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  • 51. Baptista, Marisa A. P.
    et al.
    Keszei, Marton
    Oliveira, Mariana
    Sunahara, Karen K. S.
    Andersson, John
    Dahlberg, Carin I. M.
    Worth, Austen J.
    Lieden, Agne
    Kuo, I-Chun
    Wallin, Robert P. A.
    Snapper, Scott B.
    Eidsmo, Liv
    Scheynius, Annika
    Karlsson, Mikael C. I.
    Bouma, Gerben
    Burns, Siobhan O.
    Forsell, Mattias N. E.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Immunology/Immunchemistry.
    Thrasher, Adrian J.
    Nylén, Susanne
    Westerberg, Lisa S.
    Deletion of Wiskott-Aldrich syndrome protein triggers Rac2 activity and increased cross-presentation by dendritic cells2016In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, article id 12175Article in journal (Refereed)
    Abstract [en]

    Wiskott-Aldrich syndrome (WAS) is caused by loss-of-function mutations in the WASp gene. Decreased cellular responses in WASp-deficient cells have been interpreted to mean that WASp directly regulates these responses in WASp-sufficient cells. Here, we identify an exception to this concept and show that WASp-deficient dendritic cells have increased activation of Rac2 that support cross-presentation to CD8(+) T cells. Using two different skin pathology models, WASp-deficient mice show an accumulation of dendritic cells in the skin and increased expansion of IFN gamma-producing CD8(+) T cells in the draining lymph node and spleen. Specific deletion of WASp in dendritic cells leads to marked expansion of CD8(+) T cells at the expense of CD4(+) T cells. WASp-deficient dendritic cells induce increased cross-presentation to CD8(+) T cells by activating Rac2 that maintains a near neutral pH of phagosomes. Our data reveals an intricate balance between activation of WASp and Rac2 signalling pathways in dendritic cells.

  • 52. Barbus, Sebastian
    et al.
    Tews, Björn
    Karra, Daniela
    Hahn, Meinhard
    Radlwimmer, Bernhard
    Delhomme, Nicolas
    Hartmann, Christian
    Felsberg, Jörg
    Krex, Dietmar
    Schackert, Gabriele
    Martinez, Ramon
    Reifenberger, Guido
    Lichter, Peter
    Differential retinoic acid signaling in tumors of long- and short-term glioblastoma survivors.2011In: Journal of the National Cancer Institute, ISSN 0027-8874, E-ISSN 1460-2105, Vol. 103, no 7Article in journal (Refereed)
    Abstract [en]

    Although the prognosis of most glioblastoma patients is poor, 3%-5% patients show long-term survival of 36 months or longer after diagnosis. To study the differences in activation of biochemical pathways, we performed mRNA and protein expression analyses of primary glioblastoma tissues from 11 long-term survivors (LTS; overall survival ≥ 36 months) and 12 short-term survivors (STS; overall survival ≤ 6 months). The mRNA expression ratio of the retinoic acid transporters fatty acid-binding protein 5 (FABP5) and cellular retinoic acid-binding protein 2 (CRABP2), which regulate the differential delivery of retinoic acid to either antioncogenic retinoic acid receptors or prooncogenic nuclear receptor peroxisome proliferator-activated receptor delta, was statistically significantly higher in the tumor tissues of STS than those of LTS (median ratio in STS tumors = 3.64, 10th-90th percentile = 1.43-4.54 vs median ratio in LTS tumors = 1.42, 10th-90th percentile = -0.98 to 2.59; P < .001). High FABP5 protein expression in STS tumors was associated with highly proliferating tumor cells and activation of 3-phosphoinositide-dependent protein kinase-1 and v-akt murine thymoma viral oncogene homolog. The data suggest that retinoic acid signaling activates different targets in glioblastomas from LTS and STS. All statistical tests were two-sided.

  • 53.
    Barcena-Uribarri, Ivan
    et al.
    Universität Würzburg, Germany.
    Thein, Marcus
    Universität Würzburg and Jacobs University Bremen, Germany.
    Maier, Elke
    Universität Würzburg, Germany.
    Bonde, Mari
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Bergström, Sven
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Benz, Roland
    Universität Würzburg, Germany.
    Use of Nonelectrolytes Reveals the Channel Size and Oligomeric Constitution of the Borrelia burgdorferi P66 Porin2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 11, p. e78272-Article in journal (Refereed)
    Abstract [en]

    In the Lyme disease spirochete Borrelia burgdorferi, the outer membrane protein P66 is capable of pore formation with an atypical high single-channel conductance of 11 nS in 1 M KCl, which suggested that it could have a larger diameter than 'normal' Gram-negative bacterial porins. We studied the diameter of the P66 channel by analyzing its single-channel conductance in black lipid bilayers in the presence of different nonelectrolytes with known hydrodynamic radii. We calculated the filling of the channel with these nonelectrolytes and the results suggested that nonelectrolytes (NEs) with hydrodynamic radii of 0.34 nm or smaller pass through the pore, whereas neutral molecules with greater radii only partially filled the channel or were not able to enter it at all. The diameter of the entrance of the P66 channel was determined to be <= 1.9 nm and the channel has a central constriction of about 0.8 nm. The size of the channel appeared to be symmetrical as judged from one-sidedness of addition of NEs. Furthermore, the P66-induced membrane conductance could be blocked by 80-90% by the addition of the nonelectrolytes PEG 400, PEG 600 and maltohexaose to the aqueous phase in the low millimolar range. The analysis of the power density spectra of ion current through P66 after blockage with these NEs revealed no chemical reaction responsible for channel block. Interestingly, the blockage of the single-channel conductance of P66 by these NEs occurred in about eight subconductance states, indicating that the P66 channel could be an oligomer of about eight individual channels. The organization of P66 as a possible octamer was confirmed by Blue Native PAGE and immunoblot analysis, which both demonstrated that P66 forms a complex with a mass of approximately 460 kDa. Two dimension SDS PAGE revealed that P66 is the only polypeptide in the complex.

  • 54. Barfeld, Stefan J
    et al.
    Fazli, Ladan
    Persson, Margareta
    Marjavaara, Lisette
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics. Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Urbanucci, Alfonso
    Kaukoniemi, Kirsi M
    Rennie, Paul S
    Ceder, Yvonne
    Chabes, Andrei
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics. Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Visakorpi, Tapio
    Mills, Ian G
    Myc-dependent purine biosynthesis affects nucleolar stress and therapy response in prostate cancer2015In: OncoTarget, ISSN 1949-2553, E-ISSN 1949-2553, Vol. 6, no 14, p. 12587-12602Article in journal (Refereed)
    Abstract [en]

    The androgen receptor is a key transcription factor contributing to the development of all stages of prostate cancer (PCa). In addition, other transcription factors have been associated with poor prognosis in PCa, amongst which c-Myc (MYC) is a well-established oncogene in many other cancers. We have previously reported that the AR promotes glycolysis and anabolic metabolism; many of these metabolic pathways are also MYC-regulated in other cancers. In this study, we report that in PCa cells de novo purine biosynthesis and the subsequent conversion to XMP is tightly regulated by MYC and independent of AR activity. We characterized two enzymes, PAICS and IMPDH2, within the pathway as PCa biomarkers in tissue samples and report increased efficacy of established anti-androgens in combination with a clinically approved IMPDH inhibitor, mycophenolic acid (MPA). Treatment with MPA led to a significant reduction in cellular guanosine triphosphate (GTP) levels accompanied by nucleolar stress and p53 stabilization. In conclusion, targeting purine biosynthesis provides an opportunity to perturb PCa metabolism and enhance tumour suppressive stress responses.

  • 55.
    Baudin, Maria
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Virology.
    Hossain, Delowar
    Evander, Magnus
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Virology.
    Importance of charge interactions in Rift Valley fever virus attachment to host cellsManuscript (preprint) (Other academic)
    Abstract [en]

    The mosquito-borne Rift Valley fever virus (RVFV) cause disease in both humans and animals and can infect a large range of animals as well as humans. Many different cell types are infected both in vivo and in vitro. To enter a cell the virus needs to attach and enter, and this initial binding to the host cell surface could depend on both general mechanisms, and different specific receptors. Our aim was to characterize determinants for RVFV entry into its host cells.To examine RVFV attachment to host cells we based our experimental assay on RVF virus-like particles containing a reporter gene. The enveloped RVFV uses protruding glycoproteins (Gn and Gc) for attachment and entry and to investigate potential virus-cell surface interactions, the net surface charge of the glycoproteins was first calculated. The RVFV glycoprotein Gn had a predicted isoelectric point (pI) of 7.6 and a net positive charge of +6.9 at pH 7.0, suggesting a charge interaction between the Gn ectodomain and the negatively charged cell surface. RVFV Gc on the other hand, was highly negatively charged, -12.8 at neutral pH, most probably reflecting that Gc is not exposed until after receptor binding. To characterize the general conditions needed for RVFV attachment, cells or virus were treated with various compounds. Both sodium chloride and the negatively charged heparin inhibited RVF virus-like particle infection, strongly indicating that viral binding was charge-dependent. Treatment with sodium periodate pointed to a carbohydrate structure as a cellular interaction partner. Removal of sialic acid or heparan sulfate receptors on the cell surface by enzymatic treatment and blocking of the heparan sulfate receptor did not inhibit virus attachment.In conclusion, RVFV binding to host cells was charge dependent and the results point to a carbohydrate structure with negative charge as a potential attachment factor.

  • 56. Baumann, Anne
    et al.
    Jorge-Finnigan, Ana
    Jung-KC, Kunwar
    Sauter, Alexander
    Horvath, Istvan
    Morozova-Roche, Ludmilla A.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Martinez, Aurora
    Tyrosine Hydroxylase Binding to Phospholipid Membranes Prompts Its Amyloid Aggregation and Compromises Bilayer Integrity2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 39488Article in journal (Refereed)
    Abstract [en]

    Tyrosine hydroxylase (TH), a rate-limiting enzyme in the synthesis of catecholamine neurotransmitters and hormones, binds to negatively charged phospholipid membranes. Binding to both large and giant unilamellar vesicles causes membrane permeabilization, as observed by efflux and influx of fluorescence dyes. Whereas the initial protein-membrane interaction involves the N-terminal tail that constitutes an extension of the regulatory ACT-domain, prolonged membrane binding induces misfolding and self-oligomerization of TH over time as shown by circular dichroism and Thioflavin T fluorescence. The gradual amyloid-like aggregation likely occurs through cross-beta interactions involving aggregation-prone motives in the catalytic domains, consistent with the formation of chain and ring-like protofilaments observed by atomic force microscopy in monolayer-bound TH. PC12 cells treated with the neurotoxin 6-hydroxydopamine displayed increased TH levels in the mitochondrial fraction, while incubation of isolated mitochondria with TH led to a decrease in the mitochondrial membrane potential. Furthermore, cell-substrate impedance and viability assays showed that supplementing the culture media with TH compromises cell viability over time. Our results revealed that the disruptive effect of TH on cell membranes may be a cytotoxic and pathogenic factor if the regulation and intracellular stability of TH is compromised.

  • 57.
    Beier, Frank
    et al.
    Institute for Experimental Medicine, University of Erlangen-Nürnberg, Erlangen, Germany.
    Eerola, Iiro
    Department of Medical Biochemistry and Molecular Biology, University of Turku, Turku, Finland.
    Vuorio, Eero
    Department of Medical Biochemistry and Molecular Biology, University of Turku, Turku, Finland.
    Luvalle, Phyllis
    Department of Medical Biochemistry, University of Calgary, Calgary, Alberta, Canada.
    Reichenberger, Ernest
    Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA.
    Bertling, Wolf
    Institute for Genetics, University of Bayreuth, Bayreuth, Germany.
    von der Mark, Klaus
    Institute for Experimental Medicine, University of Erlangen-Nürnberg, Erlangen, Germany.
    Lammi, Mikko
    Variability in the upstream promoter and intron sequences of the human, mouse and chick type X collagen genes.1996In: Matrix Biology, ISSN 0945-053X, E-ISSN 1569-1802, Vol. 15, no 6, p. 415-422, article id 9049979Article in journal (Refereed)
    Abstract [en]

    The type X collagen gene is specifically expressed in hypertrophic chondrocytes during endochondral ossification. Transcription of the type X collagen gene by these differentiated cells is turned on at the same time as transcription of several other cartilage specific genes is switched off and before mineralization of the matrix begins. Analysis of type X collagen promoters for regulatory regions in different cell culture systems and in transgenic mice has given contradictory results suggesting major differences among species. To approach this problem, we have determined the nucleotide sequences of the two introns and upstream promoter sequences of the human and mouse type X collagen genes and compared them with those of bovine and chick. Within the promoter regions, we found three boxes of homology which are nearly continuous in the human gene but have interruptions in the murine gene. One of these interruptions was identified as a complex 1.9 kb repetitive element with homology to LINE, B1, B2 and long terminal repeat sequences. Regulatory elements of the human type X collagen gene are located upstream of the region where the repetitive element is inserted in the mouse gene, making it likely that the repetitive element is inserted between the coding region and regulatory sequences of the murine gene without interfering with its expression pattern. We also compared the sequences of the introns of both genes and found strong conservation. Comparisons of the mammalian sequences with promoter and first intron sequences of the chicken type X collagen gene revealed that only the proximal 120 nucleotides of the promoter were conserved, whereas all other sequences displayed no obvious homology to the murine and human sequences.

  • 58.
    Beier, Frank
    et al.
    Institute Experimental Medicine, University of Erlangen-Nürnberg, Erlangen, Germany.
    Lammi, Mikko
    Institute Experimental Medicine, University of Erlangen-Nürnberg, Erlangen, Germany.
    Bertling, Wolf
    Institute for Genetics, University of Bayreuth, Bayreuth, Germany.
    von der Mark, Klaus
    Institute Experimental Medicine, University of Erlangen-Nürnberg, Erlangen, Germany.
    Transcriptional regulation of the human type X collagen gene expression.1996In: Annals of the New York Academy of Sciences, ISSN 0077-8923, E-ISSN 1749-6632, Vol. 785, p. 209-211, article id 8702131Article in journal (Refereed)
  • 59.
    Beier, Frank
    et al.
    Institut für Experimentelle Medizin, Universität Erlangen-Nürnberg, Erlangen, Germany; Department of Medical Biochemistry, University of Calgary, Calgary, Canada.
    Vornehm, Silvia
    Institut für Experimentelle Medizin, Universität Erlangen-Nürnberg, Erlangen, Germany.
    Pöschl, Ernst
    Institut für Experimentelle Medizin, Universität Erlangen-Nürnberg, Erlangen, Germany.
    von der Mark, Klaus
    Institut für Experimentelle Medizin, Universität Erlangen-Nürnberg, Erlangen, Germany.
    Lammi, Mikko
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Localization of silencer and enhancer elements in the human type X collagen gene.1997In: Journal of Cellular Biochemistry, ISSN 0730-2312, E-ISSN 1097-4644, Vol. 66, no 2, p. 210-218, article id 9213222Article in journal (Refereed)
    Abstract [en]

    Collagen type X is a short, network-forming collagen expressed temporally and spatially tightly controlled in hypertrophic chondrocytes during endochondral ossification. Studies on chicken chondrocytes indicate that the regulation of type X collagen gene expression is regulated at the transcriptional level. In this study, we have analyzed the regulatory elements of the human type X collagen (Col10a1) by reporter gene constructs and transient transfections in chondrogenic and nonchondrogenic cells. Four different promoter fragments covering up to 2,864 bp of 5'-flanking sequences, either including or lacking the first intron, were linked to luciferase reporter gene and transfected into 3T3 fibroblasts, HT1080 fibrosarcoma cells, prehypertrophic chondrocytes from the resting zone, hypertrophic chondrocytes, and chondrogenic cell lines. The results indicated the presence of three regulatory elements in the human Col10a1 gene besides the proximal promoter. First, a negative regulatory element located between 2.4 and 2.8 kb upstream of the transcription initiation site was active in all nonchondrogenic cells and in prehypertrophic chondrocytes. Second, a positive, but also non-tissue-specific positive regulatory element was present in the first intron. Third, a cell-type-specific enhancer element active only in hypertrophic chondrocytes was located between -2.4 and -0.9 kb confirming a previous report by Thomas et al. [(1995): Gene 160:291-296]. The enhancing effect, however, was observed only when calcium phosphate was either used for transfection or included in the culture medium after lipofection. These findings demonstrate that the rigid control of human Col10a1 gene expression is achieved by both positive and negative regulatory elements in the gene and provide the basis for the identification of factors binding to those elements.

  • 60. Beljantseva, Jelena
    et al.
    Kudrin, Pavel
    Jimmy, Steffi
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Ehn, Marcel
    Pohl, Radek
    Varik, Vallo
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). 1University of Tartu, Institute of Technology, Tartu, Estonia.
    Tozawa, Yuzuru
    Shingler, Victoria
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Tenson, Tanel
    Rejman, Dominik
    Hauryliuk, Vasili
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). 1University of Tartu, Institute of Technology, Tartu, Estonia.
    Molecular mutagenesis of ppGpp: turning a RelA activator into an inhibitor2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 41839Article in journal (Refereed)
    Abstract [en]

    The alarmone nucleotide (p) ppGpp is a key regulator of bacterial metabolism, growth, stress tolerance and virulence, making (p) ppGpp-mediated signaling a promising target for development of antibacterials. Although ppGpp itself is an activator of the ribosome-associated ppGpp synthetase RelA, several ppGpp mimics have been developed as RelA inhibitors. However promising, the currently available ppGpp mimics are relatively inefficient, with IC50 in the sub-mM range. In an attempt to identify a potent and specific inhibitor of RelA capable of abrogating (p) ppGpp production in live bacterial cells, we have tested a targeted nucleotide library using a biochemical test system comprised of purified Escherichia coli components. While none of the compounds fulfilled this aim, the screen has yielded several potentially useful molecular tools for biochemical and structural work.

  • 61.
    Berg, A. H.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Thomas, P.
    Olsson, P-E.
    Characterization of the 17,20β-dihydroxy-4-pregnen-3-one membrane receptor in Arctic char (Salvelinus alpinus) ovaries and its upregulation during gonadotropin induction of oocyte maturationManuscript (Other academic)
  • 62.
    Berg, A. H.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Westerlund, L.
    Olsson, P-E.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Regulation of Arctic char (Salvelinus alpinus) egg shell proteins and vitellogenin during reproduction and in response to 17β-estradiol and cortisol2004In: General and Comparative Endocrinology, ISSN 0016-6480, E-ISSN 1095-6840, Vol. 135, no 3, p. 276-285Article in journal (Refereed)
    Abstract [en]

    Estrogens induce both vitellogenin (Vtg) and egg shell (zona pellucida; ZP) protein synthesis in salmonids. However, while Vtg is strictly under estrogenic control, recent reports suggest that additional mechanisms are involved in ZP protein synthesis. During sexual maturation both estrogen and glucocorticoid levels increase in the circulation of female fish. As glucocorticoids have been shown to interfere with Vtg induction in fish we investigated whether cortisol (F) had similar effects on ZP regulation. In the present study we determined both the natural variation in Vtg and ZP during an annual reproductive cycle in female Arctic char (Salvelinus alpinus), and the effect of co-treatment of juvenile Arctic char with 17β-estradiol (E2) and F. During sexual maturation the expression of Vtg and ZP correlated to plasma levels of E2 and F. Determination of Vtg and ZP protein levels following co-treatment with E2 and F showed that F antagonized E2 induction of Vtg. However, F was observed to potentiate the expression of ZP protein in the same fish. These results indicate that in Arctic char Vtg and ZP proteins are not regulated by the same mechanisms and suggest that ZP protein expression does not necessarily imply exposure to estrogenic compounds alone, and may thus not be ideally suited as a biomarker of exposure to estrogenic compounds.

  • 63.
    Berg, Håkan
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Department of Marine Science, University of Texas Marine Science Institute, University of Texas, Port Aransas, Texas, USA.
    Olsson, Per-Erik
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Department of Natural Science, Unit of Molecular Biology, Orebro University, Orebro, Sweden.
    Modig, Carina
    17ß-estradiol induced vitellogenesis is inhibited by cortisol at the post-transcriptional level in Arctic char (Salvelinus alpinus)2004In: Reproductive Biology and Endocrinology, ISSN 1477-7827, E-ISSN 1477-7827, Vol. 2, no 62, p. 1-10Article in journal (Other academic)
    Abstract [en]

    This study was performed to investigate stress effects on the synthesis of egg yolk precursor, vitellogenin (Vtg) in Arctic char (Salvelinus alpinus). In particular the effect of cortisol (F) was determined since this stress hormone has been suggested to interfere with vitellogenesis and is upregulated during sexual maturation in teleosts. Arctic char Vtg was purified and polyclonal antibodies were produced in order to develop tools to study regulation of vitellogenesis. The Vtg antibodies were used to develop an enzyme-linked immunosorbent assay. The corresponding Vtg cDNA was cloned from a hepatic cDNA library in order to obtain DNA probes to measure Vtg mRNA expression. Analysis of plasma from juvenile Arctic char, of both sexes, exposed to different steroids showed that production of Vtg was induced in a dose dependent fashion by 17β-estradiol (E2), estrone and estriol. Apart from estrogens a high dose of F also upregulated Vtg. In addition, F, progesterone (P) and tamoxifen were tested to determine these compounds ability to modulate E2 induced Vtg synthesis at both the mRNA and protein level. Tamoxifen was found to inhibit E2 induced Vtg mRNA and protein upregulation. P did not alter the Vtg induction while F reduced the Vtg protein levels without affecting the Vtg mRNA levels. Furthermore the inhibition of Vtg protein was found to be dose dependent. Thus, the inhibitory effect of F on Vtg appears to be mediated at the post-transcriptional level.

  • 64. Berger, Susanne
    et al.
    Schäfer, Gritt
    Kesper, Dörthe A
    Holz, Anne
    Eriksson, Therese
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Palmer, Ruth H
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Beck, Lothar
    Klämbt, Christian
    Renkawitz-Pohl, Renate
    Onel, Susanne-Filiz
    WASP and SCAR have distinct roles in activating the Arp2/3 complex during myoblast fusion2008In: Journal of Cell Science, ISSN 0021-9533, E-ISSN 1477-9137, Vol. 121, no Pt 8, p. 1303-1313Article in journal (Refereed)
    Abstract [en]

    Myoblast fusion takes place in two steps in mammals and in Drosophila. First, founder cells (FCs) and fusion-competent myoblasts (FCMs) fuse to form a trinucleated precursor, which then recruits further FCMs. This process depends on the formation of the fusion-restricted myogenic-adhesive structure (FuRMAS), which contains filamentous actin (F-actin) plugs at the sites of cell contact. Fusion relies on the HEM2 (NAP1) homolog Kette, as well as Blow and WASP, a member of the Wiskott-Aldrich-syndrome protein family. Here, we show the identification and characterization of schwächling--a new Arp3-null allele. Ultrastructural analyses demonstrate that Arp3 schwächling mutants can form a fusion pore, but fail to integrate the fusing FCM. Double-mutant experiments revealed that fusion is blocked completely in Arp3 and wasp double mutants, suggesting the involvement of a further F-actin regulator. Indeed, double-mutant analyses with scar/WAVE and with the WASP-interacting partner vrp1 (sltr, wip)/WIP show that the F-actin regulator scar also controls F-actin formation during myoblast fusion. Furthermore, the synergistic phenotype observed in Arp3 wasp and in scar vrp1 double mutants suggests that WASP and SCAR have distinct roles in controlling F-actin formation. From these findings we derived a new model for actin regulation during myoblast fusion.

  • 65. Berggren, Kristina
    et al.
    Vindebro, Reine
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Bergström, Claes
    Spoerry, Christian
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Persson, Helena
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Fex, Tomas
    Kihlberg, Jan
    von Pawel-Rammingen, Ulrich
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Luthman, Kristina
    3-aminopiperidine-based peptide analogues as the first selective noncovalent inhibitors of the bacterial cysteine protease IdeS2012In: Journal of Medicinal Chemistry, ISSN 0022-2623, E-ISSN 1520-4804, Vol. 55, no 6, p. 2549-2560Article in journal (Refereed)
    Abstract [en]

    A series of eight peptides corresponding to the amino acid sequence of the hinge region of IgG and 17 newly synthesized peptide analogues containing a piperidine moiety as a replacement of a glycine residue were tested as potential inhibitors of the bacterial IgG degrading enzyme of Streptococcus pyogenes, IdeS. None of the peptides showed any inhibitory activity of IdeS, but several piperidine-based analogues were identified as inhibitors. Two different analysis methods were used: an SDS-PAGE based assay to detect IgG cleavage products and a surface plasmon resonance spectroscopy based assay to quantify the degree of inhibition. To investigate the selectivity of the inhibitors for IdeS, all compounds were screened against two other related cysteine proteases (SpeB and papain). The selectivity results show that larger analogues that are active inhibitors of IdeS are even more potent as inhibitors of papain, whereas smaller analogues that are active inhibitors of IdeS inhibit neither SpeB nor papain. Two compounds were identified that exhibit high selectivity against IdeS and will be used for further studies.

  • 66.
    Berglöf, Elisabet
    Umeå University, Faculty of Medicine, Integrative Medical Biology, Histology and Cell Biology.
    Dopamine neurons in ventral mesencephalon: interactions with glia and locus coeruleus2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Parkinson’s disease is a progressive neurodegenerative disorder, characterized by a depletion of the dopaminergic neurons in the substantia nigra. The cause of the disease is yet unknown but age, oxidative stress, and neuroinflammation are some of the features involved in the degeneration. In addition, substantial cell death of noradrenergic neurons occurs in the locus coeruleus (LC). Noradrenaline has been suggested to protect the dopamine neurons from oxidative stress and neuroinflammation. The main treatment of Parkinson’s disease is Levo-dopa, although severe side effects arise from this therapy. Hence, grafting fetal ventral mesencephalic (VM) tissue into the adult striatum has been evaluated as an alternative treatment for Parkinsons’s disease. However, the survival of the grafted neurons is limited, and the dopamine-denervated striatum does not become fully reinnervated. Therefore, elucidating factors that enhance dopamine nerve fiber formation and/or survival of the grafted neurons is of utmost importance.

    To investigate dopamine nerve fiber formation and the interactions with glial cells, organotypic VM tissue cultures were utilized. Two morphologically different nerve fiber outgrowths from the tissue slice were observed. Nerve fibers were initially formed in the absence of migrating astrocytes, although thin vimentin-positive astrocytic processes were detected within the same area. A second, persistent nerve fiber outgrowth was observed associated with migrating astrocytes. Hence, both of these nerve fiber outgrowths were to some extent dependent on astrocytes, and appeared as a general feature since this phenomenon was demonstrated in β-tubulin, tyrosine hydroxylase (TH), and aldehyde dehydrogenase A1 (ALDH1)-positive nerve fibers. Neither oligodendrocytes (NG2-positive cells), nor microglia (Iba-1-positive cells) exerted any effect on these two neuronal growths. Since astrocytes appeared to influence the nerve fiber formation, the role of proteoglycans, i.e. extracellular matrix molecules produced by astrocytes, was investigated. β-xyloside was added to the cultures to inhibit proteoglycan synthesis. The results revealed a hampered astrocytic migration and proliferation, as well as a reduction of the glia-associated TH-positive nerve fiber outgrowth. Interestingly, the number of cultures displaying the non-glia-mediated TH-positive nerve fibers increased after β-xyloside treatment, although the amount of TH-protein was not altered. Thus, proteoglycans produced by astrocytes appeared to be important in affecting the dopamine nerve fiber formation.

    The noradrenaline neurons in LC have been suggested to protect dopamine neurons from damage. Therefore, the interaction between VM and LC was evaluated. Using the intraocular grafting method, fetal VM and LC were grafted either as single grafts or as VM+LC co-grafts. Additionally, the recipient animals received 2% blueberry-enriched diet. The direct contact of LC promoted graft volume and survival of TH-positive neurons in the VM grafts. The number of dopamine neurons, derived preferably from the A9 (ALDH1/TH-positive) was increased, whereas the dopamine neurons from the A10 (calbindin/TH-positive) were not affected. A dense dopamine-β-hydroxylase (DBH)-positive innervation was correlated to the improved survival. Blueberry-enriched diet enhanced the number of TH-positive neurons in VM, although the graft size was not altered. The combination of blueberries and the presence of LC did not yield additive effects on the survival of VM grafts. The attachment of VM or the addition of blueberries did not affect the survival of TH-positive neurons in LC grafts. The number of Iba-1-positive microglia was decreased in co-grafted VM compared to single VM transplants. The addition of blueberries reduced the number of Iba-1-positive microglia in single VM transplants. Hence, the direct contact of LC or the addition of blueberries enhanced the survival of VM grafts.

    Taken together, these data demonstrate novel findings regarding the importance of astrocytes for the nerve fiber formation of dopamine neurons. Further, both the direct attachment of LC or antioxidant-enriched diet promote the survival of fetal VM grafts, while LC is not affected.

  • 67.
    Bergman, Marie-Louise
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    A sub-phenotype approach to dissect the genetic control of murine type 1 diabetes2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The non-obese diabetic (NOD) mouse is a model for human type 1 diabetes (T1D). The disease in the NOD mouse is polygenic and multifactorial and so far at least 20 insulin dependent diabetes (Idd) susceptibility loci have been identified. However, no etiological mutations have been definitely ascribed to the Idd loci. To identify potential etiological mutations, a sub-phenotype approach was undertaken, consisting of the establishment and genetic mapping of immuno-related sub-phenotypes that may contribute to the pathogenesis of T1D in the NOD mouse model. This thesis presents (1) the results of the identification and genetic mapping of four novel NOD immuno-phenotypes to individual Idd loci, and (2) confirmation of these results by the generation and analysis of congenic strains covering those Idd regions.

    Evidence is provided that gene(s) within the Idd5 region control cyclophosphamide (CY)-induced apoptosis in peripheral lymphocytes and y-irradiation induced apoptosis in NOD thymocytes. Analysis of non-obese resistant (NOR) and NOD-Idd5 congenic mice reveal that CY-induced apoptosis in peripheral lymphocytes and y-irradiation induced apoptosis in thymocytes are controlled by a 20cM and a 6cM region, respectively, both containing the Idd5 region and including the immuno-regulatory Ctla4 gene. Additionally, CTLA4 is shown to be defectively up-regulated in activated NOD peripheral lymphocytes, and CTLA4-deficient mice show similar defects in T cell apoptosis induction. Taken together, these results suggest that a defective up-regulation of CTLA4 mediates apoptosis resistance, contributing to diabetes pathogenesis.

    Moreover, it is shown that gene(s) within the Idd6 region control low proliferation ofNOD immature thymocytes and resistance to dexamethazone-induced apoptosis in immature DP thymocytes. The decrease of diabetes incidence and the restoration of the apoptosis resistance phenotype in reciprocal Idd6 congenic strains further restrict the chromosomal region controlling the Idd6 locus as well as the locus controlling the apoptosis resistance phenotype. In fact, analysis of NOD-Idd6 congenic mice reveal that Dxm-induced apoptosis in thymocytes is controlled by the distal 3cM region of the Idd6 locus. As the thymic selection process is highly dependent on both proliferation and apoptosis, the hypothesis is raised that the Idd6 locus contributes to the pathogenesis of diabetes by altering thymic selection, resulting in an autoimmune prone peripheral T cell repertoire.

  • 68. Bernardo-Garcia, Noelia
    et al.
    Sánchez-Murcia, Pedro A.
    Espaillat, Akbar
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Martínez-Caballero, Siseth
    Cava, Felipe
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Hermoso, Juan A.
    Gago, Federico
    Cold-induced aldimine bond cleavage by Tris in Bacillus subtilis alanine racemase2019In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 17, no 17, p. 4350-4358Article in journal (Refereed)
    Abstract [en]

    Pyridoxal 5'-phosphate (PLP) is a versatile cofactor involved in a large variety of enzymatic processes. Most of PLP-catalysed reactions, such as those of alanine racemases (AlaRs), present a common resting state in which the PLP is covalently bound to an active-site lysine to form an internal aldimine. The crystal structure of BsAlaR grown in the presence of Tris lacks this covalent linkage and the PLP cofactor appears deformylated. However, loss of activity in a Tris buffer only occurred after the solution was frozen prior to carrying out the enzymatic assay. This evidence strongly suggests that Tris can access the active site at subzero temperatures and behave as an alternate racemase substrate leading to mechanism-based enzyme inactivation, a hypothesis that is supported by additional X-ray structures and theoretical results from QM/ MM calculations. Taken together, our findings highlight a possibly underappreciated role for a common buffer component widely used in biochemical and biophysical experiments.

  • 69. Berry, Teeara
    et al.
    Luther, William
    Bhatnagar, Namrata
    Jamin, Yann
    Poon, Evon
    Sanda, Takaomi
    Pei, Desheng
    Sharma, Bandana
    Vetharoy, Winston R
    Hallsworth, Albert
    Ahmad, Zai
    Barker, Karen
    Moreau, Lisa
    Webber, Hannah
    Wang, Wenchao
    Liu, Qingsong
    Perez-Atayde, Antonio
    Rodig, Scott
    Cheung, Nai-Kong
    Raynaud, Florence
    Hallberg, Bengt
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Robinson, Simon P
    Gray, Nathanael S
    Pearson, Andrew DJ
    Eccles, Suzanne A
    Chesler, Louis
    George, Rani E
    The ALK(F1174L) mutation potentiates the oncogenic activity of MYCN in neuroblastoma2012In: Cancer Cell, ISSN 1535-6108, E-ISSN 1878-3686, Vol. 22, no 1, p. 117-130Article in journal (Refereed)
    Abstract [en]

    The ALK(F1174L) mutation is associated with intrinsic and acquired resistance to crizotinib and cosegregates with MYCN in neuroblastoma. In this study, we generated a mouse model overexpressing ALK(F1174L) in the neural crest. Compared to ALKF1174L and MYCN alone, co-expression of these two oncogenes led to the development of neuroblastomas with earlier onset, higher penetrance, and enhanced lethality. ALK(F1174L)/MYCN tumors exhibited increased MYCN dosage due to ALK(F1174L)-induced activation of the PI3K/AKT/mTOR and MAPK pathways, coupled with suppression of MYCN pro-apoptotic effects. Combined treatment with the ATP-competitive mTOR inhibitor Torin2 overcame the resistance of ALK(F1174L)/MYCN tumors to crizotinib. Our findings demonstrate a pathogenic role for ALK(F1174L) in neuroblastomas overexpressing MYCN and suggest a strategy for improving targeted therapy for ALK-positive neuroblastoma.

  • 70.
    Billing, Ola
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
    Insulin secretion and ASNA-1-dependent function of the endoplasmic reticulum in C. elegans2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    ASNA1 is a well-conserved ATPase involved in a wide range of functions, including cisplatin resistance, growth control, insulin secretion and targeting of tail-anchored (TA) proteins to membranes. It is a positive regulator of insulin secretion both in the roundworm Caenorhabditis elegans and in humans. Insulin secretion and downstream insulin/IGF signalling (IIS) stands at the heart of many human pathologies, such as diabetes, Alzheimer’s disease and cancer. A better understanding of IIS may therefore prove vital for treatment and cure of these diseases. This thesis aims to further investigate the function of asna-1, and to identify new regulators of IIS based on the asna-1 phenotype in C. elegans.

    Worms lacking ASNA-1 arrest growth in the first larval stage, L1, with reduced insulin secretion. The L1 arrest represents the strongest of the IIS phenotypes in worms. Most regulators of the insulin pathway have been identified in screens for other IIS phenotypes, influencing lifespan or the dauer diapause. Therefore, new regulators could be found by screening for genes which, when inactivated, cause an asna-1-like L1 arrest. Using bioinformatic approaches, a set of 143 putative asna-1 interactors were identified, based on their predicted or confirmed interaction with asna-1 in various organisms. Depletion of the Golgi SNARE homologue YKT-6 or the mitochondrial translocase homologue TOMM-40 caused asna-1-like larval arrests. Using several criteria, including genetic suppression by daf-16/Foxo, it was established that YKT-6 and TOMM-40 are positive regulators of IIS. Both proteins were also required for normal DAF-28/insulin secretion.

    Further investigation of TOMM-40 identified it as a ubiquitously expressed mitochondrial translocase in C. elegans: It localized to mitochondrial membranes and was required for importing a tagged mitochondrial reporter across mitochondrial membranes. Depletion of TOMM-40 caused a collapse of the proton gradient across the inner mitochondrial membrane and triggered the mitochondrial unfolded protein response (UPR). Worms with defective mitochondria failed to grow normally in presence of food, but this growth defect was suppressed by daf-16(mgDf50). In addition, tomm-40(RNAi) led to DAF-16/FOXO activation, an effect that was suppressed by over expression of DAF-28/insulin. Taken together, these findings support a model whereby signals of food availability are conveyed through respiring mitochondria to promote DAF-28/insulin secretion, which in turn promotes growth.

    Biochemical studies have identified ASNA-1 as a chaperone that targets a subset of newly synthesized TA proteins to a receptor at the endoplasmic reticulum (ER) membrane. However, these findings have not been tested in vivo in a metazoan model. A reporter-based system to analyse TA protein targeting into the ER in live animals using confocal microscopy was set up. A model asna-1-dependent TA protein, Y38F2AR.9/SEC-61β, required functional ASNA-1 for correct targeting to the ER. Conversely, a model asna-1-independent TA protein, CYTB5.1/cytochrome B5, did not. This phenotype was shared with the predicted asna-1 receptor homologue, wrb-1. Consistently, WRB-1 was found to localize to the ER. However, other wrb-1 mutant phenotypes only partially overlap with those of asna-1 mutants, suggesting that ASNA-1 is either partially independent of WRB-1 for TA protein targeting or that ASNA-1 has additional functions besides its role in TA protein targeting.

    Confocal microscopy also indicated that the ER morphology was aberrant in asna-1 and wrb-1 mutants. ER UPR was elevated in the asna-1 mutants, as indicated by the upregulation of an hsp-4/BiP reporter. Transmission and immuno-electron microscopy of these mutants revealed a swollen ER lumen, which is another hallmark of ER stress. High levels of autophagy in asna-1 animals and the presence of ER-containing autophagosomes in both asna-1 and wrb-1 mutants indicated a stress-induced remodelling of the ER membrane in these two mutants. In addition, both mutants had normal mitochondrial morphology, but showed severe effects on Golgi compartment morphology. Hypothetically, all these phenotypes could be due to defects in the signal recognition particle (SRP) pathway. This is because Y38F2AR.9/SEC-61β is both a TA protein and a component of the SEC-61 translocon. However, both Golgi and ER morphology was normal in Y38F2AR.9/sec-61β(tm1986) mutant animals, suggesting that the organellar defects seen in asna-1 and wrb-1 were due to a TA protein-dependent mechanism rather than an SRP-dependent mechanism. In addition, asna-1 mutants displayed numerous protein aggregates, consistent with a proposed role for ASNA-1 in shielding aggregation-prone TA protein membrane anchors from the hydrophilic environment of the cytosol.

    In conclusion, YKT-6 and TOMM-40 are positive regulators of IIS and DAF-28/insulin secretion, implicating roles for Golgi and mitochondria in IIS. DAF-28 is a metabolically regulated insulin in C. elegans, since its secretion depends on active mitochondria. Mutants for asna-1 and its predicted receptor wrb-1 show severe defects in ER and Golgi morphology. These defects may occur because TA protein targeting in asna-1 and wrb-1 mutants is defective, which is also demonstrated here in the first analysis of this process in live animals.

  • 71.
    Billing, Ola
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
    Kao, Gautam
    Naredi, Peter
    ASNA-1 acts independently of its endoplasmic reticulum receptor WRB-1 to promote insulin/IGF signallingManuscript (preprint) (Other academic)
  • 72.
    Birve, A
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Chen, S.
    Rasmuson-Lestander, Å.
    Expression pattern of the Drosophila polycomb group gene Suppressor of zeste 12Manuscript (Other academic)
  • 73. Björnberg, O
    et al.
    Vodnala, Munender
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Domkin, Vladimir
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Hofer, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Rasmussen, A
    Andersen, G
    Piskur, J
    Ribosylurea accumulates in yeast urc4 mutants2010In: Nucleosides, Nucleotides & Nucleic Acids, ISSN 1525-7770, E-ISSN 1532-2335, Vol. 29, no 4-6, p. 433-437Article in journal (Refereed)
    Abstract [en]

    Yeast Saccharomyces (Lachancea) kluyveri urc4 mutants, unable to grow on uracil, biotransformed (14)C(2)-uracil into two labeled compounds, as detected by high performance liquid chromatography (HPLC). These two compounds could also be obtained following organic synthesis of ribosylurea. This finding demonstrates that in the URC pyrimidine degradation pathway, the opening of the uracil ring takes place when uracil is attached to the ribose moiety. Ribosylurea has not been reported in the cell metabolism before and the two observed compounds likely represent an equilibrium mixture of the pyranosyl and furanosyl forms.

  • 74.
    Blomberg, Jeanette
    Umeå University, Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Regulation of apoptosis during treatment and resistance development in tumour cells2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Induction of apoptosis is the most studied cell death process and it is a tightly regulated physiological event that enables elimination of damaged and unwanted cells. Apoptosis can be induced via activation of either the intrinsic or the extrinsic signalling pathway. The intrinsic pathway involves activation of the mitochondria by stress stimuli, whereas the extrinsic pathway is triggered by ligand induced activation of death receptors such as Fas. Apoptosis induction via Fas activation plays an important role in the function of cytotoxic T lymphocytes and in the control of immune cell homeostasis.

    Several studies have shown that anticancer therapies require functional cell death signalling pathways. Irradiation based therapy has been successful in treatment of several malignancies but the usage of high doses has been associated with side effects. Therefore, low dose therapies, that either is optimized for specific delivery or administrated in combination with other treatments, are promising modalities. However, in order to achieve high-quality effects of such treatments, the death effector mechanisms involved in tumour eradication needs to be further explored. Importantly, tumour cells frequently acquire resistance to apoptosis, which consequently allows tumour cells to escape from elimination by the immune system and/or treatment.

    Interferons constitute a large family of pleotrophic cytokines that are important for the immune response against viruses and other microorganisms. The interferon signalling pathway mediates transcriptional regulation of hundreds of genes, which result in mRNA degradation, decreased protein synthesis, cell cycle inhibition and induction of apoptosis. Interferon has successfully been used in therapy against some tumours. However, several drawbacks have been reported, such as reduced sensitivity to interferon during treatment.

    The aim of this thesis was to elucidate mechanisms that mediate resistance to death receptor or interferon induced apoptosis in human tumour cell models, as well as investigate what molecular events that underlie cell death following radiation therapy of tumour cells.

    In order to elucidate mechanisms involved in acquired resistance to Fas- or interferon-induced apoptosis, a Fas- and interferon-sensitive human cell line, U937, was subjected to conditions where resistance to either Fas- or interferon induced apoptosis was acquired. Characterization of the Fas resistant cells showed that multiple resistant mechanisms had been acquired. Reduced Fas expression and increased cFLIP expression, which is an inhibitor of death receptor signalling, were two important changes found. To further examine the importance of these two alterations, clones from the Fas resistant population were established. The reduced Fas expression was determined to account for the resistant phenotype in approximately 70% of the clones. In the Fas resistant clones with normal Fas expression, the importance of an increased amount of the cFLIP protein was confirmed with shRNA interference. A cross-resistance to death receptor induced apoptosis was detected in the interferon resistant variant, which illustrates that a connection between death receptor and interferon induced apoptosis exists. Notably, interferon resistant cells also contained increased cFLIP expression, which were determined to mediate resistance to both interferon and death receptor mediated apoptosis. Finally, when cell death induced by irradiation treatment was investigated in HeLa Hep2 cells we could demonstrate that cell death was mediated by centrosome hyperamplification and mitotic aberrations, which forced the cells into mitotic catastrophes and delayed apoptosis.

    In conclusion, we have described model systems where selection for resistance to Fas or interferon induced apoptosis generated a heterogeneous population, where several signalling molecules were altered. Furthermore, we have shown that a complex cell death network was activated by irradiation based therapy.

  • 75.
    Blomberg, Jeanette
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Höglund, Andreas
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Eriksson, David
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Immunology/Immunchemistry.
    Ruuth, Kristina
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Jacobsson, Maria
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Nilsson, Jonas
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Lundgren, Erik
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Inhibition of cellular FLICE-like inhibitory protein abolishes insensitivity to interferon-α in a resistant variant of the human U937 cell line2011In: Apoptosis (London), ISSN 1360-8185, E-ISSN 1573-675X, Vol. 16, no 8, p. 783-794Article in journal (Refereed)
    Abstract [en]

    Type I interferons constitute a family of pleiotropic cytokines that have a key role in both adaptive and innate immunity. The interferon signalling pathways mediate transcriptional regulation of hundreds of genes, which result in mRNA degradation, decreased protein synthesis, cell cycle inhibition and induction of apoptosis. To elucidate regulatory networks important for interferon induced cell death, we generated interferon resistant U937 cells by selection in progressively increasing concentrations of interferon-α (IFN-α). The results show that IFN-α activates the death receptor signalling pathway and that IFN resistance was associated with cross-resistance to several death receptor ligands in a manner similar to previously described Fas resistant U937 cell lines. Increased expression of the long splice variant of the cellular FLICE-like inhibitor protein (cFLIP-L) was associated with the resistance to death receptor and IFN-α stimulation. Accordingly, inhibition of cFLIP-L expression with cycloheximide or through cFLIP short harpin RNA interference restored sensitivity to Fas and/or IFN-α. Thus, we now show that selection for interferon resistance can generate cells with increased expression of cFLIP, which protects the cells from both IFN-α and death receptor mediated apoptosis.

  • 76.
    Blomberg, Jeanette
    et al.
    Umeå University, Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Ruuth, Kristina
    Umeå University, Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Jacobsson, Maria
    Umeå University, Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Höglund, Andreas
    Umeå University, Faculty of Science and Technology, Molecular Biology (Faculty of Science and Technology).
    Nilsson, Jonas A
    Umeå University, Faculty of Science and Technology, Molecular Biology (Faculty of Science and Technology).
    Lundgren, Erik
    Umeå University, Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Reduced FAS transcription in clones of U937 cells that have acquired resistance to Fas-induced apoptosis2009In: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 276, no 2, p. 497-508Article in journal (Refereed)
    Abstract [en]

    Susceptibility to cell death is a prerequisite for the elimination of tumour cells by cytotoxic immune cells, chemotherapy or irradiation. Activation of the death receptor Fas is critical for the regulation of immune cell homeostasis and efficient killing of tumour cells by apoptosis. To define the molecular changes that occur during selection for insensitivity to Fas-induced apoptosis, a resistant variant of the U937 cell line was established. Individual resistant clones were isolated and characterized. The most frequently observed defect in the resistant cells was reduced Fas expression, which correlated with decreased FAS transcription. Clones with such reduced Fas expression also displayed partial cross-resistance to tumour necrosis factor-alpha stimulation, but the mRNA expression of tumour necrosis factor receptors was not decreased. Reintroduction of Fas conferred susceptibility to Fas but not to tumour necrosis factor-alpha stimulation, suggesting that several alterations could be present in the clones. The reduced Fas expression could not be explained by mutations in the FAS coding sequence or promoter region, or by silencing through methylations. Protein kinase B and extracellular signal-regulated kinase, components of signalling pathways downstream of Ras, were shown to be activated in some of the resistant clones, but none of the three RAS genes was mutated, and experiments using chemical inhibitors could not establish that the activation of these proteins was the cause of Fas resistance as described in other systems. Taken together, the data illustrate that Fas resistance can be caused by reduced Fas expression, which is a result of an unidentified mode of regulation.

  • 77. Boehme, Katja
    et al.
    Steinmann, Rebekka
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Kortmann, Jens
    Seekircher, Stephanie
    Heroven, Ann Kathrin
    Berger, Evelin
    Pisano, Fabio
    Thiermann, Tanja
    Wolf-Watz, Hans
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Narberhaus, Franz
    Dersch, Petra
    Concerted Actions of a Thermo-labile Regulator and a Unique Intergenic RNA Thermosensor Control Yersinia Virulence2012In: PLOS PATHOGENS, ISSN 1553-7366, Vol. 8, no 2, p. e1002518-Article in journal (Refereed)
    Abstract [en]

    Expression of all Yersinia pathogenicity factors encoded on the virulence plasmid, including the yop effector and the ysc type III secretion genes, is controlled by the transcriptional activator LcrF in response to temperature. Here, we show that a protein-and RNA-dependent hierarchy of thermosensors induce LcrF synthesis at body temperature. Thermally regulated transcription of lcrF is modest and mediated by the thermo-sensitive modulator YmoA, which represses transcription from a single promoter located far upstream of the yscW-lcrF operon at moderate temperatures. The transcriptional response is complemented by a second layer of temperature-control induced by a unique cis-acting RNA element located within the intergenic region of the yscW-lcrF transcript. Structure probing demonstrated that this region forms a secondary structure composed of two stemloops at 25 degrees C. The second hairpin sequesters the lcrF ribosomal binding site by a stretch of four uracils. Opening of this structure was favored at 37 degrees C and permitted ribosome binding at host body temperature. Our study further provides experimental evidence for the biological relevance of an RNA thermometer in an animal model. Following oral infections in mice, we found that two different Y. pseudotuberculosis patient isolates expressing a stabilized thermometer variant were strongly reduced in their ability to disseminate into the Peyer's patches, liver and spleen and have fully lost their lethality. Intriguingly, Yersinia strains with a destabilized version of the thermosensor were attenuated or exhibited a similar, but not a higher mortality. This illustrates that the RNA thermometer is the decisive control element providing just the appropriate amounts of LcrF protein for optimal infection efficiency.

  • 78. Boj, Sylvia F
    et al.
    Hwang, Chang-Il
    Baker, Lindsey A
    Chio, Iok In Christine
    Engle, Dannielle D
    Corbo, Vincenzo
    Jager, Myrthe
    Ponz-Sarvise, Mariano
    Tiriac, Hervé
    Spector, Mona S
    Gracanin, Ana
    Oni, Tobiloba
    Yu, Kenneth H
    van Boxtel, Ruben
    Huch, Meritxell
    Rivera, Keith D
    Wilson, John P
    Feigin, Michael E
    Öhlund, Daniel
    Handly-Santana, Abram
    Ardito-Abraham, Christine M
    Ludwig, Michael
    Elyada, Ela
    Alagesan, Brinda
    Biffi, Giulia
    Yordanov, Georgi N
    Delcuze, Bethany
    Creighton, Brianna
    Wright, Kevin
    Park, Youngkyu
    Morsink, Folkert HM
    Molenaar, I Quintus
    Borel Rinkes, Inne H
    Cuppen, Edwin
    Hao, Yuan
    Jin, Ying
    Nijman, Isaac J
    Iacobuzio-Donahue, Christine
    Leach, Steven D
    Pappin, Darryl J
    Hammell, Molly
    Klimstra, David S
    Basturk, Olca
    Hruban, Ralph H
    Offerhaus, George Johan
    Vries, Robert GJ
    Clevers, Hans
    Tuveson, David A
    Organoid models of human and mouse ductal pancreatic cancer2015In: Cell, ISSN 0092-8674, E-ISSN 1097-4172, Vol. 160, no 1-2, p. 324-338Article in journal (Refereed)
    Abstract [en]

    Pancreatic cancer is one of the most lethal malignancies due to its late diagnosis and limited response to treatment. Tractable methods to identify and interrogate pathways involved in pancreatic tumorigenesis are urgently needed. We established organoid models from normal and neoplastic murine and human pancreas tissues. Pancreatic organoids can be rapidly generated from resected tumors and biopsies, survive cryopreservation, and exhibit ductal- and disease-stage-specific characteristics. Orthotopically transplanted neoplastic organoids recapitulate the full spectrum of tumor development by forming early-grade neoplasms that progress to locally invasive and metastatic carcinomas. Due to their ability to be genetically manipulated, organoids are a platform to probe genetic cooperation. Comprehensive transcriptional and proteomic analyses of murine pancreatic organoids revealed genes and pathways altered during disease progression. The confirmation of many of these protein changes in human tissues demonstrates that organoids are a facile model system to discover characteristics of this deadly malignancy.

  • 79.
    Boldrup, Linda
    Umeå University, Faculty of Medicine, Medical Biosciences.
    p63 and potential p63 targets in squamous cell carcinoma of the head and neck2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Squamous cell carcinoma of the head and neck (SCCHN), the 6th most common cancer worldwide, has a low 5-year survival. Disease as well as treatment often causes patients severe functional and aesthetic problems. In order to improve treatment and diagnosis at earlier stages of tumour development it is important to learn more about the molecular mechanisms behind the disease. p63, an important regulator of epithelial formation, has been suggested to play a role in the development of SCCHN. Six different isoforms of p63 have been found and shown to have various functions. The aim of the studies in this thesis was to learn more about the role of p63 and proteins connected to p63 in SCCHN.

    Expression of p63, Cox-2, EGFR, beta-catenin, PP2A and p53 isoforms was mapped in tumours and normal tumour adjacent tissue from patients with SCCHN using western blot or RT-PCR. Results showed no significant difference between tumours and normal tumour adjacent tissue concerning expression of EGFR and beta-catenin. Cox-2 and PP2A showed significantly higher expression in tumours while p63 was more expressed in normal tumour adjacent tissue. However, expression of all these proteins in normal tumour adjacent tissue differed from tissue from disease-free non-smoking individuals. Smoking in itself did not affect expression of these proteins. The p53 isoforms p53, p53beta, p53gamma, ∆133p53, ∆133p53beta and ∆133p53gamma were expressed at RNA level in samples both from tumours and normal tumour adjacent tissue, though most of them at fairly low levels.

    The functional properties of the different p63 isoforms have not been fully mapped. By establishing stable cell lines over-expressing the different p63 isoforms we investigated their specific effect on tumour cells from SCCHN. Only the ∆Np63 isoforms could be stably over-expressed, whereas no clones over-expressing TAp63 could be established. Using microarray technique, cell lines stably expressing the ∆Np63 isoforms were studied and CD44, Keratins 4, 6, 14, 19 and Cox-2 were found to be regulated by p63.

    In conclusion, the present project adds new data to the field of p63 and SCCHN. For example, we have shown that clinically normal tumour adjacent tissue is altered compared to normal oral mucosa in non tumour patients, and that smoking does not change expression of p63, Cox-2, EGFR, beta-catenin or PP2A in oral mucosa. Novel p53 isoforms are expressed in SCCHN, and even though levels are very low they should not be overlooked. Furthermore, CD44, keratins 4, 6, 14, 19 and Cox-2 were identified as p63 targets in SCCHN.

  • 80.
    Boldrup, Linda
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Coates, Philip J
    Gu, Xiaolian
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Nylander, Karin
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    DeltaNp63 isoforms differentially regulate gene expression in squamous cell carcinoma: identification of Cox-2 as a novel p63 target.2009In: The Journal of pathology, ISSN 1096-9896Article in journal (Refereed)
    Abstract [en]

    The p53 homologue p63 produces six different isoforms that are important in development of epithelial tissues and squamous cell carcinoma of the head and neck (SCCHN). In SCCHN, the expression of p63 isoforms is highly complex, with over-expression of DeltaNp63 and p63beta isoforms in many tumours. To date, little is known about the functions of different DeltaNp63 isoforms and elucidating the distinctive properties of DeltaNp63 isoforms will help to clarify how they influence tumour biology. By gene expression profiling of SCCHN cells over-expressing the DeltaNp63 isoforms we identified different effects of the three isoforms, with DeltaNp63beta being more effective at gene induction than DeltaNp63alpha and DeltaNp63gamma, whereas DeltaNp63gamma was most effective at repressing gene expression. Thus, tumours expressing even low levels of DeltaNp63beta or DeltaNp63gamma may have distinct clinicopathological characteristics important for metastasis and therapeutic response. Induction of cyclooxygenase-2 (Cox-2) was shown by each isoform and data were confirmed by independent quantitative RT-PCR and western blotting. No direct binding of DeltaNp63 to the Cox-2 promoter could be seen, neither could any evidence for Cox-2 induction as a consequence of activated NF-kappaB pathway responses be found. As Cox-2 is known to inhibit radiotherapy responses in SCCHN patients, data indicate an additional mechanism through which DeltaNp63 acts to promote cell survival and influence therapeutic response of SCCHN. MIAME-compliant data have been deposited in the MIAME Express database (Accession No. E-MEXP-1842). Copyright (c) 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

  • 81.
    Boldrup, Linda
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Coates, Philip J
    Laurell, Göran
    Umeå University, Faculty of Medicine, Department of Clinical Sciences, Otorhinolaryngology.
    Nylander, Karin
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    p63 transcriptionally regulates BNC1, a Pol I and Pol II transcription factor that regulates ribosomal biogenesis and epithelial differentiation2012In: European Journal of Cancer, ISSN 0959-8049, E-ISSN 1879-0852, Vol. 48, no 9, p. 1401-1406Article in journal (Refereed)
    Abstract [en]

    The p53-family member, p63 is a transcription factor that influences cellular adhesion, motility, proliferation, survival and apoptosis, and has a major role in regulating epithelial stem cells. Expression of p63 is often dysregulated in squamous cell carcinomas of the head and neck. In this study we show that p63 induces the expression of the basal epithelial transcription factor, Basonuclin 1. Basonuclin 1 is an unusual transcription factor that interacts with a subset of promoters of genes that are transcribed by both RNA polymerase-I and -II and has roles in maintaining ribosomal biogenesis and the proliferative potential of immature epithelial cells. Chromatin immunoprecipitation and reporter assays demonstrate that Basonuclin 1 is a direct transcriptional target of p63 and we also show that up-regulation of Basonuclin 1 is a common event in squamous cell carcinomas of the head and neck. These data identify a new transcriptional programme mediated by p63 regulation of the Basonuclin 1 transcription factor in squamous cell carcinomas and provide a novel link of p63 with the regulation of ribosomal biogenesis in epithelial cancer.

  • 82.
    Bonde, Mari
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Structure and Function of the Borrelia burgdorferi Porins, P13 and P662015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Borrelia burgdorferi is an elongated and helically shaped bacterium that is the causal agent of the tick-borne illness Lyme disease. The disease manifests with initial flu-like symptoms and, in many cases, the appearance of a skin rash called erythema migrans at the site of the tick bite. If left untreated the disease might cause impairment of various organs such as the skin, heart, joints and the nervous system. The bacteria have a parasitic lifestyle and are always present within a host. Hosts are usually ticks or different animals and birds that serve as reservoirs for infection. B. burgdorferi are unable to synthesize building blocks for many vital cellular processes and are therefore highly dependent on their surroundings to obtain nutrients. Because of this, porins situated in the outer membrane, involved in nutrient uptake, are believed to be very important for B. burgdorferi. Except for a role in nutrient acquisition, porins can also have a function in binding extracellular matrix proteins, such as integrins, and have also been implicated in bacterial adaptation to new environments with variations in osmotic pressure.

    P13 and P66 are two integral outer membrane proteins in B. burgdorferi previously shown to have porin activities. In addition to its porin function, P66 also has integrin binding activity. In this thesis, oligomeric structures formed by the P13 and P66 protein complexes were studied using the Black lipid bilayer technique in combination with nonelectrolytes. Initial attempts were also made to study the structure of P13 in Nanodiscs, whereby membrane proteins can insert into artificial lipid bilayers in their native state and the structure can be analyzed by electron microscopy. In addition, the role of P13 and P66 in B. burgdorferi osmotic stress adaptation was examined and also the importance and role of the integrin-binding activity of P66 in B. burgdorferi infections in mice.

    Using Black lipid bilayer studies, the pore forming activity of P13 was shown to be much smaller than previously thought, exhibiting activity at 0.6 nS. The complex formed by P13 was approximately 300 kDa and solely composed of P13 monomers. The channel size was calculated to be roughly 1.4 nm. Initial Nanodisc experiments showed a pore size of 1.3 nm, confirming the pore size determined by Black lipid bilayer experiments. P66 form pores with a single channel conductance of 11 nS and a channel size of 1.9 nm. The porin assembles in the outer membrane into a large protein complex of 420 kDa, containing exclusively P66 monomers. The integrin-binding function of P66 was found to be important for efficient bacterial dissemination in the murine host but was not essential for B. burgdorferi infectivity. Neither P13 nor P66 had an active role in osmotic stress adaptation. Instead, two p13 paralogs were up-regulated at the transcript level in B. burgdorferi cultured under glycerol-induced osmotic stress.

  • 83.
    Bonde, Mari
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Olofsson, Annelie
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Frost, Mikaela
    Jegerschöld, Caroline
    Karolinska Institutet, Sweden.
    Bergström, Sven
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Sandblad, Linda
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Structural analysis of the B. burgdorferi integral outer membrane protein, P13, in lipid bilayer NanodiscsManuscript (preprint) (Other (popular science, discussion, etc.))
  • 84.
    Borge-Renberg, Karin
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Communicate or die: signalling in Drosophila immunity2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In general the work behind this thesis has revolved around the interesting pattern recognition gene family PGRPs (peptidoglycan recognition proteins). In particular the transmembrane PGRP-LC and to investigate its multifaceted role in the immune response of the fruit fly. As a well characterized model organism living on, and surrounded by, a multitude of microorganisms, Drosophila melanogaster serves as a great tool to gain insights about innate immunity. The two pillars of Drosophila innate immunity are the humoral and the cellular defense. Together they are very potent and can vanquish many infections, but if one of these pillars is damaged, chances are that the defense will collapse and the organism will succumb to the infection.

    The initial step in any immune response is to become aware of the pathogen. To accomplish this, innate immunity relies on recognizing common molecular building blocks necessary each group of microorganisms. One such building block is the bacterial cell wall component peptidoglycan. PGRPs are a widely spread gene family, and proteins of this family can bind peptidoglycan. We describe that there are 13 PGRP genes in Drosophila, one these codes for PGRP-LC. As it sits in the cell membrane in any of its three different splice forms, PGRP-LC can bind peptidoglycan, dimerize, and subsequently activate the imd/relish signalling pathway, and thereby trigger a vast production of antimicrobial peptides. These short peptides are the firearms of the humoral response. We identified three new inducible antimicrobial peptide genes, Diptericin B, Attacin C and Attacin D. Analyses of their sequences shed light on the evolution and relationship of these antimicrobial peptides

    The antimicrobial peptides are potent weapons, but without a functional cellular response the animal is at loss. Animals lacking blood cells are gravely compromised. It is interesting to find that PGRP-LC is involved at this end of the immune response equation as well. We have found that PGRP-LC is able to activate blood cells and increase numbers of circulating cells, in a JNK (Jun N-terminal kinase) dependent manner. Intriguingly this activation is not dependent on Relish, the NF-kB transcription factor of the Imd/Relish pathway.

    PGRP-LC activation funnels into both Imd/Relish and the JNK pathways. When PGRP-LC is lost, it appears that some basal, or background, JNK activation is lost. These effects are very mild, however the animal appears to become more sensitive to additional perturbations in this signalling pathway. This was the starting point when we started to re-evaluate Dredd, the caspase responsible for cleaving and activating Relish. Dredd also contributes to the JNK signalling pathway.

  • 85. Boussemart, Lise
    et al.
    Malka-Mahieu, Hélène
    Girault, Isabelle
    Allard, Delphine
    Hemmingsson, Oskar
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery. Inserm UMR981, F-94805 Villejuif, France.
    Tomasic, Gorana
    Thomas, Marina
    Basmadjian, Christine
    Ribeiro, Nigel
    Thuaud, Frédéric
    Mateus, Christina
    Routier, Emilie
    Kamsu-Kom, Nyam
    Agoussi, Sandrine
    Eggermont, Alexander M
    Désaubry, Laurent
    Robert, Caroline
    Vagner, Stéphan
    eIF4F is a nexus of resistance to anti-BRAF and anti-MEK cancer therapies2014In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 513, no 7516, p. 105-109Article in journal (Refereed)
    Abstract [en]

    In BRAF(V600)-mutant tumours, most mechanisms of resistance to drugs that target the BRAF and/or MEK kinases rely on reactivation of the RAS-RAF-MEK-ERK mitogen-activated protein kinase (MAPK) signal transduction pathway, on activation of the alternative, PI(3)K-AKT-mTOR, pathway (which is ERK independent) or on modulation of the caspase-dependent apoptotic cascade. All three pathways converge to regulate the formation of the eIF4F eukaryotic translation initiation complex, which binds to the 7-methylguanylate cap (m(7)G) at the 5' end of messenger RNA, thereby modulating the translation of specific mRNAs. Here we show that the persistent formation of the eIF4F complex, comprising the eIF4E cap-binding protein, the eIF4G scaffolding protein and the eIF4A RNA helicase, is associated with resistance to anti-BRAF, anti-MEK and anti-BRAF plus anti-MEK drug combinations in BRAF(V600)-mutant melanoma, colon and thyroid cancer cell lines. Resistance to treatment and maintenance of eIF4F complex formation is associated with one of three mechanisms: reactivation of MAPK signalling, persistent ERK-independent phosphorylation of the inhibitory eIF4E-binding protein 4EBP1 or increased pro-apoptotic BCL-2-modifying factor (BMF)-dependent degradation of eIF4G. The development of an in situ method to detect the eIF4E-eIF4G interactions shows that eIF4F complex formation is decreased in tumours that respond to anti-BRAF therapy and increased in resistant metastases compared to tumours before treatment. Strikingly, inhibiting the eIF4F complex, either by blocking the eIF4E-eIF4G interaction or by targeting eIF4A, synergizes with inhibiting BRAF(V600) to kill the cancer cells. eIF4F not only appears to be an indicator of both innate and acquired resistance but also is a promising therapeutic target. Combinations of drugs targeting BRAF (and/or MEK) and eIF4F may overcome most of the resistance mechanisms arising in BRAF(V600)-mutant cancers.

  • 86.
    Brockmann, Sarah J.
    et al.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Freischmidt, Axel
    Oeckl, Patrick
    Müller, Kathrin
    Ponna, Srinivas K.
    Helferich, Anika M.
    Paone, Christoph
    Reinders, Jörg
    Kojer, Kerstin
    Orth, Michael
    Jokela, Manu
    Auranen, Mari
    Udd, Bjarne
    Hermann, Andreas
    Danzer, Karin M.
    Lichtner, Peter
    Walther, Paul
    Ludolph, Albert C.
    Andersen, Peter M.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience.
    Otto, Markus
    Kursula, Petri
    Just, Steffen
    Weishaupt, Jochen H.
    CHCHD10 mutations p.R15L and p.G66V cause motoneuron disease by haploinsufficiency2018In: Human Molecular Genetics, ISSN 0964-6906, E-ISSN 1460-2083, Vol. 27, no 4, p. 706-715Article in journal (Refereed)
    Abstract [en]

    Mutations in the mitochondrially located protein CHCHD10 cause motoneuron disease by an unknown mechanism. In this study, we investigate the mutations p. R15L and p. G66V in comparison to wild-type CHCHD10 and the non-pathogenic variant p. P34S in vitro, in patient cells as well as in the vertebrate in vivo model zebrafish. We demonstrate a reduction of CHCHD10 protein levels in p. R15L and p. G66V mutant patient cells to approximately 50%. Quantitative real-time PCR revealed that expression of CHCHD10 p. R15L, but not of CHCHD10 p. G66V, is already abrogated at the mRNA level. Altered secondary structure and rapid protein degradation are observed with regard to the CHCHD10 p. G66V mutant. In contrast, no significant differences in expression, degradation rate or secondary structure of non-pathogenic CHCHD10 p. P34S are detected when compared with wild-type protein. Knockdown of CHCHD10 expression in zebrafish to about 50% causes motoneuron pathology, abnormal myofibrillar structure and motility deficits in vivo. Thus, our data show that the CHCHD10 mutations p. R15L and p. G66V cause motoneuron disease primarily based on haploinsufficiency of CHCHD10.

  • 87.
    Brohlin, Maria
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Biomedical Laboratory Science.
    Kelk, Peyman
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
    Wiberg, Mikael
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy. Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Hand Surgery.
    Kingham, Paul J.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
    Effects of a defined xeno-free medium on the growth and neurotrophic and angiogenic properties of human adult stem cells2017In: Cytotherapy, ISSN 1465-3249, E-ISSN 1477-2566, Vol. 19, no 5, p. 629-639Article in journal (Refereed)
    Abstract [en]

    Background. The growth properties and neurotrophic and angiogenic effects of human mesenchymal stromal cells (MSCs) cultured in a defined xeno-free, serum-free medium (MesenCult-XF) were investigated. Methods. Human MSCs from adipose tissue (ASCs) and bone marrow (BMSCs) were cultured in Minimum Essential Medium-alpha (alpha-MEM) containing fetal calf serum or in MesenCult-XF. Proliferation was measured over 10 passages and the colony-forming unit (CFU) assay and expression of cluster of differentiation (CD) surface markers were determined. Neurite outgrowth and angiogenic activity of the MSCs were determined. Results. At early passage, both ASCs and BMSCs showed better proliferation in MesenCult-XF compared with standard a-MEM containing serum. However, CFUs were significantly lower in MesenCult-XF. ASCs cultured in MesenCult-XF continued to expand at faster rates than cells grown in serum. BMSCs showed morphological changes at late passage in MesenCult-XF and stained positive for senescence beta-galactosidase activity. Expression levels of CD73 and CD90 were similar in both cell types under the various culture conditions but CD105 was significantly reduced at passage 10 in MesenCult-XF. In vitro stimulation of the cells enhanced the expression of brain derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF-A) and angiopoietin-1. Stimulated ASCs grown in MesenCult-XF evoked the longest neurite outgrowth in a neuron co-culture model. Stimulated BMSCs grown in MesenCult-XF produced the most extensive network of capillary-like tube structures in an in vitro angiogenesis assay. Conclusions. ASCs and BMSCs exhibit high levels of neurotrophic and angiogenic activity when grown in the defined serum free medium indicating their suitability for treatment of various neurological conditions. However, long-term expansion in MesenCult-XF might be restricted to ASCs.

  • 88. Bru, Samuel
    et al.
    Marc Martinez-Lainez, Joan
    Hernandez-Ortega, Sara
    Quandt, Eva
    Torres-Torronteras, Javier
    Marti, Ramon
    Canadell, David
    Arino, Joaquin
    Sharma, Sushma
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Jimenez, Javier
    Clotet, Josep
    Polyphosphate is involved in cell cycle progression and genomic stability in Saccharomyces cerevisiae2016In: Molecular Microbiology, ISSN 0950-382X, E-ISSN 1365-2958, Vol. 101, no 3, p. 367-380Article in journal (Refereed)
    Abstract [en]

    Polyphosphate (polyP) is a linear chain of up to hundreds of inorganic phosphate residues that is necessary for many physiological functions in all living organisms. In some bacteria, polyP supplies material to molecules such as DNA, thus playing an important role in biosynthetic processes in prokaryotes. In the present study, we set out to gain further insight into the role of polyP in eukaryotic cells. We observed that polyP amounts are cyclically regulated in Saccharomyces cerevisiae, and those mutants that cannot synthesise (vtc4 Delta) or hydrolyse polyP (ppn1 Delta, ppx1 Delta) present impaired cell cycle progression. Further analysis revealed that polyP mutants show delayed nucleotide production and increased genomic instability. Based on these findings, we concluded that polyP not only maintains intracellular phosphate concentrations in response to fluctuations in extracellular phosphate levels, but also muffles internal cyclic phosphate fluctuations, such as those produced by the sudden demand of phosphate to synthetize deoxynucleotides just before and during DNA duplication. We propose that the presence of polyP in eukaryotic cells is required for the timely and accurate duplication of DNA.

  • 89.
    Brännström, Kristoffer
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Islam, Tohidul
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Gharibyan, Anna L.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Iakovleva, Irina
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Nilsson, Lina
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Lee, Cheng Choo
    Sandblad, Linda
    Pamrén, Annelie
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    The Properties of Amyloid-β Fibrils Are Determined by their Path of Formation2018In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 430, no 13, p. 1940-1949Article in journal (Refereed)
    Abstract [en]

    Fibril formation of the amyloid-β peptide (Aβ) follows a nucleation-dependent polymerization process and is associated with Alzheimer's disease. Several different lengths of Aβ are observed in vivo, but Aβ1-40 and Aβ1-42 are the dominant forms. The fibril architectures of Aβ1-40 and Aβ1-42 differ and Aβ1-42 assemblies are generally considered more pathogenic. We show here that monomeric Aβ1-42 can be cross-templated and incorporated into the ends of Aβ1-40 fibrils, while incorporation of Aβ1-40 monomers into Aβ1-42 fibrils is very poor. We also show that via cross-templating incorporated Aβ monomers acquire the properties of the parental fibrils. The suppressed ability of Aβ1-40 to incorporate into the ends of Aβ1-42 fibrils and the capacity of Aβ1-42 monomers to adopt the properties of Aβ1-40 fibrils may thus represent two mechanisms reducing the total load of fibrils having the intrinsic, and possibly pathogenic, features of Aβ1-42 fibrils in vivo. We also show that the transfer of fibrillar properties is restricted to fibril-end templating and does not apply to cross-nucleation via the recently described path of surface-catalyzed secondary nucleation, which instead generates similar structures to those acquired via de novo primary nucleation in the absence of catalyzing seeds. Taken together these results uncover an intrinsic barrier that prevents Aβ1-40 from adopting the fibrillar properties of Aβ1-42 and exposes that the transfer of properties between amyloid-β fibrils are determined by their path of formation.

  • 90.
    Brännström, Kristoffer
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Öhman, Anders
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    von Pawel-Rammingen, Ulrich
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Brattsand, Maria
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Dermatology and Venerology.
    Characterization of SPINK9, a KLK5-specific inhibitor expressed in palmo-plantar epidermis2012In: Biological chemistry (Print), ISSN 1431-6730, E-ISSN 1437-4315, Vol. 393, no 5, p. 369-377Article in journal (Refereed)
    Abstract [en]

    SPINK9, a Kazal-type serine protease inhibitor, is almost exclusively expressed in the palmo-plantar epidermis. SPINK9 selectively inhibits kallikrein-related peptidase 5 (KLK5), no other target enzyme is known at present. In this study, we defined the reactive loop to residues 48 and 49 of SPINK9 and characterized the inhibition and binding of different SPINK9 variants towards KLK5, KLK7, KLK8 and KLK14. Substitutions of single amino acids in the reactive loop had a large impact on both inhibitory efficiency and specificity. Binding studies showed that it is mainly the dissociation rate that is affected by the amino acid substitutions. The inhibitory effect of wild-type SPINK9 was clearly pH-dependent with an improved effect at a pH similar to that of the outer layers of the skin. Modeling of the enzyme-inhibitor complexes showed that the reactive loop of SPINK9 fits very well into the deep negatively charged binding pocket of KLK5. A decrease in pH protonates His48 of the wild-type protein resulting in a positively charged residue, thereby explaining the observed decreased dissociation rate. Interestingly, substitution with a positively charged amino acid at position 48 resulted in a more efficient inhibitor at higher pH.

  • 91. Buchan, J Ross
    et al.
    Nissan, Tracy
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Parker, Roy
    Analyzing p-bodies and stress granules in Saccharomyces cerevisae2010In: Guide to yeast genetics: functional genomics, proteomics, and other systems analysis / [ed] Jonathan Weissman, Christine Guthrie, Gerald R. Fink, San Diego: Academic Press, 2010, 2, Vol. 470, p. 619-640Chapter in book (Refereed)
    Abstract [en]

    Eukaryotic cells contain at least two types of cytoplasmic RNA protein (RNP) granules that contain nontranslating mRNAs. One such RNP granule is a P-body, which contains translationally inactive mRNAs and proteins involved in mRNA degradation and translation repression. A second such RNP granule is a stress granule which also contains mRNAs, some RNA binding proteins and several translation initiation factors, suggesting these granules contain mRNAs stalled in translation initiation. In this chapter, we describe methods to analyze P-bodies and stress granules in Saccharomyces cerevisiae, including procedures to determine if a protein or mRNA can accumulate in either granule, if an environmental perturbation or mutation affects granule size and number, and granule quantification methods.

  • 92.
    Buckland, Robert
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    DNA precursor asymmetries, Mismatch Repair and their effect on mutation specificity2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In order to build any structure, a good supply of materials, accurate workers and quality control are needed. This is even the case when constructing DNA, the so-called “Code of Life.” For a species to continue to exist, this DNA code must be copied with incredibly high accuracy when each and every cell replicates. In fact, just one mistake in the 12 million bases that comprise the genome of budding yeast, Saccharomyces cerevisiae, can be fatal. DNA is composed of a double strand helix made up of just four different bases repeated millions of times. The building blocks of DNA are the deoxyribonucleotides (dNTPs); dCTP, dTTP, dATP and dGTP. Their production and balance are carefully controlled within each cell, largely by the key enzyme Ribonucleotide Reductase (RNR). Here, we studied how the enzymes that copy DNA, the replicative polymerases α, δ and ε, cope with the effects of an altered dNTP pool balance. An introduced mutation in the allosteric specificity site of RNR in a strain of S. cerevisiae, rnr1-Y285A, leads to elevated dCTP and dTTP levels and has been shown to have a 14-fold increase in mutation rate compared to wild type. To ascertain the full effects of the dNTP pool imbalance upon the replicative polymerases, we disabled one of the major quality control systems in a cell that corrects replication errors, the post-replicative Mismatch Repair system. Using both the CAN1 reporter assay and whole genome sequencing, we found that, despite inherent differences between the polymerases, their replication fidelity was affected very similarly by this dNTP pool imbalance. Hence, the high dCTP and dTTP forced Pol ε and Pol α/δ to make the same mistakes. In addition, the mismatch repair machinery was found to correct replication errors driven by this dNTP pool imbalance with highly variable efficiencies. Another mechanism to protect cells from DNA damage during replication is a checkpoint that can be activated to delay the cell cycle and activate repair mechanisms. In yeast, Mec1 and Rad53 (human ATR and Chk1/Chk2) are two key S-phase checkpoint proteins. They are essential as they are also required for normal DNA replication and dNTP pool regulation. However the reason why they are essential is not well understood. We investigated this by mutating RAD53 and analyzing dNTP pools and gene interactions. We show that Rad53 is essential in S-phase due to its role in regulating basal dNTP levels by action in the Dun1 pathway that regulates RNR and Rad53’s compensatory kinase function if dNTP levels are perturbed.

    In conclusion we present further evidence of the importance of dNTP pools in the maintenance of genome integrity and shed more light on the complex regulation of dNTP levels.

  • 93.
    Bunikis, Ignas
    Umeå University, Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Borrelia channel-forming proteins: structure and function2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Borrelia is a Gram-negative, corkscrew-shaped bacterium transmitted by infected ticks or lice. Borreliae are subdivided into pathogens of two diseases: Lyme disease, caused mainly by B. burgdorferi, B. afzelii and B. garinii; and relapsing fever caused primarily by B. duttonii, B. hermsii, B. recurrentis or B. crocidurae. Both diseases differ in their manifestations, duration times and dissemination patterns. Antibiotics are the major therapeutics, although unfortunately antibiotic treatment is not always beneficial. To date, drug resistance mechanisms in B. burgdorferi are unknown. Transporters of the resistance-nodulation-division (RND) family appear to be involved in drug resistance, especially in Gram-negative bacteria. They consist of three components: a cytoplasmic membrane export system, a membrane fusion protein (MFP), and an outer membrane factor (OMP). The major antibiotic efflux activity of this type in Escherichia coli is mediated by the tripartite multidrug resistance pump AcrAB-TolC. Based on the sequence homology we conclude that the besA (bb0140), besB (bb0141) and besC (bb0142) genes code for a similar efflux system in B. burgdorferi. We created a deletion mutant of besC. The minimal inhibitory concentration (MIC) values of B. burgdorferi carrying an inactive besC gene were 4- to 8-fold lower than in the wild type strain. Animal experiments showed that the besC mutant was unable to infect mice. Black lipid bilayer experiments were carried out to determine the biophysical properties of purified BesC. This study showed the importance of BesC protein for B. burgdorferi pathogenicity and resistance to antibiotics, although its importance in clinical isolates is not known.

    Due to its small genome, Borrelia is metabolically and biosynthetically deficient, thereby making it highly dependent on nutrients provided by their hosts. The uptake of nutrients by Borrelia is not yet completely understood. We describe the purification and characterization of a 36-kDa protein that functions as a putative dicarboxylate-specific porin in the outer membrane of Borrelia. The protein was designated as DipA, for dicarboxylate-specific porin A. DipA was biophysically characterized using the black lipid bilayer assay. The permeation of KCl through the channel could be partly blocked by titrating the DipA-mediated membrane conductance with increasing concentrations of different organic dicarboxylic anions. The obtained results imply that DipA does not form a general diffusion pore, but a porin with a binding site specific for dicarboxylates which play important key roles in the deficient metabolic and biosynthetic pathways of Borrelia species.

    The presence of porin P66 has been shown in both Lyme disease and relapsing fever spirochetes. In our study, purified P66 homologues from Lyme disease species B. burgdorferi, B. afzelii and B. garinii and relapsing fever species B. duttonii, B. recurrentis and B. hermsii were compared and their biophysical properties were further characterized in black lipid bilayer assay. Subsequently, the channel diameter of B. burgdorferi P66 was investigated in more detail. For this study, different nonelectrolytes with known hydrodynamic radii were used. This allowed us to determine the effective diameter of the P66 channel lumen. Furthermore, the blockage of the channel after addition of nonelectrolytes revealed seven subconducting states and indicated a heptameric structure of the P66 channel. These results may give more insight into the functional properties of this important porin.

  • 94.
    Bunikis, Ignas
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Denker, Katrin
    Östberg, Yngve
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Andersen, Christian
    Benz, Roland
    Bergström, Sven
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    An RND-type efflux system in Borrelia burgdorferi is involved in virulence and resistance to antimicrobial compounds2008In: PLoS Pathogenicity, ISSN 1553-7374, Vol. 4, no 2, p. e1000009-Article in journal (Refereed)
    Abstract [en]

    Borrelia burgdorferi is remarkable for its ability to thrive in widely different environments due to its ability to infect various organisms. In comparison to enteric Gram-negative bacteria, these spirochetes have only a few transmembrane proteins some of which are thought to play a role in solute and nutrient uptake and excretion of toxic substances. Here, we have identified an outer membrane protein, BesC, which is part of a putative export system comprising the components BesA, BesB and BesC. We show that BesC, a TolC homolog, forms channels in planar lipid bilayers and is involved in antibiotic resistance. A besC knockout was unable to establish infection in mice, signifying the importance of this outer membrane channel in the mammalian host. The biophysical properties of BesC could be explained by a model based on the channel-tunnel structure. We have also generated a structural model of the efflux apparatus showing the putative spatial orientation of BesC with respect to the AcrAB homologs BesAB. We believe that our findings will be helpful in unraveling the pathogenic mechanisms of borreliae as well as in developing novel therapeutic agents aiming to block the function of this secretion apparatus.

  • 95. Bunikis, J
    et al.
    Noppa, L
    Östberg, Yngve
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Barbour, A G
    Bergström, Sven
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Surface exposure and species specificity of an immunoreactive domain of a 66-kilodalton outer membrane protein (P66) of the Borrelia spp. that cause Lyme disease1996In: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 64, no 12, p. 5111-5116Article in journal (Refereed)
    Abstract [en]

    A chromosomally encoded 66-kDa protein (P66) of Borrelia spp. that cause Lyme disease has previously been shown to be associated with the spirochetal outer membrane. A topological model of P66 predicts a surface-exposed fragment which links the N- and C-terminal intramembranous domains of the protein (J. Bunikis, L. Noppa, and S. Bergström, FEMS Microbiol. Lett. 131:139-145, 1995). In the present study, an immunogenic determinant of P66 was identified by a comparison of the immunoreactivities of different fragments of P66 generated either by proteolytic treatment of intact spirochetes or as recombinant proteins expressed in Escherichia coli. The immune response to P66 during natural infection was found to be directed against the predicted surface domain which comprises amino acids at positions 454 through 491. A sequence comparison revealed considerable polymorphism of the surface domains of P66 proteins of different Lyme disease-causing Borrelia species. Five sequence patterns of this domain were observed in the B. garinii strains studied. In contrast, sequences of the relevant part of P66 of the B. afzelii and B. burgdorferi sensu stricto isolates studied were identical within the respective species. In immunoblotting, 5 of 17 (29.4%) sera from North American patients with early disseminated or persistent Lyme disease reacted against P66 of B. burgdorferi sensu stricto B31. These sera, however, failed to recognize P66 of B. afzelii and B. garinii, as well as an analog of P66 in the relapsing fever agent, B. hermsii. In conclusion, the topological model of P66 is supported by the demonstration of an apparent surface localization of an immunoreactive domain of this protein. Furthermore, analogous to the plasmid-encoded borrelial outer surface proteins, the predicted surface-exposed portion of chromosomally encoded P66 appears to be antigenically heterogenous.

  • 96.
    Bárcena-Uribarri, Iván
    et al.
    Universität Würzburg, Germany.
    Thein, Marcus
    Universität Würzburg and Jacobs University Bremen, Germany.
    Maier, Elke
    Universität Würzburg, Germany.
    Bonde, Mari
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Bunikis, Ignas
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Bergström, Sven
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Benz, Roland
    Universität Würzburg, Germany.
    Use of nonelectrolytes reveals the channel size and oligomeric constitution of the Borrelia burgdorferi P66 porinManuscript (preprint) (Other academic)
    Abstract [en]

    The outer membrane protein P66 of the Lyme disease spirochete Borrelia burgdorferi is capable of pore formation with an atypical high single-channel conductance of 11 nS in 1 M KCl. We studied in a non-theoretical manner the diameter of the P66 channel by analyzing its single-channel conductance in black lipid bilayers in the presence of different nonelectrolytes with known hydrodynamic radii. Furthermore, we calculated the filling of the channel with these nonelectrolytes and the results revealed that nonelectrolytes with hydrodynamic radii of 0.34 nm or smaller pass through the pore, whereas neutral molecules with greater radii only partially filled the channel or were not able to enter it at all. Thus, the diameter of the P66 entrance was determined to be ≤ 1.9 nm with a constriction site diameter of about 0.7 nm. Furthermore, the P66-induced membrane conductance could be blocked by 80-90% after addition of the nonelectrolytes PEG 400, PEG 600 and maltohexaose in the low millimolar range. Interestingly, the analysis of the power density spectra of P66 after blockage with nonelectrolytes revealed no chemical interaction responsible for channel block. The blockage of one P66 single-channel conductance unit of 11 nS occurred by seven subconducting states, thus indicating a heptameric organization of the P66 oligomer. This organization of P66 as a heptamer was confirmed by Blue Native PAGE and immunoblot analysis, which demonstrated that P66 forms a complex with a mass of approximately 460 kDa.

  • 97.
    Bárcena-Uribarri, Iván
    et al.
    University of Würzburg.
    Thein, Marcus
    Max Planck Institute for Developmental Biology.
    Sacher, Anna
    German Cancer Research Center.
    Bunikis, Ignas
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Bonde, Mari
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Bergström, Sven
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Benz, Roland
    University of Würzburg.
    P66 porins are present in both Lyme disease and relapsing fever spirochetes: a comparison of the biophysical properties of P66 porins from six Borrelia species2010In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1798, no 6, p. 1197-1203Article in journal (Refereed)
    Abstract [en]

    The genus Borrelia is the cause of the two human diseases: Lyme disease (LD) and relapsing fever (RF). BothLD and RF Borrelia species are obligate parasites and are dependent on nutrients provided by their hosts. Thefirst step of nutrient uptake across the outer membrane of these Gram-negative bacteria is accomplished bywater-filled channels, so-called porins. The knowledge of the porin composition in the outer membranes ofthe different pathogenic Borrelia species is limited. Only one porin has been described in relapsing feverspirochetes to date, whereas four porins are known to be present in Lyme disease agents. From these, theBorrelia burgdorferi outer membrane channel P66 is known to act as an adhesin and was well studied as aporin. To investigate if P66 porins are expressed and similarly capable of pore formation in other Borreliacausing Lyme disease or relapsing fever three LD species (B. burgdorferi, B. afzelii, B. garinii) and three RFspecies (B. duttonii, B. recurrentis and B. hermsii) were investigated for outer membrane proteins homologousto P66. A search in current published RF genomes, comprising the ones of B. duttonii, B. recurrentis and B.hermsii, indicated that they all contained P66 homologues. The P66 homologues of the six Borrelia specieswere purified to homogeneity and their pore-forming abilities as well as the biophysical properties of thepores were analyzed using the black lipid bilayer assay.

  • 98.
    Bäckström, Stefan
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Elfving, Nils
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Nilsson, Robert
    Wingsle, Gunnar
    Björklund, Stefan
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Purification of a plant mediator from Arabidopsis thaliana identifies PFT1 as the Med25 subunit2007In: Molecular Cell, ISSN 1097-2765, E-ISSN 1097-4164, Vol. 26, no 5, p. 717-729Article in journal (Refereed)
  • 99.
    Bäreclev, Caroline
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Vaitkevicius, Karolis
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Netterling, Sakura
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Johansson, Jörgen
    DExD-box RNA-helicases in Listeria monocytogenes are important for growth, ribosomal maturation, rRNA processing and virulence factor expression2014In: RNA Biology, ISSN 1547-6286, E-ISSN 1555-8584, Vol. 11, no 11, p. 1458-1467Article in journal (Refereed)
    Abstract [en]

    RNA-helicases are proteins required for the unwinding of occluding secondary RNA structures, especially at low temperatures. In this work, we have deleted all 4 DExD-box RNA helicases in various combinations in the Gram-positive pathogen Listeria monocytogenes. Our results show that 3 out of 4 RNA-helicases were important for growth at low temperatures, whereas the effect was less prominent at 37 degrees C. Over-expression of one RNA-helicase, Lmo1450, was able to overcome the reduced growth of the quadruple mutant strain at temperatures above 26 degrees C, but not at lower temperatures. The maturation of ribosomes was affected in different degrees in the various strains at 20 degrees C, whereas the effect was marginal at 37 degrees C. This was accompanied by an increased level of immature 23S rRNA precursors in some of the RNA-helicase mutants at low temperatures. Although the expression of the PrfA regulated virulence factors ActA and LLO decreased in the quadruple mutant strain, this strain showed a slightly increased infection ability. Interestingly, even though the level of the virulence factor LLO was decreased in the quadruple mutant strain as compared with the wild-type strain, the hly-transcript (encoding LLO) was increased. Hence, our results could suggest a role for the RNA-helicases during translation. In this work, we show that DExD-box RNA-helicases are involved in bacterial virulence gene-expression and infection of eukaryotic cells.

  • 100.
    Bönquist, Linda
    et al.
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    Lindgren, Helena
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    Golovliov, Igor
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    Guina, Tina
    Sjöstedt, Anders
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
    MglA and Igl proteins contribute to the modulation of Francisella tularensis live vaccine strain-containing phagosomes in murine macrophages2008In: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 76, no 8, p. 3502-3510Article in journal (Refereed)
    Abstract [en]

    The Francisella tularensis live vaccine strain (LVS), in contrast to its iglC mutant, replicates in the cytoplasm of macrophages. We studied the outcome of infection of the murine macrophagelike cell line J774A.1 with LVS and with iglC, iglD, and mglA mutants, the latter of which is deficient in a global regulator. Compared to LVS, all of the mutants showed impaired intracellular replication up to 72 h, and the number of the mglA mutant bacteria even decreased. Colocalization with LAMP-1 was significantly increased for all mutants compared to LVS, indicating an impaired ability to escape into the cytoplasm. A lysosomal acidity-dependent dye accumulated in approximately 40% of the vacuoles containing mutant bacteria but not at all in vacuoles containing LVS. Preactivation of the macrophages with gamma interferon inhibited the intracellular growth of all strains and significantly increased acidification of phagosomes containing the mutants, but it only slightly increased the LAMP-1 colocalization. The intracellular replication and phagosomal escape of the iglC and iglD mutants were restored by complementation in trans. In conclusion, the IglC, IglD, and MglA proteins each directly or indirectly critically contribute to the virulence of F. tularensis LVS, including its intracellular replication, cytoplasmic escape, and inhibition of acidification of the phagosomes.

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