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  • 1.
    Aguilar, Ximena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Blomberg, Jeanette
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Brännström, Kristoffer
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Schleucher, Jurgen
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Björklund, Stefan
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Interaction Studies of the Human and Arabidopsis thaliana Med25-ACID Proteins with the Herpes Simplex Virus VP16-and Plant-Specific Dreb2a Transcription Factors2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 5, e98575- p.Article in journal (Refereed)
    Abstract [en]

    Mediator is an evolutionary conserved multi-protein complex present in all eukaryotes. It functions as a transcriptional coregulator by conveying signals from activators and repressors to the RNA polymerase II transcription machinery. The Arabidopsis thaliana Med25 (aMed25) ACtivation Interaction Domain (ACID) interacts with the Dreb2a activator which is involved in plant stress response pathways, while Human Med25-ACID (hMed25) interacts with the herpes simplex virus VP16 activator. Despite low sequence similarity, hMed25-ACID also interacts with the plant-specific Dreb2a transcriptional activator protein. We have used GST pull-down-, surface plasmon resonance-, isothermal titration calorimetry and NMR chemical shift experiments to characterize interactions between Dreb2a and VP16, with the hMed25 and aMed25-ACIDs. We found that VP16 interacts with aMed25-ACID with similar affinity as with hMed25-ACID and that the binding surface on aMed25-ACID overlaps with the binding site for Dreb2a. We also show that the Dreb2a interaction region in hMed25-ACID overlaps with the earlier reported VP16 binding site. In addition, we show that hMed25-ACID/Dreb2a and aMed25-ACID/Dreb2a display similar binding affinities but different binding energetics. Our results therefore indicate that interaction between transcriptional regulators and their target proteins in Mediator are less dependent on the primary sequences in the interaction domains but that these domains fold into similar structures upon interaction.

  • 2.
    Blomberg, Jeanette
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Aguilar, Ximena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Brännström, Kristoffer
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Rautio, Linn
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Wittung-Stafshede, Pernilla
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björklund, Stefan
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Interactions between DNA, transcriptional regulator Dreb2a and the Med25 mediator subunit from Arabidopsis thaliana involve conformational changes2012In: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 40, no 13, 5938-5950 p.Article in journal (Refereed)
    Abstract [en]

    Mediator is a multiprotein coregulatory complex that conveys signals from DNA-bound transcriptional regulators to the RNA polymerase II transcription machinery in eukaryotes. The molecular mechanisms for how these signals are transmitted are still elusive. By using purified transcription factor Dreb2a, mediator subunit Med25 from Arabidopsis thaliana, and a combination of biochemical and biophysical methods, we show that binding of Dreb2a to its canonical DNA sequence leads to an increase in secondary structure of the transcription factor. Similarly, interaction between the Dreb2a and Med25 in the absence of DNA results in conformational changes. However, the presence of the canonical Dreb2a DNA-binding site reduces the affinity between Dreb2a and Med25. We conclude that transcription regulation is facilitated by small but distinct changes in energetic and structural parameters of the involved proteins.

  • 3.
    Brännström, Kristoffer
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Lindhagen Persson, Malin
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Gharabyan, A
    Vestling, M
    Brännström, Thomas
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Morozova-Roche, Ludmilla
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Design of oligomer-specific antibodiesManuscript (preprint) (Other academic)
  • 4.
    Brännström, Kristoffer
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Lindhagen-Persson, Malin
    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.
    Vestling, Monika
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Sellin, Mikael E.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Brännström, Thomas
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Morozova-Roche, Ludmilla
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Forsgren, Lars
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    A Generic Method for Design of Oligomer-Specific Antibodies2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 3, e90857- p.Article in journal (Refereed)
    Abstract [en]

    Antibodies that preferentially and specifically target pathological oligomeric protein and peptide assemblies, as opposed to their monomeric and amyloid counterparts, provide therapeutic and diagnostic opportunities for protein misfolding diseases. Unfortunately, the molecular properties associated with oligomer-specific antibodies are not well understood, and this limits targeted design and development. We present here a generic method that enables the design and optimisation of oligomer-specific antibodies. The method takes a two-step approach where discrimination between oligomers and fibrils is first accomplished through identification of cryptic epitopes exclusively buried within the structure of the fibrillar form. The second step discriminates between monomers and oligomers based on differences in avidity. We show here that a simple divalent mode of interaction, as within e. g. the IgG isotype, can increase the binding strength of the antibody up to 1500 times compared to its monovalent counterpart. We expose how the ability to bind oligomers is affected by the monovalent affinity and the turnover rate of the binding and, importantly, also how oligomer specificity is only valid within a specific concentration range. We provide an example of the method by creating and characterising a spectrum of different monoclonal antibodies against both the A beta peptide and alpha-synuclein that are associated with Alzheimer's and Parkinson's diseases, respectively. The approach is however generic, does not require identification of oligomer-specific architectures, and is, in essence, applicable to all polypeptides that form oligomeric and fibrillar assemblies.

  • 5.
    Brännström, Kristoffer
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Öhman, Anders
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Lindhagen-Persson, Malin
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Ca2+ enhances Aβ polymerization rate and fibrillar stability in a dynamic manner2013In: Biochemical Journal, ISSN 0264-6021, E-ISSN 1470-8728, Vol. 450, 189-197 p.Article in journal (Refereed)
    Abstract [en]

    Identifying factors that affect the self-assembly of the amyloid-β peptide (Aβ) is of utmost importance in the quest to understand the molecular mechanisms causing Alzheimer's disease (AD). Ca2+ has previously been shown to accelerate both Aβ fibril nucleation and maturation, and a dysregulated Ca2+ homeostasis frequently correlates with development of AD. The mechanisms regarding Ca2+ binding as well as its effect on fibril kinetics are not fully understood. Using a polymerization assay we show that Ca2+ in a dynamic and reversible manner enhances both the elongation rate and fibrillar stability, where specifically the "dock and lock" phase mechanism is enhanced. Through NMR analysis we found that Ca2+ affects the fibrillar architecture. In addition, and unexpectedly, we found that Ca2+ does not bind the free Aβ monomer. This implies that Ca2+ binding requires an architecture adopted by assembled peptides, and consequently is mediated through intermolecular interactions between adjacent peptides. This gives a mechanistic explanation to the enhancing effect on fibril maturation and indicates structural similarities between prefibrillar structures and mature amyloid. Taken together we expose how Ca2+ levels affect the delicate equilibrium between the monomeric and assembled Aβ and how fluctuations in vivo may contribute to development and progression of the disease.

  • 6.
    Brännström, Kristoffer
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Öhman, Anders
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Nilsson, Lina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Pihl, Mathias
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Sandblad, Linda
    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.
    The N-terminal Region of Amyloid β Controls the Aggregation Rate and Fibril Stability at Low pH Through a Gain of Function Mechanism2014In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, no 31, 10956-10964 p.Article in journal (Refereed)
    Abstract [en]

    Alzheimer's disease is linked to a pathological polymerization of the endogenous amyloid β-peptide (Aβ) that ultimately forms amyloid plaques within the human brain. We used surface plasmon resonance (SPR) to measure the kinetic properties of Aβ fibril formation under different conditions during the polymerization process. For all polymerization processes, a critical concentration of free monomers, as defined by the dissociation equilibrium constant (KD), is required for the buildup of the polymer, for example, amyloid fibrils. At concentrations below the KD, polymerization cannot occur. However, the KD for Aβ has previously been shown to be several orders of magnitude higher than the concentrations found in the cerebrospinal and interstitial fluids of the human brain, and the mechanism by which Aβ amyloid forms in vivo has been a matter of debate. Using SPR, we found that the KD of Aβ dramatically decreases as a result of lowering the pH. Importantly, this effect enables Aβ to polymerize within a picomolar concentration range that is close to the physiological Aβ concentration within the human brain. The stabilizing effect is dynamic, fully reversible, and notably pronounced within the pH range found within the endosomal and lysosomal pathways. Through sequential truncation, we show that the N-terminal region of Aβ contributes to the enhanced fibrillar stability due to a gain of function mechanism at low pH. Our results present a possible route for amyloid formation at very low Aβ concentrations and raise the question of whether amyloid formation in vivo is restricted to a low pH environment. These results have general implications for the development of therapeutic interventions.

  • 7.
    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.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Aβ peptide fibrillar architectures controlled by conformational constraints of the monomer2011In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 9, e25157- p.Article in journal (Refereed)
    Abstract [en]

    Anomalous self-assembly of the Aβ peptide into fibrillar amyloid deposits is strongly correlated with the development of Alzheimer's disease. Aβ fibril extension follows a template guided "dock and lock" mechanism where polymerisation is catalysed by the fibrillar ends. Using surface plasmon resonance (SPR) and quenched hydrogen-deuterium exchange NMR (H/D-exchange NMR), we have analysed the fibrillar structure and polymerisation properties of both the highly aggregation prone Aβ1-40 Glu22Gly (Aβ(40Arc)) and wild type Aβ1-40 (Aβ(40WT)). The solvent protection patterns from H/D exchange experiments suggest very similar structures of the fibrillar forms. However, through cross-seeding experiments monitored by SPR, we found that the monomeric form of Aβ(40WT) is significantly impaired to acquire the fibrillar architecture of Aβ(40Arc). A detailed characterisation demonstrated that Aβ(40WT) has a restricted ability to dock and isomerise with high binding affinity onto Aβ(40Arc) fibrils. These results have general implications for the process of fibril assembly, where the rate of polymerisation, and consequently the architecture of the formed fibrils, is restricted by conformational constraints of the monomers. Interestingly, we also found that the kinetic rate of fibril formation rather than the thermodynamically lowest energy state determines the overall fibrillar structure.

  • 8.
    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, 369-377 p.Article 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.

  • 9.
    Byström, Roberth
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Aisenbrey, Christopher
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Borowik, Tomasz
    Bokvist, Marcus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindström, Fredrick
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sani, Marc-Antoine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Gröbner, Gerhard
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Disordered proteins: Biological membranes as two-dimensional aggregation matrices2008In: Cell Biochemistry and Biophysics, ISSN 1085-9195, E-ISSN 1559-0283, Vol. 52, no 3, 175-189 p.Article, review/survey (Refereed)
    Abstract [en]

    Aberrant folded proteins and peptides are hallmarks of amyloidogenic diseases. However, the molecular processes that cause these proteins to adopt non-native structures in vivo and become cytotoxic are still largely unknown, despite intense efforts to establish a general molecular description of their behavior. Clearly, the fate of these proteins is ultimately linked to their immediate biochemical environment in vivo. In this review, we focus on the role of biological membranes, reactive interfaces that not only affect the conformational stability of amyloidogenic proteins, but also their aggregation rates and, probably, their toxicity. We first provide an overview of recent work, starting with findings regarding the amphiphatic amyloid-β protein (Aβ), which give evidence that membranes can directly promote aggregation, and that the effectiveness in this process can be related to the presence of specific neuronal ganglioside lipids. In addition, we discuss the implications of recent research (medin as an detailed example) regarding putative roles of membranes in the misfolding behavior of soluble, non-amphiphatic proteins, which are attracting increasing interest. The potential role of membranes in exerting the toxic action of misfolded proteins will also be highlighted in a molecular context. In this review, we discuss novel NMR-based approaches for exploring membrane–protein interactions, and findings obtained using them, which we use to develop a molecular concept to describe membrane-mediated protein misfolding as a quasi-two-dimensional process rather than a three-dimensional event in a biochemical environment. The aim of the review is to provide researchers with a general understanding of the involvement of membranes in folding/misfolding processes in vivo, which might be quite universal and important for future research concerning amyloidogenic and misfolding proteins, and possible ways to prevent their toxic actions.

  • 10.
    Eneqvist, Therese
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Andersson, Karin
    Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Olofsson, Anders
    Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Lundgren, Erik
    Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    The beta-slip: a novel concept in transthyretin amyloidosis.2000In: Mol Cell, ISSN 1097-2765, Vol. 6, no 5, 1207-18 p.Article in journal (Refereed)
    Abstract [en]

    Transthyretin is a tetrameric plasma protein associated with two forms of amyloid disease. The structure of the highly amyloidogenic transthyretin triple mutant TTRG53S/E54D/L55S determined at 2.3 A resolution reveals a novel conformation: the beta-slip. A three-residue shift in beta strand D places Leu-58 at the position normally occupied by Leu-55 now mutated to serine. The beta-slip is best defined in two of the four monomers, where it makes new protein-protein interactions to an area normally involved in complex formation with retinol-binding protein. This interaction creates unique packing arrangements, where two protein helices combine to form a double helix in agreement with fiber diffraction and electron microscopy data. Based on these findings, a novel model for transthyretin amyloid formation is presented.

  • 11.
    Eneqvist, Therese
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Olofsson, Anders
    Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Ando, Yukio
    Miyakawa, Taihei
    Katsuragi, Shoichi
    Jass, Jana
    Molecular Biology (Faculty of Medicine).
    Lundgren, Erik
    Molecular Biology (Faculty of Medicine).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Disulfide-bond formation in the transthyretin mutant Y114C prevents amyloid fibril formation in vivo and in vitro.2002In: Biochemistry, ISSN 0006-2960, Vol. 41, no 44, 13143-51 p.Article in journal (Refereed)
    Abstract [en]

    The Y114C mutation in human transthyretin (TTR) is associated with a particular form of familial amyloidotic polyneuropathy. We show that vitreous aggregates ex vivo consist of either regular amyloid fibrils or disordered disulfide-linked precipitates that maintain the ability to bind Congo red. Furthermore, we demonstrate in vitro that the ATTR Y114C mutant exists in three forms: one unstable but nativelike tetrameric form, one highly aggregated form in which a network of disulfide bonds is formed, and one fibrillar form. The disulfide-linked aggregates and the fibrillar form of the mutant can be induced by heat induction under nonreduced and reduced conditions, respectively. Both forms are recognized by the amyloid specific antibody MAB(39-44). In a previous study, we have linked exposure of this epitope in TTR to a three-residue shift in beta-strand D. The X-ray crystallographic structure of reduced tetrameric ATTR Y114C shows a structure similar to that of the wild type but with a more buried position of Cys10 and with beta-mercaptoethanol associated with Cys114, verifying the strong tendency for this residue to form disulfide bonds. Combined with the ex vivo data, our in vitro findings suggest that ATTR Y114C can lead to disease either by forming regular unbranched amyloid fibrils or by forming disulfide-linked aggregates that maintain amyloid-like properties but are unable to form regular amyloid fibrils.

  • 12.
    Gharibyan, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Narayana, Vinod
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Ankarcrona, Maria
    Karolinska Institute.
    Brännström, Thomas
    Umeå University, Faculty of Medicine, Department of Medical Biosciences.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Morozova-Roche, Ludmilla
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Emerging role of inflammatory S100A9 in Alzheimer’s disease amyloid growth and neurodegenerationManuscript (preprint) (Other academic)
  • 13.
    Gharibyan, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Narayana, Vinod
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Habib, Ahsan
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Sulniute, Rima
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Henein, Michael
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Morozova-Roche, Ludmilla
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Inflammatory S100A9 and Aβ amyloids in heart valve of patient with aortic stenosisManuscript (preprint) (Other academic)
  • 14. Hammer, Neal D
    et al.
    McGuffie, Bryan A
    Zhou, Yizhou
    Badtke, Matthew P
    Reineke, Ashley A
    Brännström, Kristoffer
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Gestwicki, Jason E
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Chapman, Matthew R
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    The C-terminal repeating units of CsgB direct bacterial functional amyloid nucleation2012In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 422, no 3, 376-389 p.Article in journal (Refereed)
    Abstract [en]

    Curli are functional amyloids produced by enteric bacteria. The major curli fiber subunit, CsgA, self-assembles into an amyloid fiber in vitro. The minor curli subunit protein, CsgB, is required for CsgA polymerization on the cell surface. Both CsgA and CsgB are composed of five predicted β–strand-loop-β–strand-loop repeating units that feature conserved glutamine and asparagine residues. Because of this structural homology, we proposed that CsgB might form an amyloid template that initiates CsgA polymerization on the cell surface. To test this model, we purified wild-type CsgB, and found that it self-assembled into amyloid fibers in vitro. Preformed CsgB fibers seeded CsgA polymerization as did soluble CsgB added to the surface of cells secreting soluble CsgA. To define the molecular basis of CsgB nucleation, we generated a series of mutants that removed each of the five repeating units. Each of these CsgB deletion mutants was capable of self-assembly in vitro. In vivo, membrane-localized mutants lacking the 1st, 2nd or 3rd repeating units were able to convert CsgA into fibers. However, mutants missing either the 4th or 5th repeating units were unable to complement a csgB mutant. These mutant proteins were not localized to the outer membrane, but were instead secreted into the extracellular milieu. Synthetic CsgB peptides corresponding to repeating units 1, 2 and 4 self assembled into ordered amyloid polymers, while peptides corresponding to repeating units 3 and 5 did not, suggesting that there are redundant amyloidogenic domains in CsgB. Our results suggest a model where the rapid conversion of CsgB from unstructured protein to a β-sheet-rich amyloid template anchored to the cell surface is mediated by the C-terminal repeating units.

  • 15.
    Horvath, Istvan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sellstedt, Magnus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Weise, Christoph
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nordvall, Lina-Maria
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Golla, Krishna Prasad
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Larsson, Göran
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wittung-Stafshede, Pernilla
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Modulation of α-synuclein fibrillization by ring-fused 2-pyridones: templation and inhibition involve oligomers with different structure2013In: Archives of Biochemistry and Biophysics, ISSN 0003-9861, E-ISSN 1096-0384, Vol. 532, no 2, 84-90 p.Article in journal (Refereed)
    Abstract [en]

    In a recent study we discovered that a ring-fused 2-pyridone compound triggered fibrillization of a key protein in Parkinson's disease, α-synuclein. To reveal how variations in compound structure affect protein aggregation, we now prepared a number of strategic analogs and tested their effects on α-synuclein amyloid fiber formation in vitro. We find that, in contrast to the earlier templating effect, some analogs inhibit α-synuclein fibrillization. For both templating and inhibiting compounds, the key species formed in the reactions are α-synuclein oligomers that contain compound. Despite similar macroscopic appearance, the templating and inhibiting oligomers are distinctly different in secondary structure content. When the inhibitory oligomers are added in seed amounts, they inhibit fresh α-synuclein aggregation reactions. Our study demonstrates that small chemical changes to the same central fragment can result in opposite effects on protein aggregation.

  • 16.
    Horvath, Istvan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Weise, Christoph F
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Andersson, Emma K
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Chorell, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sellstedt, Magnus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bengtsson, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Hultgren, Scott J
    Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, United States.
    Chapman, Matthew
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Wolf-Watz, Magnus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Wittung-Stafshede, Pernilla
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mechanisms of Protein Oligomerization: Inhibitor of Functional Amyloids Templates α-Synuclein Fibrillation2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 7, 3439-3444 p.Article in journal (Refereed)
    Abstract [en]

    Small organic molecules that inhibit functional bacterial amyloid fibers, curli, are promising new antibiotics. Here we investigated the mechanism by which the ring-fused 2-pyridone FN075 inhibits fibrillation of the curli protein CsgA. Using a variety of biophysical techniques, we found that FN075 promotes CsgA to form off-pathway, non-amyloidogenic oligomeric species. In light of the generic properties of amyloids, we tested whether FN075 would also affect the fibrillation reaction of human α-synuclein, an amyloid-forming protein involved in Parkinson's disease. Surprisingly, FN075 stimulates α-synuclein amyloid fiber formation as measured by thioflavin T emission, electron microscopy (EM), and atomic force microscopy (AFM). NMR data on (15)N-labeled α-synuclein show that upon FN075 addition, α-synuclein oligomers with 7 nm radius form in which the C-terminal 40 residues remain disordered and solvent exposed. The polypeptides in these oligomers contain β-like secondary structure, and the oligomers are detectable by AFM, EM, and size-exclusion chromatography (SEC). Taken together, FN075 triggers oligomer formation of both proteins: in the case of CsgA, the oligomers do not proceed to fibers, whereas for α-synuclein, the oligomers are poised to rapidly form fibers. We conclude that there is a fine balance between small-molecule inhibition and templation that depends on protein chemistry.

  • 17.
    Hörnberg, Andreas
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Eneqvist, Therese
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Olofsson, Anders
    Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Lundgren, Erik
    Faculty of Medicine, Molecular Biology (Faculty of Medicine).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    A comparative analysis of 23 structures of the amyloidogenic protein transthyretin.2000In: J Mol Biol, ISSN 0022-2836, Vol. 302, no 3, 649-69 p.Article in journal (Refereed)
    Abstract [en]

    Self-assembly of the human plasma protein transthyretin (TTR) into unbranched insoluble amyloid fibrils occurs as a result of point mutations that destabilize the molecule, leading to conformational changes. The tertiary structure of native soluble TTR and many of its disease-causing mutants have been determined. Several independent studies by X-ray crystallography have suggested structural differences between TTR variants which are claimed to be of significance for amyloid formation. As these changes are minor and not consistent between the studies, we have compared all TTR structures available at the protein data bank including three wild-types, three non-amyloidogenic mutants, seven amyloidogenic mutants and nine complexes. The reference for this study is a new 1.5 A resolution structure of human wild-type TTR refined to an R-factor/R-free of 18.6 %/21.6 %. The present findings are discussed in the light of the previous structural studies of TTR variants, and show the reported structural differences to be non-significant.

  • 18.
    Hörnberg, Andreas
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Eneqvist, Therese
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Lundgren, Erik
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    The β-strand D of transthyretin trapped in two discrete conformations2004In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1700, no 1, 93-104 p.Article in journal (Refereed)
    Abstract [en]

    Conformational changes in native and variant forms of the human plasma protein transthyretin (TTR) induce several types of amyloid diseases. Biochemical and structural studies have mapped the initiation site of amyloid formation onto residues at the outer C and D beta-strands and their connecting loop. In this study, we characterise an engineered variant of transthyretin, Ala108Tyr/Leu110Glu, which is kinetically and thermodynamically more stable than wild-type transthyretin, and as a consequence less amyloidogenic. Crystal structures of the mutant were determined in two space groups, P2(1)2(1)2 and C2, from crystals grown in the same crystallisation set-up. The structures are identical with the exception for residues Leu55-Leu58, situated at beta-strand D and the following DE loop. In particular, residues Leu55-His56 display large shifts in the C2 structure. There the direct hydrogen bonding between beta-strands D and A has been disrupted and is absent, whereas the beta-strand D is present in the P2(1)2(1)2 structure. This difference shows that from a mixture of metastable TTR molecules, only the molecules with an intact beta-strand D are selected for crystal growth in space group P2(1)2(1)2. The packing of TTR molecules in the C2 crystal form and in the previously determined amyloid TTR (ATTR) Leu55Pro crystal structure is close-to-identical. This packing arrangement is therefore not unique in amyloidogenic mutants of TTR.

  • 19.
    Hörnberg, Andreas
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP).
    Wikström Hultdin, Ulrika
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The effect of iodide and chloride on transthyretin structure and stability2005In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 44, no 26, 9290-9299 p.Article in journal (Other academic)
    Abstract [en]

    Transthyretin amyloid formation occurs through a process of tetramer destabilization and partial unfolding. Small molecules, including the natural ligand thyroxine, stabilize the tetrameric form of the protein, and serve as inhibitors of amyloid formation. Crucial for TTR's ligand-binding properties are its three halogen-binding sites situated at the hormone-binding channel. In this study, we have performed a structural characterization of the binding of two halides, iodide and chloride, to TTR. Chlorides are known to shield charge repulsions at the tetrameric interface of TTR, which improve tetramer stability of the protein. Our study shows that iodides, like chlorides, provide tetramer stabilization in a concentration-dependent manner and at concentrations approximately 15-fold below that of chlorides. To elucidate binding sites of the halides, we took advantage of the anomalous scattering of iodide and used the single-wavelength anomalous dispersion (SAD) method to solve the iodide-bound TTR structure at 1.8 A resolution. The structure of chloride-bound TTR was determined at 1.9 A resolution using difference Fourier techniques. The refined structures showed iodides and chlorides bound at two of the three halogen-binding sites located at the hydrophobic channel. These sites therefore also function as halide-binding sites.

  • 20.
    Iakovleva, Irina
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Begum, Afshan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Brännström, Kristoffer
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Wijsekera, Alexandra
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Nilsson, Lina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Zhang, Jin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Andersson, Patrik L.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sauer-Eriksson, A. Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Tetrabromobisphenol A Is an Efficient Stabilizer of the Transthyretin Tetramer2016In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 4, e0153529Article in journal (Refereed)
    Abstract [en]

    Amyloid formation of the human plasma protein transthyretin (TTR) is associated with several human disorders, including familial amyloidotic polyneuropathy (FAP) and senile systemic amyloidosis. Dissociation of TTR’s native tetrameric assembly is the rate-limiting step in the conversion into amyloid, and this feature presents an avenue for intervention because binding of an appropriate ligand to the thyroxin hormone binding sites of TTR stabilizes the native tetrameric assembly and impairs conversion into amyloid. The desired features for an effective TTR stabilizer include high affinity for TTR, high selectivity in the presence of other proteins, no adverse side effects at the effective concentrations, and a long half-life in the body. In this study we show that the commonly used flame retardant tetrabromobisphenol A (TBBPA) efficiently stabilizes the tetrameric structure of TTR. The X-ray crystal structure shows TBBPA binding in the thyroxine binding pocket with bromines occupying two of the three halogen binding sites. Interestingly, TBBPA binds TTR with an extremely high selectivity in human plasma, and the effect is equal to the recently approved drug tafamidis and better than diflunisal, both of which have shown therapeutic effects against FAP. TBBPA consequently present an interesting scaffold for drug design. Its absorption, metabolism, and potential side-effects are discussed.

  • 21.
    Iakovleva, Irina
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Begum, Afshan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Pokrzywa, Malgorzata
    Walfridsson, Malin
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Sauer-Eriksson, A Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    The flavonoid luteolin, but not luteolin-7-o-glucoside, prevents a transthyretin mediated toxic response2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 5, e0128222Article in journal (Refereed)
    Abstract [en]

    Transthyretin (TTR) is a homotetrameric plasma protein with amyloidogenic properties that has been linked to the development of familial amyloidotic polyneuropathy (FAP), familial amyloidotic cardiomyopathy, and senile systemic amyloidosis. The in vivo role of TTR is associated with transport of thyroxine hormone T4 and retinol-binding protein. Loss of the tetrameric integrity of TTR is a rate-limiting step in the process of TTR amyloid formation, and ligands with the ability to bind within the thyroxin binding site (TBS) can stabilize the tetramer, a feature that is currently used as a therapeutic approach for FAP. Several different flavonoids have recently been identified that impair amyloid formation. The flavonoid luteolin shows therapeutic potential with low incidence of unwanted side effects. In this work, we show that luteolin effectively attenuates the cytotoxic response to TTR in cultured neuronal cells and rescues the phenotype of a Drosophila melanogaster model of FAP. The plant-derived luteolin analogue cynaroside has a glucoside group in position 7 of the flavone A-ring and as opposed to luteolin is unable to stabilize TTR tetramers and thus prevents a cytotoxic effect. We generated high-resolution crystal-structures of both TTR wild type and the amyloidogenic mutant V30M in complex with luteolin. The results show that the A-ring of luteolin, in contrast to what was previously suggested, is buried within the TBS, consequently explaining the lack of activity from cynaroside. The flavonoids represent an interesting group of drug candidates for TTR amyloidosis. The present investigation shows the potential of luteolin as a stabilizer of TTR in vivo. We also show an alternative orientation of luteolin within the TBS which could represent a general mode of binding of flavonoids to TTR and is of importance concerning the future design of tetramer stabilizing drugs.

  • 22.
    Iakovleva, Irina
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Brännström, Kristoffer
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Nilsson, Lina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gharibyan, Anna
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
    Begum, Afshan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Intissar, Anan
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
    Walfridsson, Malin
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Enthalpic Forces Correlate with Selectivity of Transthyretin-Stabilizing Ligands in Human Plasma2015In: Journal of Medicinal Chemistry, ISSN 0022-2623, E-ISSN 1520-4804, Vol. 58, no 16, 6507-6515 p.Article in journal (Refereed)
    Abstract [en]

    The plasma protein transthyretin (TTR) is linked to human amyloidosis. Dissociation of its native tetrameric assembly is a rate-limiting step in the conversion from a native structure into a pathological amyloidogenic fold. Binding of small molecule ligands within the thyroxine binding site of TTR can stabilize the tetrameric integrity and is a potential therapeutic approach. However, through the characterization of nine different tetramer-stabilizing ligands we found that unspecific binding to plasma components might significantly compromise ligand efficacy. Surprisingly the binding strength between a particular ligand and TTR does not correlate well with its selectivity in plasma. However, through analysis of the thermodynamic signature using isothermal titration calorimetry we discovered a better correlation between selectivity and the enthalpic component of the interaction. This is of specific interest in the quest for more efficient TTR stabilizers, but a high selectivity is an almost universally desired feature within drug design and the finding might have wide-ranging implications for drug design.

  • 23.
    Jia, Xueen
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Gharibyan, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Öhman, Anders
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Liu, Yonggang
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Morozova-Roche, Ludmilla A
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Neuroprotective and nootropic drug noopept rescues α-synuclein amyloid cytotoxicity2011In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 414, no 5, 699-712 p.Article in journal (Refereed)
    Abstract [en]

    Parkinson's disease is a common neurodegenerative disorder characterized by α-synuclein (α-Syn)-containing Lewy body formation and selective loss of dopaminergic neurons in the substantia nigra. We have demonstrated the modulating effect of noopept, a novel proline-containing dipeptide drug with nootropic and neuroprotective properties, on α-Syn oligomerization and fibrillation by using thioflavin T fluorescence, far-UV CD, and atomic force microscopy techniques. Noopept does not bind to a sterically specific site in the α-Syn molecule as revealed by heteronuclear two-dimensional NMR analysis, but due to hydrophobic interactions with toxic amyloid oligomers, it prompts their rapid sequestration into larger fibrillar amyloid aggregates. Consequently, this process rescues the cytotoxic effect of amyloid oligomers on neuroblastoma SH-SY5Y cells as demonstrated by using cell viability assays and fluorescent staining of apoptotic and necrotic cells and by assessing the level of intracellular oxidative stress. The mitigating effect of noopept against amyloid oligomeric cytotoxicity may offer additional benefits to the already well-established therapeutic functions of this new pharmaceutical.

  • 24. Kalkunte, Satyan S
    et al.
    Neubeck, Stefan
    Norris, Wendy E
    Cheng, Shi-Bin
    Kostadinov, Stefan
    Vu Hoang, Dang
    Ahmed, Aftab
    von Eggeling, Ferdinand
    Shaikh, Zahir
    Padbury, James
    Berg, Goran
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Markert, Udo R
    Sharma, Surendra
    Transthyretin is dysregulated in preeclampsia, and its native form prevents the onset of disease in a preclinical mouse model2013In: American Journal of Pathology, ISSN 0002-9440, E-ISSN 1525-2191, Vol. 183, no 5, 1425-1436 p.Article in journal (Refereed)
    Abstract [en]

    Preeclampsia is a major pregnancy complication with potential short- and long-term consequences for both mother and fetus. Understanding its pathogenesis and causative biomarkers is likely to yield insights for prediction and treatment. Herein, we provide evidence that transthyretin, a transporter of thyroxine and retinol, is aggregated in preeclampsia and is present at reduced levels in sera of preeclamptic women, as detected by proteomic screen. We demonstrate that transthyretin aggregates form deposits in preeclampsia placental tissue and cause apoptosis. By using in vitro approaches and a humanized mouse model, we provide evidence for a causal link between dysregulated transthyretin and preeclampsia. Native transthyretin inhibits all preeclampsia-like features in the humanized mouse model, including new-onset proteinuria, increased blood pressure, glomerular endotheliosis, and production of anti-angiogenic factors. Our findings suggest that a focus on transthyretin structure and function is a novel strategy to understand and combat preeclampsia.

  • 25.
    Karlsson, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Eneqvist, Therese
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Cys114-linked dimers of transthyretin are compatible with amyloid formation.2005In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 44, no 39, 13063-70 p.Article in journal (Refereed)
    Abstract [en]

    The Tyr114Cys substitution in the human plasma protein transthyretin leads to a particularly aggressive form of familial amyloidotic polyneuropathy. In a previous study we demonstrated that ATTR Tyr114Cys forms intermolecular disulfide bonds, which partly impair fibril formation and result in a more amorphous morphology. Apart from the introduced cysteinyl group in position 114, the native sequence contains one cysteine located at position 10. To deduce the role of intermolecular disulfide bridging in fibril formation we generated and characterized the TTR Cys10Ala/Tyr114Cys double mutant. Our results suggest that an intermolecular cysteine bridge at position 114 enhances the exposure of cysteine 10, thereby facilitating additional intermolecular cysteine assemblies. We also purified a disulfide-linked dimeric form of TTR Cys10Ala/Tyr114Cys, which was recognized by the anti-TTR amyloid-specific monoclonal antibody MAb (39-44). Moreover, this dimeric molecule can form protofibrils indistinguishable from the fibrils formed under reducing conditions, as judged by atomic force microscopy. Assuming that both molecules of the dimer are part of the core of the fibril, the assembly is incompatible with a preserved native or near-native dimeric interphase. Our findings raise the question of whether TTR-amyloid architecture is indeed the result of one highly stringent assembly of structures or if different fibrils may be built from different underlying structures.

  • 26.
    Lindhagen Persson, Malin
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Diez, I
    Vestling, M
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Cytotoxic properties of transthyretin as a function of thermodynamic and kinetic stabilityManuscript (preprint) (Other academic)
  • 27.
    Lindhagen-Persson, Malin
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Brännström, Kristoffer
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Vestling, Monika
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Steinitz, Michael
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Amyloid-β oligomer specificity mediated by the IgM isotype: implications for a specific protective mechanism exerted by endogenous auto-antibodies2010In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 5, no 11, e13928- p.Article in journal (Refereed)
    Abstract [en]

    Background Alzheimers disease (AD) has been strongly linked to an anomalous self-assembly of the amyloid-β peptide (Aβ). The correlation between clinical symptoms of AD and Aβ depositions is, however, weak. Instead small and soluble Aβ oligomers are suggested to exert the major pathological effects. In strong support of this notion, immunological targeting of Aβ oligomers in AD mice-models shows that memory impairments can be restored without affecting the total burden of Aβ deposits. Consequently a specific immunological targeting of Aβ oligomers is of high therapeutic interest.

    Methodology/Principal Findings Previously the generation of conformational-dependent oligomer specific anti-Aβ antibodies has been described. However, to avoid the difficult task of identifying a molecular architecture only present on oligomers, we have focused on a more general approach based on the hypothesis that all oligomers expose multiple identical epitopes and therefore would have an increased binding to a multivalent receptor. Using the polyvalent IgM immunoglobulin we have developed a monoclonal anti-Aβ antibody (OMAB). OMAB only demonstrates a weak interaction with Aβ monomers and dimers having fast on and off-rate kinetics. However, as an effect of avidity, its interaction with Aβ-oligomers results in a strong complex with an exceptionally slow off-rate. Through this mechanism a selectivity towards Aβ oligomers is acquired and OMAB fully inhibits the cytotoxic effect exerted by Aβ(1-42) at highly substoichiometric ratios. Anti-Aβ auto-antibodies of IgM isotype are frequently present in the sera of humans. Through a screen of endogenous anti-Aβ IgM auto-antibodies from a group of healthy individuals we show that all displays a preference for oligomeric Aβ.

    Conclusions/Significance Taken together we provide a simple and general mechanism for targeting of oligomers without the requirement of conformational-dependent epitopes. In addition, our results suggest that IgM anti-Aβ auto-antibodies may exert a more specific protective mechanism in vivo than previously anticipated.

  • 28.
    Lindhagen-Persson, Malin
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Vestling, M
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Reixach, N
    Division of Rheumatology Research, W.M. Keck Autoimmune Disease Center, The Scripps Research Institute, La Jolla, CA, USA.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Formation of cytotoxic transthyretin is not dependent on inter-molecular disulphide bridges commonly found within the amyloid form2008In: Amyloid: Journal of Protein Folding Disorders, ISSN 1350-6129, E-ISSN 1744-2818, Vol. 15, no 4, 240-245 p.Article in journal (Refereed)
    Abstract [en]

    Familial amyloidotic polyneuropathy (FAP) is linked to destabilising point mutations in the human plasma protein transthyretin (TTR). Consistent with similar amyloid disorders, low molecular weight TTR oligomers have been shown to exert the major cytotoxic effect. The amyloid structure of TTR contains non-native inter-molecular disulphide linkages via the cysteine at position 10 (Cys10). Moreover, substitution of Cys10 in a mouse model for TTR-amyloidosis abolishes TTR deposits, indicating an important role of Cys10 in FAP pathogenesis. However, the role of disulphide bridges in TTR cytotoxicity has not been elucidated. By probing Cys10Ser TTR variants to the human neuroblastoma SH-SY5Y cell line, we have addressed this question, and our results clearly show that formation of an inter-molecular disulphide bridge is not a pre-requisite for TTR cytotoxicity. This finding suggests that prevention of inter-molecular TTR disulphide bridges as a therapeutic intervention will not impair the cytotoxic potential of TTR.

  • 29.
    Lundberg, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Westermark, Gunilla T
    Sauer-Eriksson, A Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Stability and fibril formation properties of human and fish transthyretin, and of the Escherichia coli transthyretin-related protein2009In: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 276, no 7, 1999-2011 p.Article in journal (Refereed)
    Abstract [en]

    Human transthyretin (hTTR) is one of several proteins known to cause amyloid disease. Conformational changes in its native structure result in aggregation of the protein, leading to insoluble amyloid fibrils. The transthyretin (TTR)-related proteins comprise a protein family of 5-hydroxyisourate hydrolases with structural similarity to TTR. In this study, we tested the amyloidogenic properties, if any, of sea bream TTR (sbTTR) and Escherichia coli transthyretin-related protein (ecTRP), which share 52% and 30% sequence identity, respectively, with hTTR. We obtained filamentous structures from all three proteins under various conditions, but, interestingly, different structures displayed different tinctorial properties. hTTR and sbTTR formed thin, curved fibrils at low pH (pH 2-3) that bound thioflavin-T (thioflavin-T-positive) but did not stain with Congo Red (CR) (CR-negative). Aggregates formed at the slightly higher pH of 4.0-5.5 had different morphology, displaying predominantly amorphous structures. CR-positive material of hTTR was found in this material, in agreement with previous results. ecTRP remained soluble at pH 2-12 at ambient temperatures. By raising of the temperature, fibril formation could be induced at neutral pH in all three proteins. Most of these temperature-induced fibrils were thicker and straighter than the in vitro fibrils seen at low pH. In other words, the temperature-induced fibrils were more similar to fibrils seen in vivo. The melting temperature of ecTRP was 66.7 degrees C. This is approximately 30 degrees C lower than the melting temperatures of sbTTR and hTTR. Information from the crystal structures was used to identify possible explanations for the reduced thermostability of ecTRP.

  • 30.
    Mikhalyov, I
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Gröbner, Gerhard
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Johansson, Lennart B-Å
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Designed fluorescent probes reveal interactions between Amyloid-β(1-40) Peptides and GM1 Gangliosides in Micelles and Lipid Vesicles2010In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 99, no 5, 1510-1519 p.Article in journal (Refereed)
    Abstract [en]

    A hallmark of the common Alzheimer's disease (AD) is the pathological conversion of its amphiphatic amyloid-beta (Abeta) peptide into neurotoxic aggregates. In AD patients, these aggregates are often found to be tightly associated with neuronal G(M1) ganglioside lipids, suggesting an involvement of G(M1) not only in aggregate formation but also in neurotoxic events. Significant interactions were found between micelles made of newly synthesized fluorescent G(M1) gangliosides labeled in the polar headgroup or the hydrophobic chain and Abeta(1-40) peptide labeled with a BODIPY-FL-C1 fluorophore at positions 12 and 26, respectively. From an analysis of energy transfer between the different fluorescence labels and their location in the molecules, we were able to place the Abeta peptide inside G(M1) micelles, close to the hydrophobic-hydrophilic interface. Large unilamellar vesicles composed of a raftlike G(M1)/bSM/cholesterol lipid composition doped with labeled G(M1) at various positions also interact with labeled Abeta peptide tagged to amino acids 2 or 26. A faster energy transfer was observed from the Abeta peptide to bilayers doped with 581/591-BODIPY-C(11)-G(M1) in the nonpolar part of the lipid compared with 581/591-BODIPY-C(5)-G(M1) residing in the polar headgroup. These data are compatible with a clustering process of G(M1) molecules, an effect that not only increases the Abeta peptide affinity, but also causes a pronounced Abeta peptide penetration deeper into the lipid membrane; all these factors are potentially involved in Abeta peptide aggregate formation due to an altered ganglioside metabolism found in AD patients.

  • 31.
    Nilsson, Lina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Larsson, Andreas
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Swedish Defence Research Agency, CBRN Defence and Security.
    Begum, Afshan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Iakovleva, Irina
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Carlsson, Marcus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kristoffer, Brännström
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Modifications of the 7-Hydroxyl Group of the Transthyretin Ligand Luteolin Provide Mechanistic Insights into Its Binding Properties and High Plasma Specificity2016In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 4, e0153112Article in journal (Refereed)
    Abstract [en]

    Amyloid formation of the plasma protein transthyretin (TTR) has been linked to familial amyloid polyneuropathy and senile systemic amyloidosis. Binding of ligands within its natural hormone binding site can stabilize the tetrameric structure and impair amyloid formation. We have recently shown that the flavonoid luteolin stabilizes TTR in human plasma with a very high selectivity. Luteolin, however, is inactivated in vivo via glucuronidation for which the preferred site is the hydroxy group at position 7 on its aromatic A-ring. We have evaluated the properties of two luteolin variants in which the 7-hydroxy group has been exchanged for a chlorine (7-Cl-Lut) or a methoxy group (7-MeO-Lut). Using an in vitro model, based on human liver microsomes, we verified that these modifications increase the persistence of the drug. Crystal structure determinations show that 7-Cl-Lut binds similarly to luteolin. The larger MeO substituent cannot be accommodated within the same space as the chlorine or hydroxy group and as a result 7-MeO-Lut binds in the opposite direction with the methoxy group in position 7 facing the solvent. Both 7-Cl-Lut and 7-MeO-Lut qualify as high-affinity binders, but in contrast to luteolin, they display a highly non-specific binding to other plasma components. The binding of the two conformations and the key-interactions to TTR are discussed in detail. Taken together, these results show a proof-of-concept that the persistence of luteolin towards enzymatic modification can be increased. We reveal two alternative high-affinity binding modes of luteolin to TTR and that modification in position 7 is restricted only to small substituents if the original orientation of luteolin should be preserved. In addition, the present work provides a general and convenient method to evaluate the efficacy of TTR-stabilizing drugs under conditions similar to an in vivo environment.

  • 32.
    Olofsson, Anders
    et al.
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Borowik, Tomasz
    Gröbner, Gerhard
    Faculty of Science and Technology, Chemistry.
    Sauer-Eriksson, Elisabeth
    Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Negatively Charged Phospholipid Membranes Induce Amyloid Formation of Medin via an alpha-Helical Intermediate2007In: Journal of Molecular Biology, ISSN 0022-2836, Vol. 374, no 1, 186-94 p.Article in journal (Refereed)
    Abstract [en]

    Medin, a recently discovered 5.5 kDa peptide, is associated with amyloid deposits in the medial layer of human arteries and the prevalence is nearly 100% within individuals above 50 years. Presently, not much is known about its biochemical and biophysical properties or its pathway from soluble peptide to insoluble amyloid. Here we have characterized the behavior of medin in the presence of lipid membranes, using circular dichroism, isothermal titration calorimetry, differential scanning calorimetry, size exclusion chromatography, and atomic force microscopy (AFM). Medin was shown to exist as a monomer in solution with a predominantly random-coil structure. It binds lipid vesicles that have either a neutral or a negative surface potential. Upon association to membranes containing acidic lipids, it undergoes an electrostatically driven conformational change towards a mainly α-helical state. Prolonged incubation converts medin from an α-helical structure into an amyloid β-sheet fibrillar state as confirmed by AFM. Based on these findings, we propose a mechanism of medin-amyloid formation where medin electrostatically associates in its monomeric form to biological interfaces displaying a negative potential. This process both increases the local peptide concentration and induces an aggregation-prone α-helical fold.

  • 33.
    Olofsson, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Ippel, Johannes H
    Wijmenga, Sybren S
    Lundgren, Erik
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Ohman, Anders
    Probing solvent accessibility of transthyretin amyloid by solution NMR spectroscopy.2004In: J Biol Chem, ISSN 0021-9258, Vol. 279, no 7, 5699-707 p.Article in journal (Refereed)
    Abstract [en]

    The human plasma protein transthyretin (TTR) may form fibrillar protein deposits that are associated with both inherited and idiopathic amyloidosis. The present study utilizes solution nuclear magnetic resonance spectroscopy, in combination with hydrogen/deuterium exchange, to determine residue-specific solvent protection factors within the fibrillar structure of the clinically relevant variant, TTRY114C. This novel approach suggests a fibril core comprised of the six beta-strands, A-B-E-F-G-H, which retains a native-like conformation. Strands C and D are dislocated from their native edge region and become solvent-exposed, leaving a new interface involving strands A and B open for intermolecular interactions. Our results further support a native-like intermolecular association between strands F-F' and H-H' with a prolongation of these beta-strands and, interestingly, with a possible shift in beta-strand register of the subunit assembly. This finding may explain previous observations of a monomeric intermediate preceding fibril formation. A structural model based on our results is presented.

  • 34.
    Olofsson, Anders
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Lindhagen Persson, Malin
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Vestling, Monika
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Öhman, Anders
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Quenched hydrogen/deuterium exchange NMR characterization of amyloid-β peptide aggregates formed in the presence of Cu2+ or Zn2+2009In: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 276, no 15, 4051-4060 p.Article in journal (Refereed)
    Abstract [en]

    Alzheimer's disease, a neurodegenerative disorder causing synaptic impairment and neuronal cell death, is strongly correlated with aggregation of the amyloid-β peptide (Aβ). Divalent metal ions such as Cu2+ and Zn2+ are known to significantly affect the rate of aggregation and morphology of Aβ assemblies in vitro and are also found at elevated levels within cerebral plaques in vivo. The present investigation characterized the architecture of the aggregated forms of Aβ(1–40) and Aβ(1–42) in the presence or absence of either Cu2+ or Zn2+ using quenched hydrogen/deuterium exchange combined with solution NMR spectroscopy. The NMR analyses provide a quantitative and residue-specific structural characterization of metal-induced Aβ aggregates, showing that both the peptide sequence and the type of metal ion exert an impact on the final architecture. Common features among the metal-complexed peptide aggregates are two solvent-protected regions with an intervening minimum centered at Asn27, and a solvent-accessible N-terminal region, Asp1–Lys16. Our results suggest that Aβ in complex with either Cu2+ or Zn2+ can attain an aggregation-prone β-strand–turn–β-strand motif, similar to the motif found in fibrils, but where the metal binding to the N-terminal region guides the peptide into an assembly distinctly different from the fibril form.

  • 35.
    Olofsson, Anders
    et al.
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Lindhagen-Persson, Malin
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Öhman, Anders
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Amide solvent protection analysis demonstrates that amyloid-beta(1-40) and amyloid-beta(1-42) form different fibrillar structures under identical conditions.2007In: Biochem J, ISSN 1470-8728, Vol. 404, no 1, 63-70 p.Article in journal (Refereed)
    Abstract [en]

    AD (Alzheimer's disease) is a neurodegenerative disorder characterized by self-assembly and amyloid formation of the 39–43 residue long Ab (amyloid-b)-peptide. The most abundant species, Ab(1–40) and Ab(1–42), are both present within senile plaques, but Ab(1–42) peptides are considerably more prone to self-aggregation and are also essential for the development of AD. To understand the molecular and pathological mechanisms behind AD, a detailed knowledge of the amyloid structures of Ab-peptides is vital. In the present study we have used quenched hydrogen/deuterium-exchange NMR experiments to probe the structure of Ab(1–40) fibrils. The fibrils were prepared and analysed identically as in our previous study on Ab(1–42) fibrils, allowing a direct comparison of the two fibrillar structures. The solvent protection pattern of Ab(1–40) fibrils revealed two well-protected regions, consistent with a structural arrangement of two b-strands connected with a bend. This protection pattern partly resembles the pattern found in Ab(1–42) fibrils, but the Ab(1–40) fibrils display a significantly increased protection for the N-terminal residues Phe4–His14, suggesting that additional secondary structure is formed in this region. In contrast, the C-terminal residues Gly37–Val40 show a reduced protection that suggests a loss of secondary structure in this region and an altered filament assembly. The differences between the present study and other similar investigations suggest that subtle variations in fibril-preparation conditions may significantly affect the fibrillar architecture.

  • 36.
    Olofsson, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP).
    Sauer-Eriksson, A Elisabeth
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP).
    Öhman, Anders
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP).
    Amyloid fibril dynamics revealed by combined hydrogen/deuterium exchange and nuclear magnetic resonance2009In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 385, no 2, 374-376 p.Article in journal (Refereed)
    Abstract [en]

    A general method to explore the dynamic nature of amyloid fibrils is described, combining hydrogen/deuterium exchange and nuclear magnetic resonance spectroscopy to determine the exchange rates of individual amide protons within an amyloid fibril. Our method was applied to fibrils formed by the amyloid-beta(1-40) peptide, the major protein component of amyloid plaques in Alzheimer's disease. The fastest exchange rates were detected among the first 14 residues of the peptide, a stretch known to be poorly structured within the fibril. Considerably slower exchange rates were observed in the remainder of the peptide within the beta-strand-turn-beta-strand motif that constitutes the fibrillar core.

  • 37.
    Olofsson, Anders
    et al.
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Öhman, Anders
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The solvent protection of alzheimer amyloid-beta-(1-42) fibrils as determined by solution NMR spectroscopy.2006In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 281, no 1, 477-83 p.Article in journal (Refereed)
    Abstract [en]

    Alzheimer disease is a neurodegenerative disorder that is tightly linked to the self-assembly and amyloid formation of the 39-43-residue-long amyloid-beta (Abeta) peptide. Considerable evidence suggests a correlation between Alzheimer disease development and the longer variants of the peptide, Abeta-(1-42/43). Currently, a molecular understanding for this behavior is lacking. In the present study, we have investigated the hydrogen/deuterium exchange of Abeta-(1-42) fibrils under physiological conditions, using solution NMR spectroscopy. The obtained residue-specific and quantitative map of the solvent protection within the Abeta-(1-42) fibril shows that there are two protected core regions, Glu11-Gly25 and Lys28-Ala42, and that the residues in between, Ser26 and Asn27, as well as those in the N terminus, Asp1-Tyr10, are solvent-accessible. This result reveals considerable discrepancies when compared with a previous investigation on Abeta-(1-40) fibrils and suggests that the additional residues in Abeta-(1-42), Ile41 and Ala42, significantly increase the solvent protection and stability of the C-terminal region Lys28-Ala42. Consequently, our findings provide a molecular explanation for the increased amyloidogenicity and toxicity of Abeta-(1-42) compared with shorter Abeta variants found in vivo.

  • 38. Ouberai, Myriam
    et al.
    Brännström, Kristoffer
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Vestling, Monika
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Dumy, Pascal
    Chierici, Sabine
    Garcia, Julian
    Clicked tacrine conjugates as acetylcholinesterase and β-amyloid directed compounds2011In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 9, no 4, 1140-1147 p.Article in journal (Refereed)
    Abstract [en]

    The multifaceted nature of Alzheimer's disease (AD) has led to the development of multi-targeted compounds based on the classical AD drug, tacrine, first known to inhibit the acetylcholine-degrading enzyme acetylcholinesterase (AChE). In the present work, we explore the potentiality of multimers of tacrine in this field. The synthesis using the so-called "click chemistry" and the in vitro study of the conjugates are described. Two or four copies of the tacrine molecule are "clicked" on a constrained cyclopeptide template proven to be a convenient tool for multimeric presentation. The multimers significantly inhibit self-induced amyloid fibril formation from Aβ(40) at low inhibitor to Aβ molar ratios at which the tacrine monomer is fully inactive (Thioflavin T assays and AFM observation). Moreover, they have the capacity to bind to Aβ(40) fibrils (SPR assays) while retaining the AChE inhibitory activity of the parent tacrine.

  • 39. Treusch, Sebastian
    et al.
    Hamamichi, Shusei
    Goodman, Jessica L
    Matlack, Kent ES
    Chung, Chee Yeun
    Baru, Valeriya
    Shulman, Joshua M
    Parrado, Antonio
    Bevis, Brooke J
    Valastyan, Julie S
    Han, Haesun
    Lindhagen-Persson, Malin
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Reiman, Eric M
    Evans, Denis A
    Bennett, David A
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Dejager, Philip L
    Tanzi, Rudolph E
    Caldwell, Kim A
    Caldwell, Guy A
    Lindquist, Susan
    Functional links between Aβ toxicity, endocytic trafficking, and Alzheimer's disease risk factors in yeast2011In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 334, no 6060, 1241-1245 p.Article in journal (Refereed)
    Abstract [en]

    Aβ (beta amyloid peptide) is an important contributor to Alzheimer's disease (AD). We modeled Aβ toxicity in yeast by directing the peptide to the secretory pathway. A genome-wide screen for toxicity modifiers identified the yeast homolog of phosphatidylinositol binding clathrin assembly protein (PICALM) and other endocytic factors connected to AD whose relationship to Aβ was previously unknown. The factors identified in yeast modified Aβ toxicity in glutamatergic neurons of Caenorhabditis elegans and in primary rat cortical neurons. In yeast, Aβ impaired the endocytic trafficking of a plasma membrane receptor, which was ameliorated by endocytic pathway factors identified in the yeast screen. Thus, links between Aβ, endocytosis, and human AD risk factors can be ascertained using yeast as a model system.

  • 40.
    Wang, Chao
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Klechikov, Alexey G.
    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.
    Wärmländer, Sebastian K. T. S.
    Jarvet, Jüri
    Zhao, Lina
    Jia, Xueen
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Shankar, S. K.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Brännström, Thomas
    Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
    Mu, Yuguang
    Gräslund, Astrid
    Morozova-Roche, Ludmilla A.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    The role of pro-inflammatory S100A9 in Alzheimer's disease amyloid-neuroinflammatory cascade2014In: Acta Neuropathologica, ISSN 0001-6322, E-ISSN 1432-0533, Vol. 127, no 4, 507-522 p.Article in journal (Refereed)
    Abstract [en]

    Pro-inflammatory S100A9 protein is increasingly recognized as an important contributor to inflammation-related neurodegeneration. Here, we provide insights into S100A9 specific mechanisms of action in Alzheimer's disease (AD). Due to its inherent amyloidogenicity S100A9 contributes to amyloid plaque formation together with A beta. In traumatic brain injury (TBI) S100A9 itself rapidly forms amyloid plaques, which were reactive with oligomer-specific antibodies, but not with A beta and amyloid fibrillar antibodies. They may serve as precursor-plaques for AD, implicating TBI as an AD risk factor. S100A9 was observed in some hippocampal and cortical neurons in TBI, AD and non-demented aging. In vitro S100A9 forms neurotoxic linear and annular amyloids resembling A beta protofilaments. S100A9 amyloid cytotoxicity and native S100A9 pro-inflammatory signaling can be mitigated by its co-aggregation with A beta, which results in a variety of micron-scale amyloid complexes. NMR and molecular docking demonstrated transient interactions between native S100A9 and A beta. Thus, abundantly present in AD brain pro-inflammatory S100A9, possessing also intrinsic amyloidogenic properties and ability to modulate A beta aggregation, can serve as a link between the AD amyloid and neuroinflammatory cascades and as a prospective therapeutic target.

  • 41.
    Åberg, Veronica
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Norman, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Chorell, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Westermark, Andreas
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Medicine).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Umeå Centre for Molecular Pathogenesis (UCMP) (Faculty of Science and Technology).
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Microwave-assisted decarboxylation of bicyclic 2-pyridone scaffolds and identification of A beta-peptide aggregation inhibitors2005In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 3, no 15, 2817-2823 p.Article in journal (Refereed)
    Abstract [en]

    A reagent-free microwave-assisted decarboxylation procedure for carboxylic acid functionalized bicyclic 2-pyridones has been developed. This new method, based on microwave heating at 220 degrees C for 600 seconds in N-methyl pyrrolidone (NMP), proved to be practical and very efficient, resulting in decarboxylated 2-pyridones in near-quantitative yields. The decarboxylated products and the intermediate 2-pyridones in the form of carboxylic acid methyl esters and carboxylic acids were screened for their effect on A beta-peptide aggregation. Two out of the 21 2-pyridones described in this study inhibited amyloid formation of the Alzheimer A beta(1-40) peptide. The effect was seen even at a 4 : 1 ratio of 2-pyridone and monomeric A beta-peptide.

  • 42.
    Ådén, Jörgen
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Weise, Christoph
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Brännström, Kristoffer
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Wolf-Watz, Magnus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Structural topology and activation of an initial adenylate kinase-substrate complex2013In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 52, no 6, 1055-1061 p.Article in journal (Refereed)
    Abstract [en]

    Enzymatic activity is ultimately defined by the structure, chemistry and dynamics of the Michaelis complex. There exist a large number of experimentally determined structures between enzymes and substrates or substrate analogues or inhibitors. However, transient, short-lived encounter and equilibrium structures also play fundamental roles during enzymatic reaction cycles. Such structures are inherently difficult to study with conventional experimental techniques. The enzyme adenylate kinase undergoes major conformational rearrangements in response to binding of its substrates ATP and AMP. ATP is sandwiched between two binding surfaces in the closed and active enzyme conformation. Thus, ade-nylate kinase harbors two spatially distant surfaces in the substrate free open conformation of which one is responsible for the initial interaction with ATP. Here, we have performed primarily nuclear magnetic resonance experiments on Escherichia coli adenylate kinase (AKeco) variants that enabled identification of the site responsible for the initial ATP interaction. This allowed a characterization of the structural topology of an initial equilibrium complex between AKeco and ATP. Based on the results it is suggested that the ATP binding mechanism to AKeco is a mixture between "induced fit" and "conformational selection" models. It is shown that ATP is activated in the initial enzyme bound complex since it displays an appreciable rate of non-productive ATP hydrolysis. In summary our results provide novel structural and functional insights into adenylate kinase catalysis.

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