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The Helicobacter pylori sialic acid binding adhesin SabA is regulated via a network of two-component systems
Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics. (Anna Arnqvist)
Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics. (Anna Arnqvist)
Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics. (Anders Olofsson)
(Anna Arnqvist)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The acid-responsive signaling system ArsRS plays a key role in regulating factors important for survival in acidic conditions during infection of the human stomach by Helicobacter pylori. In addition, ArsRS was suggested to control the disease-associated attachment protein SabA, however, mechanistic data is still lacking. We show that the repressing effect of the ArsRS system on SabA expression occurs both at acidic and neutral conditions and is mediated at the transcriptional level. Purified His6-ArsR binds PsabA DNA at several sites, with varying affinity and independent of phosphorylation status and H. pylori strains showed unique cognate PsabA sequences to tweak the ArsR binding ability, resulting in strain-dependent repression of SabA expression. By site-directed mutagenesis we reveal key amino acids for the binding activity of ArsR. Finally, we show that that ArsR binds to A/T-rich DNA as dimers or larger multimers, suggesting that ArsR has affinity for DNA structures rather than to a specific promoter DNA sequence. SabA expression is further influenced by the FlgRS and CrdRS two-component systems, illustrating a complicated crosstalk among regulatory networks in H. pylori.

Keyword [en]
Helicobacter pylori
National Category
Microbiology in the medical area
Research subject
Medical Biochemistry
Identifiers
URN: urn:nbn:se:umu:diva-120293OAI: oai:DiVA.org:umu-120293DiVA: diva2:928083
Funder
Swedish Research Council, K2009-56X-20037-04-3 (VR/NT)Swedish Cancer Society, 09 0641The Kempe Foundations
Available from: 2016-05-14 Created: 2016-05-14 Last updated: 2016-05-18
In thesis
1. Helicobacter pylori: molecular insights into regulation of adhesion properties
Open this publication in new window or tab >>Helicobacter pylori: molecular insights into regulation of adhesion properties
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Helicobacter pylori infects the human stomach and triggers an inflammatory response that damages the gastric tissue. This host-pathogen interplay has dire consequences as up to 20 % of infected individuals develop peptic ulcer disease or gastric cancer. Given that half of the world’s population is infected, the number of afflicted humans is staggering and also tells that H. pylori is extremely efficient in spreading and maintaining infection. To enable persistent infection many factors play a role, but one important feature of H. pylori is its impressive ability to adhere to the slimy gastric mucus layer and the underlying epithelial cells. This occurs mainly via the BabA and SabA proteins that bind ABO/Leb- and sLex/sLea-antigens. I have in my thesis studied how these two proteins are utilized and regulated.

H. pylori transcription is in part controlled by two-component systems (TCSs) that use a sensor protein and a DNA-binding response regulator. We have studied how these systems control sabA and to some extent babA and indeed found a better map of how sabA and babA is regulated at the transcriptional level. We also found that variations in a polynucleotide T-tract located in the sabA promotor could fine-tune SabA expression/ sLex-binding. Thus we have exposed how strict regulation by TCSs combined with stochastic processes together shapes attachment in the bacterial population.

As the buffering mucus layer is constantly exfoliated, placing H. pylori in bactericidal acid, we hypothesized that low pH should abrogate adhesion. SabA expression was indeed repressed in low pH, however BabA expression remained unaffected. The BabA/ Leb-binding was instead directly reversibly hampered by low pH and the degree of pH sensitivity was strain dependent and encoded in the BabA sequence. We believe that the pH dependent loss of binding is one key factor H. pylori utilizes to maintain persistent infection.

BabA is divided in generalists that bind ABO antigens and specialists that only bind blood group (bg) O. We co-crystalized BabA bound to these receptors and established the structural basis for generalist vs. specialist discrimination. We furthermore found a disulfide-clasped loop (CL2) in the center of the binding domain crucial for binding. Breaking CL2 with N-Acetylcysteine (NAC) disrupted binding and H. pylori infection mice experiments revealed inflammatory reduction upon NAC-treatment.

In sum, I have in my thesis dissected how H. pylori controls its adhesive abilities and how intrinsic properties in binding can be exploited for therapeutic purposes.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2016. 53 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1813
Keyword
Helicobacter pylori
National Category
Microbiology in the medical area
Research subject
Medical Biochemistry
Identifiers
urn:nbn:se:umu:diva-120466 (URN)978-91-7601-493-6 (ISBN)
Public defence
2016-06-09, N300, Umeå universitet, Naturvetarhuset, Umeå, 09:00 (English)
Opponent
Supervisors
Funder
The Kempe Foundations
Available from: 2016-05-19 Created: 2016-05-16 Last updated: 2016-05-26Bibliographically approved

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Åberg, AnnaGideonsson, PärBrännström, KristofferArnqvist, Anna
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