Helicobacter pylori CagL activates ADAM17 to induce repression of the gastric H, K-ATPase alpha subunit

Gastroenterology. 2010 Jul;139(1):239-48. doi: 10.1053/j.gastro.2010.03.036. Epub 2010 Mar 18.

Abstract

Background & aims: Infection with Helicobacter pylori represses expression of the gastric H, K-adenosine triphosphatase alpha-subunit (HKalpha), which could contribute to transient hypochlorhydria. CagL, a pilus protein component of the H pylori type IV secretion system, binds to the integrin alpha(5)beta1 to mediate translocation of virulence factors into the host cell and initiate signaling. alpha(5)beta1 binds a disintegrin and metalloprotease (ADAM) 17, a metalloenzyme that catalyzes ectodomain shedding of receptor tyrosine kinase ligands. We investigated whether H pylori-induced repression of HKalpha is mediated by CagL activation of ADAM17 and release of heparin-binding epidermal growth factor (HB-EGF).

Methods: HKalpha promoter and ADAM17 activity were measured in AGS gastric epithelial cells transfected with HKalpha promoter-reporter constructs or ADAM17-specific small interfering RNAs and infected with H pylori. HB-EGF secretion was measured by enzyme-linked immunosorbent assay analysis, and ADAM17 interaction with integrins was investigated by coimmunoprecipitation analyses.

Results: Infection of AGS cells with wild-type H pylori or an H pylori cagL-deficient isogenic mutant that also contained a wild-type version of cagL (P12DeltacagL/cagL) repressed HKalpha promoter-Luc reporter activity and stimulated ADAM17 activity. Both responses were inhibited by point mutations in the nuclear factor-kappaB binding site of HKalpha or by infection with P12DeltacagL. Small interfering RNA-mediated silencing of ADAM17 in AGS cells inhibited the repression of wild-type HKalpha promoter and reduced ADAM17 activity and HB-EGF production, compared to controls. Coimmunoprecipitation studies of AGS lysates showed that wild-type H pylori disrupted ADAM17-alpha5beta1 complexes.

Conclusions: During acute H pylori infection, CagL dissociates ADAM17 from the integrin alpha(5)beta1 and activates ADAM17-dependent, nuclear factor-kappaB-mediated repression of HKalpha. This might contribute to transient hypochlorhydria in patients with H pylori infection.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADAM Proteins / physiology*
  • ADAM17 Protein
  • Enzyme Repression
  • Helicobacter pylori / physiology*
  • Heparin-binding EGF-like Growth Factor
  • Humans
  • Integrin beta1 / metabolism
  • Intercellular Signaling Peptides and Proteins / metabolism
  • Oligopeptides / physiology
  • Promoter Regions, Genetic
  • Sodium-Potassium-Exchanging ATPase / biosynthesis
  • Sodium-Potassium-Exchanging ATPase / genetics*
  • Stomach / enzymology*

Substances

  • HBEGF protein, human
  • Heparin-binding EGF-like Growth Factor
  • Integrin beta1
  • Intercellular Signaling Peptides and Proteins
  • Oligopeptides
  • arginyl-glycyl-aspartic acid
  • ADAM Proteins
  • ADAM17 Protein
  • ADAM17 protein, human
  • ATP1A1 protein, human
  • Sodium-Potassium-Exchanging ATPase