M. Gooz et al., Inhibition of human gastric H+-K+-ATPase alpha-subunit gene expression by Helicobacter pylori, AM J P-GAST, 278(6), 2000, pp. G981-G991
Citations number
55
Categorie Soggetti
da verificare
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY
Clinical studies and in vitro data from isolated parietal cells suggest tha
t acute Helicobacter pylori infection inhibits acid secretion. Gastric acid
ification is mediated by H+-K+-ATPase, an integral protein of parietal cell
apical membranes. To test the hypothesis that H. pylori downregulates H+-K
+-ATPase alpha-subunit (HK alpha) gene expression and to identify potential
intracellular signaling pathways mediating such regulation, we transfected
human gastric adenocarcinoma (AGS) cells with human and rat HK alpha 5'-fl
anking DNA fused to a luciferase reporter plasmid. Histamine caused dose-de
pendent, cimetidine-sensitive (10(-4) M) increases in cAMP, free intracellu
lar Ca2+, and HK alpha promoter activation in AGS cells. H. pylori infectio
n of transfected AGS cells dose dependently inhibited basal and histamine-s
timulated HK alpha promoter activity by 80% and 66%, respectively. H. pylor
i dose dependently inhibited phorbol myristate acetate-induced (10(-7) M) a
nd staurosporine( 10(-7) M) and calphostin C-sensitive (5 x 10(-8) M) activ
ation of HK alpha promoter. Also, H. pylori inhibited epidermal growth fact
or (EGF) (10(-8) M), genistein-sensitive (5 x 10(-5) M) activation of HK al
pha promoter, reducing activity to 60% of basal level. These data suggest t
hat H. pylori inhibits HK alpha gene expression via intracellular pathways
involving protein kinases A and C and protein tyrosine kinase, AGS cells ha
ve functional histamine H-2 and EGF receptors, and transiently transfected
AGS cells are a useful model for studying regulation of HK alpha gene expre
ssion.