Helicobacter pylori-induced posttranscriptional regulation of H-K-ATPase α-subunit gene expression by miRNA.

Helicobacter pylori-induced posttranscriptional regulation of H-K-ATPase alpha-subunit gene expression by miRNA. Am J Physiol Gastrointest Liver Physiol 306: G606-G613 2014. First published February 6 2014 doi: 10.1152/ ajpgi. 00333.2013.-Acute Helicobacter pylori infection of gastric epithelial cells induces CagA oncoproteinand peptidoglycan (SLT)-dependent mobilization of NF-kB p50 homodimers that bind to H-K-ATPase alpha-subunit (HK alpha) promoter and repress HK alpha gene transcription. This process may facilitate gastric H. pylori colonization by induction of transient hypochlorhydria. We hypothesized that H. pylori also regulates HK alpha expression posttranscriptionally by miRNA interaction with HK alpha mRNA. In silico analysis of the HK alpha 3' untranslated region (UTR) identified miR-1289 as a highly conserved putative HK alpha -regulatory miRNA. H.pylori infection of AGS cells transfected with HK alpha 3' UTR-Luc reporter construct repressed luciferase activity by 70% whereas triangle cagA or triangle slt H. pylori infections partially abrogated repression. Transfection of AGS cells expressing HK alpha 3' UTR-Luc construct with an oligoribonucleotide mimetic of miR-1289 induced maximal repression (54%) of UTR activity within 30 min UTR activity was unchanged by nontargeting siRNA transfection. Gastric biopsies from patients infected with cagA(+) H. pylori showed a significant increase in miR-1289 expression compared with uninfected patients or those infected with cagA H. pylori. Finally miR-1289 expression was necessary and sufficient to attenuate biopsy HK alpha protein expression in the absence of infection. Taken together these data indicate that miR-1289 is upregulated by H. pylori in a CagA-and SLT-dependent manner and targets HK alpha 3' UTR affecting HK alpha mRNA translation. The sensitivity of HK alpha mRNA 3' UTR to binding of miR-1289 identifies a novel regulatory mechanism of gastric acid secretion and offers new insights into mechanisms underlying transient H. pyloriinduced hypochlorhydria.