Regulation of Helicobacter pylori urease and acetone decarboxylase genes by nitric oxide and the CrdRS two-component system. Helicobacter pylori

Helicobacter pylori colonizes the human gastric mucosa and causes various gastroduodenal diseases, including peptic ulceration and gastric cancer. Colonization requires the actions of Two-Component Systems (TCSs) to sense and respond to changes in the host environment. In this study, we evaluated gene regulation mediated by the CrdRS TCS. Few studies have evaluated this TCS, leaving the signal(s) yet to be exhaustively determined and a need for a more complete regulon to be delineated. We performed RNA sequencing (RNA-Seq) on three isogenic H. pylori 26695 mutants: a control, the deletion of the sensory histidine kinase, DcrdS, and the deletion of the response regulator, DcrdR. Comparison of the RNA-Seq results from these mutants established a 40 gene regulon putatively controlled by the CrdRS TCS. Quantitative real-time PCR (RT-qPCR) was used to validate 7 of 11 putative regulon members selected for analysis. We further investigated 6 confirmed CrdRS regulon genes, using phospho-incompetent H. pylori 26695 CrdR D53A and CrdS H173A mutants. These experiments further confirmed the role of CrdRS in regulation of urease, acetone carboxylase, hofD and HP1440. Expression of these CrdRS regulon genes was also evaluated under 10 uM nitric oxide (NO) conditions. This revealed that ureA, acxA, hofD, and HP1440 expression is affected by NO in a CrdRS-dependent manner. Importantly, three of these genes (ureA, acxA, hofD) are known to play important roles in H. pylori colonization of the stomach.