Thioloxidoreductase HP0231 of Helicobacter pylori impacts HopQ-dependent CagA translocation

Abstract

Thioloxidoreductase HP0231 of Helicobacter pylori plays essential roles in gastric colonization and related gastric pathology. Comparative proteomics and analysis of complexes between HP0231 and its protein substrates suggested that several Hop proteins are its targets. HP0231 is a dimeric oxidoreductase that functions in an oxidizing Dsb (disulfide bonds) pathway of H. pylori. H. pylori HopQ possesses six cysteine residues, which generate three consecutive disulfide bridges. Comparison of the redox state of HopQ in wild-type cells to that in hp0231-mutated cells clearly indicated that HopQ is a substrate of HP0231. HopQ binds CEACAM1, 3, 5 and 6 (carcinoembryonic antigen-related cell adhesion molecules). This interaction enables T4SS-mediated translocation of CagA into host cells and induces host signaling. Site directed mutagenesis of HopQ (changing cysteine residues into serine) and analysis of the functioning of HopQ variants showed that HP0231 influences the delivery of CagA into host cells, in part through its impact on HopQ redox state. Introduction of a C382S mutation into HopQ significantly affects its reaction with CEACAM receptors, which disturbs T4SS functioning and CagA delivery. An additional effect of HP0231 on other adhesins and their redox state, resulting in their functional impairment, cannot be excluded.

Cysteine Residues in Helicobacter pylori Adhesin HopQ Are Required for CEACAM–HopQ Interaction and Subsequent CagA Translocation

“…However, our results indicate that this is independent of HopQ, since the lack of HP0231 did not impair HopQ-CEACAM1 interaction, and thus the binding of H. pylori to epithelial cells. This finding is in contrast to a recent description of the interaction of HP0231 with HopQ, where HP0231 was thought to directly interact with and influence HopQ binding and subsequent CagA translocation [23]. The discrepancy in strains used or assay formats could explain the contrasting findings we observed, though in our assays we found that ∆hp0231 mutants in multiple strain backgrounds had no effect on HopQ-mediated binding in several assay settings.…”

“…In this study, we demonstrate that the disulfide bond between residues C103 and C132, present in cysteine-clasped loop CL1, is required for CEACAM1 engagement by HopQ, whereas the disulfide bonds present in CL2 and 3are not. This is in contrast to what was reported in a recent paper [23], though consistent with our published co-complex structure [5]. As CL3 is located distant from the binding interface, no negative effect upon disruption of its disulfide is expected.…”

“…Two other Dsb-like proteins were reported in H. pylori-HP0595 (HpDsbI), which has been described as impacting HP0231 reoxidation [13], and HP0377, a DsbC-like protein which has been described as depending on HP0231 for redox homeostasis [14]. A possible link between HP0595 and HopQ function was ruled out, since HP0595-deficient bacteria were still able to translocate CagA into host cells [23]. HP0377, like HP0231, is localized in the periplasm, making this enzyme the most likely candidate for direct interaction with HopQ.…”

Helicobacter pylori Virulence Factors Exploiting Gastric Colonization and its Pathogenicity

“…The recent studies highlighted that the interaction between HopQ and CEACAM contributes to gastric colonization [114] and facilitates translocation of the CagA protein into the gastric epithelium to induce pathogenicity [114,116,121,122]. A recent study showed that the interaction between HopQ and CEACAM plays a significant role in inhibiting immune cell activities [40].…”

Helicobacter pylori treatment in the post-antibiotics era—searching for new drug targets

“…An H. pylori strain lacking the major Dsb oxidoreductase, encoded by hp0231, is deficient in CagA translocation into host epithelial cells as Hp0231, among other activities, influences the structure of HopQ, an outer membrane protein that mediates pathogen adhesion to epithelial cells by interaction with CECAM receptors (Javaheri et al 2016;Königer et al 2016). Lack of Hp0231 abolishes the H. pylori-induced IL-8 production and the development of the hummingbird phenotype in AGS cells (Zhong et al 2016;Grzeszczuk et al 2018). Moreover, an H. pylori hp0231-deficient strain was not able to colonize the gastric mucosa of mice.…”