Helicobacter pylori infection activates the HIF-1α/ALS2/Rab5 signaling axis in gastric cells.

Helicobacter pylori (H. pylori) infection has been associated with gastric carcinogenesis by activating different signaling pathways. In gastric cancer cells, H. pylori promotes the stabilization of HIF-1α (hypoxia inducible factor 1α), a transcription factor associated with the expression of several genes involved in cellular adaptation. We previously showed that HIF-1α regulates endosomal trafficking via activation of the small GTPase Rab5, which in turn activates downstream signaling pathways involved in tumor progression, such as the WNT/β-catenin pathway. Here, we explored the possibility that H. pylori infection activates this signaling mechanism in gastric cells, uncovering the guanine exchange factor ALS2 as a novel target induced by this bacterium. H. pylori infection increased ALS2 levels in a HIF-1α-dependent manner, leading to Rab5 activation during bacterial infection, thereby allowing sustained β-catenin signaling via endosomal sequestration of GSK3β. Rab5-GTP pulldown assays in MKN74 and AGS gastric cancer cells showed that bacterial infection induced Rab5 activation, which depended on HIF-1α stabilization, as indicated by siRNA and pharmacological inhibition approaches. Interestingly, we found that H. pylori infection upregulated the Rab5 activator ALS2 at both the mRNA and protein levels in a HIF-1α-dependent manner. These observations were further confirmed in patient-derived tumor organoids, as bacterial infection recapitulated ALS2 induction ex vivo. Moreover, ALS2 was required for H. pylori-induced Rab5 activation, early endosome enlargement, and downstream β-catenin signaling, as shown by shRNA-mediated knockdown of endogenous ALS2. Taken together, these observations uncover a novel pathway induced by H. pylori in gastric cells, which involves the HIF-1α/ALS2/Rab5/β-catenin signaling axis.