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.