Augmented recruitment of host Grb2 by Helicobacter pylori tyrosine phosphorylated CagA EPIYA-D motif promotes cellular oncogenic transformation.

CagA, one of the key virulence factors of Helicobacter pylori, plays a significant role in H. pylori-associated gastric cancer by actively participating in neoplastic transformation. Among CagA variants, East Asian type CagA (CagAE) bearing the EPIYA-D motif exhibits a higher risk than the Western-type (CagAW) with EPIYA-C motifs. In this study, we investigated the interactions of CagAE and CagAW and host intracellular Grb2 and found a pronouncedly greater recruitment of Grb2 by CagAE compared to CagAW. Our findings revealed the phosphorylated tyrosine in the EPIYA motif is very important for the binding of CagA to Grb2. Phe at Y + 5 position in EPIYA-D, which interacts with Trp121 in SH2 domain of Grb2, established the higher affinity than the interaction of EPIYA-C and Grb2-SH2. The substitute of Phe to Asp/Ala in CagAE EPIYA-D reduced the recruitment of Grb2 by CagAE, and neutralized the stronger induced malignant characteristics of the recipient cells. These findings provide additional insights into the distinct regulatory mechanisms employed by CagAE and CagAW, contributing to a better understanding of the higher oncogenic risk associated with H. pylori CagAE.