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 (CagA^E) bearing the EPIYA-D motif exhibits a higher risk than the Western-type (CagA^W) with EPIYA-C motifs. In this study, we investigated the interactions of CagA^E and CagA^W and host intracellular Grb2 and found a pronouncedly greater recruitment of Grb2 by CagA^E compared to CagA^W. 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 CagA^E EPIYA-D reduced the recruitment of Grb2 by CagA^E, and neutralized the stronger induced malignant characteristics of the recipient cells. These findings provide additional insights into the distinct regulatory mechanisms employed by CagA^E and CagA^W, contributing to a better understanding of the higher oncogenic risk associated with H. pylori CagA^E.