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 Trp 121 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 .