The β4-β5 loop and C-SH2 domain mediate the unique ability of SHP1 to dephosphorylate CagA and counteract...

The Helicobacter pylori (H. pylori) virulence factor CagA undergoes tyrosine phosphorylation upon entry into host cells, enabling it to engage with multiple SH2 domain-containing proteins and disrupt host signaling pathways to promote carcinogenesis. Among these interacting partners, the tyrosine phosphatase SHP1 plays a unique role as a negative regulator by directly dephosphorylating the phosphorylated EPIYA (EPIpYA) motif of CagA, thereby counteracting its oncogenic effects. However, the molecular basis underlying SHP1's ability to specifically recognize and efficiently dephosphorylate CagA remains poorly understood. In this study, we demonstrated that the β4-β5 loop within the PTP domain of SHP1 is important for its enhanced catalytic efficiency toward the EPIpYA-peptide, as revealed by enzyme kinetics assays and molecular dynamics simulations. Substitution of this loop with the corresponding sequence from SHP1's homologue SHP2 markedly impaired SHP1's ability to dephosphorylate CagA and suppressed its tumor-suppressive function. Furthermore, we showed that the C-SH2 domain of SHP1 contributes to its efficient activation by phosphorylated CagA, and replacement of this domain compromised SHP1's ability to suppress H. pylori-induced malignant phenotypes. Together, these findings identify the β4-β5 loop as a key structural feature that enables SHP1 to efficiently dephosphorylate CagA, and the C-SH2 domain as a critical regulator that enhances SHP1 activation, both of which collectively contribute to counteracting H. pylori-induced carcinogenesis. This study provides a structural basis for understanding the unique tumor-suppressive mechanism of SHP1 and offers potential targets for developing SHP1-specific agonists against H. pylori-associated gastric cancer.