Abstract
The gastric pathogen Helicobacter pylori colonizes approximately half of the human world population. The bacterium injects the effector protein cytotoxin associated gene A (CagA) via a type-IV secretion system into host epithelial cells, where the protein becomes phosphorylated at specific EPIYA-motifs by cellular kinases. Inside the host cell, CagA can interact with over 25 different proteins in both phosphorylation-dependent and phosphorylation-independent manners, resulting in manipulation of host-cell signaling pathways. During the course of an H. pylori infection, certain host-cell proteins undergo tyrosine dephosphorylation in a CagA-dependent manner, including the actin-binding proteins cortactin and vinculin. A predominant response of intracellular CagA is the binding and activation of tyrosine phosphatase, the human Src-homology-region-2-domain-containing-phosphatase-2 (SHP2). Here, we considered the possibility that activated SHP2 might be responsible for the dephosphorylation of cortactin and vinculin. To investigate this, phosphatase inhibitor studies were performed. Additionally, a complete knockout mutant of SHP2 in AGS cells was created by CRISPR/Cas9 technology, and these cells were infected with H. pylori. However, neither the presence of an inhibitor nor the inactivation of SHP2 prevented the dephosphorylation of cortactin and vinculin upon CagA delivery. Tyrosine dephosphorylation of these proteins is therefore independent of SHP2 and instead must be caused by another, as yet unidentified, protein tyrosine phosphatase.