Phosphatase PTPN22 functions as an adaptor in the mTORC2 complex

mTOR (mechanistic target of rapamycin) kinase is a pivotal regulator of cellular growth and metabolism, integrating signals from nutrients and growth factors. It functions through the assembly of two distinct complexes, mTORC1 and mTORC2, which differ in their substrate specificity and regulation. While the regulation of mTORC1 is well-characterized, less is known about the modulators of mTORC2 signaling. In this study, we identify tyrosine phosphatase PTPN22 as an mTORC2-associated protein. We provide evidence that PTPN22 is essential for the activation of the mTORC2/AKT axis, independent of cell lineage. Loss of PTPN22 results in impaired AKT phosphorylation in response to both basal and growth factor signals. Mechanistically, PTPN22 functions as a scaffolding protein that promotes the mSIN-RICTOR interaction, thereby maintaining mTORC2 complex integrity. Notably, this adaptor function of PTPN22 is independent of its tyrosine phosphatase activity. Functionally, we demonstrate that PTPN22 is required for cell growth and survival in both cellular models and nude mouse xenografts. Together, these findings reveal a non-catalytic role for phosphatase PTPN22 in mTORC2 assembly and function.