Protein tyrosine phosphatase 1B targets focal adhesion kinase and paxillin in cell–matrix adhesions

Abstract

Protein tyrosine phosphatase 1B (PTP1B) is an established regulator of cell-matrix adhesion and motility. However, the nature of substrate targets at adhesion sites remains to be validated. Here we used Bimolecular Fluorescence Complementation (BiFC) assays in combination with a substrate trapping mutant of PTP1B to directly examine whether relevant phosphotyrosines on paxillin and FAK are substrates of the phosphatase in the context of cell-matrix adhesion sites. We find that formation of catalytic complexes at cell-matrix adhesions requires intact tyrosine residues Y31 and Y118 on paxillin and the localization of the focal adhesion kinase (FAK) at adhesion sites. In addition, we find that PTP1B specifically targets the Y925 on the focal adhesion target (FAT) domain of FAK at adhesion sites. Electrostatic analysis indicates that dephosphorylation of this residue promotes the closed conformation of the FAT 4-helix bundle, and its interaction with paxillin at adhesion sites.

Cell–Material Interplay in Focal Adhesion Points

“…It also participates in downstream signaling pathways, such as those involving Rho GTPases and MAP kinases, that are important for cell migration and proliferation . In addition, paxillin can be phosphorylated by FAK and other kinases, leading to changes in its conformation and interactions with other proteins in the FA complex. − This phosphorylation can regulate FA dynamics and downstream signaling, further contributing to the overall function of FAs in cell behavior. Another key component of FAs is vinculin, which plays a critical role in regulating their mechanical properties and signaling functions.…”