Adhesion-dependent Caveolin-1 Tyrosine-14 phosphorylation is regulated by FAK in response to changing matrix stiffness.

Integrin-mediated adhesion regulates cellular responses to changes in the mechanical and biochemical properties of the extracellular matrix. Cell-matrix adhesion regulates caveolar endocytosis, dependent on caveolin 1 (Cav1) Tyr14 phosphorylation (pY14Cav1), to control anchorage-dependent signaling. We find that cell-matrix adhesion regulates pY14Cav1 levels in mouse fibroblasts. Biochemical fractionation reveals endogenous pY14Cav1 to be present in caveolae and focal adhesions (FA). Adhesion does not affect caveolar pY14Cav1, supporting its regulation at FA, in which PF-228-mediated inhibition of focal adhesion kinase (FAK) disrupts. Cell adhesion on 2D polyacrylamide matrices of increasing stiffness stimulates Cav1 phosphorylation, which is comparable to the phosphorylation of FAK. Inhibition of FAK across varying stiffnesses shows it regulates pY14Cav1 more prominently at higher stiffness. Taken together, these studies reveal the presence of FAK-pY14Cav1 crosstalk at FA, which is regulated by cell-matrix adhesion.