Myosin II activity regulates vinculin recruitment to focal adhesions through FAK-mediated paxillin phosphorylation

TLDR

Focal adhesions are mechanosensitive complexes that grow and remodel in response to myosin II–driven cytoskeletal tension during FA maturation. The study aimed to identify proteins whose recruitment to focal adhesions depends on myosin II and to uncover the mechanism underlying this tension‑sensitive association. Myosin II activity and extracellular matrix stiffness trigger FAK/Src phosphorylation of paxillin at tyrosines 31 and 118, which promotes vinculin binding; phosphomimetic paxillin mutants can recruit vinculin independently of myosin II, highlighting paxillin’s role in mechanosensing and FA maturation.

Abstract

Focal adhesions (FAs) are mechanosensitive adhesion and signaling complexes that grow and change composition in response to myosin II–mediated cytoskeletal tension in a process known as FA maturation. To understand tension-mediated FA maturation, we sought to identify proteins that are recruited to FAs in a myosin II–dependent manner and to examine the mechanism for their myosin II–sensitive FA association. We find that FA recruitment of both the cytoskeletal adapter protein vinculin and the tyrosine kinase FA kinase (FAK) are myosin II and extracellular matrix (ECM) stiffness dependent. Myosin II activity promotes FAK/Src-mediated phosphorylation of paxillin on tyrosines 31 and 118 and vinculin association with paxillin. We show that phosphomimic mutations of paxillin can specifically induce the recruitment of vinculin to adhesions independent of myosin II activity. These results reveal an important role for paxillin in adhesion mechanosensing via myosin II–mediated FAK phosphorylation of paxillin that promotes vinculin FA recruitment to reinforce the cytoskeletal ECM linkage and drive FA maturation.