Synergistic phase separation of two pathways promotes integrin clustering and nascent adhesion formation

Integrin adhesion complexes (IACs) are integrin-based plasma
membrane-associated compartments where cells sense environmental cues. The
physical mechanisms and molecular interactions that mediate initial IAC
formation are unclear. We found that both p130Cas (“Cas”) and Focal
adhesion kinase (“FAK”) undergo liquid-liquid phase separation in
vitrounder physiologic conditions. Cas- and FAK- driven phase separation
is sufficient to reconstitute kindlin-dependent integrin
clustering in vitro with recombinant mammalian
proteins. In vitro condensates and IACs in mouse
embryonic fibroblasts (MEFs) exhibit similar sensitivities to
environmental perturbations including changes in temperature and pH.
Furthermore, mutations that inhibit or enhance phase
separation in vitro reduce or increase the number of
IACs in MEFs, respectively. Finally, we find that the Cas and FAK pathways
act synergistically to promote phase separation, integrin clustering, IAC
formation and partitioning of key components in
vitro and in cells. We propose that Cas- and FAK- driven phase
separation provides an intracellular trigger for integrin clustering and
nascent IAC formation.