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

<p><span><span><span><span><span><span><span><span><span><span><span>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 <i>in vitro</i>under physiologic conditions. Cas- and FAK- driven phase separation is sufficient to reconstitute kindlin-dependent integrin clustering <i>in vitro </i>with recombinant mammalian proteins. <i>In vitro</i> 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 <i>in vitro</i> 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 <i>in vitro</i> and in cells. We propose that Cas- and FAK- driven phase separation provides an intracellular trigger for integrin clustering and nascent IAC formation.</span></span></span></span></span></span></span></span></span></span></span></p>