Reconstituted nascent adhesion condensates drive actin polymerization on supported lipid bilayers.

Abstract

Nascent adhesions are early integrin-based assemblies that couple the extracellular matrix to the actin cytoskeleton and mature into focal adhesions. Many nascent-adhesion proteins interact through weak, multivalent contacts, suggesting that liquid-like organization may contribute to adhesion assembly. However, how phase separation shapes actin polymerization and organization remains unclear. Here, we compare two vasodilator-stimulated phosphoprotein (VASP)-recruiting adaptor proteins, zyxin and vinculin, to determine how adaptor identity tunes condensate properties and actin coupling. Both zyxin-VASP and vinculin-VASP assemblies drive integrin clustering and support actin filament growth. Notably, zyxin-VASP condensates remain fluid and redistribute along newly formed actin bundles, whereas vinculin-VASP condensates are more rigid and fail to spread along actin despite sustaining polymerization. These results suggest that differential VASP recruitment can modulate condensate properties and actin architecture, providing a potential mechanism for the maturation of nascent adhesions into focal adhesions.