Cavin1 intrinsically disordered domains are essential for fuzzy electrostatic interactions and caveola formation

Caveolae are spherical-structured nanodomains of the plasma membrane, generated by cooperative assembly of caveolin and cavin proteins. Cavins are cytosolic peripheral membrane proteins with negatively charged intrinsically disordered regions (DR1-3) that flank positively charged alpha-helical regions (HR1 and HR2). Here we show that the three DR domains of Cavin1 are essential for caveola formation and dynamic trafficking of caveolae. Electrostatic interactions between DR and HR regions promote liquid-liquid phase separation behaviour of Cavin1, assembly of Cavin1 polymers in solution, generation of membrane curvature in a reconstituted system, and Cavin1 recruitment to caveolae in cells. Removal of the first disordered region causes irreversible gel formation in vitro and results in aberrant caveola trafficking through the endosomal system. We propose a model for caveola assembly whereby fuzzy electrostatic interactions between Cavin1 proteins, combined with CAV1 and membrane lipid interactions, are required to generate membrane curvature and a metastable caveola coat.