Mechanical Energy of Protein Phase Separation Shapes Cell Membranes

Abstract

Clathrin-mediated endocytosis (CME) underlies intra- and extracellular material trafficking in eukaryotes, and is essential to protein metabolism, intercellular signaling, membrane remodeling and other cell regulatory processes. Although CME is usually driven by F-actin polymerization, membrane invagination can also occur through actin independent mechanisms. Here, we show that viscoelastic protein condensates that form via liquid-liquid phase separation at the sites of endocytosis initiation facilitate actin independent CME. Binding energies of the condensate with the membrane and surrounding cytosol provides work required to drive membrane invagination. Our findings expand the repertoire of functions associated with protein condensates that form via liquid-liquid phase separation to include their ability to do work at soft interfaces, thus shaping and organizing cellular matter.