A Protein Condensate Drives Actin-Independent Endocytosis

Endocytosis is a process by which living cells absorb materials from their surrounding and maintain the composition of proteins in their outer membrane. Endocytosis begins with invagination of the cell surface membranes which are eventually pinched off to form endocytic vesicles. The forces driving the initial invagination have remained a mystery. We have discovered that endocytosis could be driven by spontaneous phase separation of endocytic coat proteins on the membrane surface, which through a balance of competing adherence between membrane, cytoplasm and condensate, and cohesion of the condensate reflected in their viscoelastic properties, results in membrane being aspirated into the condensate. This ability of biomolecular condensates to perform work at interfaces may be a common morphogenic mechanism governing vesicle production and trafficking as well as other membrane interfacial phenomena such as the formation of transmembrane pores.

Stephen Michnick is Professor of Biochemistry at the Université de Montréal and Adjunct Professors of Bioengineering at McGill University and of Pharmacy at the University of Waterloo. He received his B. Sc. and Ph. D. from the University of Toronto with Jeremy P. Carver and postdoctoral training at Harvard University with Profs. Stuart Schreiber and Martin Karplus (Nobel Prize, Chemistry, 2013). Prof. Michnick is the Canada Research Chair in Cell Architecture and Dynamics and elected Fellow of the Royal Society of Canada and the Royal Society of Chemistry of the UK. Prof. Michnick has received several honors, including in addition to Tier I and II Canada Research Chairs, Burroughs-Wellcome New Investigator and Medical Research Council of Canada Scientist Awards. The Michnick lab studies principles governing the organization and properties of macromolecular assemblies in living cells, including the evolution and dynamics of protein interaction networks and mechano-active biomolecular condensates. They have developed methods to study the spatiotemporal dynamics and topologies of protein interaction networks, on different time and space scales.