title: Membrane fission by protein crowding.
abstract: Membrane fission, which facilitates compartmentalization of biological processes into discrete, membrane-bound volumes, is essential for cellular life. Proteins with specific structural features including constricting rings, helical scaffolds, and hydrophobic membrane insertions are thought to be the primary drivers of fission. In contrast, here we report a mechanism of fission that is independent of protein structure-steric pressure among membrane-bound proteins. In particular, random collisions among crowded proteins generate substantial pressure, which if unbalanced on the opposite membrane surface can dramatically increase membrane curvature, leading to fission. Using the endocytic protein epsin1 N-terminal homology domain (ENTH), previously thought to drive fission by hydrophobic insertion, our results show that membrane coverage correlates equally with fission regardless of the hydrophobicity of insertions. Specifically, combining FRET-based measurements of membrane coverage with multiple, independent measurements of membrane vesiculation revealed that fission became spontaneous as steric pressure increased. Further, fission efficiency remained equally potent when helices were replaced by synthetic membrane-binding motifs. These data challenge the view that hydrophobic insertions drive membrane fission, suggesting instead that the role of insertions is to anchor proteins strongly to membrane surfaces, amplifying steric pressure. In line with these conclusions, even green fluorescent protein (GFP) was able to drive fission efficiently when bound to the membrane at high coverage. Our conclusions are further strengthened by the finding that intrinsically disordered proteins, which have large hydrodynamic radii yet lack a defined structure, drove fission with substantially greater potency than smaller, structured proteins.
authors.affiliation: Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712.
authors.forename: Wilton T
authors.initials: WT
authors.lastname: Snead
authors.affiliation: Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712.
authors.forename: Carl C
authors.initials: CC
authors.lastname: Hayden
authors.affiliation: Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712.
authors.forename: Avinash K
authors.initials: AK
authors.lastname: Gadok
authors.affiliation: Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712.
authors.forename: Chi
authors.initials: C
authors.lastname: Zhao
authors.affiliation: Department of Biochemistry and Structural Biology, Center for Biomedical Neuroscience, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229.
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Lafer
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Padmini
authors.identifier: 0000-0001-5953-4347
authors.initials: P
authors.lastname: Rangamani
authors.affiliation: Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712; jcstach@austin.utexas.edu.|Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712.
authors.forename: Jeanne C
authors.initials: JC
authors.lastname: Stachowiak
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000502:physiology*; D048749:Cytokinesis; D004705:Endocytosis / Q000502:physiology*; D057927:Hydrophobic and Hydrophilic Interactions; D011487:Protein Conformation; D051381:Rats
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; C503962:Clint1 protein, rat
keywords: endocytosis; membrane biophysics; membrane fission; membrane traffic