Abstract

Fission of cellular membranes is ubiquitous and essential for life. Complex protein machineries, such as the dynamin and ESCRT spirals, have evolved to mediate membrane fission during diverse cellular processes, for example, vesicle budding. A new study suggests that non-specialized membrane-bound proteins can induce membrane fission through mass action due to protein crowding. Because up to 2/3 of the mass of cellular membranes is contributed by proteins, membrane protein crowding is an important physiological parameter. Considering the complexity of membrane shape transitions during a fission reaction, spatial and temporal variability in protein distribution, and the abundance of intrinsically disordered regions in proteins on an invaginating membrane, protein crowding can have diverse consequences for fission in the cell. The question is, how and to what extent this mechanism combines with the action of dedicated fission machineries. Membrane fission, which is required for formation of vesicles or cytokinesis, can be carried out by specialized proteins like dynamin and the ESCRT complex. Recent work suggests that fission of cellular membranes, which are densely packed with proteins, can also be induced by protein crowding due to high entropic tension.