In Vivo Analysis of Membrane Fusion

Membranes provide a barrier that allows chemical reactions to be isolated from the environment. The plasma membrane, for example, delineates self from nonself, and thus must have played an essential role in the evolution of life. Yet under numerous circumstances it is equally important that membranes be breached. Numerous forces oppose the spontaneous fusion of membranes; thus, specialized proteins have evolved to fuse membranes. The most well-understood fusion proteins are the viral fusion proteins and the SNARE proteins used in the secretory pathway. In addition, recent discoveries have lead to models for the fusion of organelles such as mitochondria and peroxisomes, as well as for cell–cell fusion. Despite the diverse structures of fusion proteins, it is possible that they function to drive membranes through a series of common lipid intermediates. Here we review the mechanisms of fusion for biological membranes, and highlight the similarities and differences in these processes