Mechanisms of COPII vesicle formation and protein sorting.

The evolutionarily conserved coat protein complex II (COPII) generates transport vesicles that mediate protein transport from the endoplasmic reticulum (ER). COPII coat is responsible for direct capture of cargo proteins and for the physical deformation of the ER membrane that drives the COPII vesicle formation. In addition to coat proteins, recent data have indicated that the Ras-like small GTPase Sar1 plays multiple roles, such as COPII coat recruitment, cargo sorting, and completion of the final fission. In the present review, we summarize current knowledge of COPII-mediated vesicle formation from the ER, as well as highlighting non-canonical roles of COPII components.