Synaptic vesicle morphology: a case of protein sorting?

Synaptic vesicles (SVs) are the repositories of neurotransmitters. They are locally recycled at nerve terminals following exocytosis. A unique feature of these vesicles is the uniformity of their morphology, which is well maintained even after rounds of exocytosis and endocytosis. Several studies suggest that disruption of clathrin adaptor proteins leads to defects in sorting cargoes and alterations in SV morphology. Here, we review the links between adaptor proteins and SV size, and highlight how protein sorting may impact SV architecture. Molecular players such as clathrin, adaptor proteins, accessory proteins, SV cargoes and lipid composition may act together to establish a stable regulatory network to maintain SV morphology.