The role of Sec1p-related proteins in vesicle trafficking in the nerve terminal

Vesicle trafficking at multiple stages of the secretory pathway depends on a family of soluble proteins related to yeast Sec1p. In yeast, this family consists of four members: the late-acting Sec1p that is required for vesicular transport between the Golgi apparatus and the cell surface; Vps33p and Vps45p which are required for trafficking between the Golgi complex and the lysosome-like vacuole; and Sly1p that is essential for trafficking between the endoplasmic reticulum and the Golgi apparatus. In mammalian systems, homologues of these proteins have been identified. In particular, a neural-specific Sec1p homologue (n-sec1/Munc-18) binds the plasma membrane protein syntaxin and may regulate synaptic vesicle docking. The Sec1p family of proteins is essential for vesicle trafficking in both regulated and constitutive trafficking pathways, and n-sec1 is critical in the regulated release of neurotransmitter from the nerve terminal.