Synaptotagmin regulation of coated pit assembly

Synaptotagmins bind clathrin AP-2 with high affinity via their second C-2 domain, which indicates they are involved in coated pit function. We now report that expression of synaptotagmins lacking either the second C-2 domain or the entire cytoplasmic region potently inhibit endocytosis. Inhibition was dependent on two intramembrane cysteine residues that were found to be essential for synaptotagmin oligomerization. Cells expressing the wild-type, but not the mutant, truncated synaptotagmin fragment had a reduced number of clathrin-coated pits. These results suggest that the formation of synaptotagmin multimers is an important step in the regulation of coated pit assembly.