SH3 domain-dependent interactions of endophilin with amphiphysin.

Amphiphysin I and II are nerve terminal-enriched proteins thought to function in synaptic vesicle endocytosis. In addition to a C-terminal SH3 domain, the proteins contain a highly conserved putative SH3 binding site and numerous consensus phosphorylation sites. We now demonstrate that amphiphysin I but not amphiphysin II is a phosphoprotein which undergoes dephosphorylation during nerve terminal depolarization. Further, both amphiphysin I and II interact with the SH3 domain of endophilin, a synaptically enriched protein implicated in synaptic vesicle endocytosis. The interaction is direct and mediated through a 43 amino acid region of amphiphysin containing the putative SH3 binding site. These data further support a role for amphiphysin I, II and endophilin in synaptic vesicle endocytosis.