IDENTIFICATION AND CHARACTERIZATION OF A NERVE TERMINAL-ENRICHED AMPHIPHYSIN ISOFORM

Amphiphysin is a nerve terminal-enriched protein thought to function i n synaptic vesicle endocytosis, in part through Src homology 3 (SH3) d omain-mediated interactions with dynamin and synaptojanin. Here, we re port the characterization of a novel amphiphysin isoform (termed amphi physin II) that was identified through a homology search of the data b ase of expressed sequence tags. Antibodies specific to amphiphysin II recognize a 90-kDa protein on Western blot that is brain-specific and highly enriched in nerve terminals. Like amphiphysin (now referred to as amphiphysin I), amphiphysin II binds to dynamin and synaptojanin th rough its SH3 domain. Further, both proteins bind directly to clathrin in an SH3 domain-independent manner. Taken together, these data sugge st that amphiphysin II may participate with amphiphysin I in the regul ation of synaptic vesicle endocytosis.