Identification and Characterization of a Nerve Terminal-enriched Amphiphysin Isoform

Abstract

Amphiphysin is a nerve terminal-enriched protein thought to function in synaptic vesicle endocytosis, in part through Src homology 3 (SH3) domain-mediated interactions with dynamin and synaptojanin. Here, we report the characterization of a novel amphiphysin isoform (termed amphiphysin II) that was identified through a homology search of the data base of expressed sequence tags. Antibodies specific to amphiphysin II recognize a 90-kDa protein on Western blot that is brainspecific and highly enriched in nerve terminals. Like amphiphysin (now referred to as amphiphysin I), amphiphysin II binds to dynamin and synaptojanin through its SH3 domain. Further, both proteins bind directly to clathrin in an SH3 domain-independent manner. Taken together, these data suggest that amphiphysin II may participate with amphiphysin I in the regulation of synaptic vesicle endocytosis.

Mechanisms of apoptosis by c-Myc

“…How Bin1 and c-Abl in¯uence the action of each other in proliferation, di erentiation, and apoptosis remains to be determined, however. Second, Bin1 is subjected to extensive alternate splicing, especially in neurons (Butler et al, 1997;Ramjaun et al, 1997;Tsutsui et al, 1997;Wechsler-Reya et al, 1997b;Ramjaun and McPherson, 1998), and it is localized to the cytosol as well as the nucleus in certain cells (Butler et al, 1997;Kadlec and Pendergast, 1997;Wechsler-Reya et al, 1998). The N and C-terminal regions of Bin1 are related to amphiphysin, a neuronal protein that is a paraneoplastic autoimmune antigen in breast and lung cancer (David et al, 1994;Dropcho, 1996).…”

The c-Myc-interacting adaptor protein Bin1 activates a caspase-independent cell death program

“…We next examined whether cells induced to die by Bin1 exhibited any di erences in endocytosis, because brain-speci®c splice isoforms of Bin1 that localize to the cytosol in di erentiated neurons have been implicated in this process, like the related adaptor protein amphiphysin (David et al, 1996;Ramjaun et al, 1997;Wigge et al, 1997). Ubiquitous splice isoforms of Bin1 that localize to the nucleus lack brain-speci®c exons required for interaction with clathrin-coated endocytotic vesicles and AP2 (Ramjaun and McPherson, 1998;P.…”

“…It was identi®ed initially through its ability to interact with and inhibit malignant transformation by c-Myc (Sakamuro et al, 1996). Subsequent investigations established that there are two ubiquitous slice isoforms of Bin1 and several other splice forms that are restricted in expression to muscle or brain (Butler et al, 1997;Ramjaun et al, 1997;Tsutsui et al, 1997;Wechsler-Reya et al, 1997b, 1998. Bin1 polypeptides are related in their terminal domains to amphiphysin, a neuronal protein involved in synaptic vesicle endocytosis, and brain isoforms which are most similar have been termed alternately amphiphysin II or amphiphysin-like (amphl).…”

Cortactin: coupling membrane dynamics to cortical actin assembly

“…The association of dynamin with clathrin-coated pits is actin-independent, and is mediated through amphiphysins I and II (Wigge and McMahon, 1998). The amphiphysin SH3 domain binds to sequences in the dynamin proline-rich region (David et al, 1996) while the amino terminal region of amphiphysins interact with clathrin (Ramjaun et al, 1997) and the clathrin-binding adaptor protein AP2 (David et al, 1996). How the activities of cortactin, mAbp1, syndapin and amphipysin regulate the cortical actin cytoskeleton and coordinate with dynamin GTPase activity during endocytic membrane ®ssion is highly complex.…”