Differential expression of endophilin 1 and 2 dimers at central nervous system synapses

Endophilin 1 is proposed to participate in synaptic vesicle biogenesis thro ugh SH3 domain-mediated interactions with the polyphosphoinositide phosphat ase synaptojanin and the GTPase dynamin. Endophilin family members have als o been identified as binding partners for a number of diverse cellular prot eins. We define here the endophilin 1-binding site within synaptojanin 1 an d show that this sequence independently and selectively purifies from brain extracts endophilin 1 and a closely related protein, endophilin 2. Endophi lin 2, like endophilin 1, is highly expressed in brain, concentrated in ner ve terminals, and found in complexes with synaptojanin and dynamin. Althoug h a fraction of endophilins 1 and 2 coexist in the same complex, the distri bution of these endophilin isoforms among central synapses only partially o verlaps. Endophilins 1 and 2 are found predominantly as stable dimers throu gh a predicted coiled-coil domain in their conserved NH2-terminal moiety. D imerization may allow endophilins to link a number of different cellular ta rgets to the endocytic machinery.