Fission and uncoating of synaptic clathrin-coated vesicles are perturbed by disruption of interactions with the SH3 domain of endophilin

Coordination between sequential steps in synaptic vesicle endocytosis, incl uding clathrin coat formation, fission, and uncoating, appears to involve p rotein-protein interactions. Here, we show that compounds that disrupt inte ractions of the SH3 domain of endophilin with dynamin and synaptojanin impa ir synaptic vesicle endocytosis in a living synapse. Two distinct endocytic intermediates accumulated. Free clathrin-coated vesicles were induced by a peptide-blocking endophilin's SH3 domain and by antibodies to the proline- rich domain (PRD) of synaptojanin. Invaginated clathrin-coated pits were in duced by the same peptide and by the SH3 domain of endophilin. We suggest t hat the SH3 domain of endophilin participates in both fission and uncoating and that it may be a key component of a molecular switch that couples the fission reaction to uncoating.