title: Endophilin drives the fast mode of vesicle retrieval in a ribbon synapse.
abstract: Compensatory endocytosis of exocytosed membrane and recycling of synaptic vesicle components is essential for sustained synaptic transmission at nerve terminals. At the ribbon-type synapse of retinal bipolar cells, manipulations expected to inhibit the interactions of the clathrin adaptor protein complex (AP2) affect only the slow phase of endocytosis (τ = 10-15 s), leading to the conclusion that fast endocytosis (τ = 1-2 s) occurs by a mechanism that differs from the classical pathway of clathrin-coated vesicle retrieval from the plasma membrane. Here we investigate the role of endophilin in endocytosis at this ribbon synapse. Endophilin A1 is a synaptically enriched N-BAR domain-containing protein, suggested to function in clathrin-mediated endocytosis. Internal dialysis of the synaptic terminal with dominant-negative endophilin A1 lacking its linker and Src homology 3 (SH3) domain inhibited the fast mode of endocytosis, while slow endocytosis continued. Dialysis of a peptide that binds endophilin SH3 domain also decreased fast retrieval. Electron microscopy indicated that fast endocytosis occurred by retrieval of small vesicles in most instances. These results indicate that endophilin is involved in fast retrieval of synaptic vesicles occurring by a mechanism that can be distinguished from the classical pathway involving clathrin-AP2 interactions.
authors.affiliation: Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors.forename: Artur
authors.initials: A
authors.lastname: Llobet
authors.affiliation: Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Gallop
authors.affiliation: Department of Biological Sciences, Imperial College, London SW7 2AS, United Kingdom.
authors.forename: Jemima J E
authors.initials: JJE
authors.lastname: Burden
authors.affiliation: Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors.forename: Gamze
authors.initials: G
authors.lastname: Çamdere
authors.affiliation: Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors.forename: Priya
authors.initials: P
authors.lastname: Chandra
authors.affiliation: Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Vallis
authors.affiliation: Department of Biological Sciences, Imperial College, London SW7 2AS, United Kingdom.
authors.forename: Colin R
authors.initials: CR
authors.lastname: Hopkins
authors.affiliation: Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors.forename: Leon
authors.initials: L
authors.lastname: Lagnado
authors.affiliation: Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors.forename: Harvey T
authors.initials: HT
authors.lastname: McMahon
mesh_terms: D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D002966:Clathrin / Q000378:metabolism; D022163:Clathrin-Coated Vesicles / Q000378:metabolism; D004594:Electrophysiology; D004705:Endocytosis / Q000502:physiology*; D006054:Goldfish; D051245:Retinal Bipolar Cells / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology; D013572:Synaptic Vesicles / Q000378:metabolism*
chemical_list: D002966:Clathrin; D000217:Acyltransferases; C018764:2-acylglycerophosphate acyltransferase