title: High-resolution localization of clathrin assembly protein AP180 in the presynaptic terminals of mammalian neurons.
abstract: Synaptic vesicles (SVs) assemble at the presynaptic compartment through a clathrin-dependent mechanism that involves one or more assembly proteins (APs). The assembly protein AP180 is especially efficient at facilitating clathrin cage formation, but its precise ultrastructural localization in neurons is unknown. Using immunoelectron microscopy, we demonstrate the presynaptic localization of AP180 in axon terminals of rat cerebellar neurons. In contrast, the assembly protein AP2 was associated with both the presynaptic plasma membrane and the cytosolic side of the membrane at postsynaptic and extrasynaptic sites. Furthermore, ultrastructural analysis of primate retina showed that AP180 immunoreactivity was preferentially and highly enriched at ribbon synapses, where glutamate is released tonically at high levels and rapid vesicle turnover is essential. To maintain functional synaptic transmission, neurotransmitter-filled SVs must be readily available, and this requires proper reassembly of new vesicles. The expression of AP180, in addition to AP-2, in the clathrin-mediated endocytic pathway might add another level of control to SV reformation for efficient assembly of clathrin, effectively controlling the size of assembled vesicles and faithfully recovering SV-specific components.
authors.affiliation: Department of Neurobiology & Anatomy and Center for Aging & Developmental Biology, University of Rochester, Rochester, New York 14642, USA. pamela_yao@urmc.rochester.edu
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Yao
authors.forename: Paul D
authors.initials: PD
authors.lastname: Coleman
authors.forename: David J
authors.initials: DJ
authors.lastname: Calkins
mesh_terms: D033962:Adaptor Protein Complex 2; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism* / Q000648:ultrastructure; D002451:Cell Compartmentation / Q000502:physiology; D002531:Cerebellum / Q000378:metabolism* / Q000648:ultrastructure; D002966:Clathrin / Q000096:biosynthesis* / Q000648:ultrastructure; D005089:Exocytosis / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry; D008252:Macaca fascicularis; D008565:Membrane Proteins / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D034041:Monomeric Clathrin Assembly Proteins; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000378:metabolism* / Q000648:ultrastructure; D013570:Synaptic Membranes / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D033962:Adaptor Protein Complex 2; D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins; D002966:Clathrin; D008565:Membrane Proteins; D034041:Monomeric Clathrin Assembly Proteins; C439023:clathrin assembly protein AP180