title: Ric-3 promotes alpha7 nicotinic receptor assembly and trafficking through the ER subcompartment of dendrites.
abstract: The function of Ric-3, which is required for nicotinic acetylcholine receptor (nAChR) expression in C. elegans, is unclear. Here we found that Ric-3 can promote or inhibit cell-surface delivery of alpha-bungarotoxin-binding nAChRs (BgtRs) composed of alpha7 subunits. At low levels, Ric-3 promoted BgtR assembly, endoplasmic reticulum (ER) release, and cell-surface delivery without trafficking from the ER. At high Ric-3 levels, Ric-3 suppressed BgtR surface delivery, but not its assembly, and BgtRs were retained in the ER or in Ric-3-containing aggregates. In PC12 cells, native BgtRs trafficked to the cell surface from the ER where low levels of endogenous Ric-3 were observed. In cultured neurons, native Ric-3 levels were higher than in PC12 cells, and Ric-3 and alpha7 subunits were found in somata and dendrites, but not axons, of inhibitory interneurons. Ric-3 trafficked with alpha7 subunits in rapidly moving vesicles to dendrites, where it was restricted to the ER subcompartment. We conclude that Ric-3 has two potential functions. At low levels, Ric-3 interactions are short-lived and promote BgtR assembly and ER release. At higher levels, Ric-3 interactions are longer-lived and mediate ER retention. In neurons, Ric-3 ER retention appears to promote transport within the dendritic ER subcompartment, thereby restricting alpha7 trafficking to dendrites and preventing axonal transport.
authors.affiliation: Department of Neurobiology, The University of Chicago, 947 East 58th Street, Chicago, IL 60637, USA.
authors.forename: John K
authors.initials: JK
authors.lastname: Alexander
authors.forename: Daphna
authors.initials: D
authors.lastname: Sagher
authors.forename: Arcadius V
authors.initials: AV
authors.lastname: Krivoshein
authors.forename: Manuel
authors.initials: M
authors.lastname: Criado
authors.forename: Gregory
authors.initials: G
authors.lastname: Jefford
authors.forename: William N
authors.initials: WN
authors.lastname: Green
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001324:Autoantigens / Q000378:metabolism; D002038:Bungarotoxins / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line / Q000166:cytology; D002478:Cells, Cultured; D002645:Chickens; D018678:Cholinergic Agents / Q000494:pharmacology; D003712:Dendrites / Q000187:drug effects / Q000648:ultrastructure*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D005434:Flow Cytometry / Q000379:methods; D005968:Glutamate Decarboxylase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D007456:Iodine Isotopes / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D018832:Molecular Chaperones / Q000235:genetics*; D018408:Patch-Clamp Techniques / Q000379:methods; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D019704:Protein Disulfide-Isomerases / Q000378:metabolism; D021381:Protein Transport / Q000235:genetics; D051381:Rats; D011978:Receptors, Nicotinic / Q000378:metabolism; D014018:Tissue Distribution / Q000187:drug effects; D014162:Transfection / Q000379:methods; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: D001324:Autoantigens; D002038:Bungarotoxins; D018678:Cholinergic Agents; C579167:Chrna7 protein, human; C579166:Chrna7 protein, mouse; C579165:Chrna7 protein, rat; C485182:Cyan Fluorescent Protein; C097741:Golgin subfamily A member 2; D007456:Iodine Isotopes; D008565:Membrane Proteins; D018832:Molecular Chaperones; D011978:Receptors, Nicotinic; C544672:Ric-3 protein, mouse; D064569:alpha7 Nicotinic Acetylcholine Receptor; D049452:Green Fluorescent Proteins; D005968:Glutamate Decarboxylase; D019704:Protein Disulfide-Isomerases; D000109:Acetylcholine