title: Quantal calcium release by purified reconstituted inositol 1,4,5-trisphosphate receptors.
abstract: Release of intracellular Ca2+ by inositol 1,4,5-trisphosphate (InsP3) occurs through specific receptor proteins which are ligand-activated Ca2+ channels. Changes in intracellular Ca2+ regulate many cellular functions. This Ca2+ release is a discontinuous quantal process in which successive increments of InsP3 transiently release precise amounts of Ca2+ (refs 4-6). Possible explanations of quantal Ca2+ release have included rapid degradation of InsP3, reciprocity of Ca2+ release and sequestration, desensitization of InsP3 receptors, or actions of InsP3 on discrete compartments of Ca2+ with variable sensitivity to InsP3 (ref. 4). We successfully reconstituted InsP3-induced Ca2+ flux in vesicles containing only purified InsP3 receptor protein. The reconstituted vesicles retain the regulatory features of the InsP3 receptor, including phosphorylation sites and modulation of Ca2+ release by adenine nucleotides. Using these reconstituted vesicles, we show here that quantal flux of Ca2+ elicited by InsP3 is a fundamental property of its receptor.
authors.affiliation: Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: C D
authors.initials: CD
authors.lastname: Ferris
authors.forename: A M
authors.initials: AM
authors.lastname: Cameron
authors.forename: R L
authors.initials: RL
authors.lastname: Huganir
authors.forename: S H
authors.initials: SH
authors.lastname: Snyder
mesh_terms: D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels; D002462:Cell Membrane / Q000502:physiology; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007700:Kinetics; D011956:Receptors, Cell Surface / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear
chemical_list: D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium