title: Expression and modulation of an invertebrate presynaptic calcium channel alpha1 subunit homolog.
abstract: Here we report the first assessment of the expression and modulation of an invertebrate alpha1 subunit homolog of mammalian presynaptic Cav2 calcium channels (N-type and P/Q-type) in mammalian cells. Our data show that molluscan channel (LCav2a) isolated from Lymnaea stagnalis is effectively membrane-targeted and electrophysiologically recordable in tsA-201 cells only when the first 44 amino acids of LCav2a are substituted for the corresponding region of rat Cav2.1. When coexpressed with rat accessory subunits, the biophysical properties of LCav2a-5'rbA resemble those of mammalian N-type calcium channels with respect to activation and inactivation, lack of pronounced calcium dependent inactivation, preferential permeation of barium ions, and cadmium block. Consistent with reports of native Lymnaea calcium currents, the LCav2a-5'rbA channel is insensitive to micromolar concentrations of omega-conotoxin GVIA and is not affected by nifedipine, thus confirming that it is not of the L-type. Interestingly, the LCav2a-5'rbA channel is almost completely and irreversibly inhibited by guanosine 5'-3-O-(thio)triphosphate but not regulated by syntaxin1, suggesting that invertebrate presynaptic calcium channels are differently modulated from their vertebrate counterparts.
authors.affiliation: Department of Physiology and Biophysics, Cellular and Molecular Neurobiology Research Group, University of Calgary, Calgary, T2N 4N1, Canada.
authors.forename: J David
authors.initials: JD
authors.lastname: Spafford
authors.forename: Lina
authors.initials: L
authors.lastname: Chen
authors.forename: Zhong-Ping
authors.initials: ZP
authors.lastname: Feng
authors.forename: August B
authors.initials: AB
authors.lastname: Smit
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Zamponi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000235:genetics / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020864:Calcium Channels, N-Type / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D015870:Gene Expression; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007448:Invertebrates; D008195:Lymnaea; D008322:Mammals; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000502:physiology*; D017434:Protein Structure, Tertiary; D050827:Syntaxin 1; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
chemical_list: D000954:Antigens, Surface; D002121:Calcium Channel Blockers; D020864:Calcium Channels, N-Type; D009419:Nerve Tissue Proteins; D050827:Syntaxin 1; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D020866:omega-Conotoxin GVIA; D019204:GTP-Binding Proteins; D009543:Nifedipine