title: Isoform-specific interaction of the alpha1A subunits of brain Ca2+ channels with the presynaptic proteins syntaxin and SNAP-25.
abstract: Presynaptic Ca2+ channels are crucial elements in neuronal excitation-secretion coupling. In addition to mediating Ca2+ entry to initiate transmitter release, they are thought to interact directly with proteins of the synaptic vesicle docking/fusion machinery. Here we report isoform-specific, stoichiometric interaction of the BI and rbA isoforms of the alpha1A subunit of P/Q-type Ca2+ channels with the presynaptic membrane proteins syntaxin and SNAP-25 in vitro and in rat brain membranes. The BI isoform binds to both proteins, while only interaction with SNAP-25 can be detected in vitro for the rbA isoform. The synaptic protein interaction ("synprint") site involves two adjacent segments of the intracellular loop connecting domains II and III between amino acid residues 722 and 1036 of the BI sequence. This interaction is competitively blocked by the corresponding region of the N-type Ca2+ channel, indicating that these two channels bind to overlapping regions of syntaxin and SNAP-25. Our results provide a molecular basis for a physical link between Ca2+ influx into nerve terminals and subsequent exocytosis of neurotransmitters at synapses that have presynaptic Ca2+ channels containing alpha1A subunits.
authors.affiliation: Department of Pharmacology, University of Washington, Seattle 98195-7280, USA.
authors.forename: J
authors.initials: J
authors.lastname: Rettig
authors.forename: Z H
authors.initials: ZH
authors.lastname: Sheng
authors.forename: D K
authors.initials: DK
authors.lastname: Kim
authors.forename: C D
authors.initials: CD
authors.lastname: Hodson
authors.forename: T P
authors.initials: TP
authors.lastname: Snutch
authors.forename: W A
authors.initials: WA
authors.lastname: Catterall
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D015220:Calcium Channels / Q000737:chemistry* / Q000378:metabolism*; D018288:Carcinoma, Small Cell; D002460:Cell Line; D018076:DNA, Complementary; D015723:Gene Library; D005982:Glutathione Transferase; D006624:Hippocampus / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008175:Lung Neoplasms; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D050765:Qa-SNARE Proteins; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D050825:Synaptosomal-Associated Protein 25; D014407:Tumor Cells, Cultured
chemical_list: D015220:Calcium Channels; D018076:DNA, Complementary; D046911:Macromolecular Substances; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins; C494208:SNAP25 protein, human; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25; D005982:Glutathione Transferase