title: Interaction of the synprint site of N-type Ca2+ channels with the C2B domain of synaptotagmin I.
abstract: N-type Ca2+ channels mediate Ca2+ influx, which initiates fast exocytosis of neurotransmitters at synapses, and they interact directly with the SNARE proteins syntaxin and SNAP-25 (synaptosome-associated protein of 25 kDa) through a synaptic protein interaction (synprint) site in the intracellular loop connecting domains II and III of their alpha1B subunits. Introduction of peptides containing the synprint site into presynaptic neurons reversibly inhibits synaptic transmission, confirming the importance of interactions with this site in synaptic transmission. Here we report a direct interaction of the synprint peptide from N-type Ca2+ channels with synaptotagmin I, an important Ca2+ sensor for exocytosis, as measured by an affinity-chromatography binding assay and a solid-phase immunoassay. This interaction is mediated by the second C2 domain (C2B) of synaptotagmin I, but is not regulated by Ca2+. Using both immobilized recombinant proteins and native presynaptic membrane proteins, we found that the synprint peptide and synaptotagmin competitively interact with syntaxin. This interaction is Ca2+-dependent because of the Ca2+ dependence of the interactions between syntaxin and these two proteins. These results provide a molecular basis for a physical link between Ca2+ channels and synaptotagmin, and suggest that N-type Ca2+ channels may undergo a complex series of Ca2+-dependent interactions with multiple presynaptic proteins during neurotransmission.
authors.affiliation: Department of Pharmacology, Box 357280, University of Washington, Seattle, WA 98195-7280, USA.
authors.forename: Z H
authors.initials: ZH
authors.lastname: Sheng
authors.forename: C T
authors.initials: CT
authors.lastname: Yokoyama
authors.forename: W A
authors.initials: WA
authors.lastname: Catterall
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry* / Q000378:metabolism*; D020746:Calcium Channels, L-Type; D002135:Calcium-Binding Proteins; D002846:Chromatography, Affinity; D004926:Escherichia coli; D005982:Glutathione Transferase; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D016324:Sequence Tagged Sites; D009435:Synaptic Transmission; D050825:Synaptosomal-Associated Protein 25; D050863:Synaptotagmin I; D050857:Synaptotagmins
chemical_list: D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins; D050825:Synaptosomal-Associated Protein 25; D050863:Synaptotagmin I; D050857:Synaptotagmins; D005982:Glutathione Transferase; D002118:Calcium