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Direct interaction of the calcium sensor protein synaptotagmin I with a cytoplasmic domain of the α 1 A subunit of the P/Q-type calcium channel

Abstract : Synaptotagmins are synaptic vesicle proteins containing two calcium-binding C2 domains which are involved in coupling calcium influx through voltage-gated channels to vesicle fusion and exocytosis of neurotransmitters. The interaction of synaptotagmins with native P/Q-type calcium channels was studied in solubilized synaptosomes from rat cerebellum. Antibodies against synaptotagmins I and II, but not IV co-immunoprecipitated [125I]omega-conotoxin MVIIC-labelled calcium channels. Direct interactions were studied between in vitro-translated [35S]synaptotagmin I and fusion proteins containing cytoplasmic loops of the alpha1A subunit (BI isoform). Gel overlay revealed the association of synaptotagmin I with a single region (residues 780-969) located in the intracellular loop connecting homologous domains II and III. Saturable calcium-independent binding occurred with equilibrium dissociation constants of 70 nM and 340 nM at 4 degrees C and pH 7.4, and association was blocked by addition of excess recombinant synaptotagmin I. Direct synaptotagmin binding to the pore-forming subunit of the P/Q-type channel may optimally locate the calcium-binding sites that initiate exocytosis within a zone of voltage-gated calcium entry.
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https://www.hal.inserm.fr/inserm-03246721
Contributor : Cécile Raymond <>
Submitted on : Wednesday, June 2, 2021 - 3:14:36 PM
Last modification on : Wednesday, June 2, 2021 - 4:20:59 PM
Long-term archiving on: : Friday, September 3, 2021 - 7:34:45 PM

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Nathalie Charvin, Christian Lévêque, Denise Walker, Frédérique Berton, Cécile Raymond, et al.. Direct interaction of the calcium sensor protein synaptotagmin I with a cytoplasmic domain of the α 1 A subunit of the P/Q-type calcium channel. EMBO Journal, EMBO Press, 1997, 16 (15), pp.4591-6. ⟨10.1093/emboj/16.15.4591⟩. ⟨inserm-03246721⟩

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