title: Molecular determinants of cysteine string protein modulation of N-type calcium channels.
abstract: Cysteine string proteins (CSPs) are secretory vesicle chaperones that are important for neurotransmitter release. We have previously reported an interaction of CSP with both heterotrimeric GTP-binding proteins (G proteins) and N-type calcium channels that results in a tonic G protein inhibition of the channels. In this report we directly demonstrate that two separate regions of CSP associate with G proteins. The N-terminal binding site of CSP, which includes the J domain, binds Galpha subunits but not Galphabeta subunits whereas the C terminal binding site of CSP associates with either free Galphabeta subunits or Galphabeta in complex with Galpha. The interaction of either binding site of CSP (CSP1-82 or CSP83-198) with G proteins elicits robust tonic inhibition of N-type calcium channel activity. However, CSP1-82 inhibition and CSP83-198 inhibition of calcium channels occur through distinct mechanisms. Calcium channel inhibition by CSP83-198 (but not CSP1-82) is completely blocked by co-expression of the synaptic protein interaction site (synprint) of the N-type channel, indicating that CSP83-198 inhibition is dependent on a physical interaction with the calcium channel. These results suggest that distinct binding sites of CSP can play a role in modulating G protein function and G protein inhibition of calcium channels.
authors.affiliation: Neuroscience Research Group, Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, T2N 4N1, Canada.
authors.forename: Linda C
authors.initials: LC
authors.lastname: Miller
authors.forename: Leigh Anne
authors.initials: LA
authors.lastname: Swayne
authors.forename: Jason G
authors.initials: JG
authors.lastname: Kay
authors.forename: Zhong-Ping
authors.initials: ZP
authors.lastname: Feng
authors.forename: Scott E
authors.initials: SE
authors.lastname: Jarvis
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Zamponi
authors.forename: Janice E A
authors.initials: JE
authors.lastname: Braun
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry; D020864:Calcium Channels, N-Type / Q000737:chemistry*; D018076:DNA, Complementary / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry; D005982:Glutathione Transferase / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins; D006624:Hippocampus / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D008565:Membrane Proteins / Q000737:chemistry*; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013569:Synapses / Q000378:metabolism
chemical_list: D020864:Calcium Channels, N-Type; D018076:DNA, Complementary; D050956:HSP40 Heat-Shock Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C088460:cysteine string protein; D005982:Glutathione Transferase; D019204:GTP-Binding Proteins; D002118:Calcium