title: A single Gbeta subunit locus controls cross-talk between protein kinase C and G protein regulation of N-type calcium channels.
abstract: The modulation of N-type calcium channels is a key factor in the control of neurotransmitter release. Whereas N-type channels are inhibited by Gbetagamma subunits in a G protein beta-isoform-dependent manner, channel activity is typically stimulated by activation of protein kinase C (PKC). In addition, there is cross-talk among these pathways, such that PKC-dependent phosphorylation of the Gbetagamma target site on the N-type channel antagonizes subsequent G protein inhibition, albeit only for Gbeta(1)-mediated responses. The molecular mechanisms that control this G protein beta subunit subtype-specific regulation have not been described. Here, we show that G protein inhibition of N-type calcium channels is critically dependent on two separate but adjacent approximately 20-amino acid regions of the Gbeta subunit, plus a highly conserved Asn-Tyr-Val motif. These regions are distinct from those implicated previously in Gbetagamma signaling to other effectors such as G protein-coupled inward rectifier potassium channels, phospholipase beta(2), and adenylyl cyclase, thus raising the possibility that the specificity for G protein signaling to calcium channels might rely on unique G protein structural determinants. In addition, we identify a highly specific locus on the Gbeta(1) subunit that serves as a molecular detector of PKC-dependent phosphorylation of the G protein target site on the N-type channel alpha(1) subunit, thus providing for a molecular basis for G protein-PKC cross-talk. Overall, our results significantly advance our understanding of the molecular details underlying the integration of G protein and PKC signaling pathways at the level of the N-type calcium channel alpha(1) subunit.
authors.affiliation: Department of Physiology and Biophysics, Cellular and Molecular Neurobiology Research Group, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors.forename: Clinton J
authors.initials: CJ
authors.lastname: Doering
authors.forename: Alexandra E
authors.initials: AE
authors.lastname: Kisilevsky
authors.forename: Zhong-Ping
authors.initials: ZP
authors.lastname: Feng
authors.forename: Michelle I
authors.initials: MI
authors.lastname: Arnot
authors.forename: Jean
authors.initials: J
authors.lastname: Peloquin
authors.forename: Jawed
authors.initials: J
authors.lastname: Hamid
authors.forename: Wendy
authors.initials: W
authors.lastname: Barr
authors.forename: Aparna
authors.initials: A
authors.lastname: Nirdosh
authors.forename: Brett
authors.initials: B
authors.lastname: Simms
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Winkfein
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Zamponi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020864:Calcium Channels, N-Type / Q000378:metabolism*; D002460:Cell Line; D044387:GTP-Binding Protein beta Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D020864:Calcium Channels, N-Type; D044387:GTP-Binding Protein beta Subunits; D020033:Protein Isoforms; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D011493:Protein Kinase C; D020962:Heterotrimeric GTP-Binding Proteins