Ca2+ and phosphatidylinositol 4,5-bisphosphate stabilize a Gbeta gamma-sensitive state of Ca V2 Ca 2+ channels.
Direct interactions between G-protein betagamma subunits and N- or P/Q-type Ca(2+) channels mediate the inhibitory action of several neurotransmitters in the brain. Membrane potential, channel phosphorylation, or auxiliary subunit association tightly regulate these interactions and the consequent inhibition of Ca(2+) current. We now provide evidence that intracellular Ca(2+) concentration and phosphoinositides play a stabilizing role in this direct voltage-dependent inhibition. Lowering resting cytosolic Ca(2+) concentration in Xenopus oocytes expressing Ca(V)2Ca(2+) channels strongly decreased basal as well as phasic, agonist-dependent inhibition of Ca(2+) channels by G-proteins. Decreasing phosphoinositide levels also suppressed G-protein inhibition and completely occluded the effects of a subsequent injection of Ca(2+) chelator. Similar regulations are observed in mouse dorsal root ganglia neurons. Alteration of G-protein block by these agents is independent of protein phosphorylation, cytoskeleton dynamics, and GTPase or GDP/GTP exchange activity, suggesting a direct action at the level of the Ca(2+) channel/Gbetagamma-protein interaction. Moreover, affinity binding experiments of intracellular loops of the Ca(V)2.1 Ca(2+) channels to different phospholipids revealed specific interactions between the C-terminal tail of the channel and phosphoinositides. Taken together these data indicate that a Ca(2+)-sensitive interaction of the C-terminal tail of P/Q channels with the plasma membrane is important for G-protein regulation.
Rousset
Matthieu
M
Centre de Recherche de Biochimie Macromoléculaire, CNRS-FRE 2593, 1919 Route de Mende, 34293 Montpellier, France.
Cens
Thierry
T
Gouin-Charnet
Annie
A
Scamps
Frédérique
F
Charnet
Pierre
P
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000737:chemistry*; D002462:Cell Membrane / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D005727:Ganglia, Spinal / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008564:Membrane Potentials; D051379:Mice; D009474:Neurons / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000737:chemistry*; D010743:Phospholipids / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013997:Time Factors; D000077191:Wortmannin; D014981:Xenopus; D014982:Xenopus laevis / Q000378:metabolism
D000730:Androstadienes; D001418:Baclofen; D002118:Calcium; D020864:Calcium Channels, N-Type; D002614:Chelating Agents; D018076:DNA, Complementary; D004533:Egtazic Acid; D004791:Enzyme Inhibitors; D019204:GTP-Binding Proteins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D019269:Phosphatidylinositol 4,5-Diphosphate; D010743:Phospholipids; D000077191:Wortmannin; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid