Direct voltage control of signaling via P2Y1 and other Galphaq-coupled receptors.
Emerging evidence suggests that Ca2+ release evoked by certain G-protein-coupled receptors can be voltage-dependent; however, the relative contribution of different components of the signaling cascade to this response remains unclear. Using the electrically inexcitable megakaryocyte as a model system, we demonstrate that inositol 1,4,5-trisphosphate-dependent Ca2+ mobilization stimulated by several agonists acting via Galphaq-coupled receptors is potentiated by depolarization and that this effect is most pronounced for ADP. Voltage-dependent Ca2+ release was not induced by direct elevation of inositol 1,4,5-trisphosphate, by agents mimicking diacylglycerol actions, or by activation of phospholipase Cgamma-coupled receptors. The response to voltage did not require voltage-gated Ca2+ channels as it persisted in the presence of nifedipine and was only weakly affected by the holding potential. Strong predepolarizations failed to affect the voltage-dependent Ca2+ increase; thus, an alteration of G-protein betagamma subunit binding is also not involved. Megakaryocytes from P2Y1(-/-) mice lacked voltage-dependent Ca2+ release during the application of ADP but retained this response after stimulation of other Galphaq-coupled receptors. Although depolarization enhanced Ca2+ mobilization resulting from GTPgammaS dialysis and to a lesser extent during AlF4- or thimerosal, these effects all required the presence of P2Y1 receptors. Taken together, the voltage dependence to Ca2+ release via Galphaq-coupled receptors is not due to control of G-proteins or down-stream signals but, rather, can be explained by a voltage sensitivity at the level of the receptor itself. This effect, which is particularly robust for P2Y1 receptors, has wide-spread implications for cell signaling.
Martinez-Pinna
Juan
J
Department of Physiology, University of Cambridge, Cambridge CB2 3EG, United Kingdom.
Gurung
Iman S
IS
Vial
Catherine
C
Leon
Catherine
C
Gachet
Christian
C
Evans
Richard J
RJ
Mahaut-Smith
Martyn P
MP
D000244:Adenosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D017607:Aluminum Compounds / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D004075:Diglycerides / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005459:Fluorides / Q000494:pharmacology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects; D008297:Male; D008533:Megakaryocytes / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009543:Nifedipine / Q000494:pharmacology; D051966:Phospholipase C gamma; D051381:Rats; D017208:Rats, Wistar; D043562:Receptors, G-Protein-Coupled / Q000819:agonists / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D058472:Receptors, Purinergic P2Y1; D015398:Signal Transduction / Q000187:drug effects; D013849:Thimerosal / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism
D017607:Aluminum Compounds; D020746:Calcium Channels, L-Type; D004075:Diglycerides; C546383:P2ry1 protein, mouse; D043562:Receptors, G-Protein-Coupled; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; C050992:tetrafluoroaluminate; D013849:Thimerosal; D000244:Adenosine Diphosphate; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D009543:Nifedipine; D005459:Fluorides; D002118:Calcium