Gbetagamma dimers stimulate vascular L-type Ca2+ channels via phosphoinositide 3-kinase.
We have previously reported that, in venous myocytes, Gbetagamma scavengers inhibit angiotensin AT1A receptor-induced stimulation of L-type Ca2+ channels (1). Here, we demonstrate that intracellular infusion of purified Gbetagamma complexes stimulates the L-type Ca2+ channel current in a concentration-dependent manner. Additional intracellular dialysis of GDP-bound inactive Galphao or of a peptide corresponding to the Gbetagamma binding region of the beta-adrenergic receptor kinase completely inhibited the Gbetagamma-induced stimulation of Ca2+ channel currents. The gating properties of the channel were not affected by intracellular application of Gbetagamma, suggesting that Gbetagamma increased the whole-cell calcium conductance. In addition, both the angiotensin AT1A receptor- and the Gbetagamma-induced stimulation of L-type Ca2+ channels were blocked by pretreatment of the cells with wortmannin, at nanomolar concentrations. Correspondingly, intracellular infusion of an enzymatically active purified recombinant Gbetagamma-sensitive phosphoinositide 3-kinase, PI3Kgamma, mimicked Gbetagamma-induced stimulation of Ca2+ channels. Both Gbetagamma- and PI3Kgamma-induced stimulations of Ca2+ channel currents were reduced by protein kinase C inhibitors suggesting that the Gbetagamma/PI3Kgamma-activated transduction pathway involves a protein kinase C. These results indicate for the first time that Gbetagamma dimers stimulate the vascular L-type Ca2+ channels through a Gbetagamma-sensitive PI3K.
Viard
P
P
Laboratoire de Physiologie Cellulaire et Pharmacologie Moléculaire, CNRS ESA 5017, Université de Bordeaux II, 33076 Bordeaux, France.
Exner
T
T
Maier
U
U
Mironneau
J
J
Nürnberg
B
B
Macrez
N
N
D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type; D019204:GTP-Binding Proteins / Q000378:metabolism*; D015640:Ion Channel Gating; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D019204:GTP-Binding Proteins