Involvement of both G protein alphas and beta gamma subunits in beta-adrenergic stimulation of vascular L-type Ca(2+) channels.
1. Previous data have shown that activation of beta(3)-adrenoceptors stimulates vascular L-type Ca(2+) channels through a G alphas-induced stimulation of the cyclic AMP/PKA pathway. The present study investigated whether beta-adrenergic stimulation also uses the G beta gamma/PI3K/PKC pathway to modulate L-type Ca(2+) channels in rat portal vein myocytes. 2. Peak Ba(2+) current (I(Ba)) measured using the whole-cell patch clamp method was maximally increased by application of 10 microm isoprenaline after blockade of beta(3)-adrenoceptors by 1 microM SR59230A. Under these conditions, the isoprenaline-induced stimulation of I(Ba) was reversed by ICI-118551 (a specific beta(2)-adrenoceptor antagonist) but not by atenolol (a specific beta(1)-adrenoceptor antagonist). The beta(2)-adrenoceptor agonist salbutamol increased I(Ba), an effect which was reversed by ICI-118551 whereas the beta(1)-adrenoceptor agonist dobutamine had no effect on I(Ba). 3. Application of PKA inhibitors (H-89 and Rp 8-Br-cyclic AMPs) or a PKC inhibitor (calphostin C) alone did not affect the beta(2)-adrenergic stimulation of I(Ba) whereas simultaneous application of both PKA and PKC inhibitors completely blocked this stimulation. 4. The beta(2)-adrenergic stimulation of L-type Ca(2+) channels was blocked by a pre-treatment with cholera toxin and by intracellular application of an anti-G alphas antibody (directed against the carboxyl terminus of G alphas). In the presence of H-89, intracellular infusion of an anti-Gss(com) antibody or a beta ARK(1) peptide as well as a pre-treatment with wortmannin (a PI3K inhibitor) blocked the beta(2)-adrenergic stimulation of I(Ba). 5. These results suggest that the beta(2)-adrenergic stimulation of vascular L-type Ca(2+) channels involves both G alphas and G beta gamma subunits which exert their stimulatory effects through PKA and PI3K/PKC pathways, respectively.
Viard
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Laboratoire de Signalisation et Interactions Cellulaires, CNRS UMR 5017, Université de Bordeaux II, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France.
Macrez
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N
Mironneau
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Mironneau
J
J
D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000201:enzymology / Q000378:metabolism*; D011169:Portal Vein / Q000166:cytology / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*; D015398:Signal Transduction
D020746:Calcium Channels, L-Type; D018343:Receptors, Adrenergic, beta-2; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D020962:Heterotrimeric GTP-Binding Proteins