Anchoring protein is required for cAMP-dependent stimulation of L-type Ca(2+) channels in rabbit portal vein.
Stimulation of cardiac L-type Ca(2+) channels by cAMP-dependent protein kinase (PKA) requires anchoring of PKA to a specific subcellular environment by A-kinase anchoring proteins (AKAP). This study evaluated the possible requirement of AKAP in PKA-dependent regulation of L-type Ca(2+) channels in vascular smooth muscle cells using the conventional whole cell patch-clamp technique. Peak Ba(2+) current in freshly isolated rabbit portal vein myocytes was significantly increased by superfusion with either 0.5 microM isoproterenol (131 +/- 3% of the control value, n = 11) or 10 microM 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP; 114 +/- 1%, n = 8). The PKA-induced stimulatory effects of both isoproterenol and 8-BrcAMP were completely abolished by a specific PKA inhibitor KT-5720 (0.2 microM) or by dialyzing cells with Ht 31 (100 microM), a peptide that inhibits the binding of PKA to AKAP. In contrast, Ht 31 did not block the excitatory effect of the catalytic subunit of PKA when dialyzed into the cells. These data suggest that stimulation of Ca(2+) channels in vascular myocytes by endogenous PKA requires localization of PKA through binding to AKAP.
Zhong
J
J
Department of Physiology, University of Nevada School of Medicine, Reno, Nevada 89557, USA.
Hume
J R
JR
Keef
K D
KD
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000502:physiology; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002227:Carbazoles; D002352:Carrier Proteins / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011169:Portal Vein / Q000166:cytology / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D011817:Rabbits
D020746:Calcium Channels, L-Type; D002227:Carbazoles; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; C400224:Ht 31 protein, synthetic; D007211:Indoles; D011506:Proteins; D011758:Pyrroles; D015124:8-Bromo Cyclic Adenosine Monophosphate; D001464:Barium; C057416:KT 5720; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol