The d5 dopamine receptor mediates large-conductance, calcium- and voltage-activated potassium channel activation in human coronary artery smooth muscle cells.
Large-conductance, calcium- and voltage-activated potassium (BK(Ca)) channels hyperpolarize coronary artery smooth muscle cells, causing vasorelaxation. Dopamine activates BK(Ca) channels by stimulating D(1)-like receptor-mediated increases in cAMP in porcine coronary artery myocytes. There are two D(1)-like receptors (R), D(1)R and D(5)R. We hypothesize that the specific D(1)-like receptor involved in BK(Ca) channel activation in human coronary artery smooth muscle cells (HCASMCs) is the D(5)R and that activation occurs via cAMP cross-activation of cGMP-dependent protein kinase (PKG), rather than cAMP-dependent protein kinase (PKA). The effects of D(1)-like receptor agonists and antagonists on BK(Ca) channel opening in HCASMCs were examined in the presence and absence of PKG/PKA inhibition by cell-attached patch clamp. In the absence of commercially available ligands specific for D(1)R or D(5)R, D(1)R or D(5)R protein was down-regulated by transfecting HCASMCs with human D(1)R or D(5)R antisense oligonucleotides, respectively: cells transfected with scrambled oligonucleotides and nontransfected HCASMCs served as controls. The predominant ion channel conducting outward currents in nontransfected HCASMCs was identified as the large-conductance, calcium- and voltage-activated potassium (BK(Ca)) channel, which was activated by D(1)-like receptor agonists despite PKA inhibition with (9R,10S,12S)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid (KT 5720) (300 nM), but was abolished by inhibiting PKG with 9-methoxy-9-methoxycarbonyl-8-methyl-2,3,9,10-tetrahydro-8,11-epoxy-1H,8H,11H-2,7b-11a-triazadibenzo(a,g) cycloocta(cde)-trinden-1-one (KT 5823) (300 nM). D(1)-like receptor agonists activated BK(Ca) channels in all transfected cells except those transfected with D(5)R antisense oligonucleotides. Thus, the dopamine (D(1)-like) receptor mediates activation of BK(Ca) channels in HCASMCs by D(5)R, not D(1)R, and via PKG, not PKA. This is the first report of differential D(1)-like receptor regulation of vascular smooth muscle function in human cells.
Natarajan
Aruna
A
Department of Pediatrics, Division of Critical Care, Georgetown University Hospital, Washington, DC 20007, USA. an5@gunet.georgetown.edu
Han
Guichun
G
Chen
Shi-you
SY
Yu
Peiying
P
White
Richard
R
Jose
Pedro
P
D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D017447:Receptors, Dopamine D1 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D050641:Receptors, Dopamine D5 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*
D002227:Carbazoles; D004791:Enzyme Inhibitors; D051036:Large-Conductance Calcium-Activated Potassium Channels; D016376:Oligonucleotides, Antisense; D011758:Pyrroles; D017447:Receptors, Dopamine D1; C073601:KT 5823; D050641:Receptors, Dopamine D5; C057416:KT 5720; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases