title: cAMP activates BKCa channels in pulmonary arterial smooth muscle via cGMP-dependent protein kinase.
abstract: The signal transduction mechanisms defining the role of cyclic nucleotides in the regulation of pulmonary vascular tone is currently an area of great interest. Normally, signaling mechanisms that elevate cAMP and guanosine-3',5'-cyclic monophosphate (cGMP) maintain the pulmonary vasculature in a relaxed state. Modulation of the large-conductance, calcium- and voltage-activated potassium (BK(Ca)) channel is important in the regulation of pulmonary arterial pressure, and inhibition (closing) of the BK(Ca) channel has been implicated in the development of pulmonary hypertension. Accordingly, studies were done to determine the effect of cAMP-elevating agents on BK(Ca) channel activity using patch-clamp studies in pulmonary arterial smooth muscle cells (PASMC) of the fawn-hooded rat (FHR), a recognized animal model of pulmonary hypertension. Forskolin (10 micro M), a stimulator of adenylate cyclase and an activator of cAMP-dependent protein kinase (PKA), and 8-4-chlorophenylthio (CPT)-cAMP (100 micro M), a membrane-permeable derivative of cAMP, opened BK(Ca) channels in single FHR PASMC. Treatment of FHR PASMC with 300 nM KT5823, a selective inhibitor of cGMP-dependent protein kinase (PKG) activity inhibited the effect of both forskolin and CPT-cAMP. In contrast, blocking PKA activation with 300 nM KT5720 had no effect on forskolin or CPT-cAMP-stimulated BK(Ca) channel activity. These results indicate that cAMP-dependent vasodilators activate BK(Ca) channels in PASMC of FHR via PKG-dependent and PKA-independent signaling pathways, which suggests cross-activation between cyclic nucleotide-dependent protein kinases in pulmonary arterial smooth muscle and therefore, a unique signaling pathway for cAMP-induced pulmonary vasodilation.
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, Georgia 30912, USA. sbarman@mail.mcg.edu
authors.forename: Scott A
authors.initials: SA
authors.lastname: Barman
authors.forename: Shu
authors.initials: S
authors.lastname: Zhu
authors.forename: Guichan
authors.initials: G
authors.lastname: Han
authors.forename: Richard E
authors.initials: RE
authors.lastname: White
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002227:Carbazoles; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017380:Hypertrophy, Right Ventricular / Q000378:metabolism; D007211:Indoles; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000201:enzymology*; D018408:Patch-Clamp Techniques; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D011651:Pulmonary Artery / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013873:Thionucleotides / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D010975:Platelet Aggregation Inhibitors; D024681:Potassium Channels, Calcium-Activated; D013873:Thionucleotides; D014665:Vasodilator Agents; C073601:KT 5823; D005576:Colforsin; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; C055656:8-((4-chlorophenyl)thio)cyclic-3',5'-GMP; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP