title: PKA-dependent activation of PDE3A and PDE4 and inhibition of adenylyl cyclase V/VI in smooth muscle.
abstract: Regulation of adenylyl cyclase type V/VI and cAMP-specific, cGMP-inhibited phosphodiesterase (PDE) 3 and cAMP-specific PDE4 by cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG) was examined in gastric smooth muscle cells. Expression of PDE3A but not PDE3B was demonstrated by RT-PCR and Western blot. Basal PDE3 and PDE4 activities were present in a ratio of 2:1. Forskolin, isoproterenol, and the PKA activator 5,6-dichloro-1-beta-D-ribofuranosyl benzimidazole 3',5'-cyclic monophosphate, SP-isomer, stimulated PDE3A phosphorylation and both PDE3A and PDE4 activities. Phosphorylation of PDE3A and activation of PDE3A and PDE4 were blocked by the PKA inhibitors [protein kinase inhibitor (PKI) and H-89] but not by the PKG inhibitor (KT-5823). Sodium nitroprusside inhibited PDE3 activity and augmented forskolin- and isoproterenol-stimulated cAMP levels; PDE3 inhibition was reversed by blockade of cGMP synthesis. Forskolin stimulated adenylyl cyclase phosphorylation and activity; PKI blocked phosphorylation and enhanced activity. Stimulation of cAMP and inhibition of inositol 1,4,5-trisphosphate-induced Ca(2+) release and muscle contraction by isoproterenol were augmented additively by PDE3 and PDE4 inhibitors. The results indicate that PKA regulates cAMP levels in smooth muscle via stimulatory phosphorylation of PDE3A and PDE4 and inhibitory phosphorylation of adenylyl cyclase type V/VI. Concurrent generation of cGMP inhibits PDE3 activity and augments cAMP levels.
authors.affiliation: Departments of Physiology and Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA. skarnam@hsc.vcu.edu
authors.forename: Karnam S
authors.initials: KS
authors.lastname: Murthy
authors.forename: Huiping
authors.initials: H
authors.lastname: Zhou
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Makhlouf
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D004004:Dichlororibofuranosylbenzimidazole / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D011817:Rabbits; D013270:Stomach / Q000033:anatomy & histology; D013566:Sympathomimetics / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D013566:Sympathomimetics; D013873:Thionucleotides; C071644:5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-3',5'-monophosphorothioate; D005576:Colforsin; D004004:Dichlororibofuranosylbenzimidazole; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D000262:Adenylyl Cyclases; C121100:adenylyl cyclase 6; C419510:adenylyl cyclase type V; D006152:Cyclic GMP; D007545:Isoproterenol