title: Feedback control through cGMP-dependent protein kinase contributes to differential regulation and compartmentation of cGMP in rat cardiac myocytes.
abstract: BACKGROUND
  We have shown recently that particulate (pGC) and soluble guanylyl (sGC) cyclases synthesize cGMP in different compartments in adult rat ventricular myocytes (ARVMs).
  
  
  OBJECTIVE
  We hypothesized that cGMP-dependent protein kinase (PKG) exerts a feedback control on cGMP concentration contributing to its intracellular compartmentation.
  
  
  RESULTS
  Global cGMP levels, cGMP-phosphodiesterase (PDE) and pGC enzymatic activities were determined in purified ARVMs. Subsarcolemmal cGMP signals were monitored in single cells by recording the cGMP-gated current (I(CNG)) in myocytes expressing the wild-type rat olfactory cyclic nucleotide-gated (CNG) channel. Whereas the NO donor S-nitroso-N-acetyl-penicillamine (SNAP) (100 μmol/L) produced little effect on I(CNG), the response increased 2-fold in the presence of the PKG inhibitors KT5823 (50 nmol/L) or DT-2 (2 μmol/L). The effect of KT5823 was abolished in the presence of the nonselective cyclic nucleotide PDE inhibitor 3-isobutyl-1-methylxantine (IBMX) (100 μmol/L) or the selective cGMP-PDE5 inhibitor sildenafil (100 nmol/L). PKG inhibition also potentiated the effect of SNAP on global cGMP levels and fully blocked the increase in cGMP-PDE5 activity. In contrast, PKG inhibition decreased by ≈50% the I(CNG) response to ANP (10 and 100 nmol/L), even in the presence of IBMX. Conversely, PKG activation increased the I(CNG) response to ANP and amplified the stimulatory effect of ANP on pGC activity.
  
  
  CONCLUSIONS
  PKG activation in adult cardiomyocytes limits the accumulation of cGMP induced by NO donors via PDE5 stimulation but increases that induced by natriuretic peptides. These findings support the paradigm that cGMP is not uniformly distributed in the cytosol and identifies PKG as a key component in this process.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche Inserm U769, Châtenay-Malabry Cedex, France.
authors.forename: Liliana R V
authors.initials: LR
authors.lastname: Castro
authors.forename: Julia
authors.initials: J
authors.lastname: Schittl
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Fischmeister
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054678:Cyclic Nucleotide Phosphodiesterases, Type 2 / Q000378:metabolism; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5 / Q000378:metabolism; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000235:genetics / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D025461:Feedback, Physiological; D006162:Guanylate Cyclase / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology*; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D012508:Sarcolemma / Q000201:enzymology; D015290:Second Messenger Systems / Q000187:drug effects; D000071756:Soluble Guanylyl Cyclase; D013997:Time Factors; D014162:Transfection
chemical_list: C518239:Cnga2 protein, rat; D054815:Cyclic Nucleotide-Gated Cation Channels; D020030:Nitric Oxide Donors; D010726:Phosphodiesterase Inhibitors; D047428:Protein Kinase Inhibitors; D018160:Receptors, Cytoplasmic and Nuclear; D009569:Nitric Oxide; D009320:Atrial Natriuretic Factor; D017869:Cyclic GMP-Dependent Protein Kinases; D054678:Cyclic Nucleotide Phosphodiesterases, Type 2; C517278:Pde2a protein, rat; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D006152:Cyclic GMP