Spatiotemporal dynamics of beta-adrenergic cAMP signals and L-type Ca2+ channel regulation in adult rat ventricular myocytes: role of phosphodiesterases.
Steady-state activation of cardiac beta-adrenergic receptors leads to an intracellular compartmentation of cAMP resulting from localized cyclic nucleotide phosphodiesterase (PDE) activity. To evaluate the time course of the cAMP changes in the different compartments, brief (15 seconds) pulses of isoprenaline (100 nmol/L) were applied to adult rat ventricular myocytes (ARVMs) while monitoring cAMP changes beneath the membrane using engineered cyclic nucleotide-gated channels and within the cytosol with the fluorescence resonance energy transfer-based sensor, Epac2-camps. cAMP kinetics in the two compartments were compared to the time course of the L-type Ca(2+) channel current (I(Ca,L)) amplitude. The onset and recovery of cAMP transients were, respectively, 30% and 50% faster at the plasma membrane than in the cytosol, in agreement with a rapid production and degradation of the second messenger at the plasma membrane and a restricted diffusion of cAMP to the cytosol. I(Ca,L) amplitude increased twice slower than cAMP at the membrane, and the current remained elevated for approximately 5 minutes after cAMP had already returned to basal level, indicating that cAMP changes are not rate-limiting in channel phosphorylation/dephosphorylation. Inhibition of PDE4 (with 10 micromol/L Ro 20-1724) increased the amplitude and dramatically slowed down the onset and recovery of cAMP signals, whereas PDE3 blockade (with 1 micromol/L cilostamide) had a minor effect only on subsarcolemmal cAMP. However, when both PDE3 and PDE4 were inhibited, or when all PDEs were blocked using 3-isobutyl-l-methylxanthine (300 micromol/L), cAMP signals and I(Ca,L) declined with a time constant >10 minutes. cAMP-dependent protein kinase inhibition with protein kinase inhibitor produced a similar effect as a partial inhibition of PDE4 on the cytosolic cAMP transient. Consistently, cAMP-PDE assay on ARVMs briefly (15 seconds) exposed to isoprenaline showed a pronounced (up to approximately 50%) dose-dependent increase in total PDE activity, which was mainly attributable to activation of PDE4. These results reveal temporally distinct beta-adrenergic receptor cAMP compartments in ARVMs and shed new light on the intricate roles of PDE3 and PDE4.
Leroy
Jérôme
J
INSERM U-769, Université Paris-Sud 11, Faculté de Pharmacie, 5, Rue J.-B. Clément, F-92296 Châtenay-Malabry Cedex, France.
Abi-Gerges
Aniella
A
Nikolaev
Viacheslav O
VO
Richter
Wito
W
Lechêne
Patrick
P
Mazet
Jean-Luc
JL
Conti
Marco
M
Fischmeister
Rodolphe
R
Vandecasteele
Grégoire
G
D012368:4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D015374:Biosensing Techniques; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3 / Q000378:metabolism*; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000378:metabolism*; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000235:genetics / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D031541:Fluorescence Resonance Energy Transfer; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D006352:Heart Ventricles / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials; D008856:Microscopy, Fluorescence / Q000379:methods; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D058987:Phosphodiesterase 3 Inhibitors; D058988:Phosphodiesterase 4 Inhibitors; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010766:Phosphorylation; D015363:Quinolones / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D012508:Sarcolemma / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
D000318:Adrenergic beta-Agonists; C504728:Cacna1c protein, rat; D020746:Calcium Channels, L-Type; D054815:Cyclic Nucleotide-Gated Cation Channels; D020662:Guanine Nucleotide Exchange Factors; D058987:Phosphodiesterase 3 Inhibitors; D058988:Phosphodiesterase 4 Inhibitors; D010726:Phosphodiesterase Inhibitors; D015363:Quinolones; D011943:Receptors, Adrenergic, beta; D012368:4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone; C021294:cilostamide; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D007545:Isoproterenol