Details

Autor(en) / Beteiligte

• Rochais, Francesca
• Vandecasteele, Grégoire
• Lefebvre, Florence
• Lugnier, Claire
• Lum, Hazel
• Mazet, Jean-Luc
• Cooper, Dermot M.F.
• Fischmeister, Rodolphe

Titel

Negative Feedback Exerted by cAMP-dependent Protein Kinase and cAMP Phosphodiesterase on Subsarcolemmal cAMP Signals in Intact Cardiac Myocytes

Ist Teil von

• The Journal of biological chemistry, 2004-12, Vol.279 (50), p.52095-52105

Ort / Verlag

American Society for Biochemistry and Molecular Biology

Erscheinungsjahr

2004

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Intracardiac cAMP levels are modulated by hormones and neuromediators with specific effects on contractility and metabolism. To understand how the same second messenger conveys different information, mutants of the rat olfactory cyclic nucleotide-gated (CNG) channel α-subunit CNGA2, encoded into adenoviruses, were used to monitor cAMP in adult rat ventricular myocytes. CNGA2 was not found in native myocytes but was strongly expressed in infected cells. In whole cell patch-clamp experiments, the forskolin analogue L-858051 (L-85) elicited a non-selective, Mg 2+ -sensitive current observed only in infected cells, which was thus identified as the CNG current ( I CNG ). The β-adrenergic agonist isoprenaline (ISO) also activated I CNG , although the maximal efficiency was ≈5 times lower than with L-85. However, ISO and L-85 exerted a similar maximal increase of the L-type Ca 2+ current. The use of a CNGA2 mutant with a higher sensitivity for cAMP indicated that this difference is caused by the activation of a localized fraction of CNG channels by ISO. cAMP-dependent protein kinase (PKA) blockade with H89 or PKI, or phosphodiesterase (PDE) inhibition with IBMX, dramatically potentiated ISO- and L-85-stimulated I CNG . A similar potentiation of β-adrenergic stimulation occurred when PDE4 was blocked, whereas PDE3 inhibition had a smaller effect (by 2-fold). ISO and L-85 increased total PDE3 and PDE4 activities in cardiomyocytes, although this effect was insensitive to H89. However, in the presence of IBMX, H89 had no effect on ISO stimulation of I CNG . This study demonstrates that subsarcolemmal cAMP levels are dynamically regulated by a negative feedback involving PKA stimulation of subsarcolemmal cAMP-PDE.