Intracellular mechanisms mediating reversal of beta-adrenergic stimulation in intact beating hearts

1993 ◽  
Vol 264 (3) ◽  
pp. H791-H797 ◽  
Author(s):  
L. Talosi ◽  
I. Edes ◽  
E. G. Kranias
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Troponin I ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Dependent Protein ◽  
Camp Levels ◽  
Isoproterenol Infusion ◽  
Phosphate Incorporation ◽  
Stimulation Of

The changes in 32P labeling of phosphoproteins were studied in Langendorff-perfused guinea pig hearts during reversal of the stimulatory effects of isoproterenol. Exposure of the hearts to isoproterenol was associated with significant increases in adenosine 3',5'-cyclic monophosphate (cAMP) levels and in the phosphate incorporation into phospholamban in sarcoplasmic reticulum, the 15-kDa protein in the sarcolemma, and troponin I in the myofibrils. Phospholamban was phosphorylated on serine and threonine residues, both of which are sites for cAMP-dependent and Ca(2+)-calmodulin-dependent protein kinases, respectively. Termination of isoproterenol infusion was associated with reversal of the mechanical effects of isoproterenol stimulation and reversal of the increases in tissue cAMP levels. However, the decreases in cAMP levels correlated only with dephosphorylation of phosphoserine in phospholamban. Dephosphorylation of phosphothreonine in phospholamban, the 15-kDa sarcolemmal protein, and troponin I occurred at a slower rate. These findings suggest that cAMP-dependent phosphorylation of phospholamban (phosphoserine) may play a prominent role during beta-adrenergic stimulation of intact hearts.

scholarly journals Phosphorylation of phospholipids in isolated guinea pig hearts stimulated with isoprenaline

1988 ◽  
Vol 251 (1) ◽  
pp. 189-194 ◽  
Author(s):  
G Jakab ◽  
S T Rapundalo ◽  
R J Solaro ◽  
E G Kranias
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Total Phospholipid ◽  
Fold Increase ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Adrenergic Agents ◽  
32P Incorporation ◽  
Phosphate Incorporation ◽  
Stimulation Of

Phosphorylation of phospholipids was studied in Langendorff perfused guinea pig hearts subjected to beta-adrenergic stimulation. Hearts were perfused with Krebs-Henseleit buffer containing [32P]Pi and freeze-clamped in a control condition or at the peak of the inotropic response to isoprenaline. 32P incorporation into total phospholipids, individual phospholipids and polyphosphoinositides was analysed in whole tissue homogenates and membranes, enriched in sarcoplasmic reticulum, prepared from the same hearts. Isoprenaline stimulation of the hearts did not result in any significant changes in the levels of phosphate incorporation in the total phospholipid present in cardiac homogenates (11.6 +/- 0.4 nmol of 32P/g for control hearts and 12.4 +/- 0.5 nmol of 32P/g for isoprenaline-treated hearts; n = 6), although there was a significant increase in the degree of phospholipid phosphorylation in sarcoplasmic reticulum (3.5 +/- 0.3 nmol of 32P/mg for control hearts and 6.7 +/- 0.2 nmol of 32P/mg for isoprenaline-treated hearts; n = 6). Analysis of 32P incorporation into individual phospholipids and polyphosphoinositides revealed that isoprenaline stimulation of the hearts was associated with a 2-3-fold increase in the degree of phosphorylation of phosphatidylinositol monophosphate and bisphosphate as well as phosphatidic acid in both cardiac homogenates and sarcoplasmic reticulum membranes. In addition, there was increased phosphate incorporation into phosphatidylinositol in sarcoplasmic reticulum membranes. Thus, perfusion of guinea pig hearts with isoprenaline is associated with increased formation of polyphosphoinositides and these phospholipids may be involved, at least in part, in mediating the effects of beta-adrenergic agents in the mammalian heart.

Relation between contractile function and regulatory cardiac proteins in hypertrophied hearts

1996 ◽  
Vol 270 (6) ◽  
pp. H2021-H2028 ◽  
Author(s):  
B. Stein ◽  
S. Bartel ◽  
U. Kirchhefer ◽  
S. Kokott ◽  
E. G. Krause ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Troponin I ◽  
Contractile Function ◽  
Papillary Muscles ◽  
Camp Accumulation ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
C Protein ◽  
Camp Formation ◽  
Phosphate Incorporation

The aim of this study was to examine the mechanism(s) underlying the reduced isoproterenol-induced positive inotropic and lusitropic effects in hypertrophied hearts. Chronic beta-adrenergic stimulation (2.4 mg isoproterenol.kg-1. day-1 for 4 days) induced cardiac hypertrophy by 33 +/- 2% in rats. A parallel downregulation of phospholamban (PLB) and sarcoplasmic reticulum Ca2(+)-ATPase (SERCA2) protein expression by 49 and 40%, respectively, was observed, whereas troponin I (TNI) and C protein remained unchanged. In papillary muscles from chronically beta-adrenergically stimulated rats, the isoproterenol-induced positive inotropic and lusitropic effects, as well as adenosine 3',5'-cyclic monophosphate (cAMP) accumulation, were attenuated compared with those in control animals. Acute exposure to isoproterenol induced phosphate incorporation into PLB, TNI, and C protein of 48 +/- 4.6, 55 +/- 5.0, and 27 +/- 4.9 pmol/mg homogenate protein, respectively, in control animals. In the hypertrophied hearts, phosphate incorporation into PLB was reduced by 76%, whereas phosphate incorporation into TNI or C protein remained unchanged. In conclusion, chronic beta-adrenergic stimulation reduced the isoproterenol-stimulated positive inotropic and lusitropic effects in papillary muscles, which were accompanied by 1) diminished cAMP formation, 2) attenuation of cAMP-mediated PLB phosphorylation, and 3) downregulation of PLB and SERCA2 protein.

beta-Adrenergic regulation of cAMP and protein phosphorylation in phospholamban-knockout mouse hearts

1997 ◽  
Vol 272 (2) ◽  
pp. H785-H790 ◽  
Author(s):  
E. Kiss ◽  
I. Edes ◽  
Y. Sato ◽  
W. Luo ◽  
S. B. Liggett ◽  
...  
Keyword(s):  
Protein Phosphorylation ◽  
Troponin I ◽  
Signal Transduction Pathway ◽  
Microsomal Protein ◽  
Mouse Heart ◽  
Wild Type ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
C Protein ◽  
Camp Levels

The stimulatory effects of beta-adrenergic agonists reflect increases in intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels and phosphorylation of key regulatory proteins in the heart. One of these phosphoproteins is phospholamban (PLB) in sarcoplasmic reticulum, and ablation of PLB is associated with attenuation of the contractile responses to beta-adrenergic stimulation in the mouse heart. To determine whether this attenuation of beta-stimulation is due to altered phosphorylation characteristics of the other key cardiac phosphoproteins and/or to compensatory responses occurring in the absence of PLB, PLB-knockout and wild-type hearts were perfused and their protein phosphorylation patterns examined. The beta-adrenergic receptor density, adenylyl cyclase activity, tissue cAMP levels, and the basal phosphoprotein pattern were similar between PLB-knockout and wild-type hearts. Isoproterenol perfusion resulted in similar increases in the tissue cAMP levels and the degree of phosphorylation of troponin I, C protein, and the 21-kDa microsomal protein in wild-type and PLB-knockout hearts. These findings indicate that the attenuation of isoproterenol-mediated increases in contractility of the PLB-knockout hearts is not due to alterations in the beta-adrenergic signal transduction pathway or the degree of phosphorylation of the key cardiac regulatory phosphoproteins in myofibrils and sarcolemma.

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

2004 ◽  
Vol 279 (50) ◽  
pp. 52095-52105 ◽  
Author(s):  
Francesca Rochais ◽  
Grégoire Vandecasteele ◽  
Florence Lefebvre ◽  
Claire Lugnier ◽  
Hazel Lum ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Negative Feedback ◽  
Adrenergic Stimulation ◽  
Dependent Protein Kinase ◽  
Α Subunit ◽  
Camp Dependent Protein Kinase ◽  
Dependent Protein ◽  
Infected Cells ◽  
Camp Levels ◽  
Stimulation Of

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, Mg2+-sensitive current observed only in infected cells, which was thus identified as the CNG current (ICNG). The β-adrenergic agonist isoprenaline (ISO) also activatedICNG, 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 Ca2+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-stimulatedICNG. 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 ofICNG. This study demonstrates that subsarcolemmal cAMP levels are dynamically regulated by a negative feedback involving PKA stimulation of subsarcolemmal cAMP-PDE.

Sign in / Sign up

Export Citation Format

Share Document