Role of β1- and β2-adrenergic receptors in regulation of Cl−and Ca2+channels in guinea pig ventricular myocytes

Hool, Livia C.; Harvey, Robert D.

doi:10.1152/ajpheart.1997.273.4.h1669

Cited by 27 publications

(30 citation statements)

References 18 publications

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“…Guinea pig ventricular myocytes were chosen for this study because they express only the ␤ 1 AR subtype (11,22). Exposure of these cells to adenovirus containing the DNA sequence for the Epac2-based biosensor exhibited significant expression 24 -48 h after infection (Fig.…”

Section: Resultsmentioning

confidence: 99%

Cytoplasmic cAMP concentrations in intact cardiac myocytes

Iancu

Gopalakrishnan

Warrier

et al. 2008

American Journal of Physiology-Cell Physiology

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.-In cardiac myocytes there is evidence that activation of some receptors can regulate protein kinase A (PKA)-dependent responses by stimulating cAMP production that is limited to discrete intracellular domains. We previously developed a computational model of compartmentalized cAMP signaling to investigate the feasibility of this idea. The model was able to reproduce experimental results demonstrating that both ␤ 1-adrenergic and M2 muscarinic receptor-mediated cAMP changes occur in microdomains associated with PKA signaling. However, the model also suggested that the cAMP concentration throughout most of the cell could be significantly higher than that found in PKA-signaling domains. In the present study we tested this counterintuitive hypothesis using a freely diffusible fluorescence resonance energy transferbased biosensor constructed from the type 2 exchange protein activated by cAMP (Epac2-camps). It was determined that in adult ventricular myocytes the basal cAMP concentration detected by the probe is ϳ1.2 M, which is high enough to maximally activate PKA. Furthermore, the probe detected responses produced by both ␤1 and M2 receptor activation. Modeling suggests that responses detected by Epac2-camps mainly reflect what is happening in a bulk cytosolic compartment with little contribution from microdomains where PKA signaling occurs. These results support the conclusion that even though ␤1 and M2 receptor activation can produce global changes in cAMP, compartmentation plays an important role by maintaining microdomains where cAMP levels are significantly below that found throughout most of the cell. This allows receptor stimulation to regulate cAMP activity over concentration ranges appropriate for modulating both higher (e.g., PKA) and lower affinity (e.g., Epac) effectors.␤-adrenergic receptor signaling; muscarinic receptor signaling; live cell imaging; fluorescence resonance energy transfer; biosensors MANY DIFFERENT NEUROTRANSMITTERS and hormones control a wide range of cellular processes by regulating the production of a common second messenger, cAMP (32). This signaling pathway plays a particularly important role in sympathetic regulation of cardiac function, where ␤ 1 -adrenergic receptor (␤ 1 AR) activation generates significant changes in the electrical, mechanical, and metabolic properties of the heart by stimulating the production of cAMP and activating protein kinase A (PKA) (4). Although other G protein-coupled receptors are also able to affect cAMP production in the heart, they do not all produce the same responses. This has led to the hypothesis that cAMP production is compartmentalized and that different receptors can regulate cAMP production in specific microdomains (31).The recent development of several different biosensors capable of monitoring cAMP activity in intact living cells has provided a means of obtaining more direct proof that compartmentation occurs (20,33,37). Some of these sensors are targeted to specific subcellular locations. This includes the fluorescence resonance energ...

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Section: Resultsmentioning

confidence: 99%

Cytoplasmic cAMP concentrations in intact cardiac myocytes

Iancu

Gopalakrishnan

Warrier

et al. 2008

American Journal of Physiology-Cell Physiology

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“…It is known that tyrosine phosphorylation of ␤ 2 -adrenergic receptors inhibits their ability to activate adenylate cyclase. 29,30 Although regulation of ion channels in guinea pig ventricular myocytes is mediated solely through the activation of ␤ 1 -adrenergic receptors, 31 there is evidence that tyrosine phosphorylation of this receptor also inhibits its ability to stimulate cAMP production. 21 Investigation of this hypothesis awaits further study.…”

Section: Discussionmentioning

confidence: 99%

Genistein Increases the Sensitivity of Cardiac Ion Channels to β-Adrenergic Receptor Stimulation

Hool

Middleton

Harvey

1998

Circulation Research

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The whole-cell patch-clamp technique was used to monitor the effects of genistein, a tyrosine kinase inhibitor, on membrane currents recorded from isolated guinea pig ventricular myocytes. Under control conditions, genistein (50 micromol/L) did not activate the latent cAMP-regulated Cl- current (ICl). However, in the presence of a subthreshold concentration (1 nmol/L) of the beta-adrenergic agonist isoproterenol (Iso), genistein caused a near-maximal activation of this current. In the absence of genistein, Iso activated ICl with an EC50 of 5 nmol/L. In the presence of genistein, Iso activated ICl with an EC50 of 0.3 nmol/L. This facilitatory effect was not observed in the presence of daidzein (50 micromol/L), an analogue of genistein that only weakly inhibits tyrosine kinase activity. Furthermore, peroxovanadate, a potent inhibitor of phosphotyrosine phosphatase activity, inhibited ICl activated by Iso alone, and it blocked the stimulatory effect of genistein in the presence of Iso. To determine whether the stimulatory effect of genistein was specific for ICl, we also studied its action on the cAMP-regulated delayed rectifier K+ current (IK) and L-type Ca2+ current (ICa-L) present in these cells. Basal IK and ICa-L were partially (approximately 30% to 40%) inhibited by genistein. However, this inhibitory effect was mimicked by daidzein, suggesting that inhibition of tyrosine kinase activity is not involved. In addition to the nonspecific inhibitory effect, genistein also caused a significant increase in the beta-adrenergic sensitivity of the unblocked cationic currents. In the absence of genistein, 1 nmol/L Iso had no effect on either IK or ICa-L. However, in the presence of genistein, 1 nmol/L Iso significantly increased the magnitude of both currents. These results suggest that tyrosine kinase activity may play an important role in regulating beta-adrenergic responsiveness of the heart.

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“…Whether such a mechanism can explain the results of the present study is yet to be determined. Although Iso has been reported to mediate cAMP-dependent responses by acting at both ␤ 1 -and ␤ 2 -ARs in some cardiac preparations (Xiao et al, 1999), we have previously demonstrated that in guinea pig ventricular myocytes Iso regulates ion channel function solely through ␤ 1 -ARs (Hool and Harvey, 1997). Therefore, an important question to address is whether or not direct tyrosine phosphorylation can regulate ␤ 1 -ARs in cardiac myocytes the same way that it regulates ␤ 2 -ARs in noncardiac preparations.…”

Section: Ptp Inhibitors Regulate ␤-Adrenergic Responses In Heart 1219mentioning

confidence: 94%

Tyrosine Phosphatase Inhibitors Selectively Antagonize β-Adrenergic Receptor-Dependent Regulation of Cardiac Ion Channels

2000

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␤-Adrenergic receptor stimulation regulates the activity of several different cardiac ion channels through an adenylate cyclase/cAMP/protein kinase A-dependent mechanism. Previous work has suggested that basal tyrosine kinase activity attenuates the ␤-adrenergic responsiveness of these cardiac ion channels, supporting the idea that tyrosine phosphorylation exerts an inhibitory effect at some point in the common signaling pathway. To determine which element in the ␤-adrenergic pathway is regulated by tyrosine kinase activity, we studied the effects of various protein tyrosine phosphatase (PTP) inhibitors on the cAMP-dependent regulation of the L-type Ca 2ϩ current in guinea pig ventricular myocytes. Three such compounds, sodium orthovanadate, peroxovanadate, and bpV(phen), had no effect on the basal Ca 2ϩ current, yet each caused a pronounced inhibition of the Ca 2ϩ current stimulated by the ␤-adrenergic receptor agonist isoproterenol. These observations are consistent with the idea that basal tyrosine kinase activity is capable of inhibiting ␤-adrenergic responses. However, these PTP inhibitors had no effect on cAMP-dependent stimulation of the Ca 2ϩ current via activation of adenylate cyclase with forskolin or activation of H 2 -histaminergic receptors with histamine. These results are consistent with the idea that inhibition of PTP activity produces an inhibitory effect involving a tyrosine kinase-dependent mechanism acting selectively at the level of the ␤-adrenergic receptor. This signaling mechanism does not seem to be linked to tyrosine kinase activity associated with insulin and insulin-like growth factor receptors, because acute exposure to agonists of these receptors did not inhibit isoproterenol regulation of the Ca 2ϩ current.

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Role of β₁- and β₂-adrenergic receptors in regulation of Cl⁻and Ca²⁺channels in guinea pig ventricular myocytes

Cited by 27 publications

References 18 publications

Cytoplasmic cAMP concentrations in intact cardiac myocytes

Cytoplasmic cAMP concentrations in intact cardiac myocytes

Genistein Increases the Sensitivity of Cardiac Ion Channels to β-Adrenergic Receptor Stimulation

Tyrosine Phosphatase Inhibitors Selectively Antagonize β-Adrenergic Receptor-Dependent Regulation of Cardiac Ion Channels

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