The catalytic subunit of cyclic AMP-dependent protein kinase directly inhibits sodium channel activities in guinea-pig ventricular myocytes

Sunami, Akihiko; Fan, Zheng; Nakamura, Fumiaki; Naka, Michiko; Tanaka, Toshio; Sawanobori, Tohru; Hiraoka, Masayasu

doi:10.1007/bf00371125

Cited by 33 publications

(18 citation statements)

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“…Early studies with mammalian ventricular myocytes demonstrated a reduction in cardiac I Na in response to PKA. 23,24,28,29 However, relatively positive holding potentials were used. In subsequent investigations in which cells were held at more negative voltages (that would minimize the effects of the negative shift in inactivation), Na ϩ currents were increased by kinase stimulation.…”

Section: Discussionmentioning

confidence: 99%

Activation of Protein Kinase A Modulates Trafficking of the Human Cardiac Sodium Channel in Xenopus Oocytes

Zhou

et al. 2000

Circulation Research

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Abstract-Voltage-gated Na ϩ channels are critical determinants of electrophysiological properties in the heart. Stimulation of ␤-adrenergic receptors, which activate cAMP-dependent protein kinase (protein kinase A [PKA]), can alter impulse conduction in normal tissue and promote development of cardiac arrhythmias in pathological states. Recent studies demonstrate that PKA activation increases cardiac Na ϩ currents, although the mechanism of this effect is unknown. To explore the molecular basis of Na ϩ channel modulation by ␤-adrenergic receptors, we have examined the effects of PKA activation on the recombinant human cardiac Na ϩ channel, hH1. Both in the absence and the presence of h␤ 1 subunit coexpression, activation of PKA caused a slow increase in Na ϩ current that did not saturate despite kinase stimulation for 1 hour. In addition, there was a small shift in the voltage dependence of channel activation and inactivation to more negative voltages. Chloroquine and monensin, compounds that disrupt plasma membrane recycling, reduced hH1 current, suggesting rapid turnover of channels at the cell surface. Preincubation with these agents also prevented the PKA-mediated rise in Na ϩ current, indicating that this effect likely resulted from an increased number of Na ϩ channels in the plasma membrane. Experiments using chimeric constructs of hH1 and the skeletal muscle Na ϩ channel, hSKM1, identified the I-II interdomain loop of hH1 as the region responsible for the PKA effect. These results demonstrate that activation of PKA modulates both trafficking and function of the hH1 channel, with changes in Na ϩ current that could either speed or slow conduction, depending on the physiological circumstances. (Circ Res. 2000;87:33-38.) Key Words: sodium channels Ⅲ protein kinases Ⅲ heart V oltage-gated Na ϩ channels play a pivotal role in the normal conduction of electrical impulses in the heart. In addition, dysfunction of Na ϩ channels can cause lifethreatening cardiac arrhythmias by slowing impulse conduction 1 or prolonging cardiac repolarization. 2 Thus, the factors that regulate Na ϩ channel function are of great interest from both a pathophysiological and a therapeutic standpoint. Neurohumoral stimulation of ␤-adrenergic receptors, which activate cAMP-dependent protein kinase (protein kinase A [PKA]), can modulate cardiac electrophysiology and enhance conduction in normal ventricular myocardium. 3,4 On the other hand, adrenergic stimulation is a potent stimulus for arrhythmic events in both the congenital long-QT syndrome 2 and cardiomyopathic states. 5 It is likely that modulation of ion channel function plays a role in this arrhythmogenesis.The effects of ␤-adrenergic receptor stimulation on cardiac Na ϩ channel function have been controversial because of conflicting results of previous studies. More recent studies using rat ventricular myocytes have demonstrated a consistent increase in I Na with PKA stimulation, 6,7 with similar results obtained using recombinant cardiac Na ϩ channels. After expression in Xenopus...

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Section: Discussionmentioning

confidence: 99%

Activation of Protein Kinase A Modulates Trafficking of the Human Cardiac Sodium Channel in Xenopus Oocytes

Zhou

et al. 2000

Circulation Research

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“…3B) did not significantly affect the degree of channel recovery at any concentration of MgATP. It has previously been reported from our laboratory that the catalytic subunit of PKA harvested from porcine cardiac muscle inhibits sodium channel activity in isolated guinea-pig ventricular myocytes (Sunami et al 1991 as a substitute for protein kinases in the phosphorylation of target proteins, but the transferred thiophosphate is not readily removed by protein phosphatases (Eckstein, 1985). As shown in Fig.…”

Section: Methods Preparationmentioning

confidence: 96%

Mechanism for reactivation of the ATP‐sensitive K+ channel by MgATP complexes in guinea‐pig ventricular myocytes.

Furukawa

Virág

Furukawa

et al. 1994

The Journal of Physiology

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1. A mechanism underlying reactivation of the adenosine 5'-triphosphate-sensitive K+ (KATP) channels by MgATP complexes after run-down was examined in guinea-pig ventricular myocytes using the patch-clamp technique with inside-out patch configuration. 2. After run-down was induced by exposure of the intracellular side of the membrane patch to Ca2+ (1 mM), channel activity was reactivated by exposure and subsequent wash-out of MgATP (2 mM). Addition of inhibitors of various serine/threonine protein kinases to the MgATP solution did not suppress reactivation of the run-down channels. 3. Non-or poorly hydrolysable ATP analogues were unable to reactivate run-down channels. 4. The degree of channel recovery was dependent upon the duration of MgATP exposure.The apparent half-activation value (K%) of MgATP for reactivation was decreased with increasing exposure time. 5. Various products of ATP hydrolysis were unable to reactivate run-down channels except a relatively low concentration (100 /M) of ADP exposure. 6. Other nucleotide triphosphates, in the presence of Mg2+, were unable to reactivate rundown channels.7. Fluorescein 5-isothiocyanate (50 /uM), which interacts with lysine residues of the nucleotide-binding site on various ATPases, inhibited KATP channel activity. After wash-out, channel activity recovered only slightly. 8. These data suggest that the hydrolysis of ATP is important for reactivation of rundown KATP channels but that protein phosphorylation by serine/threonine protein kinases may not be involved. Since no products of ATP hydrolysis could reproduce MgATP-induced channel reactivation and since the degree of channel recovery was dependent upon the duration of MgATP application, the hydrolysis energy appears to be utilized for channel reactivation.

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“…29,30 Using heterologous expression of cardiac Na ϩ channels in Xenopus oocytes and mammalian cell line, activation of PKA has been reported to increase I Na derived from both the rat (rH1) and human (hH1) channels. [31][32][33] In contrast, other studies have shown an inhibition of cardiac I Na via PKA activation in guinea pig ventricular myocytes 16,34 and neonatal rat cardiac myocytes. 35 The effects of PKA activation may be speciesspecific.…”

Section: Effects Of Camp Modulation On I Namentioning

confidence: 99%

“…Consistent with our results in the present studies, PKA activation has been documented to inhibit the cardiac I Na in guinea pig ventricular myocytes. 16,34 In addition, the differences observed could result from data obtained in the native versus expression system. [31][32][33] Previous evidence has suggested that ␤-adrenergic receptor-activated modulation of cardiac I Na can occur via both a fast direct G-protein activation as well as by the slower indirect phosphorylation pathway.…”

Section: Effects Of Camp Modulation On I Namentioning

confidence: 99%

Nitric Oxide Modulates Cardiac Na ⁺ Channel via Protein Kinase A and Protein Kinase G

Ahmmed

Dong

et al. 2001

Circulation Research

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Abstract-We directly tested the effects of nitric oxide (NO) on Na ϩ channels in guinea pig and mouse ventricular myocytes using patch-clamp recordings. We have previously shown that NO donors have no observed effects on expressed Na ϩ channels. In contrast, NO (half-blocking concentration of 523 nmol/L) significantly reduces peak whole-cell Na ϩ current (I Na ) in isolated ventricular myocytes. The inhibitory effect of NO on I Na was not associated with changes in activation, inactivation, or reactivation kinetics. At the single-channel level, the reduction in macroscopic current was mediated by a decrease in open probability and/or a decrease in the number of functional channels with no change in single-channel conductance. Application of cell permeable analogs of cGMP or cAMP mimics the inhibitory effects of NO. Furthermore, the effects of NO on I Na can only be blocked by inhibition of both cGMP and cAMP pathways. Sulfhydryl-reducing agent does not reverse the effect of NO. In summary, although NO exerts its action via the known guanylyl cyclase (GC)/cGMP pathway, our findings provide evidence that NO can mediate its function via a GC/cGMP-independent mechanism involving the activation of adynylyl cyclase (AC) and cAMP-dependent protein kinase. Key Words: nitric oxide Ⅲ cardiac Na ϩ current Ⅲ protein kinase A Ⅲ protein kinase G N itric oxide (NO) is a uniquely diffusible and reactive molecular messenger, which is found in abundance and plays important regulatory roles in different systems throughout the body. 1 In the cardiovascular system, NO is the major endothelium-derived relaxing factor (EDRF) and causes vasodilation and reduces blood pressure. 2 In addition, NO functions as an important endogenous inhibitor of vascular lesion formation. 3 The coronary endothelium is responsible for the bulk of the endogenous, physiological production of NO. 4 However, NO can also be produced within the cardiac myocytes themselves by the constitutive NO synthase. 5 NO modulates cardiac contractility both in vitro and in vivo. 6 More recently, it was shown that NO can regulate both adenylyl cyclase (AC) and guanylyl cyclase (GC) in cardiac myocytes. High levels of NO induce large increases in cGMP and a negative inotropic effect, whereas low levels of NO increase cAMP and induce a positive contractile response. 7 We have previously shown using heterologous expression systems that although Ca 2ϩ channel can be directly modulated by NO, Na ϩ channels are unaffected by direct NO modulation. 8 Here, we show that NO modulates Na ϩ channels in native cardiac myocytes. In addition, we provide evidence to demonstrate that NO modulates Na ϩ channels via second messenger pathways through activation of protein kinase G (PKG) and protein kinase A (PKA). Materials and MethodsSingle left ventricular myocytes were isolated from guinea pigs and mice (Charles River Laboratories, Wilmington, Mass) as previously described. 9 See further details in the expanded Materials and Methods section that can be found in the online data supplement av...

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The catalytic subunit of cyclic AMP-dependent protein kinase directly inhibits sodium channel activities in guinea-pig ventricular myocytes

Cited by 33 publications

References 10 publications

Activation of Protein Kinase A Modulates Trafficking of the Human Cardiac Sodium Channel in Xenopus Oocytes

Activation of Protein Kinase A Modulates Trafficking of the Human Cardiac Sodium Channel in Xenopus Oocytes

Mechanism for reactivation of the ATP‐sensitive K+ channel by MgATP complexes in guinea‐pig ventricular myocytes.

Nitric Oxide Modulates Cardiac Na ⁺ Channel via Protein Kinase A and Protein Kinase G

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The catalytic subunit of cyclic AMP-dependent protein kinase directly inhibits sodium channel activities in guinea-pig ventricular myocytes

Cited by 33 publications

References 10 publications

Activation of Protein Kinase A Modulates Trafficking of the Human Cardiac Sodium Channel in Xenopus Oocytes

Activation of Protein Kinase A Modulates Trafficking of the Human Cardiac Sodium Channel in Xenopus Oocytes

Mechanism for reactivation of the ATP‐sensitive K+ channel by MgATP complexes in guinea‐pig ventricular myocytes.

Nitric Oxide Modulates Cardiac Na + Channel via Protein Kinase A and Protein Kinase G

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Nitric Oxide Modulates Cardiac Na ⁺ Channel via Protein Kinase A and Protein Kinase G