EC:2.7.11.17 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.17 (CaMKII)
4,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Regulation of intracellular Ca(2+) concentration ([Ca(2+)](i)) in airway smooth muscle (ASM) during agonist stimulation involves sarcoplasmic reticulum (SR) Ca(2+) release and reuptake. The sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) is key to replenishment of SR Ca(2+) stores. We examined regulation of SERCA in porcine ASM: our hypothesis was that the regulatory protein phospholamban (PLN) and the calmodulin (CaM)-CaM kinase (CaMKII) pathway (both of which are known to regulate SERCA in cardiac muscle) play a role. In porcine ASM microsomes, we examined the expression and extent of PLN phosphorylation after pharmacological inhibition of CaM (with W-7) vs. CaMKII (with KN-62/KN-93) and found that PLN is phosphorylated by CaMKII. In parallel experiments using enzymatically dissociated single ASM cells loaded with the Ca(2+) indicator fluo 3 and imaged using fluorescence microscopy, we measured the effects of PLN small interfering RNA, W-7, and KN-62 on [Ca(2+)](i) responses to ACh and direct SR stimulation. PLN small interfering RNA slowed the rate of fall of [Ca(2+)](i) transients to 1 microM ACh, as did W-7 and KN-62. The two inhibitors additionally slowed reuptake in the absence of PLN. In other cells, preexposure to W-7 or KN-62 did not prevent initiation of ACh-induced [Ca(2+)](i) oscillations (which were previously shown to result from repetitive SR Ca(2+) release/reuptake). However, when ACh-induced [Ca(2+)](i) oscillations reached steady state, subsequent exposure to W7 or KN-62 decreased oscillation frequency and amplitude and slowed the fall time of [Ca(2+)](i) transients, suggesting SERCA inhibition. Exposure to W-7 completely abolished ongoing ACh-induced [Ca(2+)](i) oscillations in some cells. Preexposure to W-7 or KN-62 did not affect caffeine-induced SR Ca(2+) release, indicating that ryanodine receptor channels were not directly inhibited. These data indicate that, in porcine ASM, the CaM-CaMKII pathway regulates SR Ca(2+) reuptake, potentially through altered PLN phosphorylation.
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PMID:Regulation of sarcoplasmic reticulum Ca2+ reuptake in porcine airway smooth muscle. 1824 64

Transient outward K+ current (I to) downregulation following sustained tachycardia in vivo is usually attributed to tachycardiomyopathy. This study assessed potential direct rate regulation of cardiac I(to) and underlying mechanisms. Cultured adult canine left ventricular cardiomyocytes (37 degrees C) were paced continuously at 1 or 3 Hz for 24 hours. I to was recorded with whole-cell patch clamp. The 3-Hz pacing reduced I to by 44% (P<0.01). Kv4.3 mRNA and protein expression were significantly reduced (by approximately 30% and approximately 40%, respectively) in 3-Hz paced cells relative to 1-Hz cells, but KChIP2 expression was unchanged. Prevention of Ca2+ loading with nimodipine or calmodulin inhibition with W-7, A-7, or W-13 eliminated 3-Hz pacing-induced I to downregulation, whereas downregulation was preserved in the presence of valsartan. Inhibition of Ca2+/calmodulin-dependent protein kinase (CaMK)II with KN93, or calcineurin with cyclosporin A, also prevented I to downregulation. CaMKII-mediated phospholamban phosphorylation at threonine 17 was increased in 3-Hz paced cells, compatible with enhanced CaMKII activity, with functional significance suggested by acceleration of the Ca2+i transient decay time constant (Indo 1-acetoxymethyl ester microfluorescence). Total phospholamban expression was unchanged, as was expression of Na+/Ca2+ exchange and sarcoplasmic reticulum Ca2+-ATPase proteins. Nuclear localization of the calcineurin-regulated nuclear factor of activated T cells (NFAT)c3 was increased in 3-Hz paced cells compared to 1-Hz (immunohistochemistry, immunoblot). INCA-6 inhibition of NFAT prevented I to reduction in 3-Hz paced cells. Calcineurin activity increased after 6 hours of 3-Hz pacing. CaMKII inhibition prevented calcineurin activation and NFATc3 nuclear translocation with 3-Hz pacing. We conclude that tachycardia downregulates I to expression, with the Ca2+/calmodulin-dependent CaMKII and calcineurin/NFAT systems playing key Ca2+-sensing and signal-transducing roles in rate-dependent I to control.
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PMID:Mechanisms underlying rate-dependent remodeling of transient outward potassium current in canine ventricular myocytes. 1881 10

Returning to normal pH after acidosis, similar to reperfusion after ischemia, is prone to arrhythmias. The type and mechanisms of these arrhythmias have never been explored and were the aim of the present work. Langendorff-perfused rat/mice hearts and rat-isolated myocytes were subjected to respiratory acidosis and then returned to normal pH. Monophasic action potentials and left ventricular developed pressure were recorded. The removal of acidosis provoked ectopic beats that were blunted by 1 muM of the CaMKII inhibitor KN-93, 1 muM thapsigargin, to inhibit sarcoplasmic reticulum (SR) Ca(2+) uptake, and 30 nM ryanodine or 45 muM dantrolene, to inhibit SR Ca(2+) release and were not observed in a transgenic mouse model with inhibition of CaMKII targeted to the SR. Acidosis increased the phosphorylation of Thr(17) site of phospholamban (PT-PLN) and SR Ca(2+) load. Both effects were precluded by KN-93. The return to normal pH was associated with an increase in SR Ca(2+) leak, when compared with that of control or with acidosis at the same SR Ca(2+) content. Ca(2+) leak occurred without changes in the phosphorylation of ryanodine receptors type 2 (RyR2) and was blunted by KN-93. Experiments in planar lipid bilayers confirmed the reversible inhibitory effect of acidosis on RyR2. Ectopic activity was triggered by membrane depolarizations (delayed afterdepolarizations), primarily occurring in epicardium and were prevented by KN-93. The results reveal that arrhythmias after acidosis are dependent on CaMKII activation and are associated with an increase in SR Ca(2+) load, which appears to be mainly due to the increase in PT-PLN.
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PMID:Increased intracellular Ca2+ and SR Ca2+ load contribute to arrhythmias after acidosis in rat heart. Role of Ca2+/calmodulin-dependent protein kinase II. 1872 72

Activation of the sarcolemmal Na(+)/H(+) exchanger (NHE)1 is increasingly documented as a process involved in cardiac hypertrophy and heart failure. However, whether NHE1 activation alone is sufficient to induce such remodeling remains unknown. We generated transgenic mice that overexpress a human NHE1 with high activity in hearts. The hearts of these mice developed cardiac hypertrophy, contractile dysfunction, and heart failure. In isolated transgenic myocytes, intracellular pH was elevated in Hepes buffer but not in physiological bicarbonate buffer, yet intracellular Na(+) concentrations were higher under both conditions. In addition, both diastolic and systolic Ca(2+) levels were increased as a consequence of Na(+)-induced Ca(2+) overload; this was accompanied by enhanced sarcoplasmic reticulum Ca(2+) loading via Ca(2+)/calmodulin-dependent protein kinase (CaMK)II-dependent phosphorylation of phospholamban. Negative force-frequency dependence was observed with preservation of high Ca(2+), suggesting a decrease in myofibril Ca(2+) sensitivity. Furthermore, the Ca(2+)-dependent prohypertrophic molecules calcineurin and CaMKII were highly activated in transgenic hearts. These effects observed in vivo and in vitro were largely prevented by the NHE1 inhibitor cariporide. Interestingly, overexpression of NHE1 in neonatal rat ventricular myocytes induced cariporide-sensitive nuclear translocation of NFAT (nuclear factor of activated T cells) and nuclear export of histone deacetylase 4, suggesting that increased Na(+)/H(+) exchange activity can alter hypertrophy-associated gene expression. However, in transgenic myocytes, contrary to exclusive translocation of histone deacetylase 4, NFAT only partially translocated to nucleus, possibly because of marked activation of p38, a negative regulator of NFAT signaling. We conclude that activation of NHE1 is sufficient to initiate cardiac hypertrophy and heart failure mainly through activation of CaMKII-histone deacetylase pathway.
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PMID:Activation of Na+/H+ exchanger 1 is sufficient to generate Ca2+ signals that induce cardiac hypertrophy and heart failure. 1877 42

Recently, we identified a novel signaling pathway involving Epac, Rap, and phospholipase C (PLC)epsilon that plays a critical role in maximal beta-adrenergic receptor (betaAR) stimulation of Ca2+-induced Ca2+ release (CICR) in cardiac myocytes. Here we demonstrate that PLCepsilon phosphatidylinositol 4,5-bisphosphate hydrolytic activity and PLCepsilon-stimulated Rap1 GEF activity are both required for PLCepsilon-mediated enhancement of sarcoplasmic reticulum Ca2+ release and that PLCepsilon significantly enhances Rap activation in response to betaAR stimulation in the heart. Downstream of PLCepsilon hydrolytic activity, pharmacological inhibition of PKC significantly inhibited both betaAR- and Epac-stimulated increases in CICR in PLCepsilon+/+ myocytes but had no effect in PLCepsilon-/- myocytes. betaAR and Epac activation caused membrane translocation of PKCepsilon in PLCepsilon+/+ but not PLCepsilon-/- myocytes and small interfering RNA-mediated PKCepsilon knockdown significantly inhibited both betaAR and Epac-mediated CICR enhancement. Further downstream, the Ca2+/calmodulin-dependent protein kinase II (CamKII) inhibitor, KN93, inhibited betaAR- and Epac-mediated CICR in PLCepsilon+/+ but not PLCepsilon-/- myocytes. Epac activation increased CamKII Thr286 phosphorylation and enhanced phosphorylation at CamKII phosphorylation sites on the ryanodine receptor (RyR2) (Ser2815) and phospholamban (Thr17) in a PKC-dependent manner. Perforated patch clamp experiments revealed that basal and betaAR-stimulated peak L-type current density are similar in PLCepsilon+/+ and PLCepsilon-/- myocytes suggesting that control of sarcoplasmic reticulum Ca2+ release, rather than Ca2+ influx through L-type Ca2+ channels, is the target of regulation of a novel signal transduction pathway involving sequential activation of Epac, PLCepsilon, PKCepsilon, and CamKII downstream of betaAR activation.
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PMID:Epac and phospholipase Cepsilon regulate Ca2+ release in the heart by activation of protein kinase Cepsilon and calcium-calmodulin kinase II. 1895 19

MicroRNAs are small endogenous noncoding RNAs that regulate protein expression by hybridization to imprecise complementary sequences of target mRNAs. Changes in abundance of muscle-specific microRNA, miR-1, have been implicated in cardiac disease, including arrhythmia and heart failure. However, the specific molecular targets and cellular mechanisms involved in the action of miR-1 in the heart are only beginning to emerge. In this study we investigated the effects of increased expression of miR-1 on excitation-contraction coupling and Ca(2+) cycling in rat ventricular myocytes using methods of electrophysiology, Ca(2+) imaging and quantitative immunoblotting. Adenoviral-mediated overexpression of miR-1 in myocytes resulted in a marked increase in the amplitude of the inward Ca(2+) current, flattening of Ca(2+) transients voltage dependence, and enhanced frequency of spontaneous Ca(2+) sparks while reducing the sarcoplasmic reticulum Ca(2+) content as compared with control. In the presence of isoproterenol, rhythmically paced, miR-1-overexpressing myocytes exhibited spontaneous arrhythmogenic oscillations of intracellular Ca(2+), events that occurred rarely in control myocytes under the same conditions. The effects of miR-1 were completely reversed by the CaMKII inhibitor KN93. Although phosphorylation of phospholamban was not altered, miR-1 overexpression increased phosphorylation of the ryanodine receptor (RyR2) at S2814 (Ca(2+)/calmodulin-dependent protein kinase) but not at S2808 (protein kinase A). Overexpression of miR-1 was accompanied by a selective decrease in expression of the protein phosphatase PP2A regulatory subunit B56alpha involved in PP2A targeting to specialized subcellular domains. We conclude that miR-1 enhances cardiac excitation-contraction coupling by selectively increasing phosphorylation of the L-type and RyR2 channels via disrupting localization of PP2A activity to these channels.
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PMID:miR-1 overexpression enhances Ca(2+) release and promotes cardiac arrhythmogenesis by targeting PP2A regulatory subunit B56alpha and causing CaMKII-dependent hyperphosphorylation of RyR2. 1924 82

Airway inflammation leads to increased intracellular Ca(2+) ([Ca(2+)](i)) levels in airway smooth muscle (ASM) cells. Sarcoplasmic reticulum Ca(2+) release and reuptake are key components of ASM [Ca(2+)](i) regulation. Ca(2+) reuptake occurs via sarcoendoplasmic reticulum Ca(2+) ATPase (SERCA) and is regulated by the inhibitory protein phospholamban (PLB) in many cell types. In human ASM, we tested the hypothesis that inflammation increases PLB, thus inhibiting SERCA function, and leading to maintained [Ca(2+)](i) levels. Surprisingly, we found that human ASM does not express PLB protein (although mRNA is detectable). Overnight exposure to the proinflammatory cytokines TNFalpha and IL-13 did not induce PLB expression, raising the issue of how SERCA is regulated. We then found that direct SERCA phosphorylation (via CaMKII) occurs in human ASM. In fura-2-loaded human ASM cells, we found that the CaMKII antagonist KN-93 significantly slowed the rate of fall of [Ca(2+)](i) transients induced by ACh or bradykinin (in zero extracellular Ca(2+)), suggesting a role for CaMKII-mediated SERCA regulation. SERCA expression was decreased by cytokine exposure, and the rate of fall of [Ca(2+)](i) transients was slowed in cells exposed to TNFalpha and IL-13. Cytokine effects on Ca(2+) reuptake were unaffected by additional exposure to KN-93. These data indicate that in human ASM, SERCA is regulated by mechanisms such as CaMKII and that airway inflammation maintains [Ca(2+)](i) levels by decreasing SERCA expression and slowing Ca(2+) reuptake.
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PMID:Effect of proinflammatory cytokines on regulation of sarcoplasmic reticulum Ca2+ reuptake in human airway smooth muscle. 1978 41

Cytosolic Ca2+ transients associated with contraction and relaxation cycles in skeletal muscle are primarily dependent on the kinetics of Ca2+ release and Ca2+ uptake by the sarcoplasmic reticulum (SR). In humans, sarco(endo)plasmic reticulum Ca2+-ATPases (SERCAs) are solely responsible for the removal of Ca2+ from the cytosol following muscle contraction. There are several signalling systems involved in the acute regulation of SERCAs required to achieve a given Ca2+ transient during muscle contraction-relaxation cycles. Cyclic-AMP-dependent protein kinase and Ca2+/calmodulin-dependent protein kinase signalling activate SERCAs through the regulation of the endogenous SERCA-regulatory proteins, phospholamban and sarcolipin, both of which are highly expressed in human skeletal muscle. Recent studies on the regulation of SERCA2b in arterial smooth muscle and work from my laboratory on the interaction between SERCAs and the inducible 70-kDa heat shock protein suggests a novel role for redox signalling in regulating SERCA activity. In the absence of fatigue, activation of these signalling systems in response to repeated muscle activity serves to increase the rate of cytosolic free Ca2+ ([Ca2+]f) decay (i.e., SR Ca2+ uptake) and the speed of muscle relaxation.
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PMID:The decay phase of Ca2+ transients in skeletal muscle: regulation and physiology. 1944 1

Intermittent high-altitude (IHA) hypoxia-induced cardioprotection against ischemia-reperfusion (I/R) injury is associated with the preservation of sarcoplasmic reticulum (SR) function. Although Ca(2+)/calmodulin (CaM)-dependent protein kinase II (CaMKII) and phosphatase are known to modulate the function of cardiac SR under physiological conditions, the status of SR CaMKII and phosphatase during I/R in the hearts from IHA hypoxic rats is unknown. In the present study, we determined SR and cytosolic CaMKII activity during preischemia and I/R (30 min/30 min) in perfused hearts from normoxic and IHA hypoxic rats. The left ventricular contractile recovery, SR CaMKII activity as well as phosphorylation of phospholamban at Thr(17), and Ca(2+)/CaM-dependent SR Ca(2+)-uptake activity were depressed in the I/R hearts from normoxic rats, whereas these changes were prevented in the hearts from IHA hypoxic rats. Such beneficial effects of IHA hypoxia were lost by treating the hearts with a specific CaMKII inhibitor, KN-93. I/R also depressed cytosolic CaMKII and SR phosphatase activity, but these alterations remained unchanged in IHA hypoxic group. Furthermore, we found that the autophosphorylation at Thr(287), which confers Ca(2+)/CaM-independent activity, was not altered by I/R in both groups. These findings indicate that preservation of SR CaMKII activity plays an important role in the IHA hypoxia-induced cardioprotection against I/R injury via maintaining SR Ca(2+)-uptake activity.
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PMID:Calcium/calmodulin-dependent protein kinase II mediates cardioprotection of intermittent hypoxia against ischemic-reperfusion-induced cardiac dysfunction. 1952 72

The present study investigated cardiac function in hearts of mice with total deficiency of the beta1-, beta2- and beta3-adrenoceptors (TKO) in comparison to wildtype mice (WT). We investigated cardiac morphology and echocardiographic function, measured protein expression of Ca2+-regulatory proteins, SERCA 2a activity, myofibrillar function, and performed running wheel tests. Heart weight and heart-to-body weight ratio were significantly smaller in TKO as compared to WT. This was accompanied by a decrease in the size of the cardiomyocytes in TKO. Heart rate and ejection fraction were significantly diminished in TKO as compared to WT. Protein expressions of SERCA 2a, ryanodine receptor and Na+/Ca2)-exchanger were similar in TKO and WT mice, but phospholamban protein expression was increased. PKA-dependent phosphorylation of phospholamban at serine 16 was absent and CaMKII-dependent phosphorylation at threonine 17 was decreased in TKO. All alterations were paralleled by a decrease in SERCA 2a-activity. A similar maximal calcium-dependent tension but an increased myofibrillar calcium-sensitivity was measured in TKO as compared to WT. We did not observe relevant functional impairments of TKO in running wheel tests. In the absence of beta-agonistic stimulation, SERCA 2a activity is mainly regulated by alterations of phospholamban expression and phosphorylation. The decreased SERCA 2a activity following beta-adrenoceptor deficiency may be partly compensated by an increased myofibrillar calcium-sensitivity.
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PMID:Total beta-adrenoceptor deficiency results in cardiac hypotrophy and negative inotropy. 2040 48

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