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)

Despite their important role in controlling the cardiac Ca2+ homeostasis, presence and functions of individual isoforms of the multifunctional Ca2+/calmodulin-dependent protein kinase in the heart are not well studied. Here we report on expression of isoforms of the delta class in two differentiation states of the embryonic rat heart-derived cell line H9c2 compared to adult rat heart. Reverse transcription coupled polymerase chain reaction analysis revealed specific expression patterns of four variants of the delta class (delta B, delta C, delta 4, delta 9) in adult rat heart, H9c2 myoblasts, and skeletal muscle-like H9c2 myotubes. delta C was identified as a common isoform with higher amounts in H9c2 cells and the prominent one in myoblasts. In contrast, expression of delta 9 accompanied cardiac as well as skeletal muscle differentiation. Expression of delta B, however, was representative for differentiated cardiac muscle, whereas delta 4 expression coincided with differentiation into the skeletal muscle-like state. Our results demonstrate differentiation-dependent isoform expression of the delta class of the multifunctional Ca2+/calmodulin-dependent protein kinase of muscle. The identification of cardiac target proteins for this kinase, e.g. the alpha 1-subunit of the L-type Ca2+ channel, the sarcoplasmic reticulum Ca(2+)-ATPase, phospholamban and the ryanodine receptor define H9c2 myoblasts as a suitable model system for further functional characterization of the identified cardiac delta isoforms.
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PMID:Differentiation-dependent expression of cardiac delta-CaMKII isoforms. 944 81

Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) is present in a membrane-bound form that phosphorylates synapsin I on neuronal synaptic vesicles and the ryanodine receptor at skeletal muscle sarcoplasmic reticulum (SR), but it is unclear how this soluble enzyme is targeted to membranes. We demonstrate that alphaKAP, a non-kinase protein encoded by a gene within the gene of alpha-CaM kinase II, can target the CaM kinase II holoenzyme to the SR membrane. Our results indicate that alphaKAP (i) is anchored to the membrane via its N-terminal hydrophobic domain, (ii) can co-assemble with catalytically competent CaM kinase II isoforms and target them to the membrane regardless of their state of activation, and (iii) is co-localized and associated with rat skeletal muscle CaM kinase II in vivo. alphaKAP is therefore the first demonstrated anchoring protein for CaM kinase II. CaM kinase II assembled with alphaKAP retains normal enzymatic activity and the ability to become Ca2+-independent following autophosphorylation. A new variant of beta-CaM kinase II, termed betaM-CaM kinase II, is one of the predominant CaM kinase II isoforms associated with alphaKAP in skeletal muscle SR.
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PMID:alphaKAP is an anchoring protein for a novel CaM kinase II isoform in skeletal muscle. 975 60

Diminished Ca2+-sequestering activity of the sarcoplasmic reticulum (SR) is implicated in the age-associated slowing of cardiac muscle relaxation. In attempting to further define the underlying mechanisms, the present study investigated the impact of aging on the contents of major SR Ca2+-cycling proteins and SR protein phosphorylation by endogenous Ca2+/calmodulin-dependent protein kinase (CaM kinase). The studies were performed using homogenates and SR vesicles derived from the ventricular myocardium of adult (6-8 mo old) and aged (26-28 mo old) Fischer 344 rats. Western immunoblotting analysis showed no significant age-related difference in the relative amounts of ryanodine receptor-Ca2+-release channel (RyR-CRC), the Ca2+-storage protein calsequestrin, Ca2+-pumping ATPase (Ca2+-ATPase), and Ca2+-ATPase-regulatory protein phospholamban (PLB) in SR or homogenate. On the other hand, the relative amount of immunoreactive CaM kinase II (delta-isoform) was approximately 50% lower in the aged heart. CaM kinase-mediated phosphorylation of RyR-CRC, Ca2+-ATPase, and PLB was reduced significantly ( approximately 25-40%) in the aged compared with adult rat. ATP-dependent Ca2+-uptake activity of SR and the stimulatory effect of calmodulin on Ca2+ uptake were also reduced significantly with aging. Treatment of SR vesicles with anti-PLB antibody (PLBab) invoked relatively less stimulation of Ca2+ uptake in the aged (</=26%) compared with the adult (</=65%) rat. Ca2+-ATPase but not PLB underwent phosphorylation by CaM kinase in PLBab-treated SR with resultant stimulation of Ca2+ uptake. The rates of Ca2+ uptake by PLBab-treated SR were significantly lower (45-55%) in the aged compared with adult rat in the absence and presence of calmodulin. These findings imply that changes in the intrinsic functional properties of SR Ca2+-cycling proteins and/or their phosphorylation-dependent regulation contribute to impaired SR function in the aging heart.
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PMID:Effects of aging on sarcoplasmic reticulum Ca2+-cycling proteins and their phosphorylation in rat myocardium. 984 8

Recent studies have demonstrated phosphorylation of the cardiac and slow-twitch muscle isoform (SERCA2a) of the sarcoplasmic reticulum (SR) Ca2+-ATPase (at Ser38) by a membrane-associated Ca2+/calmodulin-dependent protein kinase (CaM kinase). Analysis of the functional consequence of Ca2+-ATPase phosphorylation in the native SR membranes, however, is complicated by the concurrent phosphorylation of the SR proteins phospholamban (PLN) which stimulates Ca2+ sequestration by the Ca2+-ATPase, and the ryanodine receptor-Ca2+ release channel (RYR-CRC) which likely augments Ca2+ release from the SR. In the present study, we achieved selective phosphorylation of the Ca2+-ATPase by endogenous CaM kinase in isolated rabbit cardiac SR vesicles utilizing a PLN monoclonal antibody (PLN AB) which inhibits PLN phosphorylation, and the RYR-CRC blocking drug, ruthenium red, which inhibits phosphorylation of RYR-CRC. Analysis of the Ca2+ concentration-dependence of ATP-energized Ca2+ uptake by SR showed that endogenous CaM kinase mediated phosphorylation of the Ca2+-ATPase, in the absence of PLN and/or RYR-CRC phosphorylation, results in a significant increase (approximately 50-70%) in the Vmax of Ca2+ sequestration without any change in the k0.5 for Ca2+ activation of the Ca2+ transport rate. On the other hand, treatment of SR with PLN AB (which mimics the effect of PLN phosphorylation by uncoupling Ca2+-ATPase from PLN) resulted in approximately 2-fold decrease in k0.5 for Ca2+ without any change in Vmax of Ca2+ sequestration. These findings suggest that, besides PLN phosphorylation, direct phosphorylation of the Ca2+-ATPase by SR-associated CaM kinase serves to enhance the speed of cardiac muscle relaxation.
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PMID:Ca2+/calmodulin-dependent phosphorylation of the Ca2+-ATPase, uncoupled from phospholamban, stimulates Ca2+-pumping in native cardiac sarcoplasmic reticulum. 1022 36

Glucose induces an increase in the intracellular Ca2+ concentration in pancreatic beta-cells to secrete insulin. CD38 occurs in beta-cells and has both ADP-ribosyl cyclase, which catalyzes the formation of cyclic ADP-ribose (cADPR) from NAD+, and cADPR hydrolase, which converts cADPR to ADP-ribose. ATP, produced by glucose metabolism, competes with cADPR for the binding site, Lys-129, of CD38, resulting in the inhibition of the hydrolysis of cADPR and thereby causing cADPR accumulation in beta-cells. Cyclic ADP-ribose then binds to FK506-binding protein 12.6 in the ryanodine receptor Ca2+ channel (RyR), dissociating the binding protein from RyR to induce the release of Ca2+ from the endoplasmic reticulum. Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) phosphorylates RyR to sensitize and activate the Ca2+ channel. Ca2+, released from the RyR, further activates CaM kinase II and amplifies the process. Thus, cADPR acts as a second messenger for Ca2+ mobilization to secrete insulin. The novel mechanism of insulin secretion described above is different from the conventional hypothesis in which Ca2+ influx from extracellular sources plays a role in insulin secretion by glucose.
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PMID:The CD38-cyclic ADP-ribose signaling system in insulin secretion. 1033 47

Glucose induces an increase in the intracellular Ca2+ concentration in pancreatic beta-cells to secrete insulin. CD38 exists in beta-cells and has both ADP-ribosyl cyclase, which catalyzes the formation of cyclic ADP-ribose (cADPR) from NAD+, and cADPR hydrolase, which converts cADPR to ADP-ribose. ATP, produced by glucose metabolism, competes with cADPR for the binding site, Lys-129, of CD38, resulting in the inhibition of the hydrolysis of cADPR and thereby causing cADPR accumulation in beta-cells. cADPR then binds to FK506-binding protein 12.6 (FKBP 12.6) in the islet type of the ryanodine receptor (RyR), dissociating the binding protein from RyR to induce the release of Ca2+ from the endoplasmic reticulum. Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) phosphorylates RyR to sensitize and activate the Ca2+ channel. Ca2+, released from the RyR, further activates CaM kinase II and amplifies this process. Thus, cADPR acts as a second messenger for Ca2+ mobilization to secrete insulin. The novel mechanism of insulin secretion described above is different from the conventional hypothesis in which Ca2+ influx from extracellular sources plays a role in insulin secretion by glucose. Furthermore, many physiological and pathological phenomena in various tissues and cells such as cardiac muscles, cerebellum, neuronal cells, pancreatic acinar cells, alveolar macrophages and immune B-cells become understandable in terms of "the CD38-cADPR signaling system" that sometimes acts in cooperation with other signal systems.
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PMID:["The CD38-cyclic ADP-ribose signal system": molecular mechanism and biological significance]. 1055 76

Calmodulin (CaM) and Ca(2+)/CaM-dependent protein kinase II (CaM kinase) are tightly associated with cardiac sarcoplasmic reticulum (SR) and are implicated in the regulation of transmembrane Ca(2+) cycling. In order to assess the importance of membrane-associated CaM in modulating the Ca(2+) pump (Ca(2+)-ATPase) function of SR, the present study investigated the effects of a synthetic, high affinity CaM-binding peptide (CaM BP; amino acid sequence, LKWKKLLKLLKKLLKLG) on the ATP-energized Ca(2+) uptake, Ca(2+)-stimulated ATP hydrolysis, and CaM kinase-mediated protein phosphorylation in rabbit cardiac SR vesicles. The results revealed a strong concentration-dependent inhibitory action of CaM BP on Ca(2+) uptake and Ca(2+)-ATPase activities of SR (50% inhibition at approximately 2-3 microM CaM BP). The inhibition, which followed the association of CaM BP with its SR target(s), was of rapid onset (manifested within 30 s) and was accompanied by a decrease in V(max) of Ca(2+) uptake, unaltered K(0.5) for Ca(2+) activation of Ca(2+) transport, and a 10-fold decrease in the apparent affinity of the Ca(2+)-ATPase for its substrate, ATP. Thus, the mechanism of inhibition involved alterations at the catalytic site but not the Ca(2+)-binding sites of the Ca(2+)-ATPase. Endogenous CaM kinase-mediated phosphorylation of Ca(2+)-ATPase, phospholamban, and ryanodine receptor-Ca(2+) release channel was also strongly inhibited by CaM BP. The inhibitory action of CaM BP on SR Ca(2+) pump function and protein phosphorylation was fully reversed by exogenous CaM (1-3 microM). A peptide inhibitor of CaM kinase markedly attenuated the ability of CaM to reverse CaM BP-mediated inhibition of Ca(2+) transport. These findings suggest a critical role for membrane-bound CaM in controlling the velocity of Ca(2+) pumping in native cardiac SR. Consistent with its ability to inhibit SR Ca(2+) pump function, CaM BP (1-2.5 microM) caused marked depression of contractility and diastolic dysfunction in isolated perfused, spontaneously beating rabbit heart preparations. Full or partial recovery of contractile function occurred gradually following withdrawal of CaM BP from the perfusate, presumably due to slow dissociation of CaM BP from its target sites promoted by endogenous cytosolic CaM.
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PMID:Reversible inhibition of the calcium-pumping ATPase in native cardiac sarcoplasmic reticulum by a calmodulin-binding peptide. Evidence for calmodulin-dependent regulation of the V(max) of calcium transport. 1066 Jun 12

To decipher the mechanism(s) underlying glucocorticoid action on cardiac contractile function, this study investigated the effects of adrenalectomy and dexamethasone treatment on the contents of sarcoplasmic reticulum (SR) Ca(2+)-cycling proteins, their phosphorylation by endogenous Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II), and SR Ca(2+) sequestration in the rat myocardium. Cardiac SR vesicles from adrenalectomized rats displayed significantly diminished rates of ATP-energized Ca(2+) uptake in vitro compared with cardiac SR vesicles from control rats; in vivo administration of dexamethasone to adrenalectomized rats prevented the decline in SR function. Western immunoblotting analysis showed that the relative protein amounts of ryanodine receptor/Ca(2+)-release channel, Ca(2+)-ATPase, calsequestrin, and phospholamban were neither diminished significantly by adrenalectomy nor elevated by dexamethasone treatment. However, the relative amount of SR-associated CaM kinase II protein was increased 2.5- to 4-fold in dexamethasone-treated rats compared with control and adrenalectomized rats. Endogenous CaM kinase II activity, as judged from phosphorylation of ryanodine receptor, Ca(2+)-ATPase, and phospholamban protein, was also significantly higher (50--80% increase) in the dexamethasone-treated rats. The stimulatory effect of CaM kinase II activation on Ca(2+) uptake activity of SR was significantly depressed after adrenalectomy and greatly enhanced after dexamethasone treatment. These findings identify the SR as a major target for glucocorticoid actions in the heart and implicate modification of the SR CaM kinase II system as a component of the mechanisms by which dexamethasone influences SR Ca(2+)-cycling and myocardial contraction.
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PMID:Glucocorticoid modulation of protein phosphorylation and sarcoplasmic reticulum function in rat myocardium. 1140

Recent studies have demonstrated that transgenic (TG) expression of either Ca2+/calmodulin-dependent protein kinase IV (CaMKIV) or CaMKIIdeltaB, both of which localize to the nucleus, induces cardiac hypertrophy. However, CaMKIV is not present in heart, and cardiomyocytes express not only the nuclear CaMKIIdeltaB but also a cytoplasmic isoform, CaMKIIdeltaC. In the present study, we demonstrate that expression of the deltaC isoform of CaMKII is selectively increased and its phosphorylation elevated as early as 2 days and continuously for up to 7 days after pressure overload. To determine whether enhanced activity of this cytoplasmic deltaC isoform of CaMKII can lead to phosphorylation of Ca2+ regulatory proteins and induce hypertrophy, we generated TG mice that expressed the deltaC isoform of CaMKII. Immunocytochemical staining demonstrated that the expressed transgene is confined to the cytoplasm of cardiomyocytes isolated from these mice. These mice develop a dilated cardiomyopathy with up to a 65% decrease in fractional shortening and die prematurely. Isolated myocytes are enlarged and exhibit reduced contractility and altered Ca2+ handling. Phosphorylation of the ryanodine receptor (RyR) at a CaMKII site is increased even before development of heart failure, and CaMKII is found associated with the RyR in immunoprecipitates from the CaMKII TG mice. Phosphorylation of phospholamban is also increased specifically at the CaMKII but not at the PKA phosphorylation site. These findings are the first to demonstrate that CaMKIIdeltaC can mediate phosphorylation of Ca2+ regulatory proteins in vivo and provide evidence for the involvement of CaMKIIdeltaC activation in the pathogenesis of dilated cardiomyopathy and heart failure.
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PMID:The deltaC isoform of CaMKII is activated in cardiac hypertrophy and induces dilated cardiomyopathy and heart failure. 1267 14

Nerve growth factor (NGF) was found to increase glutamate release in the developing visual cortex. We investigated the cellular mechanisms of this effect and its dependence on extracellular and intracellular Ca2+. The NGF-induced enhancement of glutamate release from superfused rat visual cortex synaptosomes required mild depolarization. Removal of external Ca2+ during depolarization with 15 mM K+ only halved the effect of NGF on glutamate release. NGF increased [Ca2+]i in K+-depolarized synaptosomes preloaded with fura-2AM both in the presence and in the absence of external Ca2+. The effects of NGF on glutamate release and [Ca2+]i elevation were prevented by an anti-TrkA receptor monoclonal antibody. NGF increased synaptosomal inositol (1,4,5)-triphosphate (InsP3) during depolarization and the InsP3 receptor antagonist heparin abolished the effect of NGF on evoked glutamate release both in the presence and in the absence of external Ca2+. The effect of NGF on the evoked glutamate release in Ca2+-free medium was abolished by dantrolene, a ryanodine receptor blocker, by CGP 37157, a blocker of the mitochondrial Na+/Ca2+ exchanger and by pretreatment of synaptosomes with caffeine. NGF significantly increased the depolarization-induced activation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and the subsequent phosphorylation of synapsin I in the absence of external Ca2+ and the NGF effect on evoked glutamate release was inhibited by the CaMKII inhibitors KN-93 and CaMKII 281-309 peptide but not by the MAP kinase inhibitor PD 98059. Thus, the effect of NGF on evoked glutamate release is linked to an increase in [Ca2+]i contributed by both Ca2+ entry and mobilization from InsP3-sensitive, ryanodine-sensitive and mitochondrial stores and to the subsequent activation of CaMKII.
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PMID:Cellular mechanisms of the acute increase of glutamate release induced by nerve growth factor in rat cerebral cortex. 1269 58


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