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

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

Despite its importance for the regulation of heart function, little is known about the isoform expression of the multifunctional Ca2+/calmodulin-dependent protein kinase (CaMKII) in human myocardium. In this study, we investigated the spectrum of CaMKII isoforms delta2, delta3, delta4, delta8, and delta9 in human striated muscle tissue. Isoform delta3 is characteristically expressed in cardiac muscle. In skeletal muscle, specific expression of a new isoform termed delta11 is demonstrated. Complete sequencing of human delta2 cDNA, representing all common features of the investigated CaMKII subclass, revealed its high homology to the corresponding rat cDNA. Comparative semiquantitative reverse transcription-polymerase chain reaction analyses from left ventricular tissues of normal hearts and from patients suffering from dilated cardiomyopathy showed a significant increase in transcript levels of isoform delta3 relative to the expression of glyceraldehyde-3-phosphate dehydrogenase in diseased hearts (101. 6+/-11.0% versus 64.9+/-9.9% in the nonfailing group; P<0.05, n=6). Transcript levels of the other investigated cardiac CaMKII isoforms remained unchanged. At the protein level, by using a subclass-specific antibody, we observed a similar increase of a delta-CaMKII-specific signal (7.2+/-1.0 versus 3.8+/-0.7 optical density units in the nonfailing group; P<0.05, n=4 through 6). The diseased state of the failing hearts was confirmed by a significant increase in transcript levels for atrial natriuretic peptide (292. 9+/-76.4% versus 40.1+/-3.2% in the nonfailing group; P<0.05, n=3 through 6). Our data characterize for the first time the delta-CaMKII isoform expression pattern in human hearts and demonstrate changes in this expression pattern in heart failure.
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PMID:Identification and expression of delta-isoforms of the multifunctional Ca2+/calmodulin-dependent protein kinase in failing and nonfailing human myocardium. 1018 59

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

Phospholamban is a small integral membrane protein of cardiac, smooth, and slow-twitch skeletal muscle sarcoplasmic reticulum that interacts with the Ca2+ pump of these organelles and inhibits Ca(2+)-pump activity while in the dephosphorylated form. Three sites of Ser/Thr phosphorylation have been identified in the primary sequence of phospholamban, at Ser-10, Ser-16, and Thr-17. In vitro studies indicate that these residues are phosphorylated by PKC (Ser-10), PKA, PKG or PKC (Ser-16), and CaM kinase II (Thr-17). Phosphorylation of Ser-16 (or Thr-17) is accompanied by an increase in Ca2+ pump activity in direct proportion to the stoichiometry of phosphorylation. Dual phosphorylation of both Ser-16 and Thr-17 does not cause any further stimulation of pump function over that achieved by stoichiometric phosphorylation of a single site. Examination of the pattern of phosphorylation in vivo has been aided by the generation of polyclonal antibodies specific for the phosphorylated forms of phospholamban. beta-Adrenergic stimulation of cardiac muscle results in phosphorylation of both Ser-16 and Thr-17. The time course of Ser-16 phosphorylation precedes Thr-17. The spatial distribution of Ser-16 and Thr-17 phosphorylated forms of phospholamban is not identical; phospholamban located in the nuclear membrane of a cardiac myocyte is phosphorylated exclusively on Ser-16, whereas phospholamban molecules in the SR membrane of the same cell are phosphorylated on Ser-16 and/or Thr-17. Finally, we have identified a novel stimulus for the phosphorylation of phospholamban. Ca2+ store depletion, achieved by exposure of myocytes to SERCA inhibitors, prompts the phosphorylation of phospholamban on Ser-16. This would be expected to increase Ca2+ uptake by the SR in an attempt to achieve the refilling of the SR.
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PMID:Phosphorylation states of phospholamban. 1060 38

It has been suggested that the activity of Ca2+/calmodulin-dependent protein kinase II (CaMKII) increases during acidosis in cardiac muscle. Thus we have investigated the role of CaMKII during acidosis by monitoring intracellular Ca2+ (using fura-2) and ICa (using the perforated patch clamp technique) during acidosis, in the absence and presence of the CaMKII inhibitor KN-93, in rat isolated ventricular myocytes. In the absence of KN-93, acidosis (pH 6.5) increased the amplitude of the fura-2 transient and prolonged its decay, but in the presence of KN-93 acidosis did not alter the amplitude and prolonged the decay more. In the absence of KN-93, acidosis increased the amplitude of the caffeine-induced fura-2 transient but did not alter its amplitude in the presence of KN-93. ICa did not change significantly during acidosis in the absence of KN-93 but decreased during acidosis in the presence of KN-93. These results suggest that activation of CaMKII during acidosis helps to compensate for the direct inhibitory effects of acidosis on sarcoplasmic reticular Ca2+ uptake and ICa.
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PMID:Compensatory role of CaMKII on ICa and SR function during acidosis in rat ventricular myocytes. 1148 65

The ryanodine receptor of cardiac muscle performs a central role in excitation-contraction coupling. Phosphorylation of the channel on serine 2809 (in rabbit or the corresponding serine 2808 in man) alters function in vitro, although the impact of this in vivo has not been established. We have produced a pair of antisera to the serine 2809 phosphorylation site to aid description of the incidence and consequence of phosphorylation of this receptor. One of these antisera is specific for the serine 2809 phosphorylated form of the cardiac ryanodine receptor; the other antiserum is specific for the serine 2809 dephosphorylated receptor. These antibodies have been used to demonstrate that both protein kinase A and calmodulin-dependent kinase II are capable of phosphorylating serine 2809 in vitro. Both kinases phosphorylate serine 2809 to full stoichiometry, but this is accompanied by the incorporation of more (radioactive) phosphate into the receptor by calmodulin-dependent kinase II than by protein kinase A. These data suggest that calmodulin-dependent kinase II phosphorylates at least four sites in addition to serine 2809 in vitro.
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PMID:Stoichiometric phosphorylation of cardiac ryanodine receptor on serine 2809 by calmodulin-dependent kinase II and protein kinase A. 1451 95

Intracellular Ca(2+) plays an important role in skeletal muscle excitation-contraction coupling and also in excitation-transcription coupling. Activity-dependent alterations in muscle gene expression as a result of increased load (i.e. resistance or endurance training) or decreased activity (i.e. immobilization or injury) are tightly linked to the level of muscle excitation. Differential expression of genes in slow- and fast-twitch fibres is also dependent on fibre activation. Both these biological phenomena are, therefore, tightly linked to the amplitude and duration of the Ca(2+) transient, a signal decoded downstream by Ca(2+)-dependent transcriptional pathways. Evidence is mounting that the calcineurin-nuclear factor of activated T-cells pathway and the Ca(2+)/calmodulin-dependent kinases (CaMK) II and IV play important roles in regulating oxidative enzyme expression, mitochondrial biogenesis and expression of fibre-type specific myofibrillar proteins. CaMKII is known to decode frequency-dependent information and is activated during hypertrophic growth and endurance adaptations. Thus, it was hypothesized that CaMKII, and possibly CaMKIV, are down regulated during muscle atrophy and levels of expression of CaMKII alpha, -II beta, -II gamma and -IV were assessed in skeletal muscles from young, aged and denervated rats. The results indicate that CaMKII gamma, but not CaMKIIalpha or -beta, is up regulated in aged and denervated soleus muscle and that CaMKIV is absent in skeletal but not cardiac muscle. Whether CaMKII gamma up-regulation is part of the pathology of wasting or a result of some adaptational response to atrophy is not known. Future studies will be important in determining whether insights from the adaptational response of muscle to increased loads will provide pharmacological approaches for increasing muscle strength or endurance to counter muscle wasting.
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PMID:The role of calcium and calcium/calmodulin-dependent kinases in skeletal muscle plasticity and mitochondrial biogenesis. 1529 44

Calcium (Ca) is a multifunctional regulator of diverse cellular functions. In cardiac muscle Ca is a direct central mediator of electrical activation, ion channel gating, and excitation-contraction (E-C) coupling that all occur on the millisecond time scale. The key amplification step in E-C coupling is under tight control of very local [Ca]. Ca also directly activates signaling via kinases and phosphatases (e.g., Ca-calmodulin-dependent protein kinase [CaMKII] and calcineurin) that occur over a longer time scale (seconds to minutes), and the co-localization of these Ca-dependent modulators to their targets and to Ca is also critical in distinct signaling pathways. Finally, Ca-dependent signaling is also involved in long-term (minutes to hours/days) alterations in gene expression (or excitation-transcription coupling). These pathways are involved in hypertrophy and heart failure, and they can alter the expression of some of the key Ca regulatory proteins involved in E-C coupling and their regulation by kinases and phosphatases. There may again be physical microenvironments involved in this nuclear transcription, such that they sense a discrete Ca signal that is distinct from that involved in E-C coupling. In this way cells can use Ca signaling in multiple ways that function in spatially and temporally distinct manners.
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PMID:Calcium signaling in cardiac ventricular myocytes. 1609 87

Class II histone deacetylases (HDAC4, HDAC5, HDAC7 and HDAC9) have been shown to interact with myocyte enhancer factors 2 (MEF2s) and play an important role in the repression of cardiac hypertrophy. We examined the role of HDACs during the differentiation of P19 embryonic carcinoma stem cells into cardiomyocytes. Treatment of aggregated P19 cells with the HDAC inhibitor trichostatin A induced the entry of mesodermal cells into the cardiac muscle lineage, shown by the upregulation of transcripts Nkx2-5, MEF2C, GATA4 and cardiac alpha-actin. Furthermore, the overexpression of HDAC4 inhibited cardiomyogenesis, shown by the downregulation of cardiac muscle gene expression. Class II HDAC activity is inhibited through phosphorylation by Ca2+/calmodulin-dependent kinase (CaMK). Expression of an activated CaMKIV in P19 cells upregulated the expression of Nkx2-5, GATA4 and MEF2C, enhanced cardiac muscle development, and activated a MEF2-responsive promoter. Moreover, inhibition of CaMK signaling downregulated GATA4 expression. Finally, P19 cells constitutively expressing a dominant-negative form of MEF2C, capable of binding class II HDACs, underwent cardiomyogenesis more efficiently than control cells, implying the relief of an inhibitor. Our results suggest that HDAC activity regulates the specification of mesoderm cells into cardiomyoblasts by inhibiting the expression of GATA4 and Nkx2-5 in a stem cell model system.
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PMID:HDAC activity regulates entry of mesoderm cells into the cardiac muscle lineage. 1703 45

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


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