Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Na/Ca exchanger encoded by the NCX1 gene plays an important role in calcium homeostasis in cardiac muscle. We previously identified three in vitro signaling pathways that are of major importance in the regulation of Na/Ca exchanger gene expression in neonatal cardiac myocytes, the protein kinase A (PKA) and protein kinase C (PKC) pathways, and intracellular Ca(2+). To determine whether these pathways are important in vivo, we stimulated the PKA and PKC pathways and examined functional expression of the Na/Ca exchanger in adult rat heart. After a 3- and 7-day treatment, norepinephrine (200 microg x kg(-1) x h(-1)), isoproterenol (150 microg x kg(-1) x h(-1)), and phenylephrine (200 microg x kg(-1) x h(-1)) each stimulated a significant increase in NCX1 mRNA levels (35-85%, P < 0.05). Norepinephrine also stimulated a 35% increase in protein abundance (P < 0.05), a 20% decrease in relaxation duration (P < 0.05), and a 25% reduction in the fluorescence decay constant (P < 0.05) after a 7-day treatment. We conclude that a 7-day treatment of alpha- and beta-adrenergic agonists increases the expression of functional Na/Ca exchangers in adult rat heart.
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PMID:In vivo regulation of Na/Ca exchanger expression by adrenergic effectors. 1117 87

Protein kinase C-epsilon (PKC-epsilon) plays a central role in cardiac cell signaling, but mechanisms of translocation and anchoring upon activation are poorly understood. Conventional PKC isoforms rely on a rapid Ca2+-mediated recruitment to cell membranes, but this mechanism cannot be employed by PKC-epsilon or other PKC isoforms lacking a Ca2+-binding domain. In this study, we used recombinant green fluorescent protein (GFP) fusion constructs and confocal microscopy to examine the localization, kinetics, and reversibility of PKC-epsilon anchoring in permeabilized rat cardiac myocytes. PKC-epsilon-GFP bound with a striated pattern that co-localized with alpha-actinin, a marker of the Z-line of the sarcomere. Binding required activation of PKC and occurred slowly but reversibly with apparent rate constants of k(on) = 4.6 +/- 1.2 x 10(3) M(-1) x s(-1) and k(off) = 1.4 +/- 0.5 x 10(-3) s(-1) (t1/2 = 8 min) as determined by fluorescence recovery after photobleaching and by perfusion experiments. A truncated construct composed of the N-terminal 144-amino-acid variable region of PKC-epsilon (epsilonV1-GFP), but not an analogous N-terminal domain of PKC-delta, mimicked the Z-line decoration and slow binding rate of the full-length enzyme. These findings suggest that the epsilonV1 domain is important in determining PKC-epsilon localization and translocation kinetics in cardiac muscle. Moreover, PKC-epsilon translocation is not a diffusion-controlled binding process but instead may be limited by intramolecular conformational changes within the V1 domain. The k(off) for epsilonV1-GFP was two- to threefold faster than for full-length enzyme, indicating that other domains in PKC-epsilon contribute to anchoring by prolonging the bound state.
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PMID:Localization and kinetics of protein kinase C-epsilon anchoring in cardiac myocytes. 1132 17

We hypothesize that actin polymerization within vascular smooth muscle (VSM) in response to increased intravascular pressure is a novel and previously unrecognized mechanism underlying arterial myogenic behavior. This hypothesis is based on the following observations. 1) Unlike skeletal or cardiac muscle, VSM contains a substantial pool of unpolymerized globular (G) actin whose function is not known. 2) The cytosolic concentration of G-actin is significantly reduced by an elevation in intravascular pressure, demonstrating the dynamic nature of actin within VSM and implying a shift in the F:G equilibrium in favor of F-actin. 3) Agents that inhibit actin polymerization and stabilize the cytoskeleton (cytochalasins and latrunculin) inhibit the development of myogenic tone and decrease the effectiveness of myogenic reactivity. 4) Depolymerization of F-actin with cytochalasin D causes VSM relaxation and increased G-actin content, whereas polymerization of F-actin with jasplakinolide causes VSM contraction and decreased G-actin content. These results are consistent with observations in other cell types in which actin dynamics have been implicated in contractility and/or motility. Actin filament formation in VSM may therefore underlie mechanotransduction and, by providing additional sites for interaction with myosin, enhance force production in response to pressure. Although the mechanism by which actin polymerization is stimulated by pressure is not known, it likely occurs via integrin-mediated activation of signal transduction pathways previously associated with VSM contraction (e.g., PKC activation, Rho A, and tyrosine phosphorylation).
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PMID:Pressure-induced actin polymerization in vascular smooth muscle as a mechanism underlying myogenic behavior. 1177 38

Our previous study demonstrated that endothelin-1 induced a phosphorylation of GATA-4 transcription factor, which plays important roles in cardiac hypertrophy and failure. The goal of the present study was to determine whether protein kinase C (PKC) is involved in the signaling pathway, and, if so, whether alpha-tocopherol inhibits the GATA-4 phosphorylation. Treatment of HL-1 adult mouse cardiac muscle cells with PMA, a known activator of PKC, induced a transient phosphorylation of GATA-4. PMA also phosphorylated MEK and ERK, and PMA-induced GATA-4 phosphorylation was blocked by an MEK inhibitor, PD98059, suggesting that PMA phosphorylates GATA-4 via the MEK-ERK pathway. Treatment of HL-1 cells with 1 microM PMA for 24 h resulted in a downregulation of PKC. In PKC-downregulated cells, PMA- or ET-1-induced GATA-4 phosphorylation was suppressed, suggesting the role of PKC in GATA-4 phosphorylation. However, alpha-tocopherol (5--100 microM) did not inhibit the phosphorylation of GATA-4 or ERK in HL-1 cells. In contrast, alpha-tocopherol potently inhibited the PMA-induced ERK activation in smooth muscle cells. Our studies in HL-1 cells showed that PKC inhibitors, such as calphostin C and chelerythrin, failed to inhibit the PMA signaling. Furthermore, HL-1 cells appear to possess a unique PKC-signaling mechanism as PKC is constitutively phosphorylated and PMA did not cause further phosphorylation. Thus, in HL-1 cardiac muscle cells, PMA activates the MEK-ERK-GATA-4 pathway, apparently via a PKC-independent mechanism.
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PMID:Roles of protein kinase C and alpha-tocopherol in regulation of signal transduction for GATA-4 phosphorylation in HL-1 cardiac muscle cells. 1184 24

Desmosomes are adhesive intercellular junctions of epithelia and cardiac muscle. They have an essential function in maintaining the integrity of tissues, which is compromised in human genetic and autoimmune disease that targets desmosomal components. Recent evidence (1) suggests new roles for the function of desmosomal adhesion in tissue morphogenesis, (2) gives new insights into the molecular mechanism of adhesion, (3) indicates that the desmosomal adhesion molecules, desmocollin and desmoglein, may contribute to the regulation of epidermal diffentiation, and (4) shows that the affinity of desmosomal adhesion is regulated by protein kinase C.
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PMID:Desmosomal adhesion: structural basis, molecular mechanism and regulation (Review). 1212 34

The alpha1c subunit (DHP receptor) of the L-type Ca2+ channel is important for calcium homeostasis in cardiac muscle. The DHPr provides the primary mechanism for calcium influx during contraction. Published results demonstrate three in vitro signaling pathways that are important in the regulation of DHPr gene expression in neonatal cardiac myocytes, the protein kinase A (PKA), protein kinase C (PKC) pathways, and intracellular calcium. To determine whether these pathways are important in vivo, we treated adult rats with infusions of isoproterenol, or norepinephrine at 200 microg/kg/h and assessed DHPr mRNA and protein levels. Following a 3-day infusion isoproterenol (ISO) and norepinephrine (NE) produced a small but insignificant reduction in DHPr mRNA levels. When the infusions were continued for 7 days isoproterenol increased DHPr mRNA accumulation to control levels while NE stimulated a 35% increase in DHPr mRNA levels and a 35% increase in protein abundance when compared to controls (p < 0.05). Furthermore, contractility and Ca2+ transient measurements of isolated cardiac myocytes from NE infused animals also display shortened duration of contraction/relaxation and increased intracellular free Ca2+ (DFFI) in response to electrical stimulation (p < 0.01). We conclude norepinephrine treatment alters DHPr mRNA and protein levels, and augments excitation-contraction coupling, and thus may be important for modulating cardiac calcium homeostasis in vivo.
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PMID:Norepinephrine regulates the in vivo expression of the L-type calcium channel. 1219 Jan 8

Recent evidence suggests that opening of mitochondrial K(ATP) channels in cardiac muscle triggers the preconditioning phenomenon through free radical production. The present study tested the effects of K(ATP) channel openers in a vascular smooth muscle cell model using the fluorescent probe MitoTracker (MTR) Red trade mark for detection of reactive oxygen species (ROS). Rat aortic smooth muscle cells (A7r5) were incubated with 1 micro M reduced MTR (non-fluorescent) and the MTR oxidation product (fluorescent) was quantified. Thirty-minute pretreatment with either diazoxide (200 micro M) or pinacidil (100 micro M), both potent mitochondrial K(ATP) channel openers, increased fluorescent intensity (FI) to 149 and 162 % of control (p < 0.05 for both), respectively, and the K(ATP) channel inhibitor 5-hydroxydecanoate (5 HD) blocked it. Valinomycin, a potassium-selective ionophore, raised FI to 156 % of control (p <: 0.05). However, 5 HD did not affect the valinomycin-induced increase in FI. Inhibition of mitochondrial electron transport (myxothiazol) or uncoupling of oxidative phosphorylation (dinitrophenol) also blocked either valinomycin- or diazoxide-induced increase in FI, and free radical scavengers prevented any diazoxide-mediated increase in fluorescence. Finally the diazoxide-induced increase in fluorescence was not blocked by the PKC inhibitor chelerythrine, but was by HMR 1883, a putative surface K(ATP) channel blocker. Thus opening of K(ATP) channels increases generation of ROS via the mitochondrial electron transport chain in vascular smooth muscle cells. Furthermore, a potassium-selective ionophore can mimic the effect of putative mitochondrial KATP channel openers. We conclude that potassium movement through KATP directly leads to ROS production by the mitochondria.
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PMID:Opening of ATP-sensitive potassium channels causes generation of free radicals in vascular smooth muscle cells. 1220 Jun 36

Phosphorylation of myofilament proteins by kinases such as cAMP-dependent protein kinase and protein kinase C has been shown to lead to altered thin-filament protein-protein interactions and modulation of cardiac function in vitro. In the present study, we report that a small GTPase-dependent kinase, p21-activated kinase (PAK), increases the calcium sensitivity of Triton-skinned cardiac muscle fiber bundles. Constitutively active PAK3 caused an average 1.25-fold (25.0+/-6.0%, n=6) increase in force at pCa 5.75, 1.44-fold (44.0+/-7.78%, n=6) at pCa 6.25, and 2.41-fold (141.2+/-23.7%, n=4) at pCa 6.5, representing a change in pCa50 value of approximately 0.25. Constitutively active PAK3 produced no change in force under conditions of relaxation (pCa 8.0) or maximal contraction (pCa 4.5). Furthermore, an inactive, kinase-dead form of PAK3 failed to produce any change in force development at any pCa value. The myofilament proteins phosphorylated by PAK3, at pCa 6.5, are desmin, troponin T, troponin I, and an unidentified 70-kDa protein. Importantly, cardiac troponin I was found to be phosphorylated at serine 149 of human cardiac troponin I, representing a novel phosphorylation site. These findings suggest a novel mechanism of modulating the calcium sensitivity of cardiac muscle contraction.
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PMID:p21-activated kinase increases the calcium sensitivity of rat triton-skinned cardiac muscle fiber bundles via a mechanism potentially involving novel phosphorylation of troponin I. 1224 69

Myocardial generation of insulin-like growth factor-1 (IGF-1) is altered in hypertrophy and heart failure, but there are no reports on acute functional effects of IGF-1 in human cardiac muscle. We examined inotropic responses and signal transduction mechanisms of IGF-1 in human myocardium. Experiments were performed in isolated trabeculae or cardiomyocytes from 46 end-stage failing hearts. The effect of IGF-1 (0.001 to 0.2 micromol/L) on isometric twitch force (37 degrees C, 1 Hz), intracellular Ca2+ transients (aequorin method), sarcoplasmic reticulum (SR) Ca2+ content (rapid cooling contractures), L-type Ca2+ current (whole-cell voltage clamp), and cAMP concentrations was assessed. In addition, the effects of blocking IGF-1 receptors, phosphoinositide 3-kinase (PI3-kinase), protein kinase C (PKC), or transsarcolemmal Ca2+ entry were tested. IGF-1 exerted concentration-dependent positive inotropic effects (twitch force increased to maximally 133+/-4% of baseline values at 0.1 micromol/L; P<0.05). The IGF-1 receptor antibody alphaIR3 or the PI3-kinase inhibitor wortmannin prevented the functional effects. The inotropic response was paralleled by increases in Ca2+ transients and SR Ca2+ content. IGF-1 (0.1 micromol/L) increased L-type Ca2+ current amplitude by 24+/-7% (P<0.05). Blockade of SR function did not affect the inotropic response to IGF-1. In contrast, L-type Ca2+ channel blockade with diltiazem partially prevented ( approximately 50%) the inotropic response to IGF-1. Inhibition of PKC (GF109203X), Na+-H+ exchange (HOE642), or reverse-mode Na+-Ca2+ exchange (KB-R7943) reduced the response to IGF-1 by approximately 60% to 70%. IGF-1 exerts Ca2+-dependent positive inotropic effects through activation of IGF-1 receptors and a PI3-kinase-dependent pathway in failing human myocardium. The increased [Ca2+]i with IGF-1 originates from both enhanced L-type Ca2+ currents and enhanced Na+-H+ exchange-dependent reverse-mode Na+-Ca2+ exchange. These nongenomic functional effects of IGF-1 may be of clinical relevance.
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PMID:Insulin-like growth factor-1 exerts Ca2+-dependent positive inotropic effects in failing human myocardium. 1257 44

Cardiac troponin I (cTnI) is a phosphoprotein subunit of the troponin-tropomyosin complex that is thought to inhibit cardiac muscle contraction during diastole. To investigate the contributions of cTnI phosphorylation to cardiac regulation, transgenic mice were created with the phosphorylation sites of cTnI mutated to alanine. Activation of protein kinase C (PKC) by perfusion of hearts with phorbol-12-myristate-13-acetate (PMA) or endothelin-1 (ET-1) inhibited the maximum ATPase rate by up to 25 % and increased the Ca2+ sensitivity of ATPase activity and of isometric tension by up to 0.15 pCa units. PKC activation no longer altered cTnI phosphorylation, depressed ATPase rates or enhanced myofilament Ca2+ sensitivity in transgenic mice expressing cTnI that could not be phosphorylated on serines43/45 and threonine144 (PKC sites). Modest changes in myosin regulatory light chain phosphorylation occurred in all mouse lines, but increases in myofilament Ca2+ sensitivity required the presence of phosphorylatable cTnI. For comparison, the beta-adrenergic agonist isoproterenol caused a 38 % increase in maximum ATPase rate and a 0.12 pCa unit decrease in myofilament Ca2+ sensitivity. These beta-adrenergic effects were absent in transgenic mice expressing cTnI that could not be phosphorylated on serines23/24 (protein kinase A, PKA, sites). Overall, the results indicate that PKC and PKA exert opposing effects on actomyosin function by phosphorylating cTnI on distinct sites. A primary role of PKC phosphorylation of cTnI may be to reduce the requirements of the contractile apparatus for both Ca2+ and ATP, thereby promoting efficient ATP utilisation during contraction.
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PMID:Protein kinase C and A sites on troponin I regulate myofilament Ca2+ sensitivity and ATPase activity in the mouse myocardium. 1292 17


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