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

In the present studies, we have investigated the modulation of atrial natriuretic peptide (ANP) receptor of R2 subtype (ANP-R2/ANP-C) coupled to adenylyl cyclase/cAMP signal transduction system by angiotensin II (angII). C-ANF4-23 [des(Gln18, Ser19, Gln20, Leu21, Gly22)ANF4-23-NH2] and AngII inhibited adenylyl cyclase activity in a concentration-dependent manner in vascular smooth muscle cells (VSmc A-10). The maximal inhibitions observed were about 40 and 30%, respectively, with an apparent Ki of about 1 and 10 nm. Pretreatment of the cells with AngII resulted in the attenuation of both C-ANF4-23 and AngII-mediated inhibitions of adenylyl cyclase, without altering [125I]-ANF binding. The levels of Gialpha-2 and Gialpha-3 proteins as determined by immunoblotting were also augmented by AngII treatment. In addition, AngII treatment stimulated the phosphorylation of Gialpha2 but not of Gialpha3 or ANP-C receptor, as revealed by immunoprecipitation of the proteins using specific antibodies after prelabelling the cells with [32P]orthophosphate. Staurosporine and chelerythrine, protein kinase C (PKC) inhibitors at 1 and 100 nm, respectively, prevented the AngII-mediated desensitization of C-ANF 4-23-sensitive adenylyl cyclase. In addition, the AngII-mediated phosphorylation of Gialpha2 protein was also inhibited partially by about 35% by staurosporine treatment. These results suggest that the attenuation of C-ANF4-23-mediated inhibition of adenylyl cyclase activity by AngII may not be attributed to the downregulation of receptors or to the decreased levels of G-proteins, and may involve PKC-dependent mechanisms.
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PMID:Angiotensin II modulates ANP-R2/ANP-C receptor-mediated inhibition of adenylyl cyclase in vascular smooth muscle cells: role of protein kinase C. 973 34

Previous studies from our laboratory and others indicate that contraction-induced mechanical loading of cultured neonatal rat ventricular myocytes produces many of the phenotypic changes associated with cardiomyocyte hypertrophy in vivo, and that these changes occur via the activation of serine-threonine protein kinases. These may include the extracellular regulated protein kinases (ERK1 and ERK2), the c-Jun N-terminal kinases (JNK1, JNK2, and JNK3), and one or more isoenzymes of protein kinase C. In this study, we assessed whether one or more of these kinases are activated by stimulated contraction, and whether activation was isoenzyme-specific. Low-density, quiescent cultures of neonatal rat ventricular myocytes were maintained in serum-free medium, or electrically stimulated to contract (3 Hz) for up to 48 h. ERK and JNK activation was assessed by Western blotting with polyclonal antibodies specific for the phosphorylated forms of both kinases. PKC activation was analysed by subcellular fractionation, detergent extraction, and Western blotting using isoenzyme-specific monoclonal antibodies. Stimulated contractile activity produced myocyte hypertrophy, as indicated by increased cell size, a 15+/-5% increase in total protein/DNA ratio, and induction of ANF and beta MHC gene transcription. Electrical pacing did not cause ERK1/2 or JNK1 activation, but increased JNK2 and JNK3 phosphorylation by;two-fold. Subcellular fractionation revealed a time-dependent increase in PKC delta, and to a much lesser extent PKC xi, in a Triton X-100-soluble membrane fraction within 5 min of the onset of stimulated contraction. PKC alpha was not activated by electrical pacing. These results indicate that contraction-induced mechanical loading acutely activates some but not all of the specific isoenzymes of JNKs and PKCs in cardiomyocytes.
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PMID:Isoenzyme-specific protein kinase C and c-Jun N-terminal kinase activation by electrically stimulated contraction of neonatal rat ventricular myocytes. 1090 Jan 80

The intrinsic GTPase activity of Galpha q is low, and RGS proteins which activate GTPase are expressed in the heart; however, their functional relevance in vivo is unknown. Transgenic mice with cardiac-specific overexpression of Galpha q in myocardium exhibit cardiac hypertrophy, enhanced PKC xi membrane translocation, embryonic gene expression, and depressed cardiac contractility. We recently reported that transgenic mice with cardiac-specific expression of RGS4, a Galpha q and Galpha i GTPase activator, exhibit decreased left ventricular hypertrophy and ANF induction in response to pressure overload. To test the hypothesis that RGS4 can act as a Galpha q-specific GTPase activating protein (GAP) in the in vivo heart, dual transgenic Galpha q-40xRGS4 mice were generated to determine if RGS4 co-expression would ameliorate the Galpha q-40 phenotype. At age 4 weeks, percent fractional shortening was normalized in dual transgenic mice as was left ventricular internal dimension and posterior and septal wall thicknesses. PKC xi membrane translocation and ANF and alpha -skeletal actin mRNA levels were also normalized. Compound transgenic mice eventually developed depressed cardiac contractility that was evident by 9 weeks of age. These studies establish for the first time a role for RGS4 as a GAP for Galpha q in the in vivo heart, and demonstrate that its regulated expression can have pathophysiologic consequences.
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PMID:RGS4 reduces contractile dysfunction and hypertrophic gene induction in Galpha q overexpressing mice. 1116 25

The regulatory neuropeptide calcitonin-gene related peptide (CGRP) has been shown to evoke a hypertrophic response in isolated cardiomyocytes in vitro, an effect which was attributed to PKC activation. Activation of PKC has previously been implicated in the development of cardiac hypertrophy. We therefore investigated the role of CGRP in pressure overload-induced hypertrophy in vivo, which has not previously been reported. Constriction of the ascending aorta of rats resulted in an increase in the heart weight to body weight ratio, increased myocyte diameter, re-expression of the fetal genes ANF, MHCbeta and skeletal alpha-actin, and decreased expression of the adult genes GLUT4 and SERCA2a. Treatment of neonatal rat pups (1-2 days old) with capsaicin (50 mg/kg), resulted in the permanent de-afferentation of small-diameter unmyelinated CGRP-containing sensory C-fibres. Such treatment caused a 68% decrease in the CGRP-like immunoreactivity of hearts isolated from 10 week old rats (p < 0.001). Contrary to expectations, aortic constriction of capsaicin treated rats had no effect on the development of hypertrophy at the trophic, morphometric or gene expression levels. The results suggest that the development of pressure overload-induced hypertrophy in vivo does not require the regulatory neuropeptide CGRP.
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PMID:Calcitonin gene-related peptide is not essential for the development of pressure overload-induced hypertrophy in vivo. 1171 63

The transcription factor nuclear factor-kappaB (NF-kappaB) regulates expression of a variety of genes involved in immune responses, inflammation, proliferation, and programmed cell death (apoptosis). Here, we show that in rat neonatal ventricular cardiomyocytes, activation of NF-kappaB is involved in the hypertrophic response induced by myotrophin, a hypertrophic activator identified from spontaneously hypertensive rat heart and cardiomyopathic human hearts. Myotrophin treatment stimulated NF-kappaB nuclear translocation and transcriptional activity, accompanied by IkappaB-alpha phosphorylation and degradation. Consistently, myotrophin-induced NF-kappaB activation was enhanced by wild-type IkappaB kinase (IKK) beta and abolished by the dominant-negative IKKbeta or a general PKC inhibitor, calphostin C. Importantly, myotrophin-induced expression of two hypertrophic genes (atrial natriuretic factor [ANF] and c-myc) and also enhanced protein synthesis were partially inhibited by a potent NF-kappaB inhibitor, pyrrolidine dithio-carbamate (PDTC), and calphostin C. Expression of the dominant-negative form of IkappaB-alpha or IKKbeta also partially inhibited the transcriptional activity of ANF induced by myotrophin. These findings suggest that the PKC-IKK-NF-kappaB pathway may play a critical role in mediating the myotrophin-induced hypertrophic response in cardiomyocytes.
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PMID:Activation of nuclear factor-kappaB is necessary for myotrophin-induced cardiac hypertrophy. 1248 12

The effect of the lysophospholipid, lysophosphatidic acid (LPA), on signaling and hypertrophy of neonatal rat ventricular cardiomyocytes was examined. Myocytes express mRNA for all three G-protein-coupled LPA receptor subtypes (LPA(1)/Edg-2, LPA(2)/Edg-4, and LPA(3)/Edg-7) as indicated by RT-PCR analysis. LPA inhibits isoproterenol-stimulated cyclic AMP accumulation with an IC(50) approximately 40 nM and promotes phosphorylation of ERK-1/2. LPA also elicits a small, slow onset, and activation of phosphoinositide hydrolysis with EC(50) approximately 400 nM, and stimulates a marked increase in the extent of Rho activation. Longer-term treatment with LPA induces a hypertrophic response in myocytes as indicated by increases in cell size, actin organization, ANF staining of the perinuclear region and activation of ANF promoter-luciferase gene expression. Pretreatment of myocytes with pertussis toxin (PTX) not only blocks the capacity of LPA to inhibit cyclic AMP formation and stimulate ERK phosphorylation, but also inhibits hypertrophic changes in cell morphology and ANF-luciferase gene expression. Neither phospholipase C nor Rho activation is PTX sensitive. The hypertrophic effects of LPA on myocytes are also inhibited by treatment with C3 exoenzyme or by transfection of plasmids expressing either C3 exoenzyme or dominant-negative Rho to block Rho function. Inhibition of ERK activation with PD98059 blocks LPA-induced hypertrophy while inhibitors of phospholipase C (U73122), PKC (GF109203X), or p38MAPK (SB203580) do not. These data suggest that LPA induces cardiomyocyte hypertrophy via a pathway different from the conventional G(q) pathway utilized by phenylephrine, endothelin, and PGF2 alpha and involving activation of a PTX-sensitive G(i)/ERK pathway in conjunction with activation of Rho-mediated signals.
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PMID:Lysophosphatidic acid induces hypertrophy of neonatal cardiac myocytes via activation of Gi and Rho. 1508 6

Several reports have suggested that the TAK1-MKK3/6-p38MAPK signaling axis is important for TGF-beta-related cardiac hypertrophy. Despite this, the effects of exogenous TGF-beta on cardiac hypertrophy and associated signaling mechanisms have not been demonstrated directly. Moreover, the roles of the signaling mechanisms involved in cardiac hypertrophy (TAK1 upstream and p38MAPK downstream) remain unclear. In this study, we investigated the potential involvement of protein kinase C and activating transcription factor-2 in TGF-beta1-induced cardiac hypertrophic responses in cultured neonatal rat ventricular cardiomyocytes. TGF-beta1 treatment resulted in upregulation of mRNA expression or promoter activities of beta-myosin heavy chain, atrial natriuretic factor, and brain natriuretic peptide, and increased myocyte protein content, cell size, and sarcomeric organization. These are all characteristic hallmarks of cardiac hypertrophy. PKC was found to be involved throughout the signaling system, and it was shown that it acts by mediating upstream TAK1 activation and leads to ATF-2 activation. PKC-dependent ATF-2 activation was shown to be involved in TGF-beta1-induced cardiac hypertrophic responses. The PKC inhibitors, GO6976 and GF109203X, completely blocked TGF-beta1-induced TAK1 kinase activity and subsequent downstream signaling pathways including ATF-2 phosphorylation, leading to suppression of ATF-2 transcriptional activity. This inhibitory effect was reflected in cardiac hypertrophic responses such as inhibitions of beta-MHC gene induction and ANF promoter activity. Our results suggest that PKC is involved in TGF-beta1-induced cardiac hypertrophic responses in our cell culture system and that ATF-2 activation plays a role.
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PMID:TGF-beta1 induces cardiac hypertrophic responses via PKC-dependent ATF-2 activation. 1612 22

We have previously reported a transgenic mouse that over-expresses constitutively active PKCepsilon in the myocardium and exhibits a steady progression to heart failure. Associated with the decline in function was an increased phosphorylation of sarcomeric proteins including cardiac troponin I (cTnI). To determine whether PKCepsilon phosphorylation of cTnI is sufficient to induce cardiac maladaptation, we have generated a double transgenic mouse (DbTG) that expresses constitutively active PKCepsilon and cTnI harboring non-phosphorylatable mutations in the putative PKC phosphorylation sites (S43A, S45A). We compared the hemodynamic and biochemical properties of the hearts from the DbTG mice to the non-transgenic and single transgenic lines at both 3 and 12 months of age. While no significant differences in LV function were noted in 3-month groups, the depression of function in the PKCepsilon mice was attenuated in the double transgenic mice at 12 months. The improvement in cardiac function was correlated with decreased beta-myosin heavy chain and ANF mRNA expression in the 12m DbTG mice. The extent of cTnI phosphorylation was determined using a novel one-dimensional, non-equilibrium isoelectric focusing technique. At 3 months the migration of cTnI phospho-species was different in the PKCepsilon mice and to a lesser degree in the DbTG compared to all other groups. At 12 months additional phospho-species were observed in both the PKCepsilon and DbTG samples, along with an overall shift in the distribution of phospho-species in all groups due to age. These results suggest that phosphorylation of cTnI by PKCepsilon is associated with contractile dysfunction and partial replacement of serines 43/45 improves cardiac performance. Therefore, we conclude that phosphorylation of cTnI at Ser 43 and 45 may contribute to the progression of failure.
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PMID:Partial replacement of cardiac troponin I with a non-phosphorylatable mutant at serines 43/45 attenuates the contractile dysfunction associated with PKCepsilon phosphorylation. 1651 95

Our laboratory has previously shown that adenoviral-mediated overexpression of Galphaq in neonatal rat ventricular cardiomyocytes increases the phosphorylation of Akt, a well-established anti-apoptotic effector. As demonstrated here, Galphaq expression protects cardiomyocytes against apoptosis induced by treatment with 2-deoxyglucose (2DOG) and this protection is lost when Akt activation is prevented by treatment with LY294002 (an inhibitor of PI3K). Galphaq-induced Akt phosphorylation is not caused by increased Gbetagamma signaling and does not appear to involve PKC activation. Rather studies using the EGF receptor inhibitor AG1478 and the Src inhibitor PP2 implicate these tyrosine kinases in the pathway inducing Akt phosphorylation. EGFR phosphorylation is increased in cells expressing Galphaq and this effect is inhibited by PP2, placing Src upstream of EGFR phosphorylation. EGFR activation appears to be required for Galphaq-mediated protection since inhibition of Src or EGFR rendered cells susceptible to 2DOG-induced apoptosis. In contrast to the requirement for EGFR mediated Akt activation in cardioprotection, neither EGFR nor Akt activation are necessary for the hypertrophic increases in cell size or ANF content elicited by Galphaq overexpression. These data demonstrate that increased Galphaq activity can provide anti-apoptotic signals by eliciting EGFR phosphorylation and subsequent Akt activation, independent of the well-known ability of Galphaq signaling to elicit hypertrophy.
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PMID:Galphaq expression activates EGFR and induces Akt mediated cardiomyocyte survival: dissociation from Galphaq mediated hypertrophy. 1663 Jun 27

Diadenosine polyphosphates (APnAs) are endogenous compounds and exert diverse cardiovascular functions. However, the effects of APnAs on atrial ANP release and contractility have not been studied. In this study, the effects of diadenosine tetraphosphate (AP4A) on atrial ANP release and contractility, and their mechanisms were studied using isolated perfused rat atria. Treatment of atria with AP4A resulted in decreases in atrial contractility and extracellular fluid (ECF) translocation whereas ANP secretion and cAMP levels in perfusate were increased in a dose-dependent manner. These effects of AP4A were attenuated by A(1) receptor antagonist but not by A(2A) or A(3) receptor antagonist. Other purinoceptor antagonists also did not show any effects on AP4A-induced ANF release and contractility. The increment of ANP release and negative inotropy induced by AP4A was similar to those induced by AP3A, AP5A, and AP6A. Protein kinase A inhibitors accentuated AP4A-induced ANP secretion. In contrast, an inhibitor of phospholipase C, protein kinase C or sarcolemma K(ATP) channel completely blocked AP4A-induced ANP secretion. However, an inhibitor of adenylyl cyclase or mitochondria K(ATP) channel had no significant modification of AP4A effects. These results suggest that AP4A regulates atrial inotropy and ANP release mainly through A(1) receptor signaling involving phospholipase C-protein kinase C and sarcolemmal K(ATP) channel and that protein kinase A negatively modulates the effects of AP4A.
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PMID:Diadenosine tetraphosphate stimulates atrial ANP release via A(1) receptor: involvement of K(ATP) channel and PKC. 1761 60


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