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)

Committed skeletal muscle myoblasts undergo terminal differentiation when shifted from a high-mitogen medium to a low-mitogen medium. However, expression of the myogenic regulatory factor MyoD seems to be similar in proliferating and differentiating cells, suggesting that its function is attenuated in proliferating myoblasts. To further understand the potential mechanisms that may attenuate MyoD function, we have examined the effect of posttranslational modification. By analogy with myogenin, we have examined the role of phosphorylation in regulating the function of MyoD. MyoD contains two putative protein kinase C (PKC) phosphorylation sites (Thr115 and Ser200). The former site is analogous to Thr85 within the highly conserved basic domain of myogenin that has been demonstrated to negatively regulate the myogenic differentiation functions of myogenin. To test whether hyperphosphorylation of the same PKC site in MyoD would attenuate its function, we generated a mutant MyoD with a single amino acid substitution (Thr115-Ala) that disrupts the PKC phosphorylation site (Thr115) within the conserved basic domain. Wild-type and mutant MyoD were introduced into cells using an E1, E3-deleted adenoviral vector. In mouse C3H10T1/2 fibroblasts, both wild-type and mutant MyoD induced terminal myogenic differentiation when growth factors were withdrawn from the cell culture. Consistent with these results, nuclear extracts from infected cells, but not those from uninfected cells, demonstrated complex formation with an oligonucleotide containing an E-box consensus sequence. Growth arrest was associated with the up-regulation of p21cip1, cell fusion to multinucleated myotubes, and the expression of a muscle differentiation marker (myosin heavy chain). On the other hand, when infected cells were maintained under high mitogenic conditions (in the presence of 10% fetal bovine serum), the expression of wild-type or mutant MyoD slowed cell growth and induced p21cip1. Only mutant MyoD caused cell fusion, myosin heavy chain expression, and altered mobility of the E-box oligonucleotide in gel shift assays. Furthermore, after infection, MyoD was phosphorylated, and phosphothreonine was detected in wild-type MyoD immunoprecipitated only from C3H10T1/2 cells grown under high mitogenic conditions. These results suggest that Thr115 may play an important role in the regulation of MyoD function under conditions of high mitogenesis. MyoD was also phosphorylated in malignant rhabdomyosarcoma (RMS) cells in which MyoD function was attenuated. Phosphothreonine was also detected in MyoD immunoprecipitates. Rh30 alveolar RMS cells were infected with an adenovirus expressing either wild-type or mutant MyoD. In contrast to the results in fibroblasts, when overexpressed in malignant Rh30 RMS cells, mutant MyoD arrested cell growth without inducing p21cip1 and caused cell fusion. However, no muscle differentiation markers were detected, indicating that an overexpression of mutant MyoD lacking Thr115 caused Rh30 cells to become quiescent and recapitulate at least some aspects of myogenesis (cell fusion).
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PMID:Mutation of Thr115 in MyoD positively regulates function in murine fibroblasts and human rhabdomyosarcoma cells. 975 Nov 14

In an in vivo study, spontaneously hypertensive rats (SHR) were treated with an angiotensin II (Ang II) type 1 receptor antagonist of candesartan or hydralazine. Untreated SHR progressively developed severe hypertension, and treatment with candesartan or hydralazine decreased blood pressure. Candesartan reduced left ventricular (LV) weight, LV wall thickness, transverse myocyte diameter, the relative amount of V3 myosin heavy chain, and interstitial fibrosis, while treatment with hydralazine slightly prevented an increase in LV wall thickness, but did not exert a significant reduction on other parameters. In an in vitro study, neonatal rat cardiomyocytes were cultured on deformable silicone dishes. Stretching cardiomyocytes activated second messengers such as protein kinase C, Raf-1 kinase, and mitogen-activated protein (MAP) kinase, increasing protein synthesis, enhancing endothelin (ET)-1 release, activating the Na+/H+ ion exchanger. Moreover, pretreatment with candesartan diminished an increase in phenylalanine incorporation, MAP kinase activity, and c-fos gene expression induced by the stretching of cardiomyocytes. This suggests that the cardiac renin-angiotensin system is linked to the formation of pressure-overload hypertrophy and that Ang II increases the growth of cardiomyocytes by an autocrine mechanism. Finally, we examined the signalling pathways leading to MAP kinase activation both in cardiac myocytes and in cardiac fibroblasts. Ang II-evoked signal transduction pathways differed between cell types. In cardiac fibroblasts, Ang II activated MAP kinase through a pathway including the Gbetagamma subunit of Gi protein, Src, Shc, Grb2, and Ras, while Gq and protein kinase C were important in cardiac myocytes.
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PMID:Role of tissue angiotensin II in myocardial remodelling induced by mechanical stress. 1007 20

This study tested the hypothesis that in vivo norepinephrine (NE) treatment induces bimodal cardiac functional protection against ischemia and examined the roles of alpha1-adrenoceptors, protein kinase C (PKC), and cardiac gene expression in cardiac protection. Rats were treated with NE (25 micrograms/kg iv). Cardiac functional resistance to ischemia-reperfusion (25/40 min) injury was examined 30 min and 1, 4, and 24 h after NE treatment with the Langendorff technique, and effects of alpha1-adrenoceptor antagonism and PKC inhibition on the protection were determined. Northern analysis was performed to examine cardiac expression of mRNAs encoding alpha-actin and myosin heavy chain (MHC) isoforms. Immunofluorescent staining was performed to localize PKC-betaI in the ventricular myocardium. NE treatment improved postischemic functional recovery at 30 min, 4 h, and 24 h but not at 1 h. Pretreatment with prazosin or chelerythrine abolished both the early adaptive response at 30 min and the delayed adaptive response at 24 h. NE treatment induced intranuclear translocation of PKC-betaI in cardiac myocytes at 10 min and increased skeletal alpha-actin and beta-MHC mRNAs in the myocardium at 4-24 h. These results demonstrate that in vivo NE treatment induces bimodal myocardial functional adaptation to ischemia in a rat model. alpha1-Adrenoceptors and PKC appear to be involved in signal transduction for inducing both the early and delayed adaptive responses. The delayed adaptive response is associated with the expression of cardiac genes encoding fetal contractile proteins, and PKC-betaI may transduce the signal for reprogramming of cardiac gene expression.
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PMID:Adrenergic induction of bimodal myocardial protection: signal transduction and cardiac gene reprogramming. 1023 47

Mechanical stretch induced by high blood pressure is an initial factor leading to cardiac hypertrophy. In an in vivo study, an angiotensin II (AngII) type 1 receptor antagonist TCV116 reduced left ventricular (LV) weight, LV wall thickness, transverse myocyte diameter, relative amount of V3 myosin heavy chain, and interstitial fibrosis, while treatment with hydralazine did not. In an in vitro study using cultured cardiomyocytes, mechanical stretch activated second messengers such as mitogen-activated protein (MAP) kinase, followed by increased protein synthesis. Additionally, in the stretch-conditioned medium AngII and endothelin-1 concentrations were increased. Furthermore, the Na+/H+ exchanger activated by mechanical stretch modulated the hypertrophic responses of cardiomyocytes. The pathways leading to MAP kinase activation differed between cell types. In cardiac fibroblasts AngII activated MAP kinase via G beta gamma subunit of Gi, Src, Shc, Grb2, and Ras, whereas Gq and protein kinase C were critical in cardiomyocytes.
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PMID:The molecular mechanism of cardiac hypertrophy and failure. 1041 19

We here examined the role of the interleukin-6 (IL-6) family of cytokines in endothelin-1 (ET-1)-induced hypertrophic responses using cultured cardiac myocytes of neonatal rats. ET-1 induced expression of IL-6 and leukemia inhibitory factor (LIF) genes. ET-1-induced LIF gene expression was abolished by inhibition of protein kinase C activity. ET-1 activated the promoter of atrial natriuretic peptide and beta-type myosin heavy chain genes through the tyrosine kinase pathway and IL-6 receptor gp130. These results suggest that the IL-6 family of cytokines mediates ET-1-induced expression of some fetal genes in cardiac myocytes.
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PMID:Endothelin-1 induces expression of fetal genes through the interleukin-6 family of cytokines in cardiac myocytes. 1045 39

Expression of the slow myosin heavy chain (MyHC) 2 gene defines slow versus fast avian skeletal muscle fiber types. Fetal, or secondary, skeletal muscle fibers express slow MyHC isoform genes in developmentally regulated patterns within the embryo, and this patterning is at least partly dependent on innervation in vivo. We have previously shown that slow MyHC 2 gene expression in vitro is regulated by a combination of innervation and cell lineage. This pattern of gene expression was indistinguishable from the pattern observed in vivo in that it was restricted to innervated muscle fibers of slow muscle origin. We show here that slow MyHC 2 gene expression in the slow muscle fiber lineage is regulated by protein kinase C (PKC) activity. Inhibition of PKC activity induced slow MyHC 2 gene expression, and the capacity to express the slow MyHC 2 gene was restricted to muscle fibers of slow muscle (medial adductor) origin. Fast muscle fibers derived from the pectoralis major did not express significant levels of slow MyHC 2 with or without inhibitors of PKC activity. This differential expression pattern coincided with different inherent PKC activities in fast versus slow muscle fiber types. Furthermore, over-expression of an unregulated PKCalpha mutant suppressed slow MyHC 2 gene expression in muscle fibers of the slow lineage. Lastly, denervation of skeletal muscles caused an increase in PKC activity, particularly in the slow medial adductor muscle. This increase in PKC activity was associated with lack of slow MyHC 2 gene expression in vivo. These results provide a mechanistic link between innervation, an intracellular signaling pathway mediated by PKC, and expression of a muscle fiber type-specific contractile protein gene. Dev Dyn 1999;216:177-189.
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PMID:Protein kinase C activity regulates slow myosin heavy chain 2 gene expression in slow lineage skeletal muscle fibers. 1053 57

Although cytoskeletal proteins such as myosin II are implicated in the control of insulin secretion, their precise role is poorly understood. In other secretory cells, myosin II is predominantly regulated via the phosphorylation of the regulatory light chains (RLC). The current study was aimed at investigating RLC phosphorylation in beta-cells. In both the insulin-secreting cell line RINm5F and rat pancreatic islets, the RLC was basally phosphorylated on the myosin light chain kinase sites (Ser19/Thr18). Phosphorylation at these sites was not consistently increased by either metabolic stimuli (glyceraldehyde/glucose) or the depolarizing agent KCl. The RLC sites phosphorylated by protein kinase C (PKC) (Ser1/Ser2) were unphosphorylated in the basal state, not affected by nutrients or KCl, and only slightly increased by the PKC activator phorbol 12-myristate 13-acetate (PMA). Like the other insulin secretagogues, however, PMA did promote serine phosphorylation of the myosin heavy chain (MHC) in RINm5F cells. Phosphopeptide mapping suggested that the same peptide was phosphorylated under both PMA and glyceraldehyde stimulation, which further extends our previous study of the Ca2+-dependent phosphorylation of this protein (Wilson JR, Ludowyke RI, Biden TJ: Nutrient stimulation results in a rapid Ca2+-dependent threonine phosphorylation of myosin heavy chain in rat pancreatic islets and RINm5F cells. J Biol Chem 273:22729-22737, 1998). Overall, our results demonstrate that in RINm5F cells and rat pancreatic islets, MHC phosphorylation correlates better with insulin secretion than phosphorylation of the RLC. We therefore propose that in beta-cells, in contrast to other secretory cells, phosphorylation of the MHC is more important than that of the RLC for regulation of the myosin II protein complex during insulin secretion.
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PMID:Increases in phosphorylation of the myosin II heavy chain, but not regulatory light chains, correlate with insulin secretion in rat pancreatic islets and RINm5F cells. 1058 Apr 27

Hypertrophy is an adaptive response of the heart to hemodynamic overload such as hypertension. However, it is generally accepted that cardiac hypertrophy is one of the most critical risk factors of heart disease. Therefore, for the treatment of hypertension it is important to understand the mechanism of cardiac hypertrophy and to establish effective pharmaceutical interventions. Mechanical stretch induced by hypertension is an initial factor leading to cardiac hypertrophy. In an in vivo study using spontaneously hypertensive rats, an angiotensin II type 1 receptor antagonist, TCV116, decreased left ventricular weight, left ventricular wall thickness, transverse myocyte diameter, relative amount of V3 myosin heavy chain, and interstitial fibrosis, whereas treatment with hydrolazine did not. In an in vitro study using cultured cardiomyocytes of neonatal rats, mechanical stretch activated second messengers, such as extracellular signal-regulated protein kinase (ERK), followed by increased protein synthesis. Additionally, in the stretch-conditioned medium, the levels of angiotensin II and endothelin-1 concentrations were increased. Moreover, the Na+/H+ exchanger activated by mechanical stretch modulated the hypertrophic responses of cardiomyocytes. To further elucidate whether angiotensin II is indispensable for mechanical stress-induced cardiac hypertrophy, mechanical stretch-induced ERK activation was examined in angiotensin II type 1a receptor knock-out mice. Although the addition of angiotensin II had no effects on the ERK activity in cardiomyocytes of angiotensin II type 1a receptor knockout mice, mechanical stretch induced a larger increase in the ERK activity in cardiac myocytes from these mice compared with cardiac myocytes of wild-type mice. These results suggest that mechanical stretch could induce hypertrophic responses in cardiac myocytes even in the absence of angiotensin II. The pathways leading to ERK activation differed between cell types. In cardiac fibroblasts, angiotensin II activated ERK via the G(beta)gamma subunit of Gi, Src, Shc, Grb2, and Ras, whereas Gq and protein kinase C were critical in cardiomyocytes.
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PMID:Role of the renin-angiotensin system in cardiac hypertrophy. 1075 May 88

Endothelin-1 (ET) produces neonatal rat ventricular myocyte (NRVM) hypertrophy and activates focal adhesion kinase (FAK) in other cell types. In the present study, we examined whether ET activated FAK in NRVM and whether FAK was necessary and/or sufficient for ET-induced NRVM hypertrophy. Chronic ET-1 stimulation (100 nM, 48 h) increased protein-to-DNA and myosin heavy chain (MHC)-to-DNA ratios and stimulated the assembly of newly synthesized MHC into sarcomeres. ET-1 also induced the assembly of focal adhesions and costameres, as evidenced by increased phosphotyrosine, FAK, and paxillin immunostaining. Acutely, ET treatment rapidly increased tyrosine phosphorylation of FAK and paxillin. FAK was also activated by phorbol 12-myristate 13-acetate (2 microM, 5 min). Pretreatment with chelerythrine (5 microM) or rottlerin (10 microM) completely blocked ET-induced FAK phosphorylation, indicating that protein kinase C activation was upstream of ET-induced FAK activation. In contrast, ET-induced FAK activation was not affected by blocking calcium influx via L-type voltage-gated calcium channels. Adenoviruses (Adv) containing FAK and FAK-related nonkinase (FRNK) were used to specifically define the role of FAK in ET-induced hypertrophy. ET stimulation failed to increase total protein-to-DNA or MHC-to-DNA ratios or to stimulate sarcomeric assembly in myocytes infected with Adv-FRNK. However, Adv-FAK alone did not increase total protein-to-DNA or MHC-to-DNA ratios and failed to increase the number or size of myofibrils as evidenced by double immunofluorescence labeling for MHC and FAK. Thus, although FAK is necessary for ET-induced NRVM hypertrophy, other ET-generated signals are also required to elicit the hypertrophic phenotype.
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PMID:Endothelin-induced cardiac myocyte hypertrophy: role for focal adhesion kinase. 1077 51

Endothelin-1 (ET-1) induces cardiac hypertrophy. Because Ca(2+) is a major second messenger of ET-1, the role of Ca(2+) in ET-1-induced hypertrophic responses in cultured cardiac myocytes of neonatal rats was examined. ET-1 activated the promoter of the beta-type myosin heavy chain gene (beta-MHC) (-354 to +34 base pairs) by about 4-fold. This activation was inhibited by chelation of Ca(2+) and the blocking of protein kinase C activity. Similarly, the beta-MHC promoter was activated by Ca(2+) ionophores and a protein kinase C activator. beta-MHC promoter activation induced by ET-1 was suppressed by pretreatment with the calmodulin inhibitor, W7, the Ca(2+)/calmodulin-dependent kinase II (CaMKII) inhibitor, KN62, and the calcineurin inhibitor, cyclosporin A. beta-MHC promoter activation by ET-1 was also attenuated by overexpression of dominant-negative mutants of CaMKII and calcineurin. ET-1 increased the activity of CaMKII and calcineurin in cardiac myocytes. Pretreatment with KN62 and cyclosporin A strongly suppressed ET-1-induced increases in [(3)H]phenylalanine uptake and in cell size. These results suggest that Ca(2+) plays a critical role in ET-1-induced cardiomyocyte hypertrophy by activating CaMKII- and calcineurin-dependent pathways.
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PMID:Ca2+/calmodulin-dependent kinase II and calcineurin play critical roles in endothelin-1-induced cardiomyocyte hypertrophy. 1080 60


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