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)

To investigate postreceptor pathways of endothelin and the site of action responsible for enhancing myocardial contractility, studies were performed on ferret papillary muscles loaded with the Ca2+ indicator aequorin. Endothelin-1 (ET) and the alpha 1-adrenoceptor agonist, phenylephrine (PE) produced similar dose-dependent increases in tension development and peak intracellular Ca2+ concentration ([Ca2+]i); moreover, pretreatment with PE eliminated effects of ET, suggesting similar postreceptor pathways. Because alpha 1-adrenoceptor activation is thought to cause the hydrolysis of phosphatidylinositol and generate D-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] and 1,2-diacylglycerol (DAG), the protein kinase C (PKC) activator 4 beta-phorbol 12-myristate 13-acetate (PMA) was used to determine whether activation of PKC was responsible for the myocardial actions of ET. In contrast to ET, PMA decreased tension development and peak [Ca2+]i, and pretreatment with PMA attenuated the myocardial action of ET; however, intracellular Ins(1,4,5)P3 levels were greatly increased by ET stimulation, suggesting that rather than DAG, Ins(1,4,5)P3 might be the second messenger for the actions of ET. To determine whether ET produced actions on the contractile elements, thereby enhancing myocardial contractility, 2,3-butanedione monoxime (BDM) was used to interfere with the interaction of myosin and actin. Pretreatment with 6 mM BDM did not alter the half-maximum effective concentration (EC50) of the [Ca2+]o-tension relation, but, in contrast, shifted the ET dose-response curve to the right, and increased the EC50 by approximately 1.0 log unit. In addition, ET partially reversed the downward shift of the peak [Ca2+]i-peak tension curve induced by BDM.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Endothelin-1 enhances cross-bridge function of ferret myocardium: role of second messengers. 828 56

Endothelin-1 (ET-1) is known to stimulate phospholipase C (PLC) activity in SK-N-MC human neuroblastoma/epithelioma cells: here we show that phospholipase D (PLD) is also stimulated. The generation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) by ET-1-stimulated PLC was attenuated by protein kinase C (PKC) activation and enhanced by PKC inhibition. An enhancement of ET-1-stimulated Ins(1,4,5)P3 accumulation was also seen when the product of PLD activity was either diverted into phosphatidyl butanol in the presence of butanol, or phosphatidate phosphohydrolase (PPH) activity was inhibited by DL-propranolol. We conclude that there is an inhibitory, PKC-mediated, feedback loop in these cells which is dependent, in part, on the activation of PKC by product(s) of the PLD/PPH pathway. This provides a novel role for agonist-stimulated PLD activation.
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PMID:Phospholipase D activation regulates endothelin-1 stimulation of phosphoinositide-specific phospholipase C in SK-N-MC cells. 833 5

Endothelin-1 (ET) and ATP mobilize Ca2+ in rat C6 glioma cells by stimulating phosphoinositide turnover. Both agents also inhibit adenylyl cyclase (AC) activity in C6 glioma cells. The goal of this study was to characterize the molecular mechanisms responsible for the inhibition of AC activity. The administration of either ET, ATP, A23187, or thapsigargin to cells simultaneously with isoproterenol for 5 min inhibited isoproterenol-stimulated cAMP synthesis by a maximum of 60%, 91%, 65%, and 68%, respectively. Pretreatment of cells with pertussis toxin (PTX) did not alter the inhibitory effects of A23187 or thapsigargin, whereas the inhibitory effects of ET or ATP were completely eliminated. Removal of extracellular Ca2+ and 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'- tetraacetic acid acetoxymethyl ester treatment failed to affect the inhibition caused by ET or ATP, whereas the inhibition caused by A23187 or thapsigargin was completely eliminated in Ca(2+)-free medium and was attenuated by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester treatment. The inhibition by both receptor agonists in the earlier phase (30 sec) of the AC reaction was, however, reduced by using either Ca(2+)-free medium or PTX pretreatment. The administration of 3-isobutyl-1-methylxanthine or Ro 20-1724 suggested that the inhibitory effects of A23187 and thapsigargin were partially due to Ca(2+)-dependent stimulation of PDE activity. Short term treatment with phorbol-12-myristate-13-acetate (PMA) had no effect on isoproterenol-stimulated AC activity. However, the inhibition of cAMP induced by ET or ATP, but not by A23187 or thapsigargin, was diminished by PMA, suggesting that the receptor signal via Gi was blocked by PMA treatment. The antagonistic effect of PMA was blocked by staurosporine. All four agents still inhibited AC activity in cells that had been treated with PMA for 24 hr to deplete protein kinase C. ET produced an additional decrease in AC activity in cells that had been treated with a maximally effective concentration of A23187 or thapsigargin. The ET- or ATP-induced decrease in cAMP levels showed homologous desensitization. These results demonstrate that ETZ receptors and ATP receptors in C6 glioma cells inhibit AC activity primarily by interaction with a PTX-sensitive G(i) and partially by elevation of [Ca(2+)]. Protein kinase C activation is not responsible for agonist-induced inhibition of AC but appears to uncouple the G(i)/AC system activated by ET or ATP.
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PMID:Endothelin- and ATP-induced inhibition of adenylyl cyclase activity in C6 glioma cells: role of Gi and calcium. 834 Dec 70

Endothelin-1 (ET-1) exerts the following two types of aldosterone-stimulating actions on glomerulosa cells: ET-1-mediated direct stimulation of aldosterone secretion (per se effect) and potentiation of the aldosterone secretion to angiotensin II (ANG II; potentiation effect). The role of Ca2+ and protein kinase C (PKC) systems in these two effects was investigated. Incubations of calf cultured adrenal zona glomerulosa cells in low-Ca2+ media or in the presence of the Ca2+ channel antagonist verapamil reduced the aldosterone secretion to ET-1. When cells were preincubated with ET-1 in a low-Ca2+ media or in the presence of the Ca2+ channel antagonist verapamil, washed, and incubated in media with normal Ca2+, ANG II showed potentiation of ANG II-stimulated aldosterone secretion. The PKC inhibitors H-7 and staurosporine did not decrease ET-1-stimulated aldosterone secretion, but they inhibited the potentiation effect of ET-1 on ANG II-mediated aldosterone secretion. Adrenocorticotropic hormone desensitization or prolonged phorbol ester stimulation of PKC resulting in desensitization also resulted in the abolition of the ET-1-mediated ANG II potentiation of aldosterone secretion. The PKC inhibitors did not affect ANG II-stimulated aldosterone secretion. We conclude that ET-1 exerts a direct stimulation of aldosterone secretion through a mechanism dependent on Ca2+ and potentiates ANG II-mediated aldosterone stimulation through a mechanism involving PKC.
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PMID:Mechanisms of ET-1 potentiation of angiotensin II stimulation of aldosterone production. 836 85

The goal of the present study was to identify the molecular mechanism underlying desensitization of endothelin-1 receptor-mediated phosphoinositide response in cultured neonatal rat heart cells. Endothelin elicited a concentration-dependent (EC50 = 2.2 x 10(-9) M) increase of inositol-phosphate production with a much higher potency than phenylephrine (EC50 = 1.4 x 10(-6) M). Endothelin-1 (10(-8) M) evoked phosphoinositide turnover in the presence of 10 mM LiCl, which was greatly attenuated after 30-45 min of continuous stimulation with agonist, apparently resulting in a total absence of further inositol-phosphate accumulation. However, when the uncompetitive inositol monophosphatase inhibitor Li+ was only present during the last 30 min of 150 min incubation, the inositol-phosphate accumulation was decreased to a steady state of 33% of the initial rate. The loss of responsiveness of cardiomyocytes to endothelin-1 was not brought about by a limiting supply of phospholipase C substrate phosphatidylinositol 4,5-bisphosphate. A very rapid resynthesis of this substrate took place as its level remained almost constant during 45 min stimulation with 10(-8) M endothelin-1 while the accumulation of inositol-phosphates was at least 15-fold higher than the initial cellular phosphatidylinositol 4,5-bisphosphate content. After 120 min preincubation of cells with 10(-9) M endothelin-1 the activation of phospholipase C by a second higher dose (10(-8) M) was severely (67%) inhibited at the same time leaving the induction of phosphoinositide turnover by phenylephrine (10(-4) M) virtually intact. Preincubation with phenylephrine (3 x 10(-6) M) also led to inhibition of the phenylephrine (10(-4) M)-mediated inositol-phosphate response (36% inhibition) while the endothelin-1 (10(-8) M) response was not affected. Addition of a direct activator of protein kinase C, phorbol 12-myristate 13-acetate, led to inhibition of the endothelin-1 evoked phosphoinositide turnover but the rate of desensitization was not affected. Inhibition of protein kinase C with staurosporine did not alter the time course of desensitization. In conclusion, the activity of the phosphoinositide cycle in cardiomyocytes is homologously desensitized after stimulation with endothelin-1. The desensitization is not likely to be due to either depletion of phospholipase C substrate or to the activation of protein kinase C by inositol 1,4,5-trisphosphate-mobilized Ca2+ and elevated 1,2-diacylglycerol levels.
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PMID:Homologous desensitization of the endothelin-1 receptor mediated phosphoinositide response in cultured neonatal rat cardiomyocytes. 838 49

In cultured vascular smooth muscle cells, angiotensin II and endothelin stimulate a variety of intracellular signals, including generation of inositol trisphosphate and diacylglycerol, mobilization of intracellular calcium, and activation of protein kinase C. These latter two events have been shown to mediate the phosphorylation of numerous proteins, but these substrates and the specific pathways mediating their phosphorylation have not been identified in vascular smooth muscle. Angiotensin II (100 nM, 10 min) induced a characteristic pattern of protein phosphorylation, which included the phosphorylation of many proteins, ranging in molecular mass from 20 to 76 kD. Three of these proteins have been identified as vimentin (M(r) 57,000), a specific protein kinase C substrate (M(r) 76,000) and the myosin light chain (M(r) 20,000). The 76-kD protein was one of the most highly phosphorylated proteins after agonist treatment. Endothelin-1 produced an identical pattern of phosphorylation. Five of these substrates were also phosphorylated by phorbol-12-myristate-13-acetate, and 5 were also phosphorylated after treatment with ionomycin. In general, the protein-kinase-C-dependent phosphorylations were sustained, while those mediated by calcium were rapid. Since these experiments were performed in cultured, phenotypically modulated cells stimulated with agents that promote cellular hypertrophy or hyperplasia, this pattern of phosphorylation may be representative of that seen during the growth response.
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PMID:Angiotensin-II-and endothelin-induced protein phosphorylation in cultured vascular smooth muscle cells. 839 84

Endothelin-1, a vasoactive peptide originally isolated from vascular endothelial cell culture supernatants, has constricting or mitogenic effects on smooth muscle and glomerular mesangial cells. Whether or not cultured rat glomerular epithelial cells synthesize endothelin-1 was assessed. Under basal culture conditions, the synthesis and release of endothelin-1 peptide by glomerular epithelial cells was time dependent, reaching 0.231 +/- 0.017 pg/1,000 cells at 24 h. For comparison, unstimulated bovine pulmonary artery endothelial cells and rat mesangial cells produced 0.982 +/- 0.237 and 0.004 +/- 0.002 pg of endothelin-1 peptide/1,000 cells per 24 h, respectively. In addition to endothelin-1 peptide, unstimulated glomerular epithelial cells expressed preproendothelin-1 mRNA. Transforming growth factor-beta, complement C5b-9, thrombin, and phorbol myristate acetate significantly enhanced endothelin-1 peptide synthesis in glomerular epithelial cells (45, 15, 55, and 25% above basal levels at 24 h, respectively), whereas epidermal growth factor had no effect. Thrombin and phorbol myristate acetate appeared to stimulate endothelin-1 peptide by activating protein kinase C, because the protein kinase inhibitor 1-(5-isoquinolinyl-sulfonyl)-3-methyl-piperazine abolished the thrombin- and phorbol myristate acetate-induced rise in endothelin-1 but had no effect on basal production. The stimulatory effect of thrombin was also markedly diminished in glomerular epithelial cells that had been depleted of protein kinase C by prolonged preincubation with a high dose of phorbol myristate acetate. Thus, glomerular epithelial cells may be an important source of endothelin-1, which might influence glomerular vasoconstriction or proliferation of target cells, particularly in the presence of proinflammatory molecules in the glomerulus.
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PMID:Glomerular epithelial cells produce endothelin-1. 843 51

Endothelin-1 (ET-1) was found to be a very potent stimulus for contraction and glycogenolysis in the perfused rat liver. At 1 nM it caused a dramatic increase in portal pressure of 22.1 +/- 2.7 cm water and enhanced the glucose output up to 3-fold. Extracellular Ca2+ and protein kinase C were involved in the signal transduction of ET-1. ET-1 action does not seem to be mediated by endogenous eicosanoids. The effects of ET-1 were significantly reduced in the presence of 1 microM Iloprost, a prostaglandin I2 analogue, or by 100 microM sin-1, a nitric oxide donor. In cultured hepatocytes, glycogenolysis was also stimulated by ET-1 although to an extent too small to explain the high glucose output found in the perfused liver.
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PMID:Regulation of endothelin-1 action on the perfused rat liver. 844 Mar 94

Endothelin-1 (ET-1) is an endothelium-derived vasoconstrictor peptide isolated from the culture supernatant of porcine aortic endothelial cells. This 21 amino-acid residue peptide has potent vasoconstrictive properties in vitro and in vivo. ET-1 action involves phosphatidylinositol turnover, calcium mobilization and protein kinase C activation. Endothelial cells have distinct receptors for different operating through hydrosoluble hormones. The aim of this study was to investigate on a possible role of angiotensin II (ANG II) to modulate the release ET-1 from human endothelial cells in vitro. These data revealed a time- and a dose-dependent increase of ET-1 production in response to ANG II. This mechanism may have important pathophysiological implications in vivo. In fact, a double-mechanism of secretion of ET-1 from endothelial cells could exist: one active in a physiological condition and an other in response to a vasoconstrictor stimuli (as well as ANG II). Furthermore, these results may suggest an additional favourable effect of ACE-inhibition in human hypertension therapy.
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PMID:[Angiotensin II stimulates endothelin-1 release from human endothelial cells]. 848 29

Endothelin-1 (ET-1) is known to induce the contraction and proliferation of glomerular mesangial cells. Because ET-1 was found to stimulate the tyrosine phosphorylation of unidentified cellular proteins in cultured mesangial cells, protein tyrosine kinase might serve as one of the important signals leading to various functions of ET-1. Focal adhesion kinase (p125FAK) is a newly identified cytoplasmic protein tyrosine kinase that is activated by the phosphorylation of its own tyrosine residue. Because p125FAK was found to play a role in the signal transduction of not only integrins but also various neurotransmitters, including bombesin, endothelin, and vasopressin in Swiss 3T3 cells and Rat-1 fibroblasts, whether ET-1 could stimulate the tyrosine phosphorylation of p125FAK in glomerular mesangial cells was examined. ET-1 stimulated the tyrosine phosphorylation of p125FAK by threefold to fourfold in cultured mesangial cells. This effect of ET-1 was detected at 1 min and reached a maximum within 5 min and was blocked by BQ-123, an antagonist for ETA receptor. A23187, a calcium ionophore, failed to stimulate the tyrosine phosphorylation of p125FAK, and ET-1 was able to stimulate the tyrosine phosphorylation of p125FAK, even in a calcium-free medium. The activation of protein kinase C (PKC) by phorbol 12, 13-dibutyrate resulted in a stimulation of the tyrosine phosphorylation of p125FAK, and an inhibition of PKC by calphostin C or staurosporine significantly reduced the effect of ET-1. Furthermore, prolonged treatment of the cells with phorbol 12, 13-dibutyrate markedly inhibited the ET-1-induced tyrosine phosphorylation of p125FAK. These results indicate that p125FAK might play a role in a signal transduction system of ET-1 in glomerular mesangial cells and that the ET-1-induced tyrosine phosphorylation of p125FAK is largely dependent on the PKC pathway.
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PMID:Endothelin-1 stimulates tyrosine phosphorylation of p125 focal adhesion kinase in mesangial cells. 858 30


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