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)

Agonist-stimulated release of prostacyclin (PGI2) from endothelial cells requires elevation of the concentration of intracellular ionized calcium ([Ca2+]i) above a threshold value, and raised [Ca2+]i provides a sufficient transduction signal to account for the extent of PGI2 production. However, chronic activation of protein kinase C has been reported separately to potentiate PGI2 release, but to depress agonist-induced elevations of [Ca2+]i. We show here that pretreatment with phorbol 12-myristate 13-acetate (PMA) dose-dependently induces PGI2 release over many minutes after a significant lag period without any change in [Ca2+]i. In addition, PMA potentiates the transient release of PGI2 in response to agonists in a complex manner depending on the time of pre-incubation and the concentrations of both PMA and agonist. Concomitant measurement of [Ca2+]i and PGI2 release demonstrates that PMA pretreatment dose-dependently inhibits both the peak [Ca2+]i transient and the subsequent steady-state elevation of [Ca2+]i in response to agonists. Determination of the quantitative [Ca2+]i/PGI2 dose/response relationship, when PGI2 release is driven purely by elevating [Ca2+]i with ionomycin, demonstrates that PMA also enhances the Ca2+-sensitivity of PGI2 release. The observed effects of PMA on PGI2 release can be explained quantitatively by its abilities to lower the threshold [Ca2+]i required for PGI2 synthesis and to depress the peak [Ca2+]i evoked by agonist. We propose that these effects are due respectively to actions of PMA on phospholipase A2 and on a G-protein (Gp) that couples activated receptors to phospholipase C.
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PMID:Protein kinase C activation alters the sensitivity of agonist-stimulated endothelial-cell prostacyclin production to intracellular Ca2+. 250 28

In order to elucidate the role of guanine-nucleotide-binding proteins (G-proteins) in endothelial prostacyclin (PGI2) production, human umbilical vein endothelial cells, prelabelled with either [3H]inositol or [3H]arachidonic acid, were stimulated with the non-specific G-protein activator aluminium fluoride (AlF4-). AlF4- caused a dose- and time-dependent generation of inositol phosphates, release of arachidonic acid and production of PGI2. The curves for the three events were similar. When the cells were stimulated in low extracellular calcium (60 nM), they released [3H]arachidonic acid and produced PGI2, but depleting the intracellular Ca2+ stores by pretreatment with the Ca2+ ionophore A23187 totally inhibited both events, although the cells still responded when extracellular Ca2+ was added. The Ca2+ ionophore did not inhibit the generation of inositol phosphates in cells maintained at low extracellular Ca2+. Pertussis toxin pretreatment (14 h) altered neither inositol phosphate nor PGI2 production in response to AlF4-. To investigate the functional role of the diacylglycerol/protein kinase C arm of the phosphoinositide system, the cells were pretreated with the protein kinase C activator 12-O-tetradecanoylphorbol 13-acetate (TPA) or the protein kinase C inhibitor 1-(5-isoquinolinylsulphonyl)-2-methylpiperazine (H7). TPA inhibited the AlF4(-)-induced inositol phosphate generation but stimulated both the release of arachidonic acid and the production of PGI2. H7 had opposite effects both on inositol phosphate generation and on PGI2 production. These results suggest that AlF4(-)-induced PGI2 production is mediated by a pertussis-toxin-insensitive G-protein which activates the phosphoinositide second messenger system. This production of PGI2 can be modulated by protein kinase C activation, both at the level of inositol phosphate generation and at the level of arachidonic acid release.
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PMID:Endothelial inositol phosphate generation and prostacyclin production in response to G-protein activation by AlF4-. 251 51

The terminal differentiation of Ob1771 pre-adipose cells induced by arachidonic acid in serum-free hormone-supplemented medium containing insulin, transferrin, growth hormone, tri-iodothyronine and fetuin (5F medium) was strongly diminished in the presence of inhibitors of prostaglandin synthesis, namely aspirin or indomethacin. Carbaprostacyclin, a stable analogue of prostacyclin (prostaglandin I2) known to be synthesized by pre-adipocytes and adipocytes, behaved as an efficient activator of cyclic AMP production and was able, when added to 5F medium, to mimic the adipogenic effect of arachidonic acid. Prostaglandins E2, F2 alpha and D2, unable to affect the cyclic AMP production, failed to substitute for carbaprostacyclin. However, prostaglandin F2 alpha, which is another metabolite of arachidonic acid in pre-adipose and adipose cells, able to promote inositol phospholipid breakdown and protein kinase C activation, potentiated the adipogenic effect of carbaprostacyclin. In addition, carbaprostacyclin enhanced both a limited proliferation and terminal differentiation of adipose precursor cells isolated from rodent and human adipose tissues maintained in primary culture. These results demonstrate the critical role of prostacyclin and prostaglandin F2 alpha on adipose conversion in vitro and suggest a paracrine/autocrine role of both prostanoids in the development of adipose tissue in vivo.
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PMID:Prostacyclin as a potent effector of adipose-cell differentiation. 253 85

Endothelial cells responses to a variety of agonists include release of endothelium dependent vasodilators, such as endothelium dependent relaxing factor (EDRF) and prostacyclin (PGI2). These substances act on vascular smooth muscle to cause relaxation and also have potent anti-aggregatory effects on platelets. A study of the mechanisms of signal transduction involved in these processes was undertaken. An investigation of intracellular calcium using FURA-2 and INDO-1 loaded endothelial cells shows transient elevation in response to vasodilator agonists. The calcium content of endothelial cells calculated using 45Ca flux techniques is increased in response to bradykinin and thrombin. Receptor activation leads to increased phosphoinositide turnover in endothelial cells and activates protein kinase C, the latter may be involved in feedback regulation. Patch clamp studies have demonstrated receptor-operated ionic channels in the endothelial cell membrane. Thus, intracellular calcium concentration is elevated in response to receptor activation, both as a result of liberation of calcium from intracellular stores and calcium entry from extracellular sources. Endothelial cells also respond to particulate stimuli. They can selectively bind and phagocytize bacteria. Phagocytosis leads to generation of superoxide aionin, a process which also seems to be controlled by elevation of intracellular calcium and activation of protein kinase C. In addition phagocytosis activates endothelial cells resulting in increased migration, division and further phagocytosis. All in all, the plethora of different endothelial responses to a variety of stimuli suggests a complex and multipotent cell type.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Endothelium as a transducing surface. 254 30

Angiogenin stimulates capillary and umbilical vein endothelial cell prostacyclin secretion but not that of prostaglandins of the E series. The response was quantitated by radioimmunoassay and by [3H]arachidonate labeling followed by analysis of the secreted prostaglandins. The stimulated secretion lasts for several minutes and is optimal at 2-4 min. The dose-response (peak at 1-10 ng/ml) is similar to that previously observed for activation of endothelial cell phospholipase C. Stimulated secretion was blocked by pretreatment with the inhibitors of prostacyclin synthesis, indomethacin and tranylcypromine, and also the specific inhibitor of phospholipase A2, quinacrine, as well as pertussis toxin and the diglyceryl and monoglyceryl lipase inhibitor RHC 80267. Stimulated secretion was also abolished in cells that were either pretreated for 48 hr with phorbol ester to down-regulate protein kinase C or incubated with the protein kinase inhibitor H7. Hydrolysis of phosphatidylinositol by phospholipase A2 appears to be the source of angiogenin-mobilized arachidonate; angiogenin-induced hydrolysis of phosphatidylcholine was not detected. Activation of phospholipase A2 occurs in the absence of an angiogenin-induced calcium flux. The results are discussed in terms of mechanisms of agonist-induced intracellular arachidonate mobilization and relevance to angiogenesis.
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PMID:Angiogenin stimulates endothelial cell prostacyclin secretion by activation of phospholipase A2. 264 38

The role of the Ca2+-sensitive phospholipid-dependent protein kinase C (PKC) was studied in cultured rat aortic smooth-muscle cells, known to respond to angiotensin II (Ang II) by producing prostacyclin, determined by the release of 6-oxo-prostaglandin F1 alpha. PKC activity was measured in the cytosol and the solubilized membrane fraction after DEAE-cellulose chromatography using a linear NaCl gradient. Ang II stimulated the activity of PKC in the cytosolic and in the membrane fractions of aortic smooth-muscle cells. These increases in PKC activity were concentration-dependent and occurred rapidly, reaching a plateau within 10 min. In contrast, phorbol 12-myristate 13-acetate (PMA) rapidly decreased cytosolic PKC activity and at the same time increased membrane PKC activity to reach a plateau after 20 min. Cytosolic PKC activity from control and Ang II-stimulated cells was found to be less dependent on [Ca2+] than was the highly [Ca2+]-dependent membrane PKC activity from the same cells. In contrast, membrane PKC activity from PMA-treated cells was largely [Ca2+]-independent. In the presence of 10 nM-PMA, the sensitivity of cultured smooth-muscle cells towards Ang II was increased, and maximal values of Ang II-induced prostacyclin production were enhanced by about 60%. In cells incubated with both Ang II and PMA, an additive effect on membrane PKC activity was observed, whereas cytosolic PKC activity was suppressed as in cells treated with PMA alone. These results suggest that an increase of the membrane, but not the cytosolic, PKC activity represents a positive signal in the prostacyclin production induced by Ang II stimulation of aortic smooth-muscle cells. PMA seems to induce a state of activation of membrane PKC which does not need increased intracellular [Ca2+] to be fully expressed, whereas Ang II-stimulated membrane PKC activity requires higher Ca2+ concentrations. The possibility exists that the addition of both signals leads to the augmentation of Ang II-stimulated prostacyclin production.
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PMID:Effects of angiotensin II and of phorbol ester on protein kinase C activity and on prostacyclin production in cultured rat aortic smooth-muscle cells. 265 81

We examined the mechanisms by which the phospholipid-sensitive, calcium-dependent protein kinase (protein kinase C) regulates prostacyclin synthesis by ovarian cells. In monolayer cultures of swine granulosa cells, specific phorbol esters significantly augmented production of the stable immunoreactive metabolite of prostacyclin, 6-keto-prostaglandin F1 alpha by 3- to 8-fold. These stimulatory actions were dose (0.03-30 ng/ml) and time (24-96 h) dependent, could be reproduced by non-diterpene activators of protein kinase C, and were corroborated by high performance liquid chromatography and mass spectrometry. The rank order of potency of phorbol esters was 12-O-tetradecanoylphorbol 13-acetate (TPA) greater than phorbol 12,13-dibenzoate greater than phorbol 12,13-dibutyrate greater than pure phorbol base. TPA enhanced de novo synthesis of prostacyclin, and synergized with the divalent cation ionophore, A23187. Although prostacyclin synthetase activity was not induced, microsomal cyclooxygenase activity was significantly increased by phorbol treatment. Moreover, TPA doubled the intracellular accumulation of free arachidonic acid. An inhibitor of phospholipase A2 (quinacrine 100 microM) impeded, whereas melittin (0.01 microM), an activator of cellular phospholipase A2, and purified bacterial phospholipase A2 (5 and 50 mU/ml) both augmented prostacyclin production. RH 59022 (30 microM), an inhibitor of diacylglyceride lipase, also suppressed prostacyclin synthesis. We conclude that the protein kinase C effector pathway is functionally coupled to de novo prostacyclin production in the swine granulosa cell. Increased eicosanoid synthesis can be accounted for by enhanced phospholipase A2 and diacylglyceride lipase-mediated availability of arachidonic acid substrate and an activated cyclooxygenase enzyme without a change in prostacyclin synthetase activity.
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PMID:Mechanism(s) by which activation of protein kinase C is coupled to prostacyclin synthesis in granulosa cells. 275 27

Fructose 2,6-bisphosphate, the most potent activator of 6-phosphofructo-1-kinase, has been demonstrated to mediate the increase of glycolytic flux induced by mitogens human fibroblasts. In the present work the molecular basis of transmembrane control of fructose 2,6-bisphosphate has been investigated. Prostacyclin and isoprenaline, known to activate adenylate cyclase, are able to increase fructose 2,6-bisphosphate levels, indicating that in human fibroblasts cyclic AMP plays a positive role in the control of the metabolite concentration, opposite to that exerted in hepatocytes. Substances known to activate protein kinase C such as phorbol 12-myristate 13-acetate, or to stimulate phosphoinositide turnover such as thrombin and bradykinin are also effective in raising fructose 2,6-bisphosphate. Therefore, we conclude that cyclic AMP and protein kinase C are likely involved in the control of fructose 2,6-bisphosphate levels in human fibroblasts.
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PMID:Adenylate cyclase stimulating agents and mitogens raise fructose 2,6-bisphosphate levels in human fibroblasts. Evidence for a dual control of the metabolite. 282 Jul 97

Treatment of intact human platelets with the tumour-promoting phorbol ester, phorbol 12-myristate 13-acetate (PMA), specifically inhibited PGD2-induced cyclic AMP formation without affecting the regulation of cyclic AMP metabolism by PGI2, PGE1, 6-keto-PGE1, adenosine or adrenaline. This action of PMA was: (i) concentration-dependent; (ii) not mediated by evoked formation or release of endogenous regulators of adenylate cyclase activity (thromboxane A2 or ADP); (iii) mimicked by 1,2-dioctanoylglycerol (DiC8) but not by 4 alpha-phorbol 12,13-didecanoate (which does not activate protein kinase C); (iv) attenuated by Staurosporine. These results indicate that activation of protein kinase C in platelets may provide a regulatory mechanism to abrogate the effects of the endogenous adenylate cyclase stimulant PGD2 without compromising the effects of exogenous stimulants of adenylate cyclase (PGI2, 6-keto-PGE1, adenosine).
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PMID:Effects of protein kinase C activation on human platelet cyclic AMP metabolism. 282 Aug 6

The role of G proteins and protein kinase C in mediating muscarine receptor-linked prostanoid synthesis by the rat urinary bladder was investigated using the G protein activator, sodium fluoride (NaF); the protein kinase C activators, phorbol myristate (PMA) and phorbol dibutyrate (PDBU); the protein kinase C inhibitor, H7, and the parasympathomimetic, carbachol. NaF stimulated in vitro rat urinary bladder prostacyclin (PGI2) synthesis (EC50 = 6 mmol.l-1), an action inhibited by the presence of EDTA (10 mmol.l-1). Carbachol potentiated the stimulatory action of NaF. NaF (10 mmol.l-1)-stimulated PGI2 synthesis was inhibited by the calcium channel blockers verapamil, nifedipine and the protein kinase C inhibitor, H7, in concentration-dependent manners. Carbachol-stimulated PGI2 synthesis was also inhibited by H7. PDBU and PMA were without effect on de novo, NaF- or carbachol-stimulated urinary bladder PGI2 synthesis. Other prostanoids (PGF2 and PGF2 alpha) were stimulated to the ame degree as PGI2 by NaF, and inhibited equally by H7 and calcium channel blockers. Dibutyryl adenosine 3':5'-cyclic monophosphate was without effect on de novo or NaF-stimulated prostanoid synthesis. Since fluoride activates G proteins, these data indicate that: (1) muscarine receptor-prostanoid synthesis coupling is mediated by G proteins in the rat urinary bladder; (2) fluoride action is mediated by protein kinase C and not adenyl cyclase, probably through activation of phospholipase C and therefore the generation of the protein kinase C activator, diacyl glycerol; (3) activated protein kinase C may initiate Ca2++ mobilisation linked to prostanoid synthesis; and (4) the lack of effect of the phorbol esters on urinary bladder PGI2 synthesis, in contrast to that on other smooth muscle, indicates that in different smooth muscle tissues there are varying forms of protein kinase C.
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PMID:Fluoride but not phorbol esters stimulate rat urinary bladder prostanoid synthesis: investigations into the roles of G proteins and protein kinase C. 282 37


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