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)

We have recently shown that glutamate exerts a stimulatory action on somatostatin secretion in cortical neurons essentially through NMDA receptor sites. Here, we investigated whether arachidonic acid release could be modified after NMDA receptor activation in cortical neurons in primary culture. We also studied whether pharmacological manipulation of phospholipase A2 could modify somatostatin release. We found that both glutamate and NMDA (N-methyl-D-aspartate) stimulated [3H]arachidonic acid release. NMDA-evoked arachidonic acid release was inhibited by MK-801 and TCP (two NMDA receptor-type antagonists), or by mepacrine, an inhibitor of phospholipase A2. NMDA-induced somatostatin release was inhibited by MK-801, mepacrine and by another phospholipase A2 inhibitor, p-bromophenacylbromide (pBPB). However, responses to NMDA were unaffected by H7, NDGA (nordihydroguaiaretic acid), indomethacin or by RHC 80267 (inhibitors of protein kinase C, lipooxygenase, cyclooxygenase and diacylglycerol lipase, respectively). Mepacrine (greater than or equal to 100 microM) decreased NMDA-stimulated phosphatidylinositol (PI) hydrolysis and at higher concentrations (250 microM) was also able to inhibit basal release whereas pBPB had no effect in the range of concentrations tested. Neomycin (which inhibits phosphatidylinositol metabolism by binding strongly and selectively to inositol phospholipids) reduced by 30% the NMDA-stimulated somatostatin release, although chronic treatment of neurons with the phorbol ester 12-myristate, 13-acetate (PMA) had no effect on this response. Melittin, an activator of phospholipase A2, was able to stimulate both arachidonic acid release and somatostatin secretion. High-performance liquid chromatography (HPLC) analysis of tritiated metabolites released from cortical neurons under basal or NMDA-stimulated conditions revealed that [3H]arachidonic acid was the only metabolite detectable. Furthermore, external addition of arachidonic acid increased somatostatin secretion. Our results show a correlation between the two parameters studied.
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PMID:NMDA receptor activation stimulates phospholipase A2 and somatostatin release from rat cortical neurons in primary cultures. 135 46

The activation of protein kinase C was investigated in digitonin-permeabilized human neuroblastoma SH-SY5Y cells by measuring the phosphorylation of the specific protein kinase C substrate myelin basic protein4-14. The phosphorylation was inhibited by the protein kinase C inhibitory peptide PKC19-36 and was associated to a translocation of the enzyme to the membrane fractions of the SH-SY5Y cells. 1,2-Dioctanoyl-sn-glycerol had no effect on protein kinase C activity unless the calcium concentration was raised to concentrations found in stimulated cells (above 100 nM). Calcium in the absence of other activators did not stimulate protein kinase C. Phorbol 12-myristate 13-acetate was not dependent on calcium for the activation or the translocation of protein kinase C. The induced activation was sustained for 10 min, and thereafter only a small net phosphorylation of the substrate could be detected. Calcium or dioctanoylglycerol, when applied alone, only caused a minor translocation, whereas in combination a marked translocation was observed. Arachidonic acid (10 microM) enhanced protein kinase C activity in the presence of submaximal concentrations of calcium and dioctanoylglycerol. Quinacrine and p-bromophenacyl bromide did not inhibit calcium- and dioctanoylglycerol-induced protein kinase C activity at concentrations which are considered to be sufficient for phospholipase A2 inhibition.
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PMID:Activation of protein kinase C in permeabilized human neuroblastoma SH-SY5Y cells. 137 89

In cloned osteoblast-like cells, MC3T3-E1, prostaglandin F2 alpha (PGF2 alpha) stimulated arachidonic acid (AA) release in a dose-dependent manner in the range between 1 nM and 10 microM. 12-O-tetradecanoylphorbol-13-acetate (TPA), a protein kinase C (PKC) activator, which by itself had little effect on AA release, markedly amplified the release of AA stimulated by PGF2 alpha in a dose-dependent manner. 4 alpha-phorbol 12,13-didecanoate, a phorbol ester which is inactive for PKC, showed little effect on the PGF2 alpha-induced AA release. 1-oleoyl-2-acetylglycerol (OAG), a specific activator for PKC, mimicked TPA by enhancement of the AA release induced by PGF2 alpha. H-7, a PKC inhibitor, markedly suppressed the effect of OAG on PGF2 alpha-induced AA release. Quinacrine, a phospholipase A2 inhibitor, showed partial inhibitory effect on PGF2 alpha-induced AA release, while it suppressed the amplification by OAG of PGF2 alpha-induced AA release almost to the control level. Furthermore, TPA enhanced the AA release induced by melittin, known as a phospholipase A2 activator. On the other hand, TPA inhibited the formation of inositol trisphosphate stimulated by PGF2 alpha. Under the same condition, PGF2 alpha indeed stimulated prostaglandin E2 (PGE2) synthesis and TPA markedly amplified the PGF2 alpha-induced PGE2 synthesis as well as AA release. These results indicate that the activation of PKC amplifies PGF2 alpha-induced both AA release and PGE2 synthesis through the potentiation of phospholipase A2 activity in osteoblast-like cells.
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PMID:Protein kinase C activation amplifies prostaglandin F2 alpha-induced prostaglandin E2 synthesis in osteoblast-like cells. 140 Jun 12

Although several cytokines have been demonstrated to exert pleiotropic responses, there is little information on cytokine regulation of renal tubular epithelial cell function. In the present studies, we find that both T cell-derived (tumor necrosis factor-beta and interleukins 2 and 3) and monocyte/macrophage derived (tumor necrosis factor alpha and interleukin 1 beta) cytokines promote basal, arginine vasopressin- and forskolin-stimulated adenylate cyclase activity in cultured LLC-PK1 cells. No effect of TNF, IL-1 beta, and IL-2 to stimulate protein kinase C activity was observed. TNF-beta, IL-1 beta and IL-2 also modestly stimulated 3H release from 3H-arachidonic acid labeled cells. Mepacrine, a phospholipase A inhibitor, prevented TNF-beta stimulation of 3H release from 3H-arachidonic acid labeled cells and TNF-beta potentiation of adenylate cyclase activity. TNF-beta potentiation of adenylate cyclase activity and stimulation of 3H release from 3H arachidonic acid labeled cells was not prevented by pertussis toxin. These results demonstrate that several cytokines can stimulate adenylate cyclase activity while not affecting protein kinase C activity in cultured renal tubular epithelial cells. The effect of TNF-beta to stimulate adenylate cyclase appears to occur independent of pertussis toxin-sensitive substrate and may involve activation of phospholipase A.
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PMID:Cytokine regulation of adenylate cyclase activity in LLC-PK1 cells. 140 34

Changes in intracellular calcium influence epithelial barrier integrity, but the mechanism of action is unknown. One possibility is that calcium may work by increasing phospholipase A2 (PLA2) and/or phospholipase C (PLG) activity. Measuring the mannitol permeability (Pmann) of cultured monolayers of Madin-Darby canine kidney (MDCK) epithelium cells as a measure of barrier integrity, we found that exposure of the monolayers to 5 and 10 microM A23187 produced an increase in Pmann whereas 1 microM A23187 did not. Exposure of MDCK cells labeled with [3H]arachidonate to A23187 resulted in an increase in both PLA2 activity, as measured by an increase in free fatty acids, and in PLC activity, as measured by an increase in diacylglycerol (DAG). The increase in DAG was due to an increase in phosphatidylcholine-specific PLC activity. The relationship of phospholipolysis to Pmann was evaluated further by the use of mepacrine and dexamethasone. Mepacrine (10 microM) decreased PLA2 activity by 60% but had no effect on increased Pmann after exposure to A23187. Preexposure of the monolayers to dexamethasone (10 microM) blocked both PLA2 activity and PLC activity and also prevented the increase in Pmann after exposure to A23187. To evaluate whether this protective effect of dexamethasone was due to PLC blockade, we incubated the cells with the protein kinase C blocker H-7. Incubation with H-7 offered no protection from increased Pmann after A23187. These results demonstrate that increased intracellular calcium decreases the barrier integrity of epithelium and increases both PLA2 and phosphatidylcholine-specific PLC activity. The increase in Pmann, however, appears to occur through mechanisms other than phospholipase activation.
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PMID:A23187 increases permeability of MDCK monolayers independent of phospholipase activation. 211

We investigated the involvement of arachidonate in the PRL secretory process using three experimental systems: hemipituitary glands incubated in vitro, cultured pituitary cells, and dispersed anterior pituitary cells perifused in columns. Arachidonate (100 microM) significantly (P less than 0.05) stimulated PRL release in the former system and stimulated PRL secretion in a dose-related manner in cultured cells. In hemipituitary glands, indomethacin, a cyclooxygenase inhibitor, potentiated the arachidonate-mediated stimulation, whereas nordihydroguaiaretic acid or BW755c abolished it. The latter two agents, but not indomethacin, abolished the effect of phospholipase A2 on PRL release in vitro. BW755c also inhibited the stimulatory effect of TRH on PRL release in both experimental systems. Conversely, the stimulation of PRL release by phorbol myristate acetate (PMA), although significantly reduced, was not abolished by either nordihydroguaiaretic acid or BW755c. Quinacrine, a phospholipase A2 inhibitor, also abolished the stimulatory effect of phospholipase A2 or TRH on PRL release. In cultured cells, quinacrine inhibits basal PRL release, but does not affect PRL release induced by arachidonate or (Bu)2 cAMP. These results more firmly establish a role for arachidonate as an intracellular mediator of PRL release and suggest the involvement of an arachidonate metabolic pathway(s) (lipoxygenase and epoxygenase) other than prostaglandin or thromboxane formation. The effect of PMA on PRL release may be attributable only in part to an increase in the production of arachidonate metabolites, and most of PMA's effect on PRL release may relate to its activation of protein kinase C.
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PMID:Arachidonate stimulates prolactin release in vitro: a role for the fatty acid and its metabolites as intracellular regulator(s) in mammotrophs. 298 Oct 65

The present study investigated the signal-transduction pathway responsible for the epidermal growth factor (EGF) stimulation of phosphate transport (JPhos) in the rabbit proximal convoluted tubule (PCT). Genistein, 10(-4) M, bath and lumen, an inhibitor of EGF receptor tyrosine kinase activity, blocked the EGF effect on JPhos, consistent with a role for tyrosine kinase in the signal-transduction pathway. Both staurosporine (5 x 10(-8) M) and calphostin C (10(-8) M), inhibitors of protein kinase C, blocked the EGF stimulation of JPhos, indicating that protein kinase C is involved in EGF signaling. Intracellular calcium (Ca2+i) concentrations were measured in perfused tubules using fura PE3 to determine whether changes in Ca2+i were also part of the signaling pathway. After addition of 3 nM EGF, there was no change in Ca2+i, suggesting that stimulation of protein kinase C is not from phosphatidylinositol hydrolysis by phospholipase C-gamma. To determine whether phospholipase A2 (PLA2) is involved, the inhibitor mepacrine was used. Mepacrine (5 x 10(-5) M) had no direct effect on PCT transport but blocked the stimulatory effect of EGF on JPhos. PLA2 activity, assessed as free arachidonic acid release from proximal tubules in suspension, increased by 18.8% with 3 nM EGF. Thus the stimulation of JPhos by EGF is mediated via a signal-transduction pathway involving tyrosine kinase, protein kinase C, and PLA2.
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PMID:Stimulation of proximal convoluted tubule phosphate transport by epidermal growth factor: signal transduction. 757 82

The phenanthrenemethanol antimalarial halofantrine is a potent inhibitor of bovine heart and rat liver cyclic AMP-dependent protein kinase catalytic subunit (cAK) (IC50 values 2.1 microM and 0.6 microM, respectively). The inhibition of rat liver cAK by halofantrine is non-competitive with respect to both ATP and to the synthetic peptide substrate employed (LRRASLG). Halofantrine is a poor inhibitor of calmodulin-dependent myosin light chain kinase (MLCK) and wheat embryo Ca(2+)-dependent protein kinase (CDPK) and does not inhibit rat brain Ca(2+)- and phospholipid-dependent protein kinase C (PKC). In contrast, the acridine-based antimalarial quinacrine and a variety of quinoline-based antimalarials are very poor inhibitors of cAK, the best inhibitor being chloroquine (IC50 for bovine heart cAK, 80 microM). Quinacrine and the quinoline-based antimalarials variously inhibit CDPK, PKC and MLCK albeit at relatively high concentrations (about 1 to 4 x 10(-4) M), the best inhibitors found being primaquine, pentaquine and mefloquine (IC50 values for MLCK 49, 103 and 33 microM, respectively). A number of phenanthrene derivatives having a 9-hydroxy or 9-keto substituent, namely phenanthrenequinone, 6(5H)-phenanthridinone and 9-phenanthrol are potent inhibitors of bovine heart cAK (IC50 values 8, 10 and 10 microM, respectively) and of MLCK (IC50 values 6, 53 and 10 microM, respectively). The selective, high affinity interaction of halofantrine with cAK may contribute to biological effects in vivo of this clinically-employed antimalarial compound.
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PMID:Specific inhibition of cyclic AMP-dependent protein kinase by the antimalarial halofantrine and by related phenanthrenes. 781 92

Although bile salts are irritants in the gastric mucosa, their effects on prostaglandin (PG) release have not been well studied. We investigated the effects of bile salts on PGE2 release and the possible mechanisms involved. Cultured rabbit gastric mucous epithelial cells were studied. PGE2 was measured by radioimmunoassay. Intracellular free Ca2+ concentration was measured with Ca2+ fluorescent dye indo-1 AM. Dihydroxy bile salts, such as chenodeoxycholate and deoxycholate (DC), dose-dependently increased PGE2 release, while non-dihydroxy bile salts did not. Since agents involved in the cellular signal transduction system have been reported to play important roles in PG release, the possible involvement of Ca2+, calmodulin, and protein kinase C (PKC) in DC-induced PGE2 release was studied. Deprivation of Ca2+ from the medium blocked DC-induced PGE2 release. Lanthanum (La3+), which displaced surface-bound Ca2+, suppressed DC-induced PGE2. However, BAPTA (a chelator of intracellular Ca2+) did not decrease it. Neither calmodulin inhibitors nor PKC inhibitors altered DC-induced PGE2 release. DC increased intracellular free Ca2+ concentrations. This effect was blocked by deprivation of Ca2+ from the medium. Quinacrine (a phospholipase A2 inhibitor) blocked DC-induced PGE2 release. These results suggest that in cultured rabbit gastric cells, deoxycholate stimulates PGE2 release mainly through the influx of extracellular Ca2+.
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PMID:Stimulation of prostaglandin E2 release from cultured rabbit gastric cells by sodium deoxycholate. 793 14

Prostaglandin (PG) has been reported to be one of the important protective factors in the gastric mucosa. However the mechanism of the regulation of endogenous PG production has not been well studied. We investigated the possible roles of Ca2+, cAMP, and protein kinase C (PKC) in the regulation of PGE2 release from cultured rabbit gastric mucosal cells. PGE2 was measured by radioimmunoassay. A23187 (Ca2+ ionophore) at 2 x 10(-6) M significantly increased PGE2 release. Deprivation of Ca2+ from the medium blocked the A23187-induced increase of PGE2. TMB-8 (a putative inhibitor of Ca2+ release from intracellular stores) did not have any significant effects on the increase of PGE2-induced by A23187. Thus, A23187 increased PGE2 through the influx of extracellular Ca2+. W7 or compound 48/80 (calmodulin inhibitors) did not alter the response of PGE2 caused by A23187. Exogenous administration of cAMP, forskolin (an activator of adenylate cyclase), or 2-chloroadenosine (a possible activator of adenylate cyclase through adenosine A2 receptor) had neither significant effects on PGE2 release nor an effect on A23187-induced increase of PGE2 release. 12-O-tetradecanoylphorbol 13-acetate (TPA, an activator of PKC) significantly stimulated PGE2 release in a dose-dependent fashion, whereas another phorbol ester with no biological activity did not. A23187 at 0.8 x 10(-6) M, but not cAMP, potentiated the TPA-induced increase of PGE2. Mepacrine (a phospholipase A2 inhibitor) reduced the A23187- and TPA-induced increase of PGE2. These results suggest that Ca2+ and protein kinase C may play important roles in the regulation of PGE2 release by cultured rabbit gastric cells.
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PMID:Roles of Ca2+ and protein kinase C in regulation of prostaglandin E2 release by cultured rabbit gastric epithelial cells. 839 56


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