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)

Studies were made of inhibition by wortmannin, a fungal metabolite, of human platelet responses to various stimuli. Wortmannin at concentrations as low as 1-100 nM inhibited several receptor-agonist-induced 5-hydroxytryptamine release from platelets, without affecting agonist-induced increases in the intracellular concentration of Ca2+. Phorbol 12-myristate 13-acetate (PMA), an active tumour promoter, caused 5-hydroxytryptamine release when combined with a low concentration of ionomycin, and platelet aggregation by itself; these effects of the phorbol ester were also inhibited by wortmannin as well as by staurosporine, a potent, although non-specific, protein kinase C (PKC) inhibitor, in a similar molar concentration range. The platelet responses to the receptor agonists or PMA were accompanied by increased incorporation of [32P]Pi into pleckstrin, a protein selectively expressed in platelets and other blood cells arising from haematopoietic stem cells, as a result of PKC activation in the intact cells. The pleckstrin phosphorylation was inhibited by wortmannin in ways mostly similar to those in which it inhibited the 5-hydroxytryptamine-release responses. Nevertheless, wortmannin failed to inhibit PKC activity measurable in a cell-free assay system which is highly susceptible to staurosporine. Nor did it inhibit the translocation of cytosolic PKC to membranes induced by addition of PMA to platelet cells. Thus wortmannin, which is not a direct inhibitor of PKC, could interfere with the kinase-dependent phosphorylation of pleckstrin, which may play an important role in the cellular responses to receptor stimulation.
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PMID:Suppression by wortmannin of platelet responses to stimuli due to inhibition of pleckstrin phosphorylation. 149 12

Recruitment of inflammatory cells to the lung capillaries has been proposed as an important step in the sequence of events that lead to acute lung injury. Frequently, in the clinical setting, bacteremia and sepsis syndrome precede the acute lung failure and endotoxin priming may represent a comparable paradigm, useful for experimental pursuit. Following addition of the chemotactic tripeptide FMLP (10(-9) to 10(-6) M) to the cell-free, salt solution perfusate of isolated rat lungs, only a small degree of vasoconstriction was observed. However, in lungs isolated from rats that received 2 mg/kg intraperitoneal Salmonella enteritidis endotoxin 2 h before lung perfusion, FMLP dose dependently caused a large, transient pulmonary pressor response, edema formation, and release of large amounts of thromboxane and leukotriene B4. Since in vitro priming with endotoxin, direct vascular injury by neutrophil elastase, nor direct stimulation with FMLP of pulmonary artery rings from endotoxin-pretreated rats, mimicked the effects of in vivo endotoxin priming, we conclude that the presence of inflammatory cells in the lung capillaries accounted for the large amount of eicosanoids produced by the lungs after FMLP stimulation. In fact, by retrograde lavage of the lung circulation with a collagenase solution, previously adherent cell clumps were mobilized and identified. These cell clumps, composed of red blood cells, neutrophils, and platelets, were not seen in the vascular lavage sediment obtained from unprimed control lungs. Indomethacin, a thromboxane antagonist, AA861, a 5-lipoxygenase inhibitor, and WEB 2086, a platelet-activating factor (PAF) antagonist, reduced the thromboxane synthesis and release after FMLP (10(-7) M) in in vivo endotoxin-primed lungs. None of the inhibitors employed exclusively inhibited only one particular eicosanoid mediator but rather affected the release of several mediators, suggesting a close link between the different synthetic arachidonic acid pathways. An inhibitor of phospholipase C (2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate), NCDC, but not an inhibitor of phospholipase D (Wortmannin) or of protein kinase C (staurosporine) inhibited the FMLP-stimulated pulmonary pressure rise and eicosanoid release in endotoxin-primed lungs in vivo. Our data suggest that eicosanoids (in particular thromboxane) released from cells trapped in the lung circulation, but not from constitutive lung cells, contribute to vasoconstriction and edema formation caused by the chemoattractant FMLP in endotoxin-primed lungs.
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PMID:FMLP causes eicosanoid-dependent vasoconstriction and edema in lungs from endotoxin-primed rats. 154 53

Activation of human neutrophils by receptor-mediated agonists, the Ca2+ ionophore A23187, or the protein kinase C activator phorbol myristate acetate all stimulated phospholipase D activity. This was demonstrated by the increased formation of phosphatidic acid, and in the presence of ethanol, phosphatidylethanol (PEt) accumulation. EGTA completely inhibited A23187-induced PEt formation, but only one-half of the fMLP-induced PEt accumulation. Staurosporin, an inhibitor of protein kinase C, strongly inhibited PMA-induced PEt formation, but actually stimulated the formation of PEt in response to fMLP by several-fold. Thus, increased cytosolic Ca2+ and activated protein kinase C can each lead to activation of phospholipase D, but neither is required for receptor-mediated activation of phospholipase D activity. Wortmannin is an irreversible inhibitor of the oxidative burst, but does not inhibit NADPH oxidase or known components of signal transduction. Wortmannin inhibited activation of phospholipase D in response to fMPL. It did not directly inhibit phospholipase D, as the response to A23187 was unaffected. Wortmannin did not inhibit other fMPL-stimulated events, such as aggregation or adherence. We conclude that inhibition by wortmannin defines a third pathway to activation of phospholipase D. Further, its effect on phospholipase D correlates with its effect on the respiratory burst.
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PMID:Activation of human neutrophil phospholipase D by three separable mechanisms. 210 52

We previously showed that protein kinase C (PKC) induces phosphatidylcholine-hydrolysing phospholipase D activation in osteoblast-like MC3T3-E1 cells and that tyrosine kinase is involved in this activation. Wortmannin, a potent inhibitor of phosphatidylinositol 3-kinase, markedly enhanced the formation of choline induced by 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of PKC in MC3T3-E1 cells. The effect of wortmannin was dose-dependent between 0.1 microM and 10 microM. ML-7, an inhibitor of myosin light chain kinase, had little effect on the TPA-induced formation of choline. Genistein, an inhibitor of protein tyrosine kinases, significantly suppressed the potentiation by wortmannin. These results strongly suggest that phosphatidylinositol 3-kinase is involved in the regulation of phospholipase D activation by PKC in osteoblast-like cells.
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PMID:Genistein inhibits potentiation by wortmannin of protein kinase C-activated phospholipase D in osteoblast-like cells. 766 10

Wortmannin, a selective inhibitor of phosphatidylinositol 3-kinase (PI3K), blocked insulin-induced activation of glycogen synthase (GS) and mitogen-activated protein kinase (MAPK) in rat adipocytes. These inhibitions were relatively specific, as wortmannin did not block GS activation by a protein kinase C (PKC) inhibitor, or MAPK activation by phorbol esters. Our findings suggest that PI3K is required for the activation of both GS and MAPK in rat adipocytes.
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PMID:Studies with wortmannin suggest a role for phosphatidylinositol 3-kinase in the activation of glycogen synthase and mitogen-activated protein kinase by insulin in rat adipocytes: comparison of insulin and protein kinase C modulators. 773 62

The induction of the AP-1 transcription factor has been ascribed to the early events leading to T lymphocyte activation. We have examined the possibility that stimulation of phospholipase D (PLD) may regulate activation of transcription factor AP-1 in human T cells by transfecting human T lymphocyte Jurkat cells with a plasmid containing an AP-1 enhancer element and a chloramphenicol acetyltransferase reporter gene. We have detected activatable PLD in Jurkat cells, and we have found that addition of phosphatidic acid (PA), the physiologic product of PLD action on phospholipids, is rapidly incorporated into Jurkat cells and leads to activation of transcription factor AP-1. Treatment of Jurkat cells with anti-CD3 mAb activated both PLD and transcription factor AP-1. Wortmannin, an inhibitor of receptor-coupled PLD activation, blocked the anti-CD3-induced increases in both PLD activity and AP-1 enhancer activity. We found a good correlation in the transfected cells between PLD activation and induction of AP-1 enhancer activity under different experimental conditions. Furthermore, ethanol, an inhibitor of the PLD pathway, blocked the anti-CD3-stimulated AP-1 enhancer activity. However, this anti-CD3-mediated response was not inhibited by neomycin, an inhibitor of phosphoinositide hydrolysis. The increases in AP-1 enhancer activity induced by PA or anti-CD3 mAb were efficiently abrogated by the presence of propranolol, an inhibitor of PA phosphohydrolase and protein kinase C (PKC). Furthermore, the PA- and the anti-CD3-induced increases in AP-1 enhancer activity were blocked by the presence of PKC inhibitors or by PKC down-regulation. These data indicate that PLD stimulation can activate the transcription factor AP-1 in T lymphocytes, and suggest that the induction of AP-1 enhancer factor activity by PA is mediated via PKC stimulation, either through a direct activating effect of PA or through PA-derived diacylglycerol formation. These data also provide evidence for a role of PLD-derived lipids in the induction of AP-1 enhancer activity resulting from stimulation of the TCR/CD3 complex, suggesting that increased PLD activity can play an important role in T lymphocyte activation.
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PMID:Involvement of phospholipase D in the activation of transcription factor AP-1 in human T lymphoid Jurkat cells. 807 60

We examined the roles of myosin light-chain kinase in platelet responses to ADP using wortmannin, which almost completely inhibited myosin light-chain kinase at 3-6 microM. This concentration of wortmannin did not affect ADP-induced changes in the shape of the platelets, but it markedly inhibited aggregation in platelet-rich plasma and washed platelets. ML-9, another inhibitor of myosin light chain kinase, elicited similar effects on the platelet responses to wortmannin. Electron microscopic studies showed that there was no wortmannin effect on the ADP-induced spheration of discoid platelets, pseudopod formation, or granule centralization. Wortmannin at concentrations which prevented myosin light-chain kinase also inhibited platelet aggregation induced by ADP in the presence of U46619, an analogue of thromboxane A2, which is a prerequisite for ADP-induced irreversible aggregation. Although wortmannin partially inhibited protein kinase C, the protein kinase C inhibitor Ro-31-7549 (5 microM) prevented neither ADP- or ADP/U46619-induced changes in the shape of the platelets nor aggregation. These results suggest that myosin light-chain kinase activation is a prerequisite for ADP-induced platelet aggregation, but not for changes in their shape.
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PMID:Roles of myosin light-chain kinase in platelet shape change and aggregation. 808 84

Phosphatidylinositol-3-kinase is an important enzyme for intracellular signaling. The microbial product wortmannin and some of its analogues have been shown to be potent inhibitors of phosphatidylinositol-3-kinase. The 50% inhibitory concentration for inhibition by wortmannin is 2 to 4 nM. Kinetic analysis demonstrates that wortmannin is a noncompetitive, irreversible inhibitor of phosphatidylinositol-3-kinase, with inactivation being both time- and concentration-dependent. Wortmannin has previously been reported to be an inhibitor of myosin light chain kinase but with an inhibitory concentration of 0.2 microM. Wortmannin was found not to be an inhibitor of phosphatidylinositol-4-kinase, protein kinase C, or protein tyrosine kinase. Wortmannin inhibited the formation of phosphatidylinositol-3-phosphates in intact cells. The results of the study suggest that wortmannin and its analogues may have utility as pharmacological probes for studying the actions of phosphatidylinositol-3-kinase.
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PMID:Wortmannin, a potent and selective inhibitor of phosphatidylinositol-3-kinase. 816 90

Thapsigargin-activated Ca2+ entry into platelets was examined in the presence of S-145, a thromboxane A2 receptor antagonist, to inhibit indirect effects by endogenously formed prostaglandin H2/thromboxane A2. With external Ca2+ present, 0.2 microM thapsigargin caused a prompt increase in intracellular Ca2+ concentration ([Ca2+]i) followed by a gradual increase. Pretreatment with 6 microM wortmannin, a specific inhibitor of myosin light chain kinase, partly inhibited the increase in [Ca2+]i. In Ca(2+)-free EGTA buffer, thapsigargin induced a smaller increase in [Ca2+]i, and subsequent addition of Ca2+ to the buffer caused a further prompt increase in [Ca2+]i, demonstrating external Ca2+ entry. Wortmannin only partly inhibited this entry of external Ca2+. The wortmannin-insensitive Ca2+ entry pathway remained open for more than 6 min in Ca(2+)-free buffer. On the other hand, when receptor agonists such as thrombin and U46619 were substituted for thapsigargin, activation of the wortmannin-insensitive Ca2+ entry was transient (Hashimoto et al., J. Biol. Chem (1992) 267, 17078-17081). In the presence of S-145 and wortmannin, thapsigargin stimulated phosphorylation of neither the 20-kDa myosin light chain nor the 47-kDa protein, a substrate of protein kinase C. These results suggest that thapsigargin induces external Ca2+ entry by two mechanisms: (1) a mechanism involving myosin light chain kinase; (2) a mechanism, not activated by receptor agonists, that is independent of the major protein kinases of platelets.
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PMID:Ca2+ entry pathways activated by the tumor promoter thapsigargin in human platelets. 826 42

Stimulation of B lymphocytes through the Ig receptor initiates a cascade of biochemical changes, which can ultimately lead to either activation and growth, or cell-cycle arrest and cell death. One of the critical events that occurs in both cases is the activation of tyrosine kinases, and the resulting phosphorylation of a variety of proteins on tyrosine residues. In this report we identify one of the substrates of phosphorylation as the 85-kD subunit of the enzyme phosphatidylinositol-3 kinase (PI3K), and show that both anti-IgM and anti-IgD stimulation results in an increase in the anti-phosphotyrosine-precipitable PI3K activity. Furthermore, we show that the potent and specific inhibitor of PI3K, Wortmannin, can completely abrogate anti-Ig-mediated growth inhibition without affecting tyrosine kinase induction or protein kinase C (PKC) activation. Treatment of intact cells with Wortmannin results in an irreversible decrease in anti-Ig-induced PI3K activity, suggesting that the effect of Wortmannin on anti-Ig-mediated growth inhibition is caused by its inactivation of PI3K activity. Taken together, these data show that activation of PI3K is a critical component of the anti-Ig-initiated signaling cascade that leads to growth inhibition of human B lymphoma cells.
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PMID:Phosphatidylinositol-3-kinase activity is required for the anti-ig-mediated growth inhibition of a human B-lymphoma cell line. 854 43


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