Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Primary cultures of luteal cells have been used to determine both acute and chronic effects of cytokines on luteal cell function and viability. Gonadotrophin-stimulated progesterone production is inhibited by interleukin 1 beta (IL-1 beta), tumour necrosis factor alpha (TNF-alpha), or gamma-interferon (IFN-gamma), the last two cytokine being more effective than IL-1. In contrast, all three cytokines are potent stimulators of prostaglandin production by these cells. The mechanism by which prostaglandin synthesis is enhanced may differ slightly for each cytokine. In luteal cells, TNF-alpha appears to act primarily through stimulation of phospholipase A2, whereas IL-1 beta may activate phospholipase C and prostaglandin endoperoxide synthase (PGS) in addition to phospholipase A2. The mechanism of action of IFN-gamma has not yet been determined. In addition to the observed functional effects, cytokines may also promote cell death during luteal regression. Although the three cytokines mentioned have little or no effect on viability of cultured luteal cells when administered separately, combined treatment with TNF-alpha and IFN-gamma results in a substantial decrease in the number of viable cells. Inhibition of cytokine-stimulated prostaglandin production does not alter the cytotoxic effect of these cytokines. Expression of major histocompatibility (MHC) class I molecules on luteal cells is enhanced, and MHC class II molecules are induced, by exposure to IFN-gamma. This is especially intriguing, as MHC class II expression increases before luteal regression in vivo, and is suppressed in early pregnancy. In summary, evidence is rapidly accumulating that supports the hypothesis that the function or structural integrity of luteal cells may be modulated by resident immune cells. Future research will probably address how these local events are hormonally controlled, and if they can be modified to regulate corpus luteum function.
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PMID:Involvement of immune cells in regulation of ovarian function. 762 27

Endothelin (ET) produced by endothelial cells has recently been found to be a potent vasoconstricting hormone. In this report, ET is shown to be a potent stimulator of interleukin-6 (IL-6) production by rat bone marrow (BM)-derived stromal cells. It was also shown that ET increased the level of mRNA for IL-6 in these cells. The two types of ET receptor (R), ETAR and ETBR, were shown to be expressed on both BM-derived stromal cells in culture and ex vivo in BM tissue, suggesting that ET works as a physiologic stimulator of IL-6 production in the BM. It was shown that ETAR is coupled to phospholipase C activation, leading to the production of inositol 1,4,5-trisphosphate (IP3) and 1,2-diacylglycerol (DAG) as second messengers in BM-derived stromal cells. This was corroborated by data showing that IL-6 production in these cells was induced by combined stimulation with ionomycin and phorbol myristate acetate, thereby bypassing the effects of IP3 and DAG, respectively. This is the first report on the hormonal regulation of IL-6 production by BM stromal cells, indicating that hematopoiesis is subject to endocrinologic regulation under physiologic conditions. ET has recently been reported to be produced by macrophages in response to bacterial lipopolysaccharide and human immunodeficiency virus-1 glycoprotein 120. These facts, taken together with our findings, raise the possibility that ET shares the same role of IL-1 as a local cytokine, mediating an intercellular signal between macrophages and BM stromal cells in response to bacterial or viral stimulation.
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PMID:Stimulation of interleukin-6 production by endothelin in rat bone marrow-derived stromal cells. 791 71

The release of arachidonic acid in A549 cells was stimulated in a time- and dose-dependent manner by the Ca2+ ionophore ionomycin (t1/2 = 4 min), thapsigargin (t1/2 = 8 min), bradykinin (t1/2 = 12 min, EC50 = 3 nM), and interleukin 1 alpha (t1/2 = 28 min, EC50 = 0.3 ng/ml). Bradykinin (10 nM) and interleukin 1 alpha (1 ng/ml) stimulation was blocked by the bradykinin B2 receptor antagonist, D-Arg,[Hyp3,Thi5,8, D-Phe7]bradykinin and interleukin 1 receptor antagonist (IC50 = 30 mM and 20 ng/ml, respectively), suggesting receptor mediation. Diacylglycerol release was < 10% of total arachidonic acid release in all cases, suggesting activation of phospholipase A2 activity was greater than phospholipase C activation by these agents. The effects of ionomycin (3 microM) and thapsigargin (0.3 microM) were abolished in Ca(2+)-free buffer with and without 0.5 mM EGTA. Bradykinin (10 nM) stimulation was reduced by 50% in Ca(2+)-free buffer whereas interleukin 1 alpha (1 ng/ml) stimulation remained unaffected. However, the presence of EGTA completely abolished bradykinin stimulation and partially blocked the effect of interleukin 1 alpha (43% inhibition). In the presence of extracellular Ca2+, ionomycin (3 mM), thapsigargin (0.3 mM), bradykinin (10 nM), and interleukin 1 alpha (1 ng/ml) stimulation of arachidonic acid release was blocked by the Ca2+ influx blocker LaCl3 (29, 44, 35, and 41% inhibition, respectively). Nifedipine also blocked ionomycin and thapsigargin stimulation but only partially blocked bradykinin and interleukin 1 alpha stimulation. These results suggest that following B2 receptor activation, cytosolic phospholipase A2 is stimulated by a rise in intracellular Ca2+ levels which are sensitive to the action of EGTA, whereas interleukin 1 alpha stimulation of cytosolic phospholipase A2 is mediated by a rise in intracellular Ca2+ from both EGTA-sensitive and resistant pools. Furthermore the results of ionomycin and thapsigargin indicate that extracellular Ca2+ is important for activation of cytosolic phospholipase A2 in A549 cells.
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PMID:Differential role of extra- and intracellular calcium in bradykinin and interleukin 1 alpha stimulation of arachidonic acid release from A549 cells. 813 Feb 63

Parotin subunit (PS) is a unique glycoprotein, isolated from bovine parotid glands, which possesses the ability to induce polyclonal antibody production and IL-1-like activity. The present studies investigated the existence of receptors for PS on B cell surfaces using PS-affinity chromatography. No PS-binding proteins (PSR) solubilized from human B cell surfaces with Triton X-100 were detected, whereas the PSR released from human B cell membranes with phosphatidylinositol-specific phospholipase C (PI-PLC) treatment were composed of 75- and 40-kDa proteins. PI-PLC treatment markedly reduced polyclonal antibody responses to PS but weakly inhibited the responses to PWM, xanthan gum, and LPS in human and mouse lymphocytes. Addition of PSR caused a dose-related reduction in polyclonal IgM and IgG antibody responses to PS. These results suggest that PSR can act as glycosylphosphatidylinositol-anchored receptors for PS.
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PMID:Parotin subunit as a potent polyclonal B cell activator binds to newly found glycosylphosphatidylinositol (GPI)-anchored proteins on human B cell surfaces. 813 Dec 11

The proinflammatory cytokine IL-1 was shown to increase the responsiveness of synovial cells to the potent inflammatory peptide bradykinin (BK). We have investigated the biochemical events linked to this amplifying action of IL-1. Stimulation of synoviocytes with only BK elicited a rapid increase in inositol phosphates and a concomitant accumulation of diacylglycerol (DAG), monoacylglycerol, and free arachidonic acid (AA). In contrast, IL-1 did not stimulate any of these events. Thus, BK can induce AA release via the hydrolysis of phosphatidylinositols by a phospholipase C (PLC). BK also activated a phospholipase D (PLD) to cleave phosphatidylcholine (PC), because it caused an increase in phosphatidic acid (PA) content and a sustained DAG formation, which both were inhibited by ethanol in [3H]myristic acid-labeled cells. Moreover, the addition of ethanol diverted PLD into the formation of phosphatidylethanol (PEt) thus inhibiting the amounts of PA and DAG formed. Priming of synovial cells with rIL-1 beta 24 h before exposure to BK in the presence of ethanol further enhanced the BK-induced formation of PEt. Conversely, preincubation with IL-1 did not influence the BK-induced PLC activation nor did it alter the liberation of AA. Finally, we demonstrated that the IL-1-mediated amplification of PGE2 release in response to BK was reduced by the presence of ethanol in the culture medium, suggesting that part of the synergistic action of IL-1 and BK on prostanoid production was dependent on the activation of the PC-specific PLD pathway.
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PMID:IL-1 beta amplifies bradykinin-induced prostaglandin E2 production via a phospholipase D-linked mechanism. 817 21

Various first messengers linked to phospholipase C, including acetylcholine and interleukin 1, regulate the production both of the secreted form of the amyloid protein precursor (APP) and of amyloid beta-protein. We have now identified intracellular signals which are responsible for mediating these effects. We show that activation of phospholipase C may affect APP processing by either of two pathways, one involving an increase in protein kinase C and the other an increase in cytoplasmic calcium levels. The effects of calcium on APP processing appear to be independent of protein kinase C activation. The observed effects of calcium on APP processing may be of therapeutic utility.
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PMID:Calcium regulates processing of the Alzheimer amyloid protein precursor in a protein kinase C-independent manner. 818 35

Phospholipase C-mediated release of inositol trisphosphate, followed by an increase in free intracellular calcium, is an important signal transduction pathway for several membrane receptors. In the present investigation, the coupling of various receptors to phospholipase C was studied in the human keratinocyte line HaCaT. Inositol trisphosphate formation was determined by anion-exchange chromatography, and the release of intracellular calcium was analysed with the fluorescence probe Fura-2 AM. Activation of HaCaT keratinocytes with bradykinin resulted in a time- and dose-dependent release of inositol trisphosphate and intracellular calcium, with an EC50 value of 50 nM for bradykinin-induced inositol trisphosphate formation. The mediators and cytokines IL-1, IL-4, IL-6, IL-8, EGF and TGF alpha, as well as bombesin, prolactin, carbachol, substance P and retinoic acid, did not activate this pathway. The inability of the mediators examined to activate phospholipase C may be due to lack of the respective cognate receptors or to the use of other signal transduction pathways.
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PMID:Inositol phosphate formation and release of intracellular free calcium by bradykinin in HaCaT keratinocytes. 830 79

We have tested whether breakdown of phosphatidylcholine (PC) initiated by exogenous addition of a PC-specific phospholipase C (PC-PLC) from Bacillus cereus or by endogenous overexpression of PC-PLC induces functional activation of NF-kappa B and increases human immunodeficiency virus (HIV) enhancer activity. PC-PLC-activated hydrolysis of PC was found to induce bona fide p50/p65 NF-kappa B binding activity in three different cell lines of human or murine origin. No significant changes in the turnover of other cellular phospholipids were detected in PC-PLC-treated cells. Induction of NF-kappa B by PC-PLC did not depend on de novo synthesis of proteins or autocrine secretion of either tumor necrosis factor or interleukin 1. In human monocytic and lymphoblastoid T-cell lines, induction of NF-kappa B by PC-PLC resulted in clear induction of luciferase expression vectors placed under the control of synthetic kappa B enhancers or wild type, but not kappa B-mutated, HIV long terminal repeat constructs. HIV replication was increased by PC-PLC in chronically infected monocytes and T lymphocytes. NF-kappa B activation promoted by addition of exogenous PC-PLC correlated with an intense production of diacylglycerol. However, addition of a phosphatidylinositol-specific PLC from B. cereus also induced diacylglycerol but did not activate kappa B enhancer-directed vectors. PC-PLC-induced NF-kappa B activation could not be blocked by a specific inhibitor of phorbol ester-inducible protein kinases C. These results indicate that a cellular transduction pathway, dependent on specific PC breakdown, is functional in T lymphocytes and monocytes and may be used by various transmembrane receptors to activate HIV transcription through NF-kappa B-dependent induction of the HIV enhancer.
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PMID:Phosphatidylcholine hydrolysis activates NF-kappa B and increases human immunodeficiency virus replication in human monocytes and T lymphocytes. 841 62

A short synthetic peptide (Pa) containing a structural motif ("2-6-11" motif) present in a number of human extracellular matrix proteins was found to stimulate the production of cytokines IL-1alpha, IL-1beta, IL-6, and TNFalpha by human peripheral blood mononuclear cells. We have now investigated the signal transduction pathway involved in the elicitation of these immunomodulating properties on isolated human monocytes. Our results show that active peptide Pa provoked phosphoinositide hydrolysis, intracellular calcium elevation, and cAMP accumulation. Herbimycin A, an inhibitor of protein tyrosine kinases (PTK), markedly reduced these effects of peptide Pa. We have also found that this peptide stimulated CREB, NF-kappaB, and AP-1 DNA-binding activity. With the help of inhibitors of PTK (herbimycin A), phospholipase C (neomycin sulfate), protein kinase C (bis-indolyl maleimide), protein kinase A (H89), and the calmodulin antagonist W-7, as well as cholera toxin, an agent that increases intracellular cAMP, we showed that cytokine (IL-1alpha, IL-1-beta, IL-6, and TNFalpha) production could be modified by the signal transduction pathway triggered by peptide Pa on monocytes.
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PMID:Signaling pathway triggered by a short immunomodulating peptide on human monocytes. 902 64

CD5 is a 67-kDa surface glycoprotein found in association with the Ag receptor complex on both T and B lymphocytes. CD5 modulates Ag receptor-mediated immune responses, but the molecular mechanisms of its action remain unclear. In this respect, the assessment of the relative and unique contribution of CD5 in cell signaling events is a crucial point. We have used Jurkat variants and anti-CD5 mAbs to show that the CD5 signaling pathway is distinct from that used by the TCR/CD3 complex. We hereby identify two independent mechanisms of CD5-mediated diacylglycerol release by virtue of their different kinetics: 1) an early and transient diacylglycerol increase that results from the activation of a phosphatidylcholine-specific phospholipase C, and 2) a late and sustained increase that requires de novo phospholipid synthesis. Studies performed on a TCR/CD3-deficient Jurkat cell variant indicate that only the CD5-mediated phosphatidylcholine-specific phospholipase C activation is dependent on TCR/CD3 expression. Mutational analyses of CD5 demonstrate that both mechanisms are dependent on the integrity of the CD5 distal cytoplasmic region. Our results show that CD5 is a signaling molecule per se that uses mechanisms resembling those used by some cytokine receptors (such as IL-1 or TNF receptors) to modulate lymphocyte activation.
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PMID:The cytoplasmic domain of CD5 mediates both TCR/CD3-dependent and -independent diacylglycerol production. 937 26


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