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)

A combination of metabolic labeling and chemical or enzymatic modification was employed to isolate and biochemically characterize a set of glycosyl-phosphatidylinositol (gly-PI) molecules synthesized by T lymphocytes. Gly-PI displayed unique patterns of synthesis following mitogen activation relative to the phosphoinositides and major structural lipids. The increase with time in gly-PI was paralleled by the appearance of insulin receptors. Gly-PI molecules were sensitive to hydrolysis by a PI-specific phospholipase C and were rapidly (15 sec) degraded in response to insulin binding. The product of this hydrolysis is believed to be a novel inositol phosphate-glycan (IP-gly) that was shown to inhibit the activity of a cAMP-dependent protein kinase. These results demonstrate that T cells contain a structurally related set of gly-PI molecules, at least one of which is sensitive to insulin and may function as a second messenger of hormone action.
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PMID:Regulation and function of an insulin-sensitive glycosyl-phosphatidylinositol during T lymphocyte activation. 283 76

Incubation of mouse epidermal HEL-37 cells with C. perfringens phospholipase C for 30 min caused a partial loss of protein kinase C activity after 30 min incubation. Essentially all the kinase activity was present in the cytosolic fraction of both control and treated cells, despite the continued hydrolysis of phospholipid by the exogenous phospholipase. At shorter incubation times with phospholipase C (5 and 10 min) an association of protein kinase with particulate material was observed, presumably reflecting the accumulation of diacylglycerol. It is proposed that further incubation with phospholipase C renders the plasma membrane unable to bind protein kinase C and that already bound enzyme is destroyed by proteolysis.
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PMID:Effect of membrane perturbation on protein kinase C activation: treatment with exogenous phospholipase C decreases translocation of enzyme to cellular membranes. 287 87

We examined the possible importance of protein kinase c-dependent mechanisms in mediating the stimulatory effects of gastrin and cholecystokinin (CCK) on the release of somatostatin-like immunoreactivity (SLI) from isolated canine fundic D-cells. Diacylglycerides, presumably the products of phosphoinositide breakdown that activate protein kinase c, and phospholipase C, which catalyzes the production of endogenous diacylglycerides from membrane phospholipids, both stimulated SLI secretion in a dose-dependent fashion. Both classes of agents potentiated the actions of adenosine 3',5'-cyclic monophosphate-dependent agonists but not those of gastrin and CCK. The stimulatory effects of gastrin and CCK correlated with their abilities to enhance the incorporation of 32P into membrane phosphatidyl inositol and phosphatidic acid and promote the release of [3H]inositol trisphosphate from prelabeled D-cells, two parameters of phosphoinositide turnover. These data suggest that protein kinase c may serve to transduce the signals activated by gastrin and CCK in D-cells.
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PMID:Potential mediation of somatostatin secretion from canine fundic D-cells by protein kinase c. 288 55

While protein kinase C (PKC) appears to play a role in the action of PTH in renal cells, direct evidence of activation by PTH is lacking. Rat PTH (1-34) caused a rapid, transient translocation of PKC in opossum kidney (OK) cells from a basal value of 0.09 to maximum of 0.24 at 10-15 sec. Both the time course and dose-response relationship of translocation matched a corresponding increase in cytosolic Ca2+. In contrast, PTH activation of cAMP-dependent protein kinase (PKA), while also rapid, was greater in magnitude (0.10 to 0.50), persistent, and occurred at a threshold level of 3 x 10(-10)M PTH, compared to 10(-8)M for PKC. Neither bPTH(3-34) nor bPTH(7-34) activated either protein kinase, while both antagonized rPTH(1-34)-induced PKC translocation more effectively than PKA activation. These differential effects of PTH agonist and antagonists further support the suggestion that PTH acts through two signal transduction mechanisms in which one or more receptors is linked in distinct ways to adenylate cyclase and phospholipase C.
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PMID:Parathyroid hormone 1-34, but not 3-34 or 7-34, transiently translocates protein kinase C in cultured renal (OK) cells. 293 May 65

Various regulators of protein kinase activities were tested for their effects on the in vitro transfer of phosphate from [gamma-32P]ATP to four proteins of rat brain synaptic particulate preparations. One protein, of apparent molecular weight 44,000, accepted 32P in the presence of 8 mM EDTA and no added Mg2+. It was the major phosphoprotein of brain mitochondria. Its phosphorylation was inhibited by pyruvate and stimulated by K+, and it comigrated in electrophoretic gels with authentic alpha-subunit of pyruvate: lipoamide oxidoreductase (decarboxylating) (EC 1.2.4.1) from bovine heart. The major kinase acting on three proteins of apparent molecular weights 24,000, 21,000, and 19,000 was stimulated by Ca2+, by preincubation with phospholipase C, and by 12-tetradecanoyl 4-beta-phorbol 13-acetate. Phosphorylation of these lower-molecular-weight proteins was inhibited by ACTH1-24, by cyclic 3',5'-adenosine monophosphate, and by 50 microM trifluoperazine. The stimulatory effect of Ca2+ was antagonized by calmodulin. The kinase in question appears to be B-50 protein kinase or protein kinase C.
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PMID:Regulation of phosphate incorporation into four brain phosphoproteins that are affected by experience. 298 Dec 89

When the phorbol ester, 4 beta-phorbol-12-myristate-13-acetate (PMA) or bacterial phospholipase C (PL-C) is added to a preparation of purified adult rat Leydig cells, containing 2 mM CaCl2, a time- and dose-dependent decreases of LH-stimulated testosterone production is observed. After a 3 h stimulation with oLH (100 ng/ml), PMA (100 ng/ml) and PL-C (1.6 U/ml) do not affect the cell viability or the hCG specific binding, while cAMP accumulation is significantly reduced; cAMP-stimulated steroidogenesis is diminished only in the presence of PL-C. These observations suggest that in vitro: (i) activated Ca2+- and phospholipid-dependent protein kinase is implicated in the regulation of rat Leydig cell steroidogenesis by LH at a step before the adenylate cyclase; (ii) phospholipids play an important role in cAMP-stimulated testosterone synthesis.
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PMID:Effect of phorbol ester and phospholipase C on LH-stimulated steroidogenesis in purified rat Leydig cells. 299 25

Agonistic analogs of gonadotropin releasing hormone can induce oocyte maturation in rat follicle-enclosed oocytes (1-5). Cyclic AMP does not rise following exposure of the ovarian follicle to GnRH (3) suggesting that cAMP-dependent protein kinase is not involved in the mechanism of GnRH action in this system. Protein kinase C, which is independent of cAMP, has recently been reported to mediate GnRH action in the pituitary (6-8). The possible involvement of this enzyme in the regulation of oocyte maturation has been tested in the present study. We report here that phospholipase C and direct activators of protein kinase C can mimic the response of rat oocytes to GnRH. These results suggest that GnRH-induced meiotic maturation of rat oocytes is mediated by the phospholipid-dependent protein kinase, protein kinase C.
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PMID:Activators of protein kinase C stimulate meiotic maturation of rat oocytes. 299 74

Gonadotropin-stimulated steroidogenesis in the differentiating ovarian granulosa cell is mediated through the activation of cAMP-dependent protein kinase, and is also modulated by calcium-dependent mechanisms. Granulosa cells contain calcium-activated, phospholipid-dependent protein kinase (C kinase), and show an increase in phosphatidylinositol turnover in response to GnRH agonist analogs. To evaluate the role of C kinase in ovarian steroidogenesis, the potent phorbol ester, TPA, and the permeant diacylglycerol, OAG, were used to activate C kinase in granulosa cells from PMSG-treated immature rats. Both TPA and OAG caused dose-dependent stimulation of progesterone production without affecting intra- or extracellular cAMP levels. However, the maximum steroid responses to these compounds were less than those stimulated by cAMP. The ED50 for TPA-stimulated progesterone production was 3 nM, which is close to the known Km for activation of C kinase. Stimulation of steroidogenesis was only observed with biologically-active phorbol esters and permeant diacylglycerols such as OAG and DOG. Exposure of granulosa cells to phospholipase C also increased progesterone production in a dose-dependent manner without changing the cAMP content. Although TPA and OAG did not increase basal cAMP production, both agents enhanced the cAMP responses stimulated by hCG and forskolin; likewise, phospholipase C alone did not change cAMP production but caused a dose-dependent increase in the cAMP responses to hCG and forskolin. These results demonstrate that activation of C kinase promotes steroidogenesis in ovarian granulosa cells, and potentiates the activation of adenylate cyclase by hCG and forskolin. Such findings support the possibility that the calcium, phospholipid-dependent enzyme could be involved in the regulation of progesterone production by hormonal ligands such as gonadotropins and GnRH.
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PMID:Activation of protein kinase C potentiates cyclic AMP production and stimulates steroidogenesis in differentiated ovarian granulosa cells. 300 71

Endogenous lipid droplets were prepared by subjecting fat cells to hypotonic shock and Triton X-100 treatment. The endogenous lipid droplets were found to show lipolysis in response to epinephrine, but not to show lipogenesis from glucose in response to insulin. These results indicated that the preparation of endogenous lipid droplets did not contain any intact fat cells capable of insulin-stimulated lipogenesis. Results with these endogenous lipid droplets showed that protein kinase inhibitor inhibited protein kinase-mediated hormone-sensitive lipase activity but did not reduce epinephrine-induced lipolysis. Cyclic AMP and dibutyryl cyclic AMP induced lipolytic activity in the presence of 80 mM KCl and their activities were not inhibited by protein kinase inhibitor. Phospholipase C inhibited epinephrine, cyclic AMP and dibutyryl cyclic AMP-induced lipolysis, but did not affect the lipolytic activity of either the activated or non-activated form of hormone-sensitive lipase. These results indicate the existence of a protein kinase inhibitor-insensitive and phospholipase C-sensitive lipolytic pathway in rat adipocytes.
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PMID:Studies on a protein kinase inhibitor-insensitive, phospholipase C-sensitive pathway of lipolysis in rat adipocytes. 302 21

The biochemical events initiated by mitogen in T lymphocytes are the subject of this paper. Following interaction of the mitogen with its receptors, a transmembrane 'trigger-type' signal is propagated which has both positive and negative correlates. The negative signal occurs with high mitogen concentrations and is associated with membrane freezing, microtubular aggregation, receptor capping, adenylate cyclase activation, and cellular cyclic AMP increases. The positive signal occurs with optimal mitogen concentrations and is associated with changes in membrane permeability and transport with influx of calcium and potassium ion and efflux of sodium, in transport processes for glucose, amino acids, and nucleosides, and in a collected series of early membrane lipid changes which can be considered essential for the positive signal. These lipid changes include the uptake of arachidonic acid and other fatty acids, choline, phosphate and other molecules, their incorporation into membrane phospholipids, particularly phosphatidylinositol (PI), and a turnover of PI with the production of inositol triphosphate, which can be related to calcium mobilization and diacylglycerol which activates a cytoplasmic protein kinase C. A key event associated with mitogen action is arachidonic acid release. Arachidonic acid may give rise to prostaglandins and thromboxanes as part of negative components of the signal through effects on the adenylate cyclase/cyclic AMP system. Arachidonic acid gives rise to eicosanoids like 5-, 11-, possibly 12- and 15-hydroxyperoxy and hydroxy eicosatetraenoic acids and leukotrienes B4 and C4. The activation of the 5-lipoxygenase, a critical calcium-dependent step, leads via the production of 5-HPETE and 5-HETE to the activation of membrane and soluble guanylate cyclase and the production of cyclic GMP. Cyclic GMP appears to be essential for mitogen activation and is associated with cyclic GMP-dependent protein kinase activation and the phosphorylation of a number of substrates. Calcium ion influx is clearly central to mitogen action. Calcium through its influx and mobilization from cellular stores is thought to contribute directly and indirectly through the action of calmodulin and protein kinase C to the activation of a number of enzymatic processes involved in the positive signal including phospholipase C, diglyceride kinase and lipase, 5-lipoxygenase, and guanylate cyclase. Cyclic GMP and calcium ion both participate in nuclear processes leading to RNA and protein synthesis. Interleukin 2 is associated with midcycle increases in cyclic GMP and entry into DNA synthesis.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Transduction of signals in the activation of T lymphocytes: relation to leukemia. 304 Mar 20


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