Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To clarify the role of the breakdown of phosphatidylinositol 4,5-bisphosphate (PIP2) in GH secretion in human somatotrophs and the effects of inhibitors of GH secretion on this mechanism, we studied the effects of 12-tetradecanoylphorbol-13-acetate (TPA) and phospholipase C (Plase C) on GH secretion and the interactions of somatostatin (SRIH), bromocriptine, and pertussis toxin (IAP) with TPA or Plase C, using human GH-secreting pituitary adenoma cells in culture. SRIH (10(-9)-10(-7) M) inhibited and TPA (10(-10)-10(-8) M) and Plase C (0.125-1.0 U/mL) stimulated GH secretion. SRIH (10(-9)-10(-7) M) inhibited GH release induced by TPA (10(-8) M) or Plase C (1.0 U/mL). Bromocriptine (10(-8) M) also inhibited 10(-8) M TPA-induced GH secretion. When adenoma cells were treated with 100 ng/mL IAP for 24 h, basal and TPA-induced GH secretion rates did not change. However, the inhibitory effects of SRIH (10(-8) M) or bromocriptine (10(-8) M) on basal and 10(-8) M TPA-stimulated GH secretion were attenuated. In addition, IAP reduced GH secretion induced by 0.5 U/mL Plase C, while SRIH inhibition of Plase C-evoked GH release was diminished by IAP. We conclude that the hydrolysis of PIP2 by Plase C, which causes activation of protein kinase C by 1,2-diacylglycerol and Ca2+ mobilization by inositol 1,4,5-triphosphate, is a physiological intracellular mechanism leading to GH secretion in human somatotrophs; SRIH inhibits GH secretion mediated by this mechanism, and bromocriptine blocks at least protein kinase C-mediated GH release; the inhibitory guanine nucleotide-binding protein (Ni) is involved in these inhibitory effects of SRIH and bromocriptine; and Ni modulates the breakdown of PIP2 by Plase C.
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PMID:Phorbol ester and phospholipase C-induced growth hormone secretion from pituitary somatotroph adenoma cells in culture: effects of somatostatin, bromocriptine, and pertussis toxin. 288 Aug 63

Insulin/dexamethasone/methylisobutylxanthine (hormones/IBMX) induce 3T3-L1 fibroblasts to differentiate into adipocytes. Our previous study suggested that pertussis toxin (IAP)-sensitive GTP-binding protein(s) (G-protein) is involved in the process of differentiation by hormones/IBMX, accompanied by c-fos induction. Northern blotting indicated that among the IAP-sensitive G-proteins, the levels of Gi2 alpha, Go alpha, and Gi3 alpha mRNA were decreased, increased and unchanged, respectively. Gi1 alpha was undetectable and IAP attenuated the decrease in Gi2 alpha mRNA level but did not affect the change in Go alpha mRNA level during the adipocyte differentiation. These results indicate that IAP-sensitive Gi2 alpha mRNA level is decreased during adipocyte differentiation. A combination of phosphatidylinositol-specific phospholipase C (PI-PLC) and IBMX induced c-fos expression in 3T3-L1 fibroblasts similar to that induced with hormones/IBMX. c-fos induced by both stimulators was also diminished by anti-inositolglycan antibody or anti-PI-PLC antiserum. Insulin stimulated the release of inositolproteoglycan and diacylglycerol from 3T3-L1 fibroblasts, which was suppressed by IAP treatment. These findings suggested that one of the pathways of adipocyte differentiation induced by hormones/IBMX occurs via the inositolglycan-specific PI-PLC cascade coupled to IAP-sensitive G-protein(s). Both activation of glycerophosphate dehydrogenase and stimulation of insulin-dependent 2-deoxyglucose uptake induced by hormones/IBMX were enhanced in protein kinase C-depleted cells exposed to phorbol 12-myristate 13-acetate (PMA), and attenuated in IAP-treated cells. The level of a 32P-labeled 52 kDa protein in plasma membrane fractions immunoprecipitated by anti-PI-PLC antiserum was increased by PMA stimulation, abolished in PMA-treated cells, and increased in IAP-treated cells. These findings suggest that protein kinase C phosphorylates PI-PLC, resulting in a decrease in PI-PLC activity related to the signal transduction pathway of adipocyte differentiation of 3T3-L1 fibroblasts.
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PMID:Possible involvement of phosphatidylinositol-specific phospholipase C related to pertussis toxin-sensitive GTP-binding proteins during adipocyte differentiation of 3T3-L1 fibroblasts: negative regulation of protein kinase C. 798 Dec 46

The [(3)H]inositol incorporation into the membrane fraction of A-431 human epidermoid carcinoma cells was markedly increased by stimulation of the cells with either epidermal growth factor (EGF), ATP, bradykinin, or a calcium ionophore A23187 in the presence of 1 mM extracellular calcium ions; most incorporated [(3)H]inositol was found to have accumulated as phosphatidylinositol (PI). The EGF- and ATP-stimulated PI synthesis was inhibited by two protein kinase C inhibitors, staurosporine and 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), and an intracellular calcium chelator, 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA/AM), but not by the calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7). Pretreatment of cells with pertussis toxin (IAP, islet-activating protein) inhibited the PI synthesis, [Ca(2+)]i elevation, and inositol trisphosphate (IP(3)) production by ATP, suggesting that the phospholipase C(PLC) system coupled with IAP-sensitive G protein is involved in the ATP-stimulated PI synthesis. On the other hand, the ATP stimulation increased the release of [(3)H]choline and [(32)P)phosphatidic acid (PA) from radiolabeled cells, and such release was not inhibited by IAP. In the presence of n-butyl alcohol, which prevents the production of PA by generation of phosphatidylbutanol, the ATP-stimulated PI synthesis was reduced. Because n-butyl alcohol did not inhibit IP(3) production and [Ca(2+)]i elevation, this fact suggests that the lAP-insensitive PLD system is involved in the ATP-stimulated PI synthesis. In A-431 cells, the stimulation of P(2)-purinergic receptors appears to activate the IAP-sensitive PLC system and IAP-insensitive PLD system, both of which are essential for the stimulation of PI synthesis. The present results imply the general prospect that ligand stimulation, which mobilizes second messengers and consumes their precursors, simultaneously provokes the pathway to synthesize and salvage the second messenger precursors as well.
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PMID:ATP- and EGF-stimulated phosphatidulinositol synthesis by two different pathways, phospholipase D and diacylglycerol kinase, in A-431 epidermoid carcinoma cells. 921 28

The effects of 5-HT and NA on glycine-gated Cl- channel currents(IGly) and its intracellular mechanisms were investigated in acutely dissociated rat sacral dorsal commissural neurons by using nystatin perforated patch clamp recording. It was found that: (1) the activation of 5-HT2 receptor coupled to IAP-insensitive G-proteins increases intracellular DAG formation through the activation of phospholipase C(PLC). The accumulation of DAG increases the Ca(2+)-independent or novel PKC(nPKC) activity, resulting in the potentiation of IGly; (2) the activation of alpha 2-adrenoceptor by NA coupled to IAP-sensitive G-proteins reduces intracellular cAMP formation through the inhibition of adenylyl cyclase (AC). The reduction of cAMP decreases PKA activity, resulting in the potentiation of IGly.
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PMID:[Enhancement of glycine-gated Cl- channel currents by 5-HT and NA in rat sacral dorsal commissural neurons is mediated by protein kinases]. 1103 31

The protein kinase C (PKC)-specific inhibitor, Ro-31-8220, has been shown to induce anti-proliferation and apoptosis of human cancer cell lines. In the present study, we determined the molecular pathways that lead to apoptosis after treatment of cells with the PKC-specific inhibitor RO-31-8220. For this, we used the U937 human leukemia cell line and a phorbolmyristate acetate (PMA)-resistant derivative cell line, R-U937. Ro-31-8220 treatment of U937 cells leads to apoptosis, which is accompanied by activation of caspase 3 (as measured by decreased levels of the 32kDa inactive form and increased proteolytic cleavage of phospholipase C (PLC)-gamma1). The broad-range caspase inhibitor z-VAD-fmk inhibits this induction of apoptosis, supporting a direct link between caspase activation and Ro-31-8220 induction of apoptosis. This activation of apoptosis is also accompanied by release of cytochrome c, but not by altered expression of Bcl-2 family protein or IAP family proteins. In R-U937 cells, Ro-31-8220 fails to cause release of cytochrome c, activation of caspase 3, or apoptosis. Activation of Akt occurs to a greater extent in the R-U937 cells than the U937 cells and thus might be related to protection from Ro-31-8220-induced apoptosis.
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PMID:Failure to activate caspase 3 in phorbol ester-resistant leukemia cells is associated with resistance to apoptotic cell death. 1204 64

Se-methylselenocysteine (Se-MSC) is a potent chemopreventive agent in many test systems and has been shown to inhibit tumor promotion and induce apoptosis, but its mechanism of action is still not well understood. The present study was designed to assess the mechanism of Se-MSC on the induction of apoptosis in SKOV-3 ovarian cancer cells. Se-MSC displayed strong inhibitory effects on cell proliferation and viability of SKOV-3 cells in dose and time dependent manners and induced apoptosis. Investigation of the mechanism of Se-MSC-induced apoptosis revealed that treatment with Se-MSC produced morphological features of apoptosis and DNA fragmentation. This was associated with caspase-3 activation and cleavage of poly(ADP-ribose) polymerase and phospholipase C-gamma1 proteins. However, SKOV-3 cells treated with Se-MSC did not demonstrate cytochrome c accumulation in the cytosol during apoptosis induction. Pretreatment of cells with the caspase inhibitors (z-VAD-fmk and DEVD-CHO) prevented Se-MSC-induced apoptosis. These results suggested that Se-MSC induces apoptosis through cytochrome c-independent caspase-3 activation in SKOV-3 cells. In late stage of apoptosis, p18kDa fragment of Bax was generated with the down-regulation of the expressions of survivin, X-linked inhibitor of apoptosis protein, and human inhibitor of apoptosis protein 1 following Se-MSC treatment, suggesting that the modulation of Bax and IAP (inhibitors of apoptosis) family proteins play some role in Se-MSC-mediated apoptosis. Pre-treatments of z-VAD-fmk and the calpain inhibitor, calpeptin inhibited Bax cleavage. These results suggested that Bax cleavage is mediated by calpain, and calpain activation may be a caspase-dependent one. Taken together, the chemopreventive effects of Se-MSC may be related in part to the caspase-3 activation, the down-regulation of IAP family proteins, and Bax cleavage mediated by caspase-dependent calpain activation.
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PMID:Se-methylselenocysteine induces apoptosis through caspase activation and Bax cleavage mediated by calpain in SKOV-3 ovarian cancer cells. 1217 27

Curcumin, a natural, biologically active compound extracted from rhizomes of Curcuma species, has been shown to possess potent anti-inflammatory, anti-tumor and anti-oxidative properties. The mechanism by which curcumin initiates apoptosis remains poorly understood. In the present report we investigated the effect of curcumin on the activation of the apoptotic pathway in human renal Caki cells. Treatment of Caki cells with 50 microM curcumin resulted in the activation of caspase 3, cleavage of phospholipase C-gamma1 and DNA fragmentation. Curcumin-induced apoptosis is mediated through the activation of caspase, which is specifically inhibited by the caspase inhibitor, benzyloxycarbony-Val-Ala-Asp-fluoromethyl ketone. Curcumin causes dose-dependent apoptosis and DNA fragmentation of Caki cells, which is preceded by the sequential dephosphorylation of Akt, down-regulation of the anti-apoptotic Bcl-2, Bcl-XL and IAP proteins, release of cytochrome c and activation of caspase 3. Cyclosporin A, as well as caspase inhibitor, specifically inhibit curcumin-induced apoptosis in Caki cells. Pre-treatment with N-acetyl-cysteine, markedly prevented dephosphorylation of Akt, and cytochrome c release, and cell death, suggesting a role for reactive oxygen species in this process. The data indicate that curcumin can cause cell damage by inactivating the Akt-related cell survival pathway and release of cytochrome c, providing a new mechanism for curcumin-induced cytotoxicity.
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PMID:Molecular mechanisms of curcumin-induced cytotoxicity: induction of apoptosis through generation of reactive oxygen species, down-regulation of Bcl-XL and IAP, the release of cytochrome c and inhibition of Akt. 1280 27


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