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)

Intracellular Ca2+ signals of intact endothelium from rabbit aortic or pulmonic valves loaded with fura 2 were studied using imaging fluorescence microscopy. Agonists such as ATP or carbachol and inhibitors of endoplasmic reticulum (ER) Ca(2+)-ATPase such as cyclopiazonic acid (CPA), thapsigargin, and 2', 5'-di(tert-butyl)-1, 4,-benzohydroquinone (BHQ) induced an increase in cytoplasmic free Ca2+ concentration ([Ca2+]i) that was maintained above the prestimulated levels as long as extracellular Ca2+ was present, indicating that the maintained [Ca2+]i increase is dependent on the entry of extracellular Ca2+. The voltage-gated channel was not found to contribute to [Ca2+]i increase. SK&F-96365, a receptor-operated cation channel (ROC) blocker, and 2-nitro-4-carboxyphenyl-N, N-diphenylcarbamate (NCDC), a postulated phospholipase C inhibitor, were shown to effectively block ROC, since they greatly reduced the maintained [Ca2+]i increase caused by ATP, but not that caused by CPA, which was blocked by Ni2+. To further investigate the Ca2+ influx involved in this process, divalent cation entry was measured as Mn2+ quenching of fura 2 fluorescence at 360-nm excitation wavelength. At rest, fluorescence quenching at 360 nm by Mn2+ was observed, which was inhibited by Ni2+ but not by NCDC, indicating Mn2+ entry through the leak pathway. The quenching was enhanced following ATP stimulation, and this enhancement was abolished by pretreatment with NCDC. In contrast, the rate of Mn2+ quenching was unaffected by the application of CPA. These results demonstrate that ATP stimulates divalent cation influx that is not related to the Ca2+ content of ER. Abolition of Ca2+ uptake into ER was postulated to increase the effectiveness of the Ca2+ leak in raising [Ca2+]i.
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PMID:Agonist- and CPA-induced elevation of cytoplasmic free Ca2+ in intact valvular endothelium from rabbits. 878 Jan 77

The mechanism underlying the generation of cytosolic free Ca2+ ([Ca2+]i) oscillations by bombesin, a receptor agonist activating phospholipase C, in insulin secreting HIT-T15 cells was investigated. At 25 microM, 61% of cells displayed [Ca2+]i oscillations with variable patterns. The bombesin-induced [Ca2+]i oscillations could last more than 1 h and glucose was required for maintaining these [Ca2+]i fluctuations. Bombesin-evoked [Ca2+]i oscillations were dependent on extracellular Ca2+ entry and were attenuated by membrane hyperpolarization or by L-type Ca2+ channel blockers. These [Ca2+]i oscillations were apparently not associated with fluctuations in plasma membrane Ca2+ permeability as monitored by the Mn2+ quenching technique. 2,5-di-(tert-butyl)-1,4-benzohydroquinone (tBuBHQ) and 4-chloro-m-cresol, which interfere with intracellular Ca2+ stores, respectively, by inhibiting Ca(2+)-ATPase of endoplasmic reticulum and by affecting Ca(2+)-induced Ca2+ release, disrupted bombesin-induced [Ca2+]i oscillations. 4-chloro-m-cresol raised [Ca2+]i by mobilizing an intracellular Ca2+ pool, an effect not altered by ryanodine. Caffeine exerted complex actions on [Ca2+]i. It raised [Ca2+]i by promoting Ca2+ entry while inhibiting bombesin-elicited [Ca2+]i oscillations. Our results suggest that in bombesin-elicited [Ca2+]i oscillations in HIT-T15 cells: (i) the oscillations originate primarily from intracellular Ca2+ stores; and (ii) the Ca2+ influx required for maintaining the oscillations is in part membrane potential-sensitive and not coordinated with [Ca2+]i oscillations. The interplay between intracellular Ca2+ stores and voltage-sensitive and voltage-insensitive extracellular Ca2+ entry determines the [Ca2+]i oscillations evoked by bombesin.
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PMID:Oscillations of cytosolic free calcium in bombesin-stimulated HIT-T15 cells. 884 21

Mas-7, a mastoparan derivative, induces elevation of intracellular free Ca2+ concentration ([Ca2+]i) along two independent pathways. The minor contribution occurs via phospholipase C activation and is negatively regulated by treatment with phorbol 12-myristate 13-acetate, a protein kinase C activator. The major contribution involves plasma membrane pores allowing not only Ca2+, Mn2+, and Na+ to enter but also the uptake of ethidium bromide (314 Da) and lucifer yellow (457 Da), but not fura-2 (831 Da), Evans blue (961 Da), and fluorescein-conjugate phalloidin (1,175 Da). Mas-7-induced current, as measured in planar lipid bilayers, reveals that Mas-7-induced pores have two slope conductances, 290 and 94 pS, and that the pores are nonselective for cations. The results also indicate that Mas-7 can produce pores by direct interaction with the plasma membrane without the involvement of membrane proteins and cytosolic factors. Besides in human neuroblastoma cells, similar Mas-7 effects were also observed in other cell lines such as HL-60, 1321N1 human astrocytoma, and bovine chromaffin cells. The data suggest that the Mas-7-induced [Ca2+]i elevation is the combined result of Ca2+ release from stores via phosphoinositide turnover and prolonged Ca2+ influx through membrane pores.
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PMID:Induction of cytosolic Ca2+ elevation mediated by Mas-7 occurs through membrane pore formation. 895 10

Intercellular Ca2+ signalling in primary cultures of articular chondrocytes was investigated with digital fluorescence video imaging. Mechanical stimulation of a single cell induced a wave of increased Ca2+ that was communicated to surrounding cells. Intercellular Ca2+ spreading was inhibited by 18alpha-glycyrrhetinic acid, demonstrating the involvement of gap junctions in signal propagation. In the absence of extracellular Ca2+ mechanical stimulation failed to induce Ca2+ responses and communicated Ca2+ waves. Under these conditions Ca2+ microinjection induced intercellular waves involving the cells immediately surrounding the stimulated one. Mechanical stress induced Ca2+ influx in the stimulated, but not in the adjacent cells, as assessed by the Mn2+ quenching technique. Cell treatment with thapsigargin failed to block mechanically induced signal propagation, but significantly reduced the number of cells involved in the communicated Ca2+ wave. Similar results were obtained with the phospholipase C inhibitor U73122, which is known to prevent InsP3 generation. These results provide evidence that mechanical stimulation induces a cytosolic Ca2+ increase that may permeate gap junctions, thus acting as an intercellular messenger mediating cell-to-cell communication in articular chondrocytes.
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PMID:Propagation of intercellular Ca2+ waves in mechanically stimulated articular chondrocytes. 900 May 13

Prior treatment of NG108-15 cells with phosphatase inhibitors including okadaic acid and calyculin A inhibited the elevation of cytosolic Ca2+ concentration ([Ca2+]i) induced by bradykinin by approximately 63%. This inhibition was dependent on the concentration of okadaic acid with an IC50 of 0.15 nM. Okadaic acid treatment only lowered the maximal response of [Ca2+]i increase and had no effect on the EC50 value for bradykinin regardless of the presence of extracellular Ca2+. Neither the capacity of 45Ca2+ accumulation within intracellular nonmitochondrial Ca2+ stores nor the magnitude of [Ca2+]i increase induced by thapsigargin was reduced by the treatment of okadaic acid. In contrast, the same phosphatase inhibitor treatment inhibited the bradykinin-evoked inositol 1,4,5-trisphosphate (IP3) generation, the Mn2+ influx, and the capacity of mitochondrial Ca2+ accumulation. Furthermore, the sensitivity of IP3 in the Ca2+ release was suppressed by okadaic acid pretreatment. Our results suggest that the reduction of bradykinin-induced [Ca2+]i rise by the promotion of protein phosphorylation was attributed to the reduced activity of phospholipase C, the decreased sensitivity to IP3, and the slowed rate of Ca2+ influx. Thus, phosphorylation plays a role in bradykinin-sensitive Ca2+ signaling cascade in NG108-15 cells.
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PMID:Inhibition of bradykinin-induced calcium increase by phosphatase inhibitors in neuroblastoma x glioma hybrid NG108-15 cells. 900 77

A cDNA encoding a mouse B2 bradykinin (BK) receptor was stably transfected in Chinese hamster ovary (CHO) cells. In two resulting transformants, mouse B2 BK receptor was found to induce a twofold elevation in the inositol-1,4,5-trisphosphate level. In a pertussis toxin-insensitive manner, BK also produced a biphasic increase in the intracellular Ca2+ concentration ([Ca2+]i). The initial elevation in [Ca2+]i was abolished by thapsigargin pretreatment in Ca(2+)-free medium. The second phase was dependent on external Ca2+. The BK/inositol trisphosphate and thapsigargin-sensitive Ca2+ stores required extracellular Ca2+ for refilling. Ca2+ influx induced by BK and thapsigargin was confirmed by Mn2+ entry through Ca2+ influx pathways producing Mn2+ quenching. Genistein, a tyrosine kinase inhibitor, partially decreased the BK-induced [Ca2+]i increase during the sustained phase and the rate of Mn2+ entry. BK had essentially no effect on the intracellular cyclic AMP level. The results suggest that the mouse B2 BK receptor couples to phospholipase C in CHO cells and that its activation results in biphasic [Ca2+]i increases, by mobilization of intracellular Ca2+ and store-depletion-mediated Ca2+ influx, the latter of which is tyrosine phosphorylation dependent.
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PMID:Ca2+ release and Ca2+ influx in Chinese hamster ovary cells expressing the cloned mouse B2 bradykinin receptor: tyrosine kinase inhibitor-sensitive and- insensitive processes. 903 Feb 5

In rat neutrophils, formyl-Met-Leu-Phe (fMLP)-induced phosphate formation was inhibited by abruquinone A (IC50 value about 32.7 +/- 6.4 microM) as well as by a putative phospholipase C inhibitor, [6-[[17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole- 2,5-dione (U73122) (IC50 value about 11.3 +/- 1.2 microM). The reduction in inositol phosphate levels appeared to reflect inhibition of phospholipase C activity because the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) catalyzed by a soluble fraction from neutrophils was also inhibited by abruquinone A (IC50 value about 31.4 +/- 5.6 microM) over the same range of concentrations. Although abruquinone A alone induced Ca2+ and Mn2+ influx into neutrophils in Ca(2+)-containing medium, abruquinone A, like U73122, inhibited Ca2+ release (IC50 value about 23.5 +/- 0.5 microM) from internal stores in Ca(2+)-free medium. These results indicate that abruquinone A inhibits the activity of phosphoinositide-specific phospholipase C in neutrophils.
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PMID:Inhibition by abruquinone A of phosphoinositide-specific phospholipase C activation in rat neutrophils. 903 Sep 8

T-cell hybridomas metastasize widely, and the extent of dissemination correlates with invasiveness in fibroblast cultures. Previously, we provided evidence that both metastasis and in vitro invasion require activation of LFA-1, induced by G-protein-transduced signals triggered by as yet unidentified factors. We show here that LFA-1-mediated adhesion of TAM2D2 T-cell hybridoma cells to ICAM-1 can in fact be induced by direct activation of G-proteins using AIF-4, to the same extent as by using PMA or Mn2+. We assessed effects of protein kinase C (PKC), tyrosine kinase (TK), PI3-kinase (PI3K), and phospholipase C (PLC) inhibitors. Both AIF-4-induced adhesion and invasion were completely blocked by the TK inhibitor genistein and partially blocked by the PI3K inhibitor wortmannin, but not influenced by PKC inhibitor GF109203X. Downregulation of PKC did not affect invasion or adhesion induced by AIF-4 either. In contrast, GF109203X and PKC downregulation blocked PMA-induced adhesion, but genistein and wortmannin had no effect. Invasion and both AIF-4- and PMA-induced adhesion were completely blocked by the PLC inhibitor U73122. Mn(2+)-induced adhesion, which was not or was only partially blocked by the other inhibitors, was delayed by U73122, and spreading of Mn(2+)-treated cells was completely prevented by U73122. However, PLC activity during adhesion was not detected. We conclude that signals required for invasion and G-protein-induced adhesion are similar and are distinct from PKC-induced adhesion, and that in all cases PLC is likely to be activated, but is probably too local and/or transient to be detected.
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PMID:Activation of G-proteins with AIF-4 induces LFA-1-mediated adhesion of T-cell hybridoma cells to ICAM-1 by signal pathways that differ from phorbol ester- and manganese-induced adhesion. 908 64

1. The aim of the present study was to identify the sources of Ca2+ contributing to acetylcholine (ACh)-induced release of endothelium-derived hyperpolarizing factor (EDHF) from endothelial cells of rat mesenteric artery and to assess the pathway involved. The changes in membrane potentials of smooth muscles by ACh measured with the microelectrode technique were evaluated as a marker for EDHF release. 2. ACh elicited membrane hyperpolarization of smooth muscle cells in an endothelium-dependent manner. The hyperpolarizing response was not affected by treatment with 10 microM indomethacin, 300 microM NG-nitro-L-arginine or 10 microM oxyhaemoglobin, thereby indicating that the hyperpolarization is not mediated by prostanoids or nitric oxide but is presumably by EDHF. 3. In the presence of extracellular Ca2+, 1 microM ACh generated a hyperpolarization composed of the transient and sustained components. By contrast, in Ca(2+)-free medium, ACh produced only transient hyperpolarization. 4. Pretreatment with 100 nM thapsigargin and 3 microM cyclopiazonic acid, endoplasmic reticulum Ca(2+)-ATPase inhibitors, completely abolished ACh-induced hyperpolarization. Pretreatment with 20 mM caffeine also markedly attenuated ACh-induced hyperpolarization. However, the overall pattern and peak amplitude of hyperpolarization were unaffected by pretreatment with 1 microM ryanodine. 5. In the presence of 5 mM Ni2+ or 3 mM Mn2+, the hyperpolarizing response to ACh was transient, and the sustained component of hyperpolarization was not observed. On the other hand, 1 microM nifedipine had no effect on ACh-induced hyperpolarization. 6. ACh-induced hyperpolarization was nearly completely eliminated by 500 nM U-73122 or 200 microM 2-nitro-4-carboxyphenyl-N, N-diphenylcarbamate, inhibitors of phospholipase C, but was unchanged by 500 nM U-73343, an inactive form of U-73122. Pretreatment with 20 nM staurosporine, an inhibitor of protein kinase C, did not modify ACh-induced hyperpolarization. 7. These results indicate that the ACh-induced release of EDHF from endothelial cells of rat mesenteric artery is possibly initiated by Ca2+ release from inositol 1,4,5-trisphosphate (IP3)-sensitive Ca2+ pool as a consequence of stimulation of phospholipid hydrolysis due to phospholipase C activation, and maintained by Ca2+ influx via a Ni(2+)- and Mn(2+)-sensitive pathway distinct from L-type Ca2+ channels. The Ca(2+)-influx mechanism seems to be activated following IP3-induced depletion of the pool.
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PMID:Sources of Ca2+ in relation to generation of acetylcholine-induced endothelium-dependent hyperpolarization in rat mesenteric artery. 910 9

In rat neutrophils, formylmethionyl-leucyl-phenylalanine (fMLP)-induced inositol phosphate formation was concentration-dependently inhibited by acetylshikonin as well as by a putative phospholipase C (PLC) inhibitor [6-[[17beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-p yrrole-2,5-dione (U73122). The IC50 value of acetylshikonin for the inhibition of inositol trisphosphate (IP3) formation was estimated to be 16.1 +/- 1.5 microM. The reduction of inositol phosphate levels appeared to reflect inhibition of PLC activity because the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) catalyzed by a soluble fraction from neutrophils was also inhibited by acetylshikonin (IC50 value 21.4 +/- 6.1 microM) over the same range of concentrations. Although acetylshikonin alone evoked Ca2+ and Mn2+ influx into neutrophils in Ca2+-containing medium, acetylshikonin, like U73122, inhibited Ca2+ release (IC50 value approximately 5.3 +/- 0.4 microM) from internal stores in Ca2+-free medium. These results indicate that acetylshikonin inhibits phosphatidylinositol signaling in neutrophils.
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PMID:Impairment of phosphatidylinositol signaling in acetylshikonin-treated neutrophils. 917 22


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