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)

In this study we have used a density perturbation method to isolate anti-Thy-1 antibody-induced Thy-1 caps from mouse T-lymphoma cells in the absence of detergents, and then compared the phospholipid composition of these capped membranes with that of uncapped membranes. Initial phospholipid analysis by two-dimensional thin layer chromatography (2-D TLC) reveals a significant increase in the amount of 32P-labeled phosphatidylcholine in the Thy-1 capped membrane. In contrast, no significant changes are observed in the labeling of phosphatidylserine, phosphatidylethanolamine, or the sphingomyelins. Therefore, it is suggested that phosphatidylcholine may be involved in the organization and/or regulation of Thy-1 antigen redistribution. The composition of phosphoinositide in uncapped and capped membranes was analysed separately using one-dimensional thin layer chromatography (1-D TLC) to resolve phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PlP), and phosphatidylinositol 4, 5-bisphosphate (PIP2) from all other phospholipids. This analysis reveals a significant reduction in levels of PIP and PIP2, but not PI, in Thy-1 caps. Through the use of ion exchange column chromatography, we have found an increased production of all three species of inositol phosphates during anti-Thy-1 antibody-induced capping. Inositol 1, 4, 5-triphosphate (IP3) shows the most significant increase, compared to the much smaller increases in inositol 4, 5-bisphosphate (IP2) and inositol monophosphate (IP). These results suggest that the binding of anti-Thy-1 antibody to Thy-1 antigen activates phospholipase C which, in turn, initiates polyphosphoinositide turnover and IP3 production. It is proposed that these observed effects are the result of early signal transducing events which are prerequisite steps in Thy-1 receptor cap formation.
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PMID:Isolation of Thy-1 caps and analysis of their phospholipid composition in mouse T-lymphoma cells. 282 3

To investigate whether guanosine triphosphate-binding proteins (G proteins) are involved in T cell activation, tests were made of the effect of pertussis toxin, cholera toxin, guanosine 5'-(3-O-thio)-triphosphate, and fluoride ions on interleukin 2 (IL-2) synthesis in Jurkat cells. It was found: 1) that pertussis toxin interferes with the first pathway of T cell activation insofar as it can substitute for phytohemagglutinin or monoclonal antibodies directed against the CD3 surface proteins, suggesting that a G protein serves as transducer for signals via the T cell receptor-CD3 complex; and 2) that fluoride ions induce the release of diacylglycerol (DAG) from [3H] arachidonic acid or [3H]oleic acid-prelabeled cells. In [3H]inositol or 32P-prelabeled cells, the increase in DAG production was also found to be accompanied by a 280% increase of intracellular inositol phosphate (IP), without significant modification of IP2 and IP3. These results suggest that a G protein controls the activity of a phospholipase C in Jurkat cells that upon stimulation releases DAG but not IP3. Inasmuch as DAG, like the phorbol ester tetradecanoyl phorbol acetate, activates protein kinase C, it suggests that a G protein is also involved in the transduction of the second signal for lymphocyte activation. Fluoride ions were found to be as effective as tetradecanoyl phorbol acetate to stimulate IL-2 synthesis in Jurkat cells when used in combination with phytohemagglutinin. Finally, cholera toxin and guanosine 5'-(3-O-thio)-triphosphate were found to increase intracellular cyclic adenosine triphosphate and to inhibit IL-2 synthesis. All together these results suggest that several G proteins are involved in the transduction of the two signals necessary for T cell activation as well as in the negative regulation of IL-2 synthesis.
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PMID:Inhibition and activation of interleukin 2 synthesis by direct modification of guanosine triphosphate-binding proteins. 282 88

The plasma-membrane receptors, coupling mechanisms, and effector enzymes that mediate target-cell activation by angiotensin II (AII) have been characterized in rat and bovine adrenal glomerulosa cells. The AII holoreceptor is a glycoprotein of Mr approximately 125,000 under non-denaturing conditions. Photoaffinity labeling of AII receptors with azido-AII derivatives has shown size heterogeneity among the AII binding sites between species and target tissues, with Mr values of 55,000 to 79,000. Such variations in molecular size probably reflect differences in carbohydrate content of the individual receptor sites. The adrenal AII receptor, like that in other tissues, is coupled to the inhibitory guanine nucleotide inhibitory protein (Ni). However, studies with pertussis toxin have shown that stimulation of aldosterone production by AII is not mediated by Ni but by a pertussis-insensitive nucleotide regulatory protein of unidentified nature. Although Ni is not involved in the stimulatory action of AII on steroidogenesis, it does mediate the inhibitory effects of high concentrations of AII upon aldosterone production. The actions of AII on adrenal cortical function are thus regulated by at least two guanine nucleotide regulatory proteins that are selectively activated by increasing AII concentrations. The principal effector enzyme in AII action is phospholipase C, which is rapidly stimulated in rat and bovine glomerulosa after AII receptor activation. AII-induced breakdown of phosphatidylinositol bisphosphate (PIP2) and phosphatidylinositol phosphate (PIP) leads to formation of inositol 1,4,5-trisphosphate (IP3) and inositol 1,4-bisphosphate (IP2). These are metabolized predominantly to inositol-4-monophosphate, which serves as a marker of polyphosphoinositide breakdown, whereas inositol-1-phosphate is largely derived from phosphatidylinositol hydrolysis. The AII-stimulated glomerulosa cell also produces inositol 1,3,4-trisphosphate, a biologically inactive IP3 isomer formed from Ins-1,4,5-trisphosphate via inositol tetrakisphosphate (IP4) during ligand activation in several calcium-dependent target cells. The Ins-1,4,5-P3 formed during AII action binds with high affinity to specific intracellular receptors that have been characterized in the bovine adrenal gland and other AII target tissues, and may represent the sites through which IP3 causes calcium mobilization during the initiation of cellular responses.
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PMID:Angiotensin II receptors and mechanisms of action in adrenal glomerulosa cells. 282 11

Rat intestinal epithelial cells were labelled with [32P]Pi and extracted, and the phospholipids were analysed by thin-layer chromatography. 32P-incorporation in phosphatidylinositol (PI) and phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-phosphate (PIP2) were measured in control and heat stable enterotoxin (ST)-treated cells. ST was found to induce rapid degradation of PIP and PIP2. The degradation of inositol lipids was accompanied by an increase of water soluble inositol phosphate (IP1, IP2, IP3) compounds. There was a two-fold increase of radioactivity in IP2 and IP3 but no significant change was observed in IP1. Phospholipase C activity was increased tenfold with substrate PIP2 in ST-pretreated cells. The present study indicates that ST triggers another second messenger system by increasing the PIP2 hydrolysis with the enzyme phospholipase C.
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PMID:Stimulation of phosphoinositides breakdown by the heat stable E. coli enterotoxin in rat intestinal epithelial cells. 284 95

In cultured rabbit vascular smooth muscle cells (VSMC), platelet-derived growth factor (PDGF), a potent mitogen for VSMC, induced the dose- and time-dependent formation of inositol mono-, bis- and trisphosphates (IP1, IP2 and IP3, respectively). The doses of PDGF necessary for these reactions were similar to those for DNA synthesis. The maximal level of IP1 was comparable to, and those of IP2 and IP3 were about half of those induced by angiotensin II, a potent vasoconstrictor. However, the time courses of the PDGF-induced reactions were slower than those of the angiotensin II-induced ones. Moreover, protein kinase C-activating phorbol esters inhibited the angiotensin II-induced reactions, but did not the PDGF-induced ones. These results indicate that PDGF induces the phospholipase C reactions in VSMC but suggest that the signaling mechanism of PDGF to the phospholipase C is different from that of angiotensin II.
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PMID:Platelet-derived growth factor (PDGF)-induced phospholipase C-mediated hydrolysis of phosphoinositides in vascular smooth muscle cells--different sensitivity of PDGF- and angiotensin II-induced phospholipase C reactions to protein kinase C-activating phorbol esters. 284 20

The present studies were conducted to determine whether the large or small bovine luteal cell was the site for the stimulatory effect of prostaglandin F2 alpha (PGF) on phospholipase C-catalyzed inositol phospholipid hydrolysis. Corpora lutea were removed from heifers during the luteal phase of the normal estrous cycle. Small luteal cells were isolated by unit-gravity sedimentation and large luteal cells were isolated by flow cytometry using a Becton Dickson FACS 440 cell sorter. PGF provoked rapid (5-30 s) and sustained (up to 30 min) increases in the levels of inositol mono-, bis-, and trisphosphates (IP, IP2, IP3, respectively) in small luteal cells. IP3 was formed more rapidly than IP2 or IP following PGF treatment. The PGF-stimulated increase in IP3 was accompanied by a transient reduction in the levels of 3H-labeled phosphatidylinositol 4,5-bisphosphate. LiCl (10 mM) enhanced inositol phosphate accumulation in response to PGF. Maximal increases in inositol phosphate accumulation were observed with 1-10 microM PGF and half-maximal increases were observed with 60 nM PGF. PGF (1-10 microM) had no effect on cAMP levels but stimulated small increases in progesterone accumulation in 30 min incubations of small luteal cells. PGF also increased the accumulation of inositol phosphates in large luteal cells. The increases were apparent within 5 min of incubation (the earliest time examined) and further increases were observed in incubations lasting 30 min. PGF had no significant effect on cAMP or progesterone in 30 min incubations of large cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Acute effects of prostaglandin F2 alpha on inositol phospholipid hydrolysis in the large and small cells of the bovine corpus luteum. 285 Feb 43

Binding of chemoattractants to specific cell surface receptors on human polymorphonuclear leukocytes (PMNs) initiates a variety of biologic responses, including directed migration (chemotaxis), release of superoxide anions, and lysosomal enzyme secretion. Chemoattractant receptors belong to a large class of receptors which utilize the hydrolysis of polyphosphoinositides to initiate Ca2+ mobilization and cellular activation. Receptor occupancy leads to phospholipase C-mediated hydrolysis of polyphosphoinositol 4,5-bisphosphate (PIP2) yielding inositol 1,4,5-trisphosphate (IP3) and 1,2 sn-diacylglycerol (DAG). These products synergize to initiate cell activation via calcium mobilization (IP3) and protein kinase C activation (DAG). Pertussis toxin, which ADP-ribosylates and inactivates some GTP binding proteins (G proteins), abolishes all chemoattractant-induced responses, including Ca2+ mobilization, IP3 and DAG production, enzyme secretion, superoxide production and chemotaxis. Direct evidence for chemoattractant receptor: G protein coupling was obtained using PMN membrane preparations which contain a Ca2+-sensitive phospholipase C. Hydrolysis of polyphosphoinositides at resting intracellular Ca2+ levels (100 nm) was only observed when the membranes were stimulated with the chemoattractant N-formyl-methyl-leucyl-phenylalanine (fMet-Leu-Phe) in the presence of GTP. Myeloid cells contain two distinct pertussis toxin substrates of similar molecular weight (40 and 41 kD). The 41 kD substrate resembles Gi, whereas a 40 kD substrate is physically associated with a partially purified fMet-Leu-Phe receptor preparation and may therefore represent a novel G protein involved in chemoattractant-stimulated responses. Metabolism of 1,4,5-IP3 to inositol proceeds via two distinct pathways in PMNs: (1) degradation to 1,4-IP2 and 4-IP1 or (2) conversion to 1,3,4,5-IP4, 1,3,4-IP3, 3,4-IP2 and 3-IP1. Initial formation (0-30 s) of 1,4,5-IP3 and DAG occurs at ambient intracellular Ca2+ levels, whereas formation of 1,3,4-IP3 and a second sustained phase of DAG production (30 s-10 min) require elevated cytosolic Ca2+ influx. The later peak of DAG, which is not derived from phosphoinositides, appears to be required for stimulation of respiratory burst activity. Products formed during activation can feed back to attenuate chemoattractant receptor-mediated stimulation of phospholipase C by uncoupling receptor-G protein-phospholipase C interaction.
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PMID:Signal transduction in cells following binding of chemoattractants to membrane receptors. 290 Nov 61

Deoxycholate promotes phospholipase C degradation of endogenous phosphatidyl[3H]inositol (Pl), phosphatidyl[3H]inositol monophosphate (PIP) and phosphatidyl[3H]inositol bisphosphate (PIP2) in rat cornea and human platelets. Hydrolysis of phosphatidyl[3H]inositol significantly lags polyphospho[3H]inositide degradation. Concomitantly, formation of [3H]inositol monophosphate (IP1) lags behind [3H]inositol bisphosphate (IP2) and [3H]inositol trisphosphate (IP3) production. These results demonstrate that rat cornea and human platelet phospholipase C cause a preferential hydrolysis of the endogenous polyphosphoinositides rather than phosphatidylinositol.
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PMID:Deoxycholate induces the preferential hydrolysis of polyphosphoinositides by human platelet and rat corneal phospholipase C. 299 Apr 55

Human platelet plasma membranes incubated in the presence of [gamma-32P]ATP and 15 mM MgCl2 incorporated radioactivity mostly into phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 4-phosphate (PIP), which represented together over 90% of the total lipid radioactivity. After washing, reincubation of prelabelled membranes revealed some hydrolysis of the two compounds by phosphomonoesterase(s), as detected by the release of radioactive inorganic phosphate (Pi) from the two phospholipids. This degradation attained 40%/30 min for PIP in the presence of 2 mM calcium and cytosol. The effect of calcium was observed at concentrations equal to or greater than 10(-4) M. In no case did calcium alone facilitate the formation of inositol 1,4,5-trisphosphate (IP3) and inositol 1,4-bisphosphate (IP2). In contrast, simultaneous addition of 2 mM calcium and 2 mg/ml sodium deoxycholate promoted the formation of IP3 and IP2, indicating phosphodiesteratic cleavage of PIP2 and PIP. Phospholipase C activity was detected at calcium concentrations as low as 10(-7) M, in which case PIP2 hydrolysis was slightly more pronounced compared to PIP. Addition of cytosol increased to some extent the phospholipase C activity, suggesting that the low amount of enzyme remaining in the membrane is sufficient to promote submaximal degradation of PIP2 and PIP. We conclude that platelet polyphosphoinositides are present in the plasma membrane in a state where they remain inaccessible to phospholipase C, which is still fully active even at basal calcium concentrations, i.e., 10(-7) M. These results support the view that phosphodiesteratic cleavage of PIP2 promotes and thus precedes calcium mobilization brought about by IP3. The in vitro model presented here may prove very useful in future studies dealing with the mechanism rendering polyphosphoinositides accessible to phospholipase C attack upon agonist-receptor binding.
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PMID:Studies of endogenous polyphosphoinositide hydrolysis in human platelet membranes. Evidence that polyphosphoinositides remain inaccessible to phosphodiesterase in the native membrane. 300 80

Electrically permeabilized cells of rat parotid gland, prelabelled with [3H]-inositol, synthesized [3H]-inositol phosphates (IP3 and IP2) when stimulated with alpha 1-adrenergic, muscarinic-cholinergic, and substance P receptor-agonists. Non-hydrolyzable analogues of GTP (GTP gamma S and GppNHp) also stimulated [3H]-IP3 formation by permeabilized cells and they potentiated the stimulation by receptor-agonists. These effects of guanine nucleotides occurred only with GTP analogues and only in permeabilized cells indicating an intracellular site of action. NaF stimulated [3H]-IP3 accumulation, an effect that was not entirely attributable to the ability of F- to inhibit (1,4,5)IP3 degradation. These results suggest that a guanine nucleotide-dependent regulatory protein couples Ca2+-mobilizing receptors to phospholipase C in parotid gland.
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PMID:A guanine nucleotide-dependent regulatory protein couples substance P receptors to phospholipase C in rat parotid gland. 301 Sep 71


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