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)

Two distinct inositol phospholipid-specific phospholipase C (PLC; phosphatidylcholine phosphatidohydrolase, EC 3.1.4.3) isozymes, PLC-I and PLC-II, have been purified and characterized from bovine brain. Monoclonal antibodies that distinguish between these isozymes are used in the present study to map isozyme distribution in the rat brain with immunohistochemical techniques. Both isozymes are localized in neurons, and, whereas PLC-II is rather ubiquitous--being expressed in most neurons, PLC-I is restricted in its distribution. The strongest immunoreactive labeling for PLC-I is in the neurons of the striatum, which provide inputs to the globus pallidus and substantia nigra, where terminals are also densely labeled. The neuronal targets of these terminals in the globus pallidus and substantia nigra do not express PLC-I immunoreactivity, but they do display PLC-II immunoreactivity. PLC-I immunoreactivity is also particularly well pronounced in the pyramidal cells of the hippocampus and, to a lesser extent, in the granule cells of the dentate gyrus. In the thalamus, PLC-I is localized to neurons in the reticular thalamic nucleus, in the medial subdivision of the mediodorsal thalamic nucleus, and in the anteromedial thalamic nucleus. Other areas displaying PLC-I immunoreactive neurons include the dorsal lateral septal nucleus and the basolateral amygdala. The expression of at least one or more forms of PLC in most neurons of the brain suggests that this enzyme may be part of a common system of signal transduction used universally by all neurons. However, the differential expression of PLC isozymes suggests further that certain neurotransmitter and receptor interactions may differ in the forms of the PLC enzyme used for signal transduction.
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PMID:Phospholipase C I and II brain isozymes: immunohistochemical localization in neuronal systems in rat brain. 336 68

Three phospholipase C isozymes (PLC-I, II, and III) have been purified from bovine brain. Here, phospholipase C-related cDNA clones corresponding to PLC-I and PLC-III were isolated from a rat brain lambda gt11 expression cDNA library using specific monoclonal antibodies and sequenced. Each of them encodes a distinct polypeptide with a calculated molecular mass of 138,225 (PLC-I) and 85,840 (PLC-III). Comparison of these two with the sequence of another isozyme PLC-II (Mr = 148,431) that we have previously characterized revealed a low overall sequence homology. Nevertheless, a significant amino acid sequence similarity between the three enzymes was found in two regions, one of about 150 amino acids and the other of about 120 amino acids. The two conserved domains were separated by a variable region. The variable region sequence of PLC-II is relatively long and has recently been shown to contain regions homologous to the noncatalytic domain of the nonreceptor tyrosine kinases. Those of PLC-I and III were short and appeared to be unrelated to these tyrosine kinases. The physiological implications of the multiple species of PLC enzymes are discussed.
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PMID:Cloning and sequence of multiple forms of phospholipase C. 339 Aug 63

We previously reported that cytosolic fractions of bovine brain contain two immunologically distinct forms of phospholipase C (PLC), PLC-I and PLC-II. We now report the purification of another form of inositolphospholipid-specific phospholipase C from bovine brain cytosol, designated PLC-III, and the comparison of the catalytic properties of the three isozymes. Approximately 450 micrograms of pure PLC-III was obtained from 36 bovine brains, and it had a final specific activity of 30-40 mumol of phosphatidylinositol hydrolyzed per min per mg of enzyme in the presence of 0.1% deoxycholate. PLC-III exhibited an apparent Mr of 85,000 in NaDodSO4/PAGE, which is considerably smaller than the Mr of 150,000 for PLC-I and 145,000 for PLC-II. Neither of the two mixtures of monoclonal antibodies nor the rabbit polyclonal antibodies directed against either PLC-I or PLC-II cross-reacted with PLC-III. The catalytic properties of the three isozymes were studied by using small unilamellar vesicles prepared from either phosphatidylinositol (PtdIns) or phosphatidylinositol 4,5-bisphosphate (PtdInsP2) as substrates. Hydrolysis of both PtdIns and PtdInsP2 by the three enzymes was dependent on Ca2+. However, at low Ca2+ concentration, PtdInsP2 was the preferred substrate for all three enzymes. When PtdIns was the substrate, the three enzymes exhibited similar specific activities at their optimum pH, which was 4.8 for PLC-I, 5.0 for PLC-II, and 5.5 for PLC-III. But at neutral pH, the order of specific activity was PLC-III greater than PLC-II greater than PLC-I. In contrast, the order of specific activity was PLC-I greater than PLC-III greater than PLC-II for PtdInsP2 hydrolysis, which means that PLC-I is the most specific for PtdInsP2. The three enzymes were affected differently by bovine serum albumin: inhibition of PLC-I and activation of PLC-III were observed, whereas PLC-II was unaffected. This observation suggests that any putative protein effectors for PLC should be critically scrutinized.
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PMID:Bovine brain cytosol contains three immunologically distinct forms of inositolphospholipid-specific phospholipase C. 347 95

Sheep seminal vesicles contain two immunologically distinct phospholipase C (PLC) enzymes that can hydrolyze phosphatidylinositol (PI) (Hofmann, S.L., and Majerus, P.W. (1982) J. Biol. Chem. 257, 6461-6469). One of these enzymes (PLC-I) has been purified to homogeneity; the second (PLC-II) has been purified 2600-fold from a crude extract of seminal vesicles. In the present study we have compared the ability of these purified enzymes to hydrolyze PI, phosphatidylinositol 4-phosphate (PI-4-P), and phosphatidylinositol 4,5-diphosphate (PI-4,5-P2). Using radiolabeled substrates in small unilamellar phospholipid vesicles of defined composition, the two enzymes were found to hydrolyze all three of the phosphoinositides. Hydrolysis of all three phosphoinositides by both enzymes was stimulated by Ca2+; however, in the presence of EGTA only the polyphosphoinositides were hydrolyzed. The two enzymes displayed substrate affinities in the order PI greater than PI-4-P greater than PI-4,5-P2, and maximum hydrolysis rates in the order PI-4,5-P2 greater than PI-4-P greater than PI. When present in the same vesicles, PI and the polyphosphoinositides competed for a limiting amount of either enzyme. Inclusion of phosphatidylcholine into vesicles containing the phosphoinositides resulted in greater inhibition of PI hydrolysis than polyphosphoinositide hydrolysis. When all three phosphoinositides were present in vesicles mimicking the cytoplasmic leaflet of cell membranes, there was preferential hydrolysis of the polyphosphoinositides over PI. We conclude that a single phospholipase C can account for the hydrolysis of all three phosphoinositides seen during agonist-induced stimulation of secretory cells. The cytoplasmic Ca2+ concentration and phospholipid composition of the membrane, however, may influence the relative rate of hydrolysis of the three phosphoinositides.
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PMID:Hydrolysis of polyphosphoinositides by purified sheep seminal vesicle phospholipase C enzymes. 609 Apr 45

The expression of phospholipase C isozymes and phosphatidylinositol 4-kinase in the rat facial nucleus was studied using in situ hybridization at various times after unilateral crushing and resectioning the facial nerve. The level of phospholipase C alpha messenger RNA increased from three days to one week after the operation. On the other hand, an apparent reduction in the level of phospholipase C beta 1 occurred from three days to one week after resection. After either crushing or resection, phospholipase C gamma 1 messenger RNA levels were not noticeably changed. As phosphatidylinositol 4-kinase is the rate-limiting enzyme for the production of phosphatidylinositol 4,5-bisphosphate, which is the preferred substrate for phospholipase C, we investigated the expression of phosphatidylinositol 4-kinase messenger RNA. The level of phosphatidylinositol 4-kinase messenger RNA was decreased one day after axonal injury. Among phospholipase C isozymes, phospholipase C alpha is up-regulated. As the structure of phospholipase C alpha is different from other isozymes, phospholipase C alpha is supposed to have a different function. The present unique up-regulation of phospholipase C alpha may suggest a novel function in nerve regeneration. Phospholipase C beta 1 is down-regulated, as is phosphatidylinositol 4-kinase. This suggests that the signal transmission system using a G-linked receptor is broken down after nerve injury. On the other hand, phospholipase C gamma 1, which is related to the receptor tyrosine kinase, does not demonstrate any transcriptional regulation after nerve injury.
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PMID:Differential regulation of phospholipase C isozymes in the rat facial nucleus following axotomy. 819 Feb 62

Two forms (I and II) of phosphoinositide-specific phospholipase C (PLC) were purified from the cytosol of bovine iris sphincter by sequential chromatography on DEAE-Sepharose, EAH-Sepharose, heparin-Sepharose, Sephacryl S-200 gel filtration and Mono Q HR columns. The final step resulted in specific activities of PLC-I and PLC-II of 4.3 and 5.9 mumol of phosphatidylinositol (PI) cleaved/min per mg of protein, which represented up to 295-fold purification compared with that of the starting supernatant. The purified enzymes were further investigated for the presence of isoenzymes and characterized for molecular mass, substrate specificity, pH, Ca2+ requirements and kinetic parameters. Using monoclonal antibodies, PLC-I was identified as PLC-delta 1. The apparent molecular mass of PLC-I as determined by SDS/PAGE and gel filtration was 85 kDa. PLC-II contained an apparently invisible protein band that reacted with the antibody against PLC-gamma 1, and a major 109 kDa protein band that was not recognized by any of the PLC monoclonal antibodies. Further purification of PLC-II by size-exclusion h.p.l.c. resulted in elution of the enzyme activity as a single peak which corresponded to 109 kDa position. Again, this PLC activity was not recognized by any of the PLC monoclonal antibodies. However, the 109 kDa protein activity was recognized by a polyclonal antibody raised against a rat PLC-gamma 1 fragment (amino acids 1272-1287), thus suggesting that this protein is a proteolytic product of PLC-gamma 1. PLC-delta 1 and PLC-gamma 1 were identified in the supernatant fraction and PLC-beta 1 in the membrane fraction of the iris sphincter. Although immunologically different, the catalytic properties of PLC-I and PLC-II were quite similar. The Vmax and Km values for phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis were three to five times greater than those for PI hydrolysis. Both forms preferred PIP and PIP2 over PI and both were inactive against phosphatidylcholine. With PIP2 as substrate, the optimal pH values for PLC-I and PLC-II were 6.5 and 7.5 respectively. Unlike PIP2, PI hydrolysis by both forms was dependent on the presence of free Ca2+. The maximal hydrolysis of PI and PIP2 by both forms occurred at 200 and 5 microM Ca2+ respectively. Incubation of the purified enzymes with the catalytic subunit of protein kinase A (PKA) and [gamma-32P]ATP resulted in increased phosphorylation of PLC-I and PLC-II, but it had no inhibitory effect on their enzyme activities.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Purification and characterization of phosphoinositide-specific phospholipase C from bovine iris sphincter smooth muscle. 838 Sep 92

Activation of phospholipase C (PLC) coupled to phosphoinositide (PtdIns) hydrolysis occurs through one of the two pathways. One of the major pathways for the neurotransmitter signaling involves phosphoinositide (PtdIns) specific and G-protein dependent PLC-beta, which stimulates the formation of inositol triphosphate (IP3) and inositol tetraphosphate (IP4). Another pathway through the stimulation of calcium influx can directly activate all of the PLC isozymes. At least three isozymes of PLC have been characterized in the brain; PLC-A (alpha), PLC-I (beta) and PLC-II (gamma), which are shown to be localized differentially in brain regions. Muscarinic-cholinergic signals are mediated in large part through the hydrolysis of PtdIns by PLC. To investigate changes in muscarinic coupling to PLC during aging, we examined carbachol stimulated and calcium stimulated PtdIns hydrolysis in cerebral cortical membranes in young, middle aged and old rats. In order to determine whether PtdIns hydrolysis changes correspond to PLC isozyme expression in these animals, we examined three subtypes of PLC mRNA expression in brain sections of young and old rats using in situ hybridization technique. Our study indicated decreased carbachol-induced PLC activity in the cerebral cortex and, in contrast, increased PLC-beta mRNA in the frontal cortex and superficial cortical layer of aged rats. PLC-alpha mRNA was decreased in hippocampal regions of older rats. These studies suggest that during aging there is an uncoupling of muscarinic stimulated PtdIns hydrolysis, which is accompanied by an increased PLC-beta mRNA and decreased PLC-alpha mRNA that may represent compensatory changes in PLC expression.
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PMID:Age-related loss of cholinergic-muscarinic coupling to PLC: comparison with changes in brain regional PLC subtypes mRNA distribution. 872 Aug 70

Some key elements of signal transduction have been identified within the nucleus and demonstrated to be responsive to specific agonists in numerous cell types. In particular, mitogenic stimuli have been reported to induce a transient increase of the nuclear phospholipase C beta 1 activity, causing the release of inositide-derived second messengers, whereas differentiating stimuli induced a decrease of the enzyme activity and an increase of nuclear phosphatidylinositol 4,5-bisphosphate (PIP2). Recently, we reported evidence, in human osteosarcoma Saos-2 cell lines, on the presence of specific nuclear phospholipase C isoforms and on the activation of phospholipase C beta 1 in the nucleus following the exposure to interleukin-1 alpha. In this study we report immunocytochemical ultrastructural evidence on quantitative variations of PIP2 and phospholipase C beta 1 amounts in the nucleus of Saos-2 cells at different times of exposure to interleukin-1 alpha. After short periods of culture in the presence of the agonist, the intranuclear amount of PIP2 is decreased, while a translocation of phospholipase C beta 1 occurs from the cytoplasm to the nucleus, in correspondence with the increased hydrolyzing activity of the enzyme. After longer periods of incubation with interleukin-1 alpha, on the other hand, the intranuclear amount of PIP2 is restored to initial level, while the amount of phospholipase C beta 1 is increased both at the nuclear and cytoplasmic level, when its activation is no longer effective. The results, compared with those obtained in other cell types responsive to given agonists, account for a cell-specific modulation of signal transduction based on polyphosphoinositide breakdown at the nuclear level.
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PMID:Interleukin-1 alpha induces variations of the intranuclear amount of phosphatidylinositol 4,5-bisphosphate and phospholipase C beta 1 in human osteosarcoma Saos-2 cells. 887 39

Receptor-mediated inositol 1,4,5-trisphosphate formation in most tissue is dependent on a variety of phospholipase C isoforms. To determine which phospholipase C isoforms were present in vascular smooth muscle compared to brain, liver, and spleen, we extracted proteins from these tissues and separated and identified the phospholipase C isoforms by immunoblotting. Aliquots of rat tail artery were examined by this procedure, together with aliquots of rat liver, spleen, cerebral cortex, hippocampus, cerebellum, aorta, and mesenteric artery. Phospholipase C gamma 1 was shown to be present in all of these tissues, while phospholipase C beta 1 was shown to be limited to fractions from brain. Phospholipase C delta 1 was detected in rat tail artery, mesenteric artery, aorta, and brain. Phospholipase C beta 2 was found in rat tail artery, liver, and brain. This is the first report of phospholipase C beta 2 in tissues other than HL60 cells. Since G proteins activate IP3 production via stimulation of phospholipase C beta isoforms in many tissues, and agonist-stimulated IP3 production in smooth muscle requires G protein activation, phospholipase C beta 2 may be required for agonist-stimulated force production in vascular smooth muscle.
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PMID:Phospholipase C beta 2 in vascular smooth muscle. 890 3

Acrosomal exocytosis occurs after the binding of the spermatozoon to the zona pellucida of the oocyte via specific receptors. We suggest that the zona pellucida binds to at least two different receptors in the plasma membrane. One (R) is a Gi-coupled receptor that activates phospholipase C beta 1. The other (TK) is a tyrosine kinase receptor coupled to phospholipase C gamma. Binding to R would regulate adenylyl cyclase leading to an increase in cyclic adenosine monophosphate and protein kinase A activation. The protein kinase A activates a voltage-dependent Ca2+ channel in the outer acrosomal membrane that releases Ca2+ from the interior of the acrosome to the cytosol. This is the first (I), relatively small, rise in intracellular Ca2+ which leads to activation of the phospholipase C gamma. The products of phosphatidyl-inositol bisphosphate hydrolysis by phospholipase C, diacylglycerol and inositol-trisphosphate lead to protein kinase C translocation to the plasma membrane and its activation. Protein kinase C opens a voltage-dependent Ca2+ channel (L) in the plasma membrane, leading to the second (II), higher, increase in intracellular Ca2+ leading to acrosomal exocytosis. Spermine, a physiological constituent of the seminal plasma regulates sperm acrosomal exocytosis by modulating intracellular Ca2+ binding sites and phospholipase C activity. Spermine is rapidly incorporated into the sperm cells during ejaculation and temporarily inhibits premature capacitation and acrosome reaction. During the passage of the spermatozoon through the female genital tract, there is a progressive depletion of spermine from spermatozoa, so that capacitation and consequently the acrosomal exocytosis take place at the appropriate time, when the spermatozoon reaches the vicinity of the egg.
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PMID:Regulatory mechanisms in acrosomal exocytosis. 941 80


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