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)

Plasma membrane preparations from KA31 (mouse) cells contained receptors for the binding of Rauscher murine leukemia virus (R-MuLV) envelope glycoprotein, gp70. This binding was demonstrated by gel filtration of a mixture of the microsomal fraction of the cells and 125I-labeled gp70. A rapid and convenient assay was developed to measure the complex formation between the membrane receptors and gp70 involving specific precipitation of the complex by 3 to 4% polyethylene glycol. The complex formation was responsive to the concentrations of both the receptor and gp70 and also to changes in temperature and pH. The gp70 binding was a noncooperative, saturable process, and an association constant of 3.5 X 10(8) M-1 was estimated from the binding data. The complex formation was reversible and a near-total exchange of 125I-labeled gp70 in the complex was achieved by incubation with excess of unlabeled gp70. The complex formation was inhibited by protein denaturing agents, guanidine-hydrochloride and urea. Pretreatment of the membrane fractions with either chymotrypsin or phospholipase C led to a loss of the membrane-associated receptor activity, indicating that a lipoprotein structure was important for the receptor function, consistent with the observation that nonionic detergents strongly inhibited the complex formation.
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PMID:Characterization of Rauscher murine leukemia virus envelope glycoprotein receptor in membranes from murine fibroblasts. 3 3

We investigated the signal transduction of serotonin secretion by stimulation with DNP-Ascaris antigen or ionomycin in rat basophilic leukemia cells (RBL-2H3). The modes of action of antigen and ionomycin for serotonin secretion were shown to be similar. The treatment of cells with antigen resulted in increased tyrosine phosphorylation of 105 and 72 KDa proteins, in particular, the tyrosine phosphorylation of 72 KDa protein seemed to correlate with serotonin secretion. Furthermore, we observed that antigen stimulation caused a marked increase in inositol polyphosphates production, which derived from the tyrosine phosphorylation of phospholipase C-gamma in RBL-2H3 cells. On the other hand, treatment with ionomycin also resulted in an increase in tyrosine phosphorylation of 72 KDa protein, but did not induce inositol polyphosphates production. These results suggested that the activation of tyrosine kinase may be related to serotonin secretion, and that intracellular Ca2+ increase may also play an important role in this activation.
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PMID:[The signal transduction of serotonin secretion involves protein tyrosine phosphorylation in rat basophilic leukemia cells]. 129 Apr 15

Aggregation of the high affinity receptor for IgE (Fc epsilon RI) on the surface of mast cells results in the rapid hydrolysis of membrane inositol phospholipids by phospholipase C (PLC). Although at least seven isoenzymes of PLC have been characterized in different mammalian cells, the isoenzyme involved in Fc epsilon RI-mediated signal transduction and the mechanism of its activation have not been demonstrated. We now report that PLC-gamma 1 is translocated to the membrane of mast cells after aggregation of Fc epsilon RI. Activation of rat basophilic leukemia cells, a rat mast cell line, with oligomeric IgE resulted in an increase in PLC activity in washed membrane preparations in a cell free assay containing exogenous [3H]phosphatidylinositol (PI). The increase in PLC activity has the same dose-response to oligomeric IgE as receptor mediated hydrolysis of inositol lipids (PI hydrolysis) in intact cells. Analysis by Western blot probed with anti-PLC-gamma 1 antibody revealed that there is a three- to fourfold increase in PLC-gamma 1 in membranes from activated cells. The increase in PLC activity is augmented a further 20% by the addition of orthovanadate to the incubation medium suggesting that a tyrosine phosphatase is involved in the down-regulation of this phenomenon. These findings demonstrate translocation of PLC-gamma 1 to the membrane following activation of a receptor which does not contain intrinsic tyrosine kinase activity. Activation of PLC-gamma 1 by this pathway may account for Fc epsilon RI-mediated PI hydrolysis.
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PMID:Phospholipase C-gamma 1 is translocated to the membrane of rat basophilic leukemia cells in response to aggregation of IgE receptors. 131 4

1. The presence of adenosine receptors linked to adenylate cyclase activity and their functional role in calcium-evoked 5-hydroxytryptamine (5-HT) release was investigated in rat basophilic leukaemia (RBL) cells, a widely used model for studying the molecular mechanisms responsible for stimulus-secretion coupling. 2. In [3H]-5-HT-loaded cells triggered to release by the calcium ionophore A23187, a biphasic modulation of 5-HT secretion was induced by adenosine analogues, with inhibition of stimulated release at nM and potentiation at microM concentrations, suggesting the presence of adenosine receptor subtypes mediating opposite effects on calcium-dependent release. This was also confirmed by results obtained with other agents interfering with adenosine pharmacology, such as adenosine deaminase and the non-selective A1/A2 antagonist 8-phenyl-theophylline. 3. Similar biphasic dose-response curves were obtained with a variety of adenosine analogues on basal adenylate cyclase activity in RBL cells, with inhibition and stimulation of adenosine 3':5'-cyclic monophosphate (cyclic AMP) production at nM and microM concentrations, respectively. The rank order of potency of adenosine analogues for inhibition and stimulation of adenylate cyclase activity and the involvement of G-proteins in modulation of cyclic AMP levels suggested the presence of cyclase-linked A1 high-affinity and A2-like low-affinity adenosine receptor subtypes. However, the atypical antagonism profile displayed by adenosine receptor xanthine antagonists on cyclase stimulation suggested that the A2-like receptor expressed by RBL cells might represent a novel cyclase-coupled A2 receptor subtype.4. Micromolar concentrations of adenosine analogues could also increase inositol phospholipid hydrolysis and inositol tris-phosphate formation in both unstimulated cells and in cells triggered to release by the calcium ionophore. The stimulation was constant, small and additive to that exerted by the calcium ionophore.5. It is concluded that RBL cells express both A1 and A2-like adenosine receptors which exert opposite effects on 5-HT release and intracellular cyclic AMP levels. However, besides modulation of cyclic AMP levels, additional transduction pathways, such as modulation of phospholipase C activity, may contribute to the release response evoked by adenosine analogues in this cell-line.
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PMID:Adenosine receptors in rat basophilic leukaemia cells: transductional mechanisms and effects on 5-hydroxytryptamine release. 131 28

Formyl-methionine-containing peptides (e.g. fMet-Leu-Phe) stimulate a variety of neutrophil functions by interacting with specific cell surface receptors which are coupled via G-proteins to stimulation of phospholipase C. Two markedly distinct cDNAs coding for formyl peptide receptors have recently been isolated from a rabbit and a human cDNA library respectively. To examine the hitherto unknown signal transduction properties of the formyl peptide receptor encoded by the human cDNA, we have used the PCR to clone this cDNA from poly(A)+ RNA of myeloid differentiated human leukaemia (HL-60) cells, and have injected the cDNA-derived receptor cRNA into Xenopus laevis oocytes. Receptor activity was determined electrophysiologically by measuring the agonist-dependent opening of intracellular Ca2+ concentration ([Ca2+]i)-independent Cl- channels. Injection of pure formyl peptide receptor cRNA did not lead to peptide-dependent changes in membrane current. In contrast, marked alterations of membrane current were observed in response to formyl peptides when the receptor cRNA was supplemented with poly(A)+ RNA isolated from undifferentiated HL-60 cells. Injection of the latter RNA did not lead to formyl-peptide-dependent alterations of membrane current. Binding studies using a radioiodinated formyl peptide revealed that injection of formyl peptide receptor cRNA alone led to expression of the formyl peptide receptor on the oocyte surface, and that co-injection of poly(A)+ RNA from undifferentiated HL-60 cells did not alter the level of receptor expression. Size fractionation of poly(A)+ RNA from undifferentiated HL-60 cells showed that the mRNA required to complement formyl-peptide-dependent signal transduction in oocytes had a size of approx. 3-3.5 kb. These results strongly suggest that the human formyl peptide receptor requires a specific cofactor(s), which is lacking in Xenopus oocytes but is present in undifferentiated HL-60 cells, to activate the second messenger pathway in oocytes. Identification of this factor will provide important information about the molecular mechanisms by which G-protein-coupled granulocyte-activating receptors stimulate phospholipase C.
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PMID:Complementation of formyl peptide receptor-mediated signal transduction in Xenopus laevis oocytes. 131 22

Biotin derivatives of methotrexate (biotin-SS-MTX) and folate (biotin-SS-folate), in which the functional components are joined by a dissociable disulfide-containing spacer, have been synthesized, purified by DEAE-Trisacryl chromatography, and characterized by HPLC, elemental analysis and mass spectrometry. These compounds provide a convenient means for the single-step purification of the folate transporters from L1210 cells. Parental L1210 murine leukemia cells, which contain only the microM transporter (the reduced folate/MTX transport protein) were treated with the N-hydroxysulfosuccinimide ester of biotin-SS-MTX, and a detergent extract of the plasma membranes was exposed to streptavidin-agarose beads to adsorb the labeled protein. Dithiothreitol cleavage of the disulfide linkage released the transporter, which migrated as a well-defined component (43 kDa) on SDS-PAGE gels; no other proteins were present. An L1210 subline (JF), obtained by adapting cells to grow on nanomolar concentrations of folate, contains both the microM transporter and the nM transporter (high-affinity folate binding protein). When these cells were treated with the N-hydroxysulfosuccimide ester of biotin-SS-folate and processed as described above, analysis on SDS-PAGE gels revealed the presence of two proteins, the microM transporter (43 kDa) and the nM transporter (39 kDa). Both transporters were characterized with respect to amino acid content; blocked N-termini precluded Edman sequencing. Treatment of the nM transporter with peptide:N-glycosidase F produced a smaller component (32 kDa); the microM transporter, conversely, was unchanged by this procedure. When the microM transporter in parental L1210 cells was labeled with fluorescein-MTX and then treated with phosphoinositol-specific phospholipase C (PI-PLC), no change in fluorescence was detected. Alternatively, when the nM transporter in the JF subline was labeled with fluorescein-folate and then treated with PI-PLC, complete loss of fluorescence was observed. These results indicate that the L1210 microM transporter is a non-glycosylated, integral membrane protein, while its nM counterpart is heavily glycosylated and anchored exofacially to the membrane by a glycosylphosphatidylinositol component.
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PMID:Multiple folate transport systems in L1210 cells. 132 5

Naturally occurring recombinant murine leukemia viruses (MuLVs), termed mink cell focus-inducing (MCF) viruses, are the proximal leukemogens in spontaneous thymic lymphomas of AKR mice. The mechanism by which these viruses transform lymphocytes is not clear. Previous studies have implicated either integrational activation of proto-oncogenes, chronic autocrine immune stimulation, and/or autocrine stimulation of growth factor receptors (e.g., interleukin 2 receptors) via binding of the viral env glycoprotein (gp70) to these receptors. Any one of these events could also involve activation of second messenger signaling pathways in the cell. We examined whether infection with oncogenic AKR-247 MCF MuLV induced transmembrane signaling cascades in thymocytes of AKR mice. Cyclic AMP levels were not changed, but there was enhanced turnover of phosphatidylinositol phosphates, with concomitant increases in diacyglycerol and inositol 1,4,5-triphosphate. Thus, phospholipase C activity was increased. Protein kinase C activity was also elevated in comparison to that in uninfected thymocytes. The above events occurred in parallel with MCF expression in the thymus and were chronically maintained thereafter. No changes in phospholipid turnover occurred in an organ which did not replicate the MCF virus (spleen) or in thymocytes of AKR mice infected with a thymotropic, nononcogenic MCF virus (AKV-1-C36). Therefore, only the oncogenic MCF virus induced phosphatidylinositol signal transduction. Flow cytometric comparison of cell surface gp70 revealed that AKR-247 MCF virus-infected thymocytes expressed more MCF virus gp70 than did thymocytes from AKV-1-C36 MCF virus-infected mice, suggesting that certain threshold quantities of MCF virus env glycoproteins may be involved in this signaling. This type of signal transduction is not induced by stimulation of the interleukin 2 receptor but is involved in certain oncogene systems (e.g., ras and fms). Its chronic induction by oncogenic MCF MuLV may thus initiate thymocyte transformation.
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PMID:Oncogenicity of AKR mink cell focus-inducing murine leukemia virus correlates with induction of chronic phosphatidylinositol signal transduction. 132 63

A novel hematopoietic antigen was identified using a murine monoclonal antibody raised against KG-1 cells. This antigen, termed MKW, was also detected on the surface of the monocytic cell line U937, but not on the K562, ML1, or HL-60 cell lines. On normal hematopoietic cells, the antigen is expressed on the surface of monocytic and myelocytic cells and on a subpopulation of B-cells. During normal hematopoiesis, the surface expression of MKW is greatest and occurs very early on monocytic cells. Alternatively, in myeloid cells, surface expression occurs later and cell maturation is correlated with increased surface expression. When U937 cells are induced to differentiate, surface expression is transiently up-regulated. Surface expression of MKW, however, does not appear to be an activation antigen since activation of purified T- or B-cells failed to increase MKW on the cell surface. Leukemic blasts from 22 of 80 children (27%) with acute myeloblastic leukemia and from 29 of 225 children (13%) with acute lymphoblastic leukemia expressed MKW on the cell surface. Although surface expression of MKW was absent on T-cell lines, peripheral T-cells, and most B-cells, the antigen was identified in the cytoplasm of some B-cells, T-cells, and cell lines. Immunoprecipitation studies showed that MKW is a 52-kDa protein whether expressed on the cell surface or in the cytoplasm, and it appears to be nonglycosylated. Furthermore, studies with phosphatidylinositol-phospholipase C suggested that MKW is not attached to a glycolipid anchor. The biochemical characterization of MKW and its pattern of expression are distinct from any of the previously identified CD groups or published antigens. Since this unique antigen has prognostic significance in leukemia and appears to be associated with cell differentiation, its exact role in hematopoiesis should be investigated.
Leukemia 1992 Oct
PMID:MKW, a novel hematopoietic antigen. 132 77

Signalling proteins such as phospholipase C-gamma (PLC-gamma) or GTPase-activating protein (GAP) of ras contain conserved regions of approximately 100 amino acids termed src homology 2 (SH2) domains. SH2 domains were shown to be responsible for mediating association between signalling proteins and tyrosine-phosphorylated proteins, including growth factor receptors. Nck is an ubiquitously expressed protein consisting exclusively of one SH2 and three SH3 domains. Here we show that epidermal growth factor or platelet-derived growth factor stimulation of intact human or murine cells leads to phosphorylation of Nck protein on tyrosine, serine, and threonine residues. Similar stimulation of Nck phosphorylation was detected upon activation of rat basophilic leukemia RBL-2H3 cells by cross-linking of the high-affinity immunoglobulin E receptors (Fc epsilon RI). Ligand-activated, tyrosine-autophosphorylated platelet-derived growth factor or epidermal growth factor receptors were coimmunoprecipitated with anti-Nck antibodies, and the association with either receptor molecule was mediated by the SH2 domain of Nck. Addition of phorbol ester was also able to stimulate Nck phosphorylation on serine residues. However, growth factor-induced serine/threonine phosphorylation of Nck was not mediated by protein kinase C. Interestingly, approximately fivefold overexpression of Nck in NIH 3T3 cells resulted in formation of oncogenic foci. These results show that Nck is an oncogenic protein and a common target for the action of different surface receptors. Nck probably functions as an adaptor protein which links surface receptors with tyrosine kinase activity to downstream signalling pathways involved in the control of cell proliferation.
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PMID:The SH2 and SH3 domain-containing Nck protein is oncogenic and a common target for phosphorylation by different surface receptors. 133 47

Recently, we demonstrated that aggregation of the high affinity IgE receptor in rat basophilic leukemia (RBL-2H3) cells results in rapid tyrosine phosphorylation of a 72-kDa protein (pp72). Here we investigated the relationship of pp72 phosphorylation to guanine nucleotide-binding protein (G protein) activation and phosphatidylinositol hydrolysis. The activation of G proteins by NaF in intact cells or by guanosine 5'-O-(3-thiotriphosphate) in streptolysin O-permeabilized cells induced both phosphatidylinositol hydrolysis and histamine release without tyrosine phosphorylation of pp72. Similarly, in RBL-2H3 cells expressing the G protein-coupled muscarinic acetylcholine receptor, carbachol activated phospholipase C and induced secretion without concomitant pp72 phosphorylation. Therefore, pp72 phosphorylation was not induced by G protein activation or as a consequence of phosphatidylinositol hydrolysis. To investigate whether pp72 tyrosine phosphorylation precedes the activation of phospholipase C, we studied the effect of the tyrosine kinase inhibitor genistein. Preincubation of cells with genistein decreased, in parallel, antigen-induced tyrosine phosphorylation of pp72 (IC50 = 34 micrograms/ml) and histamine release (IC50 = 31 micrograms/ml). However, genistein at concentrations of up to 60 micrograms/ml did not inhibit phosphatidylinositol hydrolysis nor did it change the amount of the secondary messenger inositol (1,4,5)-triphosphate. Previous observations showed that there was no pp72 tyrosine phosphorylation after activation of protein kinase C or after an increase in intracellular calcium. Taken together, these results suggest that pp72 tyrosine phosphorylation represents a distinct, independent signaling pathway induced specifically by aggregation of the Fc epsilon RI.
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PMID:Fc epsilon RI-induced protein tyrosine phosphorylation of pp72 in rat basophilic leukemia cells (RBL-2H3). Evidence for a novel signal transduction pathway unrelated to G protein activation and phosphatidylinositol hydrolysis. 137 2


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