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 the course of our investigation of phospholipase C (PLC)-gamma 1 phosphorylation by using a set of anti-PLC-gamma 1 monoclonal antibodies (P.-G. Suh, S. H. Ryu, W. C. Choi, K.-Y. Lee, and S. G. Rhee, J. Biol. Chem. 263:14497-14504, 1988), we found that some of these antibodies directly recognize a 47-kDa protein. We show here that this 47-kDa protein is identical to the SH2/SH3-containing protein Nck (J. M. Lehmann, G. Riethmuller, and J. P. Johnson, Nucleic Acids Res. 18:1048, 1990). Nck was found to be constitutively phosphorylated on serine in resting NIH 3T3 cells. Platelet-derived growth factor (PDGF) treatment led to increased Nck phosphorylation on both tyrosine and serine. Nck was also found to be phosphorylated on tyrosine in epidermal growth factor (EGF)-treated A431 cells and in v-Src-transformed NIH 3T3 cells. Multiple sites of serine phosphorylation were detected in Nck from resting cells, and no novel sites were found upon PDGF or EGF treatment. A single major tyrosine phosphorylation site was found in Nck in both PDGF- and EGF-treated cells and in v-Src-transformed cells. This same tyrosine was phosphorylated in vitro by purified PDGF and EGF receptors and also by pp60c-src. We compared the phosphorylation of Nck and PLC-gamma 1 in several cell lines transformed by oncogenes with different modes of transformation. Although PLC-gamma 1 and Nck have significant amino acid identity, particularly in their SH3 regions, and both associate with growth factor receptors in a ligand-dependent manner, they were not always phosphorylated on tyrosine in a coincident manner.
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PMID:The SH2/SH3 domain-containing protein Nck is recognized by certain anti-phospholipase C-gamma 1 monoclonal antibodies, and its phosphorylation on tyrosine is stimulated by platelet-derived growth factor and epidermal growth factor treatment. 144 8

Activation of receptor-linked and cytoplasmic protein tyrosine kinases is crucial in the control of normal and abnormal cell growth and differentiation. Some substrates of protein tyrosine kinases such as phospholipase C gamma and ras GTPase-activating protein (GAP) contain sequences homologous to the src protein domains SH2 and SH3 (refs 3-9). The proto-oncogene vav is expressed in haematopoietic cells and its product Vav contains sequence motifs commonly found in transcription factors, such as helix-loop-helix, leucine-zipper and zinc-finger motifs and nuclear localization signals, as well as a single SH2 and two SH3 domains. Here we show that stimulation of T-cell antigen receptor on normal human peripheral blood lymphocytes or on human leukaemic T cells, and the crosslinking of IgE receptors on rat basophilic leukaemia cells, both promote the phosphorylation of tyrosine residues in Vav. Moreover, activation of the receptor for epidermal growth factor leads to marked tyrosine phosphorylation of Vav in cells transiently expressing vav, and Vav associates with the receptor through its SH2 domain. We propose that vav encodes a new class of substrates whose tyrosine phosphorylation may provide a mechanism for direct signal transduction linking receptors at the cell surface to transcriptional control.
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PMID:Tyrosine phosphorylation of vav proto-oncogene product containing SH2 domain and transcription factor motifs. 161 45

Several cytoplasmic tyrosine kinases contain a conserved, non-catalytic stretch of approximately 100 amino acids called the src homology 2 (SH2) domain, and a region of approximately 50 amino acids called the SH3 domain. SH2/SH3 domains are also found in several other proteins, including phospholipase C-gamma (PLC gamma). Recent studies indicate that SH2 domains promote association between autophosphorylated growth factor receptors such as the epidermal growth factor (EGF) receptor and signal transducing molecules such as PLC gamma. Because SH2 domains bind specifically to protein sequences containing phosphotyrosine, we examined their capacity to prevent tyrosine dephosphorylation of the EGF and other receptors with tyrosine kinase activity. For this purpose, various SH2/SH3 constructs of PLC gamma were expressed in Escherichia coli as glutathione-S-transferase fusion proteins. Our results show that purified SH2 domains of PLC gamma are able to prevent tyrosine dephosphorylation of the EGF receptor and other receptors with tyrosine activity. The inhibition of tyrosine dephosphorylation paralleled the capacity of various SH2-containing constructs to bind to the EGF receptor, suggesting that the tyrosine phosphatase and the SH2 domain compete for the same tyrosine phosphorylation sites in the carboxy-terminal tail of the EGF receptor. Analysis of the phosphorylation sites protected from dephosphorylation by PLC gamma-SH2 revealed substantial inhibition of dephosphorylation of Tyr992 at 1 microM SH2. This indicates that Tyr992 and its flanking sequence is the high-affinity binding site for SH2 domains of PLC gamma.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:SH2 domains prevent tyrosine dephosphorylation of the EGF receptor: identification of Tyr992 as the high-affinity binding site for SH2 domains of phospholipase C gamma. 153 35

The growth of many normal cells requires contact with an adhesive substratum, a requirement that is frequently abrogated in the transformed phenotype. We have explored pathways that can lead to the anchorage-independent growth of cultured Rat-1 fibroblasts. Pasteurella multocida toxin (PMT), a 146-kDa mitogenic protein, caused a striking increase in the formation of colonies (greater than 200 microns) from single cells in soft agar. The magnitude of the effect of PMT was greater than that achieved by epidermal growth factor or platelet-derived growth factor. The toxin was extremely potent, with half-maximal and maximal effects observed at 1 and 10 pM PMT, respectively. This concentration dependence of the action of the toxin is similar to that for the stimulation of DNA synthesis in adherent cultures of the cells. Stimulation of colony formation could be achieved by a transient exposure of the cells to PMT and it was blocked by methylamine, indicating that the toxin enters the cells to act. Colony formation was stimulated equally by native and recombinant PMT, but a truncated version (33.5 kDa) of the recombinant toxin was ineffective. PMT antiserum blocked colony formation in response to PMT. In the Rat-1 cells, PMT stimulated the phospholipase C-mediated hydrolysis of inositolphospholipids, as indicated by the stimulation of inositol phosphate release, Ca2+ mobilization, and phosphorylation of a protein kinase C substrate. The results indicate that the deregulation of signal-transduction pathways as elicited by an intracellularly acting bacterial toxin can induce a malignant phenotype.
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PMID:Pasteurella multocida toxin is a potent inducer of anchorage-independent cell growth. 158 59

Chronic injections of epidermal growth factor (EGF) or the beta-adrenergic receptor agonist isoprenaline resulted in rat parotid gland hypertrophy and hyperplasia. Introduction of a polyclonal antibody to EGF or the EGF-receptor (EGF-R) caused a specific retardation of acinar cell proliferation when injected along with the growth factor. Meanwhile, only the antibody to EGF-R caused a dose-dependent retardation of proliferation on co-administration with isoprenaline both in vivo and in vitro. The antibody injected alone had no effect on cell growth. When cells were incubated in the presence of EGF, plasma membranes from isoprenaline-treated and control animals showed phosphorylation of the EGF-R tyrosine moieties and transient increases in membrane-associated phospholipase C gamma. Isoprenaline did not stimulate phosphorylation of the EGF-R in isolated plasma membranes. However, activation of the phosphotyrosine-signalling pathway could be duplicated by incubating isoprenaline-treated acinar cells, but not control cells, with bovine galactosyltransferase. Immunopurified EGF-R demonstrated variations in reactivity with two different lectins after treatment of the cells with the beta-agonist as well as increased galactosyltransferase substrate capacity in vitro. In addition, incubation of intact acinar cells and isolated plasma-membrane fractions from isoprenaline-treated rats with UDP-[14C]galactose resulted in an increased incorporation of label into the EGF-R. The results suggest that the carbohydrate moiety of the EGF-R has been altered in isoprenaline-treated animals allowing galactosyltransferase now to recognize this receptor. This interaction may in part mediate proliferation of parotid acinar cells. Indeed, we have previously shown that an antibody to galactosyltransferase is capable of blocking isoprenaline-mediated acinar cell proliferation in vivo [Humphreys-Beher, Schneyer, Kidd & Marchase (1987) J. Biol. Chem. 262, 11706-11713].
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PMID:A novel mechanism for isoprenaline-stimulated proliferation of rat parotid acinar cells involving the epidermal growth factor receptor and cell surface galactosyltransferase. 162 94

Lithium interferes with the responses of neural and secretory cells to calcium-mobilizing agonists by blocking the generation of phospholipase C-dependent second messengers. However, the mechanism by which lithium stimulates the proliferation of other cells in response to agonists that do not activate phospholipase C remains obscure. We investigated the pathways that mediate the mitogenic action of lithium on WI-38 cells in a defined, serum-free medium. Lithium, like dexamethasone (Dex), potentiated DNA synthesis in response to the combination of insulin+epidermal growth factor (EGF) (+50%), but not in response to either growth factor alone or with Dex. As in the case of Dex, lithium could be added as late as 8 h following stimulation of quiescent cells by insulin+EGF without loss of potentiating activity. While DNA synthesis in control cultures was essentially complete by 24 h, lithium and Dex stimulated "late" DNA synthesis (24-30 h) 10-fold and 5-fold, respectively. The potentiating activity of Dex, but not that of lithium, was blocked by the specific glucocorticoid receptor antagonist, RU486. Both lithium and Dex stimulated log-phase growth, but only Dex increased saturation density. These data indicate that both lithium and Dex recruit into the cell cycle a subpopulation of cells with a longer mean prereplicative phase (G1). The effect of lithium on DNA synthesis in WI-38 cells may be mediated by the glucocorticoid response pathway at some point distal to activation of the glucocorticoid receptor, or by an independent mechanism that can be switched on late in G1.
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PMID:Lithium mimics dexamethasone in stimulating DNA synthesis by WI-38 cells. 163 35

Activation of epidermal growth factor (EGF) receptors stimulates inositol phosphate production in rat hepatocytes via a pertussis toxin-sensitive mechanism, suggesting the involvement of a G protein in the process. Since the first event after receptor-G protein interaction is exchange of GTP for GDP on the G protein, the effect of EGF was measured on the initial rates of guanosine 5'-O-(3-[35S]thiotriphosphate) [( 35S]GTP gamma S) association and [alpha-32P]GDP dissociation in rat hepatocyte membranes. The initial rate of [35S]GTP gamma S binding was stimulated by EGF, with a maximal effect observed at 8 nM EGF. EGF also increased the initial rate of [alpha-32P]GDP dissociation. The effect of EGF on [35S]GTP gamma S association was blocked by boiling the peptide for 5 min in 5 mM dithiothreitol or by incubation of the membranes with guanosine 5'-O-(2-thiodiphosphate) (GDP beta S). EGF-stimulated [35S]GTP gamma S binding was completely abolished in hepatocyte membranes prepared from pertussis toxin-treated rats and was inhibited in hepatocyte membranes that were treated directly with the resolved A-subunit of pertussis toxin. The amount of guanine nucleotide binding affected by occupation of the EGF receptor was approximately 6 pmol/mg of membrane protein. Occupation of angiotensin II receptors, which are known to couple to G proteins in hepatic membranes, also stimulated [35S]GTP gamma S association with and [alpha-32P]GDP dissociation from the membranes. The effect of angiotensin II on [alpha-32P]GDP dissociation was blocked by the angiotensin II receptor antagonist [Sar1,Ile8]angiotensin II, demonstrating that the guanine nucleotide binding was receptor-mediated. In A431 human epidermoid carcinoma cells, EGF stimulates inositol lipid breakdown, but the effect is not blocked by treatment of the cells with pertussis toxin. In these cells, EGF had no effect on [35S]GTP gamma S binding. Occupation of the beta-adrenergic receptor in A431 cell membranes with isoproterenol did stimulate [35S] GTP gamma S binding, and the effect could be completely blocked by l-propranolol. These results support the concept that in hepatocyte membranes, EGF receptors interact with a pertussis toxin-sensitive G protein via a mechanism similar to other hormone receptor-G protein interactions, but that in A431 human epidermoid carcinoma cells, EGF may activate phospholipase C via different mechanisms.
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PMID:The epidermal growth factor receptor is coupled to a pertussis toxin-sensitive guanine nucleotide regulatory protein in rat hepatocytes. 164 88

Treatment of rat hepatocytes with epidermal growth factor (EGF) produced an enhanced tyrosine phosphorylation of the EGF receptor and phospholipase C-gamma (PLC-gamma) in conjunction with the mobilization of Ca2+. Approximately 30% of the total PLC-gamma was tyrosine-phosphorylated with a maximum being reached after 30 s of incubation with EGF. Pretreatment of the rats with pertussis toxin prior to isolation of the hepatocytes blocked EGF-induced tyrosine phosphorylation of PLC-gamma and Ca2+ mobilization but had no effect on autophosphorylation of the EGF receptor or Ca2+ responses elicited by angiotensin II or phenylephrine. Under these conditions Gi protein alpha subunits were fully ADP-ribosylated. A 41-kDa Gi protein alpha subunit was found to be present in the anti-PLC-gamma immune complex after EGF stimulation as shown by in vitro ADP-ribosylation using [32P]NAD+ and activated pertussis toxin. The kinetics of association between PLC-gamma with Gi alpha protein reached a maximum after 1 min of incubation with EGF. Antibodies specific for the EGF receptor also coimmunoprecipitated a Gi protein alpha subunit. Treatment of hepatocytes with EGF caused first an increase and then a decrease in the amount of Gi protein alpha subunit associated with the EGF receptor. In contrast, studies with cultured rat liver (WB) cells, a cell line in which EGF stimulation of phosphoinositide hydrolysis is not inhibited by pertussis toxin, showed that a stable complex of Gi alpha was not formed with either PLC-gamma or EGF receptor immunoprecipitates. These results indicate that a pertussis toxin-sensitive Gi protein is uniquely involved in the signal transduction pathway mediating EGF-induced activation of PLC-gamma and Ca2+ mobilization in hepatocytes.
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PMID:Pertussis toxin-sensitive Gi protein involvement in epidermal growth factor-induced activation of phospholipase C-gamma in rat hepatocytes. 165 96

The erbB-2 gene product, gp185erbB-2, unlike the structurally related epidermal growth factor (EGF) receptor (EGFR), exhibits constitutive kinase and transforming activity. We used a chimeric EGFR/erbB-2 expression vector to compare the mitogenic signaling pathway of the erbB-2 kinase with that of the EGFR, at similar levels of expression, in response to EGF stimulation. The EGFR/erbB-2 chimera was significantly more active in inducing DNA synthesis than the EGFR when either was expressed in NIH 3T3 cells. Analysis of biochemical pathways implicated in signal transduction by growth factor receptors indicated that both phospholipase C type gamma (PLC-gamma) and the p21ras GTPase-activating protein (GAP) are substrates for the erbB-2 kinase in NIH 3T3 fibroblasts. However, under conditions in which activation of the erbB-2 kinase induced DNA synthesis at least fivefold more efficiently than the EGFR, the levels of erbB-2- or EGFR-induced tyrosine phosphorylation of PLC-gamma and GAP were comparable. In addition, the stoichiometry of tyrosine phosphorylation of these putative substrates by erbB-2 appeared to be at least an order of magnitude lower than that induced by platelet-derived growth factor receptors at comparable levels of mitogenic potency. Thus, our results indicate that differences in tyrosine phosphorylation of PLC-gamma and GAP do not account for the differences in mitogenic activity of the erbB-2 kinase compared with either the EGFR or platelet-derived growth factor receptor in NIH 3T3 fibroblasts.
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PMID:The erbB-2 mitogenic signaling pathway: tyrosine phosphorylation of phospholipase C-gamma and GTPase-activating protein does not correlate with erbB-2 mitogenic potency. 167 40

We have identified the sites phosphorylated in vitro by epidermal growth factor (EGF) receptor kinase in bovine brain phospholipase C-gamma (PLC-gamma). They are tyrosine residues 472, 771, 783, and 1254. The rate of phosphorylation was fastest with the sites at 771 and 783, then at 1254, and slowest at 472. PLC-gamma isolated from cells treated with EGF is known to contain at least four tyrosine phosphate-containing peptides and two of them are identified to be residues 771 and 1254 in the accompanying paper (Wahl, M. I., Nishibe, S., Kim, J. W., Kim, H., Rhee, S. G., and Carpenter, G. (1990) J. Biol. Chem. 265, 3944-3948). The 3 residues 472, 771, and 783 are located closely to the regions of PLC-gamma which exhibit a high sequence similarity to the regulatory domain of the src family tyrosine kinases. Nevertheless, the tyrosine phosphorylation did not affect the catalytic activity of PLC-gamma in vitro. We propose, therefore, that the phosphorylation of PLC-gamma by EGF receptor kinase alters its interaction with putative inhibitory proteins and leads to its activation.
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PMID:Tyrosine residues in bovine phospholipase C-gamma phosphorylated by the epidermal growth factor receptor in vitro. 168 10


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