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)

The c-kit gene, mapped to the dominant white spotting (W) locus of the mouse (Chabot, B., Stephenson, D. A., Chapman, V. M., Besmer, P., and Bernstein, A. (1988) Nature 335, 88-89; Geissler, E. N., Ryan, M. A., and Housman, D. E. (1988) Cell 55, 185-192), encodes a receptor tyrosine kinase, p145c-kit. Germline mutations at the W locus lead to loss of function alterations in p145c-kit, and result in mice with developmental defects of varying severity in the melanocytic, hematopoietic stem cell, and primordial germ cell lineages. To investigate in more detail the effect of W mutations on p145c-kit signaling, three mutations, W42, Wv, and W41, that confer severe, intermediate, and mild phenotypic characteristics, respectively, were introduced into the human p145c-kit tyrosine kinase domain. These mutations attenuated the intrinsic tyrosine kinase activity of the receptor to different degrees. In addition, they had differential effects on the interaction of the p145c-kit substrates, phospholipase C gamma, GTPase-activating protein, and the receptor-binding subunit of phosphatidylinositol 3'-kinase, p85. Notably, the Wv mutation, while retaining significant receptor tyrosine kinase activity, was unable to bind phospholipase C gamma and GTPase-activating protein, but could still associate with p85. These results suggest that the location of W mutations may be an important determinant of the specificity of substrate association and phosphorylation, and may explain, at least in part, the cell type-specific defects associated with certain W alleles.
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PMID:Differential effects of W mutations on p145c-kit tyrosine kinase activity and substrate interaction. 137 79

The kit protooncogene encodes a transmembrane tyrosine kinase related to the receptors for the platelet derived growth factor (PDGF-R) and the macrophage growth factor (CSF1-R), and was very recently shown to bind a stem cell factor. To compare signal transduction by the kit kinase with signaling by homologous receptors we constructed a chimeric protein composed of the extracellular domain of the epidermal growth factor receptor (EGF-R) and the transmembrane and cytoplasmic domains of kit. We have previously shown that the chimeric receptor transmits potent mitogenic and transforming signals in response to the heterologous ligand. Here we demonstrate that upon ligand binding, the ligand-receptor complex undergoes endocytosis and degradation and induces short- and long-term cellular effects. Examination of the signal transduction pathway revealed that the activated kit kinase strongly associates with phosphatidylinositol 3'-kinase activity and a phosphoprotein of 85 kd. In addition, the ligand-stimulated kit kinase is coupled to modifications of phospholipase C gamma and the Raf1 protein kinase. However, it does not lead to a significant change in the production of inositol phosphate. Comparison of our results with the known signaling pathways of PDGF-R and CSF1-R suggests that each receptor is coupled to a specific combination of signal transducers.
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PMID:A specific combination of substrates is involved in signal transduction by the kit-encoded receptor. 170 85

The chimeric EK-receptor (EK-R), consisting of the epidermal growth factor receptor (EGF-R) extracellular binding domain and p145c-kit cytoplasmic signal-generating sequences, was fully functional in forming high and low affinity EGF binding sites and in ligand-regulated receptor and substrate phosphorylation activities. Relative to EGF-R, EK-R activation stimulated kit-characteristic phosphorylation of human 293 fibroblast substrate polypeptides. Transient coexpression of EK-R with candidate substrates resulted in ligand-induced phosphorylation of phospholipase C gamma and guanosine triphosphatase-activating polypeptide. The RAF-1 serine/threonine kinase was shown to be associated with activated EK-R, but no tyrosine phosphorylation could be detected. The faithfulness of EK-R substrate phosphorylation specificity was confirmed with stem cell factor-stimulated p145c-kit.
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PMID:Substrate phosphorylation specificity of the human c-kit receptor tyrosine kinase. 171 57

Platelet-derived growth factor (PDGF) is a 30 kDa dimer of disulfide-bonded A and B chains. Three isoforms of PDGF have been isolated (PDGF-AA, PDGF-AB and PDGF-BB). These bind with different affinities and specificities to two structurally related cell surface receptors, viz. the alpha-receptor and the beta-receptor. The receptors are transmembrane proteins with an intracellular, ligand-stimulatable protein tyrosine kinase domain. Activation of the receptors is intimately associated with receptor dimerization, and available data suggest that PDGF is a divalent ligand such that one molecule of PDGF binds and dimerizes two receptor molecules. Stimulation of PDGF receptors leads to a cascade of cellular events, which have been shown to require an intact receptor tyrosine kinase activity. However, ligand-induced internalization and degradation of the beta-receptor occur essentially independent of the receptor kinase activity. Receptor activation leads to the phosphorylation on tyrosine residues of three enzymes, probably by direct phosphorylation: phospholipase C-gamma, phosphatidylinositol 3' kinase and Raf-1. In certain cells, PDGF beta-receptor expression is inducible such that cells in normal tissue in vivo do not express receptors; only in inflammatory lesions or when cells are explanted in vitro, are receptors being expressed. Transformation by the v-sis oncogene is mediated by an autocrine PDGF-like growth factor. Although both the alpha- and beta-receptors are structurally related to the v-fms and v-kit oncogenes, it is not known if the PDGF receptors have a transforming potential. In conclusion, the finding of three isoforms of PDGF that interact with two structurally related receptors implies a finely tuned regulatory network, the role of which in cell growth and transformation remains to be clarified.
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PMID:Structural and functional aspects of the receptors for platelet-derived growth factor. 256 60

Cellular growth and differentiation signals are generated and defined by the interaction of specific phosphotyrosine residues of activated receptor tyrosine kinases (RTKs) and src homology-2 (SH2) domain-containing intracellular signal transducers. This appears to involve for both the p145c-kit and beta platelet-derived growth factor receptor (PDGF-R) cytoplasmic domains the formation of multiprotein signal transfer complexes, which include combinations of noncatalytic and enzymatically active subunits of phosphatidylinositol 3'-kinase (PI3'-K), phospholipase C-gamma (PLC gamma), and guanosine trisphosphatase activating protein (GAP). In vitro association experiments indicate that PLC gamma and PI3'-K bind the beta PDGF-R simultaneously, while these two SH2 proteins compete for association to p145c-kit binding sites, with p85/PI3'-K exhibiting higher affinity. Interestingly, GAP and p85/PI3'-K binding to distinct p145c-kit phosphotyrosines is cooperative, enhancing formation of a heterotetrameric signaling complex, which may include different combinations of p85 alpha and p85 beta with p110, p112, and p116 by interaction with the same tyrosine 721 docking site. The diversity of molecular interactions observed for PDGF-R and p145c-kit suggests a new mode of signal definition and modulation.
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PMID:Formation of signal transfer complexes between stem cell and platelet-derived growth factor receptors and SH2 domain proteins in vitro. 753 96

A truncated form of the c-kit tyrosine kinase receptor, corresponding to the phosphotransferase portion of the cytoplasmic catalytic domain and the carboxyterminus (tr-kit), is accumulated during late mouse spermiogenesis. Here we report that tr-kit is specifically localized in the residual sperm cytoplasm, with maximal accumulation in the midpiece of the flagellum, suggesting that it can enter the egg during fertilization. Microinjection of extracts from COS cells expressing a recombinant tr-kit protein into metaphase II-arrested mouse oocytes caused complete oocyte activation, including cortical granule exocytosis, completion of the 2nd meiotic division, formation of a parthenogenetic pronucleus and progression through cleavage stages. No activation above background levels was obtained with extracts from mock-transfected COS cells. Similar results were obtained by microinjection of in vitro synthesized tr-kit mRNA into metaphase II-arrested oocytes. Tr-kit-induced parthenogenetic egg activation was completely inhibited by oocyte preincubation with the Ca2(+)-chelating agent BAPTA-AM or with a specific inhibitor of phospholipase C activity. Tr-kit-induced egg activation was associated with a decrease in activity of mitogen-activated protein kinase, an essential component of the cytostatic factor. These results candidate tr-kit as a putative sperm factor required for triggering activation of mouse eggs at fertilization.
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PMID:Parthenogenetic activation of mouse eggs by microinjection of a truncated c-kit tyrosine kinase present in spermatozoa. 918 52

Microinjection of a truncated form of the c-kit tyrosine kinase present in mouse spermatozoa (tr-kit) activates mouse eggs parthenogenetically, and tr-kit- induced egg activation is inhibited by preincubation with an inhibitor of phospholipase C (PLC) (Sette, C., A. Bevilacqua, A. Bianchini, F. Mangia, R. Geremia, and P. Rossi. 1997. Development [Camb.]. 124:2267-2274). Co-injection of glutathione-S-transferase (GST) fusion proteins containing the src-homology (SH) domains of the gamma1 isoform of PLC (PLCgamma1) competitively inhibits tr-kit- induced egg activation. A GST fusion protein containing the SH3 domain of PLCgamma1 inhibits egg activation as efficiently as the whole SH region, while a GST fusion protein containing the two SH2 domains is much less effective. A GST fusion protein containing the SH3 domain of the Grb2 adaptor protein does not inhibit tr-kit-induced egg activation, showing that the effect of the SH3 domain of PLCgamma1 is specific. Tr-kit-induced egg activation is also suppressed by co-injection of antibodies raised against the PLCgamma1 SH domains, but not against the PLCgamma1 COOH-terminal region. In transfected COS cells, coexpression of PLCgamma1 and tr-kit increases diacylglycerol and inositol phosphate production, and the phosphotyrosine content of PLCgamma1 with respect to cells expressing PLCgamma1 alone. These data indicate that tr-kit activates PLCgamma1, and that the SH3 domain of PLCgamma1 is essential for tr-kit-induced egg activation.
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PMID:Involvement of phospholipase Cgamma1 in mouse egg activation induced by a truncated form of the C-kit tyrosine kinase present in spermatozoa. 972 17

A multiplex polymerase chain reaction (PCR) assay, developed to detect the alpha-toxin and enterotoxin genes (cpa and cpe, respectively) of Clostridium perfringens, was used to identify enterotoxigenic isolates of this organism from feces and intestinal contents of pigs and from feed samples from pig farms in Iowa. The organism was grown on tryptose-sulfite-cycloserine (TSC) agar, TSC agar without egg-yolk, sheep blood agar, or in brain heart infusion broth or cooked meat medium. DNA was extracted by boiling and the PCR assay was carried out using reagents from a commercial kit. The 319 bp amplification product of cpa and the 364 bp product of cpe were visualized under UV light after electrophoresis in a 2% agarose gel containing ethidium bromide. The average sensitivity of the assay, determined on artificially contaminated feces, was 9.2 x 10(4) colony forming units per gram. Assay of 97 isolates from feces and intestinal contents revealed cpa in 89, but all were negative for cpe. While 28% of the 442 total samples cultured yielded C. perfringens, only 5% of 298 fecal or intestinal contents samples were positive upon direct examination by the PCR assay. Ninety-one and eight-tenths % of isolates with the phenotype of C. perfringens were cpa positive by PCR. Forty-three percent of feed samples were culture positive, while 48.3% were PCR positive for cpa. None of these were cpe positive. We conclude that PCR is a useful assay for rapid detection of C. perfringens in feed, and for confirmation of the identity of isolates presumed to be C. perfringens.
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PMID:Multiplex PCR assay for detection of Clostridium perfringens in feces and intestinal contents of pigs and in swine feed. 981 Jun 19

Very little is known about the occurrence of Clostridium perfringens and of diseases caused by this anaerobic bacterium in marine mammals, especially those that are free-living. During a scientific expedition to the Greenland Sea (West Ice) in spring 1999, faeces samples from 70 hooded seals (Cystophora cristata) were taken to isolate C. perfiringens. Subsequently, PCR analysis of the isolates was performed with oligonucleotide primers of the genes encoding the four major lethal toxins (alpha, beta, epsilon and iota) for classification of toxin type and of the genes encoding C. perfringens beta2-toxin and enterotoxin for further subclassification. In addition, a commercial ELISA kit for detection of C. perfringens alpha, beta- and epsilon-toxin was used. C. perfingens was isolated in samples from 38 (54.3%) hooded seals. All isolates were C. perfringens toxin type A (alpha-toxin positive). This is the first report on the occurrence of C. perfringens in this arctic marine mammal species. Myositis and enterotoxemia caused by C. perfrigens were described in other marine mammals and it may be assumed that the pathogenesis of an outbreak of disease is similar to that encountered in terrestrial animals. Although there is some controversy surrounding the enteropathogenicity and virulence of alpha-toxin (concerning enterotoxemia), this study suggests that a possible outbreak of enterotoxemia caused by C. perfringens type A in hooded seals may, however, not be excluded.
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PMID:Clostridium perfringens toxin types in hooded seals in the Greenland Sea, determined by PCR and ELISA. 1184 22

A molecular method based on restriction fragment length polymorphism (RFLP) of PCR-amplified fragments of the 23S rRNA gene was designed to rapidly identify Listeria strains to the species level. Two fragments (S1, 460 bp, and S2, 890 bp) were amplified from boiled DNA. S2 was cut with the restriction enzymes XmnI or CfoI and, if needed, S1 was digested by either AluI or ClaI. This method was first optimized with six reference strains and then applied to 182 isolates collected from effluents of treatment plants. All isolates were also identified by the API Listeria kit, hemolysis, and phosphatidylinositol-specific phospholipase C production (PI-PLC) on ALOA medium. The PCR-RFLP method unambiguously identified 160 environmental strains, including 131 in concordance with the API system, and revealed that 22 isolates were mixed cultures of Listeria monocytogenes and Listeria innocua. Discrepant results were resolved by a multiplex PCR on the iap gene, which confirmed the PCR-RFLP data for 49 of the 51 discordances, including the 22 mixed cultures. Sequencing of the 16S rRNA gene for 12 selected strains and reconstruction of a phylogenetic tree validated the molecular methods, except for two unclassifiable strains. The 158 single identifiable isolates were 92 L. monocytogenes (including seven nonhemolytic and PI-PLC-negative strains), 61 L. innocua, 4 Listeria seeligeri, and 1 Listeria welshimeri strain. The PCR-RFLP method proposed here provides rapid, easy-to-use, inexpensive, and reliable identification of the six Listeria species. Moreover, it can detect mixtures of Listeria species and thus is particularly adapted to environmental and food microbiology.
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PMID:Rapid identification of Listeria species by using restriction fragment length polymorphism of PCR-amplified 23S rRNA gene fragments. 1460 90


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