Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

When washed human platelets were disrupted by sonication in the presence of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, both the catalytic and [3H]phorbol-12,13-dibutyrate (PDBu)-binding activities of protein kinase C were recovered in the soluble fraction and were not separable from each other upon several column chromatographies. Platelet protein kinase C required diacylglycerol, Ca2+, and phospholipid for its activation and showed a molecular weight of about 87,000 as estimated by gel filtration analysis. However, when platelets were first incubated with 2 microM Ca2+-ionophore A23187 for 5 min at 37 degrees C in the medium containing 3 mM CaCl2 and then disrupted under the same conditions, the catalytic and [3H]phorbol-12,13-dibutyrate-binding activities were separately recovered in the soluble and particulate fractions, respectively; moreover, the catalytic activity recovered in the soluble fraction became independent of diacylglycerol, Ca2+, and phospholipid, and showed a molecular weight of about 50,000 as estimated by gel filtration analysis. The kinetic properties of this Mr 50,000 enzyme were similar to those of the catalytic fragment of rat brain protein kinase C described previously. In a cell-free system, digestion with trypsin of protein kinase C highly purified from rat brain caused the generation of a fragment which had no catalytic activity but showed full [3H]phorbol-12,13-dibutyrate-binding activity. The molecular weight of this fragment was estimated to be about 35,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results indicate that protein kinase C consists of at least two functionally different domains, a hydrophobic phorbol ester- or diacylglycerol-binding and hydrophilic catalytic domains.
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PMID:Formation of a phorbol ester-binding fragment from protein kinase C by proteolytic digestion. 308 81

In order to identify cDNAs that can induce oncogenic transformation, a retroviral vector was used to transfer a library of cDNAs from the murine 32D hemopoietic cell line into NIH 3T3 fibroblasts. We have identified and recovered a provirus containing a 1.8-kilobase pair cDNA whose expression causes morphological transformation in NIH 3T3 cells. The transforming cDNA contains a complete open reading frame that encodes a protein (designated Lfc) with a region of sequence similarity to the product of the lbc oncogene. This region includes a domain that is characteristic of the CDC24 family of guanine nucleotide exchange factors in tandem with a pleckstrin homology (PH) domain. The Lfc protein is distinguished from Lbc by a 150-amino acid NH2-terminal extension that contains a cysteine- and histidine-rich domain similar to the diacylglycerol-binding site (zinc butterfly) found in protein kinase C. NH2- and COOH-terminal deletion analysis revealed that both the PH and putative guanine nucleotide exchange factor domains are required, but the zinc butterfly is dispensable, for transformation. Although the removal of the PH domain of the Lfc protein completely eliminated its ability to transform NIH 3T3 cells, replacement of this domain with an isoprenylation site restored all of its transforming activity. This suggests that a PH domain-dependent recruitment of the Lfc protein to the cellular membrane is a necessary step for cellular transformation. The lfc gene is expressed in a broad range of tissues as well as in a variety of hemopoietic and non-hemopoietic cell lines. Lfc appears to be a new member of a growing family of proteins that are likely to act as activators of Ras-like proteins in a developmental or cell-lineage specific manner.
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PMID:Expression cloning of lfc, a novel oncogene with structural similarities to guanine nucleotide exchange factors and to the regulatory region of protein kinase C. 762 63

We have analyzed the structure of the active site of monogalactosyldiacylglycerol (MGDG) synthase from spinach chloroplast envelope. Since purification of this membrane-embedded enzyme yielded such low amounts of protein that analyses of the amino acid sequence were so far impossible, we used indirect strategies. Analyses of the inhibition of MGDG synthase by UDP and of its inactivation by citraconic anhydride first indicated that the enzyme contained two functionally independent and topologically distinct binding sites for each substrate. Whereas MGDG synthase binds both the nucleotidic part of UDP-Gal and the acyl chains of 1,2-diacylglycerol, UDP is a competitive inhibitor relatively to UDP-Gal, while it does not compete with 1,2-diacylglycerol for binding on the enzyme. The UDP-Gal-binding site contains lysine residues, as demonstrated for UDP-Gal-binding sites from all galactosyltransferases studied so far. Radiolabeling of MGDG synthase by sulfur labeling reagent, a 35S-labeled lysine-blocking reagent, confirmed that MGDG synthase was a polypeptide with a low molecular mass (around 20 kDa). The 1,2-diacylglycerol-binding site contains reduced cysteines and at least one metal. The divalent cation(s) associated to apo-MGDG synthase was not unambiguously identified, but the results suggest that it could be zinc. Therefore, MGDG synthase presents some structural features in common with diacylglycerol-manipulating enzymes, such as protein kinase C and 1,2-diacylglycerol kinase, which are characterized by the presence of a ubiquitous Cys6His2 domain involved in zinc coordination in their 1,2-diacylglycerol-binding domains.
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PMID:The catalytic site of monogalactosyldiacylglycerol synthase from spinach chloroplast envelope membranes. Biochemical analysis of the structure and of the metal content. 789 Jun 98

Association of calcium-dependent isotypes of protein kinase C (PKC) with a phospholipid bilayer is regulated by a single Ca(2+)-binding site. The dependence of PKC association with phosphatidylserine-containing membranes on the concentration of Ca2+ is linear in the submicro- to submillimolar range. The Ca(2+)-regulated association of PKC with the membrane is sensitive to the factors that alter the diffuse double-layer potential produced by anionic lipids such as phosphatidylserine (PS). This indicates that the Ca(2+)-binding site on the membrane-bound enzyme senses a higher concentration of Ca2+ than is present in bulk solution. This is a consequence of the accumulation of Ca2+ in the layer adjacent to the plane of the membrane by the double-layer potential. Calculations based on the Gouy-Chapman-Stern theory of the diffuse double layer yielded a unique value of the Ca2+ dissociation constant for the Ca(2+)-PKC-bilayer complex equal to approximately 700 nM. The soluble form of the enzyme has a 3.5 order of magnitude lower affinity for Ca2+. The free energy of interaction between the Ca(2+)- and PS-binding sites is large (approximately 5 kcal/mol). In contrast, the interaction between the diacylglycerol-binding site and either the Ca(2+)- or PS-binding site appears to be weak.
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PMID:Characterization of the calcium-binding site that regulates association of protein kinase C with phospholipid bilayers. 818 56

We investigated the hypothesis that tumor necrosis factor-alpha (TNF) activates pulmonary endothelial protein kinase C (PKC). Confluent bovine pulmonary artery endothelial monolayers were exposed to recombinant human TNF, and the translocation of PKC, an indicator of enzyme activation, was studied using both slot immunoblotting and immunofluorescence. For slot immunoblot analysis, membrane and cytosol lysate fractions were prepared, and PKC antigen was assessed using MC5 monoclonal anti-PKC antibody. TNF (1,000 U/ml for 15 min) induced translocation of PKC into the membrane. Immunofluorescence analysis with the MC5 antibody was also used. Monolayers treated with culture medium showed diffuse cytoplasmic fluorescence. In contrast, treatment with either TNF (1,000 U/ml for 15 min) or 1,2-dioctanoylglycerol (4 x 10(-5) M for 5 min), a diacylglycerol that activates PKC, resulted in translocation of fluorescence to the cell periphery; fine, punctate PKC-associated fluorescence was localized to the margins of cells. The TNF-induced translocation of PKC was inhibited using either IP-300 polyclonal anti-TNF antibody (indicating that the TNF effect was not due to the vehicle or contaminating endotoxin) or calphostin C (10(-6) M for 15 min), which inhibits PKC activation by interacting with the regulatory diacylglycerol-binding domain. TNF treatment had no effect on either the content of PKC, or of total protein, in the membrane + cytosol, and cycloheximide (40 microM for 5 min) did not alter the translocation of PKC induced by TNF; these results indicate that the effect of TNF on PKC translocation was related to neither de novo membrane synthesis of PKC (as opposed to translocation per se) nor nonspecific augmentation of protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Tumor necrosis factor-alpha activates pulmonary artery endothelial protein kinase C. 843 Aug 18

Vav, a 95 kDa proto-oncogene product expressed specifically in hematopoietic cells, was originally isolated as a transforming human oncogene. Vav contains an array of functional domains that are involved in interactions with other proteins and, possibly, with lipids. These include, among others, a putative guanine nucleotide exchange domain, a cysteine-rich region similar to the phorbol ester/diacylglycerol-binding domain of protein kinase C, a pleckstrin-homology domain, and Src-homology 2 and 3 (SH2 and SH3, respectively) domains. The presence of these domains, the transforming activity of the vav oncogene, and the rapid increase in tyrosine phosphorylation of Vav induced by triggering of diverse receptors indicate that it plays an important role in hematopoietic cell signaling pathways. Such a role is supported by recent studies using "knockout" mice and transiently transfected T cells, in which Vav deletion or overexpression, respectively, had marked effects on lymphocyte development or activation. The presence of a putative guanine nucleotide exchange domain, the prototype of which is found in the dbl oncogene product, implies that Vav functions as a guanine nucleotide exchange factor (GEF) for one (or more) members of the Ras-like family of small GTP-binding proteins. In support of such a role, Vav preparations were found in some (but not other) studies to mediate in vitro-specific GEF activity for Ras. Additional studies are required to identify the physiological regulators and targets of Vav, and its exact role in hematopoietic cell development and signaling.
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PMID:Vav: function and regulation in hematopoietic cell signaling. 872 92

Since the identification of protein kinase C (PKC) in the late 1970s, there have been many attempts to define its involvement in pancreatic beta-cell responses to physiological secretagogues. Early studies made use of PKC inhibitors such as polymyxin B and staurosporine, but their lack of selectivity made results difficult to interpret. Phorbol ester-induced PKC downregulation and measurements of PKC translocation within beta-cells provided useful information, but these studies were further complicated by the identification of novel PKC isoforms which do not possess diacylglycerol-binding sites or do not translocate upon stimulation. Second-generation PKC inhibitors, such as Ro 31-8220 and Go 6976, show improved selectivity and have helped clarify the situation. In addition, the use of antisense oligonucleotides or pseudosubstrate peptide inhibitors to selectively deplete or inhibit particular PKC isoforms has provided valuable information. The application of these varied methodologies has allowed us to develop a fuller understanding of the role played by PKC in beta-cell stimulus-response coupling.
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PMID:Protein kinase C signalling in pancreatic beta-cells: cellular and molecular approaches. 930 97

The specificity of many signal transduction pathways relies on the temporal coordination of different second messenger signals. Here we found a molecular mechanism which guarantees that conventional protein kinase C (PKC) isoforms are sequentially activated by calcium and diacylglycerol signals. Receptor stimuli that triggered repetitive calcium spikes induced a parallel repetitive translocation of GFP-tagged PKCgamma to the plasma membrane. While calcium acted rapidly, diacylglycerol binding to PKCgamma was initially prevented by a pseudosubstrate clamp, which kept the diacylglycerol-binding site inaccessible and delayed calcium- and diacylglycerol-mediated kinase activation. After termination of calcium signals, bound diacylglycerol prolonged kinase activity. The properties of this molecular decoding machine make PKCgamma responsive to persistent diacylglycerol increases combined with high- but not low-frequency calcium spikes.
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PMID:Protein kinase C as a molecular machine for decoding calcium and diacylglycerol signals. 981 2

As part of a cDNA library screen for clones that induce transformation of NIH 3T3 fibroblasts, we have isolated a cDNA encoding the murine homolog of the guanine nucleotide exchange factor RasGRP. A point mutation predicted to prevent interaction with Ras abolished the ability of murine RasGRP (mRasGRP) to transform fibroblasts and to activate mitogen-activated protein kinases (MAP kinases). MAP kinase activation via mRasGRP was enhanced by coexpression of H-, K-, and N-Ras and was partially suppressed by coexpression of dominant negative forms of H- and K-Ras. The C terminus of mRasGRP contains a pair of EF hands and a C1 domain which is very similar to the phorbol ester- and diacylglycerol-binding C1 domains of protein kinase Cs. The EF hands could be deleted without affecting the ability of mRasGRP to transform NIH 3T3 cells. In contrast, deletion of the C1 domain or an adjacent cluster of basic amino acids eliminated the transforming activity of mRasGRP. Transformation and MAP kinase activation via mRasGRP were restored if the deleted C1 domain was replaced either by a membrane-localizing prenylation signal or by a diacylglycerol- and phorbol ester-binding C1 domain of protein kinase C. The transforming activity of mRasGRP could be regulated by phorbol ester when serum concentrations were low, and this effect of phorbol ester was dependent on the C1 domain of mRasGRP. The C1 domain could also confer phorbol myristate acetate-regulated transforming activity on a prenylation-defective mutant of K-Ras. The C1 domain mediated the translocation of mRasGRP to cell membranes in response to either phorbol ester or serum stimulation. These results suggest that the primary mechanism of activation of mRasGRP in fibroblasts is through its recruitment to diacylglycerol-enriched membranes. mRasGRP is expressed in lymphoid tissues and the brain, as well as in some lymphoid cell lines. In these cells, RasGRP has the potential to serve as a direct link between receptors which stimulate diacylglycerol-generating phospholipase Cs and the activation of Ras.
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PMID:Regulation of RasGRP via a phorbol ester-responsive C1 domain. 981 87

The function of the small-Mr Ras-like GTPase Rap1 remains largely unknown, but this protein has been demonstrated to regulate cortical actin-based morphologic changes in Dictyostelium and the oxidative burst in mammalian neutrophils. To test whether Rap1 regulates phagocytosis, we biochemically analyzed cell lines that conditionally and modestly overexpressed wild-type [Rap1 WT(+)], constitutively active [Rap1 G12T(+)], and dominant negative [Rap1 S17N(+)] forms of D. discoideum Rap1. The rates of phagocytosis of bacteria and latex beads were significantly higher in Rap1 WT(+) and Rap1 G12T(+) cells and were reduced in Rap1 S17N(+) cells. The addition of inhibitors of protein kinase A, protein kinase G, protein tyrosine kinase, or phosphatidylinositide 3-kinase did not affect phagocytosis rates in wild-type cells. In contrast, the addition of U73122 (a phospholipase C inhibitor), calphostin C (a protein kinase C inhibitor), and BAPTA-AM (an intracellular Ca2+ chelator) reduced phagocytosis rates by 90, 50, and 65%, respectively, suggesting both arms of the phospholipase C signaling pathways played a role in this process. Other protein kinase C-specific inhibitors, such as chelerythrine and bisindolylmaleimide I, did not reduce phagocytosis rates in control cells, suggesting calphostin C was affecting phagocytosis by interfering with a protein containing a diacylglycerol-binding domain. The addition of calphostin C did not reduce phagocytosis rates in Rap1 G12T(+) cells, suggesting that the putative diacylglycerol-binding protein acted upstream in a signaling pathway with Rap1. Surprisingly, macropinocytosis was significantly reduced in Rap1 WT(+) and Rap1 G12T(+) cells compared with control cells. Together our results suggest that Rap1 and Ca2+ may act together to coordinate important early events regulating phagocytosis.
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PMID:The small Mr Ras-like GTPase Rap1 and the phospholipase C pathway act to regulate phagocytosis in Dictyostelium discoideum. 995 Jun 84


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