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:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transformation by activated pp60c-src has been correlated by genetic analysis with the tyrosine phosphorylation of a 120 kilodalton (kDa) protein, p120. We now demonstrate tyrosine phosphorylation of p120 following stimulation of cells by growth factors whose receptors have intrinsic tyrosine-specific protein kinase activity. Stimulation of quiescent NIH3T3 cells with platelet-derived growth factor (PDGF) resulted in the tyrosine phosphorylation of p120 that was maximal by 5 min and returned to background levels by 30 min. p120 was also phosphorylated on tyrosine after addition of colony-stimulating factor 1 (CSF-1) or epidermal growth factor (EGF) to NIH3T3 cells engineered to express high levels of their respective receptors. Two additional src substrates, p110 and p85, were analysed under identical assay conditions. PDGF, CSF-1, and EGF induced only a minimal increase in the tyrosine phosphorylation of p85 and no change in the phosphorylation of p110. Thus, the marked ligand-induced tyrosine phosphorylation of p120 was a property not shared by the other src substrates examined. Immunoblotting with antibodies to p120 and the ras GTPase activating protein, GAP, suggests that p120 and GAP are unrelated. In addition, the amino acid sequences of four cyanogen bromide peptides derived from p120 showed no homology to GAP or to sequences in either the PIR or Swiss-Prot databases. These data suggest that tyrosine phosphorylation of p120 may contribute to both signal transduction through growth factor receptors and pp60src induced transformation.
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PMID:PDGF, CSF-1, and EGF induce tyrosine phosphorylation of p120, a pp60src transformation-associated substrate. 185 49

Colonic neoplasia provides an opportunity to study tumor progression because most carcinomas arise from adenomas (polyps), which, in turn, arise from normal epithelia. The malignant potential of adenomas varies with size, histology, and degree of dysplasia. Polyps that are less than 2 cm with villous architecture and severe dysplasia are most likely to contain carcinoma. Previous studies demonstrated that the in vitro protein-tyrosine kinase activity of pp60c-src from colon carcinomas is significantly higher than that from adjacent normal mucosa. Here we report that the protein kinase activity of pp60c-src is also elevated in colonic polyps. Activity is highest in malignant polyps and in greater than 2-cm benign polyps that contain villous structure and severe dysplasia. Thus, pp60c-src activation occurs in benign polyps that are at greatest risk for developing cancer. These data suggest that activation of the protooncogene product pp60c-src may be an important event in the genesis of human colon carcinoma.
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PMID:Activation of the pp60c-src protein kinase is an early event in colonic carcinogenesis. 210 87

We examined pp60c-src protein kinase activity in human gastric carcinoma cell lines and gastric carcinoma tissues as well as normal mucosa. pp60c-src kinase activity was detected in all 5 carcinoma cell lines at various levels. Of 16 gastric carcinoma tissues, 8 showed higher pp60c-src kinase activity in tumor tissues than in corresponding normal mucosa. However, the levels of expression of pp60c-src detected by Western blotting were not always consistent with the activities of pp60c-src protein kinase. These findings suggest that the increase in pp60c-src protein kinase activity might be brought about by post-translational changes.
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PMID:pp60c-src protein kinase activity in human gastric carcinomas. 211 May 50

The product of the c-src proto-oncogene (pp60c-src) is a tyrosine-specific protein kinase that is expressed in two phases of neural development. In post-mitotic neuronal cells undergoing terminal differentiation, pp60c-src is present at high levels in the membrane of nerve growth cones and proximal axon shafts. Membrane-associated forms of alpha- and beta-tubulin are the major phosphotyrosine-modified proteins in growth cone membranes in vivo. pp60c-src phosphorylates purified, unassembled tubulin subunits in vitro, inhibiting their ability to polymerize into microtubules. It is conceivable that tubulin phosphorylation by pp60c-src in the growth cone may regulate neurite extension by altering adhesion of cells to the substratum.
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PMID:Tyrosine phosphorylation of membrane-associated tubulin in nerve growth cones enriched in pp60c-src. 211 26

The transforming protein of polyomavirus, middle T (mT), forms a complex with two cellular enzymes: the protein tyrosine kinase pp60c-src and a phosphatidylinositol (PtdIns) 3-kinase. A mutant virus, Py1178T, encodes an mT protein which associates with and activates pp60c-src to the same extent as the wild type but fails to associate with PtdIns 3-kinase. To investigate relationships between activation of pp60c-src, association of PtdIns 3-kinase, and cellular levels of the second messenger inositol 1,4,5-trisphosphate (InsP3), we examined the effects of wild-type and mutant mT proteins on inositol metabolism in rat and mouse fibroblasts. Expression of either wild-type or 1178T mT caused a 300 to 500% increase in the InsP3 level. Cells transformed by Rous sarcoma virus also showed similar increases in InsP3 levels. Mutant mT proteins which failed to activate pp60c-src (NG59 and 1387T) had no effect on InsP3 levels. Pulse-chase experiments with [3H]inositol showed that the turnover of phosphoinositides was increased in cells transformed by either wild-type polyomavirus or Py1178T as compared with the normal parent cell line. The turnover of inositol phosphates was unchanged upon transformation. These data indicate that cells expressing either wild-type or mutant 1178T mT or pp60v-src exhibit elevated levels of InsP3 because of activation of phospholipase C. This activation appears to depend, directly or indirectly, upon activation of pp60src protein kinase activity. Activation of pp60c-src and elevation of InsP3 content are not sufficient for full transformation. Full transformation also requires the association of mT-pp60c-src complexes with PtdIns 3-kinase.
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PMID:Inositol trisphosphate levels in cells expressing wild-type and mutant polyomavirus middle T antigens: evidence for activation of phospholipase C via activation of pp60c-src. 215 7

The control of cell proliferation involves both regulatory events initiated at the plasma membrane that control reentry into the cell cycle and intracellular biochemical changes that direct the process of cell division itself. Both of these aspects of cell growth control can be studied in Xenopus oocytes undergoing meiotic maturation in response to mitogenic stimulation. All mitogenic signaling pathways so far identified lead to the phosphorylation of ribosomal protein S6 on serine residues, and the biochemistry of this event has been investigated. Insulin and other mitogens activate ribosomal protein S6 kinase II, which has been cloned and sequences in oocytes and other cells. This enzyme is activated by phosphorylation on serine and threonine residues by an insulin-stimulated protein kinase known as MAP-2 kinase. MAP kinase itself is also activated by direct phosphorylation on threonine and tyrosine residues in vivo. These results reconstitute one step of the insulin signaling pathway evident shortly after insulin receptor binding at the membrane. Several hours after mitogenic stimulation, a cell cycle cytoplasmic control element is activated that is sufficient to cause entry into M phase. This control element, known as maturation-promoting factor or MPF, has been purified to near homogeneity and shown to consist of a complex between p34cdc2 protein kinase and cyclin B2. In addition to apparent phosphorylation of cyclin, regulation of MPF activity involves synthesis of the cyclin subunit and its periodic degradation at the metaphase----anaphase transition. The p34cdc2 kinase subunit is regulated by phosphorylation/dephosphorylation on threonine and tyrosine residues, being inactive when phosphorylated and active when dephosphorylated. Analysis of phosphorylation sides in histone H1 for p34cdc2 has revealed a consensus sequence of (K/R)S/TP(X)K/R, where the elements in parentheses are present in some but not all sites. Sites with such a consensus are specifically phosphorylated in mitosis and by MPF in the protooncogene pp60c-src. These results provide a link between cell cycle control and cell growth control and suggest that changes in cell adhesion and the cytoskeleton in mitosis may be regulated indirectly by MPF via protooncogene activation. S6 kinase II is also activated upon expression of MPF in cells, indicating that MPF is upstream of S6 kinase on the mitogenic signaling pathway. Further study both of the signaling events that lead to MPF activation and of the substrates for phosphorylation by MPF should lead to a comprehensive understanding of the biochemistry of cell division.
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PMID:Xenopus oocytes and the biochemistry of cell division. 215 26

We have isolated four activated transforming human c-src mutants derived spontaneously from viruses carrying the normal human c-src (SRC) genes in the form of Rous sarcoma virus. These mutants induced transformed cell morphology distinguishable from each other in vitro as well as tumors in chicks, whereas normal SRC-carrying viruses did not. Analyses of the transforming SRC proteins together with the normal SRC protein showed that levels of the carboxy-terminal Tyr-phosphorylation were negatively correlated with both transforming ability and protein kinase (PKase) activity as determined by in vitro autophosphorylation. It was observed that two cell lysis methods, that is, NP-40 and RIPA, yielded two different phosphorylated forms of transforming SRC proteins: one possessed low levels of phosphorylation at the autophosphorylation site and the other possessed high levels of phosphorylation at this site. Using the two types of transforming SRC preparations, we have studied in vitro SRC-PKase reactions in relation to in vivo and in vitro autophosphorylation and in vitro phosphorylation of an exogenous substrate. A possible functional relationship between autophosphorylation and SRC-PKase expression is discussed.
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PMID:Characterization of avian retroviruses carrying activated transforming human c-src genes and of steps involved in expression of activated src-PKases in vitro. 216 36

Three different types of experiments are presented in this paper, the results of which converge to indicate that the viral src protein associates with and modulates the activity and/or the specificity of a serine/threonine protein kinase. Firstly, a 60-kDa protein from extracts of FR3T3 rat fibroblasts transformed by wild-type Rous sarcoma virus (SRD-FR3T3) is shown to be immunoprecipitated with a monoclonal antibody (mAb) raised against bacterially produced pp60v-src, the mAb327 [Lipsich, L. A., Lewis, A. J. & Brugge, J. S. (1983) J. Virol. 48, 352-360] and to be phosphorylated in vitro at serine/threonine/tyrosine residues, in the ratio 25:53:22. Under the same experimental conditions, the pp60c-src protein immunoprecipitated with mAb327 from extracts of NIH c-src overexpresser cells is phosphorylated exclusively on tyrosine residues. Secondly, the results of immunoprecipitation experiments using a tumor-bearing rabbit (TBR) serum and reported in an earlier work [David-Pfeuty, T. & Hovanessian, A. (1984) Eur. J. Biochem. 140, 325-342], together with those reported here, suggest that the TBR-immunoprecipitated pp60v-src coprecipitates with a cellular protein related to the 60-kDa subunit of the Ca2+/calmodulin protein kinase II from brain. Finally, partially purified preparations of pp60v-src, but not of pp60c-src, are shown to contain a Ca2+/calmodulin-dependent protein kinase activity that phosphorylates a 52-kDa protein substrate.
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PMID:Serine/threonine-specific protein kinase activity associated with viral pp60src protein. 216 17

We have observed a modification of the cellular protein kinase pp60c-src, elicited in murine 3T3 fibroblasts by platelet-derived growth factor (PDGF). The modification occurred rapidly after addition of PDGF to the culture medium and was first detected as a reduction in the electrophoretic mobility of a portion of the pp60c-src molecules. A similarly modified form of the viral homologue pp60v-src occurs in vivo in the absence of stimulation by PDGF. The occurrence of modified forms of both pp60c-src and pp60v-src was associated with a novel phosphorylation at tyrosine in the amino-terminal domains of the proteins. The time-course and dose-response for this modification of pp60c-src paralleled PDGF-induced increases in phosphorylation of pp36, a major cellular substrate for several tyrosine-specific protein kinases. In parallel experiments, treatment of cells with PDGF increased the kinase activity of pp60c-src in an immunocomplex assay. These results suggest pp60c-src may play a role in the mitogenic response to PDGF.
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PMID:The product of the protooncogene c-src is modified during the cellular response to platelet-derived growth factor. 241 73

The effect of polyoma middle-sized tumor antigen (MTAg) on phosphatidylinositol metabolism has been characterized in vivo and in vitro using polyoma-transformed and polyoma-infected cells. Cells infected with transformation-competent polyoma virus exhibit increased levels of inositol phospholipids and the second messenger inositol trisphosphate. MTAg or pp60c-src immunoprecipitates from MTAg-transformed cells contain an activity that phosphorylates phosphatidylinositol and phosphatidylinositol 4-phosphate. This activity is induced in parallel with MTAg when the MTAg synthesis is regulated by hormonal or heavy metal inducers. Immunoprecipitates from one class of polyoma mutants defective in transformation have a reduced level of associated phosphatidylinositol kinase activity in vitro yet are capable of tyrosine phosphorylation on exogenous protein substrates at rates comparable to wild-type virus. Thus, for these mutants, phosphatidylinositol kinase activity is more tightly correlated with transformation than is protein kinase activity. These results suggest that alterations in phosphatidylinositol metabolism by MTAg play a role in transformation by polyoma virus.
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PMID:Phosphatidylinositol metabolism and polyoma-mediated transformation. 242 8


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