Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cellular effects of numerous hormones and neurotransmitters, including the vasoactive agents angiotensin II (AngII) and [Arg8]vasopressin, are mediated in part by protein-serine threonine kinases activated by increase of cytosolic Ca2+ concentration. In this study, we have tested the ability of Ca(2+)-mobilizing agents to activate cellular tyrosine kinases. Treatment of intact GN4 liver epithelial cells with AngII rapidly (less than or equal to 15 sec) increased tyrosine kinase activity measured either in unfractionated cell lysates or in anti-phosphotyrosine immune complexes from detergent-solubilized cells. Increased phosphorylation of the exogenous substrate poly(Glu80Tyr20) (3- to 4-fold over control) by immunoprecipitated kinases closely paralleled the time- and dose-dependence of the appearance of tyrosine phosphoproteins in intact cells. This effect of AngII was mimicked by thapsigargin, a Ca(2+)-elevating tumor promoter. The ability of AngII, but not epidermal growth factor, to increase tyrosine kinase activity was blocked in cells loaded with the Ca2+ chelator bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid. Dephosphorylation of immunoprecipitated proteins by tyrosine phosphatase treatment was accompanied by a 60-70% loss in in vitro kinase activity, suggesting that the AngII-sensitive kinase(s) are activated by phosphorylation in intact cells. These findings demonstrate a link between two widely occurring signaling pathways, the tyrosine kinases and the Ca2+ second-messenger system, and suggest the possible involvement of Ca(2+)-activated tyrosine kinases in the endocrine actions of AngII and [Arg8]vasopressin.
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PMID:Calcium-dependent increase in tyrosine kinase activity stimulated by angiotensin II. 138 99

The retinoblastoma gene product (Rb), a nuclear phosphoprotein, functions as a tumor suppressor that is inactivated in retinoblastoma and other malignancies. The hypophosphorylated forms of Rb are observed in the G0/G1 phase of the cell cycle, whereas the hyperphosphorylated forms predominate in S and G2/M phases, suggesting that phosphorylation/dephosphorylation of Rb may regulate progression through the growth cycle. However, little is known about the intracellular signals that regulate phosphorylation/dephosphorylation of Rb. We show that D-erythro-sphingosine potently induces early dephosphorylation of Rb. Initial dephosphorylation was observed as early as 1 h after treatment of hematopoietic cells with sphingosine, whereas complete shift to the dephosphorylated form was seen 4 h after treatment. These effects occurred at concentrations of sphingosine as low as 100-500 nM, with maximal effects observed at 1-2.5 microM. These effects were specific to sphingosine, inasmuch as other lipids, amphiphiles, and long chain amino bases, as well as structural analogs of sphingosine, failed to induce dephosphorylation of Rb. Also, activation of second messenger systems including protein kinase C, cAMP-dependent kinases, and calcium ionophores, as well as inhibition of serine/threonine protein phosphatases, failed to induce dephosphorylation of Rb. Induction of Rb dephosphorylation by sphingosine preceded inhibition of growth and a specific arrest in the G0/G1 phase of the cell cycle. These studies, for the first time, identify an intracellular activator of Rb.
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PMID:Retinoblastoma protein dephosphorylation induced by D-erythro-sphingosine. 138 23

Cell lines stably overexpressing protein kinase C (PKC)-alpha were previously described by us. These cell lines were generated by the introduction of the full length cDNA coding for PKC-alpha into Swiss/3T3 cells. Here we show that activation of PKC-alpha by phorbol-esters induced in these cells specific phosphorylation of two cellular proteins p90 and p52. Phosphorylation of p80 (MARCKS protein), previously identified as a substrate for PKC, was also enhanced. Phosphorylated p90 and p52 proteins were associated with particulate membrane-enriched fractions and were extractable with the use of nonionic detergents. Time course analysis of phorbol-ester induced phosphorylation of p90 and p52 revealed maximal stimulation of phosphorylation after 15-30 min. Phosphamino acid analysis showed that phosphorylation of p90 and p52 occurred mainly on serine residues. Phosphorylation of p52 was also on threonine residues. Whereas, phorbol ester activation induced phosphorylation of both p90 and p52, the mitogens platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) enhanced phosphorylation of p90, but not p52. Thus, our studies showed the involvement of PKC-alpha in the regulation of p90 and p52 phosphorylation and provided direct evidence for the role of PKC-alpha in cellular signaling by PDGF and FGF. Moreover, the fact that phosphorylation of p52 was specific to phorbol ester activation may suggest its involvement in tumor promotion. Characterization of p90 and p52 will enable us to reveal the phosphorylation cascade activated downstream to PKC-alpha and to determine their role in mitogenic signaling and tumor promotion.
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PMID:Phosphorylation of p90 and p52 in response to phorbol-esters in Swiss/3T3 cells overexpressing protein kinase C-alpha. 142 77

The central region of the N-myc protein has a characteristic amino acid sequence EDTLSDSDDEDD, which is very similar to those of particular domains of adenovirus E1A, human papilloma virus E7, Simian virus 40 large T, c-myc and L-myc proteins. Domains of these three viral oncoproteins have recently been shown to be specific binding sites for the tumor-suppressor gene retinoblastoma protein. We have noted that the sequence of serine followed by a cluster of acidic amino acids is exactly the same as that of a typical substrate of casein kinase II (CKII). Therefore, we investigated whether these nuclear oncoproteins are phosphorylated by CKII. For this purpose, we fused the beta-galactosidase and N-myc genes including this domain and expressed it in Escherichia coli cells. Several mutant N-myc genes, containing single amino acid substitutions in this domain, were also used to produce fused proteins. Strong phosphorylation by CKII was detected with the fused protein of wild-type N-myc. However, no phosphorylation of beta-galactosidase itself was observed and the phosphorylations of fused mutant proteins were low. Another fused N-myc protein containing most of the C-terminal region downstream of this acidic region was not phosphorylated by CKII. Analysis of phosphorylation sites in synthetic peptides of this acidic region identified the major sites phosphorylated by CKII as Ser261 and Ser263. On two-dimensional tryptic mapping of phosphorylated N-myc proteins, major spots of in vitro-labeled and in-vivo-labeled N-myc proteins were detected in the same positions. These results suggest that two serine residues of the acidic central region of the N-myc protein are phosphorylated by CKII in vivo as well as in vitro. The functional significance of this acidic domain is discussed.
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PMID:Specific phosphorylation of the acidic central region of the N-myc protein by casein kinase II. 142 1

We have reported the establishment of two interleukin (IL)-2-dependent human leukemic cell lines (TALL-103/2 [CD3+TCR gamma delta +] and TALL-104 [CD3+ TCR alpha beta +]) which display major histocompatibility complex nonrestricted tumoricidal activity. Whereas TALL-103/2 cells lyse only natural killer cell-susceptible targets, TALL-104 cells display a broad range of tumor target reactivity. In reverse antibody-dependent cell-mediated cytotoxicity (ADCC), lysis by both cell lines is triggered by monoclonal antibodies (mAb) recognizing CD3 and, to a lesser extent, CD2, but not CD8 or CD56 antigens. In conventional cytotoxic assays, the lytic activity of both cell lines is strictly Ca(2+)-dependent. In reverse ADCC, lysis by TALL-103/2 cells is highly dependent on the presence of Ca2+, whereas TALL-104 cells seem to only partially require extracellular Ca2+. The cytoplasm of both cell lines contains azurophilic granules typical of cytotoxic cells. Northern blot analysis demonstrates mRNA expression of pore-forming protein (PFP; perforin) and serine esterases (SE). The magnitude of expression of these transcripts and of lytic activity depends on the doses of IL-2. Upon deprivation of IL-2, TALL-103/2 cells completely lose cytotoxic granules and function within 16 h, whereas TALL-104 cells progressively lose expression of PFP and SE mRNA, as well as killer activity, within 4 wk. Both anti-CD3 mAb and lysable target cells induce efficient BLT-esterase secretion from TALL-103/2 and TALL-104 cells analogous to findings with conventional cytotoxic T lymphocytes. The stable expression of tumoricidal activity over 2 yr in culture renders these cell lines unique and very useful for studies on the regulation of cell-mediated lysis in vitro and in animal models.
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PMID:Two unique human leukemic T-cell lines endowed with a stable cytotoxic function and a different spectrum of target reactivity analysis and modulation of their lytic mechanisms. 142 67

The primary structure of the Lewis lung carcinoma protein HMGY belonging to the nuclear group of proteins HMGI (high mobility group I) was determined using electrospray and fast atom bombardment mass spectrometry. It was demonstrated that the sequence of the tumor protein corresponds to the amino acid sequence derived from the cDNA from cultured cells and that the N-terminal serine residue is N-acetylated. Moreover, the two high performance liquid chromatography-purified forms Y1 and Y2 of the protein HMGY were shown to differ at the level of serine phosphorylation, since they contain three phosphate and two phosphate groups, respectively, in the C-terminal region. No other modification was detected in the remaining part of the molecule.
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PMID:Mass spectrometric analysis of the HMGY protein from Lewis lung carcinoma. Identification of phosphorylation sites. 142 98

The product of the c-raf-1 proto-oncogene is a cytoplasmic serine/threonine protein kinase that appears to be activated in signal transduction from a variety of cell-surface receptors. The mechanism of c-Raf activation upon stimulation of cell-surface receptors is not clear, but there seem to exist multiple pathways of activation which involve tyrosine and/or serine phosphorylation of the c-Raf protein in vivo. The activated state of Raf is reflected in an increased apparent molecular weight of the Raf protein in sodium dodecyl sulfate-polyacrylamide gels owing to hyperphosphorylation. The tumor promoter 12-O-tetradecanoyl phorbol 13-acetate (TPA) is one of the agents able to induce this hyperphosphorylation of Raf in vivo, suggesting that protein kinase C (PKC) may be involved in the activation of c-Raf in particular situations. Using recombinant baculoviruses expressing PKC and Raf polypeptides, we show here that conventional PKC types (alpha, beta, gamma) but not novel types (delta, zeta, eta) or the unrelated Mos kinase are able to activate c-Raf in a TPA-dependent manner upon coexpression in insect cells. Direct phosphorylation of the Raf protein with PKC in vitro also enhanced the kinase activity of c-Raf, suggesting that c-Raf acts immediately downstream of PKC in a protein kinase cascade which is triggered by TPA and may lead to transcriptional activation of TPA-inducible genes and tumor promotion.
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PMID:Activation of the c-Raf protein kinase by protein kinase C phosphorylation. 143 48

The monoclonal antibody (mAb) 1801 has been reported to identify an N-terminal determinant within the tumor-suppressor protein p53 located between amino acids 32 and 79. This region contains two potential sites for serine phosphorylation at amino acids 33 and 46. Using a novel technique which dephosphorylates proteins in situ in fixed permeabilized cells, we have unmasked determinants in p53 recognized by mAb 1801, allowing additional sites of p53 protein to be detected in immunohistochemically reacted cells. This result indicates that phosphorylation at one or both sites within the determinant recognized by mAb 1801 previously blocked antibody-ligand interaction. It further suggests that in situ dephosphorylation may be of more general use in identifying antibodies which can only bind to epitopes in a particular phosphorylation state.
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PMID:In situ dephosphorylation of p53 protein by calf intestinal alkaline phosphatase treatment. 143 59

Human mononuclear phagocytes have the capacity to participate directly in extracellular matrix turnover via the secretion of neutral proteinases. These neutral proteinases include the serine proteinases, elastase and cathepsin G and the metalloproteinases, interstitial collagenase, 92 kD type IV collagenase, 72 kD type IV collagenase and stromelysin. Mononuclear phagocytes also produce the counter-regulatory metalloproteinase inhibitor, TIMP (tissue inhibitor of metalloproteinases). We have studied the capacity of normal human mononuclear phagocytes and of the human monocytic tumor line U937 to elaborate proteinases and inhibitors. The serine proteinases, elastase and cathepsin G, are present only at the earliest stages of mononuclear phagocyte differentiation (U937 cells in the basal state, freshly isolated peripheral blood monocytes) and are stored within intracellular granules. As human mononuclear phagocytes differentiate (U937 cells exposed to phorbol esters, human monocytes cultured in vitro), the cellular content of these serine proteinases declines rapidly. Accompanying the acquisition of a more differentiated state, the ability for regulated secretion of the neutral metalloproteinases is attained. This capacity is acquired in a sequential manner, with secretion of the 92 kD type IV collagenase observed at earlier states of differentiation while release of stromelysin requires a fully differentiated and LPS (lipopolysaccharide)-stimulated alveolar macrophage. Interstitial collagenase and 72 kD type IV collagenase are synthesized at intermediate stages of differentiation. In comparison to human fibroblasts, human mononuclear phagocytes produce approximately 10-30% of the interstitial collagenase, 10% of the stromelysin and 1-2% of the 72 kD type IV collagenase on a per cell basis. Synthesis of the 92 kD type IV collagenase is restricted to the inflammatory cell (but also occurs in neutrophils and keratinocytes).
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PMID:Neutral proteinase expression by human mononuclear phagocytes: a prominent role of cellular differentiation. 148 61

Phorbol ester tumor promoters activate gene transcription by regulating both the synthesis and posttranslational modification of the activator protein 1 (AP-1) transcription factor, c-Jun and JunB are components of the mammalian AP-1 complex. Here we demonstrate that in U-937 human leukemic cells, phorbol esters stimulate the phosphorylation of the amino terminus of human c-Jun (JUN) but not human JunB (JUNB). Mutational analysis indicates that serine-63 and -73, which reside within the putative regulatory domain of JUN, are required for both constitutive and phorbol 12-myristate 13-acetate-inducible N-terminal JUN phosphorylation. To determine the functional role of this N-terminal phosphorylation, we prepared several chimeric proteins containing the N-terminal 84 amino acids (positions 5-89) of human JUN or murine JUNB fused to the yeast GAL4 DNA-binding domain. This region was found to be sufficient for the phorbol ester-inducible transcriptional activity of JUN, but not JUNB. This induction was abolished by the mutation of serine-63 and -73 to leucine residues. Thus, we propose that phorbol esters enhance the trans-activation potential of JUN, but not JUNB, by the phosphorylation of the N-terminal regulatory domain of JUN.
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PMID:Phorbol ester-induced amino-terminal phosphorylation of human JUN but not JUNB regulates transcriptional activation. 149 19


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