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

The effect of transforming growth factor beta (TGF-beta) on human gastric carcinoma cell lines was examined. Cell growth and DNA synthesis of TMK-1 were inhibited by TGF-beta, whereas MKN-28 presented no response to TGF-beta. Scatchard plot analysis of TGF-beta binding showed that TMK-1 had a relatively small number of high-affinity receptors, whereas MKN-28 had a large number of low-affinity receptors. By affinity labeling, only the type I receptor (Mr 65,000) for TGF-beta was detected in TMK-1, while three types of receptors, type I, type II (Mr 85,000-95,000), and type III (Mr 250,000-350,000), for TGF-beta were present in MKN-28. TGF-beta treatment reduced p34cdc-2 kinase activity and the level of phosphorylation of retinoblastoma protein in TMK-1, whereas it did not affect them in MKN-28. mRNAs for MYC and platelet-derived growth factor B chain were increased by treatment of TGF-beta on TMK-1. cAMP-responsive element binding activity was decreased by TGF-beta treatment in MKN-28 but not in TMK-1. This was closely correlated with protein kinase C activity. These results suggest that the type I receptor for TGF-beta in human gastric carcinoma cells may be mainly linked with the growth inhibition of TGF-beta by a decrease in retinoblastoma protein phosphorylation by p34cdc-2 without suppression of MYC expression. Conversely, TGF-beta may reduce protein kinase C activity and cAMP-responsive element binding activity in TGF-beta-resistant gastric carcinoma cells.
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PMID:Growth inhibition of transforming growth factor beta on human gastric carcinoma cells: receptor and postreceptor signaling. 130 37

One approach to identify postreceptor molecular events that transduce the negative-growth signals of inhibitory cytokines is to analyze the cytokine-induced modifications in the expression of cell-cycle-controlling genes. Here we report that suppression of phosphorylation of the retinoblastoma gene product (pRb) is a receptor-generated event triggered by interferons and interleukin 6 (IL-6) in hematopoietic cell lines. The conversion of pRb to the underphosphorylated forms occurs concomitantly with the decline in c-myc protein expression and both events precede the G0/G1-phase arrest induced by the cytokines. Loss of IL-6-induced c-myc responses in cells that have been stably transfected with constitutive versions of the c-myc gene abrogates the typical G0/G1-phase arrest but does not prevent the specific dephosphorylation of pRb. Conversely, depletion of protein kinase C from cells interferes with part of the interferon-induced suppression of pRb phosphorylation and relieves the G0/G1-phase cell-cycle block without affecting the extent of c-myc inhibition. None of the cytokines, including transforming growth factor beta, reduce the phosphorylation of pRb in S-phase-blocked cells. In contrast, the other IL-6-induced molecular responses, including the decline in c-myc mRNA levels, are not phase-specific and develop normally in S-phase-blocked cells that are depleted of the underphosphorylated functional forms of pRb. These and the suppression of pRb phosphorylation, which occur independently of each other, and suggest that the development of the interferon- or IL-6-induced G0/G1-specific arrest requires at least these two receptor-generated events.
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PMID:Interferons and interleukin 6 suppress phosphorylation of the retinoblastoma protein in growth-sensitive hematopoietic cells. 137 Mar 54

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

Protein kinase C and its family of multiple subspecies play pivotal roles in cell-surface mediated signal transduction. For example, in the process of synthesizing melatonin, the activation of alpha 1-adrenergic receptor sites in the pineal gland causes translocation of protein kinase C, which in turn enhances the beta-adrenergic-activated accumulation of both cyclic AMP and cyclic GMP. In the retina, protein kinase C phosphorylates rhodopsin and hence is involved in visual transduction. The activation of protein kinase C depends on the presence of phospholipid and Ca++. In this communication, we report that the bovine pineal gland and retina possess unique protein kinase C isoenzymes that are distinct from those seen in the rat brain. Furthermore, in retinoblastoma cells in culture, protein kinase C is stimulated by a cooperative interaction between calcium and zinc. Moreover, the subcellular regions of retina that exhibit the highest activity of protein kinase C also possess the highest concentration of zinc. In view of the fact that the bovine pineal gland and retina continually synthesize metallothionein and other low molecular weight zinc binding proteins, we propose that zinc and metallothionein participate in signal transduction in the retina and pineal gland. The action of metallothionein, a zinc binding protein, in activating protein kinase C is opposite to that of calcium binding protein, which is a potent inhibitor of protein kinase C.
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PMID:Pineal and retinal protein kinase C isoenzymes: cooperative activation by calcium and zinc metallothionein. 156 29

Transforming growth factor-beta 1 (TGF-beta 1) rapidly increases the expression of junB transcription factor and plasminogen activator inhibitor-1 (PAI-1) and prevents the cell cycle-dependent phosphorylation of the RB retinoblastoma susceptibility gene product during late G1 phase in Mv1Lu lung epithelial cells. These responses are shown in this report to be blocked by the potent serine/threonine protein kinase inhibitor, H7, added with TGF-beta 1. Added alone, H7 does not alter the basal junB or PAI-1 mRNA levels, the deposition of PAI-1 into the extracellular matrix, or the phosphorylation of RB in late G1 phase, suggesting that this inhibitor does not have a general nonspecific effect on the cell. The analogs H8 and H9, which are preferential inhibitors of cyclic nucleotide-dependent protein kinases, are fivefold less potent than H7 as inhibitors of the TGF-beta response. The PAI-1 response to TGF-beta 1 is not affected by the simultaneous addition of staurosporine, which is a protein kinase C inhibitor, or by the prolonged preincubation of cells with phorbol 12-myristate 13-acetate, which down-regulates protein kinase C. The results suggest the possibility that H7 and its analogs block various early TGF-beta responses by inhibiting a protein serine/threonine kinase(s).
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PMID:Evidence for the involvement of protein kinase activity in transforming growth factor-beta signal transduction. 172 3

Transformation of secondary Sprague-Dawley rat embryo (RE) cells with type 5 adenovirus (Ad5) results in morphologically transformed cells which can undergo a series of sequential changes resulting in enhanced expression of the transformed phenotype, a process termed progression. Selection for a progressed phenotype often occurs after growth in agar or tumor formation in nude mice, and this process is reversible following treatment of cells with 5-azacytidine. In the present study we have analyzed a series of clonal populations of Ad5-transformed RE cells representing different stages in a defined progression lineage. Progression was not associated with alterations in the steady-state levels of mRNA produced by the viral transforming genes, E1A and E1B, or the cellular gene, c-myc. In addition, the tumor-promoting agent 12-O-tetradecanoyl-phorbol-13-acetate (TPA), which induces expression of a progressed phenotype in Ad5-transformed RE cells, did not significantly alter the RNA transcription rates of the Ad5 E1A or E1B genes, the TPA-inducible gene TPA-S1 or the TPA-responsive genes Pro1 or protein kinase C. TPA did, however, increase by 1 h the steady-state level of c-fos mRNA, but this effect was similar in both progressed and unprogressed cells. Progression also did not involve a change in the RNA transcription rate of a number of cellular and viral genes, including actin, c-Ha-ras, c-myc, v-fos, erbB, TGF-alpha, TGF-beta, Pro-2, transin, TPA-R1, v-myb and c-mos, or other adenovirus genes in addition to E1A and E1B, including E2A and E4. Immunoblotting analysis using E1B polyclonal antiserum further indicated that progression was not associated with changes in the levels of an Mr 21,000 polypeptide encoded by E1B. Similarly, immunoprecipitation analysis with an Ad2 E1A monoclonal antibody indicated similar levels of the Mr 55,000 and 48,000 E1A polypeptides, as well as coprecipitated proteins of Mr 300,000, 107,000 and 105,000 [which is the retinoblastoma (Rb) protein], in E11 and E11-NMT cells. Immunoprecipitation of cell lysates with a monoclonal antibody specific for the Mr 105,000 Rb protein further demonstrated that progression also was not associated with a change in the level or state of phosphorylation of the Rb protein. However, transfection of a human Rb gene (also containing a neomycin resistance gene) into Ad5-transformed RE cells was more inhibitory, with respect to formation of G418-resistant colonies, in unprogressed than in progressed Ad5-transformed RE cells.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Analysis of viral and cellular gene expression during progression and suppression of the transformed phenotype in type 5 adenovirus-transformed rat embryo cells. 192 6

Pyroglutamyl peptidase II (EC 3.4.19.-), a membrane-bound metalloproteinase, is a highly specific TRH-degrading enzyme. Exposure of Y-79 human retinoblastoma cells to 12-0-tetradecanoyl phorbol 13-acetate (TPA) decreased the activity of this enzyme in a time- and concentration-dependent manner (IC50 5 x 10(-9) M). After 15 min of TPA treatment, only 10% of pyroglutamyl peptidase II activity remained. TPA treatment did not affect the activity of the cytosolic enzyme pyroglutamyl peptidase I (EC 3.4.19.3) or the membrane-bound enzyme dipeptidyl peptidase IV (EC 3.4.19.3). Pretreatment of the cells with the protein kinase C inhibitors H-7 or sphingosine prevented the inactivation of pyroglutamyl peptidase II by TPA. The time course of the TPA-mediated effect paralleled the time course of translocation and activation of protein kinase C in this cell line. Immunoblot analysis demonstrated that inactivation of pyroglutamyl peptidase II was not due to dissociation or internalization of this enzyme molecule. Incubation of TPA-activated Y-79 cell membranes with gamma-[32P]-ATP followed by immunoprecipitation revealed a time-dependent phosphorylation of a 48 kilodalton subunit of pyroglutamyl peptidase II. These studies indicate that the phorbol ester effect is mediated by protein kinase C, and reveal a mechanism of potentiation of the action of TRH at its target sites.
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PMID:Rapid inactivation and phosphorylation of pyroglutamyl peptidase II in Y-79 human retinoblastoma cells after exposure to phorbol ester. 197 29

Protein phosphorylation has evolved as the most versatile posttranslational modification widely used by cells. Signal transduction pathways mediated by activation of MAP kinases and protein kinase C trigger the exit of cells from the quiscence (Go-->G1 transition). Indeed, binding of growth factors at the cell surface triggers their receptors, usually possessing a tyrosine kinase on the cytoplasmic side, to phosphorylate other molecules passing on the information sequentially to GRB2 protein, to p21ras, to c-Raf-1, to MAP kinase kinase, to MAP kinase, to p90rsk, to transcription factors. Activated PKC, MAP kinase, and pp90src can translocate to the nucleus where they phosphorylate a number of protein transcription regulators in a cell cycle-dependent manner or in response to cell stimulation for exit from quiescence. The cell cycle is mainly regulated by p34cdc2 or otherwise called cdc2 in association with cyclins B at G2/M and by Cdk2 in association with cyclins A, D1, and E at G1/S checkpoints; phosphorylation of histone H1 and lamins by cdc2 triggers chromosome assembly and nuclear envelope breakdown, respectively, as a prelude to mitosis. Cdc2 activities functioning as a G2/M regulator are controlled by its phosphorylation and dephosphorylation at Ser/Thr residues. MAP kinases might be the missing link in the chain connecting the Go to G1 transition with the cell cycle regulation, whereas phosphorylation of replication protein factors, retinoblastoma, and p53 might link the G1 to S transition with the control of DNA synthesis. A number of transcription factors are known to stimulate DNA replication, including p53, c-Myc, AP-1, Oct-1, T-antigen; the DNA binding activities of all these proteins and their interaction with other transcription factors are controlled by phosphorylation. The nuclear import of several proteins including NF kappa B, Dorsal, glucocorticoid receptor, ISGF3, rNFIL-6, T antigen, and the kinases PKC, MAP, and p90rsk, are dependent on their phosphorylation at specific sites. Histone phosphorylation stimulated at discrete stages of the cell cycle or in response to cAMP or other stimuli might induce profound changes in chromatin organization.
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PMID:Phosphorylation of transcription factors and control of the cell cycle. 754 80

Human diploid fibroblasts have a finite proliferative lifespan in culture, at the end of which they are arrested with G1 phase DNA contents. Upon serum stimulation, senescent cells are deficient in carrying out a subset of early signal transduction events such as activation of protein kinase C and induction of c-fos. Later in G1, they uniformly fail to express late G1 genes whose products are required for DNA synthesis, implying that they are unable to pass the R point. Failure to pass the R point may occur because senescent cells are unable to phosphorylate the retinoblastoma protein, owing to the accumulation of inactive complexes of cyclin E/Cdk2 and possibly cyclin D/Cdk4. Senescent cells contain high amounts of p21, a potent cyclin-dependent kinase inhibitor whose levels are also elevated in cells arrested in G1 following DNA damage, suggesting that both arrests might share a common mechanism. Cell aging is accompanied by a progressive shortening of chromosomal telomeres, which could be perceived by the cells as a form of DNA damage that gives rise to the signals that inactive the cell cycle machinery.
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PMID:Origins of G1 arrest in senescent human fibroblasts. 757 95

In this present work, the authors discuss some recent advances in the pathogenesis of pituitary tumours. The model of transgenic mice suggest that chronic hormonal stimulation and some growth factors could sustain pituitary tumour development. However, these data are not suitable for human pituitary adenomas. The evidence that most pituitary adenomas are monoclonal in origin has prompted a search for somatic mutations. The mutated Gs alpha are found in only 30-40% of somatotroph adenomas and the ras mutations seem to be associated with the malignant transformation. In some prolactinomas resistant to the bromocriptine treatment, quantitative and qualitative alterations of the dopamine receptor D2, have been described. Mutations of protein kinase C have been identified in some invasive pituitary tumours. Molecular abnormalities have been reported in some cases (allele loss at the 11q13 locus, retinoblastoma gene mutation, aberrant expression of hst gene, Pit-1 overexpression) but none by itself can explain the tumour formation. The pituitary tumorigenesis is certainly a multistep process with the intervention of multiple promoting factors.
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PMID:[Etiopathogenesis of pituitary tumors]. 780 23


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