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 expression of many genes is altered upon the activation of macrophages by bacterial LPS. These genes play a crucial role in the orchestration of various responses to protect the host against infection. A novel 2.3 kilobase (kb) cDNA, designated IRG1, was obtained from a cDNA library prepared with RNA isolated from RAW 264.7 following lipopolysaccharide stimulation. Sequence analysis of the clone revealed no identity to any known genes but showed the presence of many potential phosphorylation sites suggesting that IRG1 protein product may be regulated at this level. Furthermore, IRG1 contains the motif for glycosaminoglycan attachment site, implying that IRG1 may be a proteoglycan. By interspecific back-cross analysis, Irg1 was mapped to mouse chromosome 14 linked to Tyrp2 and Rap2a. The IRG1 message appears 1.5 h following LPS exposure and its induction was not dependent on new protein synthesis. In fact, cycloheximide induced the expression of IRG1, suggesting that a protein repressor prevents the expression of IRG1 when uninduced. The role of the protein kinase A pathway in regulating the induction of IRG1 by LPS is questionable, because although forskolin inhibited its induction, neither dibutyrl-cAMP nor 8-(4-chlorophenylthio)-cAMP had much effect on its expression. In contrast, activation of protein kinase C potentiated the LPS response. Chelation of extracellular calcium inhibited IRG1 4 h after LPS induction, while increasing intracellular calcium had little effect on the levels of the IRG1 transcript. Inhibiting tyrosine phosphorylation abrogated the induction of IRG1 by LPS. Hence, the induction of IRG1 by LPS is mediated by tyrosine kinase and protein kinase C pathway.
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PMID:Cloning and analysis of gene regulation of a novel LPS-inducible cDNA. 772 48

Abnormalities of retinal pericytes and endothelial cells are prominent features of diabetic retinopathy. In this study, we used cultures of bovine retinal cells to examine the regulation of cell-associated proteoglycans, a class of highly sulfated macromolecules important in the regulation of cell growth. Bovine retinal pericytes and endothelial cells were radiolabeled with 35SO4 and cell-associated proteoglycans were removed from the cell surface, quantified, and characterized. The effects of high glucose concentration (25 mM), phorbol 12,13-dibutyrate (PDBu, 0.1 microM), and ascorbic acid (0.1 mM) on cell-associated proteoglycans and growth of these cells were studied. Our results showed that both the ionically bound and the membrane-intercalated forms of cell-associated proteoglycans are present on retinal cells. The predominant cell-associated proteoglycan of pericytes is chondroitin sulfate and for endothelial cells it is heparan sulfate. High glucose concentration and ascorbic acid increased the cell-associated proteoglycans on pericytes but reduced them on endothelial cells. In contrast to this divergent trend, high glucose concentration and ascorbic acid inhibited the growth of both pericytes and endothelial cells. The effects of high glucose on retinal cell-associated proteoglycans were mimicked by PDBu added in a manner to stimulate protein kinase C activity. We conclude that cell-associated proteoglycans are present on retinal pericytes and endothelial cells. High glucose concentration and ascorbic acid affect cell-associated proteoglycans of these two cell types in opposite directions, whereas both suppress the growth of the two cell types. Therefore, it is not likely that high glucose concentration and ascorbic acid change the rate of retinal cell growth directly by affecting cell-associated proteoglycan levels.
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PMID:Cell-associated proteoglycans of retinal pericytes and endothelial cells: modulation by glucose and ascorbic acid. 785 4

Focal adhesion formation in fibroblasts results from complex transmembrane signaling processes initiated by extracellular matrix molecules. Although a role for integrins with attendant tyrosine kinases has been established, there is evidence that cell surface heparan sulfate proteoglycans (HSPGs) are also involved with an associated role of protein kinase C. The identity of the proteoglycan has remained elusive, but we now report that syndecan 4 (ryudocan/amphiglycan) is present in focal adhesions of a number of cell types. Affinity-purified antibodies raised against a unique portion of the cytoplasmic domain of syndecan 4 core protein recognized an HSPG of similar characteristics to those of syndecan 4. These antibodies stained focal adhesions only after cell permeabilization and recognized differing mammalian species. Syndecan 4 was associated with focal adhesions that contained either beta 1 or beta 3 integrin subunits and those that formed on substrates of fibronectin, laminin, vitronectin, or type I collagen. No focal adhesions were found that were vinculin-containing but lacked syndecan 4. In contrast, syndecan 2, whose cytoplasmic domain is closely homologous to syndecan 4, does not appear to be a focal adhesion component. Thus, syndecan 4 represents a new transmembrane focal adhesion component, probably involved in their assembly.
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PMID:Syndecan 4 heparan sulfate proteoglycan is a selectively enriched and widespread focal adhesion component. 801 4

We have analysed the mechanism of PMA-induced adhesion of the MDS human leukemia cell line. Affinity to various matrix ligands indicated that PMA induced fibronectin adhesion of MDS cells. This interaction could not be inhibited by RGDS-peptide, therefore it was most probably not mediated by integrins. Rather, both the basal and PMA-induced fibronectin adhesion of MDS cells could be inhibited by heparin and much less efficiently by chondroitin sulphate, suggesting that glycosaminoglycans of proteoglycans may be responsible for the change in adhesive phenotype. PMA stimulation of MDS cells induced a significant increase in proteoglycan biosynthesis. Studies on the glycosaminoglycan pattern of the proteoglycans showed that PMA treatment initiated a shift in glycanation of the MDS-proteoglycans from the predominant chondroitin sulphate-proteoglycans in control cells to a predominant heparan sulphateproteoglycans in adherent cells. These data indicate that protein kinase C, the main target of PMA, may have a profound role in the regulation of glycanation pattern of proteoglycans. Furthermore, such alterations in the cellular proteoglycans may significantly affect the matrix adhesion potential of hematopoietic cells.
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PMID:PMA induces shift from chondroitin to heparan sulphate on proteoglycans correlating with fibronectin adhesion of MDS human leukemia cells. 807 77

We investigated the effects of PAL (protocatechualdehyde), a metabolite of ACP (3,4-diacetoxy benzylidene diacetate) which is a candidate as a novel antirheumatic agent, on the production of a tissue inhibitor of metalloproteinases (TIMP) using a primary chondrocyte culture from bovine nasal septum cartilage. The addition of human recombinant interleukin-1 alpha (hrIL-1 alpha) induced proteoglycan (PG) depletion from a chondrocyte matrix. PAL significantly reduced the induction of PG depletion. HrIL-1 alpha increased the casein-degrading activity, matrix metalloproteinase (MMP) activity, and the level of TIMP secretion in the culture media. PAL significantly reduced the casein-degrading activity and further increased TIMP secretion under hrIL-1 alpha stimulation. Phorbol myristate acetate (PMA) also increased the level of TIMP secretion, and staurosporine, a specific inhibitor of protein kinase C (PKC), reduced the TIMP secretion to the control level under hrIL-1 alpha or PMA stimulation. Furthermore, PAL showed a significant increase following treatment with a low concentration of PMA which alone did not increase TIMP production. These findings suggest that the activation of the PKC pathway plays an important role in TIMP production and that PAL increases the level of TIMP production through an additive or synergistic effect with the activation of the PKC pathway. In conclusion, these findings demonstrate that the inhibition of the MMP activity and the increase of TIMP production by PAL contribute to the inhibition of PG depletion in a primary chondrocyte culture from bovine nasal septum cartilage.
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PMID:Effect of a benzylidene derivative, novel antirheumatic agent, on the production of tissue inhibitor of metalloproteinases. 814 18

Low (2 ng/ml) and high (40 ng/ml) concentrations of the protein kinase C (PKC) activator phorbol-12-myristate-13-acetate (PMA) were tested for their effect on cultured bovine articular chondrocyte proteoglycan synthesis. In addition, we examined whether PMA could reverse interleukin 1 (IL-1) and nonsteroidal antiinflammatory drug (NSAID) induced inhibition of proteoglycan synthesis. Low concentrations of PMA stimulated proteoglycan synthesis by chondrocytes. High concentrations of PMA had no significant effect. IL-1 and high concentrations of NSAID inhibited proteoglycan production by chondrocytes. Low concentrations of PMA completely reversed IL-1 induced inhibition but did not significantly alter proteoglycan synthesis in the presence of antiinflammatory drugs. On the other hand, high concentrations of PMA had little effect on IL-1 induced inhibition but significantly potentiated the suppression of proteoglycan synthesis induced by 2 of the NSAID tested, indomethacin and flurbiprofen. Assay of PKC activity indicated that PKC levels were down-regulated by high but not by low concentrations of PMA. This suggests that different mechanisms were regulating the effects of low and high concentrations of PMA on proteoglycan synthesis. Although IL-1 and high concentrations of NSAID both suppress proteoglycan synthesis by chondrocytes, their different responses when coincubated with PMA suggest that they act through different pathways.
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PMID:Effect of phorbol ester on the inhibition of proteoglycan synthesis induced by interleukin 1 and antiinflammatory drugs. 829 87

NG2 is a chondroitin sulfate proteoglycan that is expressed on dividing progenitor cells of several lineages including glia, muscle, and cartilage. It is an integral membrane proteoglycan with a core glycoprotein of 300 kDa. In the present study we have characterized three molecular forms of the NG2 core protein expressed by different cell lines. Many cell lines that express the full length 300-kDa NG2 core protein also release a 290-kDa form into the medium. This species lacks the cytoplasmic domain but contains almost the entire ectodomain. Two core protein species, the intact 300-kDa form and a truncated 275-kDa form, are expressed at the surface of an NG2-transfected cell line U251NG52. The 275-kDa species lacks the cytoplasmic domain and at least 64 amino acids of the ectodomain. Mild trypsinization of B49 cells also generates the 275-kDa species, suggesting that this component is produced by proteolysis of the 300-kDa form. Conversion of the 300-kDa species to the 275-kDa form in U251NG52 cells is stimulated by reagents such as phorbol esters, which activate protein kinase C. Phorbol esters are also known to induce expression of metalloproteinases such as collagenase and stromelysin, which could be responsible for cleavage of the 300-kDa core protein. Although B49 cells do not spontaneously produce the truncated 275-kDa species, use of monoclonal antibodies against NG2 to block the interaction between NG2 and type VI collagen results in the appearance of the 275-kDa component in these cells. Thus the interaction between NG2 and type VI collagen, which contains a Kunitz-type proteinase inhibitor sequence in the alpha 3 chain, may protect the proteoglycan against proteolysis. This is consistent with the observed deficiency of U251NG52 cells in anchoring type VI collagen at the surface.
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PMID:Generation of truncated forms of the NG2 proteoglycan by cell surface proteolysis. 859 Aug 8

Studies of neural, hepatic, and other cells have demonstrated that in vitro ethanol exposure can influence a variety of membrane-associated signaling mechanisms. These include processes such as receptor-kinase phosphorylation, adenylate cyclase and protein kinase C activation, and prostaglandin production that have been implicated as critical regulators of chondrocyte differentiation during embryonic limb development. The potential for ethanol to affect signaling mechanisms controlling chondrogenesis in the developing limb, together with its known ability to promote congenital skeletal deformities in vivo, prompted us to examine whether chronic alcohol exposure could influence cartilage differentiation in cultures of prechondrogenic mesenchyme cells isolated from limb buds of stage 23-25 chick embryos. We have made the novel and surprising finding that ethanol is a potent stimulant of in vitro chondrogenesis at both pre- and posttranslational levels. In high-density cultures of embryonic limb mesenchyme cells, which spontaneously undergo extensive cartilage differentiation, the presence of ethanol in the culture medium promoted increased Alcian-blue-positive cartilage matrix production, a quantitative rise in 35SO4 incorporation into matrix glycosaminoglycans (GAG), and the precocious accumulation of mRNAs for cartilage-characteristic type II collagen and aggrecan (cartilage proteoglycan). Stimulation of matrix GAG accumulation was maximal at a concentration of 2% ethanol (v/v), although a significant increase was elicited by as little as 0.5% ethanol (approximately 85 mM). The alcohol appears to directly influence differentiation of the chondrogenic progenitor cells of the limb, since ethanol elevated cartilage formation even in cultures prepared from distal subridge mesenchyme of stage 24/25 chick embryo wing buds, which is free of myogenic precursor cells. When limb mesenchyme cells were cultured at low density, which suppresses spontaneous chondrogenesis, ethanol exposure induced the expression of high levels of type II collagen and aggrecan mRNAs and promoted abundant cartilage matrix formation. These stimulatory effects were not specific to ethanol, since methanol, propanol, and tertiary butanol treatments also enhanced cartilage differentiation in embryonic limb mesenchyme cultures. Further investigations of the stimulatory effects of ethanol on in vitro chondrogenesis may provide insights into the mechanisms regulating chondrocyte differentiation during embryogenesis and the molecular basis of alcohol's teratogenic effects on skeletal morphogenesis.
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PMID:Ethanol exposure stimulates cartilage differentiation by embryonic limb mesenchyme cells. 860 6

Hyperglycemic conditions are known to increase mRNA and protein levels of several extracellular matrix molecules in cultured mesangial cells, but accompanying increases in proteoglycan mRNA have not been found, and there are discrepant reports of normal or decreased proteoglycan synthesis with or without undersulfation in diabetic kidneys and hyperglycemic cultures. We examined the effects in proliferating cells of glucose on [35S]Sulfate incorporation into heparan and dermatan sulfates and on mRNA levels of decorin, biglycan, and basement membrane perlecan. In both mesangial cells and vascular smooth muscle cells, 30 mmol/L glucose caused a decrease of 15% to 25% in the amount of sulfate incorporated into each proteoglycan in cultures confluent for 1 to 4 days, compared with 10 mmol/L glucose. The effect showed no specificity for the class of proteoglycan and was not a consequence of changes in total protein synthesis, which increased, or cell proliferation, which was unaffected. No decrease in charge density of any of the proteoglycan fractions was observed by ion-exchange chromatography. Therefore, the decrease in labeling was due to a decrease in synthesis and not undersulfation. mRNA levels for biglycan and perlecan increased slightly and transiently, and these changes cannot account for the decreased synthesis. Decorin mRNA was detected only in smooth muscle cells, where it and biglycan were differentially affected by glucose, apparently at the transcriptional level; stabilities of the two messages were unaffected by glucose. Although transforming growth factor-beta 1 (TGF-beta 1) mRNA levels increased in response to glucose, the cytokine did not appear to regulate proteoglycan synthesis, because structural changes in proteoglycans elicited by addition of TGF-beta 1 to the culture medium did not occur in the hyperglycemic cultures. On the other hand, inhibition and downregulation of protein kinase C (PKC), while decreasing net sulfate incorporation into mesangial cell proteoglycans, prevented the effect of high glucose. We conclude that a high glucose concentration causes a general decrease in the synthesis of all classes of proteoglycans at a posttranscriptional level, and can do so without affecting the charge density of individual proteoglycan molecules.
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PMID:Posttranscriptional effects of glucose on proteoglycan expression in mesangial cells. 878 2

Platelet-derived growth factor (PDGF) stimulates not only the proliferation and migration of arterial smooth muscle cells (ASMCs), but also the transcription, translation, and posttranslational processing of versican, a large chondroitin sulfate proteoglycan present in the extracellular matrix of blood vessels. PDGF receptor tyrosine kinase activity is required for signaling events associated with mitogenic and motogenic stimulation of cells by PDGF. Therefore, we have asked if inhibiton of tyrosine kinase activity by genistein also blocks the stimulation of both versican core protein synthesis and glycosaminoglycan (GAG) chain modifications induced by PDGF in ASMCs. The tyrosine kinase inhibitor, genistein, in a dose-dependent manner, reversibly inhibits PDGF-stimulated ASMC cell proliferation and RNA and core protein expression of versican, without affecting the expression of decorin and biglycan. In contrast, genistein does not affect the increase in GAG chain elongation that is induced by PDGF. This suggests that different aspects of the biosynthesis of versican are differentially regulated. To determine if such differential regulation involves downstream activation of protein kinase C, ASMCs were treated with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) to directly activate this kinase. In comparison to PDGF stimulation, TPA has little effect on expression of versican mRNA expression, nor does TPA stimulate ASMC cell proliferation. However, like PDGF, TPA increases [35S]sulfate incorporation into proteoglycans and GAG chain elongation. These results indicate that PDGF-induced GAG chain elongation, which is not inhibited by genistein treatment and is stimulated by protein kinase C activation, involves signaling pathways different from those that regulate PDGF-stimulated versican mRNA and protein expression.
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PMID:Genistein selectively inhibits platelet-derived growth factor-stimulated versican biosynthesis in monkey arterial smooth muscle cells. 905 68


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