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)

An initial event in T cell activation is the specific adherence of T cells via their T cell receptor to the MHC peptide complex. We have studied this adherence by incubating T cells with preformed HLA DR4Dw4 peptide complexes attached to a solid support. Adherence of sodium 51Cr-labeled T cell clones specific for the influenza hemagglutinin peptide, HA 307-319, was maximal after 15 min and was specific for the HLA DR4Dw4-HA 307-319 complex. The binding was temperature dependent and could be blocked with azide or protein kinase C inhibitors, indicating that for adherence the T cells need to be metabolically active and have a functioning protein kinase C pathway. The adherence could be blocked with CD4- or CD3-reactive murine mAb, suggesting that the TCR and CD4 molecules work in concert to induce strong adherence to the HLA DR4Dw4-HA 307-319 complex. A subsequent event in T cell activation is proliferation, which is thought to need additional proteins such as IL-1 or other adhesion molecules. MHC peptide complexes coated on microtiter plates also induced proliferation in the human T cell clones. Removal of any monocytes by treatment of human T cell clones with anti-CD14 in conjunction with C, followed by purification over a nylon wool column, did not abrogate proliferation. After prolonged culture of the T cell clones in plates coated with peptide-pulsed HLA DR4Dw4 in the presence of IL-2, the T cell clones continued to proliferate in response to peptide. These results suggest that human T cell clones do not require a second signal from a monocyte or other APC to proliferate.
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PMID:Purified HLA class II peptide complexes can induce adherence and activation of peptide-specific human T cell clones. 153 49

We used the U937 cell line to analyze CD14, CD11/CD18, HLA class-I and DR antigen expression during PMA-induced differentiation. Treatment of U937 cells with PMA markedly increased CD14, CD11a, CD11b and CD18 antigen expression, and slightly increased CD11c expression. Protein kinase C may play a major role in regulating the expression of these antigens. The protein kinase inhibitor H7 abrogated the inductive effect of PMA. Calcium ionophore, when added alone or in the presence of PMA, had no effect. The inhibitory effect of the calcium antagonist verapamil, EGTA, and of chlorpromazine, an antagonist of calcium-binding proteins, supports a role for calcium-dependent protein kinase C in the up-regulation of CD14 and CD11/CD18 surface expression. The specific calmodulin inhibitors R24571 and W7 had no effect on antigen expression. Our findings suggest that protein kinase C activation is an important step in the PMA-induced differentiation of U937 cells.
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PMID:Protein kinase C-mediated regulation of the expression of CD14 and CD11/CD18 in U937 cells. 168 74

The human monoblast cell line, U937, was employed to elucidate early events associated with differentiation induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) and 1,25-dihydroxy-Vitamin D3 (VD3). Exposure of cells to a combination of GM-CSF and VD3 resulted in an up-regulation of c-fos mRNA within 1 h and a marked down-regulation of c-myc mRNA by 24 h and this was associated with a shift of cell population from the S phase to the G0 + G1 phase of the cell cycle by 18%. This was followed by a marked enhancement of monocyte-associated cell surface antigens [OKM1 (CD11b), LeuM3 (CD14), M77.7], as determined by monoclonal antibodies and flow cytometry. Functional characteristics such as nitroblue-tetrazolium reduction, alpha-naphthyl butyrate esterase activity, and phagocytic capability occurred. Cells treated with GM-CSF or VD3 alone showed only minor changes. These results demonstrate a potent synergistic effect of GM-CSF and VD3 on induction of U937 differentiation. This differentiation was partially blocked by H7, a protein kinase C (PKC) inhibitor. Changes in c-myc and c-fos mRNA expressions and a shift in cell cycle were shown to be early events in this process.
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PMID:Mechanisms of differentiation of U937 leukemic cells induced by GM-CSF and 1,25(OH)2 vitamin D3. 186 27

To evaluate the role of the high-affinity monocyte receptor for lipopolysaccharide (LPS), CD14, in the process of tolerance to LPS, the human monocytic cell line Mono-Mac-6 was cultured in the absence or presence of different amounts of LPS. The kinetics of CD14 modulation in these cells showed an initial 4-day period characterized by increased cell-surface expression, rate of biosynthesis (peaking at 48 hr) and release of its soluble forms (sCD14) which correlated with the amount of LPS in the culture. At this time, tolerance to LPS was already established, as measured by tumour necrosis factor-alpha (TNF-alpha) induction, it was LPS dose dependent and persisted up to 15 days. LPS also reduced the cell proliferation rate in a dose-dependent manner. After 8 days and up to 15 days, the CD14 biosynthesis, cell-surface expression and release of sCD14 inversely correlated with the level of LPS in the culture. The 48-hr LPS-pretreated cells showed a slightly decreased CD14 affinity for LPS, a relative high number of CD14 molecules per cells, and desensitization also to a phorbol 12-myristate 13-acetate (PMA) challenge. An anti-CD14 monoclonal antibody (mAb) protected the cells from tolerization when added at the beginning of culture, as revealed by challenge with LPS and PMA. The data indicate that in this model tolerization to LPS (1) precedes CD14 down-modulation, (2) operates by alteration of the receptor affinity for LPS and by a mechanism which affects a protein kinase C (PKC)-dependent signalling pathway, and (3) that CD14 plays a critical role in the establishment of tolerance to LPS. In addition, analysis of the data suggests the existence of a PKC-independent signalling pathway for LPS tolerization and a CD14-independent mechanism for establishing tolerance.
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PMID:CD14 and tolerance to lipopolysaccharide: biochemical and functional analysis. 750 90

Bryostatin 5 is a macrocyclic lactone which activates protein kinase C (PKC). PKC activation has been implicated in leukemic cell differentiation. We have examined the effect of PKC activation by bryostatin 5 on human acute myeloid cell differentiation in the presence and absence of vitamin D3. In vitro treatment of 20 patient samples of acute myeloid leukemias in a 4 days culture system with 10 nM bryostatin 5 induced strongly adherent macrophage-like cells in all cases. Bryostatin 5 induced a significant (p = 0.00006) increment in esterase activity in a majority of the samples, which was further enhanced by vitamin D3. CD14 expression was significantly (p = 0.035) enhanced with the combination of bryostatin 5 and vitamin D3. Nitroblue tetrazolium (NBT) reducing ability was, however, nearly abolished (p = 0.0007). A loss of CD34 expression occurred during cell culture; this loss was enhanced by vitamin D3, but prevented partly by bryostatin 5. Together these findings indicate that exposure to bryostatin 5 leads to a strong macrophage-like cell differentiation in human myeloid leukemia and that VD3 has an additional effect. These findings strengthen the potential role of bryostatins as possible antileukemic agents.
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PMID:The differentiation inducing effect of bryostatin 5 on human myeloid blast cells is potentiated by vitamin D3. 750 34

Bacterial LPS stimulates human monocytes to secrete inflammatory cytokines, which are involved in several disease processes. However, the mechanism of LPS activation of cytokine expression and secretion is not completely understood. In this study, we investigated the signal transduction pathways involved in LPS-stimulated TNF-alpha and IL-1 beta secretion. TNF-alpha and IL-1 beta secretion were completely blocked by protein kinase C (PKC) and cyclic nucleotide-dependent protein kinase inhibitor, H-7, but were not affected by H-89, a specific cyclic nucleotide-dependent protein kinase inhibitor. In addition, LPS was found to induce activation of PKC, reaching maximal activity at 30 min and returning to unstimulated levels after 60 min. LPS stimulation only slightly increased intracellular levels of diacylglycerol, the natural activator of PKC, and pretreatment of monocytes with the diacylglycerol-kinase inhibitor, R59022, did not affect LPS-stimulated TNF-alpha secretion. LPS-induced PKC activation was found not to be affected by blocking of the LPS receptor, CD14, with mAb or by inhibition of protein tyrosine kinase with herbimycin A. However, these agents suppressed LPS-induced TNF-alpha secretion and TNF-alpha mRNA accumulation. The results suggest that TNF-alpha and IL-1 beta secretion after LPS stimulation of human monocytes requires the activation of protein tyrosine kinase and PKC, upstream to the activation of gene transcription. The activation of PKC by LPS is probably mediated by a diacylglycerol-independent pathway.
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PMID:Involvement of protein kinase C and protein tyrosine kinase in lipopolysaccharide-induced TNF-alpha and IL-1 beta production by human monocytes. 751 14

To investigate mechanisms of mononuclear phagocyte cell signaling, the effects of bacterial LPS on protein kinase activities in normal human peripheral blood monocytes were examined. Incubation of intact monocytes with LPS brought about time- and concentration-dependent increases in myelin basic protein (MBP) phosphotransferase activity in high speed supernatants of cell lysates. Anion-exchange chromatography on Mono Q demonstrated that LPS treatment resulted in two principal peaks of stimulated MBP kinase activity. Evidence was obtained to indicate that the first eluted peak of MBP kinase activity is accounted for by p42 and p44 mitogen-activated protein (MAP) kinases. Thus, 1) MBP kinase activity within peak 1 was quantitatively precipitated by anti-MAP kinase Abs, 2) the enzyme effectively phosphorylated a specific peptide substrate, 3) peak 1 contained proteins of subunit size M(r) 42,000 and M(r) 44,000 that reacted specifically with anti-MAP kinase Abs, and that 4) were recognized by anti-phosphotyrosine Abs only after stimulation of cells with LPS. Studies of the second peak of LPS-stimulated MBP kinase activity indicate that it is an isoform of protein kinase C (PKC) because: 1) enzyme activity was quantitatively immunoprecipitated by anti-PKC Abs, 2) the activity of the enzyme was potently and selectively inhibited by a specific peptide modeled on the autoinhibitory domain of PKC, and 3) the presence of a protein of subunit size M(r) 80,000 recognized by anti-PKC Abs. Because the second peak of MBP kinase activity (like the first) was active in the absence of added calcium and in the presence of 2 mM EGTA, it appears to be a type II, calcium-independent isoform of PKC. Abs to CD14 completely abrogated LPS-induced activation of both Mono Q peaks of MBP phosphotransferase activity. These results indicate that LPS coordinately activates both an apparently calcium-independent PKC and MAP kinase in mononuclear phagocytes and these responses appear to be initiated by signaling through the cell surface receptor, CD14.
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PMID:CD14-dependent activation of protein kinase C and mitogen-activated protein kinases (p42 and p44) in human monocytes treated with bacterial lipopolysaccharide. 752 66

We examined the expression of eosinophilic granules, esterase activity and CD14 in a human eosinophilic cell line, EoL-1. Unstimulated EoL-1 cells were weakly positive for nonspecific esterase, but negative for surface CD14, and contained a few eosinophilic granule-positive cells. A combination of G-CSF and TNF-alpha increased the eosinophilic granule-containing cells, but failed to increase esterase activity or CD14 expression. IFN-gamma alone or in combination with TNF-alpha enhanced nonspecific esterase activity but failed to induce CD14 expression or increase eosinophilic granule-containing cells. dbcAMP increased eosinophilic granule-containing cells, nonspecific esterase activity and CD14 expression. Specific esterase activity was not detected in any circumstances. EoL-1 cells fractionated by density gradients or CD14 expression showed nonspecific esterase activity and CD14 expression in both the eosinophilic granule-positive and negative cell populations. Forskolin and butyrate had a synergistic effect on CD14 induction and protein kinase A was suggested to play a role in dbcAMP-induced CD14 expression. A protein kinase C activator, phorbol 12-myristate 13-acetate, did not increase eosinophilic granules, nonspecific esterase activity or CD14 expression in EoL-1 cells. The results show that EoL-1 cells can express nonspecific esterase and CD14, but the expression is not necessarily restricted to cells which have differentiated into the monocyte/macrophage lineage.
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PMID:Induction of eosinophilic granules, nonspecific esterase activity and CD14 expression in the human eosinophilic leukemia cell line, EOL-1. 752 48

1. In RAW 264.7 macrophages, lipopolysaccharide (LPS) and gamma-interferon (IFN gamma) alone or in combination stimulated the induction of nitric oxide synthase (iNOS) activity and increased the expression of the 130 kDa isoform of NOS. 2. LPS-induced NOS activity was reduced by incubation with CD14 neutralising antibodies and abolished in macrophages deprived of serum. 3. LPS stimulated a small increase in protein kinase C (PKC) activity in RAW 264.7 macrophages which was dependent on the presence of serum. However, IFN gamma did not potentiate LPS-stimulated PKC activity. 4. The protein kinase C inhibitor, Ro-318220, abolished both LPS- and IFN gamma-stimulated protein kinase C activity and the induction of NOS activity. 5. LPS- and IFN gamma-induced NOS activity was reduced by the tyrosine kinase inhibitor genestein. Genestein also reduced LPS-stimulated protein kinase C activity but did not affect the response to the protein kinase C activator, tetradecanoylphorbol acetate (TPA). 6. Nicotinamide, an inhibitor of poly-ADP ribosylation, abolished LPS- and IFN gamma-induced NOS activity. 7. Brefeldin A, an inhibitor of a factor which stimulates nucleotide exchange activity on the 21 kDa ADP-ribosylation factor, ARF, reduced LPS- and IFN gamma-induced NOS activity by approximately 80%. 8. These results suggest the involvement of protein kinase C, tyrosine kinase and poly-ADP ribosylation pathways in the regulation of the induction of nitric oxide synthase in RAW 264.7 macrophages by LPS and IFN gamma.
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PMID:Protein kinase C and tyrosine kinase pathways regulate lipopolysaccharide-induced nitric oxide synthase activity in RAW 264.7 murine macrophages. 753 21

Previously, we reported that preexposure of proteose peptone-elicited murine peritoneal exudate macrophages (P-PEM) to a low dose of LPS suppressed the expression of TNF-alpha mRNA, but not of IL-1 beta mRNA, induced by a second round of LPS exposure. To elucidate the mechanisms underlying this hyporesponsiveness to LPS, we focused on two molecules: nuclear factor (NF)-kappa B and CD14. Activation of NF-kappa B induced by a second round of LPS was suppressed in LPS-primed P-PEM much like the suppression of TNF-alpha mRNA expression. However, protein kinase C (PKC), a candidate as an activator of NF-kappa B, was not desensitized by LPS priming. LPS-induced TNF-alpha production was not affected by depletion of PKC, and LPS could not induce translocation of PKC. CD14 expression showed no significant difference between control and primed P-PEM. In contrast with J774.1 cells and thioglycolate medium-elicited macrophages (T-PEM), P-PEM exhibited serum-independent TNF-alpha production, and a polyclonal Ab to murine CD14 had no inhibitory effect on the LPS-induced TNF-alpha production by P-PEM. These results suggest that priming by LPS causes blockage at an early step, at least before the activation of NF-kappa B, in the LPS signal transduction pathway, but not at the expression of CD14. Our results also suggest that, in P-PEM, in contrast to J774.1 cells and T-PEM, neither PKC nor CD14 is involved in the LPS-induced activation and suppression of TNF-alpha gene expression.
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PMID:Suppression of TNF-alpha mRNA expression in LPS-primed macrophages occurs at the level of nuclear factor-kappa B activation, but not at the level of protein kinase C or CD14 expression. 753 82


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