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

We examined the levels of protein kinase C (PKC) activity and the expressions of its three major isozymes, designated types I (gamma), II (beta), and III (alpha), in the cytosol and particulate fractions of cells from patients with acute myelogenous leukemia (AML), acute lymphocytic leukemia (ALL), and chronic lymphocytic leukemia (CLL), in an attempt to elucidate the cell type- or lineage-specific expression of these isozymes. The levels of PKC activities in the cytosol and particulate fractions from AML cells were higher than those from ALL or CLL cells. The average PKC activities of AML cells, ALL cells, and CLL cells were 18.7, 12.2, and 11.3 pmol/min/10(8) cells, respectively, in the cytosol fractions and 4.4, 3.1, and 2.6 pmol/min/10(8) cells, respectively, in their particulate fractions. M1 cells (French-American-British classification) and AML cells with T-lymphocyte-associated surface antigens, such as CD2 and CD7, had significantly lower PKC activities among AML cells. Immunoblot analyses using monoclonal antibodies against each isozyme revealed that all three isozymes were broadly distributed on leukemic cells with considerable variability in the level of expression. All lymphoid leukemic cells expressed PKC-gamma in the cytosol fractions, albeit a minor component; however, this type was observed in cells from only half the number of AML patients. Those AML cells with cytosolic PKC-gamma usually expressed lymphoid surface antigens, such as CD2, CD7, and CD19. On the other hand, cytosolic PKC-beta and PKC-alpha were commonly observed in all types of leukemic cells. AML cells expressed these two types at almost equal levels, but in lymphoid cells, expressions of PKC-beta were usually more abundant than those of PKC-alpha. These data suggest that AML cells with lymphoid antigens might have a lower PKC activity but more predominant expression of cytosolic PKC-gamma than the usual AML cells.
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PMID:Expression of three major protein kinase C isozymes in various types of human leukemic cells. 186 47

Prolonged activation of protein kinase C (PKC) types alpha and beta by tumor-promoting phorbol esters leads to desensitization of the phorbol ester response, downregulation of protein kinase C activity and depletion of the protein kinase C polypeptide. When the gamma isoenzyme of PKC is transiently expressed in COS-1 cells and exposed to phorbol esters, PKC-Gamma is downregulated in COS cells although these cells do not normally express this subtype. A point mutation in the putative ATP-binding site (Lys-380----Met-380) of the protein kinase C gamma isoenzyme which results in a kinase-deficient enzyme does not interfere with this downregulation. Our results suggest that autophosphorylation or constitutive signalling through the protein kinase C-gamma kinase domain is not a prerequisite for downregulation of PKC activity.
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PMID:Downregulation of protein kinase C-gamma is independent of a functional kinase domain. 190 48

The appearance of the biphasic insulin secretory response several days after birth suggests that maturation of a critical step in stimulus-secretion coupling occurs during the early neonatal period. To clarify the role of protein kinase C (PKC) during this time, we examined the pancreatic islets of adult, 3-day neonatal, and 19-day fetal rats for the presence of different PKC isoenzymes. Western-blot analysis of islet extracts showed the presence of PKC isoforms in both adult and neonatal tissues. Immunocytochemistry of adult islets revealed a differential expression in islet cell types. PKC-alpha was found only in beta-cells, PKC-gamma in alpha-cells, and PKC-epsilon in delta-cells and vascular walls. Immunoreactivity for PKC-beta was not detected in any cell type. All three isoenzymes were also present in neonatal islets; however, in contrast to adult tissue, immunoreactivity for either PKC-alpha or PKC-gamma was present in relatively few cells. There was no apparent immunoreactivity for PKC-alpha or PKC-gamma in fetal islets, although these tissues contained strong staining for insulin and glucagon. These data show that three of the PKC isoforms are restricted to a particular islet cell type, where they may play a unique role in the secretion of a specific hormone. Moreover, our results demonstrate that these enzymes, especially PKC-alpha, appear during the early neonatal period. This age-dependent expression may be linked to the development of the biphasic insulin release response.
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PMID:Age-dependent expression of protein kinase C isoforms in rat islets. 193 8

The molecular pathways that are responsible for delivering the proliferative signals from the cell surface to the nucleus in T lymphocytes are still unresolved, but recent data implicates protein kinase C (PKC) involvement in the TCR signaling pathway. To further address the role of PKC in T cell activation, the effects of high level expression of the PKC-gamma isoenzyme in murine CTL clones were examined. Unlike the parental cells that required periodic Ag stimulation for cell activation and growth, cells expressing a retrovirally transduced PKC-gamma gene propagated in culture independent of the need for Ag stimulation, although maintaining identical functional specificity to the parental CTL. Constitutive PKC-gamma expression may therefore mimic physiologic PKC activation, thereby abrogating the requirement for TCR-Ag interaction in T cell activation.
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PMID:Retroviral transduction of protein kinase C-gamma into cytotoxic T lymphocyte clones leads to immortalization with retention of specific function. 199 61

In this study we examined the effects of insulin on protein kinase C (PKC) activity in cultured fetal chick neurons. PKC activity, measured as 32P incorporation into histone H1 in the presence of calcium (500 microM), phosphatidylserine (100 micrograms/ml), and diolein (3.3 micrograms/ml) minus the incorporation in the presence of calcium alone, was detected in neuronal cytosolic (207 +/- 33 pmol/min/mg) and membrane (33 +/- 8 pmol/min/mg) fractions. Insulin added to intact neurons increased the activity of PKC in both cytosolic and membrane fractions by about 40%. Neurons preincubated with cycloheximide (10 micrograms/ml) 30 min prior to insulin treatment showed the same degree of stimulation of PKC activity by insulin. The activation of PKC was maximal within 5-10 min of insulin exposure and was sustained for at least 60 min. Insulin stimulated PKC in a dose-dependent manner, with a maximal response obtained at 100 ng/ml. Addition of phosphatidylserine and diolein to neuronal cell extracts resulted in the phosphorylation of four major cytosolic proteins (70, 57, 18, and 16 kDa) and one major membrane protein (75 kDa). Phosphorylation of all five proteins was increased 2-fold in extracts from insulin-treated neurons. Immunoblot analysis of whole cell extracts using antibodies against PKC-alpha, PKC-beta, PKC-gamma, PKC-delta, and PKC-epsilon revealed that cultured fetal chick neurons contained only one of these PKC isoforms, the epsilon-isoform. The enzyme was mostly cytosolic. Insulin had no effect on either the amount of distribution of PKC-epsilon in cultured neurons but induced a small change in the mobility of PKC-epsilon on sodium dodecyl sulfate-polyacrylamide gels. When assay conditions were designed to measure specifically the activity of PKC-epsilon, using a synthetic peptide substrate in the absence of calcium, activity was 50 +/- 12% higher in insulin-treated cells (p less than 0.005). PKC activity in control and insulin treated-neurons was almost completely inhibited when assays included a peptide identical to the pseudo-substrate binding site of PKC-epsilon. We conclude that PKC-epsilon is the major PKC isoform present in cultured fetal chick neurons. Insulin stimulates PKC-epsilon activity by a mechanism that does not involve translocation of the enzyme from cytosol to membrane.
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PMID:Insulin stimulates the activity of a novel protein kinase C, PKC-epsilon, in cultured fetal chick neurons. 220 68

We have expressed rat protein kinase C-gamma in insect cells using a baculovirus vector. The yield of expressed protein kinase C-gamma is about 4% of total protein. The recombinant protein shows a prominent band at about 80 kDa on SDS-polyacrylamide gels, which can be identified as protein kinase C-gamma by Western blotting using monoclonal antibodies against protein kinase C-gamma. Upon incubation with [gamma-32P]ATP and in the presence of Ca2+, phosphatidylserine and diacylglycerol this protein autophosphorylates. Its enzyme activity shows the characteristic properties of mammalian protein kinase C.
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PMID:High-efficiency expression of rat protein kinase C-gamma in baculovirus-infected insect cells. 226 45

The isoform pattern of protein kinase C (PKC) was examined in wild-type and Adriamycin-resistant (HL-60/AR) HL-60 leukemia cells. Analyses were carried out by immunoblotting with mouse monoclonal antibodies against PKC-alpha and PKC-beta and a rabbit polyclonal antibody against the variable (V3) region of PKC-gamma. HL-60/AR cells contained an equivalent level of PKC-alpha and a lower amount of PKC-beta than HL-60 cells. In contrast, only HL-60/AR cells contained PKC-gamma. These results indicate that the regulation of this family of isoenzymes is altered in drug-resistant cells.
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PMID:Protein kinase C-gamma is present in adriamycin resistant HL-60 leukemia cells. 230 37

The present study has characterized several aspects of the mouse epidermal protein kinase C (PKC) system and compared phorbol ester-sensitive and -resistant mice. Protein immunoblots of partially purified epidermal PKC preparations from SENCAR and C57BL/6 mice indicated the presence of the gamma-, beta-, and alpha-isozymes of PKC in both strains. Hydroxylapatite chromatography profiles of epidermal PKC isozymes from SENCAR and C57BL/6 mice revealed three major peaks of PKC activity eluting in fractions similar to those observed in chromatograms of brain tissue and corresponding to PKC-gamma, -beta, and -alpha. Further analyses of hydroxylapatite chromatography fractions revealed that PKC-gamma and -beta were present in approximately similar proportions and were much more abundant than PKC-alpha. This distribution of epidermal PKC isozymes was similar in both strains. After a single topical application of 3.4 nmol 12-O-tetradecanoylphorbol-13-acetate (TPA) to SENCAR mouse epidermis, total PKC activity in the cytosol fraction decreased rapidly to about 50% of control within 15 min and was accompanied by an increase (approximately 150% of control) of PKC activity in the membrane fraction. At 4 h, PKC activities were significantly lower than the control levels and remained downregulated through 96 h with a maximal decrease (to approximately 25-30% of the control) in both cytosol and membrane fractions at h. PKC activity returned to control levels by 168 h. Ca++/phospholipid-independent kinase activity was the same as control levels at 15 min, 1 h, and 4 h after TPA treatment but was elevated above control levels at 24 h, 48 h, and 96 h, and by 168 h returned essentially to control levels. No differences were found in the magnitude or kinetics of TPA-induced translocation and downregulation of total PKC or appearance of Ca++/phospholipid-independent kinase activity between SENCAR, DBA/2, and C57BL/6 mice. Scatchard analyses using a two binding site model revealed that the apparent Kd and Bmax values for binding of PDBu to epidermal cytosol and membrane fractions were similar between SSln, SENCAR, DBA/2, and C57BL/6 mice. The present results demonstrate for the first time that mouse epidermis contains significant amounts of the three major PKC isozymes that are present in brain, especially PKC-gamma. In addition, topical application of a promoting dose of TPA did not lead to complete loss of PKC activity in either the membrane or cytosol fractions of mouse epidermis. In conclusion, no differences were observed between phorbol ester-sensitive and -resistant mice in any aspect of epidermal PKC examined.
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PMID:Partial characterization of epidermal protein kinase C in mice sensitive or resistant to phorbol ester. 237 71

Four monoclonal antibodies (mAbs), derived from high-responder Biozzi mice immunized with purified protein kinase C, were selected by ELISA and further characterized by immunoblot: 3G12, 5A2, 36G9 are of isotype gamma 1, kappa and 15G4 is of isotype gamma 2b, kappa. Competition analysis between 15G4 and the three other mAbs showed that 15G4 and 3G12 are directed against either the same or overlapping epitope(s). All four mAbs are specific for the bovine gamma isoform of protein kinase C and cross-react with protein kinase C gamma from a variety of animal species. Immunoblot analysis of protein kinase C tryptic fragments revealed that the mAbs recognize the regulatory domain and not the catalytic domain. Two of the mAbs, 36G9 and 5A2, inhibit protein kinase C gamma cofactor-dependent activity (80% and 50% respectively). Consistent with the epitope mapping, none of mAbs inhibit the cofactor-independent catalytic activity of protein kinase C gamma. Competition analysis between these mAbs and phosphatidylserine, 12-O-tetradecanoylphorbol 13-acetate and Ca2+ showed that 36G9 and 5A2 block cofactor binding to protein kinase C gamma. These four mAbs thus interact with at least three distinct epitopes in the regulatory domain of protein kinase C gamma.
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PMID:Monoclonal antibodies to protein kinase C gamma. Functional relationship between epitopes and cofactor binding sites. 247 72

An early consequence of stimulation of T cells via their Ag receptor is the activation of protein kinase C (PKC). It has recently been shown that PKC activity resides in a family of homologous proteins. Inasmuch as T cells are phenotypically and functionally heterogeneous, we examined the possibility that this heterogeneity may be reflected in differential expression of message for PKC isoenzyme genes. RNA from six leukemic T cell lines was probed for PKC-alpha, -beta, and -gamma message before and after activation. These studies revealed significant differences among these lines. None expressed mRNA for PKC-gamma. Whereas all cells possessed message for PKC-alpha, there was consistent variability in the level expressed. The greatest heterogeneity was seen with PKC-beta. Two cell lines, HUT 78 and HPB-ALL, did not hybridize with the beta probe under any conditions tested. We subsequently used these PKC-beta negative cells to study the role of this isoenzyme in mediating some of the effects seen with phorbol esters that directly bind to and activate PKC. Our results indicate that PKC-beta, which is expressed in some T cells, is not necessary for PMA-induced CD3 or CD4 internalization, IL-2 production, or acquisition of the p55 chain of the IL-2 receptor.
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PMID:Heterogeneity of protein kinase C isoenzyme gene expression in human T cell lines. Protein kinase C-beta is not required for several T cell functions. 278 92


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