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)

Our first goal was to determine whether acute hyperglycemia alters endothelium-dependent reactivity of rat cerebral arterioles. Our second goal was to investigate a possible mechanism for impaired reactivity during acute hyperglycemia. Diameter of pial arterioles was measured during suffusion with ADP, acetylcholine, histamine, N-methyl-D-aspartate (NMDA), and nitroglycerin before and during application of a suffusate containing D-glucose (5, 10, 20, and 25 mM). ADP, acetylcholine, histamine, NMDA, and nitroglycerin produced dose-related vasodilation before application of D-glucose. Vasodilatation in response to the agonists was not altered by 5 and 10 mM D-glucose. In contrast, vasodilatation in response to ADP, acetylcholine, histamine, and NMDA was impaired during application of 20 and 25 mM D-glucose. Dilatation in response to nitroglycerin was not altered. Application of the protein kinase C inhibitor calphostin C (1.0 nM) or chelerythrine (10 nM) restored endothelium-dependent vasodilatation during application of 25 mM D-glucose. Thus acute hyperglycemia impairs endothelium-dependent responses of cerebral arterioles via the activation of protein kinase C.
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PMID:Acute effects of glucose on reactivity of cerebral microcirculation: role of activation of protein kinase C. 748 61

In this study we used endothelin as a paradigm to explore the concept that some vasoactive agents, acting through mobilization of Ca2+ and stimulation of protein kinase C, can interact with human skeletal muscle and modify its glucose transport. Cultured human skeletal myoblasts from the vastus lateralis demonstrated two subclasses of high-affinity endothelin receptors and a robust increase in cytosolic free Ca2+ upon exposure to endothelin. The endothelin-evoked rise in cytosolic free Ca2+ primarily resulted from Ca2+ mobilization from intracellular organelles. Both endothelin and insulin enhanced [3H]deoxy-D-glucose uptake in human myoblasts, but their effects were not additive. These findings also were observed in differentiated myotubes of L6 skeletal muscle cells. Moreover, [3H]deoxy-D-glucose uptake in human myoblasts was enhanced by treatment with phorbol 12-myristate 13-acetate. The endothelin- and insulin-mediated increases in [3H]deoxy-D-glucose were totally ablated by treatment with calphostin C. Such observations suggest that endothelin can enhance glucose uptake in human skeletal muscle. This is mediated through mechanisms that are at least partially protein kinase C dependent. Thus, increased levels of endothelin in vascular beds may contribute to altered glucose metabolism in essential hypertension.
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PMID:Endothelin mobilizes calcium and enhances glucose uptake in cultured human skeletal myoblasts and L6 myotubes. 751 52

Infections with verocytotoxin (VT) producing Escherichia coli have been strongly implicated in the epidemic form of hemolytic uremic syndrome (HUS). Endothelial damage plays a central role in the pathogenesis of HUS. In vitro studies have shown that VT can damage endothelial cells after interaction with its cellular receptor globotriaosylceramide (GbOse3cer). Cytokines, such as tumor necrosis factor alpha (TNF alpha) and interleukin-1 (IL-1) can potentiate the toxic effect of VT by inducing a protein-synthesis dependent increase in VT receptors on endothelial cells. In this study, the mechanisms underlying the increase in endothelial VT receptors induced by TNF alpha were studied in more detail. To investigate which proteins were involved in this induction, endothelial cells were incubated with and without TNF alpha in the presence of 14C-galactose or 14C-glucose. Thin-layer chromatography (TLC) analysis of the glycolipid extracts of these cells demonstrated a markedly enhanced incorporation of 14C-galactose in GbOse3cer and other galactose-containing glycolipids, suggesting that TNF alpha enhanced galactosyl-transferase activity. To examine the role of the two recently cloned TNF-receptors (TNFR-p75 and TNFR-p55) in the TNF alpha-induced increase in GbOse3cer in human endothelial cells, cells were incubated with TNF alpha, the TNFR-p55 selective R32W-S86T-TNF alpha-mutant, or the TNFR-p75 selective D143N-A145R-TNF alpha-mutant. The effect of TNF alpha activation, determined by binding-experiments with 125I-VT-1, could be largely, but not completely mimicked by R32W-S86T-TNF alpha. Although incubation of cells with D143N-A145R-TNF alpha did not show an increase in VT-1 binding, the monoclonal antibody utr-1, which prevents binding to TNFR-p75, decreased the TNF alpha-induced VT-1 binding. Activation of protein kinase C (PKC) by phorbol ester increases the expression of VT-1 receptors; this effect was prevented by the PKC inhibitor Ro31-8220 and by homologous desensitization by pretreatment with phorbol ester. In contrast, the presence of the protein kinase inhibitor Ro31-8220 or desensitization of PKC activity reduced the TNF alpha-induced increase in VT-1 receptors maximally by 50% and 24%, respectively. Comparable reductions in overall protein synthesis and the synthesis of E-selectin and plasminogen activator inhibitor-1 (PAI-1) were observed. This suggests an effect on general protein synthesis rather than a specific effect of PKC in the signal transduction pathway, by which TNF alpha induces VT-1 receptors. Our results indicate that TNF alpha can increase the VT-1 receptors on endothelial cells by inducing galactosyl-transferase activity, that this action of TNF alpha mainly occurs via the TNFR-p55; and that PKC activation increases expression of VT-1 receptors by a separate mechanism that acts additively to the TNF alpha-induced increase in VT-1 receptors.
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PMID:Tumor necrosis factor alpha induces endothelial galactosyl transferase activity and verocytotoxin receptors. Role of specific tumor necrosis factor receptors and protein kinase C. 753 May 4

Mixed micelles containing Nonidet P40 (NP-40) (829 microM or 4.8 mM), phosphatidylserine (PS) (14.5 or 8 mol%), and 1,2-diacylglycerol (DG) (0.5 or 1 mol%) when preincubated with protein kinase C (PKC) assay mixture containing cationic substrate and CaCl2 (400 microM) formed aggregates in a time-, temperature-, and substrate concentration-dependent manner with a t1/2 approximately 3-12 min (22 degrees C). Concomitant with the formation of these aggregates there was a substantial loss of substrate phosphorylation catalyzed by the Ca(2+)-dependent PKC alpha, beta, and gamma but not the Ca(2+)-independent PKC, delta and epsilon. All cationic PKC substrates tested, neurogranin peptide analog, neurogranin, and histone III-S, formed aggregates with PS/DG/NP-40/Ca2+ mixed micelles in a time-dependent fashion. The poly(cationic-anionic) PKC substrate protamine sulfate also forms aggregates with the mixed micelles in the presence of Ca2+, but without affecting the substrate phosphorylation by the kinase. Under similar conditions, but at 4 degrees C, neither aggregation nor loss of cationic substrate phosphorylation was observed. Another nonionic detergent, octyl glucoside, behaved similarly to NP-40. Phosphatidylinositol (PI) and phosphatidylglycerol like PS, were effective in forming aggregates with NP-40/cationic polypeptide/DG/Ca2+ as monitored by light scattering, yet without affecting substrate phosphorylation. Phosphorylation of cationic substrates by M-kinase, derived from trypsinized PKC beta, was also greatly diminished by the aggregation. In contrast, [3H]phorbol 12,13-dibutyrate binding to PKC beta was unaffected. Formation of the aggregates that were selectively utilized by the Ca(2+)-independent PKCs was dependent on the ratio of cationic substrate to the number of mixed micelles.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Selective phosphorylation of cationic polypeptide aggregated with phosphatidylserine/diacylglycerol/Ca2+/detergent mixed micelles by Ca(2+)-independent but not Ca(2+)-dependent protein kinase C isozymes. 753 39

The mechanisms for the insulin resistance induced by hyperglycemia were investigated by studying the effect of high glucose concentration (HG) and its modulation by thiazolidine derivatives, on insulin signaling using Rat 1 fibroblasts expressing human insulin receptors (HIRc). Incubating HIRc cells in 27 mM D-glucose for 4 days impaired the insulin-stimulated phosphorylation of pp185 and receptor beta-subunits. Both protein kinase C activities and phorbol dibutyrate binding to intact cells were unchanged; however, cytosolic protein-tyrosine phosphatase (PTPase) activity increased within 1 h prior to the impairment of insulin receptor kinase in HG cells (Maegawa, H., Tachikawa-Ide, R., Ugi, S., Iwanishi, M., Egawa, K., Kikkawa, R., Shigeta, Y., and Kashiwagi, A. (1993) Biochem. Biophys. Res. Commun. 197, 1078-1082). Increased PTPase activity was consistent with a 2-fold increase in the amount of PTP1B, and anti-PTP1B antibody inhibited this increment of cytosolic PTPase activity in HG cells. Co-incubating cells with pioglitazone prevented these abnormalities in cytosolic PTPase, the PTP1B content and the impaired phosphorylation of pp185 and receptor beta subunits in HG cells. Finally, HG cells had impaired insulin-stimulated alpha-amino-isobutyric acid uptake, which was ameliorated by exposure to thiazolidine derivatives. In conclusion, exposing cells to high glucose levels desensitizes insulin receptor function, and thiazolidine derivatives can reverse the process via the normalization of cytosolic PTPase, but not of protein kinase C.
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PMID:Thiazolidine derivatives ameliorate high glucose-induced insulin resistance via the normalization of protein-tyrosine phosphatase activities. 753 76

The effects of high (28mM) D-glucose (HG) on the cell cycle progression were investigated in rat aorta vascular smooth muscle cells (VSMCs) in primary culture, using an immunocytochemical analysis of cell-cycle-specific nuclear antigens. HG had no effect on the cell cycle of the serum-deprived G0 cells, whereas platelet-derived growth factor (PDGF) stimulated the entry of the G0 cells to the G1 phase without a further progression to the S and M phases. HG, but neither mannitol nor L-glucose, stimulated the progression of the PDGF-pretreated G1 cells to the S and M phases, which was blocked by calphostin-C, a protein kinase C (PKC) blocker. HG did not affect the cytosolic Ca2+ concentration ([Ca2+]i). These data suggest that HG has no competent effect on the G0 cells and acts as a progression growth factor (to stimulate the cell cycle from the G1 to the S/M) in VSMCs through the mechanism, which may be insensitive to [Ca2+]i and mediated by PKC.
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PMID:High D-glucose stimulates the cell cycle from the G1 to the S and M phases, but has no competent effect on the G0 phase, in vascular smooth muscle cells. 754 Aug 40

We studied the kinetics of cell-cell adhesion by monocyte-depleted peripheral blood lymphocytes with a stirred-cuvette aggregometer using samples from healthy young (mean age = 25 years) and healthy elderly (mean age = 75 years) human donors. This was a very reproducible assay, as there was virtually no intraindividual variability and very little interindividual variability among donors of the same age group. In all cases, aggregation of cells began immediately upon addition of the protein kinase C activator phorbol myristate acetate (PMA) or the calcium ionophore ionomycin, and continued until reaching an asymptotic limit by 20 minutes or less. Unstimulated cells did not aggregate during this time. The rate of aggregate formation and total amount of aggregation (using young donors' cells) varied between PMA- and ionomycin-stimulated cells, suggesting different mechanisms for initiating cellular aggregation, or possibly, different peripheral blood lymphocyte subsets affected by these activating agents. However, for both stimuli, the rate of aggregation and the total amount of cellular aggregation were significantly lower with the elderly donors' cells. Further, aggregation was Ca2+/Mg2+ dependent, and the reaction required metabolically active cells, as the reaction was inhibited by the addition of sodium azide and 2-deoxy-D-glucose in both donor groups. Pretreating cells with the actin polymerization inhibitor cytochalasin B resulted in 35-40% inhibition of aggregation among young donors' cells, although, interestingly, there was no apparent effect upon the cells capable of forming aggregates in the old donor group. In both donor groups, aggregation by activated cells could be partially blocked by pretreating cells with monoclonal antibodies directed against the alpha and beta chains of the integrin leukocyte function-associated antigen-1 (LFA-1) (CD11a/CD18). These results show that there is diminished cell-cell binding among lymphocytes from healthy, elderly humans, and this is partly due to altered activation of LFA-1 function with age.
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PMID:Diminished cell-cell binding by lymphocytes from healthy, elderly humans: evidence for altered activation of LFA-1 function with age. 758 93

The mechanisms for the insulin resistance induced by hyperglycemia were investigated by studying the in vitro effects of a high glucose concentration on insulin signaling with Rat 1 fibroblasts expressing human insulin receptors (HIRc). Incubation of HIRc cells for 4 days in 27 mM D-glucose led to impaired insulin-stimulation of both alpha-aminoisobutyric acid uptake (AIB) and phosphorylation of pp185 and receptor beta-subunits in vivo. In vitro autophosphorylation and tyrosine kinase activities toward poly Glu80 Tyr20 of insulin receptors from cells exposed to high glucose media (HG) were also impaired (46-48% of control), although the binding of insulin to HG cells was unchanged. One possible explanation for these high glucose effects is that they are mediated by the activation of protein kinase C (PKC). However, a 4-day-high glucose culture had no effect on cytosolic and membrane PKC activities or on phorbol dibutyrate binding to whole cells. This is in accordance with the orthophosphate labeling study, in which basal autophosphorylation activity in HG cells did not increase, suggesting that phosphorylation of serine and threonine residues in the basal state might not increase in HG cells. These results indicate that in cells exposed to high glucose, desensitization of insulin receptors was induced via several intracellular events, but might not be due to persistent activation of PKC in HIRc cells.
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PMID:High glucose condition desensitizes insulin action at the levels of receptor kinase. 759 89

To investigate the mechanism of glomerular endothelial response to high glucose, an in vitro model of the glomerular endothelial barrier was established in which transfer of fluorescein-labeled albumin across confluent monolayers of immortalized bovine glomerular endothelial cells (GEN) grown on polycarbonate membranes was measured. We first examined the effects of increased concentrations of D-glucose on albumin permeability across GEN monolayers and further investigated the role of protein kinase C (PKC) in the regulation of glucose-induced changes in endothelial barrier function. Incubation with 30 mM D-glucose increased albumin permeability more than those with 10 mM D-glucose. Albumin permeability incubated with 10 mM D-glucose plus 20 mM mannitol was not significantly different from those with 10 mM D-glucose, indicating that the increase in albumin permeability induced by 30 mM D-glucose was not due to high osmolar stimuli. A protein kinase C (PKC) inhibitor, H-7 (25 microM) significantly reduced the permeability-increasing effects of D-glucose. Lactate dehydrogenase release from endothelial cells was not significantly increased above baseline after incubation with 10 mM or 30 mM D-glucose. These results suggest that elevated concentrations of glucose activates PKC, resulting in an increase in albumin permeability across GEN.
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PMID:High glucose modulates albumin permeability across glomerular endothelial cells via a protein kinase C-dependent mechanism. 766 97

The human acrosome reaction (AR; sperm exocytosis) is absolutely required for fertilization. In the course of further characterizing the AR and its control, an AR-inhibiting glycoprotein (ARIG) from human seminal plasma was purified by differential centrifugation, carboxymethyl cellulose chromatography, chromatofocusing, and Sephacryl S300 gel filtration. A highly purified protein with a molecular weight of 74,000 was obtained as determined by gel filtration and SDS-PAGE. ARIG eluted in a narrow pH range (6.2-5.4) during chromatofocusing, corresponding to a pl of 5.8 +/- 0.4. It had covalent modifications, including internal disulfide bonds, and both complex N-linked and O-linked oligosaccharide chains. Lectin analysis suggested that sialic acid was absent and that the complex oligosaccharide chains had sequences containing galactose, galactosamine, and/or glucosamine in a beta 1-4 linkage. Mannose residues were also present. When ARIG was added to in vitro-capacitated human spermatozoa 30 min prior to the calcium ionophore A23187, the AR was significantly inhibited (ID50 = 8.5 micrograms/ml). In addition, ARIG reduced sperm exocytosis in response to atrial natriuretic peptide (a guanylate cyclase activator) and to the protein kinase C activators phorbol myristate acetate and dioctanoylglycerol. The ability of ARIG to block the human AR induced by a variety of agonists and the fact that biological activity of the protein was lost after removal of its sugar moieties suggests that it may function as a general inhibitor of sperm exocytosis and that its interaction with spermatozoa may be mediated by carbohydrate-binding proteins on the sperm cell.
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PMID:Purification and partial characterization of acrosome reaction inhibiting glycoprotein from human seminal plasma. 766 49


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