Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.11 (AMPK)
 12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Suramin inhibited protein kinase C (PKC) type I-III activity in a concentration-dependent manner. Similar inhibitory effects were observed with M-kinase, the constitutively active catalytic fragment of PKC, and autophosphorylation of PKC types I-III. Kinetic experiments indicated that suramin competitively inhibits activity with respect to ATP (Ki = 17, 27, and 31 microM, respectively) and that it can also inhibit by interaction with the substrate histone III-S. With protamine as the Pi acceptor, suramin inhibition was dependent on lipid, being approximately 4-fold less sensitive to inhibition in the absence of phosphatidylserine and diacylglycerol than in their presence. Suramin at low concentrations (10-40 microM), in the presence of Ca2+ and absence of lipid, was able to stimulate kinase activity (approximately 200-400%) in a type-dependent manner and at higher concentrations inhibited activity with histone III-S as substrate. These results indicate that suramin, a hexa-anionic hydrophobic compound, can act as a negatively charged phospholipid analog in activating PKC in the presence of Ca2+ and absence of lipid and can inhibit Ca2+/phosphatidylserine/diacylglycerol-stimulated kinase activity at higher concentrations by competing with ATP or by interaction with the exogenous substrate. Suramin inhibited cAMP-dependent protein kinase much less potently (IC50 = 656 microM) than PKC. The ability of suramin to inhibit PKC-mediated processes in intact cells was tested using the phorbol ester-stimulated respiratory burst of neutrophils as a model system. The respiratory burst of human neutrophils, when preincubated with suramin and then stimulated with phorbol ester, was inhibited in a concentration-dependent manner, suggesting that suramin may also be able to inhibit PKC-mediated processes in intact cells.
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PMID:Effects of suramin, an anti-human immunodeficiency virus reverse transcriptase agent, on protein kinase C. Differential activation and inhibition of protein kinase C isozymes. 169 Jul 10

A mouse spleen-derived mast cell line (PT-18) was employed to examine the mechanisms of adenosine 3':5'-monophosphate (cAMP)-mediated inhibition of antigen-induced lipid mediator biosynthesis. Specifically, we tested the hypothesis that increasing cAMP in mast cells inhibits lipid mediator biosynthesis by a mechanism independent of effects on histamine release (degranulation) or changes in cytosolic calcium concentration. Forskolin inhibited antigen-induced prostaglandin D2 (PGD2), leukotriene C4 (LTC4), and leukotriene B4 (LTB4) production by 30-50%. In contrast, forskolin had no inhibitory effect on antigen-induced increases in cytosolic calcium concentration, as monitored by the calcium indicator fura-2, or histamine release from the cells. The combination of the phosphodiesterase inhibitor isobutylmethylxanthine with forskolin inhibited the antigen-induced production of PGD2 and LTC4 by 90-100% and histamine release by about 60%. These responses were accompanied by a virtual abolition of the antigen-induced increase in cytosolic calcium. To test further the hypothesis that increasing cAMP can lead to inhibition of lipid mediator biosynthesis in the absence of effects on cytosolic calcium, we employed the calcium ionophores A23187 and ionomycin. Forskolin alone or in combination with isobutylmethylxanthine had no effect on ionophore-induced increases in cytosolic calcium but effectively inhibited leukotriene biosynthesis. In addition, increasing cyclic AMP led to an inhibition of ionophore-induced production of platelet-activating factor and liberation of arachidonic acid. These data suggest that a relatively modest increase in cAMP-dependent protein kinase activity in mast cells leads to inhibition of the lipase-catalyzed cleavage of arachidonic acid from membrane phospholipids in the absence of measurable effects on either histamine release or changes in cytosolic calcium concentration. This effect results in a selective inhibition of the biosynthesis of lipid mediators including LTC4, LTB4, PGD2, and platelet-activating factor.
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PMID:Inhibition by adenosine 3':5'-monophosphate of eicosanoid and platelet-activating factor biosynthesis in the mouse PT-18 mast cell. 169 Nov 75

We established a pancreatic adenocarcinoma cell line (CFPAC-1) from a patient with cystic fibrosis (CF) and assessed some of its properties. The cells show epithelial morphology and express cytokeratin and oncofetal antigens characteristic of pancreatic duct cells. Basal and stimulated levels of cAMP and cAMP-dependent protein kinase and the biophysical properties of single Cl- channels in CFPAC-1 are similar to those of airway and sweat gland primary cultures and Cl(-)-secreting epithelial cell lines. Anion transport and single Cl- channel activity was stimulated by Ca2+ ionophores but not by forskolin, cAMP analogs, or phosphodiesterase inhibitors. The cells express the CF gene and manifest the most common CF mutation, deletion of three nucleotides resulting in a phenylalanine-508 deletion. These properties have been stable through greater than 80 passages (24 months), suggesting that CFPAC-1 can serve as a continuous cell line that displays the CF defect.
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PMID:A cystic fibrosis pancreatic adenocarcinoma cell line. 169 30

Cystic fibrosis (CF), the most common lethal genetic disease in Caucasians, is characterized by defective electrolyte transport in several epithelia. In sweat duct, pancreatic, intestinal, and airway epithelia, abnormalities in transepithelial ion transport may account for the manifestations of the disease. A Cl- impermeable apical cell membrane is a common feature in these CF epithelia. The rate of transepithelial Cl- transport is controlled in part by hormonally regulated apical membrane Cl- channels; in CF epithelia, Cl- channels are present but their regulation is defective. Most regulation studies have focused on an outwardly rectifying Cl- channel, although other channels may be involved in Cl- secretion. Phosphorylation of Cl- channels or associated regulatory proteins by cAMP-dependent protein kinase or by protein kinase C (at a low internal [Ca2+]) in excised patches of membrane activates Cl- channels in normal cells but not in CF cells. Phosphorylation with protein kinase C at a high internal [Ca2+] in excised patches of membrane inactivates the channel; such inactivation is normal in CF cells. Cl- channels can also be activated by other maneuvers including an increase in the cytosolic [Ca2+], sustained membrane depolarization, an increase in temperature, proteolysis, and changes in osmolarity; the response to such maneuvers is not defective in CF. In addition to the Cl- channel abnormalities, Na+ absorption is increased in CF epithelia. It is not certain whether the increased rate of Na+ absorption results from an increase in the number of cation channels or an alteration of their kinetics. The relation of these ion channel abnormalities to the CF gene product is unknown, but an understanding of the function of the protein product and its defective function in CF should yield important new insights into the pathogenesis and potential therapy of this disease.
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PMID:Abnormal regulation of ion channels in cystic fibrosis epithelia. 169 93

In the porcine renal epithelial cell line, LLC-PK1, activation of the cAMP-dependent signal transduction pathway induces the urokinase-type plasminogen activator (uPA) gene. We show here that the cAMP response is enhanced when the intracellular calcium concentration is increased. When LLC-PK1 cells were treated with the calcium ionophore ionomycin alone, there was no uPA mRNA accumulation. However, in the presence of ionomycin the dose-response of 8-bromo-cAMP (Br-cAMP) with respect to uPA mRNA accumulation was shifted toward the lower concentrations of Br-cAMP. A Northern blot analysis after the inhibition of RNA synthesis and nuclear run-on assays showed that the synergistic effect of Ca2+ could be attributed to increases in uPA gene transcription and mRNA stability. In the presence of cycloheximide, a protein synthesis inhibitor, uPA mRNA was stabilized, but the effect of ionomycin on Br-cAMP-induced mRNA accumulation was still maintained. The result suggests that the Ca2+, at least on transcription, does not require new protein synthesis. Ionomycin treatment did not modify the activity of the cAMP-dependent protein kinase, suggesting that Ca2+ either affects a step in the pathway between the kinase and the uPA gene, or acts independently of the cAMP-dependent protein kinase pathway. The effect of ionomycin was not suppressed by protein kinase C down-regulation nor by inhibitors of calmodulin. Synergism was also observed when Br-cAMP was replaced with calcitonin, a peptide hormone which is coupled to adenylate cyclase, and when ionomycin was replaced with another ionophore A23187, suggesting that the synergism is due to an interaction between cAMP-dependent and Ca2(+)-dependent signal transduction pathways.
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PMID:Ca2+ potentiates cAMP-dependent expression of urokinase-type plasminogen activator gene through a calmodulin- and protein kinase C-independent mechanism. 170 Nov 76

Previous studies have shown that an increase in the cytosolic Ca2+ concentration [( Ca2+]c) activates Cl- channels in airway epithelia but that the effect is indirect. Because adenosine 3',5'-cyclic monophosphate (cAMP) and phorbol myristate acetate (PMA) activate Cl- channels via phosphorylation by cAMP-dependent protein kinase and protein kinase C, respectively, we asked whether Ca2(+)-dependent Cl- channel activation is phosphorylation dependent. We measured 125I- efflux as an assay of Cl- channel activation in the intact cell. We found that depletion of cellular ATP prevented cAMP- and PMA-induced activation but did not alter activation produced by the Ca2+ ionophore A23187. Moreover, addition of high concentrations of staurosporine (5 microM), to nonspecifically inhibit kinase activity, blocked cAMP- and PMA-stimulated 125I- efflux but had no effect on A23187-induced efflux. These results suggest that elevation of [Ca2+]c does not activate Cl- channels via phosphorylation.
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PMID:Evidence that Ca2(+)-dependent activation of airway epithelia Cl- channels is not dependent on phosphorylation. 170 78

The rat pituitary cell line GH3 contains a high molecular weight microtubule-associated protein with properties characteristic of microtubule-associated protein-2 (MAP-2). The 280-kDa protein is selectively immunoprecipitated by antibodies to authentic bovine brain MAP-2 and is phosphorylated at appropriate sites by cAMP-dependent protein kinase (cAMP kinase) and multifunctional Ca2+/calmodulin-dependent protein kinase (CaM kinase). Although MAP-2 is a minor cellular constituent, it can be immunoprecipitated from [32P]Pi-labeled GH3 cells and shown to contain a high level of basal phosphorylation. Vasoactive intestinal peptide, forskolin, 3-isobutyl-1-methylxanthene, or cholera toxin, treatments which increase cellular cAMP levels, or dibutyryl cAMP stimulate phosphorylation of specific sites on MAP-2 without significantly increasing its high state of basal phosphorylation. Phosphopeptide mapping reveals that the sites phosphorylated by cAMP kinase in vitro are the same sites whose phosphorylation in situ increases following stimulation of GH3 with agents that activate cAMP kinase. Increasing intracellular Ca2+ levels in GH3 cells also stimulates phosphorylation of MAP-2 but at sites distinct from those phosphorylated following treatment with cAMP inducing agonists. Phosphopeptide mapping indicates that the sites phosphorylated by CaM kinase in vitro are the same sites whose phosphorylation in situ increases following Ca2(+)-mediated stimulation. We conclude that activation of cAMP- and Ca2(+)-based signaling pathways leads to phosphorylation of MAP-2 in GH3 cells and that cAMP kinase and CaM kinase mediate phosphorylation by these pathways, respectively.
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PMID:Phosphorylation of microtubule-associated protein-2 in GH3 cells. Regulation by cAMP and by calcium. 170 24

Vitronectin (VN), previously shown to be a substrate for purified transglutaminases, was demonstrated in this study to be cross-linked when incubated with HUVEC and EAhy926 cells. The cross-linking was calcium-dependent and required that VN be plated at the substratum of the cells. These cells also phosphorylated VN, but in contrast to a previous study demonstrating a cAMP-dependent protein kinase in platelets, the phosphorylation of VN by was decreased with the addition of 1mM cAMP. The cross-linking of VN by endothelial cells demonstrates that the adhesion of these cells to VN is a dynamic process in which the substratum may be enzymatically altered. Furthermore, the modifications of VN by cross-linking and phosphorylation could modulate the functions of VN and influence events such as endothelial cell proliferation and angiogenesis.
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PMID:Vitronectin in the substratum of endothelial cells is cross-linked and phosphorylated. 170 22

Ca2+/phospholipid-dependent protein kinase (PKC) was inhibited by sulphated polysaccharides. Pentosan polysulphate (PPS) and heparin were 8-10-times more potent than dextran sulphate or heparan sulphate. Steady-state studies revealed that PPS was a competitive inhibitor with respect to ATP with an apparent Ki value of 0.32 micrograms/ml and a non-competitive inhibitor with respect to histones. In contrast, the inhibition of PKC by heparin was competitive with substrate and non-competitive with respect to ATP. The interaction of sulphated polysaccharides with the catalytic domain of PKC was further demonstrated by the absence of effect on [3H]phorbol 12,13-dibutyrate binding to the regulatory domain of PKC. Furthermore, PPS and heparin inhibited equally cAMP-dependent protein kinase and tyrosine protein kinase. Structure-function relationships indicated that the Inhibition of protein kinases by PPS and heparin fractions was highly dependent on molecular weight. Additionally, PKC-affinity chromatography revealed that a high-molecular-weight heparin fraction with strong anti-PKC activity was eluted. We set out to demonstrate that heparin and PPS, which are potent antiproliferative agents on vascular smooth muscle cells (SMC), alter intracellular PKC activity (both membrane and cytosolic). Therefore, it is suggested that the mechanism by which sulphated polysaccharides inhibit SMC growth may be by direct inhibition of PKC in SMC.
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PMID:Effect of pentosan polysulphate, standard heparin and related compounds on protein kinase C activity. 170 25

The hematoxylin-stainable protein (HSP) in keratohyalin granules of the newborn rat epidermis was found to have the same amino acid composition and the same inhibitory and immunological properties as cystatin alpha. However, only its pI value (4.7) differed from that of cystatin alpha (5.3). Alkaline phosphatase treatment of HSP changed its pI value from 4.7 to 5.3. This pI change was inhibited by EDTA, an inhibitor of alkaline phosphatase. Furthermore, 32P from [gamma-32P]ATP was incorporated into recombinant cystatin alpha by a protein kinase C (PKC) preparation in the presence of phosphatidyl serine and Ca2+ ions as co-factors. The incorporation increased dose-dependently with the added cystatin alpha and was inhibited significantly by H-7, a specific inhibitor of PKC. SDS-PAGE autoradiography of the 32P-labeled proteins showed that 32P was incorporated into the cystatin alpha. This incorporation was not observed by the action of cAMP-dependent protein kinase. Therefore, it is highly possible that the HSP is a phosphorylated cystatin alpha and that the phosphorylation is catalyzed specifically by PKC.
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PMID:Identification of hematoxylin-stainable protein in epidermal keratohyalin granules as phosphorylated cystatin alpha by protein kinase C. 171 84


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