Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to establish a regulatory role for phosphoproteins in the process of receptor-stimulated Ca2+ mobilization, isolated pancreatic acinar cells, loaded with fura-2, were stimulated with cholecystokinin-octapeptide (CCK8) in the presence of either staurosporine, a general inhibitor of protein kinase activity, or 12-O-tetradecanoylphorbol 13-acetate (TPA), an activator of protein kinase C. Staurosporine alone did not affect the average free cytosolic Ca2+ concentration ([Ca2+]i,av) in a suspension of acinar cells. However, in the presence of 1.0 microM staurosporine the stimulatory effect of submaximal concentrations of CCK8 was significantly enhanced. The potentiating effect of the inhibitor was paralleled by the increased production of inositol 1,4,5-trisphosphate. In addition, staurosporine evoked a transient increase in [Ca2+]i,av in cells prestimulated with a submaximal concentration of CCK8. The data obtained with staurosporine indicate that CCK8-stimulated phosphorylations exert a negative feedback role in the process of receptor-mediated Ca2+ mobilization. The involvement of protein kinase C was investigated by studying the effects of TPA on CCK8-induced Ca2+ mobilization. The phorbol ester induced a rightward shift of the dose/response curve for the CCK8-evoked increase in [Ca2+]i,av, which, in contrast to the unlimited shift obtained with the receptor antagonist D-lorglumide, reached a maximum of approximately one order of a magnitude at 10 nM TPA. The inhibitory effect of TPA was completely overcome by CCK8 at concentrations at or beyond 10 nM. This observation has led to the hypothesis that protein kinase C, directly or indirectly, converts the CCK receptor from a high-affinity state to a low-affinity state. Substantial evidence in favour of this hypothesis was provided by the observation that the increase in [Ca2+]i,av evoked by the CCK8 analogue JMV-180, which acts as an agonist at the high-affinity receptor, was completely blocked by TPA pretreatment. TPA also evoked a rightward shift of the dose/response curve for the carbachol-induced increase in [Ca2+]i,av, indicating that the protein-kinase-C-mediated transition of the affinity state of receptors is a more general phenomenon. In the presence of submaximal CCK8 concentrations, TPA dose-dependently decreased the poststimulatory elevated [Ca2+]i,av to the prestimulatory level, indicating that protein kinase C also inhibits the process of sustained Ca2+ mobilization. The effects of TPA were counteracted by staurosporine, suggesting that the effects of the inhibitor itself were indeed due to inhibition of the receptor-mediated activation of protein kinase C.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Receptor-evoked Ca2+ mobilization in pancreatic acinar cells: evidence for a regulatory role of protein kinase C by a mechanism involving the transition of high-affinity receptors to a low-affinity state. 769 87

All-trans-retinoic acid (RA) and retinoids induce synthesis of tissue-type plasminogen activator (t-PA) in endothelial and neuroblastoma cells in vitro and in rats in vivo. In HT1080 fibrosarcoma cells, induction of t-PA-related antigen secretion and t-PA mRNA steady state levels by RA were found to depend on de novo protein and mRNA synthesis. Fragments derived from the 5'-flanking region of the t-PA gene (+197 to -9578 base pairs (bp)) were linked to the chloramphenicol acetyltransferase gene. Transfection studies demonstrated that the region spanning bp -7145 to -9578 mediated induction by RA. A functional retinoic acid response element (RARE), consisting of a direct repeat of the GGGTCA motif spaced by 5 nucleotides (t-PA/DR5), was localized at -7.3 kilobases. The t-PA/DR5 element interacted with the heterodimer composed of retinoic acid receptor alpha and retinoid X receptor alpha in vitro, whereas its mutation abolished induction by RA in transient expression. In human EA.hy926 hybrid endothelial and in SK-N-SH neuroblastoma cells, the activity of t-PA/DR5 was found to be independent of the intervening sequence (-632 to -7144 bp) and of its distance from the transcription initiation site. Staurosporine, an inhibitor of protein kinase activity, inhibited induction by RA, suggesting that it required protein phosphorylation.
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PMID:Retinoic acid induction of human tissue-type plasminogen activator gene expression via a direct repeat element (DR5) located at -7 kilobases. 770 55

Secretion of parathyroid hormone (PTH) is regulated by Ca2+ as well as by protein kinases A and C. In this study we report that protein kinases A and C regulate PTH messenger RNA levels in vitro in dispersed bovine parathyroid cells. Incubation of bovine parathyroid cells with cholera toxin (10(-9) M), which activates adenylate cyclase and indirectly stimulates protein kinase A, increased PTH mRNA levels about 2-fold after 3 and 7 h incubation, but not at 24 h. Incubation with pertussis toxin (5 x 10(-9) M), which blocks the high-calcium-mediated inhibition of cyclic adenosine monophosphate accumulation in these cells, also reversed the inhibition of PTH mRNA levels at high Ca2+ (2.0 mM) with a marked increase in PTH mRNA levels. Pertussis toxin also increased PTH mRNA at a low extracellular Ca2+ concentration (0.7 mM) (4-fold increase) and a normal concentration (1.25 mM) (2-fold increase). Inhibition of protein kinase C both by staurosporine (1 x 10(-8) M) and by prolonged incubation with the phorbol ester phorbol 12-myristate 13-acetate (PMA) (1 x 10(-7) M), decreased PTH mRNA levels at 24 h, reaching approximately 40% and 5% of control, respectively. Staurosporine and PMA had no effect on PTH mRNA levels at 3 h. The inactive phorbol ester, phorbol 12-13-dibutyrate (PDBu), had no effect on PTH mRNA levels at 1 and 24 h. There were no changes in a control gene 18S RNA in these studies.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of parathyroid hormone messenger RNA levels by protein kinase A and C in bovine parathyroid cells. 778 66

Staurosporine, an inhibitor of protein kinases, induced outgrowth of cultured embryonic Xenopus myocytes. The outgrowing membrane elicited by staurosporine was stained uniformly with fluorescein isothiocyanate-phalloidin. Pretreatment with microfilament-disrupting agents but not microtubule inhibitors inhibited staurosporine-induced membrane outgrowth. Microfilament assembly is thus required for the action of staurosporine. Protein kinase C activators did not antagonize the membrane outgrowing effect of staurosporine. Furthermore, none of H-7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride), H-8 (N[2-(methylamino)ethyl]-5-isoquinoline sulfonamide), sphingosine, phloretin, genistein or calmidazolium induced any significant morphological changes of embryonic myocytes, indicating that tyrosine kinases, protein kinase C, protein kinase A or calmodulin-dependent protein kinases may not be involved in the membrane outgrowing action of staurosporine. Total protein content of myocytes was not altered by staurosporine and protein or RNA synthesis inhibitors did not inhibit the membrane outgrowth induced by staurosporine. Furthermore, membrane outgrowth induced by staurosporine was less pronounced in older cultured myocytes or myocytes acutely isolated at later stages of tadpoles, indicating that there is different developmental susceptibility to the action of staurosporine.
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PMID:Pharmacological evidence for a lack of role for protein kinase C in staurosporine-induced morphological changes in embryonic Xenopus myocytes. 780 81

Dose- and time-dependent killing of cultured rat hepatocytes was produced by aluminum maltolate (AlM), a neutral, water-soluble complex of aluminum 3-hydroxy-2-methyl-4H-pyran-4-one. Treatment with 10 mM AlM for 1 h killed 50% or more of the cells within 3 h. Removal of calcium from the culture medium or treatment with calcium channel blockers (verapamil, nifedipine, diltiazem) potentiated the cell killing. By contrast, inhibition by thapsigargin of the sequestration of intracellular calcium by the endoplasmic reticulum reduced the toxicity of AlM. In turn, activation of protein kinase C with 12-O-tetradecanoylphorbol 13-acetate or activation of protein kinase A with 8-[4-chlorophenyl-thio]adenosine 3',5'-cyclic monophosphate also reduced the toxicity of AlM. By contrast, inhibition of protein kinase activity by staurosporine potentiated the cell killing. Staurosporine, however, did not reverse the protection afforded by thapsigargin. Hepatocytes treated with AlM for 1 h were rescued by adding deferoxamine as late as 90 min following the removal of AlM, whereas pretreatment for 1 h with deferoxamine did not prevent the toxicity of AlM. ATP depletion did not precede loss of viability. Pharmacologic probes excluded oxidative stress as a mechanism of lethal injury by AlM, and inhibition of protein synthesis by cycloheximide did not protect the hepatocytes, thereby excluding activation of a cell death program. These data define a new model in which aluminum kills liver cells by a mechanisms distinct from previously recognized pathways of lethal cell injury. It is hypothesized that aluminum binds to cytoskeletal proteins intimately associated with the plasma membrane. This interaction eventually disrupts the permeability barrier function of the cell membrane, an event that heralds the death of the hepatocyte. The intracellular calcium ion concentration and protein phosphorylation may modify the interaction of aluminum with its critical targets. Alternatively, aluminum may inhibit the phosphorylation of cytoskeletal elements, thereby interfering with their function.
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PMID:The absence of extracellular calcium potentiates the killing of cultured hepatocytes by aluminum maltolate. 784 Jun 48

Alkaline phosphatase (ALP) hydrolyzed phosvitin and amino acid phosphates demonstrating nonisotropy at different pH. Orthovanadate, a protein phosphatase inhibitor, more specifically inhibited the serine and tyrosine phosphatase activities of ALP than that of threonine phosphatase at concentrations > 0.1 mM or 0.01 mM, respectively. Calyculin A and okadaic acid at increased concentrations increased ALP amino acid phosphatase activity. Bisphosphonates, such as disodium-1-hydroxy-1-aminopropylidine-1,1-diphosphonate (APD) and ethane-1-hydroxy-1,1-diphosphonate (HEBP), at increased concentrations, inhibited ALP amino acid phosphatase activity. These results suggest that ALP may function as a protein phosphatase. In terms of protein kinase inhibitors, N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide, N-(6-aminoheyxl)-5-chloro-1-naphthalenesulfomide hydrochloride and 4',5,7-trihydroxyisoflavone had little effect on ALP amino acid phosphatase activity. Staurosporine slightly enhanced ALP serine and threonine phosphatase activities at a concentration of 0.1 mM. These results suggest that protein phosphatase activity does not depend on the protein kinase activity of ALP, since duality between the former and the latter is not supported. ALP may function less as a protein kinase than as a protein phosphatase. The coupling mechanism of phosphate dynamics may be regulated indirectly.
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PMID:Amino acid phosphatase activity of alkaline phosphatase. A possible role of protein phosphatase. 785 10

1. Non-contractile Ca2+ mobilization (unaccompanied by muscle contraction) was initiated by nerve stimulation in the presence of neostigmine (more than 0.03 microM) at the endplate region of mouse diaphragm muscles. In the process of nicotinic receptor desensitization, the depressant effect of non-contractile Ca2+ on contractile Ca2+ mobilization was investigated by measurement of Ca(2+)-aequorin luminescence. 2. When the phrenic nerve was stimulated with paired pulses having intervals of 150, 300, 600, 1000 and 2000 ms, contractile Ca2+ transients were elicited during the generation of non-contractile Ca2+ mobilization. The amplitude of the contractile Ca2+ transients elicited by the second pulse (S2) was depressed at the shorter pulse intervals, but recovered to the initial contractile response (S1) at longer pulse intervals. 3. The extent of depression of S2 was enhanced by increasing the concentration of neostigmine (0.03 to 0.3 microM). When a low concentration (0.05 microM) of pancuronium, a competitive nicotinic antagonist, completely blocked non-contractile Ca2+ mobilization, the depression of S2 was diminished. 4. The depression of S2 was enhanced when the peak amplitude of non-contractile Ca2+ mobilization was raised by increasing the external Ca2+ concentration from 1.3 to 5 mM. 5. Staurosporine (10 nM), a protein kinase-C inhibitor, diminished the depression of S2 despite large amounts of non-contractile Ca2+ mobilization. The diminishing effect of staurosporine was counteracted by TPA (0.1 microM), a protein kinase-C activator. 6. These findings suggest that non-contractile Ca2+ mobilization may enhance the desensitization of the postsynaptic nicotinic receptor via activation of protein kinase-C at the neuromuscular junction.
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PMID:Postsynaptic nicotinic receptor desensitized by non-contractile Ca2+ mobilization via protein kinase-C activation at the mouse neuromuscular junction. 788 45

The indol alkaloid staurosporine is a potent inhibitor of protein kinase C, but has also been shown to have certain effects paradoxically similar to those of protein kinase C-activating phorbol esters. We show here that collagenase mRNA expression is stimulated by 10 nM staurosporine in normal and ras-oncogene-transformed rat fibroblasts. The kinetics of collagenase mRNA induction by staurosporine were slow compared to induction by phorbol ester. Staurosporine induction of the collagenase promoter appeared to be mediated via the TPA response element (TRE). Induction did not involve any increase in jun mRNA expression and did not require expression of c-Jun. Prolonged treatment with phorbol ester to deplete protein kinase C did not inhibit stimulation of the collagenase promoter by staurosporine. Instead, involvement of cAMP-dependent protein kinase (PKA) was indicated by inhibition of staurosporine induction by the PKA inhibitor H-89. In addition, raised levels of cAMP were observed during the first hour of staurosporine treatment. Altogether, our data indicate that staurosporine induces a PKA-dependent pathway leading to c-Jun-independent activation of the collagenase TRE element.
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PMID:Induction of the collagenase phorbol ester response element by staurosporine. 796 79

Available data indicate that the liver is a target organ for parathyroid hormone (PTH) and that this effect is most likely mediated by PTH-induced calcium entry into hepatocytes. The present study examined the effects of both PTH-(1-84) and its amino-terminal fragment [PTH-(1-34)] on cytosolic calcium concentration ([Ca2+]i) of hepatocytes and explored the cellular pathways that mediate this potential action of PTH. Both moieties of PTH produced a dose-dependent rise in [Ca2+]i, but the effect of PTH-(1-84) was greater (P < 0.01) than an equimolar amount of PTH-(1-34). This effect required calcium in the medium and was totally [PTH-(1-34)] or partially [PTH-(1-84)] blocked by PTH antagonist ([Nle8,18,Tyr34]bPTH-(7-34)-NH2] and by verapamil or nifedipine. Sodium or chloride channel blockers did not modify this effect. 12-O-tetradecanoylphorbol 13-acetate (TPA), an activator of protein kinase C, dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP), and G protein activator also produced a dose-dependent rise in [Ca2+]i. Staurosporine abolished the effect of TPA, and both staurosporine and calphostin C partially inhibited the effect of PTH. Staurosporine and verapamil together produced greater inhibition of PTH action than each alone. Rp-cAMP, a competitive inhibitor of cAMP binding to the R subunit of protein kinase A, and N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), a protein kinase A inhibitor, blocked the effect of both DBcAMP and PTH, but the effect of these agents was greater (P < 0.01) on DBcAMP action. G protein inhibitor and pertussis toxin partially blocked the action of PTH. The data indicate that 1) PTH increases [Ca2+]i of hepatocytes; 2) this action of the hormone is receptor mediated; 3) the predominant pathway for this PTH action is the stimulation of a G protein-adenylate cyclase-cAMP system, which then leads to stimulation of a calcium transport system inhibitable by verapamil or nifedipine or activation of L-type calcium channels; 4) activation of protein kinase C is also involved; and 5) the PTH-induced rise in [Ca2+]i is due, in major parts, to movement of extracellular calcium into the cell.
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PMID:Mechanisms of PTH-induced rise in cytosolic calcium in adult rat hepatocytes. 797 36

The involvement of protein kinase C (PKC), cAMP-dependent protein kinase (PKA), and other phosphorylation mechanisms in the rapid desensitization of the [Ca2+]i response to parathyroid hormone (PTH) stimulation was investigated in osteoblast-like UMR-106 cells. A 5 minute preincubation of the cell suspension with phorbol 12,13-dibutyrate (PDB) decreased the response to PTH in a concentration-dependent manner. 1-Oleoyl-2-acetyl-r-glycerol (OAG) pretreatment likewise decreased the PTH response. Staurosporine, a potent protein kinase inhibitor, completely prevented the desensitization caused by PDB. These PDB and staurosporine effects were also observed in 3 mM EGTA-containing medium ([Ca2+]free < 10(-8) M). A 5 minute pretreatment of cells with 1 microM forskolin had no effect on the calcium response to PTH. Homologous and PDB-induced desensitizations differed in several respects. Staurosporine pretreatment resulted in only a slight restoration of the PTH response under conditions of homologous desensitization. Chronic treatment with phorbol ester prevented the desensitization of the PTH response by acute phorbol treatment but not the homologous desensitization. Both homologous and PDB-induced desensitization were relieved by alkaline phosphatase treatment, consistent with the involvement of phosphorylation in the desensitization. This alkaline phosphatase effect on desensitization was inhibited by L-phenylalanine. These results suggest that PTH receptor homologous desensitization involves phosphorylation process(es) other than or in addition to those of PKC.
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PMID:Studies on the mechanism of desensitization of the parathyroid hormone-stimulated calcium signal in UMR-106 cells: reversal of desensitization by alkaline phosphatase but not by protein kinase C downregulation. 807 54


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