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)

Since benzodiazepines (BZs) have been shown to inhibit the growth of some cell lines, the effects of these drugs on human melanoma (M-6) cell growth were examined. Cell growth was measured by the tetrazolium salt (MTT) assay or the Hoechst 33258 DNA assay. Diazepam, a non-selective BZ agonist, and Ro5-4864, a peripheral-type agonist, inhibited M-6 cell proliferation by 36% and 55% with EC50s of 139 microM and 107 microM respectively, after four days of treatment in culture. The central-type agonists, clonazepam and flunitrazepam, were ineffective. The antiproliferative effect of diazepam was partially reversed by treatment with phorbol 12-myristate 13-acetate (PMA). Neither PK 11195, a peripheral-type BZ receptor antagonist, nor flumazenil a central-type antagonist, blocked the effect of diazepam, indicating that these BZ receptors are not involved. The effect of PMA suggests that the antiproliferative effect of the BZs may involve inhibition of a calcium/protein kinase C-related pathway in M-6 cells.
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PMID:Benzodiazepine-induced inhibition of human malignant melanoma (M-6) cell growth. 870 47

Bryostatin 1, a macrocyclic lactone, has undergone phase I trials as an anticancer agent. Because of the lipid solubility of this compound it must be delivered either in ethanol or in a PET formulation. During the trial, these vehicles caused a large number of treatment-related side effects. We have synthesized the triethanolamine salt of 26-succinylbryostatin 1 and find that this compound is approx. 100-fold more water soluble than bryostatin 1. Because of the potential for clinical use, we have evaluated the biologic activity of this compound. We find that in a concentration-dependent manner 26-succinylbryostatin 1 is capable of activating protein kinase C (PKC) in vitro and displacing [3H]PDBu from PKC. However, at all concentrations tested the activity was less than the parent compound bryostatin 1. Addition of bryostatin 1 but not 26-succinylbryostatin 1 to U937 leukemic cells in culture stimulated a drop in cytosolic PKC, secondary to translocation of PKC to the membrane. Although 26-succinylbryostatin 1 did not stimulate a drop in the cytosolic levels of PKC, addition to U937 cells activated transcription from an AP-1 enhancer construct and c-Jun protein phosphorylation in a similar fashion to bryostatin 1 and differentiation of U937 cells. Unlike bryostatin 1, 26-succinylbryostatin 1 was unable to cause aggregation of human platelets. Although injection of bryostatin-1 into mice carrying B16 melanoma inhibits tumor growth, there was no significant inhibition of melanoma growth when identical doses of 26-succinylbryostatin 1 were injected. Therefore, 26-succinylbryostatin 1 shares some but not all of the pharmacologic properities of bryostatin 1. This compound can activate protein phosphorylation without lowering cytosolic levels of PKC.
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PMID:Biological activity of 26-succinylbryostatin 1. 870 88

Nucleolar phosphoprotein p120 is a low abundance, proliferation-associated protein. Several functional domains have been characterized and are discussed here such as the antigenic domain recognized by a monoclonal antibody, the nuclear/nucleolar localization domain, phosphorylation domains of casein kinase II (CKII) and protein kinase C, a putative methylation domain and an RNA binding region. By sucrose gradient sedimentation analyses, protein p120 was shown to rapidly sediment with 60-80 S pre-rRNP particles but sedimented more slowly when treated with RNAse or salt suggesting binding to RNA. Nucleolar protein p120 differed from other nucleolar proteins such as C23 (nucleolin) and B23 (nucleophosmin) which sedimented more slowly near the top of the gradient.
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PMID:Functional domains of nucleolar phosphoprotein p120. 876 86

The ability of all cells to maintain their volume during an osmotic challenge is dependent on the regulated movement of salt and water across the plasma membrane. We demonstrate the phosphorylation-dependent gating of a nonselective conductance in Caco-2 cells during cellular shrinkage. Intracellular application of exogenous purified rat brain protein kinase C (PKC) resulted in the activation of a current similar to that activated during shrinkage with a Na(+)-to-Cl- permeability ratio of approximately 1.7:1. To prevent possible PKC- and/or shrinkage-dependent activation of cystic fibrosis transmembrane regulator (CFTR), which is expressed at high levels in Caco-2 cells, a functional anti-peptide antibody, anti-CFTR505-511, was introduced into the cells via the patch pipette. Anti-CFTR505-511, which is directed against the Walker motif in the first nucleotide binding fold of CFTR, prevented the PKC/shrink-age current activation. The peptide CFTR505-511 also induced current inhibition, suggesting the possible involvement of a regulatory element in close proximity to the channel that shares sequence homology with the first nucleotide binding fold of CFTR and whose binding to the channel is required for channel gating.
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PMID:Shrinkage activates a nonselective conductance: involvement of a Walker-motif protein and PKC. 877 43

Platelet shape change (PSC) represents the initial phase of platelet activation and is normally investigated in ethylene diamine tetraacetic acid (EDTA) containing platelet rich plasma (PRP); EDTA is a potent chelator of calcium and therefore reduces ionized calcium to negligible levels. It is therefore assumed that it is a process independent of calcium. To test the hypothesis that PSC may be dependent upon intracellular calcium, we examined the effect of 8-(N,N-Diethylamino) octyl 3,4,5-Trimethoxybenzoate hydrochloride (TMB-8), an inhibitor of intercellular calcium mobilization on PSC. It produced a dose dependent inhibition of PSC. We then examined whether PSC was dependent upon calmodulin and protein kinase C, a calcium dependent enzyme which is cardinal to platelet aggregation. Both calmidazolium, a specific inhibitor of calmodulin, and H-9, a specific inhibitor of protein kinase C, produced dose dependent inhibition of PSC. Finally, we investigated whether GP IIb/IIIa receptor which binds fibrinogen was involved in PSC; DMP 728 [(cyclic [D-2-amino-butyryl-N2-methyl-L-arginyl-glycyl-L-aspartyl-3- (a min o-methyl-benzoic acid], methanesulfonic acid salt] a potent GP IIb/IIIa receptor antagonist was without any effect on PSC. We conclude that PSC is a calcium, calmodulin and protein kinase C dependent process like platelet aggregation but that it does not require extracellular calcium or the participation of platelet GP IIb/IIIa complex.
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PMID:Calcium, calmodulin and protein kinase C dependence of platelet shape change. 882 31

Deletion of the yeast Ser/Thr protein phosphatase PPZ1 results in increased tolerance to sodium and lithium. PPZ1 is also important for cell integrity, as ppz1Delta cells undergo lysis under caffeine stress and PPZ1 overexpression overrides the lytic defect of mutants in the protein kinase C/mitogen-activated protein (MAP) kinase pathway. The PPZ1 protein can be dissected in two halves. The COOH-terminal half is related to type 1 phosphatases, whereas the NH2-terminal half is unrelated to phosphatases and contains a consensus site for N-myristoylation. Several mutated versions of PPZ1 have been constructed and tested for complementation of ppz1Delta mutants. We show that PPZ1 can be myristoylated in vivo and that change of Gly-2 to Ala results in lack of myristoylation and loss of complementation of salt tolerance. Removal of the entire NH2-terminal half results in complete loss of function, although it does not abolish the phosphatase activity of the protein expressed in Escherichia coli. The deletion of a large region of the NH2-terminal half (residues 17-193) does not affect the ability to complement the salt tolerance phenotype but abolish complementation of caffeine sensitivity, whereas the opposite behavior is observed upon removal of residues from 241 to 318. Mutation of Arg-451 to Leu results in both complete loss of function and of phosphatase activity. These results indicates that the NH2-terminal half of the protein contains structural determinants that are specific for certain functions and that the phosphatase activity is required but not sufficient for full PPZ1 function.
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PMID:The NH2-terminal extension of protein phosphatase PPZ1 has an essential functional role. 882 89

Previous studies have shown that aldosterone plus salt loading cause cardiac hypertrophy in rats in vivo, and that in vitro, both aldosterone and glucose stimulate fibroblast growth. The present studies examined the effects of adrenal steroids via mineralocorticoid and glucocorticoid receptors (MR and GR) on [3H]leucine incorporation by neonatal rat cardiomyocytes in culture and the role of elevated glucose in modulating such effects. GR occupancy by corticosterone, the highly selective type II (glucocorticoid) receptor agonist RU28362, or high doses of aldosterone lowers incorporation; when this effect is blocked by coincubation with the glucocorticoid antagonist RU486, aldosterone, but not corticosterone, markedly elevates leucine incorporation, indicating a specific mineralocorticoid effect via MR. Incubation with high glucose alone does not increase incorporation, but markedly increases the hypertropic effect of aldosterone in terms of both threshold and maximum response. The glucose-aldosterone synergy is via MR and is completely blocked by spironolactone. The time course of increased incorporation is identical for aldosterone acting alone or with elevated glucose, consistent with widespread transcriptional effects and suggesting that the contribution of high glucose is not rate limiting. The glucose effect reflects neither induction of MR synthesis nor an increase in their affinity; it is specific, in that it is not mimicked by L-glucose or mannitol at equal concentrations, and is mediated via an increase in protein kinase C activity that can be measured in both soluble and particulate compartments. The role of this synergy in the cardiac sequelae of diabetes remains to be explored.
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PMID:High glucose stimulates aldosterone-induced hypertrophy via type I mineralocorticoid receptors in neonatal rat cardiomyocytes. 882 70

1. The purpose of this study was to compare the actions of phorbol 12-myristate 13-acetate (PMA) and ionomycin on Na+/H+ exchange activation and histamine release to that of compound 48/80 in order to study the possible relationship between pHi and secretion of histamine in rat peritoneal mast cells. 2. Resting pHi in mast cells suspended in a bicarbonate-free physiological salt solution amounted to 6.73 +/- 0.05 (mean +/- s.d., n = 52). 3. PMA (20 nM) induced a substantial but rather slow increase in pHi. This response was very sensitive to inhibition by staurosporine, very sensitive to inhibition by 5-(N,N-hexamethylene)amiloride (HMA), insensitive to the absence of extracellular calcium (without EGTA), and sensitive to partial depletion of intracellular calcium with EGTA. 4. Ionomycin (1 microM) induced a biphasic change in pHi that was sensitive to inhibition by HMA, insensitive to staurosporine. In the absence of extracellular calcium using EGTA, the biphasic response disappeared, leaving only a slow, and diminished change in pHi. 5. The effects of ionomycin and PMA on pHi were additive. 6. Addition of the secretagogue compound 48/80 (1 microgram ml-1) increased pHi, substantially, delta pHi amounting to 0.29 +/- 0.05 pH-units (n = 4). The biphasic pHi-response was insensitive to the absence of extracellular calcium (without EGTA). The initial fast response in pHi was, however, inhibited by HMA, not staurosporine. 7. The finding that staurosporine and HMA each inhibited approximately half of the compound 48/80-induced pHi-response, whereas both inhibitors completely abolished the compound 48/80-induced pHi-response seems to indicate that two independent pathways for the activation of the Na+/H+ exchange were stimulated by compound 48/80. 8. The histamine release induced via both PKC activation (using PMA) and calcium (using ionomycin) were much larger than the sum of each activation pathway, whereas in the absence of extracellular calcium using EGTA, the histamine release in response to PMA and ionomycin was completely abolished. 9. The compound 48/80-induced histamine release was partially sensitive to inhibition by HMA (approximately 30% inhibition) and partially sensitive to inhibition by staurosporine (approximately 50% inhibition). Preincubation with staurosporine and HMA before stimulation with compound 48/80 showed the same degree of inhibition as observed after staurosporine alone, even though this combination of drugs completely inhibited the pHi-response. Furthermore, compound 48/80-induced histamine release was not dependent on the presence of extracellular calcium (with and without EGTA). 10. In spite of the similarities in second messenger pathways for pHi regulation and histamine release, it is, however, not very likely that these two processes are directly related. It is, however, possible, that an increase in pHi plays a permissive, rather than an essential role for histamine release in rat peritoneal mast cells. This hypothesis was supported by the finding that preincubation with the Na+/H+ exchange-inhibitor HMA inhibited 30% of the compound 48/80-induced histamine secretion.
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PMID:Dual regulation of the Na+/H(+)-exchange in rat peritoneal mast cells: role of protein kinase C and calcium on pHi regulation and histamine release. 883 53

1. Protein kinase modulation of gamma-aminobutyric acid-A (GABAA)- and glycine-activated Cl- currents in freshly dissociated, morphologically identified rabbit retinal rod bipolar cells was studied under voltage clamp with the use of the whole cell patch-clamp technique. Responses to pulses of GABA and glycine were monitored before, during, and after application of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase (PKA) and protein kinase C (PKC) activators, inactive analogues, and inhibitors. 2. Bath perfusion with either forskolin, an adenylate cyclase activator, or its inactive analogue, 1,9 dideoxyforskolin, reduced the GABA-activated Cl- currents by 30-50%; coapplication of N-[2-(Methylamino)ethyl]-5-isoquinolinesulfonamide hydrochloride (H-8), a PKA inhibitor, did not prevent the forskolin effects. The membrane-permeable cAMP analogues, 8-bromo-cAMP and 8-(4-Chlorophenylthio)-cAMP, and intracellularly dialyzed cAMP, did not modulate either the GABA- or glycine-activated Cl- current. Perfusion of the phosphodiesterase inhibitor 3-isobutyl-1-methylxantine (IBMX) had no direct effect on the GABA-activated current and did not alter the results with cAMP or its membrane-permeable analogues. Collectively, these results make it very unlikely that PKA represents an important mechanism of either GABAA or glycine channel modulation in the rabbit rod bipolar cell. 3. Although the isoquinoline sulfonamide protein kinase inhibitor H-8 was without discernible effect, the related compounds 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine dihydrochlorine (H-7) and N-(2-Aminoethyl)-5-isoquinolinesulfonamide dihydrochloride (H-9) both dramatically reduced the GABA response. H-7 also strongly reduced the response to glycine, whereas H-8 had no effect and H-9 had an intermediate effect. Because only certain members of this inhibitor class of agents proved effective, and their effectiveness appeared unrelated to the established activity profiles, these agents probably inhibit the Cl- currents in a phosphorylation-independent manner. Direct interaction of these inhibitors with binding sites in the GABAA receptor-channel complex has been previously reported in some other preparations. 4. The phorbol ester and PKC activator phorbol 12,13 dibutyrate (PDB) led to a 35-55% reduction in the GABA-activated Cl- current of the rod bipolar cell. The broad-spectrum kinase inhibitor staurosporine, and the more PKC-specific inhibitor calphostin C, had no direct effect on GABA responses, but prevented Cl- current reduction when coapplied with PDB. Phorbol 12-myristate 13-acetate (PMA) reduced the GABA-activated current in a fashion very similar to PDB. Staurosporine and calphostin C blocked the PMA effect. No reduction of Cl- current was seen with the inactive analogue, 4-alpha-PMA, used as a control for PKC-independent phorbol ester effects. 5. PDB effectively reduced the GABA-activated Cl- current of the rod bipolar cell at low concentrations, whereas PMA had a diminished effect at low concentrations. This is consistent with the reported concentration-dependent abilities of these agents to promote translocation of PKC-alpha immunoreactivity from the membrane to the cytosolic compartment in the rabbit retinal rod bipolar cell. Collectively, the data from phorbol esters, inactive analogues, and kinase inhibitors support the existence of a PKC-mediated mechanism for GABA-activated Cl- current reduction in these cells. 6. The naphthalenesulfonamide PKC activator N-(n-Heptyl)-5-chloro-1-naphthalenesulfonamide (SC-10) also potently and reversibly reduced the GABA-activated current. Staurosporine and calphostin C eliminated this effect. When the nonhydrolyzable guanosine 5'-triphosphate (GTP) analogue guanosine 5'-O-(3-thiotriphosphate) tetralithium salt (GTP-gamma-S) replaced GTP in the recording pipette, the SC-10-mediated GABA current reduction became irreversible.(ABSTRACT TRUNCATED)
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PMID:Protein kinase modulation of GABAA currents in rabbit retinal rod bipolar cells. 893 Feb 56

Ethanol (1-200 mM), a potent depressor of respiration and motor activity, potentiated the inhibitory Cl- current activated by glycine in 80% of the cultured mouse spinal (n = 236) neurons studied. Ethanol (100 mM) had no effect on the gamma-aminobutyric acidA current and slightly inhibited the N-methyl-D-aspartate current in these neurons. Ethanol increased the affinity of the receptors to glycine without changing the maximal amplitude of the glycine current. The EC50 was reduced from 54 +/- 3 microM in the absence of ethanol to 38 +/- 5 microM in the presence of ethanol. Activation of GTP binding proteins in the neurons with intracellular guanosine-5'-0-(2-thiotriiphosphate) (0.5 mM) enhanced the effect of ethanol, and application of a similar concentration of guanosine 5'-0-(2-thiodiphosphate had an inhibitory effect upon the current potentiation. The potentiating effect of ethanol persisted after culturing the neurons with pertussis toxin, but not with cholera toxin, an irreversible activator of Gs. Activation of cyclic AMP-dependent protein kinase by cyclic AMP and Sp-adenosine-3',5'-cyclic monophosphothioate triethylamine salt, but not of protein kinase C and protein kinase G, potentiated the glycine current. The effect of Sp-adenosine-3',5'-cyclic monophosphothioate triethylamine salt, but not of ethanol, was inhibited completely by the protein kinase A peptide inhibitor. These results suggest that ethanol potentiates the glycine activated Cl- current by modifying a signal transduction step other than protein kinase A.
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PMID:Potentiation of the glycine-activated Cl- current by ethanol in cultured mouse spinal neurons. 896 32


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