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)

Bryostatins and phorbol esters acutely activate and subsequently down-regulate protein kinase C (PKC) by inducing its proteolysis via an unknown pathway. Here we show that treatment of renal epithelial cells with bryostatin 1 (Bryo) produced novel PKC-alpha species, which were larger than the native protein (80 kDa). The >80 kDa PKC-alpha species contained Ubi as indicated by immunostaining and accumulated in the presence of lactacystin, a selective inhibitor of proteolysis by the proteasome. In vitro experiments with 125I-ubiquitin and membranes from Bryo-treated cells showed that PKC-alpha became ubiquitinated by a reaction that depended on ATP and a cytosolic fraction. Lactacystin or a peptidyl aldehyde, Bz-Gly-Leu-Ala-leucinal, which inhibits certain proteinase activities of the proteasome, inhibited Bryo-evoked disappearance of PKC-alpha protein from the cells. Lacta preserved Bryo-induced 32P-labeled PKC-alpha indicating that the proteasome inhibitor spared activated enzyme from down-regulation in vivo. These findings show that Bryo induces the degradation of PKC-alpha by the ubiquitin-proteasome complex.
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PMID:Ubiquitination of protein kinase C-alpha and degradation by the proteasome. 870 57

The beta-amyloid precursor protein undergoes a physiological cleavage by alpha-secretase that leads to the release of a secreted C-terminally truncated fragment called APP alpha and likely concomitantly reduces the formation of the amyloidogenic A beta peptide. Here we demonstrate that APP alpha secretion is increased by the protein kinase A (PKA) effectors 8-bromo cyclic AMP and forskolin in human embryonic kidney cells (HK293), and that this can be prevented by a proteasome inhibitor. Furthermore, we establish that PKA effectors but not protein kinase C agonists increase the chymotrypsin-like activity and phosphorylation state of the proteasome in vitro and in vivo in HK293 cells. Altogether, this report demonstrates that the alpha-secretase pathway is under the control of PKA in human cells and that the proteasome likely contributes, either directly or through yet unknown intermediates, to the PKA-stimulated APP alpha secretion in human cells.
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PMID:Protein kinase A phosphorylation of the proteasome: a contribution to the alpha-secretase pathway in human cells. 893 98

We evaluated the possibility that distinct proteolytic pathways contribute to the down-regulation of a novel (epsilon) or conventional (alpha) isoform of protein kinase C (PKC) in nonimmortalized human fibroblasts. Inhibitors of calpains and other cysteine proteinases, vesicle trafficking, or lysosomal proteolysis did not affect the down-regulation of PKC-alpha or -epsilon produced by bryostatin 1 (Bryo). Lactacystin (Lacta) and certain terminal aldehyde tripeptides or tetrapeptides, which selectively inhibit the proteasome, preserved substantial PKC-alpha and -epsilon protein from down-regulation by Bryo or phorbol-12-myristate-13-acetate. Lacta preserved active kinase in vivo, as shown by the retention of Bryo-induced autophosphorylated PKC-alpha. Concomitant with down-regulation, Bryo produced PKC-alpha and -epsilon species that were larger than the native proteins (80 and 90 kDa, respectively). Western blot analysis showed that the larger PKC-alpha species were ubiquitinylated. Treatment with Bryo plus Lacta synergistically increased multiubiquitinylated PKC-alpha, as expected if Bryo induces ubiquitinylation of PKC-alpha and Lacta blocks its degradation. Bryo also produced a 76-kDa, nonphosphorylated form of PKC-alpha and an 86-kDa form of PKC-epsilon. Phosphatase inhibitors decreased production of 76- and 86-kDa PKC-alpha and -epsilon by Bryo and preserved 80- and 90-kDa PKC-alpha and -epsilon, respectively. Our results suggest that the down-modulation of PKC-alpha and -epsilon occurs principally via the ubiquitin/ proteasome pathway. Dephosphorylation seems to predispose PKC to ubiquitinylation.
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PMID:Bryostatin 1 and phorbol ester down-modulate protein kinase C-alpha and -epsilon via the ubiquitin/proteasome pathway in human fibroblasts. 905 99

The rat gastric GATA DNA-binding protein, GATA-6 (GATA-GT1), was stably expressed in CHO-K1 cells. The GATA-6 protein was localized in the nucleus but not in the cytoplasm. Interestingly, when cells were treated with dibutyryl cAMP, the GATA-6 protein was specifically degraded. Such a phenomenon was not observed in the presence of 5'-AMP or dibutyryl cGMP. The cellular level of the GATA-6 protein was restored upon removal of dibutyryl cAMP. Degradation was also induced by cholera toxin, which increased the cellular cAMP concentration, and was inhibited by a protein kinase A inhibitor. However, activators of protein kinase C did not have any effect. The degradation was inhibited by proteasome inhibitors (PSI (benzyloxycarbonyl-Ile-Glu(O-t-Bu)-Ala-leucinal) and MG115 (benzyloxycarbonyl-Leu-Leu-norvalinal)) but not by those of lysosomes and serine proteases. These results suggest that a kinase-mediated protein phosphorylation is the cellular signal for degradation of the GATA-6 protein. This finding constitutes a novel aspect of regulation by GATA DNA-binding proteins, which are essential for developmental processes and tissue-specific transcription.
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PMID:Gastric GATA-6 DNA-binding protein: proteolysis induced by cAMP. 918 81

The physiological processing of the beta-amyloid precursor protein (betaAPP) by a protease called alpha-secretase gives rise to APP alpha, a C-terminally truncated fragment of betaAPP with known neurotrophic and cytoprotective properties. Several lines of evidence indicate that protein kinase C (PKC)-mediated events regulate this physiological pathway. We show here that the proteasome multicatalytic complex modulates the phorbol 12,13-dibutyrate-stimulated APP alpha secretion at several levels in human kidney 293 (HK293) cells. Two blocking agents of the proteasome, namely, Z-IE(Ot-Bu)A-leucinal and lactacystin, elicit a dual effect on PKC-regulated APP alpha secretion by metabolically labeled HK293 cells. Thus, short periods of preincubation (2-5 h) of the cells with the inhibitors trigger a drastic potentiation of APP alpha recovery, whereas long-term treatment of the cells (15-20 h) with the blocking agents leads to an overall decrease in the secretion of APP alpha. Such a dual effect was not observed on constitutive APP alpha secretion and intracellular formation generated by HK293 cells, which both only increase upon inhibitor treatments. Similar effects on the constitutive and PKC-regulated APP alpha secretion were observed with PC12 cells. Altogether, these data suggest distinct mechanisms underlying basal and PKC-regulated APP alpha production, indicating that this multicatalytic complex appears as a key contributor of the alpha-secretase pathway.
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PMID:Constitutive and protein kinase C-regulated secretory cleavage of Alzheimer's beta-amyloid precursor protein: different control of early and late events by the proteasome. 937 83

Treatment of cells with tumor-promoting phorbol esters results in the activation but then depletion of phorbol ester-responsive protein kinase C (PKC) isoforms. The ubiquitin-proteasome pathway has been implicated in regulating the levels of many cellular proteins, including those involved in cell cycle control. We report here that in 3Y1 rat fibroblasts, proteasome inhibitors prevent the depletion of PKC isoforms alpha, delta, and epsilon in response to the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). Proteasome inhibitors also blocked the tumor-promoting effects of TPA on 3Y1 cells overexpressing c-Src, which results from the depletion of PKC delta. Consistent with the involvement of the ubiquitin-proteasome pathway in the degradation of PKC isoforms, ubiquitinated PKC alpha, delta, and epsilon were detected within 30 min of TPA treatment. Diacylglycerol, the physiological activator of PKC, also stimulated ubiquitination and degradation of PKC, suggesting that ubiquitination is a physiological response to PKC activation. Compounds that inhibit activation of PKC prevented both TPA- and diacylglycerol-induced PKC depletion and ubiquitination. Moreover, a kinase-dead ATP-binding mutant of PKC alpha could not be depleted by TPA treatment. These data are consistent with a suicide model whereby activation of PKC triggers its own degradation via the ubiquitin-proteasome pathway.
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PMID:Activation of protein kinase C triggers its ubiquitination and degradation. 944 80

We investigated the ability of bryostatin 1 to block nerve growth factor (NGF)-induced differentiation of pheochromocytoma PC12 cells and to effect expression of protein kinase C (PKC) isoforms. Compared with phorbol myristate acetate (PMA), a likewise potent activator of PKC, high doses of bryostatin (> 200 nM) failed to down-regulate delta-PKC, as with zeta-PKC, whereas, alpha-PKC was completely down-regulated. Two forms of delta-PKC were expressed in PC12 cells, a phosphorylated 78.000 M(r) species and a de-phosphorylated 76.000 M(r) form. High-dose bryostatin treatment resulted in a 4.5-fold increase in phosphorylated delta-PKC and a 2.5-fold increase in phosphotyrosine. Inhibition of tyrosine kinase activity, with either herbimycin or genistein, prior to addition of bryostatin abrogated protection from down-regulation and led to simultaneous increases in ubiquitinated 110.000 M(r)-delta-PKC. Similarly, pre-treatment of cells with N-acetyl-L-leucinyl-L-leucinyl-L-norleucinal, an inhibitor of the proteasome pathway, prior to low-dose treatment with bryostatin resulted in a dose-dependent accumulation of delta-PKC and inhibition of down-regulation. Protection of delta-PKC from down-regulation by high-dose bryostatin requires a counter-balance between protein tyrosine kinase and phosphatase systems. High doses of bryostatin blocked NGF-induced neurite outgrowth without altering Y-490 TrK A phosphorylation or an alteration in pp44/42 mitogen-activated protein kinase. Our findings suggest that the phosphorylation state of delta-PKC may regulate its ability to participate in signal coupling and modulation of cell growth and differentiation pathways. Moreover, these data reveal the existence of a signalling pathway independent of MAP kinase that affects NGF differentiation in a negative fashion.
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PMID:Delta-protein kinase C phosphorylation parallels inhibition of nerve growth factor-induced differentiation independent of changes in Trk A and MAP kinase signalling in PC12 cells. 961 84

Many cytokines and growth factors activate common signal transduction pathways and yet are able to elicit distinct cell-specific responses. We are defining mechanisms regulating signalling molecules in order to understand how cytokines can produce unique responses. It was found that individual members of the signal transducer and activator of transcription (STAT) family are regulated by ciliary neurotrophic factor (CNTF) and by protein kinase C. Treatment of SH-SY5Y human neuroblastoma cells with the phorbol ester, 12- O -tetradecanoylphorbol 13-acetate (TPA), for 4-5 h caused a 60% decline in both STAT2 and STAT3 levels and no decline in levels of STATs 1, 5 or 6, or in Jaks 1 or 2. The decline in STAT3 was inhibited by treatment with MG132, an inhibitor of proteasome-dependent protein degradation. Treatment of cells with CNTF induced a rapid tyrosine phosphorylation of STAT3 followed by a time-dependent decay of this signal. Loss of tyrosine phosphorylated STAT3 was inhibited by MG132 but did not require protein kinase C activity. These results suggest that STAT3 availability can be controlled by proteasome-dependent pathways activated either by protein kinase C or by cytokines.
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PMID:Ciliary neurotrophic factor and phorbol ester each decrease selected STAT3 pools in neuroblastoma cells by proteasome-dependent mechanisms. 1020 66

The intracellular signalling pathways controlling muscle protein synthesis and proteolysis are potential targets for anabolic/anti-catabolic therapy. In this review, we consider both the potentiation of the effect of anabolic hormones and suppression of the catabolic action of cytokines. Potential candidates, in particular isoforms of the protein kinase C family, and their role in the control of ribosomal action and the ubiquitin-proteasome proteolytic system are discussed.
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PMID:Potential intracellular targets for anabolic/anti-catabolic therapies. 1045 50

Long-term facilitation (LTF) of the sensory-to-motor synapses that mediate defensive reflexes in Aplysia requires induction of the transcription factor Aplysia CCAAT/enhancer binding protein (ApC/EBP) as an early response gene. We examined the time course of ApC/ EBP DNA binding during the induction of LTF: Binding activity was detected within 1 h of the sensitization treatment with serotonin, reached a maximum at 2 h, and decreased after 6 h. How are DNA binding and the turnover of ApC/EBP regulated? We find that phosphorylation of ApC/EBP by mitogen-activated protein (MAP) kinase is essential for binding. MAP kinase appears to be activated through protein kinase C. We also showed that ApC/EBP is degraded through the ubiquitin-proteasome pathway but that phosphorylation by MAP kinase renders it resistant to proteolysis. Thus, phosphorylation by MAP kinase is required for ApC/EBP to act as a transcription activator as well as to assure its stability early in the consolidation phase, when genes essential for the development of LTF begin to be expressed.
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PMID:Activation and degradation of the transcription factor C/EBP during long-term facilitation in Aplysia. 1058 1


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