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)

Modulation of protein kinase C (PKC) activity has been demonstrated to either prevent or enhance drug-induced apoptosis in various tissue types. We tested four novel modulators of PKC activity in comparison to the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) for the capability to affect differentiation, cell cycle progression and apoptosis in the human myeloid leukemia cell lines U937 and HL-60. Farnesyl thiotriazole (FTT) and N-(n-heptyl)-5-chloro-1-naphthalenesulfonamide (SC-10) are both direct activators of PKC, whereas 6-(2-(4-[(4-fluorophe-nyl)phenylmethylene]-1-piperidinyl)ethyl)-7-methyl-5H-thiazolo[3,2-a]pyrimidin-5-one (R59022) and [3-[2-[4-(bis-(4-fluorophenyl)methylene]piperidin-1-yl)ethyl]-2,3-dihydro-2-thioxo-4(1H)-quin-azolinone (R59949) are diacyl glycerol kinase inhibitors that activate PKC by enhancing the levels of the endogenous ligand diacyl glycerol. U937 cells displayed a slight reduction in the number of cells in G(2)/M cell cycle phase after exposure to FTT, SC-10, R59022 and R59949, respectively. In contrast, HL-60 cells demonstrated a largely unaltered cell cycle distribution. Whereas TPA treatment resulted in a strong induction of p21(WAF/CIP1), c-Fos and c-Jun levels, neither one of the novel PKC activators altered expression of these proteins. Consequently, we tested the ability of the activators to cause membrane translocation of PKC. While TPA treatment resulted in translocation of the PKC isoforms alpha, delta and epsilon, SC-10 and FTT failed to induce alterations in the PKC content of the membrane and cytosolic fractions, respectively. Expression of the beta(2)-integrin CD11c that is induced during TPA-mediated differentiation remained unaltered after exposure to SC-10 and was partly reduced after treatment with FTT. To further investigate the effect of these activators upon apoptosis in leukemic cells, HL-60 and U937 cells were treated with 1-beta-D-arabinofuranosylcytosine (Ara-C) or etoposide (VP-16). Whereas TPA strongly reduced apoptosis in Ara-C- or VP-16-treated U937 cells, little if any reduction was observed after pretreatment with either FTT, SC-10, R59022 or R59949, respectively, in these cells. In contrast, TPA enhanced apoptosis in Ara-C- or VP-16-treated HL-60 cells. Interestingly, FTT and SC-10 demonstrated a protective effect in Ara-C-treated HL-60 cells. Taken together, these data suggest that the novel PKC activators FTT, SC-10, R59022 and R59949 exhibit modest biological effects upon leukemic blast cells, and are not capable of enhancing the apoptotic response of these cells to cytotoxic drugs.
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PMID:Effect of novel modulators of protein kinase C activity upon chemotherapy-induced differentiation and apoptosis in myeloid leukemic cells. 1218 29

RAS mutations are one of the most frequent molecular abnormalities associated with myeloid leukemia and preleukemia, yet there is a poor understanding of how they contribute to the pathogenesis of these conditions. Here, we describe the consequences of ectopic mutant N-Ras (N-Ras*) expression on normal human erythropoiesis. We show that during early (erythropoietin [EPO]-independent) erythropoiesis, N-Ras* promoted the amplification of a phenotypically primitive but functionally defective subpopulation of CD34(+) erythroblasts. N-Ras* also up-regulated the expression of megakaryocyte antigens on human erythroblasts. Although early erythroblasts expressing N-Ras* were able to respond to erythropoietin and generate mature progeny, this occurred with greatly reduced efficiency, probably explaining the poor colony growth characteristics of these cells. We further report that this oncogene promoted the expression and activation of protein kinase C (PKC) and that the effects of N-Ras* on erythropoiesis could be abrogated or attenuated by inhibition of PKC. Similarly, the effects of this oncogene could be partially mimicked by treatment with PKC agonist. Together, these data suggest that expression of N-Ras* is able to subvert the normal developmental cues that regulate erythropoiesis by activating PKC. This gives rise to phenotypic and functional abnormalities commonly observed in preleukemia, suggesting a direct link between RAS mutations and the pathogenesis of preleukemia.
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PMID:Protein kinase C mediates mutant N-Ras-induced developmental abnormalities in normal human erythroid cells. 1239 54

The effects of the PKC activator and down-regulator bryostatin 1 and the PKC and Chk1 inhibitor 7-hydroxystaurosporine (UCN-01) were compared with respect to potentiation of 1-beta-D-arabinofuranosylcytosine (ara-C)-induced apoptosis in human myelomonocytic leukemia cells (U937). Whereas bryostatin 1 and UCN-01 both markedly enhanced ara-C-induced mitochondrial injury (e.g., cytochrome c and Smac/DIABLO release, loss of mitochondrial membrane potential), caspase activation, and apoptosis, ectopic expression of an N-terminal loop-deleted Bcl-2 mutant protein protected cells from ara-C/UCN-01- but not ara-C/bryostatin 1-mediated lethality. Conversely, ectopic expression of CrmA or dominant-negative caspase-8 abrogated potentiation of ara-C-mediated apoptosis by bryostatin 1 but not by UCN-01. Exposure of cells to ara-C and bryostatin 1 (but not UCN-01) resulted in sustained release of tumor necrosis factor (TNF) alpha; moreover, potentiation of ara-C lethality by bryostatin 1 (but not by UCN-01) was reversed by coadministration of TNF soluble receptors or the selective PKC inhibitor bisindolylmaleimide (1 microM). Finally, similar events were observed in the human promyelocytic leukemia cell line HL-60. Together, these findings suggest that potentiation of ara-C lethality in human myeloid leukemia cells by bryostatin 1 but not UCN-01 involves activation of the extrinsic, receptor-mediated apoptotic pathway, and represents a consequence of bryostatin 1-mediated release of TNF-alpha. They also argue that the mechanism by which bryostatin 1 promotes ara-C-induced mitochondrial injury, caspase activation, and apoptosis involves factors other than or in addition to PKC down-regulation or modulation of Bcl-2 phosphorylation status.
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PMID:Bryostatin 1 and UCN-01 potentiate 1-beta-D-arabinofuranosylcytosine-induced apoptosis in human myeloid leukemia cells through disparate mechanisms. 1248 56

Interactions between the protein kinase C (PKC) activator/down-regulator bryostatin 1 and paclitaxel have been examined in human myeloid leukemia cells (U937) and in highly paclitaxel-resistant cells ectopically expressing a Bcl-2 phosphorylation loop-deleted protein (Delta Bcl-2). Treatment (24 hours) of wild-type cells with paclitaxel (eg, 5 to 20 nM) in combination with 10 nM bryostatin 1 induced a marked increase in mitochondrial damage (eg, cytochrome c and Smac/DIABLO [second mitochondria-derived activator of caspases/direct IAP binding protein with low pI] release), caspase activation, Bid cleavage, and apoptosis; moreover, bryostatin 1 circumvented the block to paclitaxel-induced mitochondrial injury and apoptosis conferred by ectopic expression of the loop-deleted protein. Coadministration of tumor necrosis factor (TNF) soluble receptors, or ectopic expression of CrmA or dominant-negative caspase-8, abrogated potentiation of paclitaxel-induced mitochondrial injury and apoptosis by bryostatin 1, implicating the extrinsic apoptotic pathway in this process. Similar events occurred in HL-60 leukemia cells. Potentiation of paclitaxel-induced apoptosis in wild-type and mutant cells by bryostatin 1 was associated with increases in TNF-alpha mRNA and protein and was mimicked by exogenous TNF-alpha. Coadministration of the selective PKC inhibitor GFX (1 microM) blocked the increase in TNF-alpha mRNA levels and apoptosis in bryostatin 1/paclitaxel-treated cells. Lastly, synchronization of cells in G(2)M increased their sensitivity to TNF-alpha-associated lethality. Collectively, these findings indicate that in U937 cells, bryostatin 1 promotes paclitaxel-mediated mitochondrial injury and apoptosis, and circumvents resistance to cell death conferred by loss of the Bcl-2 phosphorylation domain, through the PKC-dependent induction of TNF-alpha. They further suggest that this process is amplified by paclitaxel-mediated arrest of cells in G(2)M, where they are more susceptible to TNF-alpha-induced lethality.
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PMID:Induction of tumor necrosis factor by bryostatin 1 is involved in synergistic interactions with paclitaxel in human myeloid leukemia cells. 1252 1

Interactions between the protein kinase C activator bryostatin 1 and the cyclin-dependent kinase (CDK) inhibitor flavopiridol (FP) have been examined in human myeloid leukemia cells (U937 and HL-60). Previous studies have demonstrated synergistic induction of apoptosis in leukemic cells exposed to the potent differentiation-inducer phorbol 12-myristate 13-acetate (PMA) in conjunction with FP [L. Cartee et al., Cancer Res., 61: 2583-2591, 2001]. Although bryostatin 1 (10 nM) is a very weak inducer of differentiation compared with PMA in these cells, coadministration of a minimally toxic concentration of FP (100 nM) did not promote bryostatin 1-related maturation but instead caused a marked increase in mitochondrial damage (e.g., cytochrome c release; loss of Deltapsi(m)), caspase activation, poly(ADP-ribose) polymerase cleavage, and apoptosis. Bryostatin 1/FP-induced apoptosis was significantly diminished in cells ectopically expressing dominant-negative Fas-associated death domain or by coadministration of tumor necrosis factor (TNF)-alpha soluble receptors, implicating the extrinsic pathway in bryostatin 1/FP actions. Enhanced apoptosis in bryostatin 1/FP-treated cells was accompanied by down-regulation of Mcl-1 and a sustained increase in TNF-alpha release. The selective protein kinase C inhibitor GFX blocked TNF-alpha and cytochrome c release in bryostatin 1/FP-treated cells and attenuated apoptosis. Finally, coadministration of bryostatin 1 (or PMA) with FP induced a marked increase in apoptosis in U937 cells ectopically expressing an NH(2)-terminal phosphorylation loop-deleted Bcl-2 protein, which are otherwise highly resistant to FP-mediated lethality. Taken together, these findings suggest that synergistic induction of apoptosis by bryostatin 1 and FP does not stem from disruption of the leukemic cell maturation process but instead results from enhanced release of TNF-alpha and activation of the extrinsic apoptotic cascade, culminating in cell death.
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PMID:Protein kinase C-dependent activation of the tumor necrosis factor receptor-mediated extrinsic cell death pathway underlies enhanced apoptosis in human myeloid leukemia cells exposed to bryostatin 1 and flavopiridol. 1253 76

Phorbol 12-myristate 13-acetate (PMA) is a protein kinase C (PKC) activator and tumor promoter that induces terminal differentiation in human myeloid leukemia cells. We undertook to characterize phorbol ester-activated PKC-mediated cell cycle arrest and apoptosis. In the present studies, we determined the effect of high intracellular levels of the anti-apoptosis Bcl-2 protein on caspase 3 activation and cyctochrome c release during phorbol ester 12-myristate 13-acetate (PMA)-induced apoptosis. For this, we used the U937 cells, Bcl-2 overexpressed U937 cells (U937/Bcl-2) and the PMA-resistant derivative cell line R-U937. The G1 arrest of U937 cells and U937/Bcl-2 cells induced by treatment with 20 nM PMA is associated with cyclin A down-regulation and accumulation of p21, cdks inhibitor. However, PMA had no effect on the levels of cyclin A expression and p21 expression under the same conditions of time and concentration of PMA in the R-U937 cells. Treatment with 20 nM PMA for 24 h produced morphological features of apoptosis and DNA fragmentation in U937 and U937/Bcl-2 cells, but not in R-U937 cells. This was associated with the caspase 3 activation and cyctochrome c release. R-U937 cells exhibited less cytochrome c release and sustained phosphorylation level of Akt during PMA-induced apoptosis. These findings indicate that R-U937 cells are resistant to PMA-induced apoptosis by a mechanism of the signaling defect in the activation of the caspase 3 that is involved in the execution of apoptosis.
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PMID:Inactive caspase 3 activates Akt in human leukemia cells susceptible or resistant to apoptosis induced by phorbol ester. 1268 78

Tumor necrosis factor-alpha (TNF-alpha) induces both rapid onset of apoptosis and monocytic differentiation in HL-60 human myeloid leukemia cells. In this study, we examined the effect of activation of protein kinase C (PKC) in c-Myc protein expression in association with the induction of apoptosis and differentiation in TNF-alpha-treated HL-60 cells. Pretreatment with phorbol 12-myristate 13-acetate (PMA), an activator of PKC, prevented TNF-alpha-induced rapid onset of apoptosis, which occurs at 3 h culture with TNF-alpha, concomitantly with the up-regulation of c-Myc protein expression. In addition, PMA enhanced TNF-a-induced differentiation at 24h treatment. This was documented by the expression of integrin Mac-1 molecule (CD11b) on the cell surface and the cellular adhesion to the plastic bottom of the flask, indicating the differentiation along with the monocyte/macrophage lineage. These results indicate that activation of PKC not only counteracts apoptosis but also enhances differentiation in TNF-alpha-treated HL-60 cells. Up-regulation of c-Myc protein evoked by pretreatment with PMA for a short time could disturb the signaling pathway of the ceramide and sphingosine, which are known to function as the endogenous modulators mediating the apoptotic signal of TNF-alpha. Our results strongly suggest the role of c-Myc protein as a mediator of cytoprotective effect of PKC pathway, and PKC pathway opposes apoptosis and consequently undergo differentiation via rapid up-regulated c-Myc protein expression during TNF-alpha signaling of HL-60 cells. Our findings provide a new insight for a role of PKC and c-Myc protein with special reference to the regulatory mechanisms in the decision of cellular fate, differentiation or apoptosis.
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PMID:Activation of protein kinase C enhances TNF-alpha-induced differentiation by preventing apoptosis via rapid up-regulation of c-Myc protein expression in HL-60 cells. 1268 21

The protein kinase C (PKC) isoenzyme superfamily represents a popular target in pharmacological interventions designed to elicit apoptosis directly in tumor cells or to potentiate the lethal effects of antineoplastic agents. Numerous observations support the clinical utility of PKC inhibition by experimental sphingolipid derivatives such as safingol. The present studies document the cytotoxicity and chemomodulatory capacity of phenethylisothiocyanate derivatives of sphinganine and sphingosine (PEITC-Sa and PEITC-So) in the human myeloid leukemia cell line HL-60. The biological actions of these novel derivatives were compared directly with those of the parent compounds sphinganine and sphingosine. Exposure to natural and modified sphingoid bases promoted extensive apoptotic cell death. The PEITC-sphingoid base derivatives exhibited higher cytotoxicity than their natural counterparts and were also distinctly superior to the clinically relevant sphingoid base analog safingol. In each instance, lethality was shown to correlate with inhibition of conventional and novel PKC isoforms and downstream loss of extracellular signal-regulated kinase (ERK)1/ERK2. The involvement of these signaling systems in potentiating the lethal actions of 1-(beta-D-arabinofuranosyl)cytosine (araC) was also examined with regard to the differential actions of PEITC-Sa and PEITC-So to that of the parent compounds as well as safingol. Exposure to araC alone rapidly increased PKC activity. In the presence of PEITC-Sa or PEITC-So, the therapeutic efficacy of araC increased markedly; moreover, potentiation was directly related to the loss of araC-stimulated PKC activity. These findings demonstrate that PEITC-substituted sphingoid base analogs exert potent antineoplastic effects in human leukemia cells. We suggest that these synthetic lipids represent potentially useful agents in the development of conventional PKC/novel PKC-directed chemotherapeutic strategies.
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PMID:Intrinsic cytotoxicity and chemomodulatory actions of novel phenethylisothiocyanate sphingoid base derivatives in HL-60 human promyelocytic leukemia cells. 1472 18

HACS1 is a Src homology 3 and sterile alpha motif domain-containing adaptor that is preferentially expressed in normal hematopoietic tissues and malignancies including myeloid leukemia, lymphoma, and myeloma. Microarray data showed HACS1 expression is up-regulated in activated human B cells treated with interleukin (IL)-4, CD40L, and anti-immunoglobulin (Ig)M and clustered with genes involved in signaling, including TNF receptor-associated protein 1, signaling lymphocytic activation molecule, IL-6, and DEC205. Immunoblot analysis demonstrated that HACS1 is up-regulated by IL-4, IL-13, anti-IgM, and anti-CD40 in human peripheral blood B cells. In murine spleen B cells, Hacs1 can also be up-regulated by lipopolysaccharide but not IL-13. Induction of Hacs1 by IL-4 is dependent on Stat6 signaling and can also be impaired by inhibitors of phosphatidylinositol 3-kinase, protein kinase C, and nuclear factor kappaB. HACS1 associates with tyrosine-phosphorylated proteins after B cell activation and binds in vitro to the inhibitory molecule paired Ig-like receptor B. Overexpression of HACS1 in murine spleen B cells resulted in a down-regulation of the activation marker CD23 and enhancement of CD138 expression, IgM secretion, and Xbp-1 expression. Knock down of HACS1 in a human B lymphoma cell line by small interfering ribonucleic acid did not significantly change IL-4-stimulated B cell proliferation. Our study demonstrates that HACS1 is up-regulated by B cell activation signals and is a participant in B cell activation and differentiation.
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PMID:The SH3-SAM adaptor HACS1 is up-regulated in B cell activation signaling cascades. 1538 29

The role of putrescine, spermidine and spermine in phorbol 12-myristate-13-acetate (PMA)-induced macrophage differentiation was examined in human HL-60 and U-937 myeloid leukemia cells. Unlike other polyamines, spermine affected this differentiation by acting as a negative regulator. This negative regulation was established by showing that the PMA-induced macrophage phenotype, but not PMA-associated replication arrest, was abrogated (a) by replenishing the PMA-evoked decrease in cellular spermine levels with this polyamine from an exogenous source and (b) by blocking PMA-induced expression of the polyamine catabolic enzyme N(1)-spermidine/spermine acetyltransferase (SSAT) with antisense oligonucleotides in the presence of low substrate level. The PMA-evoked reduction in cellular spermine appears to result from an increase in the activity of SSAT and a decrease in the activity of ornithine decarboxylase, the polyamine biosynthetic enzyme. To a degree, these changes are due to corresponding changes in the expression of the genes that code for these enzymes. When cell differentiation is initiated, SSAT expression is increased after PMA-evoked activation of protein kinase C-beta. The present studies raise the possibility that agents able to reduce spermine levels in patients' myeloid leukemia cells may enhance the activity of differentiation therapy drugs for this type of leukemia.
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PMID:Spermine acts as a negative regulator of macrophage differentiation in human myeloid leukemia cells. 1549 67


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