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)

The present studies were undertaken to characterize further the potential role of protein kinase C (PKC) in the regulation of apoptosis in HL-60 promyelocytic leukemia cells. The capacity of acute exposure to specific and nonspecific pharmacological inhibitors of PKC to promote apoptotic DNA fragmentation was examined both quantitatively and qualitatively and correlated with effects on cellular differentiation and proliferation. Incubation of HL-60 cells for 6 h with chelerythrine and calphostin C (highly specific inhibitors that act at the regulatory domain) or H7 and gossypol (nonspecific inhibitors that act at the PKC catalytic domain) produced concentration-dependent increases in DNA fragmentation. Induction of DNA fragmentation by chelerythrine, calphostin C, and gossypol was biphasic, resulting in a sharp decline in effect at concentrations above 5 microM, 0.1 microM, and 100 microM, respectively, whereas maximal and more stable effects were observed in response to H7 (100 microM). A 6-h exposure to staurosporine, a nonspecific but potent PKC inhibitor, failed to induce DNA fragmentation at concentrations generally used to achieve maximal inhibition of enzyme activity (e.g., 50 nM) but promoted fragmentation at considerably higher concentrations (e.g., > or = 200 nM). In contrast, 6-h exposures to the nonspecific protein kinase inhibitor hypericin (0.1 to 100 microM) or to the nonspecific inhibitor of protein kinase A, HA1004 (50 microM), were without effect on DNA fragmentation. DNA obtained from cells exposed to chelerythrine (5 microM), calphostin C (100 nM), H7 (50 microM), gossypol (50 microM), and staurosporine (200 nM)--but not hypericin (25 microM)--exhibited clear evidence of internucleosomal DNA cleavage on agarose gel electrophoresis; moreover, these cells exhibited the classical morphological features of apoptosis (cell shrinkage, nuclear condensation, and the formation of apoptotic bodies). All of the PKC inhibitors that induced apoptosis, and one of the inhibitors that did not (hypericin), substantially inhibited HL-60 cell clonogenicity at the concentrations evaluated. None of the agents tested induced cellular maturation as assessed by nonspecific esterase and nitro-blue tetrazolium positivity. DNA fragments obtained from cells exposed to specific and nonspecific PKC inhibitors possessed predominantly 5'-phosphate termini, consistent with the action of a Ca(2+)-/Mg(2+)-dependent endonuclease. Finally, Northern blot analysis revealed that exposure to calphostin C at a concentration that induced apoptosis (100 nM) failed to alter expression of bcl-2, an oncogene known to block apoptosis in both lymphoid and myeloid leukemia cells.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Induction of apoptotic DNA fragmentation and cell death in HL-60 human promyelocytic leukemia cells by pharmacological inhibitors of protein kinase C. 751 Oct 48

The effect of saponins on the one of major functions of neutrophil, namely the generation of superoxide anion (O2-), was investigated using retinoic acid (RA)-differentiated HL-60 cells (promyelocytic leukemia cells). The generation of O2- from the cells induced by saponins was monitored by the reduction of cytochrome c. All five species of crude saponins studied here, i.e. tea-leaf saponins, tea-seed saponins, ginsenosides, soyasaponins and saikosaponins, stimulated the generation of O2- from RA-differentiated HL-60 cells. Tea-leaf saponins showed the highest stimulating activity, followed by soyasaponins and ginsenosides. The cytotoxic activity of saponins was determined by the dye exclusion method after the incubation of RA-differentiated HL-60 cells with various concentrations of saponins. Saikosaponins and tea-seed saponins exhibited considerable cytotoxic activity and hemolytic activity. To examine the involvement of protein kinase C (PKC) in the neutrophil activation by saponins, the effect of H-7, an antagonist of PKC, on the generation of O2- induced by saponins was investigated. H-7 was found to inhibit the generation of O2- in a dose-dependent manner, suggesting the participation of PKC in the neutrophil stimulating process by saponins. Tea-leaf saponins, ginsenosides and soyasaponins, which had high neutrophil stimulating activity and low cytotoxic activity, seemed to be useful as a biological response modifier (BRM) for the activation of neutrophil.
 ...
PMID:[Activation of retinoic acid (RA)-differentiated HL-60 cells by saponins]. 756

Vitamin A is metabolized to several biologically active compounds, the best known of which is retinoic acid. This compound has been shown to inhibit the growth of a variety of tumor cells and to induce a more differentiated phenotype in several tumor types. Vitamin D is metabolized to the active compound 1,25-dihydroxyvitamin D3. This vitamin is well-known for its role in maintaining calcium homeostasis in the body. Recently it has been shown that vitamin D3 can also inhibit tumor cell replication and stimulate differentiation of selected tumor types. Retinoic acid is being used clinically to treat promyelocytic leukemia, head and neck tumors as well as cervical dysplasia. Use of vitamin D3 clinically has been restricted by its affect on calcium metabolism. Recently, however, new analogs of vitamin D3 have been developed which have much less calcium mobilizing activity, yet still retain their tumor inhibitory properties. The action of both of these vitamins is mediated by nuclear receptors which have the same structure as steroid receptors. There are three nuclear retinoic acid receptors (RAR alpha, beta, and gamma), but only one vitamin D3 nuclear receptor. These receptors are expressed in very small amounts. Since the ligand should be in vast excess of receptor (ie not limiting), we explored the possibility that response to vitamin A might be mediated by control of RAR expression. Using B16 mouse melanoma cells as a model system, we found that RAR alpha and gamma mRNAs were constitutively expressed. RAR beta mRNA was induced by treatment of the cells with RA. Induction of RAR beta mRNA occurred within 1h and was not inhibited by cycloheximide. The mRNA for all three RARs was dramatically decreased with 8-bromo-cyclic AMP treatment and could not be rescued by addition of RA. Analysis of RAR gamma revealed that this decrease occurred within 1h of exposure to 8-bromo-cyclic AMP and was not blocked by simultaneous treatment with cycloheximide. Nuclear extracts from cyclic AMP-treated cells showed a large decrease in protein binding to a retinoic acid response element (RARE) oligonucleotide compared to control cells. This correlated with a marked reduction of RA-stimulated RARE-reporter gene activity in transfected cells which were treated with cyclic AMP. Pre-treatment of B16 cells with cyclic AMP prior to RA addition dramatically reduced induction of PKC alpha, an early marker of RA-induced cell differentiation. Thus, cyclic AMP can antagonize the physiological actions of RA via its ability to inhibit RAR expression.
 ...
PMID:Use of vitamins A and D in chemoprevention and therapy of cancer: control of nuclear receptor expression and function. Vitamins, cancer and receptors. 764 20

The human promyelocytic leukemia cell line HL-60 was induced to differentiate to mature granulocytic cells by dbcAMP or RA. The influence of distinct protein kinases during different stages of this differentiation was studied by the use of H8, staurosporine and genistein as inhibitors of PKA, PKC and PTK respectively. In dbcAMP-mediated differentiation, the PKA activity of uninduced cells is crucial for the induction of differentiation, but therefore its significance drastically declines and a more important role is played by PKC and PTK. In RA-mediated differentiation, the native state of PKA and PKC activities are necessary and of similar importance for induction. However, the differentiation is enhanced when, following induction, the activities of PKA and PTK are normal and the activity of PKC, in contrast, is temporary suppressed. At the phenotypic stage the effect of inhibition of protein kinases on maturation is in the order PTK > PKC > PKA for the dbcAMP-mediated differentiation and PKC > PKA > PTK for the RA-mediated differentiation. The results indicate that protein kinase activities during differentiation are stage specific and this specificity depends on the inducer used.
 ...
PMID:Protein kinase inhibitors exert stage specific and inducer dependent effects on HL-60 cell differentiation. 764 44

The differentiation of a cell line of human promyelocytic leukemia, HL-60 cells, triggered by 12-O-tetradecanoyl 13-phorbol acetate (TPA), depends on the phosphorylation of some proteins, such as 17, 27, and 34 kDa proteins, by protein kinase C. For elucidation of the mechanism of ligand-induced differentiation of HL-60 cells, the effects of okadaic acid (OA), a phosphatase inhibitor, on cell differentiation and protein phosphorylation were studied. After treatment with OA, HL-60 cells differentiated into macrophage-like cells; within 16 h, 70% or more of the treated cells adhered to plastic dishes. The adherent cells did not undergo mitosis but began activities such as phagocytosis. OA increased the phosphorylation of 17, 23, 27, and 34 kDa proteins, as did TPA. The amount of annexin I (39 kDa protein) in HL-60 cells caused to differentiate with OA was 7.5-fold that without such treatment. Kinetic analysis showed that increased transcription of annexin I mRNA caused the increase in annexin I in the differentiated cells. Thus, OA and TPA increased cellular levels of annexin I and caused the differentiation of HL-60 cells into macrophage-like cells.
 ...
PMID:Okadaic acid increased annexin I and induced differentiation of human promyelocytic leukemia cells. 771 18

The product of the p53 tumor-suppressor gene has been shown to function in apoptosis and cell cycle regulation. However, there is little information regarding the regulation of apoptosis in cell differentiation. We investigated the relationship between p53-dependent apoptosis and differentiation induction using human promyelocytic leukemia HL-60 cells transfected with pMAMneo expression vectors containing dexamethasone-inducible wild-type p53 (wt-p53) cDNA inserts. Continuous exposure of the pMAMneo/wt-p53 transfectants to 1 microM dexamethasone for more than 24 h caused overexpression of wt-p53 followed by cell death with morphological changes typical of apoptosis. Using the wt-p53-inducible HL-60 cells, we examined the effects of differentiation inducers on the wt-p53-dependent apoptosis. All-trans retinoic acid (all-trans RA) at 1 nM or granulocyte macrophage colony-stimulating factor (GM-CSF) at 35 pM inhibited the wt-p53-induced apoptosis over a 42-h treatment. The apoptosis inhibition by GM-CSF, but not all-trans RA, was abolished by specific inhibitors of protein kinase C. These results suggest that extracellular signals involved in the differentiation induction could modulate the wt-p53-dependent apoptosis through protein kinase C-dependent and independent pathways.
 ...
PMID:Inhibition by differentiation-inducing agents of wild-type p53-dependent apoptosis in HL-60 cells. 773 Jan 47

Regulation of phospholipase D (PLD) activation by protein kinase C (PKC) was studied in membranes isolated from human promyelocytic leukemia HL60 cells. The activation of membrane-bound PLD by PKC partially purified from rat brain was most effectively induced with phorbol 12-myristate 13-acetate (PMA) and Ca2+ (1 microM) which caused translocation of PKC to membranes. Ro31-8425, a potent inhibitor of PKC, suppressed the catalytic activity of PKC in a concentration-dependent manner, with complete inhibition at 5 microM. However, the PKC-mediated PLD activation was not affected by Ro31-8425. It was thus suggested that membrane-bound PLD of HL60 cells was activated by PKC translocation but probably via a phosphorylation-independent mechanism. Furthermore, addition by guanosine 5'-3-O-(thio)trisphosphate (GTP gamma S) potentiated the PKC-mediated PLD activation and this potentiating effect was abolished by Rho GTPase dissociation inhibitor (RhoGDI). The suppressed PLD activation by RhoGDI was completely restored by addition of recombinant RhoA. These results indicate that the PKC-mediated PLD activation can be synergistically potentiated by RhoA in HL60 membranes.
 ...
PMID:Activation of membrane-bound phospholipase D by protein kinase C in HL60 cells: synergistic action of a small GTP-binding protein RhoA. 777

The present studies were undertaken to characterize the potential role of sphingosine in the regulation of apoptosis in HL-60 promyelocytic leukemia cells. A 6-h exposure of HL-60 cells to sphingosine or its methylated derivative, N,N-dimethylsphingosine, caused internucleosomal DNA fragmentation and stereotypical morphological changes characteristic of apoptosis (i.e., cell shrinkage, nuclear condensation, and the formation of apoptotic bodies), as well as that to pharmacological inhibitors of protein kinase C such as 1-(5-isoquinolinesulfonyl)-2-methylpiperazine and staurosporine. Apoptosis by sphingosine and N,N-dimethylsphingosine was measured using a flow cytometric method. The percentages of apoptotic cells in cultures treated with sphingosine (10 microM) and N,N-dimethylsphingosine (10 microM) for 6 h were 55.6 +/- 7.8% and 84.2 +/- 11.6%, respectively. HL-60 cells were induced to differentiate toward macrophages by treatment with 5 nM 4 beta-phorbol 12-myristate 13-acetate (PMA). Internucleosomal DNA fragmentation, which was a hallmark of apoptosis, was first detected after 10-h exposure to PMA and increased with longer treatment. Sphingosine concentrations in the cells increased concomitantly with the increasing proportion of apoptotic cells during cell differentiation. Sphingosine level in HL-60 cells differentiated by treatment with PMA for 48 h was about 3.3-fold greater than that in untreated cells. Differentiated HL-60 cells exhibited a markedly increased conversion of exogenously added [3H]ceramide to [3H]sphingosine, indicating elevation of ceramidase activity. Moreover, exposure to sphingosine resulted in down-regulation of c-myc mRNA. These observations suggest the possible role of sphingosine in induction of apoptotic DNA fragmentation during PMA-induced differentiation in myeloid leukemia cells. Sphingosine may function as an endogenous modulator mediating the apoptotic signal.
 ...
PMID:Induction of apoptosis by sphingosine in human leukemic HL-60 cells: a possible endogenous modulator of apoptotic DNA fragmentation occurring during phorbol ester-induced differentiation. 783 42

We have tested the effect of several bile acids on the proliferation and differentiation of the HL60 human promyelocytic leukemia cell line in vitro. Deoxycholate, chenodeoxycholate and lithocholic acid caused dose-dependent inhibition of cell proliferation and induction of differentiation along the monocyte/macrophage pathway as determined by morphology, NBT test, non-specific esterase, and staining by monoclonal antibodies against specific cell-surface antigens. Optimal effects were obtained at 100, 75, and 60 microM of the 3 bile acids respectively. Cell-cycle flow-cytometric analysis showed that a substantial fraction of HL60 cells accumulated at the G0/G1 transition. Protein-kinase-C inhibitors such as sphinganine and H-7 inhibited the differentiation-inducing effect of bile acids, suggesting a possible role for PKC in this regulation. When bile acids were combined with non-effective concentrations of all-trans retinoic acid, enhancement of the monocytic differentiation of THP-1 human leukemia cells was observed. Our findings demonstrate induction of tumor-cell differentiation by bile acids, compounds that present minimal undesirable effects in humans.
 ...
PMID:Inhibition of proliferation and induction of monocytic differentiation on HL60 human promyelocytic leukemia cells treated with bile acids in vitro. 792 7

We designed several oxygenated steroids in which functional groups including a hydrophobic group are arranged analogously to those of phorbol ester (12-O-tetradecanoylphorbol-13-acetate, TPA), with the aim of finding compounds with TPA-like activity, but having a different skeleton and a rigid conformation. The designed steroids, 1 beta,5 alpha-dihydroxy-3 beta-hydroxymethylcholestan-6-one (4), 3 beta,5 alpha-dihydroxycholestan-6-one (5), 3 beta-hydroxymethylcholestan-5 alpha-ol-6-one (6) and 1 beta,3 beta,5 alpha-trihydroxycholestan-6-one (7), were synthesized. A related oxygenated steroid isolated from soft coral, cholestane-1 beta,3 beta-5 alpha,6 beta-tetrol (8), was also synthesized. Among these analogs, compound 7 showed weak TPA-like activities in three biological tests: inhibition to protein kinase C and to cytosolic-nuclear tumor promoter-binding protein (CN-TPBP), and induction of differentiation of human promyelocytic leukemia cells (HL-60) to monocyte-like cells. On the other hand, compound 5 was found to be a specific ligand for CN-TPBP, but lacked the other TPA-like activities.
 ...
PMID:Synthesis of oxygenated cholesterols as structural mimics of phorbol ester-type tumor promoters. 800 92


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>