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Experimental Brain Research 1988As was shown previously (Reymann et al. 1988), the protein kinase C (PKC)-inhibitor polymyxin B prevents the maintenance of electrically induced long-term potentiation...
As was shown previously (Reymann et al. 1988), the protein kinase C (PKC)-inhibitor polymyxin B prevents the maintenance of electrically induced long-term potentiation (LTP) of synaptic transmission to CA1 neurons, indicating that posttranslational phosphorylation processes mediated by PKC are involved in mechanisms underlying this form of synaptic plasticity. To make sure that 1.) the polymyxin B actually acts against PKC activation and 2.) the long-lasting potentiation elicited by phorbol esters (Malenka et al. 1986) is mediated by PKC-activation, we have tested polymyxin B as well as the potent PKC-inhibitor K-252b during phorbol ester-induced LTP. 4-beta-phorbol-12,13-dibutyrate (PDBu) - a known activator of protein kinase C, induces a remarkable potentiation at concentrations as low as 0.5 microM. When 20 microM polymyxin B or 40 nM K-252b was administered to rat hippocampal slices prior to such a weak phorbol ester treatment, this potentiation did not develop with the exception of a small increase in the population spike in spite of polymyxin B-treatment (42% instead of 120% increase at 2 h after PDBu). In contrast, spike potentiation induced by high concentrations of PDBu (10 microM) could not be counteracted by 100 microM polymyxin B. It is concluded that at low concentrations the phorbol ester-induced potentiation is mainly mediated by a selective activation of protein kinase C and that the prevented maintenance of electrically induced LTP by polymyxin B is in fact due to inhibition of this kinase. The spike potentiation developed faster than that of the EPSP raising the possibility that PDBu activates two separate PKC-dependent processes.
Topics: Action Potentials; Animals; Electric Stimulation; Enzyme Inhibitors; Hippocampus; In Vitro Techniques; Male; Phorbol 12,13-Dibutyrate; Phorbol Esters; Polymyxin B; Protein Kinase C; Rats; Rats, Inbred Strains; Synaptic Transmission
PubMed: 2843394
DOI: 10.1007/BF00247540 -
Biochemical Pharmacology Feb 2013Bryostatin 1, like the phorbol esters, binds to and activates protein kinase C (PKC) but paradoxically antagonizes many but not all phorbol ester responses. Previously,...
Comparison of transcriptional response to phorbol ester, bryostatin 1, and bryostatin analogs in LNCaP and U937 cancer cell lines provides insight into their differential mechanism of action.
Bryostatin 1, like the phorbol esters, binds to and activates protein kinase C (PKC) but paradoxically antagonizes many but not all phorbol ester responses. Previously, we have compared patterns of biological response to bryostatin 1, phorbol ester, and the bryostatin 1 derivative Merle 23 in two human cancer cell lines, LNCaP and U937. Bryostatin 1 fails to induce a typical phorbol ester biological response in either cell line, whereas Merle 23 resembles phorbol ester in the U937 cells and bryostatin 1 in the LNCaP cells. Here, we have compared the pattern of their transcriptional response in both cell lines. We examined by qPCR the transcriptional response as a function of dose and time for a series of genes regulated by PKCs. In both cell lines bryostatin 1 differed primarily from phorbol ester in having a shorter duration of transcriptional modulation. This was not due to bryostatin 1 instability, since bryostatin 1 suppressed the phorbol ester response. In both cell lines Merle 23 induced a pattern of transcription largely like that of phorbol ester although with a modest reduction at later times in the LNCaP cells, suggesting that the difference in biological response of the two cell lines to Merle 23 lies downstream of this transcriptional regulation. For a series of bryostatins and analogs which ranged from bryostatin 1-like to phorbol ester-like in activity on the U937 cells, the duration of transcriptional response correlated with the pattern of biological activity, suggesting that this may provide a robust platform for structure activity analysis.
Topics: Antineoplastic Agents; Bryostatins; Cell Line, Tumor; Dose-Response Relationship, Drug; Gene Expression Regulation, Neoplastic; Humans; Molecular Structure; Phorbol Esters; Protein Kinase C
PubMed: 23146662
DOI: 10.1016/j.bcp.2012.10.028 -
Blood Cells, Molecules & Diseases 2001Chronic lymphocytic leukemia (CLL) is characterized by the gradual accumulation of immature B-lymphocytes. CLL B-lymphocytes mature to a plasmacytoid phenotype when...
Chronic lymphocytic leukemia (CLL) is characterized by the gradual accumulation of immature B-lymphocytes. CLL B-lymphocytes mature to a plasmacytoid phenotype when treated in vitro with phorbol esters. CLL B-cell apparent maturation is associated with altered expression of specific plasma membrane and mitochondrial proteins including heightened expression of a 30-kDa heat shock protein 60 (hsp60) analog. During our efforts to further characterize this hsp60 analog by mass spectrometry, we detected the mitochondrial protein prohibitin in phorbol-ester-matured CLL B-lymphocytes. Prohibitin modulates cell proliferation and inhibits cell cycle traverse in several systems, although few data are available for lymphocytes. A twofold increase in prohibitin concentration was observed in phorbol-ester-matured compared to resting CLL B-cells as determined by quantitative Western immunoblot analysis. A similar increase in prohibitin was observed in phorbol-ester-treated normal human B-lymphocyte populations. An antisense oligonucleotide complementary to the 5' coding region of the prohibitin gene blunted the increase in prohibitin protein in phorbol-ester-treated CLL B-cells by 42%. These data suggest that increased prohibitin expression is associated with and may facilitate B-cell maturation.
Topics: Antineoplastic Agents; B-Lymphocytes; Blotting, Western; Cell Division; Cell Size; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Oligonucleotides, Antisense; Phorbol Esters; Prohibitins; Protein Biosynthesis; Proteins; Repressor Proteins; Tetradecanoylphorbol Acetate; Up-Regulation
PubMed: 11162143
DOI: 10.1006/bcmd.2000.0348 -
Naunyn-Schmiedeberg's Archives of... Oct 1985The effect of phorbol ester, phorbol 12,13-dibutyrate, was investigated on the overflow of tritium from 3H-noradrenaline-loaded sympathetic neurons of the isolated...
The effect of phorbol ester, phorbol 12,13-dibutyrate, was investigated on the overflow of tritium from 3H-noradrenaline-loaded sympathetic neurons of the isolated perfused salivary gland of the rat. Stimulation (1 Hz for 60 s)-evoked overflow of tritium was enhanced by phorbol ester. A significant enhancement was seen at 1 nmol/l, which increased to a maximum level (over 4-fold) at 30 nmol/l. The spontaneous overflow of radioactivity, however, was not affected by any concentration of phorbol ester. The facilitatory effect of phorbol ester on stimulation-evoked overflow was observed in the presence of inhibitors of neuronal and extraneuronal uptake as well as after removal of negative feedback inhibition of release by presynaptic alpha-adrenoceptors. Tyramine (7 mumol/l for 10 min) caused a marked increase in the overflow of tritium in either the presence or absence of calcium. However, tyramine-induced overflow was not enhanced by phorbol ester. It is concluded that protein kinase C of sympathetic neurons is involved in an exocytotic release of the transmitter.
Topics: Animals; Calcium; Electric Stimulation; Enzyme Activation; In Vitro Techniques; Neurotransmitter Agents; Norepinephrine; Phorbol 12,13-Dibutyrate; Phorbol Esters; Protein Kinase C; Rats; Salivary Glands; Sympathetic Nervous System; Tyramine
PubMed: 2866448
DOI: 10.1007/BF00498863 -
The Journal of Biological Chemistry Feb 1989Interferons (IFNs) induce the expression of a variety of cellular RNAs and inhibit phorbol ester induction of other genes. Experiments reported here indicate that... (Comparative Study)
Comparative Study
Interferons (IFNs) induce the expression of a variety of cellular RNAs and inhibit phorbol ester induction of other genes. Experiments reported here indicate that phorbol esters can also specifically inhibit the expression of an IFN-induced RNA (IFN-IND-1). Phorbol esters exert their effects by inhibiting IFN-induced transcription of the gene that encodes IFN-IND-1 (ISG-54K); inhibitors of protein synthesis reverse the effects of these compounds. The actions of phorbol esters are only seen in those types of cultured cells where cycloheximide in the presence of IFN prevents long term IFN treatment of cells from inducing a "desensitized state." In desensitized cells, IFN is not able to reinduce the transcription of the RNA. Our results indicate that a protein kinase C-dependent pathway requiring protein synthesis may be one mechanism by which IFN is able to down regulate the transcription of genes whose expression it initially induces.
Topics: Cycloheximide; Fibroblasts; Gene Expression Regulation; Humans; Interferon Type I; Melanoma; Phorbol 12,13-Dibutyrate; RNA; Recombinant Proteins; Tetradecanoylphorbol Acetate; Transcription, Genetic; Tumor Cells, Cultured
PubMed: 2464596
DOI: No ID Found -
Cancer Research Jun 1985Tumor-promoting phorbol esters reversibly inhibit intercellular communication between BALB/c 3T3 cells. In order to study the possible role of blocked intercellular...
Tumor-promoting phorbol esters reversibly inhibit intercellular communication between BALB/c 3T3 cells. In order to study the possible role of blocked intercellular communication in the promotion step in cell transformation, we investigated the effect of phorbol ester tumor promoters on cell transformation and intercellular communication in BALB/c 3T3 A31-1-1 cells by a dye-transfer method. When the cells are in the growing phase, inhibition of dye transfer by phorbol esters is complete but transient; more than 90% inhibition was observed 4 h after treatment of the cells with either 12-O-tetradecanoylphorbol-13-acetate or phorbol-12,13-didecanoate, but the extent of dye transfer returned to the control level after 24 h of treatment. However, when these phorbol ester-treated cells were cultured beyond confluence in the presence of tumor promoters, the capacity to transfer dye decreased again and was inhibited continuously for at least 5 weeks of culture. In control cultures, the extent of dye transfer between cells did not decrease at their confluence. The ability of 12-O-tetradecanoylphorbol-13-acetate and phorbol-12,13-didecanoate to induce continuous inhibition of dye transfer between these cells correlated well with their capacity to promote transformation of BALB/c 3T3 cells initiated with 20-methylcholanthrene. These results suggest that the continuously blocked intercellular communication after confluence, rather than its transient inhibition during the growing phase, might play an important role in the promotion of in-vitro two-stage transformation of BALB/c 3T3 cells.
Topics: Animals; Cell Communication; Cell Transformation, Neoplastic; Cells, Cultured; Coloring Agents; Mice; Mice, Inbred BALB C; Phorbol Esters; Phorbols
PubMed: 3986803
DOI: No ID Found -
Biochemistry May 2001Phorbol ester-induced conventional protein kinase C (PKCalpha, -betaIota/IotaIota, and -gamma) isozyme activities are potentiated by 1,2-diacyl-sn-glycerol. This has...
Low- and high-affinity phorbol ester and diglyceride interactions with protein kinase C: 1-O-alkyl-2-acyl-sn-glycerol enhances phorbol ester- and diacylglycerol-induced activity but alone does not induce activity.
Phorbol ester-induced conventional protein kinase C (PKCalpha, -betaIota/IotaIota, and -gamma) isozyme activities are potentiated by 1,2-diacyl-sn-glycerol. This has been attributed to a "cooperative" interaction of the two activators with two discrete sites termed the low- and high-affinity phorbol ester binding sites, respectively [Slater, S. J., Milano, S. K., Stagliano, B. A., Gergich, K. J., Ho, C., Mazurek, A., Taddeo, F. J., Kelly, M. B., Yeager, M. D., and Stubbs, C. D. (1999) Biochemistry 38, 3804-3815]. Here, we report that the 1-O-alkyl ether diglyceride, 1-O-hexadecyl-2-acetyl-sn-glycerol (HAG), like its 1,2-diacyl counterpart, 1-oleoyl-2-acetyl-sn-glycerol (OAG), also potentiated PKCalpha, -betaI/II, and -gamma activities induced by the phorbol ester 4beta-12-O-tetradecanoylphorbol-13-acetate (TPA). Similar to OAG, HAG was found to bind to the low-affinity phorbol ester binding site and to enhance high-affinity phorbol ester binding, and to decrease the level of Ca(2+) required for phorbol ester-induced activity, while being without effect on the Ca(2+) dependence of membrane association. Thus, similar to OAG, HAG may also potentiate phorbol ester-induced activity by interacting with the low-affinity phorbol ester binding site, leading to a reduced level of Ca(2+) required for the activating conformational change. However, HAG was found not to behave like a 1,2-diacyl-sn-glycerol in that alone it did not induce PKC activity, and also in that it enhanced OAG-induced activity. The results reveal HAG to be a member of a new class of "nonactivating" compounds that modulate PKC activity by interacting with the low-affinity phorbol ester binding site.
Topics: Animals; Binding Sites; Calcium; Diglycerides; Dose-Response Relationship, Drug; Drug Synergism; Enzyme Activation; Enzyme Induction; Glyceryl Ethers; Isoenzymes; Liposomes; Phorbol Esters; Protein Binding; Protein Kinase C; Protein Kinase C beta; Protein Kinase C-alpha; Protein Kinase C-delta; Rats; Tetradecanoylphorbol Acetate
PubMed: 11352745
DOI: 10.1021/bi001002z -
The Journal of Biological Chemistry Jul 1985The murine Leydig tumor cell line, MLTC-1, contains gonadotropin receptors and a gonadotropin-responsive adenylate cyclase system that became refractory (desensitized)...
The murine Leydig tumor cell line, MLTC-1, contains gonadotropin receptors and a gonadotropin-responsive adenylate cyclase system that became refractory (desensitized) when exposed to human chorionic gonadotropin (hCG). MLTC-1 cells also contain phorbol ester receptors with a Kd of 53 nM for [3H]phorbol dibutyrate. Exposing cells to 12-O-tetradecanoyl phorbol 13-acetate (TPA) also causes desensitization of the hCG response. TPA-induced desensitization was similar to hCG-induced desensitization by every criteria tested. Both TPA- and hCG-induced desensitization caused approximately 50% loss of the hormone response within 30 min. Neither TPA or hCG altered receptor affinity for hCG. The dose response of adenylate cyclase to hCG or GTP in isolated membranes was not affected by either hCG- or TPA-induced desensitization. Similarly the dose response to hCG of cAMP accumulation in intact cells was not altered by desensitization with hCG or TPA. It was determined that MLTC-1 cells have Ca2+/phospholipid-dependent protein kinase activity that displayed a dose-dependent response to TPA. The concentration of TPA required to activate the protein kinase was similar to that required for desensitization. Phorbol esters that were unable to activate protein kinase C were also unable to desensitize MLTC-1 cells. The protein kinase from MLTC-1 cells was also activated by diacylglycerol. In addition, diacylglycerols caused desensitization of the hCG response. TPA- and diacylglycerol-induced desensitization is probably mediated by protein kinase C, and the similarities between hCG- and TPA-induced refractoriness suggests a convergence of mechanisms at some point of MLTC-1 cell desensitization.
Topics: Adenylyl Cyclases; Animals; Caenorhabditis elegans Proteins; Carrier Proteins; Cell Line; Chorionic Gonadotropin; Diglycerides; Dose-Response Relationship, Drug; Kinetics; Leydig Cell Tumor; Male; Mice; Phorbol 12,13-Dibutyrate; Phorbol Esters; Phorbols; Protein Kinase C; Receptors, Cell Surface; Receptors, Drug; Receptors, Immunologic; Receptors, LH; Testicular Neoplasms; Tetradecanoylphorbol Acetate
PubMed: 2989273
DOI: No ID Found -
The Journal of Biological Chemistry Jan 1985The human leukemic cell line, HL-60, differentiates in response to tumor-promoting phorbol esters. Recently, we have reported that one of the first events evoked by...
The human leukemic cell line, HL-60, differentiates in response to tumor-promoting phorbol esters. Recently, we have reported that one of the first events evoked by phorbol esters in HL-60 cells is the stimulation of Na+-dependent H+ efflux. In efforts to determine whether stimulation of Na+/H+ exchange by phorbol esters is coupled to induction of cellular differentiation, we found that 1) amiloride, a frequently used inhibitor of Na+/H+ exchange, rapidly inhibits phorbol ester-stimulated protein phosphorylation in vivo and protein kinase C-mediated phosphorylation in vitro, both with potency similar to that with which amiloride inhibits Na+/H+ exchange; 2) an amiloride analog, dimethylamiloride, is a far more potent inhibitor of Na+/H+ exchange than is amiloride, while being no more potent than amiloride in inhibiting phorbol ester/protein kinase C-mediated phosphorylation; and 3) at concentrations sufficient to completely inhibit Na+/H+ exchange, amiloride blocked phorbol ester-induced adhesion of HL-60 cells (adhesion being a property indicative of the differentiated state), but dimethylamiloride (as well as ethylisopropylamiloride, another very potent amiloride analog) did not. Thus, dimethylamiloride represents a potential tool for distinguishing protein kinase C-coupled from Na+/H+ exchange-coupled events in phorbol ester-stimulated cells.
Topics: Amiloride; Carrier Proteins; Cell Adhesion; Cell Differentiation; Cell Line; Humans; Leukemia, Myeloid, Acute; Phorbol 12,13-Dibutyrate; Phorbol Esters; Phorbols; Phosphorylation; Protein Kinase C; Protein Kinase Inhibitors; Pyrazines; Receptors, Cell Surface; Receptors, Transferrin; Sodium-Hydrogen Exchangers
PubMed: 2981834
DOI: No ID Found -
Journal of the American Chemical Society Sep 2002A dramatic switching of PKC agonist and antagonist activity was observed by modification of the hydrophilicity of the 12-ester side chain of phorbol. Thus, phorbol ester...
A dramatic switching of PKC agonist and antagonist activity was observed by modification of the hydrophilicity of the 12-ester side chain of phorbol. Thus, phorbol ester 4 that contains a glycol at the 12-ester chain demonstrated a pure and significant antagonist ability of PKC; however, 3 that contains an alkanol at the 12-ester chain demonstrated a potent PKC agonist activity. On the basis of the structural difference between 3 and 4 and results of the partition assay in the Hela cell/PBS buffer system, we propose that 4 acts as a translocation poison of the PKC-phorbol ester complex. The approach of controlling the agonist/antagonist activity of phorbol esters by the nature (i.e., hydrophilicity, charge, and rigidity, etc.) of the 12-ester chain may be very useful for developing selective PKC inhibitors and a potential pharmaceutical compound for anticancer therapies.
Topics: Cell Membrane; Enzyme Activation; Enzyme Inhibitors; HeLa Cells; Humans; Phorbol Esters; Protein Kinase C; Structure-Activity Relationship; Tetradecanoylphorbol Acetate
PubMed: 12207512
DOI: 10.1021/ja027048s