scholarly journals Post-transcriptional regulation of apolipoprotein E expression in mouse macrophages by phorbol ester

1993 ◽  
Vol 292 (1) ◽  
pp. 105-111 ◽  
Author(s):  
L Dory
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Apolipoprotein E ◽  
Phorbol Ester ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Mouse Macrophages ◽  
Apoe Expression

Phorbol ester-mediated differentiation of THP-1 cells (a human monocytic cell line) into mature macrophages is associated with a transcriptional induction of apolipoprotein E (apoE) expression [Auwerx, Deeb, Brunzell, Peng and Chait (1988) Biochemistry 27, 2651-2655]. Endotoxin, on the other hand, which may also act through activation of protein kinase C, is a potent inhibitor of apoE expression in mouse macrophages [Werb and Chin (1983) J. Biol. Chem. 258, 10642-10648]. The present experiments examine the effect of phorbol ester, an activator of protein kinase C, on the apoE expression in mouse thioglycollate-elicited peritoneal macrophages. Phorbol ester inhibits apoE expression in a specific, time- and dose-dependent manner. A 75% inhibition in the rate of apoE secretion, but not that of total protein, was observed following a 4.5 h incubation with 160 nM phorbol ester, although nearly full inhibition was obtained with 40 nM. The changes in apoE secretion were paralleled by similar changes in apoE synthesis, indicating synthesis as the primary site of action. The decreased rates of apoE synthesis are shown not to be due to increased apoE degradation. The profound inhibition of apoE synthesis was not accompanied by significant changes in apoE mRNA levels at any concentration of phorbol ester (up to 16 microM), or length of treatment (up to 24 h), suggesting a post-transcriptional locus of regulation of apoE expression. Although the early changes in apoE synthesis correlate with increased microsomal protein kinase C activity, the suppression of apoE expression persists even during conditions of nearly complete (> 95%) loss of protein kinase C activity, suggesting that the direct or indirect effect of protein kinase C on apoE expression is mediated by a stable phosphorylated protein, or that the observed effects are mediated through a protein kinase C species that is not readily downregulated by phorbol esters. The presented studies clearly demonstrate the potential importance of the translational regulation of apoE expression through the protein kinase C signal transduction pathway.

Endotoxin-Induced Tissue Factor in Human Monocytes is Dependent upon Protein Kinase C Activation

1993 ◽  
Vol 70 (05) ◽  
pp. 800-806 ◽  
Author(s):  
C Ternisien ◽  
M Ramani ◽  
V Ollivier ◽  
F Khechai ◽  
T Vu ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Tissue Factor ◽  
Factor Ix ◽  
Transcriptional Level ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Human Monocytes ◽  
Kinase C ◽  
Pkc Activation

SummaryTissue factor (TF) is a transmembrane receptor which, in association with factors VII and Vila, activates factor IX and X, thereby activating the coagulation protease cascades. In response to bacterial lipopolysaccharide (LPS) monocytes transcribe, synthesize and express TF on their surface. We investigated whether LPS-induced TF in human monocytes is mediated by protein kinase C (PKC) activation. The PKC agonists phorbol 12- myristate 13-acetate (PMA) and phorbol 12, 13 dibutyrate (PdBu) were both potent inducers of TF in human monocytes, whereas 4 alpha-12, 13 didecanoate (4 a-Pdd) had no such effect. Both LPS- and PMA-induced TF activity were inhibited, in a concentration dependent manner, by three different PKC inhibitors: H7, staurosporine and calphostin C. TF antigen determination confirmed that LPS-induced cell-surface TF protein levels decreased in parallel to TF functional activity under staurosporine treatment. Moreover, Northern blot analysis of total RNA from LPS- or PMA-stimulated monocytes showed a concentration-dependent decrease in TF mRNA levels in response to H7 and staurosporine. The decay rate of LPS-induced TF mRNA evaluated after the arrest of transcription by actinomycin D was not affected by the addition of staurosporine, suggesting that its inhibitory effect occurred at a transcriptional level. We conclude that LPS-induced production of TF and its mRNA by human monocytes are dependent on PKC activation.

Tamoxifen inhibits phorbol ester stimulated osteoclastic bone resorption: An effect mediated by calmodulin

2000 ◽  
Vol 78 (6) ◽  
pp. 715-723 ◽  
Author(s):  
John P Williams ◽  
Margaret A McKenna ◽  
Allyn M Thames III ◽  
Jay M McDonald
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Bone Resorption ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Fold Increase ◽  
Dependent Manner ◽  
Osteoclast Activity ◽  
Kinase C ◽  
Protein Kinase Cα

Tamoxifen inhibits bone resorption by disrupting calmodulin-dependent processes. Since tamoxifen inhibits protein kinase C in other cells, we compared the effects of tamoxifen and the phorbol ester, phorbol myristate acetate, on osteoclast activity. Phorbol esters stimulate bone resorption and calmodulin levels four-fold (k0.5 = 0.1–0.3 µM). In contrast, tamoxifen inhibited osteoclast activity ~60% with an IC50 of 1.5 µM, had no apparent effect on protein kinase C activity in whole-cell lysates, and reduced protein kinase Cα recovered by immunoprecipitation 75%. Phorbol esters stimulated resorption in a time-dependent manner that was closely correlated with a similar-fold increase in calmodulin. Protein kinase Cα, β, δ, ε, and ζ were all down-regulated in response to phorbol ester treatment. Tamoxifen and trifluoperazine inhibited PMA-dependent increases in bone resorption and calmodulin by 85 ± 10%. Down-regulation of protein kinase C isoforms by phorbol esters suggests that the observed increases in bone resorption and calmodulin levels are most likely due to a mechanism independent of protein kinase C and dependent on calmodulin. In conclusion, the data suggest that protein kinase C negatively regulates calmodulin expression and support the hypothesis that the effects of both phorbol esters and tamoxifen on osteoclast activity is mediated by calmodulin.Key words: osteoclast, calmodulin, tamoxifen, osteoporosis, protein kinase C.

DIACYLGLYCEROL AND PHORBOL ESTER REDUCE AEQUORIN-INDICATED [Ca++] ELEVATIONS INDUCED BY THROMBIN OR ADP

1987 ◽  
Author(s):  
J A Ware ◽  
M Smith ◽  
E W Salzman
Keyword(s):  
Protein Kinase C ◽  
Platelet Aggregation ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Time Dependent ◽  
Dependent Manner ◽  
Kinase C ◽  
Protein Kinase C Activators ◽  
Protein Kinase C Inhibitor ◽  
Ca Homeostasis

Platelet aggregation and secretion induced by phorbol ester (PMA) or diacylglycerol (DAG) are preceded by an increase in [Ca++] that is detected byaequorin, but not by quin2, fura-2, or indo-1, suggesting that these indicatorsreflect different aspects of Ca++ homeostasis, possibly different functional Ca++ pools. Addition of two conventional agonists in subthreold concentrations synergistically enhances the [Ca++] rise and aggregation.However, if PMA or DAG is the first agonist the subsequent quin2-indicated [Ca++] rise after thrombin is reduced.Whether aequorin-indicated [Ca++] is similarly affected is unknown. We studied gel-filtered platelets loaded with aequorin or a fluorophore and added PMA, DAG, thrombin or ADP, alone or in combination. Either PMA or DAG alone caused a concentration-dependent increase in [Ca++] detectable with aequorin but not with the fluorophores; simultaneous addition of thrombin or ADP with DAG or PMA produced a larger [Ca++] rise than either alone. However, addition of DAG or PMA as a first agonist reduced subsequent aequorin-indicated [Ca++] rises following thrombin or ADP in a concentration and time-dependent manner. Inhibition of ADP or thrombin-induced [Ca++] rise was not always accompanied by inhibition of aggregation or secretion. Combination of subthreshold concentrations of ADP and thrombin produced an enhanced [Ca++] rise and aggregation. However, this synergistic effect was inhibited by preincubation with DAG or PMA. Neither this effect nor DAG-induced [Ca++] rise was inhibited by the protein kinase C inhibitor H-7. In genera^ preincubation of platelets with an agonist enhances Ca rise and aggregation in response to a second agonist; in contrasl protein kinase C activators, which themselves elevate [Ca++] as shown by aequorin, inhibit aequorin-indicated Ca rises after ADP or thrombin, and limit synergism between these two agonists.

Phorbol ester binding and protein kinase c activity in aging rat brain

1988 ◽  
Vol 20 ◽  
pp. 27
Author(s):  
F. Battaini ◽  
R. Del Vesco ◽  
A. Gagnoni ◽  
S. Govoni ◽  
M. Trabucchi
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Rat Brain ◽  
Phorbol Ester ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Aging Rat

scholarly journals Phorbol ester promotes histone H3-Ser10 phosphorylation at the LDL receptor promoter in a protein kinase C-dependent manner

2004 ◽  
Vol 45 (8) ◽  
pp. 1519-1527 ◽  
Author(s):  
Wei Huang ◽  
Vachaspati Mishra ◽  
Sanjay Batra ◽  
Ishan Dillon ◽  
Kamal D. Mehta
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Histone H3 ◽  
Ldl Receptor ◽  
Dependent Manner ◽  
Kinase C

scholarly journals Comparison of effects of phorbol esters and glucose on protein kinase C activation and insulin secretion in pancreatic islets

1989 ◽  
Vol 264 (1) ◽  
pp. 27-33 ◽  
Author(s):  
R A Easom ◽  
J H Hughes ◽  
M Landt ◽  
B A Wolf ◽  
J Turk ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Insulin Secretion ◽  
Protein Kinase ◽  
Pancreatic Islets ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Protein Kinase Activity ◽  
Isolated Pancreatic Islets ◽  
Kinase C ◽  
Protein Kinase C Activity

The tumour-promoting phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) induces insulin secretion from isolated pancreatic islets, and this suggests a potential role for protein kinase C in the regulation of stimulus-secretion coupling in islets. In the present study, the hypothesis that the insulinotropic effect of TPA is mediated by activation of protein kinase C in pancreatic islets has been examined. TPA induced a gradual translocation of protein kinase C from the cytosol to a membrane-associated state which correlated with the gradual onset of insulin secretion. The pharmacologically inactive phorbol ester 4 alpha-phorbol 12,13-didecanoate did not mimic this effect. TPA also induced a rapid time-dependent decline of total protein kinase C activity in islets and the appearance of a Ca2+- and phospholipid-independent protein kinase activity. Insulin secretion induced by TPA was completely suppressed (IC50 approximately 10 nM) by staurosporine, a potent protein kinase C inhibitor. Staurosporine also inhibited islet cytosolic protein kinase C activity at similar concentrations (IC50 approximately 2 nM). In addition, staurosporine partially (approximately 60%) inhibited glucose-induced insulin secretion at concentrations (IC50 approximately 10 nM) similar to those required to inhibit TPA-induced insulin secretion, suggesting that staurosporine may act at a step common to both mechanisms, possibly the activation of protein kinase C. However, stimulatory concentrations of glucose did not induce down-regulation of translocation of protein kinase C, and the inhibition of glucose-induced insulin release by staurosporine was incomplete. Significant questions therefore remain unresolved as to the possible involvement of protein kinase C in glucose-induced insulin secretion.

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