Time-dependent translocation of the α and β1 isotypes of protein kinase C in human platelets in response to phorbol ester stimulation

1997 ◽  
Vol 25 (1) ◽  
pp. 44S-44S
Author(s):  
Jacqueline M. Kew ◽  
W. Jonathan Ryves ◽  
Fred J. Evans
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Human Platelets ◽  
Time Dependent ◽  
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.

scholarly journals Inhibition of mitogen-activated protein kinase kinase does not impair primary activation of human platelets

1996 ◽  
Vol 318 (1) ◽  
pp. 207-212 ◽  
Author(s):  
Angelika G. BÖRSCH-HAUBOLD ◽  
Ruth M. KRAMER ◽  
Steve P WATSON
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Substrate Inhibition ◽  
Human Platelets ◽  
Mitogen Activated Protein Kinase ◽  
Ionophore A23187 ◽  
Kinase C ◽  
Mitogen Activated Protein

Mitogen-activated protein kinases (MAPKs), a family of protein serine/threonine kinases regulating cell growth and differentiation, are activated by a dual-specificity kinase through phosphorylation at threonine and tyrosine. We used a recently described selective inhibitor of the p42/p44mapk-activating enzyme, PD 98059 [2-(2´-amino-3´-methoxyphenyl)-oxanaphthalen-4-one], to investigate the role of the p42/p44mapk pathway in human platelets. PD 98059 inhibited p42/p44mapk activation in thrombin-, collagen- and phorbol ester-stimulated platelets, as determined from in-gel renaturation kinase assays, with an IC50 of approx. 5 µM (thrombin stimulation). It also prevented activation of MAPK kinase, which was measured in whole-cell lysates with glutathione S-transferase/p42mapk fusion protein (GST–MAPK) as substrate. Inhibition of p42/p44mapk did not affect platelet responses to thrombin or collagen such as aggregation, 5-hydroxytryptamine release and protein kinase C activation. In addition, PD 98059 did not interfere with release of arachidonic acid, a response mediated by cytosolic phospholipase A2 (cPLA2), or with cPLA2 phosphorylation. This suggests that platelet cPLA2 is not regulated by p42/p44mapk after stimulation with physiological agonists. In contrast, phorbol ester-induced phosphorylation of cPLA2 and potentiation of arachidonic acid release stimulated by Ca2+ ionophore A23187 were inhibited by PD 98059, indicating that p42/p44mapk phosphorylates cPLA2 after activation of protein kinase C by the non-physiological tumour promoter.

scholarly journals Activation of Na+/H+ exchange in human platelets stimulated by thrombin and a phorbol ester

1987 ◽  
Vol 241 (1) ◽  
pp. 301-303 ◽  
Author(s):  
W Siffert ◽  
G Siffert ◽  
P Scheid
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Fluorescent Probe ◽  
Phorbol Ester ◽  
Human Platelets ◽  
Cytoplasmic Ph ◽  
Kinase C ◽  
Stimulation Of

We have investigated changes in cytoplasmic pH (pHi) in activated human platelets, using the fluorescent probe 2,7-biscarboxyethyl-5(6)-carboxyfluorescein. Stimulation of platelets by thrombin or 12-O-tetradecanoylphorbol 13-acetate increased pHi by about 0.11 pH unit above the resting value. This increase in pHi depended on the presence of external Na+ and was inhibited by ethylisopropylamiloride. The data suggest that protein kinase C mediates Na+/H+ exchange in human platelets.

scholarly journals Effects of prostaglandin I2 and forskolin on the secretion from platelets evoked at basal concentrations of cytoplasmic free calcium by thrombin, collagen, phorbol ester and exogenous diacylglycerol

1984 ◽  
Vol 222 (3) ◽  
pp. 833-836 ◽  
Author(s):  
T J Rink ◽  
A Sanchez
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Human Platelets ◽  
Free Calcium ◽  
Prostaglandin I2 ◽  
Kinase C ◽  
Inositol Lipids ◽  
Hydrolysis Of ◽  
Cytoplasmic Free Calcium

Cytoplasmic free calcium ([Ca2+]i) and secretion of ATP were measured in quin2-loaded human platelets. In certain conditions thrombin and collagen cause secretion while [Ca2+]i remains at basal concentrations, a response attributed to activation of protein kinase by diacylglycerol formed by hydrolysis of inositol lipids. This secretion evoked by thrombin could be totally suppressed by prostaglandin I2 or forskolin, as expected from the known ability of cyclic AMP to inhibit phospholipase C. The secretory response evoked by collagen at basal [Ca2+]i and that evoked by exogenous diacylglycerol or phorbol ester, direct activators of protein kinase-C, were much less affected by these inhibitors, suggesting that thrombin and collagen may promote formation of diacylglycerol by different mechanisms.

Phorbol ester-induced activation of human platelets is associated with protein kinase C phosphorylation of myosin light chains

Nature ◽  
1983 ◽  
Vol 306 (5942) ◽  
pp. 490-492 ◽  
Author(s):  
Michiko Naka ◽  
Masakatsu Nishikawa ◽  
Robert S. Adelstein ◽  
Hiroyoshi Hidaka
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Human Platelets ◽  
Light Chains ◽  
Myosin Light Chains ◽  
Kinase C

scholarly journals Ethanol inhibits thrombin-induced secretion by human platelets at a site distinct from phospholipase C or protein kinase C

1990 ◽  
Vol 269 (2) ◽  
pp. 489-497 ◽  
Author(s):  
C Benistant ◽  
R Rubin
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Phorbol Ester ◽  
Inositol Phosphates ◽  
Shape Change ◽  
Protein A ◽  
Human Platelets ◽  
Kinase C ◽  
A Site

Ethanol is known to inhibit the activation of platelets in response to several physiological agonists, but the mechanism of this action is unclear. The addition of physiologically relevant concentrations of ethanol (25-150 mM) to suspensions of washed human platelets resulted in the inhibition of thrombin-induced secretion of 5-hydroxy[14C]tryptamine. Indomethacin was included in the incubation buffer to prevent feedback amplification by arachidonic acid metabolites. Ethanol had no effect on the activation of phospholipase C by thrombin, as determined by the formation of inositol phosphates and the mobilization of intracellular Ca2+. Moreover, ethanol did not interfere with the thrombin-induced formation of diacylglycerol or phosphatidic acid. Stimulation of platelets with phorbol ester (5-50 nM) resulted in 5-hydroxy[14C]tryptamine release comparable with those with threshold doses of thrombin. However, ethanol did not inhibit phorbol-ester-induced secretion. Ethanol also did not interfere with thrombin- or phorbol-ester-induced phosphorylation of myosin light chain (20 kDa) or a 47 kDa protein, a known substrate for protein kinase C. By electron microscopy, ethanol had no effect on thrombin-induced shape change and pseudopod formation, but prevented granule centralization and fusion. The results indicate that ethanol does not inhibit platelet secretion by interfering with the activation of phosphoinositide-specific phospholipase C or protein kinase C by thrombin. Rather, the data demonstrate an inhibition of a Ca2(+)-mediated event such as granule centralization.

scholarly journals Effect of tumour-promoting phorbol ester, thrombin and vasopressin on translocation of three distinct protein kinase C isoforms in human platelets and regulation by calcium

1992 ◽  
Vol 288 (3) ◽  
pp. 891-896 ◽  
Author(s):  
M Crabos ◽  
D Fabbro ◽  
S Stabel ◽  
P Erne
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Human Platelets ◽  
Second Phase ◽  
Percentage Increase ◽  
Control Value ◽  
Kinase C ◽  
Pkc Isoforms ◽  
Alpha Beta

Protein kinase C (PKC) acts in synergy with Ca2+ mobilization for the activation of platelets. Three different PKC subtypes that specifically react with antibodies to alpha- beta- and zeta-PKC have been detected in human platelets. We have compared the subcellular redistribution of these isoforms in platelets after exposure to the tumour-promoting phorbol ester phorbol 12-myristate 13-acetate (PMA) and to two physiological agonists, thrombin and vasopressin. In the presence of PMA, beta-PKC is most rapidly translocated to membranes, followed by zeta-PKC and alpha-PKC [membrane contents of 39 +/- 6, 31 +/- 4 and 24 +/- 4% (means +/- S.E.M.) respectively after 2 min incubation]. In contrast, both thrombin and vasopressin induced a biphasic translocation of PKC isoforms. For both agonists, the first phase of translocation occurred within 1 min and was identical for the three isoforms. However, during the second phase, the translocation of zeta-PKC by thrombin and vasopressin differed [membrane contents (mean +/- S.E.M.) of 24 +/- 3 and 46 +/- 4% respectively after 10 min]. These results suggest a differential activation of zeta-PKC by vasopressin and thrombin. PMA-induced translocation of alpha-PKC was decreased from 278 +/- 27 to 198 +/- 24 (mean +/- S.E.M., P = 0.02; percentage increase over control value) in the presence of 1 mM-EDTA, whereas chelation of intracellular Ca2+ by Quin2-AM does not influence this response. These results suggest that the PMA-induced translocation of alpha-PKC depends on the presence of 1 mM concentration of extracellular Ca2+. In addition, the chelation of either extracellular or intracellular Ca2+ inhibited both vasopressin- and thrombin-induced translocation of all three isoforms, suggesting that Ca2+ is an important requirement for the translocation of alpha-, beta- and zeta-PKC by physiological agonists. In conclusion, the translocation of PKC varies between different isoforms and between different agonists.

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