scholarly journals Modulation of platelet-activating-factor-induced calcium influx and intracellular calcium release in platelets by phorbol esters

1987 ◽  
Vol 247 (3) ◽  
pp. 669-674 ◽  
Author(s):  
F H Valone ◽  
B Johnson
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Intracellular Calcium ◽  
Calcium Release ◽  
Phorbol Esters ◽  
Calcium Influx ◽  
Platelet Activating Factor ◽  
Kinase C ◽  
Kinetics Of ◽  
Activate Protein Kinase

The mechanisms by which platelet-activating factor (PAF) and thrombin increase intracellular calcium were examined. Platelets were loaded with the calcium-sensitive fluorescent probe Quin 2 and then were suspended in buffer containing 0.5 mM-Mn2+ in order to quantify simultaneously calcium release from intracellular stores and divalent cation influx. Pretreating platelets with agents which activate protein kinase C [the phorbol ester phorbol myristate acetate (PMA) or the diacylglycerol 1-oleoyl-2-acetylglycerol (OAG)] inhibited increased intracellular calcium by PAF and thrombin in a dose-related manner. That protein kinase C regulates intracellular calcium by phosphorylating proteins in two distinct pathways was suggested by two observations. PAF-induced calcium release was more sensitive to inhibition by PMA and OAG than was manganese influx and the kinetics of recovery from inhibition were different for the two pathways. Both PMA and OAG aggregated Quin 2-loaded platelets without eliciting measurable increases in intracellular calcium. In contrast, prostacyclin, which increases intracellular cyclic AMP, inhibited calcium release and influx in parallel, suggesting that this agent acts at a step common to both pathways.

Effect of phorbol esters on contractile state and calcium flux in cultured chick heart cells

1987 ◽  
Vol 253 (1) ◽  
pp. H205-H209 ◽  
Author(s):  
G. F. Leatherman ◽  
D. Kim ◽  
T. W. Smith
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Calcium Flux ◽  
Heart Cells ◽  
Maximal Effect ◽  
Contractile State ◽  
Kinase C ◽  
45Ca Fluxes ◽  
Activate Protein Kinase

Phorbol esters are potent tumor promoters that have been widely used in studies of transmembrane signaling because of their ability to activate protein kinase C. To study the effect of phorbol esters (and indirectly, the role of protein kinase C) on cardiac muscle contractility, we examined the effects of phorbol myristate acetate (PMA) on contractile state, transmembrane 45Ca fluxes, and cytosolic free Ca concentration ([Ca]i) using spontaneously contracting cultured chick ventricular cells. PMA produced a concentration- and time-dependent decrease in the amplitude of cell motion [half maximum inhibitory concentration (IC50) = 130 nM] with maximal effect (54 +/- 5% of control) observed at 1 microM. PMA (1 microM) reduced 45Ca uptake rate by 16 +/- 4% (P less than 0.05) and the size of the rapidly exchangeable Ca pool by 11 +/- 2% (P less than 0.05) but did not alter the 45Ca efflux rate. In fura-2-loaded cells, PMA produced a decrease in [Ca]i from 96 +/- 7 to 72 +/- 5 nM (mean +/- SE; P less than 0.05) with a time course similar to that of alteration in contractile amplitude. PMA had no effect on cellular Na content. Phorbol didecanoate (1 microM), a phorbol diester that does not activate protein kinase C, produced no significant changes in contractile amplitude, 45Ca fluxes, or [Ca]i. These results indicate that PMA influences transsarcolemmal Ca uptake, and thus the excitation-contraction process, and suggest that protein kinase C may modulate myocardial Ca homeostasis and contractile state.

scholarly journals Protein kinase C- and calcium-regulated pathways independently synergize with Gi pathways in agonist-induced fibrinogen receptor activation

2002 ◽  
Vol 368 (2) ◽  
pp. 535-543 ◽  
Author(s):  
Todd M. QUINTON ◽  
Soochong KIM ◽  
Carol DANGELMAIER ◽  
Robert T. DORSAM ◽  
Jianguo JIN ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Intracellular Calcium ◽  
Phospholipase C ◽  
Calcium Release ◽  
Receptor Activation ◽  
Dense Granule ◽  
Fibrinogen Receptor ◽  
Kinase C ◽  
Induced Aggregation

Platelet fibrinogen receptor activation is a critical step in platelet plug formation. The fibrinogen receptor (integrin αIIbβ3) is activated by agonist-mediated Gq stimulation and resultant phospholipase C activation. We investigated the role of downstream signalling events from phospholipase C, namely the activation of protein kinase C (PKC) and rise in intracellular calcium, in agonist-induced fibrinogen receptor activation using Ro 31-8220 (a PKC inhibitor) or dimethyl BAPTA [5,5′-dimethyl-bis-(o-aminophenoxy)ethane-N,N,N′,N′-tetra-acetic acid], a high-affinity calcium chelator. All the experiments were performed with human platelets treated with aspirin, to avoid positive feedback from thromboxane A2. In the presence of Ro 31-8220, platelet aggregation caused by U46619 was completely inhibited while no effect or partial inhibition was seen with ADP and the thrombin-receptor-activating peptide SFLLRN, respectively. In the presence of intracellular dimethyl BAPTA, ADP- and U46619-induced aggregation and anti-αIIbβ3 antibody PAC-1 binding were completely abolished. However, similar to the effects of Ro 31-8220, dimethyl BAPTA only partially inhibited SFLLRN-induced aggregation, and was accompanied by diminished dense-granule secretion. When either PKC activation or intracellular calcium release was abrogated, aggregation and fibrinogen receptor activation with U46619 or SFLLRN was partially restored by additional selective activation of the Gi signalling pathway. In contrast, when both PKC activity and intracellular calcium increase were simultaneously inhibited, the complete inhibition of aggregation that occurred in response to either U46619 or SFLLRN could not be restored with concomitant Gi signalling. We conclude that, while the PKC- and calcium-regulated signalling pathways are capable of inducing activating fibrinogen receptor independently and that each can synergize with Gi signalling to cause irreversible fibrinogen receptor activation, both pathways act synergistically to effect irreversible fibrinogen receptor activation.

scholarly journals Release of superoxide and change in morphology by neutrophils in response to phorbol esters: antagonism by inhibitors of calcium-binding proteins.

1985 ◽  
Vol 101 (3) ◽  
pp. 1052-1058 ◽  
Author(s):  
J M Robinson ◽  
J A Badwey ◽  
M L Karnovsky ◽  
M J Karnovsky
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Guinea Pig ◽  
Calcium Binding ◽  
Binding Proteins ◽  
Phorbol Esters ◽  
Morphological Changes ◽  
Calcium Binding Proteins ◽  
Kinase C ◽  
Activate Protein Kinase

The ability of phorbol derivatives to function as stimulating agents for superoxide (O2-) release by guinea pig neutrophils has been evaluated and compared to the known ability of each compound to activate protein kinase C. Those that activate the kinase also stimulate O2- release, while those that are inactive with respect to the kinase have no effect on O2- release. The same correlation was observed with respect to the ability of phorbol esters to induce morphological changes in neutrophils, i.e., vesiculation and reduction in granule content. Certain phenothiazines and naphthalene sulfonamides that are known antagonists of calcium-binding proteins blocked both phorbol ester-induced O2- release and morphological changes in these cells.

scholarly journals Mechanism of inhibitory action of TMB-8 [8-(NN-diethylamino)octyl-3,4,5-trimethoxybenzoate] on aldosterone secretion in adrenal glomerulosa cells

1985 ◽  
Vol 232 (1) ◽  
pp. 87-92 ◽  
Author(s):  
I Kojima ◽  
K Kojima ◽  
H Rasmussen
Keyword(s):  
Protein Kinase C ◽  
Angiotensin Ii ◽  
Protein Kinase ◽  
Calcium Release ◽  
Calcium Influx ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Aldosterone Secretion ◽  
Kinase C ◽  
Glomerulosa Cells

The mechanism of 8-(NN-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) action was evaluated in isolated adrenal glomerulosa cells. TMB-8 inhibits both angiotensin II- and K+-stimulated aldosterone secretion in a dose-dependent manner. The ID50 for angiotensin II- and K+-stimulated aldosterone secretion is 46 and 28 microM, respectively. In spite of the fact that 100 microM-TMB-8 inhibits angiotensin II-stimulated aldosterone secretion almost completely, TMB-8 (100 microM) does not inhibit angiotensin II-induced 45Ca2+ efflux from prelabelled cells nor does it affect inositol 1,4,5-trisphosphate-induced calcium release from non-mitochondrial pool(s) in saponin-permeabilized cells. TMB-8 has no inhibitory effect on A23187-induced aldosterone secretion, but 12-O-tetradecanoylphorbol 13-acetate-induced aldosterone secretion is completely abolished. TMB-8 effectively inhibits both angiotensin II- and K+-induced increases in calcium influx but has no effect on A23187-induced calcium influx. TMB-8 inhibits the activity of protein kinase C dose-dependently. These results indicate that TMB-8 inhibits aldosterone secretion without inhibiting mobilization of calcium from an intracellular pool. The inhibitory effect of TMB-8 is due largely to an inhibition of plasma membrane calcium influx, but this drug also inhibits the activity of protein kinase C directly.

scholarly journals Thapsigargin potentiates histamine-stimulated HCl secretion in gastric parietal cells but does not mimic cholinergic responses.

1991 ◽  
Vol 2 (1) ◽  
pp. 27-39 ◽  
Author(s):  
C S Chew ◽  
A C Petropoulos
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Intracellular Calcium ◽  
Parietal Cell ◽  
Calcium Release ◽  
Parietal Cells ◽  
Kinase C ◽  
Hcl Secretion ◽  
Protein Kinase C Activation ◽  
Cholinergic Response

The role of calcium in control of HCl secretion by the gastric parietal cell was examined using a recently available intracellular calcium-releasing agent, thapsigargin, which has been shown, in some cell types, to induce sustained elevation of intracellular calcium ([Ca2+]i), an action that appears to be independent of inositol lipid breakdown and protein kinase C activation and to be mediated, at least partially, by selective inhibition of endoplasmic reticulum Ca2(+)-ATPase. Using the calcium-sensitive fluorescent probe, fura-2, in combination with digitized video image analysis of single cells as well as standard fluorimetric techniques, we found that thapsigargin induced sustained elevation of [Ca2+]i in single parietal cells and in parietal cells populations. Chelation of medium calcium led to a transient rise and fall in [Ca2+]i, indicating that the sustained elevation in [Ca2+]i in response to thapsigargin was due to both intracellular calcium release and influx. Although thapsigargin appeared to affect the same calcium pool(s) regulated by the cholinergic agonist, carbachol, and the pattern of thapsigargin-induced increases in [Ca2+]i were similar to the plateau phase of the cholinergic response, thapsigargin did not induce acid secretory responses of the same magnitude as those initiated by carbachol (28 vs 600% of basal). The protein kinase C activator, 12-O-tetradecanoyl phorbol-13-acetate (TPA) potentiated the secretory response to thapsigargin but this combined response also did not attain the same magnitude as the maximal cholinergic response. In the presence but not the absence of medium calcium, thapsigargin potentiated acid secretory responses to histamine, which elevate both cyclic AMP (cAMP) and [Ca2+]i in parietal cells, as well as forskolin and cAMP analogues but had no effect on submaximal and an inhibitory effect on maximal cholinergic stimulation. Furthermore, thapsigargin did not fully mimic potentiating interactions between histamine and carbachol, either in magnitude or in the pattern of temporal response. Assuming that the action of thapsigargin is specific for intracellular calcium release mechanisms, these data suggest that 1) sustained influx of calcium is necessary but not sufficient for cholinergic activation of parietal cell HCl secretion and for potentiating interactions between cAMP-dependent agonists and carbachol; 2) mechanisms in addition to elevated [Ca2+]i and protein kinase C activation may be involved in cholinergic regulation; and 3) increases in [Ca2+]i in response to histamine are not directly involved in the mechanism of histamine-stimulated secretion.

scholarly journals Diacylglycerol induces deacylation of phosphatidylinositol and mobilization of arachidonic acid in mouse macrophages Comparison with induction by phorbol diester

1986 ◽  
Vol 239 (3) ◽  
pp. 685-690 ◽  
Author(s):  
A Emilsson ◽  
J Wijkander ◽  
R Sundler
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Intracellular Calcium ◽  
Phorbol Myristate Acetate ◽  
Myristate Acetate ◽  
Sequence Of Events ◽  
Kinase C ◽  
Mouse Macrophages ◽  
Activate Protein Kinase

1,2-Dioctanoyl-sn-glycerol (2-50 microM) was found, like phorbol myristate acetate (greater than or equal to 3 nM) to stimulate phospholipase A-type cleavage of phosphatidylinositol and the release of arachidonic acid from macrophage phospholipids. The 1,3 isomer of dioctanoylglycerol was inactive, whereas racemic 1,2-dioctanoylglycerol was half as potent as the 1,2-sn enantiomer. Dioctanoylglycerol-induced deacylation of phosphatidylinositol was only partly dependent on extracellular calcium but was more severely inhibited by depletion of intracellular calcium. Chlorpromazine inhibited the deacylation of phosphatidylinositol, whereas inhibitors of cyclo-oxygenase and lipoxygenase were ineffective. Since both phorbol myristate acetate and 1,2-dioctanoyl-sn-glycerol are known to activate protein kinase C, the results suggest that this kinase is involved in the sequence of events leading to release of arachidonic acid in macrophages.

Activation of protein kinase C inhibits synthesis and release of decidual prolactin

1986 ◽  
Vol 251 (2) ◽  
pp. E172-E177
Author(s):  
I. Harman ◽  
A. Costello ◽  
B. Ganong ◽  
R. M. Bell ◽  
S. Handwerger
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Dependent Manner ◽  
Prolactin Release ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Decidual Cells ◽  
Prolactin Synthesis ◽  
Activate Protein Kinase

Activation of calcium-activated, phospholipid-dependent protein kinase C by diacylglycerol and phorbol esters has been shown to mediate release of hormones in many systems. To determine whether protein kinase C activation is also involved in the regulation of prolactin release from human decidua, we have examined the effects of various acylglycerols and phorbol esters on the synthesis and release of prolactin from cultured human decidual cells. sn-1,2-Dioctanoylglycerol (diC8), which is known to stimulate protein kinase C in other systems, inhibited prolactin release in a dose-dependent manner with maximal inhibition of 53.1% (P less than 0.01) at 100 microM. Diolein (100 microM), which also stimulates protein kinase C activity in some systems, inhibited prolactin release by 21.3% (P less than 0.05). Distearin and dipalmitin, which are much less effective in activating protein kinase C, and monopalmitin and tripalmitin, which do not activate protein kinase C, had no significant effect on prolactin release. Phorbol 12-myristate 13-acetate (PMA), phorbol 12,13-didecanoate, and 4 beta-phorbol 12,13-dibutyrate, which activate protein kinase C in other systems, also inhibited the release of prolactin, while the protein kinase C inactivate 4 alpha-phorbol-12,13-didecanoate was without effect. The inhibition of prolactin release was secondary to a decrease in prolactin synthesis. The amounts of prolactin synthesized by cells exposed to diC8 (300 microM) or PMA (10(-7) M) for 30 min were 56.3 and 50.0% less than that synthesized by control cells (P less than 0.01 in each instance).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of phorbol esters and diacylglycerol on steroid metabolism in isolated rat hepatocytes

1988 ◽  
Vol 118 (1) ◽  
pp. 19-23 ◽  
Author(s):  
C. J. Allan ◽  
P. Skett
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Rat Hepatocytes ◽  
Male Rats ◽  
Steroid Metabolism ◽  
Isolated Rat Hepatocytes ◽  
Kinase C ◽  
Activate Protein Kinase

ABSTRACT Hepatocytes, isolated from adult male rats and maintained in serum- and hormone-free medium, were pretreated with phorbol esters known to activate protein kinase C (4β-phorbol-12-myristate-13-acetate) and to be inactive in this respect (4α-phorbol and its 12,13-didecanoate ester). Subsequently the cells were assayed for steroid-metabolizing capacity using androst-4-ene-3,17-dione as substrate. The active phorbol ester was seen to inhibit steroid metabolism markedly after 1 h whereas the inactive derivatives did not show this effect. The endogenous activator of protein kinase C (diacylglycerol) was also seen to inhibit steroid metabolism in a manner similar to the 4β-phorbol ester. Hepatic steroid metabolism is, thus, inhibited by activation of protein kinase C and this may be one of the mechanisms by which the regulatory hormones (e.g. growth hormone) affect steroid metabolism in the liver. J. Endocr. (1988) 118, 19–23

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