scholarly journals The diacylglycerol analogue, 1,2-sn-dioctanoylglycerol, induces an increase in cytosolic free Ca2+ and cytosolic acidification of T lymphocytes through a protein kinase C-independent process

1989 ◽  
Vol 258 (3) ◽  
pp. 689-698 ◽  
Author(s):  
R Ebanks ◽  
C Roifman ◽  
A Mellors ◽  
G B Mills
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
T Lymphocytes ◽  
Cell Activation ◽  
Phorbol Esters ◽  
Inositol Phosphates ◽  
Free Calcium ◽  
Intact Cells ◽  
Kinase C ◽  
Cytosolic Acidification

In this paper, we demonstrate that low concentrations (0.5-2.5 microM) of 1,2-sn-dioctanoylglycerol (DiC8), a potent diacylglycerol used in many previous studies to probe the role of protein kinase C (PKC) in cell activation, cause cytosolic alkalinization of human, mouse and pig T lymphocytes through PKC-mediated activation of the Na+/H+ antiport. However, at higher concentrations (greater than or equal to 12.5 microM), the effect on cytosolic pH (pHi) is reversed, resulting in a marked cytosolic acidification, followed by a gradual return of pHi to baseline values. DiC8 also induces marked changes in cytosolic free calcium concentrations ([Ca2+]i), initially by releasing calcium from intracellular stores, followed by a net transmembrane influx of calcium. The DiC8-induced cytosolic acidification, the resultant return to baseline pH and the increase in [Ca2+]i are independent of activation of PKC. Unlike many other agents which increase [Ca2+]i, DiC8 does not induce phosphatidylinositol hydrolysis with the resultant production of inositol phosphates. Other compounds known to activate PKC, including the closely related diacylglycerol analogues, 1,2-sn-dihexanoylglycerol and 1,2-sn-didecanoylglycerol, phorbol esters and mezerein, did not induce changes in [Ca2+]i or cytosolic acidification in T lymphocytes. Thus the action of DiC8 on intact lymphocytes is different from that of phorbol esters and other diacylglycerols, and is specific to the length of the acyl chains. Because changes in [Ca2+]i are often associated with cell proliferation and cell differentiation, some effects of DiC8 on intact cells may be a consequence of changes in [Ca2+]i.

scholarly journals Ethanol-induced phospholipase C activation is inhibited by phorbol esters in isolated hepatocytes

1988 ◽  
Vol 251 (3) ◽  
pp. 865-871 ◽  
Author(s):  
J B Hoek ◽  
R Rubin ◽  
A P Thomas
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phospholipase C ◽  
Phorbol Esters ◽  
Inositol Phosphates ◽  
Isolated Hepatocytes ◽  
Intact Cells ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Activate Protein Kinase

Ethanol causes a transient activation of the phosphoinositide-specific phospholipase C in intact hepatocytes and mimics the action of receptor-mediated agonists [Hoek, Thomas, Rubin & Rubin (1987) J. Biol. Chem. 262, 682-691]. Preincubation of the hepatocytes with phorbol esters which activate protein kinase C prevented this effect of ethanol: phorbol ester treatment inhibited the ethanol-induced phosphorylase activation, the increase in intracellular free Ca2+ concentrations measured in quin 2-loaded hepatocytes, and the changes in concentrations of inositol phosphates, phosphoinositides and phosphatidic acid. Several lines of evidence indicate that these effects were mediated by protein kinase C. Phorbol esters acted in a concentration range where they activate protein kinase C; phorbol esters that do not activate protein kinase C were not effective in inhibiting the effects of ethanol. The permeant diacylglycerol oleoyl-acetylglycerol also inhibited the effects of ethanol, but other diacylglycerols were not effective in the intact cells. The inhibition of ethanol-induced Ca2+ mobilization by phorbol esters was prevented by preincubating the cells with the protein kinase C inhibitors 1-(5-isoquinolinesulphonyl)-2-methylpiperazine (H7) and sphingosine. H7 also enhanced the Ca2+ mobilization induced by ethanol in cells that were not pretreated with phorbol esters, indicating that the transient nature of the ethanol-induced Ca2+ mobilization may be due to an activation of protein kinase C caused by the accumulation of diacylglycerol. These data support a model whereby ethanol activates the phosphoinositide-specific phospholipase C, possibly by affecting receptor-G-protein-phospholipase C interactions in the membrane.

Regulation of protein kinase C activity in neuronal differentiation induced by the N-ras oncogene in PC-12 cells

1990 ◽  
Vol 10 (6) ◽  
pp. 2983-2990
Author(s):  
J C Lacal ◽  
A Cuadrado ◽  
J E Jones ◽  
R Trotta ◽  
D E Burstein ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Neuronal Differentiation ◽  
Phorbol Esters ◽  
Ras Oncogene ◽  
Intact Cells ◽  
Pc 12 Cells ◽  
Kinase C ◽  
Ras P21

Expression of the N-ras oncogene under the control of the glucocorticoid-responsive promoter in the pheochromocytoma cell line UR61, a subline of PC-12 cells, has been used to investigate the differentiation process to neuronal cells triggered by ras oncogenes (I. Guerrero, A. Pellicer, and D. E. Burstein, Biochem. Biophys. Res. Commun. 150:1185-1192, 1988). Using ras-inducible cell lines, we observed that expression of the oncogenic N-ras p21 protein interferes with the ability of phorbol esters to induce downregulation of protein kinase C. This effect was associated with the appearance of immunologically detectable protein kinase C as well as the activity of the enzyme as analyzed either by binding of [3H]phorbol-12,13-dibutyrate in intact cells or by in vitro kinase activity. These results indicate a relationship between ras p21 and protein kinase C in neuronal differentiation in this model system. Comparison to the murine fibroblast system suggests that this relationship may be functional.

scholarly journals Bombesin and platelet-derived growth factor stimulate formation of inositol phosphates and Ca2+ mobilization in Swiss 3T3 cells by different mechanisms

1989 ◽  
Vol 258 (1) ◽  
pp. 177-185 ◽  
Author(s):  
D M Blakeley ◽  
A N Corps ◽  
K D Brown
Keyword(s):  
Protein Kinase C ◽  
Growth Factor ◽  
Protein Kinase ◽  
Phorbol Esters ◽  
Inositol Phosphates ◽  
Platelet Derived Growth Factor ◽  
3T3 Cells ◽  
Kinase C ◽  
Swiss 3T3 ◽  
Stimulation Of

Highly purified platelet-derived growth factor (PDGF) or recombinant PDGF stimulate DNA synthesis in quiescent Swiss 3T3 cells. The dose-response curves for the natural and recombinant factors were similar, with half-maximal responses at 2-3 ng/ml and maximal responses at approx. 10 ng/ml. Over this dose range, both natural and recombinant PDGF stimulated a pronounced accumulation of [3H]inositol phosphates in cells labelled for 72 h with [3H]inositol. In addition, mitogenic concentrations of PDGF stimulated the release of 45Ca2+ from cells prelabelled with the radioisotope. However, in comparison with the response to the peptide mitogens bombesin and vasopressin, a pronounced lag was evident in both the generation of inositol phosphates and the stimulation of 45Ca2+ efflux in response to PDGF. Furthermore, although the bombesin-stimulated efflux of 45Ca2+ was independent of extracellular Ca2+, the PDGF-stimulated efflux was markedly inhibited by chelation of external Ca2+ by using EGTA. Neither the stimulation of formation of inositol phosphates nor the stimulation of 45Ca2+ efflux in response to PDGF were affected by tumour-promoting phorbol esters such as 12-O-tetradecanoylphorbol 13-acetate (TPA). In contrast, TPA inhibited phosphoinositide hydrolysis and 45Ca2+ efflux stimulated by either bombesin or vasopressin. Furthermore, whereas formation of inositol phosphates in response to both vasopressin and bombesin was increased in cells in which protein kinase C had been down-modulated by prolonged exposure to phorbol esters, the response to PDGF was decreased in these cells. These results suggest that, in Swiss 3T3 cells, PDGF receptors are coupled to phosphoinositidase activation by a mechanism that does not exhibit protein kinase C-mediated negative-feedback control and which appears to be fundamentally different from the coupling mechanism utilized by the receptors for bombesin and vasopressin.

scholarly journals Isolation and characterization of protein kinase C from Y-1 adrenal cell cytoskeleton.

1989 ◽  
Vol 108 (2) ◽  
pp. 553-567 ◽  
Author(s):  
V Papadopoulos ◽  
P F Hall
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Phorbol Esters ◽  
Intact Cells ◽  
Adrenal Cells ◽  
Isolation And Characterization ◽  
Kinase C

The cytoskeletons of Y-1 mouse adrenal tumor cells contain a calcium and phospholipid-dependent protein kinase (protein kinase C) that is bound sufficiently tight to resist extraction by 0.5% Triton but not by 1.0% Triton. The enzyme has been purified to near homogeneity from cytoskeleton and cytosol. It shows features typical of this type of kinase, namely a requirement for Ca2+ and phospholipid, stimulation by tumor promoters but not by nontumor-promoting phorbol esters, and inhibition by trifluoperazine. The enzyme shows specificity for four substrates found in the cytoskeleton, namely 80, 33, 20, and 18 kD. The first three substrates are phosphorylated by the enzyme; the fourth is dephosphorylated and is therefore affected by the kinase indirectly. The 80-kD protein is the kinase enzyme itself which is autophosphorylated in vitro and in the cytoskeleton. The 20-kD protein is myosin light chain. The 33- and 18-kD proteins are unidentified. The same substrates were phosphorylated when Y-1 cells were permeabilized with digitonin and incubated with [gamma-32P]ATP and phorbol-12-myristate-13-acetate. Partly purified protein kinase C changes the extent of phosphorylation of the same substrates when added to cytoskeletons previously extracted to remove endogenous protein kinase C. Addition of Ca2+, phosphatidylserine, and phorbol-12-myristate-13-acetate to cytoskeletons, and addition of these three agents plus protein kinase C to extracted cytoskeletons, causes these structures to undergo a rapid and extensive rounding. A similar change is induced in intact cells by addition of phorbol ester. It is concluded that protein kinase C is capable of changing the shape of adrenal cells by an action that involves autophosphorylation and phosphorylation of myosin light chain. This response may in turn be related to the steroidogenic responses to ACTH and cyclic AMP.

scholarly journals Inhibitors of protein kinase C prolong the falling phase of each free-calcium transient in a hormone-stimulated hepatocyte

1990 ◽  
Vol 268 (3) ◽  
pp. 627-632 ◽  
Author(s):  
A Sanchez-Bueno ◽  
C J Dixon ◽  
N M Woods ◽  
K S R Cuthbertson ◽  
P H Cobbold
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Time Course ◽  
Phorbol Esters ◽  
Calcium Transient ◽  
Free Calcium ◽  
Hormone Concentration ◽  
Rat Hepatocyte ◽  
Pkc Inhibitor ◽  
Kinase C

Many cells generate oscillations in cytoplasmic free Ca2+ concentration (‘free Ca’) when stimulated with Ca-mobilizing hormones. The frequency of repetitive free-Ca transients in a rat hepatocyte is a function of hormone concentration and can be depressed by phorbol esters. We show here that the protein kinase C (PKC) inhibitors staurosporine and sphingosine can reverse the effects of phorbol dibutyrate on the frequency of free-Ca transients induced by phenylephrine or vasopressin. An important feature of the hepatocyte free-Ca oscillator is that the transient's time course, particularly the rate of fall of free Ca from peak to resting, depends on the species of agonist, and is measurably different for phenylephrine, vasopressin, angiotensin II or ATP. We show here that the rate of fall of free Ca in transients induced by phenylephrine or vasopressin is markedly decreased after treatment of the cells with a PKC inhibitor. A receptor-controlled oscillator model is discussed, in which PKC provides negative feedback during the falling phase of free-Ca transients.

scholarly journals The action of the protein kinase C inhibitor, staurosporine, on human platelets. Evidence against a regulatory role for protein kinase C in the formation of inositol trisphosphate by thrombin

1988 ◽  
Vol 249 (2) ◽  
pp. 345-350 ◽  
Author(s):  
S P Watson ◽  
J McNally ◽  
L J Shipman ◽  
P P Godfrey
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phosphatidic Acid ◽  
Phorbol Esters ◽  
Inositol Phosphates ◽  
Protein A ◽  
Polymyxin B ◽  
Human Platelets ◽  
Phosphoinositide Metabolism ◽  
Kinase C

The ability of several putative inhibitors of protein kinase C (PKC) to block dioctanoylglycerol (DC8)-induced phosphorylation of a 47 kDa protein (a recognized substrate for PKC) in human platelets was investigated. Staurosporine (1 microM) caused complete inhibition of phosphorylation, whereas the other reagents were either inactive (polymyxin B) or gave only partial inhibition (C-1, H-7, tamoxifen). Staurosporine (1 microM) fully inhibited the phosphorylation of the 47 kDa protein in platelets challenged with thrombin, but also inhibited the phosphorylation of a 20 kDa protein which is a substrate for myosin light-chain kinase. The inhibition of both kinases by staurosporine was associated with the inhibition of thrombin-induced secretion of ATP and 5-hydroxytryptamine and a slowing of the aggregation response; staurosporine, however, had no effect on the formation of phosphatidic acid and inositol phosphates induced by thrombin. Staurosporine also reversed the inhibitory action of phorbol esters on thrombin-induced formation of phosphatidic acid. These data are consistent with a role for these two kinases in secretion and aggregation (although there must be additional control signals, since aggregation was only slowed, not inhibited), but suggest that neither kinase is involved in the regulation of phosphoinositide metabolism. This latter conclusion contradicts previous observations that the activation of PKC by phorbol esters or membrane-permeable diacylglycerols alters the apparent activity of both phospholipase C and inositol trisphosphatase. Possible explanations for this discrepancy are discussed.

scholarly journals Ca2+ and protein kinase C-dependent mechanisms involved in gastrin-induced Shc/Grb2 complex formation and P44-mitogen-activated protein kinase activation

1997 ◽  
Vol 325 (2) ◽  
pp. 383-389 ◽  
Author(s):  
Laurence DAULHAC ◽  
Aline KOWALSKI-CHAUVEL ◽  
Lucien PRADAYROL ◽  
Nicole VAYSSE ◽  
Catherine SEVA
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Tyrosine Phosphorylation ◽  
Phorbol Esters ◽  
Receptor Occupancy ◽  
Mitogen Activated Protein Kinase ◽  
Free Calcium ◽  
Mapk Activation ◽  
Kinase C ◽  
Mitogen Activated Protein

The proliferative effects of gastrin on normal and neoplastic gastro-intestinal tissues have been shown to be mediated by the gastrin/CCKB (G/CCKB) G-protein-coupled receptors. We have recently reported that gastrin stimulates the tyrosine phosphorylation of Shc proteins and their subsequent association with the Grb2/Sos complex, leading to mitogen-activated protein kinase (MAPK) activation, a pathway known to play an important role in cell proliferation. We undertook the present study to characterize the signalling pathways used by this receptor to mediate the activation of the Shc/Grb2 complex. Since G/CCKB receptor occupancy leads to the activation of the phospholipase C (PLC)/protein kinase C (PKC) pathway, we examined whether PKC stimulation and Ca2+ mobilization contribute to the phosphorylation of Shc proteins and their association with Grb2 in response to gastrin. Our results indicate that Shc proteins are tyrosine phosphorylated and associate with Grb2 in response to phorbol esters, suggesting that activation of PKC is a potential signalling pathway leading to activation of the Shc/Grb2 complex. Inhibition of PKC by GF109203X completely blocked the effect of PMA on Shc tyrosine phosphorylation and its subsequent association with Grb2, but had a partial inhibitory effect on the response to gastrin. Depletion of the intracellular Ca2+ pools by treatment with thapsigargin blocked the increase in intracellular free calcium concentration induced by gastrin and diminished the ability of the peptide to stimulate Shc phosphorylation and recruitment of Grb2. In addition, removal of extracellular Ca2+ partially inhibited the effect of gastrin on Shc phosphorylation as well as its association with Grb2, indicating that the effects of gastrin are also mediated by Ca2+-dependent mechanisms. Furthermore, we show that blockage of the two major early signals generated by activation of PLC, which induced the activation of the Shc/Grb2 complex, also blocked gastrin-induced MAPK activation.

scholarly journals A method for measuring protein kinase C activity in permeabilized T lymphocytes by using peptide substrates. Evidence for multiple pathways of kinase activation

1990 ◽  
Vol 268 (2) ◽  
pp. 303-308 ◽  
Author(s):  
D R Alexander ◽  
J D Graves ◽  
S C Lucas ◽  
D A Cantrell ◽  
M J Crumpton
Keyword(s):  
T Cells ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
T Lymphocytes ◽  
Inositol Phosphates ◽  
Assay System ◽  
Peptide Substrates ◽  
Kinase C ◽  
Wide Range ◽  
Pkc Activation

Activation of protein kinase C (PKC) in human T lymphocytes is an immediate consequence of mitogenic signalling via the antigen-receptor complex and CD2 antigen. In order to investigate further the signal-transduction pathways which result in PKC activation, we have established a novel PKC assay system using streptolysin-O-permeabilized T cells. Known peptide substrates of PKC were introduced into permeabilized cells in the presence of [gamma-32P]ATP, 3 mM-Mg2+ and 150 nM free Ca2+. The peptide found to have the lowest background phosphorylation had the sequence Pro-Leu-Ser-Arg-Thr-Leu-Ser-Val-Ala-Ala-Lys-Lys (peptide GS), and the phosphorylation of the peptide was increased up to 6-fold by direct activation of PKC with phorbol 12,13-dibutyrate. Induction of PKC activation with the UCHT1 antibody against the CD3 antigen, or with phytohaemagglutinin (PHA) or guanosine 5′-[gamma-thio]triphosphate (GTP[S]), increased peptide-GS phosphorylation by 2-3 fold. The specificity of PKC action on peptide GS was demonstrated by blocking increases in phosphorylation with a pseudosubstrate peptide PKC inhibitor. PKC activation by this technique could be detected within 1 min of adding external ligand. Dose-response curves revealed that PHA-induced production of inositol phosphates correlated closely with PKC activities, whereas only a partial correlation between these parameters was observed with GTP[S]. Our data are consistent with the presence of more than one G-protein-mediated pathway of PKC regulation in T cells. The quantitative PKC assay system described is both simple and reproducible, and its potential application to a wide range of cell types should prove useful in further investigations of PKC activation mechanisms.

Na(+)-H+ exchange is stimulated by protein kinase C activation in inner medullary collecting duct cells

1990 ◽  
Vol 259 (4) ◽  
pp. F666-F671 ◽  
Author(s):  
I. N. Slotki ◽  
J. H. Schwartz ◽  
E. A. Alexander
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cell Activation ◽  
Phorbol Esters ◽  
Collecting Duct ◽  
Synthetic Analogue ◽  
Inner Medullary Collecting Duct ◽  
Kinase C ◽  
Medullary Collecting Duct ◽  
Free Media

In this study we investigated the role of protein kinases in activation of the Na(+)-H+ exchanger in inner medullary collecting duct (IMCD) cells. Monolayers, 24-48 h after achieving confluence, were made quiescent by 24 h incubation in 0.1% serum before study. Changes in pHi were measured with 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Phorbol myristate acetate (PMA), a synthetic analogue of diacylglycerol (DAG), was used to stimulate protein kinase C (PKC). In nominally HCO3(-)-free media containing 110 mM Na+ and 1 mM Ca2+, PMA addition increased pHi from 7.29 +/- 0.08 to 7.54 +/- 0.07 after 20 min. The increment in pHi was completely inhibited by 1 mM amiloride or by replacement of extracellular Na+ with choline but not inhibited by 1 mM N-ethylmaleimide, an inhibitor of active proton transport. Downregulation of PKC by overnight incubation of monolayers with PMA also prevented the rise in pHi upon subsequent challenge with PMA. Another active analogue of DAG, 1,2-dioleoyl-rac-glycerol, caused an increment in pHi similar to that produced by PMA, whereas 4 alpha-phorbol, an inactive analogue, did not stimulate Na(+)-H+ exchange. Bradykinin (10(-6) M), a phospholipase C-activating hormone, also induces alkalinization of IMCD cells similar to that produced by phorbol esters. Neither vasopressin (10(-7) M), which induces cellular accumulation of adenosine 3-,5--cyclic monophosphate (cAMP) and activation of protein kinase A (PKA), nor 8-bromo-cAMP (1 mM) changed pHi. Therefore in the IMCD cell activation of PKC but not PKA stimulates a rise in pHi via the Na(+)-H+ exchanger.

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