Arachidonic Acid and Cyclic Adenosine Monophosphate Stimulation of c-fosExpression bya Pathway Independent of Phorbol Ester-Sensitive Protein Kinase C

Recent studies suggest that 12-O-tetradecanoylphorbol 13-acetate (TPA), one of a family of phorbol esters that are known tumor promoters, can activate intracellular Ca2+, phospholipid-dependent protein kinase (protein kinase C) directly. To examine the possible involvement of protein kinase C-mediated mechanisms in regulating gastric somatostatin release, we studied the effects of TPA on isolated enriched canine gastric somatostatin cells in short-term culture. TPA markedly stimulated somatostatin release such that nearly 10% of total cellular content of somatostatin was released into media within 2 h of incubation. Among the phorbol compounds tested, TPA was the most potent, with half-maximum effective dose (ED50) obtained at a dose of 5 X 10(-9) M. Phorbol 12,13-dibutyrate (PDBu) also stimulated somatostatin release but with only 5% of the potency of TPA, whereas phorbol compounds with no biological activity in other systems failed to stimulate somatostatin release. In the absence of extracellular Ca2+, the effects of TPA were significantly attenuated. In contrast, stimulation of somatostatin release by forskolin (10(-4) M) was not affected by Ca2+ deprivation but was potentiated by TPA. No such potentiation was observed when TPA was combined with the Ca2+ ionophore A23187. Carbamylcholine (10(-5) M), which inhibits the stimulatory actions of beta-adrenergic agonists or dibutyryl cyclic adenosine monophosphate on somatostatin cells, also inhibited TPA-induced somatostatin release. These data suggest the presence of dual stimulatory mechanisms for gut somatostatin release, both of which are susceptible to inhibition by muscarinic agonists.

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Stimulation of porcine thyroid cell alkalinization and growth by EGF, phorbol ester, and diacylglycerol

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1990.258.3.e445 ◽

1990 ◽

Vol 258 (3) ◽

pp. E445-E450

Author(s):

N. Takasu ◽

I. Komiya ◽

Y. Nagasawa ◽

T. Asawa ◽

T. Shinoda ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Cell Growth ◽

Phorbol Ester ◽

Thyroid Cell ◽

Ph Indicator ◽

Thyroid Cells ◽

Kinase C ◽

Epidermal Growth ◽

Stimulation Of

We studied the effects of epidermal growth factor (EGF), 12-O-tetradecanoylphorbol-13-acetate (TPA), and 1-oleoyl-2-acetyl-glycerol (OAG) on cytoplasmic pH (pHi) and cell growth in cultured porcine thyroid cells. pHi was measured using 2',7'-bis(2-carboxyethyl-5,6-carboxyfluorescein (BCECF), an internalized fluorescent pH indicator. EGF, TPA, and OAG alkalinized the thyroid cells and stimulated their growth. These EGF-, TPA-, and OAG-stimulated cell alkalinization and growth depended on extracellular Na concentrations and were inhibited by amiloride, an inhibitor of Na(+)-H+ exchanger, indicating that EGF-, TPA-, and OAG-stimulated cell alkalinization and growth may occur through activation of Na(+)-H+ exchange. Alkalinization seems to be involved in thyroid cell growth. TPA (a tumor-promoting phorbol ester) and OAG (synthetic diacylglycerol), both potent activators of protein kinase C, imitate the action of EGF in rapidly elevating pHi and stimulating cell growth in thyroid cells. Trifluoperazine, an inhibitor of protein kinase C, inhibited EGF-, TPA-, and OAG-stimulated cell alkalinization and growth. The data suggest that activation of protein kinase C may be involved in the mechanism of EGF-stimulated cell alkalinization and growth of the thyroid cells.

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A novel 3',5'-cyclic adenosine monophosphate-responsive sequence in the bovine CYP17 gene is a target of negative regulation by protein kinase C

Molecular Endocrinology ◽

10.1210/me.6.8.1323 ◽

1992 ◽

Vol 6 (8) ◽

pp. 1323-1331 ◽

Cited By ~ 13

Author(s):

M. Bakke

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Cyclic Adenosine Monophosphate ◽

Adenosine Monophosphate ◽

Negative Regulation ◽

Kinase C ◽

Cyp17 Gene

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

Biochemical Journal ◽

10.1042/bj3180207 ◽

1996 ◽

Vol 318 (1) ◽

pp. 207-212 ◽

Cited By ~ 53

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.

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Osmotic and phorbol ester-induced activation of Na+/H+ exchange: possible role of protein phosphorylation in lymphocyte volume regulation.

The Journal of Cell Biology ◽

10.1083/jcb.101.1.269 ◽

1985 ◽

Vol 101 (1) ◽

pp. 269-276 ◽

Cited By ~ 88

Author(s):

S Grinstein ◽

S Cohen ◽

J D Goetz ◽

A Rothstein

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Phorbol Ester ◽

Time Course ◽

Phorbol Esters ◽

Underlying Mechanism ◽

Atp Depletion ◽

Sequence Of Events ◽

Kinase C ◽

Stimulation Of

The Na+/H+ antiport is stimulated by 12-O-tetradecanoylphorbol-13, acetate (TPA) and other phorbol esters in rat thymic lymphocytes. Mediation by protein kinase C is suggested by three findings: (a) 1-oleoyl-2-acetylglycerol also activated the antiport; (b) trifluoperazine, an inhibitor of protein kinase C, blocked the stimulation of Na+/H+ exchange; and (c) activation of countertransport was accompanied by increased phosphorylation of specific membrane proteins. The Na+/H+ antiport is also activated by osmotic cell shrinking. The time course, extent, and reversibility of the osmotically induced and phorbol ester-induced responses are similar. Moreover, the responses are not additive and they are equally susceptible to inhibition by trifluoperazine, N-ethylmaleimide, and ATP depletion. The extensive analogies between the TPA and osmotically induced effects suggested a common underlying mechanism, possibly activation of a protein kinase. It is conceivable that osmotic shrinkage initiates the following sequence of events: stimulation of protein kinase(s) followed by activation of the Na+/H+ antiport, resulting in cytoplasmic alkalinization. The Na+ taken up through the antiport, together with the HCO3- and Cl- accumulated in the cells as a result of the cytoplasmic alkalinization, would be followed by osmotically obliged water. This series of events could underlie the phenomenon of regulatory volume increase.

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On the signal transducing mechanisms involved in the synergistic interaction between interleukin-1 and bradykinin on prostaglandin biosynthesis in human gingival fibroblasts

Bioscience Reports ◽

10.1007/bf01122798 ◽

1992 ◽

Vol 12 (4) ◽

pp. 263-271 ◽

Cited By ~ 17

Author(s):

Ulf H. Lerner ◽

Gustaf Brunius ◽

Thomas Modeer

Keyword(s):

Arachidonic Acid ◽

Protein Kinase C ◽

Protein Kinase ◽

Cyclic Amp ◽

Phorbol Esters ◽

Synergistic Interaction ◽

Human Gingival Fibroblasts ◽

Gingival Fibroblasts ◽

Kinase C ◽

Stimulation Of

Recombinant human interleukin-1β (IL-1β) and bradykinin (BK) synergistically stimulate prostaglandin E2 (PGE2) formation in human gingival fibroblasts cultured for 24 h. Neither BK or IL-1β per se, nor their combinations, caused any acute stimulation of cellular cyclic AMP accumulation. BK, but not IL-1β, caused a rapid, transient rise of intracellular Ca2+ concentration ([Ca2+]i), as assessed by recordings of fura-2 fluorescence in monolayers of prelabelled gingival fibroblasts. IL-1β did not change the effect of BK on [Ca2+]i. Ionomycin and A 23187, two calcium ionophores, synergistically potentiated the stimulatory effect of IL-1β on PGE2 formation. Three different phorbol esters known to activate protein kinase C also synergistically potentiated the action of IL-1β on PGE2 formation. Exogenously added arachidonic acid significantly enhanced the basal formation of PGE2. In IL-1β treated cells, the enhancement of PGE2 formation seen after addition of arachidonic acid, was synergistically upregulated by IL-1β. These data show that i) the synergistic interaction between IL-1β and BK on PGE2 formation is not due to an effect linked to an upregulation of cyclic AMP or [Ca2+]i; ii) the signal transducing mechanism by which BK interacts with IL-1β, however, may be linked to a BK induced stimulation of [Ca2+]i and/or protein kinase C; iii) the mechanism involved in the action of IL-1β may, at least partly, be due to enhancement of the biosynthesis of prostanoids mediated by an upregulation of cyclooxygenase activity.

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