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

1985 ◽  
Vol 101 (1) ◽  
pp. 269-276 ◽  
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.

Phorbol esters inhibit ammoniagenesis and gluconeogenesis in proximal tubular segments

1987 ◽  
Vol 252 (6) ◽  
pp. F1073-F1079
Author(s):  
M. C. Chobanian ◽  
M. R. Hammerman
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Proximal Tubule ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Extracellular Ph ◽  
Linear Functions ◽  
Kinase C ◽  
Proximal Tubular ◽  
Stimulation Of

To characterize the regulation of ammoniagenesis and gluconeogenesis in renal proximal tubule, ammonia and glucose productions were measured in suspensions of canine proximal tubular segments incubated with 10 mM L-glutamine. Productions were linear functions of time for 120 min and were decreased as extracellular pH was increased from 7.0 to 7.5 To ascertain whether activation of protein kinase c affects either process, we incubated segments with tumor-promoting phorbol esters, 12-O-tetradecanoylphorbol-13-acetate (TPA), or phorbol 12,13-dibutyrate, or with the inactive phorbol ester 4 alpha-phorbol. Ammoniagenesis and gluconeogenesis were inhibited by incubation with 10(-6) M of the two former compounds but not the latter compound. Inhibition of ammoniagenesis and gluconeogenesis occurred after incubation with as little as 10(-9) M phorbol 12,13-dibutyrate. Phorbol ester-induced inhibition was observed under conditions such that extracellular [Na+] was greater than intracellular [Na+], but not when extracellular [Na+] equaled intracellular [Na+], and was not observed in the presence of amiloride. Our findings are consistent with a role for protein kinase c in the control of ammoniagenesis and gluconeogenesis in proximal tubule. Such control could be mediated via stimulation of Na+-H+ exchange.

Phorbol ester inhibition of chicken intestinal brush-border sodium-proton exchange

1991 ◽  
Vol 260 (6) ◽  
pp. C1264-C1272 ◽  
Author(s):  
E. B. Chang ◽  
M. W. Musch ◽  
D. Drabik-Arvans ◽  
M. C. Rao
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Brush Border ◽  
Time Course ◽  
Brush Border Membrane ◽  
Phorbol Esters ◽  
Kinase C ◽  
Na Uptake ◽  
Exchange Activity

Phorbol esters, specific activators of protein kinase C, inhibit amiloride-sensitive Na uptake from the mucosal medium in intact intestinal mucosa as well as in isolated chicken villus enterocytes. In isolated cells, maximal inhibition is observed at 60 s, and influx returns to control values within 15 min. This effect can be measured either as initial 22Na influx rates or by following changes in intracellular pH using the pH-sensitive fluorescent dye 5,6-carboxyfluorescein. The effects of amiloride and phorbol esters were not additive, suggesting inhibition of a common transport system, i.e., Na-H exchange. In brush-border membrane vesicles (BBMV) made from villus enterocytes, amiloride-sensitive Na-H exchange activity was significantly inhibited in phorbol ester-treated cells. The degree of inhibition of 22Na uptake by BBMV had the same time course and dose-effect relationship as phorbol ester-inhibited cellular Na uptake. Similarly, the time course of protein kinase C translocation from cytosol to particulate or brush-border membrane fractions correlated with Na uptake measurements made in whole cells and BBMV. These results suggest that protein kinase C activation in chicken villus enterocytes inhibits brush-border membrane Na-H exchange activity.

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.

Rat histidine decarboxylase promoter is regulated by gastrin through a protein kinase C pathway

1996 ◽  
Vol 270 (4) ◽  
pp. G619-G633 ◽  
Author(s):  
M. Hocker ◽  
Z. Zhang ◽  
D. A. Fenstermacher ◽  
S. Tagerud ◽  
M. Chulak ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Time Course ◽  
Histidine Decarboxylase ◽  
Peptide Hormone ◽  
Direct Stimulation ◽  
Gastric Glands ◽  
Kinase C ◽  
Translational Start ◽  
Stimulation Of

The enzyme L-histidine decarboxylase (HDC; EC 4.1.1.22), which converts L-histidine to histamine, plays a key role in the regulation of acid secretion. In the rat and human stomach, the peptide hormone gastrin appears to be one of the main regulators of HDC expression. In rats, marked elevation of gastric HDC mRNA abundance was observed within 12 h after induction of hypergastrinemia by a single injection of the proton-pump blocker omeprazole. In situ hybridization revealed that HDC expression occurred in the basal third of gastric glands where enterochromaffin-like cells are localized. To study the regulation of HDC gene transcription, 1,291 nucleotides of the 5'-flanking region of the rat HDC gene and the noncoding portion of exon 1 were cloned and sequenced. Gastrin and cholecystokinin (CCK) octapeptide equipotently stimulated the transcriptional activity of the rat HDC promoter three- to fourfold, and deletion analysis revealed the presence of a gastrin response element within 201 nucleotides upstream of the translational start site. Time-course studies revealed maximal activation of the HDC promoter after 12-36 h. Direct stimulation of protein kinase C (PKC) with the phorbol ester phorbol 12-myristate 13-acetate (PMA) substantially elevated rat HDC promoter activity, whereas induction of Ca2+ -dependent signaling pathways with thapsigargin was without effect. Downregulation or blockade of PKC abolished the effects of gastrin and PMA on the HDC promoter. These data indicate that stimulation of the CCK-B/gastrin receptor activates the rat HDC promoter in a time- and dose-dependent fashion and that this effect is primarily mediated via a PKC-dependent signaling pathway. Use of HDC as a model gene will allow further investigation of the intracellular pathways that are involved in gastrin-dependent gene regulation.

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.

Regulation of p-aminohippurate transport by protein kinase C in OK kidney epithelial cells

1996 ◽  
Vol 271 (2) ◽  
pp. F469-F475 ◽  
Author(s):  
M. Takano ◽  
J. Nagai ◽  
M. Yasuhara ◽  
K. Inui
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Basolateral Membrane ◽  
Significant Inhibition ◽  
Regulatory Control ◽  
Ok Cells ◽  
Kinase C ◽  
Apical Side

We studied the effect of phorbol 12-myristate 13-acetate (PMA), a phorbol ester which activates protein kinase C, on p-aminohippurate (PAH) transport in OK cells. PMA (10(-7) M) almost completely inhibited the transcellular transport of PAH across OK cell monolayers from the basal to the apical side, as well as the accumulation of PAH in the cells. The uptake of PAH across the basolateral membrane of OK cells was inhibited by PMA in a time-and dose-dependent fashion. Exposing the cells with other protein kinase C activators such as active phorbol esters and diacylglycerols also resulted in a significant inhibition of basolateral PAH uptake, but the inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate, had no effect. The inhibition of basolateral PAH uptake by PMA was blocked by staurosporine, an inhibitor of protein kinase C. Cycloheximide, actinomycin D, colchicine, and cytochalasin D did not affect the inhibitory effect of PMA on basolateral PAH uptake. These results suggested that the PAH transport system in OK cells is under the regulatory control of protein kinase C.

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

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.

scholarly journals Protein kinase C-dependent and -independent mechanisms regulating the parotid substance P receptor as revealed by differential effects of protein kinase C inhibitors

1988 ◽  
Vol 256 (2) ◽  
pp. 677-680 ◽  
Author(s):  
H Sugiya ◽  
J W Putney
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Substance P ◽  
Time Course ◽  
Phorbol Esters ◽  
Inhibitory Effect ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Substance P Receptor ◽  
Rat Parotid

Substance P-induced inositol trisphosphate (InsP3) formation was inhibited by 1 microM-4 beta-phorbol 12,13-dibutyrate (PDBu) in rat parotid acinar cells. The inhibitory effect of PDBu was reversed by the protein kinase C inhibitors H-7 or K252a. Substance P also elicits a persistent desensitization of subsequent substance P-stimulated InsP3 formation. However, this desensitization was not inhibited by H-7. In addition, H-7 had no effect on the time course of substance P-induced InsP3 formation. These results suggest that, although activation of protein kinase C by phorbol esters can inhibit the substance P receptor-linked phospholipase C pathway, this mechanism apparently plays little, if any, role in regulating this system after activation by substance P.

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