Relationship of bile salt stimulation of colonic epithelial phospholipid turnover and proliferative activity: Role of activation of protein kinase C

The effect of elevating cytoplasmic Ca2+ [( Ca2+]i) on the intracellular pH (pHi) of thymic lymphocytes was investigated. In Na+-containing media, treatment of the cells with ionomycin, a divalent cation ionophore, induced a moderate cytoplasmic alkalinization. In the presence of amiloride or in Na+-free media, an acidification was observed. This acidification is at least partly due to H+ (equivalent) uptake in response to membrane hyperpolarization since: it was enhanced by pretreatment with conductive protonophores, it could be mimicked by valinomycin, and it was decreased by depolarization with K+ or gramicidin. In addition, activation of metabolic H+ production also contributes to the acidification. The alkalinization is due to Na+/H+ exchange inasmuch as it is Na+ dependent, amiloride sensitive, and accompanied by H+ efflux and net Na+ gain. A shift in the pHi dependence underlies the activation of the antiport. The effect of [Ca2+]i on Na+/H+ exchange was not associated with redistribution of protein kinase C and was also observed in cells previously depleted of this enzyme. Treatment with ionomycin induced significant cell shrinking. Prevention of shrinking largely eliminated the activation of the antiport. Moreover, a comparable shrinking produced by hypertonic media also activated the antiport. It is concluded that stimulation of Na+/H+ exchange by elevation of [Ca2+]i is due, at least in part, to cell shrinking and does not require stimulation of protein kinase C.

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Role of protein kinase C in T-cell antigen receptor regulation of p21ras: evidence that two p21ras regulatory pathways coexist in T cells

Molecular and Cellular Biology ◽

10.1128/mcb.12.7.3305-3312.1992 ◽

1992 ◽

Vol 12 (7) ◽

pp. 3305-3312

Author(s):

M Izquierdo ◽

J Downward ◽

J D Graves ◽

D A Cantrell

Keyword(s):

T Cells ◽

Protein Kinase C ◽

Protein Kinase ◽

Kinase Inhibitor ◽

Antigen Receptor ◽

Permeabilized Cell ◽

Regulatory Pathways ◽

Kinase C ◽

Stimulation Of

T-lymphocyte activation via the antigen receptor complex (TCR) results in accumulation of p21ras in the active GTP-bound state. Stimulation of protein kinase C (PKC) can also activate p21ras, and it has been proposed that the TCR effect on p21ras occurs as a consequence of TCR regulation of PKC. To test the role of PKC in TCR regulation of p21ras, a permeabilized cell system was used to examine TCR regulation of p21ras under conditions in which TCR activation of PKC was blocked, first by using a PKC pseudosubstrate peptide inhibitor and second by using ionic conditions that prevent phosphatidyl inositol hydrolysis and hence diacylglycerol production and PKC stimulation. The data show that TCR-induced p21ras activation is not mediated exclusively by PKC. Thus, in the absence of PKC stimulation, the TCR was still able to induce accumulation of p21ras-GTP complexes, and this stimulation correlated with an inactivation of p21ras GTPase-activating proteins. The protein tyrosine kinase inhibitor herbimycin could prevent the non-PKC-mediated, TCR-induced stimulation of p21ras. These data indicate that two mechanisms for p21ras regulation coexist in T cells: one PKC mediated and one not. The TCR can apparently couple to p21ras via a non-PKC-controlled route that may involve tyrosine kinases.

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Prolactin stimulation of ornithine decarboxylase and mitogenesis in Nb2 node lymphoma cells: The role of protein kinase C and calcium mobilization

Immunopharmacology ◽

10.1016/0162-3109(86)90050-0 ◽

1986 ◽

Vol 12 (1) ◽

pp. 37-51 ◽

Cited By ~ 50

Author(s):

Arthur R. Buckley ◽

David W. Montgomery ◽

Ruthann Kibler ◽

Charles W. Putnam ◽

Charles F. Zukoski ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Ornithine Decarboxylase ◽

Calcium Mobilization ◽

Lymphoma Cells ◽

Kinase C ◽

Stimulation Of

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PROTEIN KINASE C CONTROLS CA2+ MOBILIZATION IN HUMAN PLATELETS

10.1055/s-0038-1644509 ◽

1987 ◽

Cited By ~ 1

Author(s):

W Siffert ◽

P Scheid ◽

JW N Akkerman

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Human Platelets ◽

Cytosolic Ph ◽

Fluorescent Indicators ◽

Kinase C ◽

Deutsche Forschungsgemeinschaft ◽

Ionophore Monensin ◽

Stimulation Of

Platelet stimulation has been shown to result in a rise of cytosolic pH (pHi) as a result of an activation of a Na+/H+ antiport. We have investigated the role of pH in Ca2+ mobilization in human platelets. pHi and free Ca2+, {Ca2+)i, were measured in platelets loaded with the fluorescent indicators BCECF and quin2, respectively. Stimulation of platelets by either thrombin or OAG, an activator of protein kinase C (Pk-C), increased pHi. Pretreatment of platelets with inhibitors of Pk-C, trifluoperazine (TFP) or sphingosine (SPH), blocked the stimulus-induced rise in pHi, suggesting a role of Pk-C in the activation of Na+/H+ exchange. Blocking Na+/H+ exchange by an amiloride analogue or by TFP similarly suppressed the thrombin-induced increase in {Ca2*}i. This effect could be prevented by increasing pHi with the Na+/H+ ionophore monensin or with NH4Cl. The thrombin-induced (0.05 U/ml) rise in {Ca2+}i was more than 3-fold enhanced when the pH was raised from 6.8 to 7.4.Our results demonstrate that pHi controls Ca2+ mobilization in human platelets and suggest that Pk-C contributes to this control by activating the Na+/H+ exchanger.Supported by the Deutsche Forschungsgemeinschaft. No Sche 46/5-2.

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