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

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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Calcium mobilization and protein kinase C activation are required for cholecystokinin stimulation of pancreatic cholesterol esterase secretion

Biochemical Journal ◽

10.1042/bj3060605 ◽

1995 ◽

Vol 306 (2) ◽

pp. 605-608 ◽

Cited By ~ 3

Author(s):

J Brodt-Eppley ◽

D Y Hui

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Digestive Enzyme ◽

Calcium Mobilization ◽

Cholesterol Esterase ◽

Ionophore A23187 ◽

Prolonged Incubation ◽

Ar42j Cells ◽

Kinase C ◽

Stimulation Of

The bile salt-stimulated cholesterol esterase is a digestive enzyme synthesized by the acinar cells of the pancreas. Previous results have shown that cholesterol esterase biosynthesis and secretion in the AR42J pancreatoma cells could be increased 3-5-fold by intestinal hormones such as cholecystokinin (CCK). The purpose of the current study is to explore the signalling mechanism by which CCK stimulation of AR42J cells results in increased biosynthesis and secretion of the cholesterol esterase. The results showed that the CCK-induced cholesterol esterase secretion could be mimicked by addition of the Ca2+ ionophore A23187 or by transient incubation of AR42J cells with the protein kinase C activator phorbol 12-myristate 13-acetate (PMA). Cholesterol esterase stimulation by CCK, A23187 and PMA could be abolished by the calcium chelator BAPTA or by specific protein kinase C inhibitors such as chelerythrine. Additionally, prolonged incubation of AR42J cells with PMA to reduce the protein kinase C level, also reduced CCK-stimulated cholesterol esterase secretion to a level similar to that observed in control cells. Taken together, these data suggested that CCK activation of cholesterol esterase secretion may be mediated by a Ca(2+)-dependent protein kinase C pathway, requiring increases in calcium mobilization and activation of protein kinase C.

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Protein Kinase C Isoform ε Negatively Regulates ADP-Induced Thromboxane Generation by Regulating cPLA2 Activation and Calcium Mobilization In Platelets

Blood ◽

10.1182/blood.v116.21.2020.2020 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2020-2020

Author(s):

Yamini Bynagari ◽

Parth Lakhani ◽

Kamala Bhavaraju ◽

Jianguo Jin ◽

Mario C Rico ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Conflicts Of Interest ◽

Arterial Injury ◽

Calcium Mobilization ◽

Erk Activation ◽

Kinase C ◽

Cpla2 Activation ◽

Pkc Isoforms

Abstract Abstract 2020 Positive regulatory role of Protein Kinase C (PKC) isoforms in platelets have been extensively studied. However, negative regulatory roles of PKCs in platelets are poorly understood. In this study we investigated the mechanism by which PKCs negatively regulate ADP-induced thromboxane generation and identified PKC isoforms involved in this process. Pan PKC inhibition with GF109203X potentiated ADP-induced cPLA2 phosphorylation suggesting that PKCs negatively regulate thromboxane generation by regulating cPLA2 activation. Inhibition of PKCs potentiated ADP-induced ERK activation and intracellular calcium mobilization, two upstream signaling molecules of cPLA2.These data suggest that PKCs negatively regulate thromboxane by regulating ERK activation and calcium mobilization, which inturn regulate cPLA2 activation. Pan-PKC inhibition potentiated ADP-induced, P2Y1 receptor-mediated calcium mobilization in platelets independent of P2Y12-receptor. Pretreatment of platelets with GF109203X, a Pan PKC inhibitor, but not Go-6976, a classical PKC isoform inhibitor, potentiated ADP-induced thromboxane generation. Thus, we investigated the role of various novel class of PKC isoforms (nPKCs) in platelets. We have previously demonstrated that nPKC η, θ, δ positively regulates agonist-induced thromboxane generation in platelets. Thus, we investigated if the role of nPKC ε in ADP-induced thromboxane generation using PKC ε knockout mice (PKCε KO). ADP-induced thromboxane generation in PKC ε KO murine platelets was ten-fold higher than that of wild type platelets. Furthermore, PKC ε KO mice exhibited shorter times to occlusion in FeCl3-induced arterial injury model and shorter bleeding times in Tail bleeding experiments. We conclude that PKCε negatively regulates ADP-induced thromboxane generation in platelets and thereby offers protection against thrombosis. Disclosures: No relevant conflicts of interest to declare.

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Role of intracellular calcium mobilization in the regulation of protein kinase C-mediated membrane processes

Nature ◽

10.1038/317549a0 ◽

1985 ◽

Vol 317 (6037) ◽

pp. 549-551 ◽

Cited By ~ 141

Author(s):

W. S. May ◽

N. Sahyoun ◽

M. Wolf ◽

P. Cuatrecasas

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Intracellular Calcium ◽

Calcium Mobilization ◽

Membrane Processes ◽

Kinase C ◽

Intracellular Calcium Mobilization

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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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