Phosphorylation of Elongation Factor 1 (EF-1) by Protein Kinase C Stimulates GDP/GTP-Exchange Activity

1995 ◽  
Vol 234 (2) ◽  
pp. 550-556 ◽  
Author(s):  
Holme I. Peters ◽  
Yu-Wen Edith Chang ◽  
Jolinda A. Traugh
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Elongation Factor ◽  
Kinase C ◽  
Elongation Factor 1 ◽  
Exchange Activity

scholarly journals Acceleration of Sodium-Calcium Exchange Activity during ATP-induced Calcium Release in Transfected Chinese Hamster Ovary Cells

1997 ◽  
Vol 109 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Melissa Vázquez ◽  
Yu Fang ◽  
John P. Reeves
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Chinese Hamster Ovary ◽  
Calcium Release ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Ovary Cells ◽  
Kinase C ◽  
Stimulation Of ◽  
Exchange Activity

The P2U purinergic agonist ATP (0.3 mM) elicited an increase in [Ca2+]i due to Ca2+ release from intracellular stores in transfected Chinese hamster ovary cells that express the bovine cardiac Na+/Ca2+ exchanger (CK1.4 cells). The following observations indicate that ATP-evoked Ca2+ release was accompanied by a Ca2+- dependent regulatory activation of Na+/Ca2+ exchange activity: Addition of extracellular Ca2+ (0.7 mM) 0–1 min after ATP evoked a dramatic rise in [Ca2+]i in Na+-free media (Li+ substitution) compared to Na+-containing media; no differences between Na+- and Li+-based media were observed with vector-transfected cells. In the presence of physiological concentrations of extracellular Na+ and Ca2+, the ATP-evoked rise in [Ca2+]i declined more rapidly in CK1.4 cells compared to control cells, but then attained a long-lived plateau of elevated [Ca2+]i which eventually came to exceed the declining [Ca2+]i values in control cells. ATP elicited a transient acceleration of exchange-mediated Ba2+ influx, consistent with regulatory activation of the Na+/Ca2+ exchanger. The acceleration of Ba2+ influx was not observed in vector-transfected control cells, or in CK1.4 cells in the absence of intracellular Na+ or when the Ca2+ content of the intracellular stores had been reduced by prior treatment with ionomycin. The protein kinase C activator phorbol 12-myristate 13-acetate attenuated the exchange-mediated rise in [Ca2+]i under Na+-free conditions, but did not inhibit the ATP-evoked stimulation of Ba2+ influx. The effects of PMA are therefore not due to inhibition of exchange activity, but probably reflect the influence of protein kinase C on other Ca2+ homeostatic mechanisms. We conclude that exchange activity is accelerated during ATP-evoked Ca2+ release from intracellular stores through regulatory activation by increased [Ca2+]i. In the absence of extracellular Ca2+, the stimulation of exchange activity is short-lived and follows the time course of the [Ca2+]i transient; in the presence of extracellular Ca2+, we suggest that the exchanger remains activated for a longer period of time, thereby stabilizing and prolonging the plateau phase of store-dependent Ca2+ entry.

scholarly journals Oxytocin-Induced Activation of Eukaryotic Elongation Factor 2 in Myometrial Cells Is Mediated by Protein Kinase C

Endocrinology ◽  
2007 ◽  
Vol 149 (1) ◽  
pp. 131-138 ◽  
Author(s):  
Dominic Devost ◽  
Marie-Eve Carrier ◽  
Hans H. Zingg
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Wide Spectrum ◽  
Elongation Factor ◽  
Direct Stimulation ◽  
Trophic Effect ◽  
Kinase C ◽  
Elongation Factor 2 ◽  
Eukaryotic Elongation Factor 2 ◽  
Eukaryotic Elongation Factor

The nonapeptide oxytocin (OT) mediates a wide spectrum of biological action, many of them related to reproduction. Recently, we have shown that OT exerts a trophic effect on uterine smooth muscle cells and induces dephosphorylation, and thus activation, of the translation elongation factor eukaryotic elongation factor 2 (eEF2). The present study was designed to elucidate the mechanisms underlying this novel action of OT in the well-characterized human myometrial cell line hTERT-C3. Pathways known to induce eEF2 dephosphorylation are mammalian target of rapamycin (mTOR), and the MAPKs ERK1/2 and p38. Using a panel of chemical inhibitors of specific signaling pathways, we determined that none of these pathways played a role in OT-mediated eEF2 dephosphorylation. Because the OT receptor is a G protein-coupled receptor linked to Gαq, we tested the possibility that this OT action was mediated via protein kinase C (PKC). PKC activity was blocked by application of the general PKC chemical inhibitor Go6983 or by incubation with the cell-permeable PKC inhibitor peptide myr-psi PKC. With either approach, the effect of OT on eEF2 dephosphorylation was suppressed, indicating that the PKC pathway is essential for this OT action. Consistent with this idea, we also found that direct stimulation of PKC with the phorbol ester phorbol 12-myristate 13-acetate induced eEF2 dephosphorylation. Moreover, we observed that the stimulatory effect of OT on [35S]methionine incorporation into nascent proteins was blocked by PKC inhibition. Overall, these results define a novel hormonal signaling pathway that leads to eEF2 dephosphorylation and activation of protein synthesis.

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.

scholarly journals Endogenous flow-induced superoxide stimulates Na/H exchange activity via PKC in thick ascending limbs

2014 ◽  
Vol 307 (7) ◽  
pp. F800-F805 ◽  
Author(s):  
Nancy J. Hong ◽  
Jeffrey L. Garvin
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Xanthine Oxidase ◽  
Signaling Pathway ◽  
Intracellular Ph ◽  
Specific Inhibitor ◽  
Pkc Inhibitor ◽  
Kinase C ◽  
Luminal Flow ◽  
Exchange Activity

Luminal flow stimulates Na reabsorption along the nephron and activates protein kinase C (PKC) which enhances endogenous superoxide (O2−) production by thick ascending limbs (TALs). Exogenously-added O2− augments TAL Na reabsorption, a process also dependent on PKC. Luminal Na/H exchange (NHE) mediates NaHCO3 reabsorption. However, whether flow-stimulated, endogenously-produced O2− enhances luminal NHE activity and the signaling pathway involved are unclear. We hypothesized that flow-induced production of endogenous O2− stimulates luminal NHE activity via PKC in TALs. Intracellular pH recovery was measured as an indicator of NHE activity in isolated, perfused rat TALs. Increasing luminal flow from 5 to 20 nl/min enhanced total NHE activity from 0.104 ± 0.031 to 0.167 ± 0.036 pH U/min, 81%. The O2− scavenger tempol decreased total NHE activity by 0.066 ± 0.011 pH U/min at 20 nl/min but had no significant effect at 5 nl/min. With the NHE inhibitor EIPA in the bath to block basolateral NHE, tempol reduced flow-enhanced luminal NHE activity by 0.029 ± 0.010 pH U/min, 30%. When experiments were repeated with staurosporine, a nonselective PKC inhibitor, tempol had no effect. Because PKC could mediate both induction of O2− by flow and the effect of O2− on luminal NHE activity, we used hypoxanthine/xanthine oxidase to elevate O2−. Hypoxanthine/xanthine oxidase increased luminal NHE activity by 0.099 ± 0.020 pH U/min, 137%. Staurosporine and the PKCα/β1-specific inhibitor Gö6976 blunted this effect. We conclude that flow-induced O2− stimulates luminal NHE activity in TALs via PKCα/β1. This accounts for part of flow-stimulated bicarbonate reabsorption by TALs.

Loss of bradykinin receptors and TPA-stimulated Na+ influx in SV40-transformed WI-38 cells

1990 ◽  
Vol 259 (4) ◽  
pp. C549-C556 ◽  
Author(s):  
B. G. Etscheid ◽  
G. A. Jamieson ◽  
K. Toscas ◽  
M. L. Villereal
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Dramatic Reduction ◽  
Bradykinin Receptors ◽  
Sv40 Virus ◽  
Mitogenic Stimulation ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Stimulation Of ◽  
Exchange Activity

Mitogenic stimulation of Na(+)-H+ exchange activity, as defined by the level of 5-(N,N-hexamethylene)amiloride (HMA)-sensitive Na+ influx, was compared in WI-38 and SV40 virus-transformed WI-38 fibroblasts. Serum or bradykinin dramatically stimulated HMA-sensitive Na+ influx in WI-38 cells, whereas in SV40-transformed WI-38 cells, serum, but not bradykinin, produced a large increase in HMA-sensitive Na+ influx. This lack of a bradykinin response was traced to a dramatic reduction in the number of bradykinin receptors, from 470 fmol/mg protein in WI-38 cells to 29 fmol/mg protein in the SV40-transformed WI-38 cells. Transformation of WI-38 cells with SV40 virus also altered the mechanism by which HMA-sensitive Na+ influx is stimulated. In WI-38 cells, 12-O-tetradecanoylphorbol 13-acetate (TPA) dramatically stimulated HMA-sensitive Na+ influx. In SV40-transformed WI-38 cells, TPA alone had no effect on HMA-sensitive influx and inhibited serum-stimulated HMA-sensitive Na+ influx. Down-regulation of protein kinase C activity decreased serum- and TPA-stimulated HMA-sensitive Na+ influx in the WI-38 cells and relieved the TPA inhibition of serum-stimulated HMA-sensitive Na+ influx in the SV40-transformed WI-38 cells.

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