scholarly journals Modulation of maturation and ribosomal protein S6 phosphorylation in Xenopus oocytes by microinjection of oncogenic ras protein and protein kinase C.

1990 ◽  
Vol 10 (3) ◽  
pp. 880-886 ◽  
Author(s):  
T Kamata ◽  
H F Kung
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Ribosomal Protein ◽  
Xenopus Oocytes ◽  
Protein A ◽  
Ras Proteins ◽  
Ras Protein ◽  
Oncogenic Ras ◽  
Ribosomal Protein S6 ◽  
Kinase C

Using Xenopus oocytes as a model system, we investigated the possible involvement of ras proteins in the pathway leading to phosphorylation of ribosomal protein S6. Our results indicate that microinjection of oncogenic T24 H-ras protein (which contains valine at position 12) markedly stimulated S6 phosphorylation on serine residues in oocytes, whereas normal ras protein (which contains glycine at position 12) was without effect. The S6 phosphorylation activity in the cell extract from T24 ras protein-injected oocytes was increased significantly. In addition, injection of protein kinase C potentiated the induction of maturation and S6 phosphorylation by the oncogenic ras protein. A similar potentiation was detected when T24 ras protein-injected oocytes were incubated with active phorbol ester. These findings suggest that ras proteins activate the pathway linked to S6 phosphorylation and that protein kinase C has a synergistic effect on the ras-mediated pathway.

Modulation of maturation and ribosomal protein S6 phosphorylation in Xenopus oocytes by microinjection of oncogenic ras protein and protein kinase C

1990 ◽  
Vol 10 (3) ◽  
pp. 880-886
Author(s):  
T Kamata ◽  
H F Kung
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Ribosomal Protein ◽  
Xenopus Oocytes ◽  
Protein A ◽  
Ras Proteins ◽  
Ras Protein ◽  
Oncogenic Ras ◽  
Ribosomal Protein S6 ◽  
Kinase C

Using Xenopus oocytes as a model system, we investigated the possible involvement of ras proteins in the pathway leading to phosphorylation of ribosomal protein S6. Our results indicate that microinjection of oncogenic T24 H-ras protein (which contains valine at position 12) markedly stimulated S6 phosphorylation on serine residues in oocytes, whereas normal ras protein (which contains glycine at position 12) was without effect. The S6 phosphorylation activity in the cell extract from T24 ras protein-injected oocytes was increased significantly. In addition, injection of protein kinase C potentiated the induction of maturation and S6 phosphorylation by the oncogenic ras protein. A similar potentiation was detected when T24 ras protein-injected oocytes were incubated with active phorbol ester. These findings suggest that ras proteins activate the pathway linked to S6 phosphorylation and that protein kinase C has a synergistic effect on the ras-mediated pathway.

The phosphorylation of eukaryotic ribosomal protein S6 by protein kinase C

1985 ◽  
Vol 148 (3) ◽  
pp. 579-586 ◽  
Author(s):  
Peter J. PARKER ◽  
Matilda KATAN ◽  
Michael D. WATERFIELD ◽  
David P. LEADER
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Ribosomal Protein ◽  
Ribosomal Protein S6 ◽  
Kinase C

scholarly journals Ca2+-independent protein kinase C activity is required for alpha1-adrenergic-receptor-mediated regulation of ribosomal protein S6 kinases in adult cardiomyocytes

2003 ◽  
Vol 373 (2) ◽  
pp. 603-611 ◽  
Author(s):  
Lijun WANG ◽  
Mark ROLFE ◽  
Christopher G. PROUD
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Ribosomal Protein ◽  
Adrenergic Receptor ◽  
Rat Cardiomyocytes ◽  
Ribosomal Protein S6 ◽  
Kinase C ◽  
Adult Cardiomyocytes ◽  
Pkc Isoforms

The α1-adrenergic agonist, phenylephrine (PE), exerts hypertrophic effects in the myocardium and activates protein synthesis. Both Ca2+-dependent protein kinase C (PKC, PKCα) and Ca2+-independent PKC isoforms (PKCδ and ε) are detectably expressed in adult rat cardiomyocytes. Stimulation of the α1-adrenergic receptor by PE results in activation of Ca2+-independent PKCs, as demonstrated by translocation of the δ and ε isoenzymes from cytosol to membrane fractions. PE also induces activation of p70 ribosomal protein S6 kinases (S6K1 and 2) in adult cardiomyocytes. We have studied the role of Ca2+-independent PKCs in the regulation of S6K activity by PE. Activation of S6K1/2 by PE was blocked by the broad-spectrum PKC inhibitor bisindolylmaleimide (BIM) I, whereas Gö6976, a compound that only inhibits Ca2+-dependent PKCs, did not inhibit S6K activation. Rottlerin, which selectively inhibits PKCδ, also prevented PE-induced S6K activation. The isoform-specific PKC inhibitors had similar effects on the phosphorylation of eukaryotic initiation factor 4E (eIF4E)-binding protein 1, a translation repressor that, like the S6Ks, lies downstream of the mammalian target of rapamycin (mTOR). Infection of cells with adenoviruses encoding dominant-negative PKCδ or ε inhibited the activation of extracellular-signal-regulated kinase (ERK) by PE, and also inhibited the activation and/or phosphorylation of S6Ks 1 and 2. The PE-induced activation of protein synthesis was abolished by BIM I and markedly attenuated by rottlerin. Our data thus suggest that Ca2+-independent PKC isoforms play an important role in coupling the α1-adrenergic receptor to mTOR signalling and protein synthesis in adult cardiomyocytes.

scholarly journals Scrape-loaded p21ras down-regulates agonist-stimulated inositol phosphate production by a mechanism involving protein kinase C

1989 ◽  
Vol 260 (1) ◽  
pp. 157-161 ◽  
Author(s):  
B D Price ◽  
J D H Morris ◽  
C J Marshall ◽  
A Hall
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Inositol Phosphate ◽  
Platelet Derived Growth Factor ◽  
3T3 Cells ◽  
Ras Protein ◽  
Kinase C ◽  
Inositol Phosphate Production ◽  
Ligand Stimulation ◽  
Scrape Loading

The effect of scrape-loaded [Val-12]p21ras on agonist-stimulated phosphatidylinositol 4,5-bisphosphate (PIP2) turnover in Swiss-3T3 cells was studied. Previously [Morris, Price, Lloyd, Marshall & Hall (1989) Oncogene 4, 27-31] we demonstrated that [Val-12]p21ras activates protein kinase C within 10 min of scrape loading. Here, we show that [Val-12]p21ras inhibits bombesin and platelet-derived growth factor-stimulated PIP2 breakdown 1.5-4 h after scrape loading. This effect persisted for at least 18 h and could be mimicked in control cells by activation of protein kinase C with 12-O-tetradecanoyl 13-acetate (TPA) 15 min prior to ligand stimulation. When protein kinase C was down-regulated by chronic TPA treatment, [Val-12]p21ras was no longer able to inhibit agonist-stimulated inositol phosphate production. These results indicate that changes in inositol phosphate levels caused by ras protein are probably due to activation of protein kinase C and not to an interaction of ras with phospholipase C.

Protein kinase C and progesterone-induced maturation in Xenopus oocytes

Development ◽  
1990 ◽  
Vol 109 (3) ◽  
pp. 597-604
Author(s):  
R.L. Varnold ◽  
L.D. Smith
Keyword(s):  
Cell Cycle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Xenopus Oocytes ◽  
Plasma Membranes ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Concomitant Reduction ◽  
Dependent Protein

Though progesterone-induced maturation has been studied extensively in Xenopus oocytes, the mechanism whereby the prophase block arrest is released is not well understood. The current hypothesis suggests that a reduction in cAMP and subsequent inactivation of cAMP-dependent protein kinase is responsible for reentry into the cell cycle. However, several lines of evidence indicate that maturation can be induced without a concomitant reduction in cAMP. We show that the mass of diacylglycerol in whole oocytes and plasma membranes decreases 29% and 10% respectively, within the first 15 sec after the addition of progesterone. Diacylglycerol in plasma membranes further decreased 59% by 5 min. We also show that the protein kinase C inhibitors sphingosine and staurosporine can induce oocyte maturation. In addition, the synthetic diglyceride, DiC8, and microinjected PKC can inhibit or delay progesterone-induced maturation. These results together suggest that a transient decrease in protein kinase C activity may regulate entry into the cell cycle. The mechanism whereby DAG is decreased in response to progesterone is unclear. Initial studies show that progesterone leads to a decrease in IP3 suggesting that progesterone may act by reducing the hydrolysis of PIP2. On the other hand, progesterone caused a decrease in the amount of [3H]arachidonate labelling in DAG during the same time suggesting that progesterone may stimulate lipase activity. The relationship between postulated changes in the PKC pathway and those hypothesized for the PKA pathway are discussed.

scholarly journals Localization of the MARCKS (87 kDa) protein, a major specific substrate for protein kinase C, in rat brain

1990 ◽  
Vol 10 (5) ◽  
pp. 1683-1698 ◽  
Author(s):  
CC Ouimet ◽  
JK Wang ◽  
SI Walaas ◽  
KA Albert ◽  
P Greengard
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Rat Brain ◽  
Protein A ◽  
Specific Substrate ◽  
Kinase C
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