scholarly journals Effect of vasopressin on the regulation of protein synthesis initiation in liver cells

1988 ◽  
Vol 254 (3) ◽  
pp. 773-779 ◽  
Author(s):  
J Menaya ◽  
R Parrilla ◽  
M S Ayuso
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Liver Cells ◽  
Initiation Factor ◽  
Protein Labelling ◽  
Kinase C ◽  
Isolated Liver Cells ◽  
Wide Range ◽  
Initiation Factor 2

Vasopressin was found to be an effective inhibitor of protein labelling in isolated liver cells. Its effect shows the following distinct characteristics: (1) in contrast with alpha-adrenergic agonists, its effect is observable under a wide range of cellular Ca2+-loading conditions; (2) it is not influenced by the nutritional state of the animal. The lack of vasopressin effect on valine production, and its ability to decrease protein labelling from near-saturation concentrations of [3H]valine, indicate that the observed variations in protein labelling reflect actual changes in the rate of protein synthesis. The action of vasopressin is primarily exerted on the initiation step of protein synthesis and this effect is accompanied by a decreased activity of eukaryotic initiation factor 2. Activators of protein kinase C showed similar but not additive effects on protein synthesis, as did vasopressin. It seems plausible to conclude that protein kinase C activation may play an important regulatory role in hepatic protein synthesis as a transducer of hormonal and perhaps other type of signals.

scholarly journals Role of Ca2+ and protein kinase C in the receptor-mediated activation of Na+/H+ exchange in isolated liver cells

1997 ◽  
Vol 325 (3) ◽  
pp. 631-636 ◽  
Author(s):  
Angeles MARTÍN-REQUERO ◽  
Francisco J. DAZA ◽  
Ofelia G. HERMIDA ◽  
Nora BUTTA ◽  
Roberto PARRILLA
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Liver Cells ◽  
Adrenergic Agonists ◽  
Vasoactive Peptides ◽  
Kinase C ◽  
Isolated Liver Cells ◽  
Isolated Liver ◽  
Intracellular Alkalinization ◽  
Vasoactive Peptide

This work aimed to study the relationship between agonist-induced changes in cytosolic free calcium levels, protein kinase C (PKC) activity and intracellular pH in isolated liver cells. We observed that, like α1-adrenergic agonists, the Ca2+-mobilizing vasoactive peptides vasopressin and angiotensin II produced an extracellular-Na+-dependent, 5-(N-ethyl-N-isopropyl)amiloride-sensitive, intracellular alkalinization, indicative of Na+/H+ antiporter activation. Blocking the agonist-induced increase in the intracellular Ca2+ concentration using the calcium chelator bis-(o-aminophenoxy)ethane-N,N,N′,N′-tetra-acetic acid (BAPTA) prevented all types of receptor-mediated intracellular alkalinization. Thus activation of the Na+/H+ exchanger by either α1-adrenergic agonists or vasoactive peptides relies on the mobilization of intracellular Ca2+. In contrast, only the α1-adrenergic-agonist-induced alkalinization was dependent on extracellular Ca2+. Even though α1-adrenergic as well as vasoactive peptide agonists stimulated protein kinase C (PKC) activity in isolated liver cells, only the α1-adrenoreceptor-mediated intracellular alkalinization was dependent on PKC. According to these observations, Ca2+-mobilizing agonists appear to activate the Na+/H+ exchanger by at least two different mechanisms: (1) the α1-adrenoreceptor-mediated activation that is dependent on extracellular Ca2+ and PKC; and (2) vasoactive-peptide-induced alkalinization that is independent of extracellular Ca2+ and PKC. The α1-adrenoreceptor-mediated, PKC-sensitive, activation of the Na+/H+ exchanger seems to be responsible for the distinct ability of these receptors to elicit the sustained stimulation of hepatic functions.

scholarly journals Protein Kinase C-Related Kinase 2 Phosphorylates the Protein Synthesis Initiation Factor eIF4E in Starfish Oocytes

2000 ◽  
Vol 228 (2) ◽  
pp. 166-180 ◽  
Author(s):  
Shyh-Jye Lee ◽  
Genevieve Stapleton ◽  
Julia H. Greene ◽  
Merrill B. Hille
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Initiation Factor ◽  
Kinase C ◽  
Protein Synthesis Initiation

scholarly journals 3,5,3′-Tri-iodo-l-thyronine acutely regulates a protein kinase C-sensitive, Ca2+-independent, branch of the hepatic α1-adrenoreceptor signalling pathway

1998 ◽  
Vol 331 (1) ◽  
pp. 89-97 ◽  
Author(s):  
Francisco J. DAZA ◽  
Roberto PARRILLA ◽  
Angeles MARTÍN-REQUERO
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Hepatic Metabolism ◽  
Liver Cells ◽  
Signalling Pathway ◽  
Perfused Liver ◽  
Kinase C ◽  
Isolated Liver Cells ◽  
Isolated Liver ◽  
Stimulation Of

This work aimed to investigate the acute effect of the thyroid hormone 3,5,3´-tri-iodo-l-thyronine (T3) in regulating the hepatic metabolism either directly or by controlling the responsiveness to Ca2+-mobilizing agonists. We did not detect any acute metabolic effect of T3 either in perfused liver or in isolated liver cells. However, T3 exerted a powerful inhibitory effect on the α1-adrenoreceptor-mediated responses. The promptness of this T3 effect rules out that it was the result of rate changes in gene(s) transcription. T3 inhibited the α1-adrenoreceptor-mediated sustained stimulation of respiration and release of Ca2+ and H+, but not the glycogenolytic or gluconeogenic responses, in perfused liver. In isolated liver cells, T3 enhanced the α1-agonist-induced increase in cytosolic free Ca2+ and impeded the intracellular alkalinization. Since T3 also prevented the α1-adrenoreceptor-mediated activation of protein kinase C, its effects on pH seem to be the result of a lack of activation of the Na+/H+ exchanger. The failure of T3 to prevent the α1-adrenergic stimulation of gluconeogenesis despite the inhibition of protein kinase C activation indicates that the elevation of cytosolic free Ca2+ is a sufficient signal to elicit that response. T3 also impaired some of the angiotensin-II-mediated responses, but did not alter the effects of PMA on hepatic metabolism, indicating, therefore, that some postreceptor event is the target for T3 actions. The differential effect of T3 in enhancing the α1-adrenoreceptor-mediated increase in cytosolic free Ca2+ and preventing the activation of protein kinase C, provides a unique tool for further investigating the role of each branch of the signalling pathway in controlling the hepatic functions. Moreover, the low effective concentrations of T3 (⩽ 10 nM) in perturbing the α1-adrenoreceptor-mediated response suggests its physiological significance.

scholarly journals Ribosomal RACK1:Protein Kinase C βII Phosphorylates Eukaryotic Initiation Factor 4G1 at S1093 To Modulate Cap-Dependent and -Independent Translation Initiation

2018 ◽  
Vol 38 (19) ◽  
Author(s):  
Mikhail I. Dobrikov ◽  
Elena Y. Dobrikova ◽  
Matthias Gromeier
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Kinase Inhibitor ◽  
Physiological Role ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Kinase C ◽  
Cox 2

ABSTRACT Eukaryotic ribosomes contain the high-affinity protein kinase C βII (PKCβII) scaffold, receptor for activated C kinase (RACK1), but its role in protein synthesis control remains unclear. We found that RACK1:PKCβII phosphorylates eukaryotic initiation factor 4G1 (eIF4G1) at S1093 and eIF3a at S1364. We showed that reversible eIF4G(S1093) phosphorylation is involved in a global protein synthesis surge upon PKC–Raf–extracellular signal-regulated kinase 1/2 (ERK1/2) activation and in induction of phorbol ester-responsive transcripts, such as cyclooxygenase 2 (Cox-2) and cyclin-dependent kinase inhibitor (p21Cip1), or in 5′ 7-methylguanosine (m7G) cap-independent enterovirus translation. Comparison of mRNA and protein levels revealed that eIF4G1 or RACK1 depletion blocked phorbol ester-induced Cox-2 or p21Cip1 expression mostly at the translational level, whereas PKCβ inhibition reduced them both at the translational and transcript levels. Our findings reveal a physiological role for ribosomal RACK1 in providing the molecular scaffold for PKCβII and its role in coordinating the translational response to PKC-Raf-ERK1/2 activation.

Dephosphorylation of activated protein kinase C contributes to downregulation by bryostatin

1996 ◽  
Vol 271 (1) ◽  
pp. C304-C311 ◽  
Author(s):  
H. W. Lee ◽  
L. Smith ◽  
G. R. Pettit ◽  
J. Bingham Smith
Keyword(s):  
Alkaline Phosphatase ◽  
Protein Synthesis ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Bryostatin 1 ◽  
Rapid Loss ◽  
Renal Epithelial Cells ◽  
Kinase C ◽  
Phosphatase Treatment ◽  
Pkc Alpha

We show that bryostatin 1 (Bryo) rapidly produces an inactive, incompetent 76-kDa form of protein kinase C-alpha (PKC-alpha) in the LLC-MK2 line of renal epithelial cells. Bryo, like phorbol 12-myristate 13-acetate (PMA), acutely activated PKC, as indicated by autophosphorylation and translocation of PKC-alpha, the predominant PMA-sensitive isoform expressed by the cells. Bryo concomitantly increased the 32P labeling of 80-kDa PKC-alpha by autophosphorylation and produced a 76-kDa form of PKC-alpha that lacked detectable 32P. The 76-kDa form was in the particulate rather than the cytosolic fraction, which suggests that it was produced from activated kinase. Alkaline phosphatase treatment of immunoprecipitated PKC-alpha converted the 80-kDa form to 76 kDa, but it had no effect on the mobility of the 76-kDa form, suggesting that it was not phosphorylated. Pulse-chase labeling of PKC-alpha with [35S]Met/Cys indicated that there is a precursor-product relationship between the 80- and 76-kDa forms, respectively. Inhibition of protein synthesis had no effect on the production of 76-kDa PKC-alpha by Bryo. PMA also produced 76-kDa PKC-alpha but was less potent and efficacious than Bryo. Bryo produced a more rapid loss of 80-kDa PKC-alpha protein and total Ca(2+)- and phospholipid-dependent PKC activity than PMA. The 76-kDa form is inactive and incompetent because it lacked detectable 32P under conditions that strongly autophosphorylated the 80-kDa form. We suggest that dephosphorylation predisposes PKC to proteolysis, and greater production of the 76-kDa form explains the more efficient downregulation of the kinase by Bryo vs. PMA.

Rapid response of protein synthesis to insulin in 3T3 cells: Effects of protein kinase C depletion and differences from the response to serum repletion

1986 ◽  
Vol 6 (9) ◽  
pp. 797-804 ◽  
Author(s):  
John E. Hesketh ◽  
Gillian P. Campbell ◽  
Peter J. Reeds
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Actinomycin D ◽  
Calf Serum ◽  
Cell Protein ◽  
Foetal Calf Serum ◽  
3T3 Cells ◽  
Kinase C

Quiescent 3T3 cells grown in media containing 4% foetal calf serum showed different responses to insulin and to serum repletion (to 12%). Insulin stimulated protein synthesis within 1 h and this early response was insensitive to actinomycin D. The later insulin response showed progressive sensitivity to actinomycin D. The serum response was slower, not occurring until 1 h, and was inhibited by actinomycin D. Depletion of cell protein kinase C by pre-treatment with phorbol ester caused a total block of the immediate response to insulin but had little effect on the response to serum or the later response to insulin. Acute phorbol ester treatment stimulated protein synthesis.

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