scholarly journals Key role of l-alanine in the control of hepatic protein synthesis

1987 ◽  
Vol 241 (2) ◽  
pp. 491-498 ◽  
Author(s):  
D Pérez-Sala ◽  
R Parrilla ◽  
M S Ayuso
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Physiological Role ◽  
Chain Elongation ◽  
Liver Protein ◽  
Isolated Liver Cells ◽  
Metabolic Transformation ◽  
Hepatic Protein Synthesis

We investigated the effects of administration of single amino acids to starved rats on the regulation of protein synthesis in the liver. Of all the amino acids tested, only alanine, ornithine and proline promoted statistically significant increases in the extent of hepatic polyribosome aggregation. The most effective of these was alanine, whose effect of promoting polyribosomal aggregation was accompanied by a decrease in the polypeptide-chain elongation time. The following observations indicate that alanine plays an important physiological role in the regulation of hepatic protein synthesis. Alanine was the amino acid showing the largest decrease in hepatic content in the transition from high (fed) to low (starved) rates of protein synthesis. The administration of glucose or pyruvate is also effective in increasing liver protein synthesis in starved rats, and their effects were accompanied by an increased hepatic alanine content. An increase in hepatic ornithine content does not lead to an increased protein synthesis, unless it is accompanied by an increase of alanine. The effect of alanine is observed either in vivo, in rats pretreated with cycloserine to prevent its transamination, or in isolated liver cells under conditions in which its metabolic transformation is fully impeded.

Regulation of hepatic protein synthesis in chronic inflammation and sepsis

1992 ◽  
Vol 262 (2) ◽  
pp. C445-C452 ◽  
Author(s):  
T. C. Vary ◽  
S. R. Kimball
Keyword(s):  
Protein Synthesis ◽  
Sterile Inflammation ◽  
Chain Elongation ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Translational Efficiency ◽  
Liver Protein ◽  
Ribosomal Subunits ◽  
Hepatic Protein Synthesis

The regulation of protein synthesis was determined in livers from control, sterile inflammatory, and septic animals. Total liver protein was increased in both sterile inflammation and sepsis. The rate of protein synthesis in vivo was measured by the incorporation of [3H]phenylalanine into liver proteins in a chronic (5 day) intra-abdominal abscess model. Both sterile inflammation and sepsis increased total hepatic protein synthesis approximately twofold. Perfused liver studies demonstrated that the increased protein synthesis rate in vivo resulted from a stimulation in the synthesis of both secreted and nonsecreted proteins. The total hepatic RNA content was increased 40% only in sterile inflammation, whereas the translational efficiency was increased twofold only in sepsis. The increase in translational efficiency was accompanied by decreases in the amount of free 40S and 60S ribosomal subunits in sepsis. Rates of peptide-chain elongation in vivo were increased 40% in both sterile inflammation and sepsis. These results demonstrate that sepsis induces changes in the regulation of hepatic protein synthesis that are independent of the general inflammatory response. In sterile inflammation, the increase in protein synthesis occurs by a combination of increased capacity and translational efficiency, while in sepsis, the mechanism responsible for accelerated protein synthesis is an increased translational efficiency.

scholarly journals BIOSYNTHESIS IN ISOLATED ACETABULARIA CHLOROPLASTS

1972 ◽  
Vol 54 (2) ◽  
pp. 279-294 ◽  
Author(s):  
David C. Shephard ◽  
Wendy B. Levin
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Technical Problems ◽  
Hydrolyzed Protein ◽  
Protein Amino Acids ◽  
Amino Acid Labeling ◽  
Labeling Pattern

The ability of chloroplasts isolated from Acetabulana mediterranea to synthesize the protein amino acids has been investigated. When this chloroplast isolate was presented with 14CO2 for periods of 6–8 hr, tracer was found in essentially all amino acid species of their hydrolyzed protein Phenylalanine labeling was not detected, probably due to technical problems, and hydroxyproline labeling was not tested for The incorporation of 14CO2 into the amino acids is driven by light and, as indicated by the amount of radioactivity lost during ninhydrin decarboxylation on the chromatograms, the amino acids appear to be uniformly labeled. The amino acid labeling pattern of the isolate is similar to that found in plastids labeled with 14CO2 in vivo. The chloroplast isolate did not utilize detectable amounts of externally supplied amino acids in light or, with added adenosine triphosphate (ATP), in darkness. It is concluded that these chloroplasts are a tight cytoplasmic compartment that is independent in supplying the amino acids used for its own protein synthesis. These results are discussed in terms of the role of contaminants in the observed synthesis, the "normalcy" of Acetabularia chloroplasts, the synthetic pathways for amino acids in plastids, and the implications of these observations for cell compartmentation and chloroplast autonomy.

scholarly journals Effects of the hepatotoxic agents retrorsine and aflatoxin B1 on hepatic protein synthesis in the rat

1968 ◽  
Vol 109 (1) ◽  
pp. 87-91 ◽  
Author(s):  
S. Villa-Treviño ◽  
D. D. Leaver
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Rat Liver ◽  
Aflatoxin B1 ◽  
Plasma Proteins ◽  
Pyrrolizidine Alkaloid ◽  
Main Site ◽  
Nuclear Rna ◽  
Hepatic Protein Synthesis

1. Aflatoxin and the pyrrolizidine alkaloid retrorsine inhibited the incorporation of labelled amino acids into rat liver and plasma proteins in vivo. Inhibition was greater and detected earlier with retrorsine (1hr.) than with aflatoxin (3hr.). 2. Both toxins affected the liver ribosomal aggregates, causing increases in the proportion of monomers plus dimers. The effect of retrorsine was greater than that of aflatoxin. 3. Incorporation of labelled amino acids into proteins of cell-free preparations of liver from rats treated with aflatoxin was lower than in control preparations. The main site of inhibition appeared to be the ribosomes. 4. Both toxins inhibited the incorporation of orotate into liver nuclear RNA 1hr. after administration.

scholarly journals Polyribosomes in isolated liver cells. Preparative procedures, effects of incubation and correlation with protein synthesis

1980 ◽  
Vol 186 (1) ◽  
pp. 35-45 ◽  
Author(s):  
A J Dickson ◽  
C I Pogson
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Isolated Hepatocytes ◽  
Liver Cells ◽  
Liver Protein ◽  
Isolated Cells ◽  
Isolated Liver Cells ◽  
Rat Liver Cells ◽  
Isolated Liver

Methods have been derived which permit the isolation of undergraded polyribosomes from isolated rat liver cells. Under the conditions used the polyribosome profile of hepatocytes immediately after isolation was essentially identical with that from intact liver. However, during incubation of cells in complex physiological media there was a progressive dissociation of polyribosomes. The addition of a variety of factors that produce reaggregation of polyribosomes in rat liver in vivo did not prevent dissociation during cell incubations. Although large polyribosomes were lost most rapidly, the albumin-synthesizing capacity of isolated cells was not selectively lost when compared with total protein synthesis. The significance of these results for the use of isolated hepatocytes in the study of liver protein synthesis is discussed.

Role of the state of reduction of the nad system on the regulation of hepatic protein synthesis in the rat in vivo

1982 ◽  
Vol 14 (7) ◽  
pp. 615-620 ◽  
Author(s):  
Sebastian Cerdan Garcia-Esteller ◽  
SofÍa Sanchez Robles ◽  
Angeles Martin-Requero ◽  
Matilde S. Ayuso-Parrilla ◽  
Roberto Parrilla
Keyword(s):  
Protein Synthesis ◽  
The State ◽  
Role Of The State ◽  
Hepatic Protein Synthesis

scholarly journals Protein synthesis regulation by leucine

2010 ◽  
Vol 46 (1) ◽  
pp. 29-36 ◽  
Author(s):  
Daiana Vianna ◽  
Gabriela Fullin Resende Teodoro ◽  
Francisco Leonardo Torres-Leal ◽  
Julio Tirapegui
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mrna Translation ◽  
Protein Translation ◽  
Cellular Effects ◽  
Cellular Processes ◽  
High Protein Diets

In vivo and in vitro studies have demonstrated that high protein diets affect both protein synthesis and regulation of several cellular processes. The role of amino acids as substrate for protein synthesis has been established in the literature. However, the mechanism by which these amino acids modulate transcription and regulate the mRNA translation via mTOR-dependent signaling pathway has yet to be fully determined. It has been verified that mTOR is a protein responsible for activating a cascade of biochemical intracellular events which result in the activation of the protein translation process. Of the aminoacids, leucine is the most effective in stimulating protein synthesis and reducing proteolysis. Therefore, it promotes a positive nitrogen balance, possibly by favoring the activation of this protein. This amino acid also directly and indirectly stimulates the synthesis and secretion of insulin, enhancing its anabolic cellular effects. Therefore, this review aimed to identify the role of leucine in protein synthesis modulation and to discuss the metabolic aspects related to this aminoacid.

Certain aspects of cholesterol metabolism and hepatic protein synthesis in the rat

1964 ◽  
Vol 207 (6) ◽  
pp. 1287-1294 ◽  
Author(s):  
Shiro Saito ◽  
Louis Charles Fillios
Keyword(s):  
Protein Synthesis ◽  
Cholesterol Metabolism ◽  
Dietary Treatment ◽  
High Serum ◽  
Liver Protein ◽  
High Serum Cholesterol ◽  
Cholesterol Levels ◽  
Hepatic Protein Synthesis

Hepatic protein synthesis was studied in rats fed a hypercholesteremic diet, containing cholesterol and cholic acid, and high in fat. If such a diet was fed for periods of at least 4 weeks a lowered capacity of amino acid incorporation into liver protein in vivo and in vitro was observed. The animals selected were rats which had been previously characterized by such a dietary assay as being neither refractory nor susceptible to induction of high serum cholesterol levels. When "hypo-responders" (i.e., rats which are relatively refractory to hypercholesteremia) were compared to "hyper-responders" significant differences in protein synthesis in vivo were observed after only 2 weeks of dietary treatment; the capacity for incorporation of amino acids in the livers of hyper-responders was significantly lower than that in the hypo-responders. Several studies were also carried out in vitro including an attempt to determine which intracellular components of the liver may be affected; it appears that the defect(s) is primarily related to the endoplasmic reticulum. Thus, diet may act as the modus operandi for revealing any purported inherent defect(s).

Effect of nitrogen and calorie restriction on protein synthesis in the rat

1976 ◽  
Vol 230 (5) ◽  
pp. 1321-1325 ◽  
Author(s):  
TP Stein ◽  
JC Oram-Smith ◽  
MJ Leskiw ◽  
HW Wallace ◽  
LC Long ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Liver Protein ◽  
Protein Catabolism ◽  
Intravenous Hyperalimentation ◽  
Major Response ◽  
Dietary Deficiency

The effect of a deficiency of calories and/or nitrogen on protein metabolism in the rat was investigated. During the 5 days of the study, the rats received all nutrients except water via intravenous hyperalimentation. Four diets were used: I) 1.25 g amino acids, 12.5 g glucose/day; II) 1.25 g amino acids/day; III) 1.25 g glucose/day; and IV) 12.5 glucose/day. The rate of protein synthesis in heart, lung, muscle, kidney, and liver was estimated by a modification of the technique of Garlick et al. (The diurnal response of muscles and liver protein synthesis in vivo in meal-fed rats. Biochem. J. 136: 935-945, 1973) except that [15N]glycine was used as the tracer. Heart and lung protein synthesis was depressed by both caloric and nitrogen restriction. Muscle protein synthesis was only significantly affected by omission of calories from the diet. Kidney nitrogen content increased with the amino acid diets and decreased with the nitrogen-deficient diets. The major response of the liver to a dietary deficiency was to lose nitrogen via an increase in the rate of liver protein catabolism.

scholarly journals Short-term changes in diet composition do not affect in vivo hepatic protein synthesis in rats

2018 ◽  
Vol 314 (3) ◽  
pp. E241-E250 ◽  
Author(s):  
Andrea Lee Estrada ◽  
William Max Hudson ◽  
Paul Y. Kim ◽  
Claire Marie Stewart ◽  
Frederick F. Peelor ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Deuterium Oxide ◽  
Control Diet ◽  
Saturated Fat ◽  
Transcriptional Response ◽  
Liver Protein ◽  
Acute Response ◽  
Dietary Treatments ◽  
Hepatic Protein Synthesis

Protein synthesis is critical to protein homeostasis (proteostasis), and modifications in protein synthesis influence lifespan and the development of comorbidities associated with obesity. In the present study, we examined the acute response of liver protein synthesis to either high-fat or high-sucrose diets in order to elucidate nutrient-mediated regulation of hepatic protein synthesis in the absence of body fat accumulation. Total and endoplasmic reticulum-associated protein syntheses were assessed by use of the stable isotope, deuterium oxide (2H2O), in rats provided a control diet or diets enriched in polyunsaturated fat, saturated fat, or sucrose for 2, 4, or 7 days. The three experimental diets increased hepatic triglycerides 46–91% on day 7 and fasting insulin levels 83–117% on day 7, but did not result in differences in body weight when compared with control ( n = 6/diet/time). The fraction of newly synthesized proteins in total liver lysates and microsomes was not significantly different among dietary groups ( n = 3/diet/time). To determine whether the experimental diets provoked a transcriptional response to enhance the capacity for protein synthesis, we also measured a panel of genes linked to amino acid transport, synthesis, and processing. There were no significant differences in any of the genes measured among groups. Therefore, dietary treatments that have been linked to impaired proteostasis and that promote hepatic steatosis and insulin resistance, did not result in significant changes in total or ER-associated protein synthesis in the liver over a 7-day period.

scholarly journals General Transcriptional Coactivator PC4 Activates p53 Function

2004 ◽  
Vol 24 (5) ◽  
pp. 2052-2062 ◽  
Author(s):  
Sourav Banerjee ◽  
B. R. Prashanth Kumar ◽  
Tapas K. Kundu
Keyword(s):  
Amino Acids ◽  
Dna Binding ◽  
Physiological Role ◽  
Transcriptional Coactivator ◽  
Suppressor Activity ◽  
Tumor Suppressor Activity ◽  
In Vitro Interaction

ABSTRACT The function of p53 is modulated by several transcriptional coactivators that regulate its tumor suppressor activity. Here we report that human transcriptional coactivator PC4 enhances the DNA binding of p53 to its cognate site in vitro and directly interacts with p53 in vivo. In vitro interaction studies demonstrated that the C-terminal 30 amino acids (364 to 393) of p53 strongly interact with PC4. Surprisingly, PC4 also stimulates the sequence-specific DNA binding of p53 with the C-terminal 30 amino acids deleted (p53Δ30), suggesting that PC4 mediates enhancement of p53 DNA binding by a unique mechanism. We also demonstrated that PC4 can stimulate p53- and p53Δ30-mediated transactivation from a p53-responsive promoter. Furthermore, PC4 enhances p53- and p53Δ30-dependent apoptosis by inducing bax (a p53-targeted proapoptotic gene) gene expression. These results establish the first physiological role of PC4 as a transcriptional coactivator.

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