scholarly journals Internal Ribosome Entry Site-mediated Translation of a Mammalian mRNA Is Regulated by Amino Acid Availability

2000 ◽  
Vol 276 (15) ◽  
pp. 12285-12291 ◽  
Author(s):  
James Fernandez ◽  
Ibrahim Yaman ◽  
Rangnath Mishra ◽  
William C. Merrick ◽  
Martin D. Snider ◽  
...  
Keyword(s):  
Amino Acid ◽  
Expression System ◽  
Fold Increase ◽  
Essential Amino Acids ◽  
Amino Acid Starvation ◽  
Cellular Stress Response ◽  
Entry Site ◽  
Cationic Amino Acid ◽  
Protein Levels ◽  
Amino Acid Availability

The cationic amino acid transporter, Cat-1, facilitates the uptake of the essential amino acids arginine and lysine. Amino acid starvation causes accumulation and increased translation of cat-1 mRNA, resulting in a 58-fold increase in protein levels and increased arginine uptake. A bicistronic mRNA expression system was used to demonstrate the presence of an internal ribosomal entry sequence (IRES) within the 5′-untranslated region of the cat-1 mRNA. This study shows that IRES-mediated translation of the cat-1 mRNA is regulated by amino acid availability. This IRES causes an increase in translation under conditions of amino acid starvation. In contrast, cap-dependent protein synthesis is inhibited during amino acid starvation, which is well correlated with decreased phosphorylation of the cap-binding protein, eIF4E. These findings reveal a new aspect of mammalian gene expression and regulation that provides a cellular stress response; when the nutrient supply is limited, the activation of IRES-mediated translation of mammalian mRNAs results in the synthesis of proteins essential for cell survival.

scholarly journals Distinct Amino Acid Availability-Dependent Regulatory Mechanisms of MepS and MepM Levels in Escherichia coli

2021 ◽  
Vol 12 ◽  
Author(s):  
Yung Jae Kim ◽  
Byoung Jun Choi ◽  
Si Hyoung Park ◽  
Han Byeol Lee ◽  
Ji Eun Son ◽  
...  
Keyword(s):  
Amino Acid ◽  
Minimal Medium ◽  
Molecular Mechanisms ◽  
Aromatic Amino Acids ◽  
Normal Growth ◽  
Regulatory Mechanisms ◽  
Dependent Manner ◽  
Bacterial Physiology ◽  
Protein Levels ◽  
Amino Acid Availability

Peptidoglycan (PG) hydrolases play important roles in various aspects of bacterial physiology, including cytokinesis, PG synthesis, quality control of PG, PG recycling, and antibiotic resistance. However, the regulatory mechanisms of their expression are poorly understood. In this study, we have uncovered novel regulatory mechanisms of the protein levels of the synthetically lethal PG endopeptidases MepS and MepM, which are involved in PG synthesis. A mutant defective for both MepS and MepM was lethal in an amino acid-rich medium, whereas it exhibited almost normal growth in a minimal medium, suggesting the expendability of MepS and MepM in a minimal medium. Protein levels of MepS and MepM dramatically decreased in the minimal medium. Although MepM was revealed as a substrate of Prc, a periplasmic protease involved in the proteolysis of MepS, only the decrease in the MepS level in the minimal medium was affected by the prc depletion. Phenotypic and biochemical analyses showed that the presence of aromatic amino acids in the medium induced the accumulation of MepS, but not MepM, while the presence of glutamate increased the level of MepM, but not MepS. Together, these results demonstrate that the protein levels of the two major PG endopeptidases are regulated in an amino acid availability-dependent manner, but their molecular mechanisms and signaling are significantly distinct.

scholarly journals Changes of cellular stress response related hsp70 and abcb1 transcript and Hsp70 protein levels in Siberian freshwater amphipods upon exposure to cadmium chloride in the lethal concentration range

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8635
Author(s):  
Marina V. Protopopova ◽  
Vasiliy V. Pavlichenko ◽  
Till Luckenbach
Keyword(s):  
Stress Response ◽  
Cadmium Chloride ◽  
Fold Increase ◽  
Cellular Stress Response ◽  
Lethal Concentration ◽  
Amphipod Species ◽  
Sensitive Species ◽  
Transcript Levels ◽  
Protein Levels ◽  
Hsp70 Protein

The induction of cellular stress response systems, heat shock protein hsp70/Hsp70 and multixenobiotic transporter abcb1, by cadmium chloride (CdCl2) was explored in amphipod species with different stress adaptation strategies from the Lake Baikal area. Based on the lethal concentrations (LC) of CdCl2, the sensitivities of the different species to CdCl2 were ranked (24 hr LC50 in mg/L CdCl2 (mean/95% confidence interval)): Gammarus lacustris (1.7/1.3–2.4) < Eulimnogammarus cyaneus (2.9/2.1–4.0) < Eulimnogammarus verrucosus (5.7/3.8–8.7) < Eulimnogammarus vittatus (18.1/12.4–26.6). Conjugated dienes, indicating lipid peroxidation, were significantly increased after 24 hr exposures to 5 mg/L CdCl2 only in the more CdCl2-sensitive species G. lacustris and E. cyaneus. Upon treatment with 0.54 to 5.8 mg/L CdCl2 for 1, 6 and 24 hrs, hsp70 transcript levels were generally more increased after the longer exposure times and in the more CdCl2-sensitive species. Relating the CdCl2 exposure concentrations to LCx values revealed that across the species the increases of hsp70 transcript levels were comparatively low (up to 2.6-fold) at CdCl2 concentrations ≤LC50. Relative hsp70 transcript levels were maximally increased in E. cyaneus by 5 mg/L CdCl2 ($\hat {=}$LC70) at 24 hrs (9.1-fold increase above the respective control). When G. lacustris was exposed to 5 mg/L CdCl2 ($\hat {=}$LC90) for 24 hrs, the increase in hsp70 was in comparison to E. cyaneus considerably less pronounced (3.0-fold increase in hsp70 levels relative to control). Upon exposure of amphipods to 5 mg/L CdCl2, increases in Hsp70 protein levels compared to untreated controls were highest in E. cyaneus at 1 and 6 hrs (5 mg/L CdCl2 $\hat {=}$ LC70) and in E. verrucosus at 24 hrs (5 mg/L CdCl2 $\hat {=}$ LC45). Thus, when the fold increases in Hsp70 protein levels in the different amphipod species were related to the respective species-specific LCx values a similar bell-shaped trend as for hsp70 transcript levels was seen across the species. Transcript levels of abcb1 in CdCl2exposed individuals of the different amphipod species varied up to 4.7-fold in relation to the respective controls. In contrast to hsp70/Hsp70, abcb1 transcripts in CdCl2 exposed individuals of the different amphipod species did not indicate similar levels of induction of abcb1 at equal LCx levels across the species. Induction of hsp70 and abcb1 genes and Hsp70 proteins by CdCl2 in the lethal concentration range shows that these cellular responses are rather insensitive to CdCl2 stress in the examined amphipod species. Furthermore, the increase of expression of these cellular defense systems at such high stress levels suggests that induction of these genes is not related to the maintenance of normal metabolism but to mitigation of the effects of severe toxic stress.

Amino acids suppress proteolysis independent of insulin throughout the neonatal period

1997 ◽  
Vol 272 (4) ◽  
pp. E592-E599 ◽  
Author(s):  
B. B. Poindexter ◽  
C. A. Karn ◽  
J. A. Ahlrichs ◽  
J. Wang ◽  
C. A. Leitch ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Neonatal Period ◽  
Essential Amino Acids ◽  
Whole Body ◽  
Amino Acid Availability ◽  
Dose Dependent Fashion ◽  
Term Newborns ◽  
Dose Dependent ◽  
Acid Administration

To determine how increased amino acid availability alters rates of whole body proteolysis and the irreversible catabolism of the essential amino acids leucine and phenylalanine throughout the neonatal period, leucine and phenylalanine kinetics were measured under basal conditions and in response to intravenous amino acids in two separate groups of healthy, full-term newborns (at 3 days and 3 wk of age). The endogenous rates of appearance of leucine and phenylalanine (reflecting proteolysis) were suppressed equally in both groups and in a dose-dependent fashion (by approximately 10% with 1.2 g x kg(-1) x day(-1) and by approximately 20% with 2.4 g x kg(-1) x day(-1)) in response to intravenous amino acid delivery. Insulin concentrations remained unchanged from basal values during amino acid administration. The irreversible catabolism of leucine and phenylalanine increased in a stepwise fashion in response to intravenous amino acids; again, no differences were observed between the two groups. This study clearly demonstrates that the capacity to acutely increase rates of leucine oxidation and phenylalanine hydroxylation is fully present early in the neonatal period in normal newborns. Furthermore, these data suggest that amino acid availability is a primary regulator of proteolysis in normal newborns throughout the neonatal period.

scholarly journals The hnRNA-Binding Proteins hnRNP L and PTB Are Required for Efficient Translation of the Cat-1 Arginine/Lysine Transporter mRNA during Amino Acid Starvation

2009 ◽  
Vol 29 (10) ◽  
pp. 2899-2912 ◽  
Author(s):  
Mithu Majumder ◽  
Ibrahim Yaman ◽  
Francesca Gaccioli ◽  
Vladimir V. Zeenko ◽  
Chuanping Wang ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Binding Protein ◽  
Mrna Translation ◽  
Amino Acid Starvation ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Polypyrimidine Tract Binding Protein ◽  
Global Protein Synthesis

ABSTRACT The response to amino acid starvation involves the global decrease of protein synthesis and an increase in the translation of some mRNAs that contain an internal ribosome entry site (IRES). It was previously shown that translation of the mRNA for the arginine/lysine amino acid transporter Cat-1 increases during amino acid starvation via a mechanism that utilizes an IRES in the 5′ untranslated region of the Cat-1 mRNA. It is shown here that polypyrimidine tract binding protein (PTB) and an hnRNA binding protein, heterogeneous nuclear ribonucleoprotein L (hnRNP L), promote the efficient translation of Cat-1 mRNA during amino acid starvation. Association of both proteins with Cat-1 mRNA increased during starvation with kinetics that paralleled that of IRES activation, although the levels and subcellular distribution of the proteins were unchanged. The sequence CUUUCU within the Cat-1 IRES was important for PTB binding and for the induction of translation during amino acid starvation. Binding of hnRNP L to the IRES or the Cat-1 mRNA in vivo was independent of PTB binding but was not sufficient to increase IRES activity or Cat-1 mRNA translation during amino acid starvation. In contrast, binding of PTB to the Cat-1 mRNA in vivo required hnRNP L. A wider role of hnRNP L in mRNA translation was suggested by the decrease of global protein synthesis in cells with reduced hnRNP L levels. It is proposed that PTB and hnRNP L are positive regulators of Cat-1 mRNA translation via the IRES under stress conditions that cause a global decrease of protein synthesis.

EFFECT OF STEAM PELLETING AND REGRINDING ON THE DIGESTIBILITY OF PROTEIN IN CEREAL GRAINS, SOYBEAN MEAL AND WHEAT BRAN BY THE RAT

1968 ◽  
Vol 48 (1) ◽  
pp. 35-39 ◽  
Author(s):  
E. M. Olsen ◽  
S. J. Slinger
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Wheat Bran ◽  
Soybean Meal ◽  
Protein Digestibility ◽  
Essential Amino Acids ◽  
Cereal Grains ◽  
Protein Utilization ◽  
Amino Acid Availability ◽  
Net Protein

The effect if steam pelleting and regrinding on digestibility of protein in corn, wheat, barley, oats, soybean meal and wheat bran was tested with rats. Percentage amino acid absorption and net protein utilization (NPU) were determined for the wheat bran. Pelleting and regrinding improved the digestibility of protein in bran but had no effect on the digestibility of protein in the other ingredients tested. Increased absorption of amino acids caused by the increased digestibility of protein in bran varied considerably for individual amino acids, being greatest for isoleucine, lysine, methionine and threonine of the essential amino acids. The improvement in protein digestibility and amino acid availability was reflected in a higher NPU.

Protein degradation and synthesis measured with multiple amino acid tracers in vivo

1996 ◽  
Vol 271 (4) ◽  
pp. E733-E741 ◽  
Author(s):  
P. Tessari ◽  
R. Barazzoni ◽  
M. Zanetti ◽  
M. Vettore ◽  
S. Normand ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Protein S ◽  
Essential Amino Acids ◽  
Body Protein ◽  
Amino Acid Availability ◽  
Before And After ◽  
Branched Chain ◽  
Multiple Amino Acid

Whether tracers of different essential amino acids yield the same estimates of body protein turnover is still uncertain. Therefore, we have simultaneously determined leucine (Leu; using [14C]Leu), phenylalanine (Phe; using [13C]Phe), and tyrosine (Tyr; using [2H2]Tyr) rates of appearance (Ra) from proteolysis (PD), as well as Leu and Phe disposal, into protein synthesis (PS) both before and after an anabolic stimulus in healthy volunteers. Protein anabolism was stimulated by insulin plus a branched-chain amino acid-enriched aromatic amino acid-deficient amino acid solution, which increased Leu (from 145 +/- 9 to 266 +/- 10 mumol/l) but decreased Phe (from 57 +/- 2 to 46 +/- 3) and Tyr (from 58.7 +/- 5.5 to 21.0 +/- 2.2) concentrations. Postabsorptive endogenous Leu Ra (2.04 +/- 0.12 mumol.kg-1.min-1), Phe Ra (0.66 +/- 0.03), and Tyr Ra (0.45 +/- 0.06), as well as rates of PS determined with the leucine (1.65 +/- 0.10 mumol.kg-1.min-1) and the phenylalanine tracer (0.57 +/- 0.03), agreed well with the known abundance of these amino acids in body protein(s). After insulin and amino acids, PD was suppressed (P < 0.001) using all tracers. However, although percent suppression of endogenous Leu Ra (-->1.49 +/- 0.10 mumol.kg-1.min-1, 26 +/- 5%) and Phe Ra (-->0.53 +/- 0.02 mumol.kg-1.min-1, -20 +/- 2%) were comparable, endogenous Tyr Ra was suppressed to a larger extent (-->0.23 +/- 0.02 mumol.kg-1.min-1, -46 +/- 3% P = 0.038). PS was stimulated using the Leu (+24 +/- 7%, P < 0.02) but not the Phe (+6 +/- 4%, not significant) data. We conclude that isotopes of different essential amino acid: provide comparable estimates of PD and PS in the postabsorptive state. However, their responses to an anabolic stimulus may differ, possibly depending on exogenous amino acid availability and/or the resulting plasma levels.

scholarly journals Identification of a Novel Amino Acid Response Pathway Triggering ATF2 Phosphorylation in Mammals

2009 ◽  
Vol 29 (24) ◽  
pp. 6515-6526 ◽  
Author(s):  
Cédric Chaveroux ◽  
Céline Jousse ◽  
Yoan Cherasse ◽  
Anne-Catherine Maurin ◽  
Laurent Parry ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Amino Acid ◽  
Signal Transduction Pathway ◽  
Amino Acid Starvation ◽  
Mitogen Activated Protein Kinase ◽  
Individual Gene ◽  
Amino Acid Availability ◽  
Rna Transfection ◽  
Mitogen Activated Protein ◽  
Amino Acid Response

ABSTRACT It has been well established that amino acid availability can control gene expression. Previous studies have shown that amino acid depletion induces transcription of the ATF3 (activation transcription factor 3) gene through an amino acid response element (AARE) located in its promoter. This event requires phosphorylation of activating transcription factor 2 (ATF2), a constitutive AARE-bound factor. To identify the signaling cascade leading to phosphorylation of ATF2 in response to amino acid starvation, we used an individual gene knockdown approach by small interfering RNA transfection. We identified the mitogen-activated protein kinase (MAPK) module MEKK1/MKK7/JNK2 as the pathway responsible for ATF2 phosphorylation on the threonine 69 (Thr69) and Thr71 residues. Then, we progressed backwards up the signal transduction pathway and showed that the GTPase Rac1/Cdc42 and the protein Gα12 control the MAPK module, ATF2 phosphorylation, and AARE-dependent transcription. Taken together, our data reveal a new signaling pathway activated by amino acid starvation leading to ATF2 phosphorylation and subsequently positively affecting the transcription of amino acid-regulated genes.

Cortisol stimulates system A amino acid transport and SNAT2 expression in a human placental cell line (BeWo)

2006 ◽  
Vol 291 (3) ◽  
pp. E596-E603 ◽  
Author(s):  
Helen N. Jones ◽  
Cheryl J. Ashworth ◽  
Ken R. Page ◽  
Harry J. McArdle
Keyword(s):  
Amino Acid ◽  
Cell Line ◽  
Expression System ◽  
Isobutyric Acid ◽  
Fetal Plasma ◽  
Functional Studies ◽  
Protein Levels ◽  
System A ◽  
Cortisol Levels ◽  
Amino Isobutyric Acid

Both placental system A activity and fetal plasma cortisol concentrations are associated with intrauterine growth retardation, but it is not known if these factors are mechanistically related. Previous functional studies using hepatoma cells and fibroblasts produced conflicting results regarding the regulation of system A by cortisol. Using the b30 BeWo choriocarcinoma cell line, we investigated the regulation of system A by cortisol. System A function was analyzed using methyl amino isobutyric acid (MeAIB) transcellular transport studies. Transporter expression [system A transporter (SNAT)1/2] was studied at the mRNA and protein levels using Northern and Western blotting, respectively. Localization was carried out using immunocytochemistry. The [14C]MeAIB transfer rate across BeWo monolayers after preincubation with cortisol for 24 h was significantly increased compared with control. This was associated with a relocalization of the SNAT2 transporter at lower cortisol levels and significant upregulation of mRNA and protein expression levels at cortisol levels >1 μM. This is the first study to show functional and molecular regulation of system A by cortisol in BeWo cells. It is also the first study to identify which system A isoform is regulated. These results suggest that cortisol may be involved in upregulation of system A in the placenta to ensure sufficient amino acid supply to the developing fetus.

scholarly journals Induction of calreticulin expression in response to amino acid deprivation in Chinese hamster ovary cells

1998 ◽  
Vol 329 (2) ◽  
pp. 389-394 ◽  
Author(s):  
Richard HEAL ◽  
John McGIVAN
Keyword(s):  
Amino Acid ◽  
Chinese Hamster Ovary ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Fold Increase ◽  
Asparagine Synthetase ◽  
Mrna Levels ◽  
Amino Acid Deprivation ◽  
Ovary Cells ◽  
Protein Levels

The role of calreticulin as a stress-induced molecular chaperone protein of the endoplasmic reticulum is becoming more apparent. We characterize here the induction of calreticulin in response to complete amino acid deprivation in Chinese hamster ovary cells. Amino acid deprivation caused a 4-fold increase in calreticulin protein levels over a period of 4-10 h. In addition to an overall increase in protein levels, the glycosylation of calreticulin was increased. This glycosylation event was blocked by tunicamycin and was not required for the increase in calreticulin protein levels. Immunofluorescence studies localized calreticulin to the ER of CHO cells, and no significant change was observed after amino acid deprivation. Northern-blot analysis showed that calreticulin mRNA levels were increased approx. 10-fold in response to complete amino acid deprivation. The response was sensitive to actinomycin D and α-amanitin, implying that regulation is primarily at the level of transcription. These results are similar to the large increases in asparagine synthetase mRNA observed in response to amino acid deprivation, but the amino acid-deprivation-response element identified to be involved in asparagine synthetase induction is absent from the calreticulin promoter.

scholarly journals Ammonium-Dependent Shortening of CLS in Yeast Cells Starved for Essential Amino Acids Is Determined by the Specific Amino Acid Deprived, through Different Signaling Pathways

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Júlia Santos ◽  
Cecília Leão ◽  
Maria João Sousa
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Essential Amino Acid ◽  
Essential Amino Acids ◽  
Amino Acid Starvation ◽  
Yeast Cells ◽  
Environmental Interventions ◽  
Specific Amino Acid ◽  
Chronological Life Span ◽  
In Cells

Ammonium (NH4+) leads to chronological life span (CLS) shortening inSaccharomyces cerevisiaeBY4742 cells, particularly evident in cells starved for auxotrophy-complementing amino acids (leucine, lysine, and histidine) simultaneously. Here, we report that the effect ofNH4+on aging yeast depends on the specific amino acid they are deprived of. Compared with no amino acid starvation, starvation for leucine alone or in combination with histidine resulted in the most pronouncedNH4+-induced CLS shortening, whereas starvation for lysine, alone or in combination with histidine resulted in the least sensitivity toNH4+. We also show thatNH4+-induced CLS shortening is mainly mediated by Tor1p in cells starved for leucine or histidine but by Ras2p in cells starved for lysine, and in nonstarved cells. Sch9p protected cells from the effect ofNH4+under all conditions tested (starved or nonstarved cells), which was associated with Sch9p-dependent Hog1p phosphorylation. Our data show thatNH4+toxicity can be modulated through manipulation of the specific essential amino acid supplied to cells and of the conserved Ras2p, Tor1p, and Sch9p regulators, thus providing new clues to the development of environmental interventions for CLS extension and to the identification of new therapeutic targets for diseases associated with hyperammonemia.

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