Mammalian target of rapamycin/eukaryotic initiation factor 4F pathway regulates follicle growth and development of theca cells in mice

2017 ◽  
Vol 29 (4) ◽  
pp. 768 ◽  
Author(s):  
Chao Zhang ◽  
Xiao-Ran Liu ◽  
Yong-Chun Cao ◽  
Jin-Ling Tian ◽  
Di Zhen ◽  
...  
Keyword(s):  
Growth And Development ◽  
Mammalian Target Of Rapamycin ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Follicle Growth ◽  
Thecal Cell ◽  
Thecal Cells ◽  
Mtor Signalling ◽  
Mtor Signalling Pathway

The aim of the present study was to clarify the roles of the mammalian target of rapamycin (mTOR) signalling pathway in follicular growth and development of thecal cells. Using in vivo-grown and in vitro-cultured ovaries, histological changes were evaluated using haematoxylin and eosin (HE) staining. Differentially expressed genes (DEGs) from 0 day post partum (d.p.p.) to 8 d.p.p. ovaries were screened by microarray and verified by quantitative real-time polymerase chain reaction. Forty-two DEGs related to cell proliferation and differentiation were screened out, with most DEGs being related to the to mTOR signalling pathway. Then, 3 d.p.p. ovaries were retrieved and used to verify the role of mTOR signalling in follicle and thecal cell development using its activators (Ras homologue enriched in brain (Rheb) and GTP) and inhibitor (rapamycin). The development of follicles and thecal cells was significantly impaired in ovaries cultured in vitro Day 3 to Day 8. In in vitro-cultured ovaries, Rheb and GTP (is 100 ng mL–1 Rheb and 500 ng mL–1 GTP for 48 h) significantly increased follicle diameter, the percentage of primary and secondary follicles and the umber of thecal cells, and upregulated expression of mTOR, phosphorylated eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), eukaryotic initiation factor (eIF) 4F and cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17A1). Rapamycin (10 nM rapamycin for 24 h) had opposite effects to those of Rheb and GTP, and partly abrogated (significant) the effects of Rheb and GTP when added to the culture in combination with these drugs. Thus, mTOR signalling plays an important role in follicle growth and thecal cell development.

scholarly journals A MAP4 kinase related to Ste20 is a nutrient-sensitive regulator of mTOR signalling

2007 ◽  
Vol 403 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Greg M. Findlay ◽  
Lijun Yan ◽  
Julia Procter ◽  
Virginie Mieulet ◽  
Richard F. Lamb
Keyword(s):  
Amino Acids ◽  
Growth Factor ◽  
Cell Growth ◽  
Mammalian Target Of Rapamycin ◽  
Signalling Pathway ◽  
Initiation Factor ◽  
S6 Kinase ◽  
Eukaryotic Initiation Factor 4E ◽  
Mtor Signalling ◽  
Mtor Signalling Pathway

The mTOR (mammalian target of rapamycin) signalling pathway is a key regulator of cell growth and is controlled by growth factors and nutrients such as amino acids. Although signalling pathways from growth factor receptors to mTOR have been elucidated, the pathways mediating signalling by nutrients are poorly characterized. Through a screen for protein kinases active in the mTOR signalling pathway in Drosophila we have identified a Ste20 family member (MAP4K3) that is required for maximal S6K (S6 kinase)/4E-BP1 [eIF4E (eukaryotic initiation factor 4E)-binding protein 1] phosphorylation and regulates cell growth. Importantly, MAP4K3 activity is regulated by amino acids, but not the growth factor insulin and is not regulated by the mTORC1 inhibitor rapamycin. Our results therefore suggest a model whereby nutrients signal to mTORC1 via activation of MAP4K3.

scholarly journals Phosphorylation of eukaryotic initiation factor 4E (eIF4E) at Ser209 is not required for protein synthesis in vitro and in vivo

2001 ◽  
Vol 268 (20) ◽  
pp. 5375-5385 ◽  
Author(s):  
Linda McKendrick ◽  
Simon J. Morley ◽  
Virginia M. Pain ◽  
Rosemary Jagus ◽  
Bhavesh Joshi
Keyword(s):  
Protein Synthesis ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Eukaryotic Initiation Factor 4E

scholarly journals Effect of lithium on ventricular remodelling in infarcted rats via the Akt/mTOR signalling pathways

2017 ◽  
Vol 37 (2) ◽  
Author(s):  
Tsung-Ming Lee ◽  
Shinn-Zong Lin ◽  
Nen-Chung Chang
Keyword(s):  
Interstitial Fibrosis ◽  
Lithium Treatment ◽  
Cardiac Contractility ◽  
Mammalian Target Of Rapamycin ◽  
Left Ventricular ◽  
Initiation Factor ◽  
Gene Expressions ◽  
Activated T Cells ◽  
Pathological Hypertrophy ◽  
Mtor Signalling

Activation of phosphoinositide 3-kinase (PI3K)/Akt signalling is the molecular pathway driving physiological hypertrophy. As lithium, a PI3K agonist, is highly toxic at regular doses, we assessed the effect of lithium at a lower dose on ventricular hypertrophy after myocardial infarction (MI). Male Wistar rats after induction of MI were randomized to either vehicle or lithium (1 mmol/kg per day) for 4 weeks. The dose of lithium led to a mean serum level of 0.39 mM, substantially lower than the therapeutic concentrations (0.8–1.2 mM). Infarction in the vehicle was characterized by pathological hypertrophy in the remote zone; histologically, by increased cardiomyocyte sizes, interstitial fibrosis and left ventricular dilatation; functionally, by impaired cardiac contractility; and molecularly, by an increase of p-extracellular-signal-regulated kinase (ERK) levels, nuclear factor of activated T cells (NFAT) activity, GATA4 expression and foetal gene expressions. Lithium administration mitigated pathological remodelling. Furthermore, lithium caused increased phosphorylation of eukaryotic initiation factor 4E binding protein 1 (p-4E-BP1), the downstream target of mammalian target of rapamycin (mTOR). Blockade of the Akt and mTOR signalling pathway with deguelin and rapamycin resulted in markedly diminished levels of p-4E-BP1, but not ERK. The present study demonstrated that chronic lithium treatment at low doses mitigates pathological hypertrophy through an Akt/mTOR dependent pathway.

Regulation of eukaryotic initiation factor-2B activity in muscle of diabetic rats

1993 ◽  
Vol 264 (1) ◽  
pp. E101-E108 ◽  
Author(s):  
A. M. Karinch ◽  
S. R. Kimball ◽  
T. C. Vary ◽  
L. S. Jefferson
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Cardiac Muscle ◽  
Casein Kinase Ii ◽  
Diabetic Rats ◽  
Casein Kinase ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Fast Twitch

Peptide-chain initiation is inhibited in fast-twitch skeletal muscle, but not heart, of diabetic rats. We have investigated mechanisms that might maintain eukaryotic initiation factor (eIF)-2B activity, preventing loss of efficiency of protein synthesis in heart of diabetic rats but not in fast-twitch skeletal muscle. There was no change in the amount or phosphorylation state of eIF-2 in skeletal or cardiac muscle during diabetes. In contrast, eIF-2B activity was decreased in fast-twitch but not slow-twitch muscle from diabetic animals. NADP+ inhibited partially purified eIF-2B in vitro, but addition of equimolar NADPH reversed the inhibition. The NADPH-to-NADP+ ratio was unchanged in fast-twitch muscle after induction of diabetes but was increased in heart of diabetic rats, suggesting that NADPH also prevents inhibition of eIF-2B in vivo. The activity of casein kinase II, which can phosphorylate and activate eIF-2B in vitro, was significantly lower in extracts of fast-twitch, but not cardiac muscle, of diabetic rats compared with controls. The results presented here demonstrate that changes in eIF-2 alpha phosphorylation are not responsible for the effect of diabetes on eIF-2B activity in fast-twitch skeletal muscle. Modulation of casein kinase II activity may be a factor in the regulation of protein synthesis in muscle during acute diabetes. The activity of eIF-2B in heart might be maintained by the increased NADPH/NADP+.

Mammalian target of rapamycin pathway is up-regulated by both acute endurance exercise and chronic muscle contraction in rat skeletal muscle

2013 ◽  
Vol 38 (8) ◽  
pp. 862-869 ◽  
Author(s):  
Brittany A. Edgett ◽  
Melanie L. Fortner ◽  
Arend Bonen ◽  
Brendon J. Gurd
Keyword(s):  
Skeletal Muscle ◽  
Endurance Exercise ◽  
Gastrocnemius Muscle ◽  
Contractile Activity ◽  
Mammalian Target Of Rapamycin ◽  
Mtor Pathway ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Sprague Dawley ◽  
Sprague Dawley Rats

This study examined changes in the expression of translation initiation regulatory proteins and mRNA following both an acute bout of endurance exercise and chronic muscle contractile activity. Female Sprague Dawley rats ran for 2 h at 15 m·min−1 followed by an increase in speed of 5 m·min−1 every 5 min until volitional fatigue. The red gastrocnemius muscle was harvested from nonexercised animals (control; n = 6) and from animals that exercised either immediately after exercise (n = 6) or following 3 h of recovery from exercise (n = 6). Compared with control, ribosomal protein S6 (rpS6) mRNA was elevated (p < 0.05) at both 0 h (+32%) and 3 h (+47%). Both a catalytic subunit of eukaryotic initiation factor 2B (eIF2Bε) (+127%) and mammalian target of rapamycin (mTOR) mRNA (+44%) were increased at 3 h, compared with control. Phosphorylation of mTOR (+40%) and S6 kinase 1 (S6K1) (+266%) were increased immediately after exercise (p < 0.05). Female Sprague Dawley rats also underwent chronic stimulation of the peroneal nerve continuously for 7 days. The red gastrocnemius muscle was removed 24 h after cessation of the stimulation. Chronic muscle stimulation increased (p < 0.05) mTOR protein (+74%), rpS6 (+31%), and eukaryotic initiation factor 2α (+44%, p = 0.069), and this was accompanied by an increase in cytochrome c (+31%). Increased resting phosphorylation was observed for rpS6 (+51%) (p < 0.05) but not for mTOR or eukaryotic initiation factor 4E binding protein 1. These experiments demonstrate that both acute and chronic contractile activity up-regulate the mTOR pathway and mitochondrial content in murine skeletal muscle. This up-regulation of the mTOR pathway may increase translation efficiency and may also represent an important control point in exercise-mediated mitochondrial biogenesis.

scholarly journals Inactivation of eukaryotic initiation factor 2B in vitro by heat shock

1998 ◽  
Vol 334 (2) ◽  
pp. 463-467 ◽  
Author(s):  
Gert C. SCHEPER ◽  
Adri A. M. THOMAS ◽  
van Roel WIJK
Keyword(s):  
Heat Shock ◽  
Thermal Inactivation ◽  
Ribosomal Subunit ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Nucleotide Exchange ◽  
Mild Heat ◽  
Eif2α Phosphorylation ◽  
Cell Extracts

Protein synthesis in rat H35 Reuber hepatoma cells is rapidly inhibited on heat shock. At mild heat-shock temperatures the main cause for inhibition is the inactivation of the guanine nucleotide exchange factor eukaryotic initiation factor 2B (eIF2B); under more severe heat-shock conditions the activity of several initiation factors is compromised. eIF2B is required for GDP/GTP exchange on eIF2, which delivers methionyl-tRNA to the 40 S ribosomal subunit. We have tried to elucidate the mechanism underlying the inactivation of eIF2B by assays in vitro. Incubation of cell extracts at 41 °C or higher led to the inactivation of eIF2B. In agreement with observations in cells exposed to mild heat shocks, the thermal inactivation of eIF2B could be ascribed to neither eIF2α phosphorylation nor the induction of another inhibitor. With the use of glycerol gradients we show that eIF2B forms aggregates in heat-treated extracts. Furthermore eIF2B activity is protected against heat shock in thermotolerant cells. Taken together, these results suggest a role for chaperones in the control of eIF2B activity.

scholarly journals Phosphorylation of Eukaryotic Initiation Factor 2 by Heme-Regulated Inhibitor Kinase-Related Protein Kinases in Schizosaccharomyces pombe Is Important for Resistance to Environmental Stresses

2002 ◽  
Vol 22 (20) ◽  
pp. 7134-7146 ◽  
Author(s):  
Ke Zhan ◽  
Krishna M. Vattem ◽  
Bettina N. Bauer ◽  
Thomas E. Dever ◽  
Jane-Jane Chen ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Schizosaccharomyces Pombe ◽  
Environmental Stresses ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Α Subunit ◽  
Eukaryotic Initiation Factor 2 ◽  
Initiation Factor 2 ◽  
Eif2α Kinase

ABSTRACT Protein synthesis is regulated by the phosphorylation of the α subunit of eukaryotic initiation factor 2 (eIF2α) in response to different environmental stresses. One member of the eIF2α kinase family, heme-regulated inhibitor kinase (HRI), is activated under heme-deficient conditions and blocks protein synthesis, principally globin, in mammalian erythroid cells. We identified two HRI-related kinases from Schizosaccharomyces pombe which have full-length homology with mammalian HRI. The two HRI-related kinases, named Hri1p and Hri2p, exhibit autokinase and kinase activity specific for Ser-51 of eIF2α, and both activities were inhibited in vitro by hemin, as previously described for mammalian HRI. Overexpression of Hri1p, Hri2p, or the human eIF2α kinase, double-stranded-RNA-dependent protein kinase (PKR), impeded growth of S. pombe due to elevated phosphorylation of eIF2α. Cells from strains with deletions of the hri1+ and hri2+ genes, individually or in combination, exhibited a reduced growth rate when exposed to heat shock or to arsenic compounds. Measurements of in vivo phosphorylation of eIF2α suggest that Hri1p and Hri2p differentially phosphorylate eIF2α in response to these stress conditions. These results demonstrate that HRI-related enzymes are not unique to vertebrates and suggest that these eIF2α kinases are important participants in diverse stress response pathways in some lower eukaryotes.

A possible linkage between AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) signalling pathway

2003 ◽  
Vol 8 (1) ◽  
pp. 65-79 ◽  
Author(s):  
Naoki Kimura ◽  
Chiharu Tokunaga ◽  
Sushila Dalal ◽  
Christine Richardson ◽  
Ken-ichi Yoshino ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Mammalian Target Of Rapamycin ◽  
Signalling Pathway ◽  
Target Of Rapamycin ◽  
Amp Activated Protein Kinase ◽  
Mtor Signalling ◽  
Mtor Signalling Pathway

scholarly journals A region rich in aspartic acid, arginine, tyrosine, and glycine (DRYG) mediates eukaryotic initiation factor 4B (eIF4B) self-association and interaction with eIF3.

1996 ◽  
Vol 16 (10) ◽  
pp. 5328-5334 ◽  
Author(s):  
N Méthot ◽  
M S Song ◽  
N Sonenberg
Keyword(s):  
Aspartic Acid ◽  
Ribosomal Subunit ◽  
Direct Interaction ◽  
Initiation Factor ◽  
Eukaryotic Initiation Factor ◽  
Ribosome Binding ◽  
Initiation Factors ◽  
Self Association

The binding of mRNA to the ribosome is mediated by eukaryotic initiation factors eukaryotic initiation factor 4F (eIF4F), eIF4B, eIF4A, and eIF3, eIF4F binds to the mRNA cap structure and, in combination with eIF4B, is believed to unwind the secondary structure in the 5' untranslated region to facilitate ribosome binding. eIF3 associates with the 40S ribosomal subunit prior to mRNA binding. eIF4B copurifies with eIF3 and eIF4F through several purification steps, suggesting the involvement of a multisubunit complex during translation initiation. To understand the mechanism by which eIF4B promotes 40S ribosome binding to the mRNA, we studied its interactions with partner proteins by using a filter overlay (protein-protein [far Western]) assay and the two-hybrid system. In this report, we show that eIF4B self-associates and also interacts directly with the p170 subunit of eIF3. A region rich in aspartic acid, arginine, tyrosine, and glycine, termed the DRYG domain, is sufficient for self-association of eIF4B, both in vitro and in vivo, and for interaction with the p170 subunit of eIF3. These experiments suggest that eIF4B participates in mRNA-ribosome binding by acting as an intermediary between the mRNA and eIF3, via a direct interaction with the p170 subunit of eIF3.

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