scholarly journals Lutropin increases phosphorylation of a 33 000-dalton ribosomal protein in rat tumour Leydig cells

1982 ◽  
Vol 204 (3) ◽  
pp. 809-815 ◽  
Author(s):  
G H Bakker ◽  
J W Hoogerbrugge ◽  
F F G Rommerts ◽  
H J van der Molen
Keyword(s):  
Protein Synthesis ◽  
Luteinizing Hormone ◽  
Subcellular Localization ◽  
Ribosomal Protein ◽  
Molecular Mass ◽  
Leydig Cell ◽  
Leydig Cells ◽  
Ribosomal Subunit ◽  
Ribosomal Protein S6 ◽  
Leydig Cell Tumour

Addition of lutropin (luteinizing hormone, ‘LH’) and 3-isobutyl-1-methylxanthine to tumour Leydig cells stimulated phosphorylation of five proteins, of 17 000, 22 000, 24 000, 33 000 and 57 000 Da. Phosphorylation of these proteins coincided with increased pregnenolone production. Phosphorylation of a 33 000-Da protein was lutropin-dependent in Leydig cells isolated from a Leydig-cell tumour, from immature testes or from mature testes. In tumour Leydig cells this protein was present in the small ribosomal subunit. Incubation of tumour Leydig cells with either cycloheximide or puromycin inhibited both basal and lutropin-dependent pregnenolone production, by approx. 90% and 98% respectively. In contrast, basal pregnenolone production in Leydig cells from immature and mature testes was insensitive to cycloheximide or puromycin. Cycloheximide or puromycin increased phosphorylation of the 33 000-Da phosphoprotein by approx. 130% and 80% respectively (effect of lutropin/3-isobutyl-1-methylxanthine on phosphorylation: 100%). The molecular mass, the subcellular localization and the sensitivity to phosphorylation in the presence of inhibitors of protein synthesis indicate that the 33 000-Da protein could be similar to ribosomal protein S6.

scholarly journals Specific protein synthesis in isolated rat testis leydig cells. Influence of luteinizing hormone and cycloheximide

1977 ◽  
Vol 162 (2) ◽  
pp. 341-346 ◽  
Author(s):  
F H A Janszen ◽  
B A Cooke ◽  
H J van der Molen
Keyword(s):  
Protein Synthesis ◽  
Luteinizing Hormone ◽  
Leydig Cell ◽  
Half Life ◽  
Leydig Cells ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Protein Band ◽  
Specific Protein ◽  
Rat Testis

The effect of luteinizing hormone (luteotropin) and cycloheximide on specific protein synthesis in rat testis Leydig cells has been investigated. Proteins were labelled with either I114C]leucine, [3H]leucine or [35S]methionine during incubation with Leydig-cell suspensions in vitro. Total protein was extracted from the cells and separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. No detectable increase in the synthesis of specific proteins could be observed after incubation of Leydig cells with luteinizing hormone for up to 1 h. However, after a 2h incubation period, an increase in [35S]methionine incorporation was observed in a protein with an apparent mol.wt. of 21000 (referred to as ‘protein 21’). When, after labelling of this protein with [35S]-methionine, Leydig cells were incubated for another 30min with cycloheximide, no decrease in radioactivity of this protein band was observed, indicating that it does not have a short half-life. However, another protein band was detected, which after incubation with cycloheximide disappeared rapidly, the reaction following first-order kinetics, with a half-life of about 11 min. This protein, with an apparent mol.wt. of 33000 (referred to as “protein 33”), was found to be located in the particulate fraction of the Leydig cell, and could not be demonstrated in other rat testis-cell types or blood cells. No effect of luteinizing hormone on molecular weight, subcellular localization or half-life of protein 33 was observed. A possible role for protein 33 and protein 21 in the mechanism of action of luteinizing hormone on testosterone production of Leydig cells is discussed.

p70 Ribosomal protein S6 kinase (Rps6kb1): an update

2014 ◽  
Vol 67 (12) ◽  
pp. 1019-1025 ◽  
Author(s):  
Farnaz Bahrami-B ◽  
Parvin Ataie-Kachoie ◽  
Mohammad H Pourgholami ◽  
David L Morris
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Protein ◽  
Ribosomal Proteins ◽  
Ribosomal Subunit ◽  
Mtor Inhibitors ◽  
Therapeutic Index ◽  
Drug Induced ◽  
S6 Kinase ◽  
Ribosomal Protein S6 ◽  
Ribosomal Protein S6 Kinase

The Rps6kb1 gene encodes the 70 kDa ribosomal protein S6 kinase (p70S6K), which is a serine/threonine kinase regulated by phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway. p70S6K plays a crucial role in controlling cell cycle, growth and survival. The PI3K/mTOR signalling pathway is one of the major mechanisms for controlling cell survival, proliferation and metabolism and is the central regulator of translation of some components of protein synthesis system. Upon activation, this kinase phosphorylates S6 protein of ribosomal subunit 40S resulting in selective translation of unique family of mRNAs that contain oligopyrimidine tract on 5’ transcriptional site (5′TOP). 5′TOP mRNAs are coding the components of translational apparatus including ribosomal proteins and elongation factors. Due to the role of p70S6K in protein synthesis and also its involvement in a variety of human diseases ranging from diabetes and obesity to cancer, p70S6K is now being considered as a new therapeutic target for drug development. Furthermore, p70S6K acts as a biomarker for response to immunosuppressant as well as anticancer effects of inhibitors of the mTOR. Because of the narrow therapeutic index of mTOR inhibitors, drug monitoring is essential, and this is usually done by measuring blood drug levels, therapeutic response and drug-induced adverse effects. Recent studies have suggested that plasma p70S6K is a reliable index for the monitoring of patient response to mTOR inhibitors. Therefore, a better understanding of p70S6K and its role in various pathological conditions could enable the development of strategies to aid diagnosis, prognosis and treatment schedules.

scholarly journals Leydig Cell Protein Synthesis and Steroidogenesis in Response to Acute Stimulation by Luteinizing Hormone in Rats1

1998 ◽  
Vol 59 (2) ◽  
pp. 263-270 ◽  
Author(s):  
Lindi Luo ◽  
Haolin Chen ◽  
Douglas M. Stocco ◽  
Barry R. Zirkin
Keyword(s):  
Protein Synthesis ◽  
Luteinizing Hormone ◽  
Leydig Cell ◽  
Cell Protein

Binding of thyroid hormone to the goat testicular Leydig cell induces the generation of a proteinaceous factor which stimulates androgen release

1994 ◽  
Vol 143 (3) ◽  
pp. 549-556 ◽  
Author(s):  
N R Jana ◽  
S Bhattacharya
Keyword(s):  
Protein Synthesis ◽  
Leydig Cell ◽  
Leydig Cells ◽  
Actinomycin D ◽  
Competitive Inhibition ◽  
Binding Capacity ◽  
Cell Protein ◽  
Scatchard Analysis ◽  
Cell Nuclei ◽  
Stimulation Of

Abstract Leydig cells isolated from goat testis were sonicated and pure nuclear preparations obtained for 125I-3,5,3′-triiodothyronine (T3)-binding assay. Under optimum assay conditions of pH 7·2 at 37 °C and 90 min of incubation, binding of 125I-T3 to Leydig cell nuclei reached saturation at 1·2 nmol/l concentration. A Scatchard analysis of T3 binding exhibited a Kd of 0·535 × 10−9 mol/l and a maximum binding capacity of 1·25 pmol/mg DNA. Competitive inhibition studies showed T3 binding to be analogue specific. The physiological relevance of T3 binding to goat Leydig cell was examined by adding increasing concentrations of T3 to the Leydig cell incubation (1×10 cells/incubation). T3 (10, 25 and 50 ng/ml or 4, 10 and 20 ng/incubation) resulted a dose dependent increase in androgen release and in all cases stimulation of androgen release was statistically significant (P<0·01) compared with control. Stimulation of Leydig cell androgen release by T3 was significantly inhibited by actinomycin-D (P<0·01) and cycloheximide (P<0·01). T3 had additive stimulatory effects on LH-augmented androgen release from Leydig cells. T3 (50 ng/ml or 20 ng/incubation) effected a more than twofold increase in Leydig cell protein synthesis compared with control and both actinomycin-D and cycloheximide (50 μg/ml) inhibited it completely. The data indicated that the stimulatory effect of T3 on androgen release is mediated via T3-induced protein(s). Sub-cellular fractions obtained from T3-treated Leydig cells showed an increase in protein synthesis in mitochondrial and soluble supernatant fractions (100 k sup) and it was only 100 k sup which stimulated androgen release from Leydig cells in separate incubations. Treatment of 100 k sup with trypsin or heat abolished its stimulatory effect. Incubation of Leydig cells with T3 for different times showed an increase in protein synthesis prior to the stimulation of androgen release. The results therefore indicated that T3 binding to Leydig cells induced the generation of a proteinaceous factor(s) which in turn stimulated androgen release. Journal of Endocrinology (1994) 143, 549–556

scholarly journals Death-Associated Protein Kinase Phosphorylates Mammalian Ribosomal Protein S6 and Reduces Protein Synthesis†

Biochemistry ◽  
2006 ◽  
Vol 45 (45) ◽  
pp. 13614-13621 ◽  
Author(s):  
Andrew M. Schumacher ◽  
Anastasia V. Velentza ◽  
D. Martin Watterson ◽  
John Dresios
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase ◽  
Ribosomal Protein ◽  
Ribosomal Protein S6 ◽  
Death Associated Protein Kinase

scholarly journals Stimulation of skeletal muscle myofibrillar protein synthesis, p70 S6 kinase phosphorylation, and ribosomal protein S6 phosphorylation by inhibition of myostatin in mature mice

2009 ◽  
Vol 296 (3) ◽  
pp. E567-E572 ◽  
Author(s):  
Stephen Welle ◽  
Kerri Burgess ◽  
Sangeeta Mehta
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Protein ◽  
Myofibrillar Protein ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
S6 Kinase ◽  
P70 S6 Kinase ◽  
Ribosomal Protein S6 ◽  
The Mean ◽  
Myofibrillar Protein Synthesis

Knocking out myostatin activity during development increases the rate of muscle protein synthesis. The present study was done to determine whether postdevelopmental loss of myostatin activity stimulates myofibrillar protein synthesis and the phosphorylation of some of the proteins involved in regulation of protein synthesis rate. Myostatin activity was inhibited for 4 days, in 4- to 5-mo-old male mice, with injections of an anti-myostatin antibody (JA16). The mean myofibrillar synthesis rate increased 19% ( P < 0.01) relative to the mean rate in saline-treated mice, as determined by incorporation of deuterium-labeled phenylalanine. JA16 increased phosphorylation of p70 S6 kinase (S6K) and ribosomal protein S6 (rpS6) 1.9-fold ( P < 0.05). It did not affect phosphorylation of eukaryotic initiation factor 4E-binding protein-1 or Akt. Microarrays and real-time PCR analyses indicated that JA16 administration did not selectively enrich levels of mRNAs encoding myofibrillar proteins, ribosomal proteins, or translation initiation and elongation factors. Rapamycin treatment did not affect the rate of myofibrillar protein synthesis whether or not the mice received JA16 injections, although it eliminated the phosphorylation of S6K and rpS6. We conclude that the normal level of myostatin activity in mature muscle is sufficient to inhibit myofibrillar synthesis rate and phosphorylation of S6K and rpS6. Reversal of the inhibition of myofibrillar synthesis with an anti-myostatin antibody is not dependent on mTOR activation.

scholarly journals Correlation of protein kinase activation and testosterone production after stimulation of Leydig cells with luteinizing hormone

1976 ◽  
Vol 160 (3) ◽  
pp. 439-446 ◽  
Author(s):  
B A Cooke ◽  
M L Lindh ◽  
F H A Janszen
Keyword(s):  
Protein Kinase ◽  
Luteinizing Hormone ◽  
Cyclic Amp ◽  
Protein Kinases ◽  
Leydig Cell ◽  
Leydig Cells ◽  
Kinase Activation ◽  
Testosterone Production ◽  
Protein Kinase Activation ◽  
Stimulation Of

The effect of different doses of luteinizing hormone on activation of protein kinases, cyclic AMP and testosterone production was studied in purified rat testis Leydig-cell preparations in the presence of 3-isobutyl-1-methylxanthine (a phosphodiesterase inhibitor). In addition, the nature of the protein kinases present in these cells and other tissues was investigated. The following results were obtained. 1. With all the amounts of luteinizing hormone used (0.1-1000 ng/ml), both activation of protein kinase and stimulation of testosterone production were demonstrated. With the lowest amount of luteinizing hormone (0.1 ng/ml), an 8.4±0.9% (S.E.M.,n=6) stimulation of protein kinase activation occurred, increasing to 100% with 1000 ng/ml, compared with 3.2±1.0%(S.E.M.,n=7) and 100% stimulation of testosterone production with 0.1 and 100 ng/ml respectively. 2. With amounts of luteinizing hormone up to 1 ng/ml (which gave half-maximal stimulation of testosterone production) no detectable increases in net cyclic AMP production were obtained. With higher amounts of luteinizing hormone, cyclic AMP production increased, but maximal production was not reached with 1000 ng/ml. 3. Two isoenzymic forms of protein kinase were present in Leydig cells and seminiferous tubules; type I was eluted with 0.075 M-and type II with 0.22-0.25 M-NaCl from DEAE-cellulose columns. 4. The protein kinase activity was not affected by the presence of erythrocytes in the Leydig-cell preparation, but varied depending on the type of histone used as substrate (histone F2b > mixed > histone F1).

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