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James A Carson - One of the best experts on this subject based on the ideXlab platform.
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acute myotube Protein Synthesis Regulation by il 6 related cytokines
American Journal of Physiology-cell Physiology, 2017Co-Authors: Song Gao, Larry J Durstine, Hojin Koh, Wayne Carver, Norma Frizzell, James A CarsonAbstract:IL-6 and leukemia inhibitory factor (LIF), members of the IL-6 family of cytokines, play recognized paradoxical roles in skeletal muscle mass Regulation, being associated with both growth and atrophy. Overload or muscle contractions can induce a transient increase in muscle IL-6 and LIF expression, which has a regulatory role in muscle hypertrophy. However, the cellular mechanisms involved in this Regulation have not been completely identified. The induction of mammalian target of rapamycin complex 1 (mTORC1)-dependent myofiber Protein Synthesis is an established regulator of muscle hypertrophy, but the involvement of the IL-6 family of cytokines in this process is poorly understood. Therefore, we investigated the acute effects of IL-6 and LIF administration on mTORC1 signaling and Protein Synthesis in C2C12 myotubes. The role of glycoProtein 130 (gp130) receptor and downstream signaling pathways, including phosphoinositide 3-kinase (PI3K)-Akt-mTORC1 and signal transducer and activator of transcription 3 (STAT3)-suppressor of cytokine signaling 3 (SOCS3), was investigated by administration of specific siRNA or pharmaceutical inhibitors. Acute administration of IL-6 and LIF induced Protein Synthesis, which was accompanied by STAT3 activation, Akt-mTORC1 activation, and increased SOCS3 expression. This induction of Protein Synthesis was blocked by both gp130 siRNA knockdown and Akt inhibition. Interestingly, STAT3 inhibition or Akt downstream mTORC1 signaling inhibition did not fully block the IL-6 or LIF induction of Protein Synthesis. SOCS3 siRNA knockdown increased basal Protein Synthesis and extended the duration of the Protein Synthesis induction by IL-6 and LIF. These results demonstrate that either IL-6 or LIF can activate gp130-Akt signaling axis, which induces Protein Synthesis via mTORC1-independent mechanisms in cultured myotubes. However, IL-6- or LIF-induced SOCS3 negatively regulates the activation of myotube Protein Synthesis.
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lewis lung carcinoma Regulation of mechanical stretch induced Protein Synthesis in cultured myotubes
American Journal of Physiology-cell Physiology, 2016Co-Authors: Song Gao, James A CarsonAbstract:Mechanical stretch can activate muscle and myotube Protein Synthesis through mammalian target of rapamycin complex 1 (mTORC1) signaling. While it has been established that tumor-derived cachectic factors can induce myotube wasting, the effect of this catabolic environment on myotube mechanical signaling has not been determined. We investigated whether media containing cachectic factors derived from Lewis lung carcinoma (LLC) can regulate the stretch induction of myotube Protein Synthesis. C2C12 myotubes preincubated in control or LLC-derived media were chronically stretched. Protein Synthesis Regulation by anabolic and catabolic signaling was then examined. In the control condition, stretch increased mTORC1 activity and Protein Synthesis. The LLC treatment decreased basal mTORC1 activity and Protein Synthesis and attenuated the stretch induction of Protein Synthesis. LLC media increased STAT3 and AMP-activated Protein kinase phosphorylation in myotubes, independent of stretch. Both stretch and LLC independently increased ERK1/2, p38, and NF-κB phosphorylation. In LLC-treated myotubes, the inhibition of ERK1/2 and p38 rescued the stretch induction of Protein Synthesis. Interestingly, either leukemia inhibitory factor or glycoProtein 130 antibody administration caused further inhibition of mTORC1 signaling and Protein Synthesis in stretched myotubes. AMP-activated Protein kinase inhibition increased basal mTORC1 signaling activity and Protein Synthesis in LLC-treated myotubes, but did not restore the stretch induction of Protein Synthesis. These results demonstrate that LLC-derived cachectic factors can dissociate stretch-induced signaling from Protein Synthesis through ERK1/2 and p38 signaling, and that glycoProtein 130 signaling is associated with the basal stretch response in myotubes.
Song Gao - One of the best experts on this subject based on the ideXlab platform.
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acute myotube Protein Synthesis Regulation by il 6 related cytokines
American Journal of Physiology-cell Physiology, 2017Co-Authors: Song Gao, Larry J Durstine, Hojin Koh, Wayne Carver, Norma Frizzell, James A CarsonAbstract:IL-6 and leukemia inhibitory factor (LIF), members of the IL-6 family of cytokines, play recognized paradoxical roles in skeletal muscle mass Regulation, being associated with both growth and atrophy. Overload or muscle contractions can induce a transient increase in muscle IL-6 and LIF expression, which has a regulatory role in muscle hypertrophy. However, the cellular mechanisms involved in this Regulation have not been completely identified. The induction of mammalian target of rapamycin complex 1 (mTORC1)-dependent myofiber Protein Synthesis is an established regulator of muscle hypertrophy, but the involvement of the IL-6 family of cytokines in this process is poorly understood. Therefore, we investigated the acute effects of IL-6 and LIF administration on mTORC1 signaling and Protein Synthesis in C2C12 myotubes. The role of glycoProtein 130 (gp130) receptor and downstream signaling pathways, including phosphoinositide 3-kinase (PI3K)-Akt-mTORC1 and signal transducer and activator of transcription 3 (STAT3)-suppressor of cytokine signaling 3 (SOCS3), was investigated by administration of specific siRNA or pharmaceutical inhibitors. Acute administration of IL-6 and LIF induced Protein Synthesis, which was accompanied by STAT3 activation, Akt-mTORC1 activation, and increased SOCS3 expression. This induction of Protein Synthesis was blocked by both gp130 siRNA knockdown and Akt inhibition. Interestingly, STAT3 inhibition or Akt downstream mTORC1 signaling inhibition did not fully block the IL-6 or LIF induction of Protein Synthesis. SOCS3 siRNA knockdown increased basal Protein Synthesis and extended the duration of the Protein Synthesis induction by IL-6 and LIF. These results demonstrate that either IL-6 or LIF can activate gp130-Akt signaling axis, which induces Protein Synthesis via mTORC1-independent mechanisms in cultured myotubes. However, IL-6- or LIF-induced SOCS3 negatively regulates the activation of myotube Protein Synthesis.
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lewis lung carcinoma Regulation of mechanical stretch induced Protein Synthesis in cultured myotubes
American Journal of Physiology-cell Physiology, 2016Co-Authors: Song Gao, James A CarsonAbstract:Mechanical stretch can activate muscle and myotube Protein Synthesis through mammalian target of rapamycin complex 1 (mTORC1) signaling. While it has been established that tumor-derived cachectic factors can induce myotube wasting, the effect of this catabolic environment on myotube mechanical signaling has not been determined. We investigated whether media containing cachectic factors derived from Lewis lung carcinoma (LLC) can regulate the stretch induction of myotube Protein Synthesis. C2C12 myotubes preincubated in control or LLC-derived media were chronically stretched. Protein Synthesis Regulation by anabolic and catabolic signaling was then examined. In the control condition, stretch increased mTORC1 activity and Protein Synthesis. The LLC treatment decreased basal mTORC1 activity and Protein Synthesis and attenuated the stretch induction of Protein Synthesis. LLC media increased STAT3 and AMP-activated Protein kinase phosphorylation in myotubes, independent of stretch. Both stretch and LLC independently increased ERK1/2, p38, and NF-κB phosphorylation. In LLC-treated myotubes, the inhibition of ERK1/2 and p38 rescued the stretch induction of Protein Synthesis. Interestingly, either leukemia inhibitory factor or glycoProtein 130 antibody administration caused further inhibition of mTORC1 signaling and Protein Synthesis in stretched myotubes. AMP-activated Protein kinase inhibition increased basal mTORC1 signaling activity and Protein Synthesis in LLC-treated myotubes, but did not restore the stretch induction of Protein Synthesis. These results demonstrate that LLC-derived cachectic factors can dissociate stretch-induced signaling from Protein Synthesis through ERK1/2 and p38 signaling, and that glycoProtein 130 signaling is associated with the basal stretch response in myotubes.
Assen Marintchev - One of the best experts on this subject based on the ideXlab platform.
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novel mechanisms of eif2b action and Regulation by eif2α phosphorylation
Nucleic Acids Research, 2017Co-Authors: Andrew M Bogorad, Kai Ying Lin, Assen MarintchevAbstract:Eukaryotic translation initiation factor 2 (eIF2) is a heterotrimeric GTPase, which plays a critical role in Protein Synthesis Regulation. eIF2-GTP binds Met-tRNAi to form the eIF2-GTP•Met-tRNAi ternary complex (TC), which is recruited to the 40S ribosomal subunit. Following GTP hydrolysis, eIF2-GDP is recycled back to TC by its guanine nucleotide exchange factor (GEF), eIF2B. Phosphorylation of the eIF2α subunit in response to various cellular stresses converts eIF2 into a competitive inhibitor of eIF2B, which triggers the integrated stress response (ISR). DysRegulation of eIF2B activity is associated with a number of pathologies, including neurodegenerative diseases, metabolic disorders, and cancer. However, despite decades of research, the underlying molecular mechanisms of eIF2B action and Regulation remain unknown. Here we employ a combination of NMR, fluorescence spectroscopy, site-directed mutagenesis, and thermodynamics to elucidate the mechanisms of eIF2B action and its Regulation by phosphorylation of the substrate eIF2. We present: (i) a novel mechanism for the inhibition of eIF2B activity, whereby eIF2α phosphorylation destabilizes an autoregulatory intramolecular interaction within eIF2α; and (ii) the first structural model for the complex of eIF2B with its substrate, eIF2-GDP, reaction intermediates, apo-eIF2 and eIF2-GTP, and product, TC, with direct implications for the eIF2B catalytic mechanism.
M D Hanigan - One of the best experts on this subject based on the ideXlab platform.
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effects of reduced dietary Protein and supplemental rumen protected essential amino acids on the nitrogen efficiency of dairy cows
Journal of Dairy Science, 2014Co-Authors: S Arriola I Apelo, A L Bell, K A Estes, J Ropelewski, M J De Veth, M D HaniganAbstract:When fed to meet the metabolizable Protein requirements of the National Research Council, dairy cows consume an excess of N, resulting in approximately 75% of dietary N being lost to the environment as urine and feces. Reductions in environmental N release could be attained through an improvement in N efficiency. The objective of this study was to determine if the predicted reduction in milk yield associated with feeding a low-Protein diet to lactating dairy cows could be avoided by dietary supplementation with 1 or more ruminally protected (RP) AA. Fourteen multiparous and 10 primiparous Holstein cows, and 24 multiparous Holstein × Jersey crossbred cows were used in a Youden square design consisting of 8 treatments and 3 periods. The 8 dietary treatments were (1) a standard diet containing 17% crude Protein [CP; positive control (PC)], (2) a 15% CP diet [negative control (NC)], (3) NC plus RP Met (+M), (4) NC plus RP Lys (+K), (5) NC plus RP Leu (+L), (6) NC plus RP Met and Lys (+MK), (7) NC plus RP Met and Leu (+ML), and (8) NC plus RP Met, Lys, and Leu (+MKL). Dry matter intake was not affected by treatment. Crude Protein intake was lower for NC and RP AA treatments compared with the PC treatment. No detrimental effect was detected of the low-CP diet alone or in combination with AA supplementation on milk and fat yield. However, milk Protein yield decreased for NC and +MKL diets, and lactose yield decreased for the +MKL compared with the PC diet. Milk urea N concentrations were lower for all diets, suggesting that greater N efficiency was achieved by feeding the low-Protein diet. Minimal effects of treatments on arterial plasma essential AA concentrations were detected, with only Ile and Val being significantly lower in the NC than in the PC diet. Phosphorylation ratios of signaling Proteins known to regulate mRNA translation were not affected by treatments. This study highlights the limitations of requirement models aggregated at the Protein level and the use of fixed postabsorptive efficiency to calculate milk Protein requirements. Milk Protein Synthesis Regulation by signaling pathways in vivo is still poorly understood.
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isoleucine leucine methionine and threonine effects on mammalian target of rapamycin signaling in mammary tissue
Journal of Dairy Science, 2014Co-Authors: S Arriola I Apelo, L M Singer, X Y Lin, M L Mcgilliard, N R Stpierre, M D HaniganAbstract:Improved representation of postabsorptive N metabolism in lactating dairy cows requires a better understanding of Protein Synthesis Regulation in the mammary glands. This study aimed to determine the quantitative effects of Ile, Leu, Met, and Thr on the phosphorylation state of signaling Proteins that regulate Protein Synthesis. The experiment used a composite design with a central point, 2 axial points per AA, and a complete 2(4) factorial. All of the other AA were provided at the concentrations in Dulbecco's modified Eagle's medium. The experiment was replicated with tissues from 5 lactating cows. Mammary tissue slices (0.12 ± 0.02 g) were incubated for 4h. Total and site-specific phosphorylated mammalian target of rapamycin (mTOR; Ser2448), eukaryotic elongation factor (eEF) 2 (Thr56), ribosomal Protein S6 (Ser235/236), and eukaryotic initiation factor 2α (Ser51) were determined by western immunoblotting. Tissue concentrations of the 4 AA studied responded linearly to media supply. Addition of Ile, Leu, Met, or Thr had no effect on eukaryotic initiation factor 2α phosphorylation. Isoleucine and Thr positively affected mTOR phosphorylation. However, the 2 AA had an antagonistic relationship. Similarly, Ile linearly increased ribosomal Protein S6 phosphorylation, and Thr inhibited the Ile effect. In addition, eEF2 phosphorylation was linearly decreased by Ile and Leu. Threonine curvilinearly decreased eEF2 phosphorylation, Ile and Leu negatively interacted on eEF2, and Thr tended to inhibit Leu effects on eEF2. This work demonstrated saturable responses and interactions between AA on activation of the mTOR pathway. Incorporation of these concepts into milk Protein response models will help to improve milk and milk Protein yield predictions and increase postabsorptive N efficiency and reduce N excretion by dairy cows.
Olav Rooyackers - One of the best experts on this subject based on the ideXlab platform.
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dysRegulation of mitochondrial dynamics and the muscle transcriptome in icu patients suffering from sepsis induced multiple organ failure
PLOS ONE, 2008Co-Authors: Katarina Fredriksson, Inga Tjader, Pernille Keller, Natasa Petrovic, Bo Ahlman, Camilla Scheele, Jan Wernerman, James A Timmons, Olav RooyackersAbstract:Background: Septic patients treated in the intensive care unit (ICU) often develop multiple organ failure including persistent skeletal muscle dysfunction which results in the patient’s protracted recovery process. We have demonstrated that muscle mitochondrial enzyme activities are impaired in septic ICU patients impairing cellular energy balance, which will interfere with muscle function and metabolism. Here we use detailed phenotyping and genomics to elucidate mechanisms leading to these impairments and the molecular consequences. Methodology/Principal Findings: Utilising biopsy material from seventeen patients and ten age-matched controls we demonstrate that neither mitochondrial in vivo Protein Synthesis nor expression of mitochondrial genes are compromised. Indeed, there was partial activation of the mitochondrial biogenesis pathway involving NRF2a/GABP and its target genes TFAM, TFB1M and TFB2M yet clearly this failed to maintain mitochondrial function. We therefore utilised transcript profiling and pathway analysis of ICU patient skeletal muscle to generate insight into the molecular defects driving loss of muscle function and metabolic homeostasis. Gene ontology analysis of Affymetrix analysis demonstrated substantial loss of muscle specific genes, a global oxidative stress response related to most probably cytokine signalling, altered insulin related signalling and a substantial overlap between patients and muscle wasting/inflammatory animal models. MicroRNA 21 processing appeared defective suggesting that post-transcriptional Protein Synthesis Regulation is altered by disruption of tissue microRNA expression. Finally, we were able to demonstrate that the phenotype of skeletal muscle in ICU patients is not merely one of inactivity, it appears to be an actively remodelling tissue, influenced by several mediators, all of which may be open to manipulation with the aim to improve clinical outcome. Conclusions/Significance: This first combined Protein and transcriptome based analysis of human skeletal muscle obtained from septic patients demonstrated that losses of mitochondria and muscle mass are accompanied by sustained Protein Synthesis (anabolic process) while dysRegulation of transcription programmes appears to fail to compensate for increased damage and proteolysis. Our analysis identified both validated and novel clinically tractable targets to manipulate these failing processes and pursuit of these could lead to new potential treatments.
