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Mammalian Mss51 is a Skeletal Muscle-Specific Gene Modulating Cellular Metabolism

View Article: PubMed Central - PubMed

ABSTRACT

Background:: The transforming growth factor β (TGF-β) signaling pathways modulate skeletal muscle growth, regeneration, and cellular metabolism. Several recent gene expression studies have shown that inhibition of myostatin and TGF-β1 signaling consistently leads to a significant reduction in expression of Mss51, also named Zmynd17. The function of mammalian Mss51 is unknown although a putative homolog in yeast is a mitochondrial translational activator.

Objective:: The objective of this work was to characterize mammalian MSS51.

Methods:: Quantitative RT-PCR and immunoblot of subcellular fractionation were used to determine expression patterns and localization of Mss51. The CRISPR/Cas9 system was used to reduce expression of Mss51 in C2C12 myoblasts and the function of Mss51 was evaluated in assays of proliferation, differentiation and cellular metabolism.

Results:: Mss51 was predominantly expressed in skeletal muscle and in those muscles dominated by fast-twitch fibers. In vitro, its expression was upregulated upon differentiation of C2C12 myoblasts into myotubes. Expression of Mss51 was modulated in response to altered TGF-β family signaling. In human muscle, MSS51 localized to the mitochondria. Its genetic disruption resulted in increased levels of cellular ATP, β-oxidation, glycolysis, and oxidative phosphorylation.

Conclusions:: Mss51 is a novel, skeletal muscle-specific gene and a key target of myostatin and TGF-β1 signaling. Unlike myostatin, TGF-β1 and IGF-1, Mss51 does not regulate myoblast proliferation or differentiation. Rather, Mss51 appears to be one of the effectors of these growth factors on metabolic processes including fatty acid oxidation, glycolysis and oxidative phosphorylation.

No MeSH data available.


Glycolysis and Oxidative Phosphorylation in Mss51-disrupted cells. (A) ATP production in control and Mss51-disrupted myotubes (n = 6). (B) Activity of C16 :0 fatty acid β-oxidation in control and Mss51-disrupted myotubes (n = 6). (C) Glycolysis stress test measuring the extracellular acidification rate (ECAR) in control and Mss51-disrupted myotubes treated with glucose, oligomycin, and 2-deoxy-D-glucose. (D) Glycolysis, glycolytic capacity, and glycolytic reserve calculated from the glycolysis stress test (n = 10). (E) Mitochondrial stress test results comparing oxygen consumption rates (OCR) between control and Mss51-disrupted myotubes treated with oligomycin, carbonyl cyanide-p-trifluoromethoxyphen (FCCP), and Antimycin A/Rotenone. (F) Basal respiration, ATP production, proton leak, maximum respiration, and spare respiratory capacity as calculated from the mitochondrial stress test (n = 10). *p <  0.05, ***p <  0.001.
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jnd-2-4-jnd150119-g007: Glycolysis and Oxidative Phosphorylation in Mss51-disrupted cells. (A) ATP production in control and Mss51-disrupted myotubes (n = 6). (B) Activity of C16 :0 fatty acid β-oxidation in control and Mss51-disrupted myotubes (n = 6). (C) Glycolysis stress test measuring the extracellular acidification rate (ECAR) in control and Mss51-disrupted myotubes treated with glucose, oligomycin, and 2-deoxy-D-glucose. (D) Glycolysis, glycolytic capacity, and glycolytic reserve calculated from the glycolysis stress test (n = 10). (E) Mitochondrial stress test results comparing oxygen consumption rates (OCR) between control and Mss51-disrupted myotubes treated with oligomycin, carbonyl cyanide-p-trifluoromethoxyphen (FCCP), and Antimycin A/Rotenone. (F) Basal respiration, ATP production, proton leak, maximum respiration, and spare respiratory capacity as calculated from the mitochondrial stress test (n = 10). *p <  0.05, ***p <  0.001.

Mentions: AMPKα activation switches off ATP consuming pathways and switches on ATP generating processes (glucose uptake and fatty acid oxidation) [46]. To determine if the increases in gene expression of fatty acid utilization and p-AMPKα described above resulted in increased ATP generation, we measured ATP content of populations of differentiated myotubes. Cellular ATP content was significantly increased in Mss51-disrupted myotubes (Fig. 7A). To determine if fatty acid utilization was altered in Mss51-disrupted myotubes, we measured β-oxidation of radiolabeled palmitic acid in intact control and Mss51-disrupted myotubes (Fig. 7B). Mss51-disrupted myotubes were shown to have a significantly higher β-oxidation activity.


Mammalian Mss51 is a Skeletal Muscle-Specific Gene Modulating Cellular Metabolism
Glycolysis and Oxidative Phosphorylation in Mss51-disrupted cells. (A) ATP production in control and Mss51-disrupted myotubes (n = 6). (B) Activity of C16 :0 fatty acid β-oxidation in control and Mss51-disrupted myotubes (n = 6). (C) Glycolysis stress test measuring the extracellular acidification rate (ECAR) in control and Mss51-disrupted myotubes treated with glucose, oligomycin, and 2-deoxy-D-glucose. (D) Glycolysis, glycolytic capacity, and glycolytic reserve calculated from the glycolysis stress test (n = 10). (E) Mitochondrial stress test results comparing oxygen consumption rates (OCR) between control and Mss51-disrupted myotubes treated with oligomycin, carbonyl cyanide-p-trifluoromethoxyphen (FCCP), and Antimycin A/Rotenone. (F) Basal respiration, ATP production, proton leak, maximum respiration, and spare respiratory capacity as calculated from the mitochondrial stress test (n = 10). *p <  0.05, ***p <  0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664537&req=5

jnd-2-4-jnd150119-g007: Glycolysis and Oxidative Phosphorylation in Mss51-disrupted cells. (A) ATP production in control and Mss51-disrupted myotubes (n = 6). (B) Activity of C16 :0 fatty acid β-oxidation in control and Mss51-disrupted myotubes (n = 6). (C) Glycolysis stress test measuring the extracellular acidification rate (ECAR) in control and Mss51-disrupted myotubes treated with glucose, oligomycin, and 2-deoxy-D-glucose. (D) Glycolysis, glycolytic capacity, and glycolytic reserve calculated from the glycolysis stress test (n = 10). (E) Mitochondrial stress test results comparing oxygen consumption rates (OCR) between control and Mss51-disrupted myotubes treated with oligomycin, carbonyl cyanide-p-trifluoromethoxyphen (FCCP), and Antimycin A/Rotenone. (F) Basal respiration, ATP production, proton leak, maximum respiration, and spare respiratory capacity as calculated from the mitochondrial stress test (n = 10). *p <  0.05, ***p <  0.001.
Mentions: AMPKα activation switches off ATP consuming pathways and switches on ATP generating processes (glucose uptake and fatty acid oxidation) [46]. To determine if the increases in gene expression of fatty acid utilization and p-AMPKα described above resulted in increased ATP generation, we measured ATP content of populations of differentiated myotubes. Cellular ATP content was significantly increased in Mss51-disrupted myotubes (Fig. 7A). To determine if fatty acid utilization was altered in Mss51-disrupted myotubes, we measured β-oxidation of radiolabeled palmitic acid in intact control and Mss51-disrupted myotubes (Fig. 7B). Mss51-disrupted myotubes were shown to have a significantly higher β-oxidation activity.

View Article: PubMed Central - PubMed

ABSTRACT

Background:: The transforming growth factor &beta; (TGF-&beta;) signaling pathways modulate skeletal muscle growth, regeneration, and cellular metabolism. Several recent gene expression studies have shown that inhibition of myostatin and TGF-&beta;1 signaling consistently leads to a significant reduction in expression of Mss51, also named Zmynd17. The function of mammalian Mss51 is unknown although a putative homolog in yeast is a mitochondrial translational activator.

Objective:: The objective of this work was to characterize mammalian MSS51.

Methods:: Quantitative RT-PCR and immunoblot of subcellular fractionation were used to determine expression patterns and localization of Mss51. The CRISPR/Cas9 system was used to reduce expression of Mss51 in C2C12 myoblasts and the function of Mss51 was evaluated in assays of proliferation, differentiation and cellular metabolism.

Results:: Mss51 was predominantly expressed in skeletal muscle and in those muscles dominated by fast-twitch fibers. In vitro, its expression was upregulated upon differentiation of C2C12 myoblasts into myotubes. Expression of Mss51 was modulated in response to altered TGF-&beta; family signaling. In human muscle, MSS51 localized to the mitochondria. Its genetic disruption resulted in increased levels of cellular ATP, &beta;-oxidation, glycolysis, and oxidative phosphorylation.

Conclusions:: Mss51 is a novel, skeletal muscle-specific gene and a key target of myostatin and TGF-&beta;1 signaling. Unlike myostatin, TGF-&beta;1 and IGF-1, Mss51 does not regulate myoblast proliferation or differentiation. Rather, Mss51 appears to be one of the effectors of these growth factors on metabolic processes including fatty acid oxidation, glycolysis and oxidative phosphorylation.

No MeSH data available.