scholarly journals Differentiation of Murine C2C12 Myoblasts Strongly Reduces the Effects of Myostatin on Intracellular Signaling

Biomolecules ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 695
Author(s):  
Juulia H. Lautaoja ◽  
Satu Pekkala ◽  
Arja Pasternack ◽  
Mika Laitinen ◽  
Olli Ritvos ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Intracellular Signaling ◽  
Negative Regulator ◽  
C2c12 Cells ◽  
C2c12 Myotubes ◽  
Receptor Ligands ◽  
In Vivo Models ◽  
Altered Expression ◽  
Activin Receptor ◽  
Noncanonical Signaling

Alongside in vivo models, a simpler and more mechanistic approach is required to study the effects of myostatin on skeletal muscle because myostatin is an important negative regulator of muscle size. In this study, myostatin was administered to murine (C2C12) and human (CHQ) myoblasts and myotubes. Canonical and noncanonical signaling downstream to myostatin, related ligands, and their receptor were analyzed. The effects of tumorkines were analyzed after coculture of C2C12 and colon cancer-C26 cells. The effects of myostatin on canonical and noncanonical signaling were strongly reduced in C2C12 cells after differentiation. This may be explained by increased follistatin, an endogenous blocker of myostatin and altered expression of activin receptor ligands. In contrast, CHQ cells were equally responsive to myostatin, and follistatin remained unaltered. Both myostatin administration and the coculture stimulated pathways associated with inflammation, especially in C2C12 cells. In conclusion, the effects of myostatin on intracellular signaling may be cell line- or organism-specific, and C2C12 myotubes seem to be a nonoptimal in vitro model for investigating the effects of myostatin on canonical and noncanonical signaling in skeletal muscle. This may be due to altered expression of activin receptor ligands and their regulators during muscle cell differentiation.

scholarly journals LOW-INTENSITY EXERCISE ENHANCES MUSCULAR ANDROGEN/ANDROGEN RECEPTOR TO INHIBIT MYOSTATIN PATHWAY

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S85-S86
Author(s):  
Bo-Kyung Son ◽  
Masato Eto ◽  
Miya Oura ◽  
Masahiro Akishita
Keyword(s):  
Skeletal Muscle ◽  
Androgen Receptor ◽  
Electric Pulse ◽  
Negative Regulator ◽  
Muscle Size ◽  
C2c12 Myotubes ◽  
Protein Levels ◽  
Low Intensity ◽  
Low Intensity Exercise ◽  
Response To Exercise

Abstract Background: Physical exercise is well documented to induce muscle size, strength, and energy metabolism. Although the contribution of systemic or local androgen in exercise-adapted muscle hypertrophy has been suggested, less is known about the molecular pathway of androgen in response to exercise. In the present study, we examined roles of androgen/androgen receptor (AR) after exercise, especially for the suppression of myostatin, a potent negative regulator of muscle mass. Methods and Results: To examine the effects of exercise, we employed low-intensity exercise in mice and electric pulse stimulation (EPS) in C2C12 myotubes. Both mRNA and protein levels of AR significantly increased in skeletal muscle of low-intensity exercised mice and C2C12 myotubes exposed to EPS. Production of testosterone and DHT from EPS-treated C2C12 myotubes was markedly increased. Of interest, we found that myostatin was clearly inhibited by EPS, and its inhibition was significantly abrogated by flutamide, a specific antagonist of AR. Furthermore, IL-6 and phospho-STAT3 (pSTAT3) expression, the downstream pathway of myostatin, were decreased by EPS and this was also reversed by flutamide. Similar downregulation of myostatin and IL-6 was seen in skeletal muscle of low-intensity exercised mice. Conclusion: Muscle AR expression and androgen production were increased by exercise and EPS treatment. As a mechanistical insight, it is suggested that AR inhibited myostatin expression transcriptionally, which downregulates IL-6/pSTAT3 pathway and thus contributes to the prevention of muscle degradation.

α7β1-Integrin regulates mechanotransduction and prevents skeletal muscle injury

2006 ◽  
Vol 290 (6) ◽  
pp. C1660-C1665 ◽  
Author(s):  
Marni D. Boppart ◽  
Dean J. Burkin ◽  
Stephen J. Kaufman
Keyword(s):  
Skeletal Muscle ◽  
Muscle Damage ◽  
Intracellular Signaling ◽  
Ex Vivo ◽  
Negative Regulator ◽  
Blue Dye ◽  
The Matrix ◽  
Mitogen Activated Protein ◽  
Exercise Induced

α7β1-Integrin links laminin in the extracellular matrix with the cell cytoskeleton and therein mediates transduction of mechanical forces into chemical signals. Muscle contraction and stretching ex vivo result in activation of intracellular signaling molecules that are integral to postexercise injury responses. Because α7β1-integrin stabilizes muscle and provides communication between the matrix and cytoskeleton, the role of this integrin in exercise-induced cell signaling and skeletal muscle damage was assessed in wild-type and transgenic mice overexpressing the α7BX2 chain. We report here that increasing α7β1-integrin inhibits phosphorylation of molecules associated with muscle damage, including the mitogen-activated protein kinases (JNK, p38, and ERK), following downhill running. Likewise, activation of molecules associated with hypertrophy (AKT, mTOR, and p70S6k) was diminished in mice overexpressing integrin. While exercise resulted in Evans blue dye-positive fibers, an index of muscle damage, increased integrin protected mice from injury. Moreover, exercise leads to an increase in α7β1 protein. These experiments provide the first evidence that α7β1-integrin is a negative regulator of mechanotransduction in vivo and provides resistance to exercise-induced muscle damage.

scholarly journals Myostatin inhibits IGF-I-induced myotube hypertrophy through Akt

2009 ◽  
Vol 297 (5) ◽  
pp. 1124-1132 ◽  
Author(s):  
Michael R. Morissette ◽  
Stuart A. Cook ◽  
Cattleya Buranasombati ◽  
Michael A. Rosenberg ◽  
Anthony Rosenzweig
Keyword(s):  
Skeletal Muscle ◽  
Knockout Mice ◽  
Molecular Mechanisms ◽  
Muscle Growth ◽  
Dominant Negative ◽  
Negative Regulator ◽  
C2c12 Myotubes ◽  
Akt Phosphorylation ◽  
Igf I

Myostatin is a highly conserved negative regulator of skeletal muscle growth. Loss of functional myostatin in cattle, mice, sheep, dogs, and humans results in increased muscle mass. The molecular mechanisms responsible for this increase in muscle growth are not fully understood. Previously, we have reported that phenylephrine-induced cardiac muscle growth and Akt activation are enhanced in myostatin knockout mice compared with controls. Here we report that skeletal muscle from myostatin knockout mice show increased Akt protein expression and overall activity at baseline secondary to an increase in Akt mRNA. We examined the functional role of myostatin modulation of Akt in C2C12 myotubes, a well-established in vitro model of skeletal muscle hypertrophy. Adenoviral overexpression of myostatin attenuated the insulin-like growth factor-I (IGF-I)-mediated increase in myotube diameter, as well as IGF-I-stimulated Akt phosphorylation. Inhibition of myostatin by overexpression of the NH2-terminal portion of myostatin was sufficient to increase myotube diameter and Akt phosphorylation. Coexpression of myostatin and constitutively active Akt (myr-Akt) restored the increase in myotube diameter. Conversely, expression of dominant negative Akt (dn-Akt) with the inhibitory myostatin propeptide blocked the increase in myotube diameter. Of note, ribosomal protein S6 phosphorylation and atrogin-1/muscle atrophy F box mRNA were increased in skeletal muscle from myostain knockout mice. Together, these data suggest myostatin regulates muscle growth at least in part through regulation of Akt.

Myostatin reduces Akt/TORC1/p70S6K signaling, inhibiting myoblast differentiation and myotube size

2009 ◽  
Vol 296 (6) ◽  
pp. C1258-C1270 ◽  
Author(s):  
Anne Ulrike Trendelenburg ◽  
Angelika Meyer ◽  
Daisy Rohner ◽  
Joseph Boyle ◽  
Shinji Hatakeyama ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Atrophy ◽  
Transforming Growth Factor ◽  
Negative Regulator ◽  
Bone Morphogenetic Protein 2 ◽  
Muscle Size ◽  
Skeletal Muscle Atrophy ◽  
Myoblast Differentiation ◽  
Activin Receptor

Myostatin is a negative regulator of skeletal muscle size, previously shown to inhibit muscle cell differentiation. Myostatin requires both Smad2 and Smad3 downstream of the activin receptor II (ActRII)/activin receptor-like kinase (ALK) receptor complex. Other transforming growth factor-β (TGF-β)-like molecules can also block differentiation, including TGF-β1, growth differentiation factor 11 (GDF-11), activins, bone morphogenetic protein 2 (BMP-2) and BMP-7. Myostatin inhibits activation of the Akt/mammalian target of rapamycin (mTOR)/p70S6 protein synthesis pathway, which mediates both differentiation in myoblasts and hypertrophy in myotubes. Blockade of the Akt/mTOR pathway, using small interfering RNA to regulatory-associated protein of mTOR (RAPTOR), a component of TOR signaling complex 1 (TORC1), increases myostatin-induced phosphorylation of Smad2, establishing a myostatin signaling-amplification role for blockade of Akt. Blockade of RAPTOR also facilitates myostatin's inhibition of muscle differentiation. Inhibition of TORC2, via rapamycin-insensitive companion of mTOR (RICTOR), is sufficient to inhibit differentiation on its own. Furthermore, myostatin decreases the diameter of postdifferentiated myotubes. However, rather than causing upregulation of the E3 ubiquitin ligases muscle RING-finger 1 ( MuRF1) and muscle atrophy F-box ( MAFbx), previously shown to mediate skeletal muscle atrophy, myostatin decreases expression of these atrophy markers in differentiated myotubes, as well as other genes normally upregulated during differentiation. These findings demonstrate that myostatin signaling acts by blocking genes induced during differentiation, even in a myotube, as opposed to activating the distinct “atrophy program.” In vivo, inhibition of myostatin increases muscle creatine kinase activity, coincident with an increase in muscle size, demonstrating that this in vitro differentiation measure is also upregulated in vivo.

scholarly journals Notch Inhibition via GSI Treatment Elevates Protein Synthesis in C2C12 Myotubes

Biology ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 115
Author(s):  
Joshua R. Huot ◽  
Joseph S. Marino ◽  
Michael J. Turner ◽  
Susan T. Arthur
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Notch Signaling ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
C2c12 Cells ◽  
Skeletal Muscle Regeneration ◽  
C2c12 Myotubes ◽  
Myonuclear Domain ◽  
Myotube Hypertrophy

The role of Notch signaling is widely studied in skeletal muscle regeneration but little is known about its influences on muscle protein synthesis (MPS). The purpose of this study was to investigate whether Notch signaling is involved in the regulation of MPS. C2C12 cells were treated with a γ-secretase inhibitor (GSI), to determine the effect of reduced Notch signaling on MPS and anabolic signaling markers. GSI treatment increased myotube hypertrophy by increasing myonuclear accretion (nuclei/myotube: p = 0.01) and myonuclear domain (myotube area per fusing nuclei: p < 0.001) in differentiating C2C12 cells. GSI treatment also elevated myotube hypertrophy in differentiated C2C12s (area/myotube; p = 0.01). In concert, GSI treatment augmented pmTOR Ser2448 (p = 0.01) and protein synthesis (using SUnSET method) in myotubes (p < 0.001). Examining protein expression upstream of mTOR revealed reductions in PTEN (p = 0.04), with subsequent elevations in pAKT Thr308 (p < 0.001) and pAKT Ser473 (p = 0.05). These findings reveal that GSI treatment elevates myotube hypertrophy through both augmentation of fusion and MPS. This study sheds light on the potential multifaceted roles of Notch within skeletal muscle. Furthermore, we have demonstrated that Notch may modulate the PTEN/AKT/mTOR pathway.

scholarly journals Regulation of Skeletal Muscle DRP-1 and FIS-1 Protein Expression by IL-6 Signaling

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Dennis K. Fix ◽  
Brandon N. VanderVeen ◽  
Brittany R. Counts ◽  
James A. Carson
Keyword(s):  
Skeletal Muscle ◽  
Intracellular Signaling ◽  
Transmembrane Protein ◽  
Mitochondrial Fission ◽  
Tibialis Anterior Muscle ◽  
C2c12 Myotubes ◽  
Extracellular Signal ◽  
Control Plasmid ◽  
Cultured Myotubes ◽  
Transcription 3

IL-6 signals through the ubiquitously expressed glycoprotein 130 (gp130) transmembrane protein to activate intracellular signaling that includes signal transducer and activator of transcription 3 (STAT3) and extracellular signal-regulated kinase 1/2 (ERK1/2). Dynamin-1-like protein (DRP-1) and mitochondrial fission 1 protein (FIS-1) are key proteins in the process of mitochondrial fission and have emerged as IL-6-sensitive targets. The purpose of this study was to examine the regulation of DRP-1 and FIS-1 expression by IL-6 and gp130 signaling in myotubes and skeletal muscle. Fully differentiated C2C12 myotubes were treated with 100 ng of IL-6 for 24 hours in the presence of gp130siRNA, C188-9 (STAT3 inhibitor), or PD98059 (ERK1/2 inhibitor). Male C57BL/6 (B6) and muscle-specific gp130 knockout mice (KO) had IL-6 systemically overexpressed for 2 weeks by transient transfection with 50 ng of an IL-6-expressing or control plasmid in the quadriceps muscles, and the tibialis anterior muscle was analyzed to determine systemic effects of IL-6. IL-6 induced DRP-1 and FIS-1 expression in myotubes 124% and 82% (p=.001) and in skeletal muscle 97% and 187% (p=.001). Myotube gp130 knockdown suppressed the IL-6 induction of DRP-1 68% (p=.002) and FIS-1 65% (p=.001). Muscle KO suppressed the IL-6 induction of DRP-1 220% (p=.001) and FIS-1 121% (p=.001). ERK1/2 inhibition suppressed the IL-6 induction of DRP-1 59% (p=.0003) and FIS-1 102% (p=.0001) in myotubes, while there was no effect of STAT3 inhibition. We report that chronically elevated IL-6 can directly induce DRP-1 and FIS-1 expression through gp130 signaling in cultured myotubes and skeletal muscle. Furthermore, ERK 1/2 signaling is necessary for the IL-6 induction of DRP-1 and FIS-1 expression in myotubes.

scholarly journals Blocking Activin Receptor Ligands Is Not Sufficient to Rescue Cancer-Associated Gut Microbiota—A Role for Gut Microbial Flagellin in Colorectal Cancer and Cachexia?

Cancers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1799 ◽  
Author(s):  
Satu Pekkala ◽  
Anniina Keskitalo ◽  
Emilia Kettunen ◽  
Sanna Lensu ◽  
Noora Nykänen ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Gut Microbiota ◽  
Tumor Formation ◽  
C2c12 Myotubes ◽  
Muscle Loss ◽  
Receptor Ligands ◽  
Activin Receptor ◽  
Before And After ◽  
Inflammatory Proteins

Colorectal cancer (CRC) and cachexia are associated with the gut microbiota and microbial surface molecules. We characterized the CRC-associated microbiota and investigated whether cachexia affects the microbiota composition. Further, we examined the possible relationship between the microbial surface molecule flagellin and CRC. CRC cells (C26) were inoculated into mice. Activin receptor (ACVR) ligands were blocked, either before tumor formation or before and after, to increase muscle mass and prevent muscle loss. The effects of flagellin on C26-cells were studied in vitro. The occurrence of similar phenomena were studied in murine and human tumors. Cancer modulated the gut microbiota without consistent effects of blocking the ACVR ligands. However, continued treatment for muscle loss modified the association between microbiota and weight loss. Several abundant microbial taxa in cancer were flagellated. Exposure of C26-cells to flagellin increased IL6 and CCL2/MCP-1 mRNA and IL6 excretion. Murine C26 tumors expressed more IL6 and CCL2/MCP-1 mRNA than C26-cells, and human CRC tumors expressed more CCL2/MCP-1 than healthy colon sites. Additionally, flagellin decreased caspase-1 activity and the production of reactive oxygen species, and increased cytotoxicity in C26-cells. Conditioned media from flagellin-treated C26-cells deteriorated C2C12-myotubes and decreased their number. In conclusion, cancer increased flagellated microbes that may promote CRC survival and cachexia by inducing inflammatory proteins such as MCP-1. Cancer-associated gut microbiota could not be rescued by blocking ACVR ligands.

scholarly journals Ubiquitin E3 ligases Atrogin-1 and MuRF1 protein contents are differentially regulated in the rapamycin-sensitive mTOR-S6K1 signaling pathway in C2C12 myotubes

2021 ◽  
Author(s):  
Yusuke Nishimura ◽  
Ibrahim Musa ◽  
Peter Dawson ◽  
Lars Holm ◽  
Yu-Chiang Lai
Keyword(s):  
Skeletal Muscle ◽  
Protein Content ◽  
Signaling Pathway ◽  
Negative Regulator ◽  
Skeletal Muscle Atrophy ◽  
C2c12 Myotubes ◽  
Gene Expressions ◽  
E3 Ligases ◽  
Gene And Protein Expression ◽  
Mtorc1 Signaling

Muscle-specific ubiquitin E3 ligases, Atrogin-1 and MuRF1, are highly expressed in multiple conditions of skeletal muscle atrophy. The PI3K/Akt/FoxO signaling pathway is well known to regulate Atrogin-1 and MuRF1 gene expressions. Evidence supporting this is largely based on stimuli by insulin and IGF-1, that activate anabolic signaling, including Akt and Akt-dependent transcription factors. However, Akt activation also activates the mammalian target of rapamycin complex 1 (mTORC1) which induces skeletal muscle hypertrophy. However, whether mTORC1-dependent signaling has a role in regulating Atrogin-1 and/or MuRF1 gene and protein expression is currently unclear. In this study, we confirmed that activation of insulin-mediated Akt signaling suppresses both Atrogin-1 and MuRF1 protein content and that inhibition of Akt increases both Atrogin-1 and MuRF1 protein content in C2C12 myotubes. Interestingly, inhibition of mTORC1 using a specific mTORC1 inhibitor, rapamycin, increased Atrogin-1, but not MuRF1, protein content. Furthermore, activation of AMP-activated protein kinase (AMPK), a negative regulator of the mTORC1 signaling pathway, also showed distinct time-dependent changes between Atrogin-1 and MuRF1 protein content, suggesting differential regulatory mechanisms between Atrogin-1 and MuRF1 protein content. To further explore the downstream of mTORC1 signaling, we employed a specific S6K1 inhibitor, PF-4708671, and found that Atrogin-1 protein content was dose-dependently increased with PF-4708671 treatment, whereas MuRF1 protein content was not significantly altered. Overall, our results indicate that Atrogin-1 and MuRF1 protein contents are regulated by different mechanisms, the downstream of Akt, and that Atrogin-1 protein content can be regulated by rapamycin-sensitive mTOR-S6K1 dependent signaling pathway.

scholarly journals Neurogranin is expressed in mammalian skeletal muscle and inhibits calcineurin signaling and myoblast fusion

2019 ◽  
Vol 317 (5) ◽  
pp. C1025-C1033 ◽  
Author(s):  
Val A. Fajardo ◽  
Colton J. F. Watson ◽  
Kirsten N. Bott ◽  
Fereshteh Moradi ◽  
Lucas A. Maddalena ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Myogenic Differentiation ◽  
Vastus Lateralis ◽  
Critical Role ◽  
Myoblast Fusion ◽  
C2c12 Cells ◽  
C2c12 Myotubes ◽  
Mammalian Skeletal Muscle ◽  
Mrna Levels ◽  
Calcineurin Signaling

Calcineurin is a Ca2+/calmodulin (CaM)-dependent phosphatase that plays a critical role in promoting the slow fiber phenotype and myoblast fusion in skeletal muscle, thereby making calcineurin an attractive cellular target for enhancing fatigue resistance, muscle metabolism, and muscle repair. Neurogranin (Ng) is a CaM-binding protein thought to be expressed solely in brain and neurons, where it inhibits calcineurin signaling by sequestering CaM, thus lowering its cellular availability. Here, we demonstrate for the first time the expression of Ng protein and mRNA in mammalian skeletal muscle. Both protein and mRNA levels are greater in slow-oxidative compared with fast-glycolytic muscles. Coimmunoprecipitation of CaM with Ng in homogenates of C2C12 myotubes, mouse soleus, and human vastus lateralis suggests that these proteins physically interact. To determine whether Ng inhibits calcineurin signaling in muscle, we used Ng siRNA with C2C12 myotubes to reduce Ng protein levels by 60%. As a result of reduced Ng expression, C2C12 myotubes had enhanced CaM-calcineurin binding and calcineurin signaling as indicated by reduced phosphorylation of nuclear factor of activated T cells and increased utrophin mRNA. In addition, calcineurin signaling affects the expression of myogenin and stabilin-2, which are involved in myogenic differentiation and myoblast fusion, respectively. Here, we found that both myogenin and stabilin-2 were significantly elevated by Ng siRNA in C2C12 cells, concomitantly with an increased fusion index. Taken together, these results demonstrate the expression of Ng in mammalian skeletal muscle where it appears to be a novel regulator of calcineurin signaling.

C2C12 cells: biophysical, biochemical, and immunocytochemical properties

1994 ◽  
Vol 266 (6) ◽  
pp. C1795-C1802 ◽  
Author(s):  
D. K. McMahon ◽  
P. A. Anderson ◽  
R. Nassar ◽  
J. B. Bunting ◽  
Z. Saba ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Troponin ◽  
Troponin T ◽  
Protein Isoforms ◽  
C2c12 Cells ◽  
Contractile Protein ◽  
Hill Coefficient ◽  
C2c12 Myotubes ◽  
Cardiac Troponin T ◽  
Biophysical Properties

We examined the myofibril biochemical, structural, and biophysical properties of C2C12, a mouse skeletal muscle cell line (American Type Culture Collection), to assess whether force development and the sensitivity of the myofilaments to calcium could be measured in C2C12 myotubes and whether a cardiac contractile protein, troponin T, is expressed and incorporated into C2C12 myofibrils. When myoblasts fused and differentiated into myotubes, expression of myofilament proteins was initiated. Multiple cardiac and skeletal muscle troponin T isoforms were coexpressed. Cardiac troponin T expression increased and then decreased with time. Fluorescence immunocytochemistry demonstrated incorporation of cardiac troponin T isoforms into the myofibrils. At the time of the biophysical studies, mean myotube diameter was 12 microns (range 5-25 microns), and mean length was 290 microns (range 130-520 microns). The estimated maximum force developed by chemically skinned myotubes at 6-7 days poststarvation, 0.88 +/- 0.12 microN (mean +/- 95% confidence interval, n = 5), was significantly less (P < 0.05) than that at 10-13 days poststarvation, 1.12 +/- 0.12 microN (n = 7). The force-pCa relation yielded a Hill coefficient of 2.9 +/- 0.6 (n = 7) and half-maximal activation at pCa of 5.77 +/- 0.20. The demonstration that the biophysical properties of C2C12 cells can be measured and that cardiac and skeletal muscle troponin T isoforms are incorporated and colocalized into myofibrils suggest that these cells could be a useful model to assess the effects of exogenous native and mutated cardiac and skeletal contractile protein isoforms on myofilament function.

Sign in / Sign up

Export Citation Format

Share Document