Mechanical stretch activates signaling events for protein translation initiation and elongation in C2C12 myoblasts.
It has been proposed that mechanically induced tension is the critical factor in the induction of muscle hypertrophy. However, the molecular mechanisms involved in this process are still under investigation. In the present study, the effect of mechanical stretch on intracellular signaling for protein translation initiation and elongation was studied in C2C12 myoblasts. Cells were grown on a silicone elastomer chamber and subjected to 30-min of 5 or 15% constant static or cyclic (60 cycles/min) uniaxial stretch. Western blot analyses revealed that p70 S6 kinase (p70S6K) and eukaryotic elongation factor 2 (eEF2), which are the markers for translation initiation and peptide chain elongation, respectively, were activated by both static and cyclic stretch. The magnitude of activation was greater in response to the 15% cyclic stretch. Cyclic stretch also increased the phosphorylation of MAP kinases (p38 MAPK, ERK1/2 and JNK). However, the pharmacological inhibition of MAP kinases did not block the stretch-induced activation of p70S6K and eEF2. An inhibitor of the mammalian target of rapamycin (mTOR) blocked the stretch-induced phosphorylation of p70S6K but did not affect the eEF2 activation. A broad-range tyrosine kinase inhibitor, genistein, blocked the stretch-induced activation of p70S6K and eEF2, whereas Src tyrosine kinase and Janus kinase (JAK) inhibitors did not. These results suggest that the stretch-induced activation of protein translation initiation and elongation in mouse myoblast cell lines is mediated by tyrosine kinase(s), except for Src kinase or JAK.
Section of Applied Physiology, Department of Health and Sports Sciences, Graduate School of Medicine, Osaka University, Osaka 560-0043, Japan. nakai@hss.osaka-u.ac.jp
Naoya
N
Nakai
Fuminori
F
Kawano
Yoshihiko
Y
Oke
Sachiko
S
Nomura
Takashi
T
Ohira
Ryo
R
Fujita
Yoshinobu
Y
Ohira
D000818:Animals; D002460:Cell Line; D054736:Elongation Factor 2 Kinase / Q000378:metabolism*; D019833:Genistein / Q000037:antagonists & inhibitors; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D032446:Myoblasts / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D012026:Reflex, Stretch; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D020123:Sirolimus / Q000037:antagonists & inhibitors; D013314:Stress, Mechanical; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
D019833:Genistein; D011505:Protein-Tyrosine Kinases; D019061:src-Family Kinases; D017346:Protein Serine-Threonine Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; C517690:Eef2k protein, mouse; D054736:Elongation Factor 2 Kinase; D019950:Mitogen-Activated Protein Kinase 1; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020123:Sirolimus