Abstract
Differentiation, maturation, and repair of skeletal muscle requires ongoing cooperation between signaling cascades activated by hormones and growth factors, and intrinsic regulatory programs controlled by myogenic transcription factors. The insulin-like growth factor - phosphatidylinositol-3 kinase - Akt pathway has been implicated in muscle growth and regeneration after injury, in counteracting sarcopenia during aging, and in maintaining muscle cell viability. Here we present evidence for distinct roles for Akt1 and Akt2 in different phases of muscle differentiation. Targeted knockdown of either Akt had no effect on C2 myoblast proliferation, even though Akt1 concentrations are markedly higher than Akt2 levels under growth-promoting conditions. Akt2 concentrations rose by nearly an order of magnitude during muscle differentiation, while Akt1 levels remained constant, yet loss of either protein did not increase myoblast death. Rather, knockdown or genetic knockout of Akt1 blocked differentiation at its earliest stages, preventing induction of muscle-specific proteins and inhibiting formation of multinucleated myofibers, while myoblasts lacking Akt2 differentiated normally, although resultant myofibers were thinner and incorporated fewer nuclei than controls. Forced expression of knockdown-resistant Akt1 partially reversed the deficit in differentiation seen in myoblasts lacking Akt1. Our results define isoform-specific Akt actions in muscle cells, and demonstrate that both Akts are necessary for full myoblast differentiation and maturation.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 503-511 |
| Number of pages | 9 |
| Journal | Journal of Cellular Physiology |
| Volume | 219 |
| Issue number | 2 |
| DOIs | |
| State | Published - May 2009 |
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ASJC Scopus subject areas
- Clinical Biochemistry
- Cell Biology
- Physiology
Cite this
Distinct actions of Akt1 and Akt2 in skeletal muscle differentiation. / Rotwein, Peter; Wilson, Elizabeth M.
In: Journal of Cellular Physiology, Vol. 219, No. 2, 05.2009, p. 503-511.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Distinct actions of Akt1 and Akt2 in skeletal muscle differentiation
AU - Rotwein, Peter
AU - Wilson, Elizabeth M.
PY - 2009/5
Y1 - 2009/5
N2 - Differentiation, maturation, and repair of skeletal muscle requires ongoing cooperation between signaling cascades activated by hormones and growth factors, and intrinsic regulatory programs controlled by myogenic transcription factors. The insulin-like growth factor - phosphatidylinositol-3 kinase - Akt pathway has been implicated in muscle growth and regeneration after injury, in counteracting sarcopenia during aging, and in maintaining muscle cell viability. Here we present evidence for distinct roles for Akt1 and Akt2 in different phases of muscle differentiation. Targeted knockdown of either Akt had no effect on C2 myoblast proliferation, even though Akt1 concentrations are markedly higher than Akt2 levels under growth-promoting conditions. Akt2 concentrations rose by nearly an order of magnitude during muscle differentiation, while Akt1 levels remained constant, yet loss of either protein did not increase myoblast death. Rather, knockdown or genetic knockout of Akt1 blocked differentiation at its earliest stages, preventing induction of muscle-specific proteins and inhibiting formation of multinucleated myofibers, while myoblasts lacking Akt2 differentiated normally, although resultant myofibers were thinner and incorporated fewer nuclei than controls. Forced expression of knockdown-resistant Akt1 partially reversed the deficit in differentiation seen in myoblasts lacking Akt1. Our results define isoform-specific Akt actions in muscle cells, and demonstrate that both Akts are necessary for full myoblast differentiation and maturation.
AB - Differentiation, maturation, and repair of skeletal muscle requires ongoing cooperation between signaling cascades activated by hormones and growth factors, and intrinsic regulatory programs controlled by myogenic transcription factors. The insulin-like growth factor - phosphatidylinositol-3 kinase - Akt pathway has been implicated in muscle growth and regeneration after injury, in counteracting sarcopenia during aging, and in maintaining muscle cell viability. Here we present evidence for distinct roles for Akt1 and Akt2 in different phases of muscle differentiation. Targeted knockdown of either Akt had no effect on C2 myoblast proliferation, even though Akt1 concentrations are markedly higher than Akt2 levels under growth-promoting conditions. Akt2 concentrations rose by nearly an order of magnitude during muscle differentiation, while Akt1 levels remained constant, yet loss of either protein did not increase myoblast death. Rather, knockdown or genetic knockout of Akt1 blocked differentiation at its earliest stages, preventing induction of muscle-specific proteins and inhibiting formation of multinucleated myofibers, while myoblasts lacking Akt2 differentiated normally, although resultant myofibers were thinner and incorporated fewer nuclei than controls. Forced expression of knockdown-resistant Akt1 partially reversed the deficit in differentiation seen in myoblasts lacking Akt1. Our results define isoform-specific Akt actions in muscle cells, and demonstrate that both Akts are necessary for full myoblast differentiation and maturation.
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U2 - 10.1002/jcp.21692
DO - 10.1002/jcp.21692
M3 - Article
VL - 219
SP - 503
EP - 511
JO - Journal of Cellular Physiology
JF - Journal of Cellular Physiology
SN - 0021-9541
IS - 2
ER -