Abstract
The PI3K/Akt/mTOR signaling pathway is critical for cellular growth and survival in skeletal muscle, and is activated in response to growth factors such as insulin-like growth factor-I (IGF-I). We found that in C2C12 myoblasts, deficiency of PI3K p110 catalytic subunits or Akt isoforms had distinct effects on phosphorylation of mTOR and p70S6K. siRNA-mediated knockdown of PI3K p110α, p110β, and simultaneous knockdown of p110α and p110β resulted in increased basal and IGF-I-stimulated phosphorylation of mTOR S2448 and p70S6K T389; however, phosphorylation of S6 was reduced in p110β-deficient cells, possibly due to reductions in total S6 protein. We found that IGF-I-stimulated Akt1 activity was enhanced in Akt2- or Akt3-deficient cells, and that knockdown of individual Akt isoforms increased mTOR/p70S6K activation in an isoform-specific fashion. Conversely, levels of IGF-I-stimulated p70S6K phosphorylation in cells simultaneously deficient in both Akt1 and Akt3 were increased beyond those seen with loss of any single Akt isoform, suggesting an alternate, Akt-independent mechanism that activates mTOR/p70S6K. Our results collectively suggest that mTOR/p70S6K is activated in a PI3K/Akt-dependent manner, but that in the absence of p110α or Akt, alternate pathway(s) may mediate activation of mTOR/p70S6K in C2C12 myoblasts.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 252-257 |
| Number of pages | 6 |
| Journal | Biochemical and Biophysical Research Communications |
| Volume | 390 |
| Issue number | 2 |
| DOIs | |
| State | Published - Dec 11 2009 |
Fingerprint
Keywords
- Akt
- mTOR
- Myoblast
- PI3K
- S6K
ASJC Scopus subject areas
- Biochemistry
- Biophysics
- Cell Biology
- Molecular Biology
Cite this
Effects of PI3K catalytic subunit and Akt isoform deficiency on mTOR and p70S6K activation in myoblasts. / Matheny, Ronald W.; Adamo, Martin L.
In: Biochemical and Biophysical Research Communications, Vol. 390, No. 2, 11.12.2009, p. 252-257.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Effects of PI3K catalytic subunit and Akt isoform deficiency on mTOR and p70S6K activation in myoblasts
AU - Matheny, Ronald W.
AU - Adamo, Martin L
PY - 2009/12/11
Y1 - 2009/12/11
N2 - The PI3K/Akt/mTOR signaling pathway is critical for cellular growth and survival in skeletal muscle, and is activated in response to growth factors such as insulin-like growth factor-I (IGF-I). We found that in C2C12 myoblasts, deficiency of PI3K p110 catalytic subunits or Akt isoforms had distinct effects on phosphorylation of mTOR and p70S6K. siRNA-mediated knockdown of PI3K p110α, p110β, and simultaneous knockdown of p110α and p110β resulted in increased basal and IGF-I-stimulated phosphorylation of mTOR S2448 and p70S6K T389; however, phosphorylation of S6 was reduced in p110β-deficient cells, possibly due to reductions in total S6 protein. We found that IGF-I-stimulated Akt1 activity was enhanced in Akt2- or Akt3-deficient cells, and that knockdown of individual Akt isoforms increased mTOR/p70S6K activation in an isoform-specific fashion. Conversely, levels of IGF-I-stimulated p70S6K phosphorylation in cells simultaneously deficient in both Akt1 and Akt3 were increased beyond those seen with loss of any single Akt isoform, suggesting an alternate, Akt-independent mechanism that activates mTOR/p70S6K. Our results collectively suggest that mTOR/p70S6K is activated in a PI3K/Akt-dependent manner, but that in the absence of p110α or Akt, alternate pathway(s) may mediate activation of mTOR/p70S6K in C2C12 myoblasts.
AB - The PI3K/Akt/mTOR signaling pathway is critical for cellular growth and survival in skeletal muscle, and is activated in response to growth factors such as insulin-like growth factor-I (IGF-I). We found that in C2C12 myoblasts, deficiency of PI3K p110 catalytic subunits or Akt isoforms had distinct effects on phosphorylation of mTOR and p70S6K. siRNA-mediated knockdown of PI3K p110α, p110β, and simultaneous knockdown of p110α and p110β resulted in increased basal and IGF-I-stimulated phosphorylation of mTOR S2448 and p70S6K T389; however, phosphorylation of S6 was reduced in p110β-deficient cells, possibly due to reductions in total S6 protein. We found that IGF-I-stimulated Akt1 activity was enhanced in Akt2- or Akt3-deficient cells, and that knockdown of individual Akt isoforms increased mTOR/p70S6K activation in an isoform-specific fashion. Conversely, levels of IGF-I-stimulated p70S6K phosphorylation in cells simultaneously deficient in both Akt1 and Akt3 were increased beyond those seen with loss of any single Akt isoform, suggesting an alternate, Akt-independent mechanism that activates mTOR/p70S6K. Our results collectively suggest that mTOR/p70S6K is activated in a PI3K/Akt-dependent manner, but that in the absence of p110α or Akt, alternate pathway(s) may mediate activation of mTOR/p70S6K in C2C12 myoblasts.
KW - Akt
KW - mTOR
KW - Myoblast
KW - PI3K
KW - S6K
UR - http://www.scopus.com/inward/record.url?scp=70350135233&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=70350135233&partnerID=8YFLogxK
U2 - 10.1016/j.bbrc.2009.09.100
DO - 10.1016/j.bbrc.2009.09.100
M3 - Article
VL - 390
SP - 252
EP - 257
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
SN - 0006-291X
IS - 2
ER -