Control of Ser2448 phosphorylation in the mammalian target of rapamycin by insulin and skeletal muscle load

Thomas H. Reynolds IV, Sue C. Bodine, John C. Lawrence

Research output: Contribution to journalArticle

195 Citations (Scopus)

Abstract

We have investigated the effects of insulin, amino acids, and the degree of muscle loading on the phosphorylation of Ser2448, a site in the mammalian target of rapamycin (mTOR) phosphorylated by protein kinase B (PKB) in vitro. Phosphorylation was assessed by immunoblotting with a phosphospecific antibody (anti-Ser(P)2448) and with mTAb1, an activating antibody whose binding is inhibited by phosphorylation in the region of mTOR that contains Ser2448. Incubating rat diaphragm muscles with insulin increased Ser2448 phosphorylation but did not change the total amount of mTOR. Insulin, but not amino acids, activated PKB, as evidenced by increased phosphorylation of both Ser308 and Thr473 in the kinase. Ser2448 phosphorylation was also modulated by muscle-loading. Overloading the rat plantaris muscle by synergist muscle ablation, which promotes hypertrophy of the plantaris muscle, increased Ser2448 phosphorylation. In contrast, unloading the gastrocnemius muscle by hindlimb suspension, which promotes atrophy of the muscle, decreased Ser2448 phosphorylation, an effect that was fully reversible. Neither overloading nor hindlimb suspension significantly changed the total amount of mTOR. In summary, our results demonstrate that atrophy and hypertrophy of skeletal muscle are associated with decreases and increases in Ser2448 phosphorylation, suggesting that modulation of this site may have an important role in the control of protein synthesis.

Original languageEnglish (US)
Pages (from-to)17657-17662
Number of pages6
JournalJournal of Biological Chemistry
Volume277
Issue number20
DOIs
StatePublished - May 17 2002
Externally publishedYes

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Phosphorylation
Sirolimus
Muscle
Skeletal Muscle
Insulin
Hindlimb Suspension
Muscles
Proto-Oncogene Proteins c-akt
Hypertrophy
Rats
Suspensions
TOR Serine-Threonine Kinases
Phospho-Specific Antibodies
Amino Acids
Muscular Atrophy
Diaphragms
Ablation
Diaphragm
Unloading
Immunoblotting

ASJC Scopus subject areas

  • Biochemistry

Cite this

Control of Ser2448 phosphorylation in the mammalian target of rapamycin by insulin and skeletal muscle load. / Reynolds IV, Thomas H.; Bodine, Sue C.; Lawrence, John C.

In: Journal of Biological Chemistry, Vol. 277, No. 20, 17.05.2002, p. 17657-17662.

Research output: Contribution to journalArticle

Reynolds IV, Thomas H. ; Bodine, Sue C. ; Lawrence, John C. / Control of Ser2448 phosphorylation in the mammalian target of rapamycin by insulin and skeletal muscle load. In: Journal of Biological Chemistry. 2002 ; Vol. 277, No. 20. pp. 17657-17662.
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