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Phosphorylation of S6K1 at Thr389 following resistance exercise does not require the PIF‐pocket of PDK1
Author(s) -
Baar Keith,
Alessi Dario,
Hickman Jonathan
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.lb33
Subject(s) - phosphorylation , p70 s6 kinase 1 , resistance training , medicine , chemistry , biochemistry , protein kinase b
The PIF binding domain of the phosphoinositol‐dependent protein kinase (PDK1) is required for insulin‐stimulated S6K phosphorylation on threonine 389 and activation of the kinase. Since S6K1 may play a role in the development of skeletal muscle hypertrophy, we hypothesized that PDK1‐PIF knockin mice would be unable to undergo skeletal muscle hypertrophy. To test this hypothesis, the gastrocnemius muscle of control and knockin mice was removed for 7 days of overload. Both the control and PDK1‐PIF knockin mice plantaris (PLN) muscle hypertrophied normally (wt=26.6±2.6%; PDK1‐PIF=28.8±2.95%). Since the hypertrophy response was unaltered, we determined the activation of S6K1. Both the phosphorylation of S6K1 and its downstream target rS6 were normal in the overloaded PLN. To test the possibility that new cells, lacking the knockin mutation, had been recruited to the muscle to permit hypertrophy and the phosphorylation of S6K1, we acutely stimulated control and PDK1‐PIF mice and determined the phosphorylation of S6K1 and rS6 30 minutes following the completion of resistance exercise. Once again, the phosphorylation of S6K1 and rS6 was similar between the control and PDK1‐PIF knockin mice. These data suggest that, unlike insulin treatment, resistance exercise results in non‐PDK1 dependent phosphorylation of S6K1.