Figure 4.

mTOR in TNF-induced insulin resistance. (A) Myotubes were incubated with medium or 200 nM rapamycin for 1 h before treatment with insulin (5 min), TNF (1 h), or TNF and then insulin. After immunoprecipitation (IP) of IRS-1 from cell lysates a Western blot was probed with antiphosphotyrosine (Upper) and then with anti-IRS-1 (Lower). (B) Serum-starved myotubes were incubated in the absence or presence of 10 nM TNF for 1 h before immunoprecipitation of either IRS-1 (Upper) or mTOR (Lower). A Western blot of proteins fractionated from each immunopreciptate then was hybridized with the reciprocal antibody.