Fig. 8.

Activation of the IRE1α-XBP1 pathway by the prolonged exposure to insulin can be saturated by the mTOR inhibitor rapamycin. Hepa1c1c7 cells were treated with insulin (10 nm) in the presence or absence of rapamycin (5 and 20 nm) for 12 h and then lysed in Triton X-100 buffer. Levels of phospho-/total-S6K (A), phospho-IRE1α (B), and nuclear XBP1 (C) were evaluated by immunoblotting with specific antibodies as noted. Results represent mean ± sem of three independent experiments. An arrow indicates target band.