Figure 4. Defective autophagy impaired long-lived protein degradation. (A) Atg5 WT and KO MEFs were labeled with AHA and then treated with starvation or MTOR inhibitors for 3 h, as described in Figure 2A. Data for the relative signal intensity were expressed as the ratio of treated cells to control cells, as mean ± SD from 3 independent experiments, *P < 0.05, the Student t test. (B) Atg5 WT and KO MEFs were treated as described in (A), harvested and proteins from cell lysates were analyzed by western blot. ACTB served as the loading control.