FIGURE 5.

Zfat deficiency enhances PI3K-dependent activation of Akt and nuclear exclusion of FoxO1. A–D, immunoblot analysis of the indicated proteins on splenic CD4⁺ T cells from Zfat^f/f and Zfat^f/f-CD4Cre mice. CD4⁺ T cells were harvested immediately (A and B) or after incubation with 10 μm LY294002 or vehicle (DMSO) for 20 min (C and D). The cells were lysed (A–C) or fractionated into nuclear (Nu)/cytoplasmic (Cy) fractions (D) and then subjected to immunoblotting with the specific antibodies. Actin was used as a loading control. Levels of FoxO1 protein expression were quantified by densitometry. Values below the panel in D represent the proportion of FoxO1 protein residing in each fraction. Data are representative of two or three independent experiments. E, model of the enhanced lysosomal degradation of FoxO1 in Zfat-deficient T cells. Zfat deficiency causes Akt activation, leading to the nuclear exclusion of FoxO1, after which the cytoplasmic FoxO1 is degraded by lysosomal proteases through autophagy, which is up-regulated by Zfat deficiency.