Figure 6. Pharmacological inhibition of autophagy leads to a caspase-dependent cell death.

(a) Immunoblotting. Jurkat T cells overexpressing ATG5 or control cells were cultured in the presence and absence of 3-MA for 48 h. 3-MA blocked the formation of LC3-II and p62 degradation, indicating that it indeed inhibited ATG5-induced autophagy. Results are representative of three independent experiments. (b) Cell cycle analysis. Normal Jurkat T cells and cells overexpressing ATG5 were cultured for 48 h in the presence and absence of 3-MA. Induction of G2- or M-phase arrest was seen as a consequence of ATG5 overexpression independent of treatment with 3-MA, as normal Jurkat T cells exhibited no G2/M arrest following 3-MA treatment. Representative flow cytometry diagrams are shown (n=3). Moreover, induction of autophagy by Beclin 1 overexpression or starvation failed to produce cell cycle arrest (Supplementary Fig. S4). (c) Morphological analysis. Normal Jurkat T cells and cells overexpressing ATG5 were cultured for 48 h in the presence and absence of 3-MA and analysed. Representative examples of morphology are shown (n=3); large multinucleated cells and cells with abnormal nuclei were seen as a consequence of ATG5 overexpression independent of 3-MA. Neither induction of autophagy by Beclin 1 overexpression nor starvation resulted in such abnormal cells (Supplementary Fig. S4). Scale bar, 10 μm. (d) Viability assays. Jurkat T cells either overexpressing ATG5 following lentiviral gene transfer or treated with etoposide were cultured in the presence and absence of the indicated pharmacological inhibitors for the indicated times to block autophagy and caspase activity. All values are means±s.d. (n=3).