Fig. 4: Procaspase 9 can be degraded by the autophagy mediated by LC3.

a, b MDA-MB-453 cells were treated with rapamycin at 0, 0.2, 0.5, or 1.0 μM for 24 h. Protein levels were analyzed by immunoblotting (a), and procaspase 9 or procaspase 3 or procaspase 7 was quantified by densitometry (normalized to β-actin) with two independent biological replicates (b). c, d COS7 cells were starved in HBSS with or without 10 nM of Baf A1 for 0, 1, 2, or 4 h. Treatment with 20 μM of etoposide for 24 h was served as a control for caspase activation. Protein levels were analyzed by immunoblotting (c), quantified by densitometry (normalized to β-actin) with three independent biological replicates and are shown as mean ± standard deviation, one-way ANOVA (d). e, f Atg5^+/+ and Atg5^−/− MEF cells were transfected with Myc-procaspase 9 and then treated with rapamycin at the indicated concentration (μM) for 24 h. The protein levels were detected by immunoblotting (e), quantified by densitometry (normalized to β-actin) with three independent biological replicates and are shown as mean ± standard deviation, one-way ANOVA (f). g MDA-MB-453 cells were treated with rapamycin at 0, 0.2, 0.5, or 1.0 μM for 24 h. Protein levels were analyzed by immunoblotting. h MDA-MB-453 cells were starved in HBSS for 0, 2, 4, or 6 h. Protein levels were analyzed by immunoblotting. The experiments (g, h) were repeated two times with similar results. i COS7 cells were starved in HBSS medium for 0 or 2 h, and then subjected to immunostaining and confocal microscopy. DNAs in nuclei were stained with DAPI. n = 30 images, Scale bar: 10 μm. The white rectangles indicate the enlarged areas. I: LC3-I, II: LC3-II. Source data for (a–h) are provided as a Source Data file.