Figure 3. Myc increases autophagic flux.

(A) Practically no mCherry-GFP-Atg8a dots are seen in control fat body cells of well-fed larvae. (B) Dots positive for both mCherry and GFP appear in control cells upon feeding larvae chloroquine, a drug that blocks lysosomal degradation. (C) Overexpression of Myc results in the formation of puncta that are mostly mCherry-positive. (D) Chloroquine treatment strongly increases the number of mCherry punctae in Myc overexpressing cells. Note that dots are now positive for GFP as well. (A′–D′) Fluorescent intensity and colocalization profiles of mCherry and GFP channels from panels A–D. Pearson correlation coefficients shown in A′–D′ indicate that the correlation of the mCherry and GFP pixel intensity is low in panel C but high in panels A, B, and D. (E) Quantification of data in panels A–D, n = 15–30 per genotype/treatment. Myc expression in fat body cells strongly induces mCherry puncta formation compared to control cells. Chloroquine treatment increases dot numbers both in control and Myc overexpressing cells. (F) Autophagic degradation-dependent conversion of mCherry-GFP-Atg8a to free mCherry is increased by overexpression of Myc in fat body cells. Numbers indicate the level of free mCherry relative to the loading control Tubulin in different genotypes, as determined by densitometric evaluation. Scalebars in A–D equal 20 µm. Statistically significant differences are indicated, ** p<0.01.