Figure 6.—

Two alternative models for how autophagy affects cell growth in C. elegans. (A) If autophagy genes mediate the effect of both insulin/IGF-1 and TGF-β signaling to control cell growth, i.e., insulin/IGF-1 and TGF-β signaling converge on autophagy to regulate cell size, unc-51 and bec-1 should function downstream of these two hormonal systems. (B) Because mutations in bec-1 and unc-51 do not completely suppress the Lon phenotype of daf-2 and certain TGF-β mutant strains, it is also possible that autophagy genes act in parallel to insulin/IGF-1 and TGF-β signaling in cell growth control. The question marks indicate whether the effect of the insulin/IGF-1 signaling pathway on body size is solely the result of changes in autophagy. Arrows indicate positive regulatory interactions, bars represent inhibitions. DAF-2, IGF-1 receptor; AGE-1, phosphatidylinositol-3-OH kinase; DAF-16, FOXO forkhead transcription factor; SMA-6, type I TGF-β receptor; DBL-1, TGF-β ligand for SMA-6; LON-1, cytoplasmic transducer of TGF-β signaling.