Activation of mTOR by release of extracellular cholesterol stores controls the transition from quiescence to growth in C. elegans
Recovery from the quiescent developmental stage called dauer is an essential process in C. elegans and provides an excellent model to understand how metabolic transitions contribute to developmental plasticity. We here show that the depletion of sterol-binding proteins SCL-12 and SCL-13 is the key change in the C. elegans proteome in early dauer recovery. This process releases a cholesterol store that is sequestered in the gut lumen during the dauer state to facilitate the transition into reproductive development. First, the stored cholesterol undergoes endocytosis into the lysosomes of the intestinal cells, where it activates mTOR to promote protein synthesis and growth. Second, it is used for the production of dafachronic acids that switch metabolic programs at the transcriptional level. These processes are essential for population fitness and survival, as loss of SCL-12 and SCL-13, depletion of sterols, and loss of mTOR precludes quiescence exit, ultimately leading to the expiration of the entire population.