Daf-9/daf-12 Regulates Transcription Factor HLH-30 In C. Elegans

is a physiological process that is involved in the engulfinent of a portion of the cytosol or organelles and the formation of autolysosome for degradation. To resist a variety of stress, such as starvation, infection, damage of organelles, autophagy will increased to maintain the cellular homeostasis. In Caenorhabditis elegans, transcription factor HLH-30 up-regulates the levels of genes related to autophagy and lysosomal to promote autophagy and activate lysosomal. Upon fasting, HLH-30 is translocated from the cytoplasm to the nucleus to regulate autophagy in response to starvation. DAF-12 nuclear receptor signal pathway is deeply involved in the regulation of lifespan, development and stress-resistance. In the presence of nutrients, DAF-9, a cytochrome P450, promotes the synthesis of Dafachronic acid (DA), which is the ligand of DAF-12. The combination of DAF-12 and DA regulates the development of C. elegans. In the absence of food, DAF-12 binds to DIN-1 in response to starvation. Because both DAF-12 and HLH-30 are involved in the resistance to starvation, we assume that the DAF-9/DAF-12 pathway can control the regulation of HLH-30. In this study, our results demonstrate that HLH-30 was regulated by DAF-9/DAF-12. In the presence of nutrients, the silence of daf-9 by RNAi promoted the translocation of HLH-30 from the cytoplasm to the nucleus and autophagy. The silence of daf-12 by RNAi also promoted the translocation of HLH-30 from the cytoplasm to the nucleus in well-fed worms. However, knockdown of din-1 did not affect the translocation of HLH-30 during starvation. These results indicated that the translocation of HLH-30 is suppressed by DAF-12/DA in well-fed worms, whereas DAF-12/DIN-1 dose not activate HLH-30. When DAF-9 or DAF-12 is inactivated, HLH-30 is translocated from cytoplasm to nucleus leading to the activation of autophagy. Although CeTOR regulated the translocation of HLH-30, the action was not related to the DAF-9/DAF-12 pathway. Finally, we found that the translocation of HLH-30 induced by knockdown of daf-9 was decreased after nuclear receptor gene nhr-49 was silenced. Our data also demonstrated that another nuclear receptor NHR-80 did not affect the activation of HLH-30 in worms subjected to daf-9 RNAi. In conclusion, our study demonstrates that the DAF-9/DAF-12 pathway regulates the activation of HLH-30 through nuclear receptor NHR-49.