Chaperone-mediated Autophagy Targets Hypoxia-inducible Factor-1α (HIF-1α) for Lysosomal Degradation

Abstract

Hypoxia-inducible factor-1 (HIF-1) is a heterodimeric transcription factor that mediates adaptive responses to hypoxia. We demonstrate that lysosomal degradation of the HIF-1α subunit by chaperone-mediated autophagy (CMA) is a major regulator of HIF-1 activity. Pharmacological inhibitors of lysosomal degradation, such as bafilomycin and chloroquine, increased HIF-1α levels and HIF-1 activity, whereas activators of chaperone-mediated autophagy, including 6-aminonicotinamide and nutrient starvation, decreased HIF-1α levels and HIF-1 activity. In contrast, macroautophagy inhibitors did not increase HIF-1 activity. Transcription factor EB, a master regulator of lysosomal biogenesis, also negatively regulated HIF-1 activity. HIF-1α interacts with HSC70 and LAMP2A, which are core components of the CMA machinery. Overexpression of HSC70 or LAMP2A decreased HIF-1α protein levels, whereas knockdown had the opposite effect. Finally, hypoxia increased the transcription of genes involved in CMA and lysosomal biogenesis in cancer cells. Thus, pharmacological and genetic approaches identify CMA as a major regulator of HIF-1 activity and identify interplay between autophagy and the response to hypoxia.