Adaptation to hypoxia in Drosophila melanogaster requires autophagy.

ABSTRACT

Macroautophagy/autophagy, a mechanism of degradation of intracellular material required to sustain cellular homeostasis, is exacerbated under stress conditions like nutrient deprivation, protein aggregation, organelle senescence, pathogen invasion, and hypoxia, among others. Detailed in vivo description of autophagic responses triggered by hypoxia is limited. We have characterized the autophagic response induced by hypoxia in Drosophila melanogaster. We found that this process is essential for Drosophila adaptation and survival because larvae with impaired autophagy are hypersensitive to low oxygen levels. Hypoxia triggers a bona fide autophagic response, as evaluated by several autophagy markers including Atg8, LysoTracker, Lamp1, Pi3K59F/Vps34 activity, transcriptional induction of Atg genes, as well as by transmission electron microscopy. Autophagy occurs in waves of autophagosome formation and maturation as hypoxia exposure is prolonged. Hypoxia-triggered autophagy is induced cell autonomously, and different tissues are sensitive to hypoxic treatments. We found that hypoxia-induced autophagy depends on the basic autophagy machinery but not on the hypoxia master regulator sima/HIF1A. Overall, our studies lay the foundation for using D. melanogaster as a model system for studying autophagy under hypoxic conditions, which, in combination with the potency of genetic manipulations available in this organism, provides a platform for studying the involvement of autophagy in hypoxia-associated pathologies and developmentally regulated processes.Abbreviations Atg autophagy-related; FYVE zinc finger domain from Fab1 (yeast ortholog of PIKfyve); GFP green fluorescent protein; HIF hypoxia-inducible factor; hsf heat shock factor; Hx hypoxia; mCh mCherry; PtdIns phosphatidylinositol; PtdIns3P phosphatidylinositol-3-phosphate; Rheb Ras homolog enriched in brain; sima similar; Stv Starvation; TEM transmission electron microscopy; Tor target of rapamycin; UAS upstream activating sequence; Vps vacuolar protein sorting.