Characterization of the autophagic response to hypoxia in Drosophila melanogaster

AYELÉN VALKO; MARIANA MELANI; WAPPNER, PABLO

Conferencia; Buenos Aires Research Conference on Autophagy; 2017

Autophagy is induced in response to stressful conditions, including starvation and infections. In mammalian cultured cells, plants and worms autophagy can also be triggered in response to low oxygen levels, playing an essential adaptive role under this condition. We have studied hypoxia-induced autophagy in Drosophila melanogaster, a model organism that can survive at extremely low oxygen levels for days. We found that autophagy is induced in fat body cells of hypoxic 3rd instar larvae, as assayed by ATG8 nucleation. Also, we detected increased GFP-Lamp and GFP-2xFYVE signal, indicative of increased lysosomes and augmented Vps34 activity respectively. We used the GFP-mCherry-Atg8 reporter to analyze autophagic flux under hypoxic conditions, in comparison to starvation-induced autophagy. We observed that autophagosomes form already at 2 hours of hypoxia; at 6 hours immature autophagosomes and acidic autolysosomes co-exist in the cells, and by 12 hours, the majority of ATG8-positive foci are acidic. Noteworthy, we observed that hypoxia-induced autophagy was blocked in atg1 or sima mutant larvae and that starvation-induced autophagy is sima-independent. Finally, atg1 and atg3 mutant larvae fail to develop in a hypoxic environment, suggesting that autophagy is a mechanism required for physiologic adaptation to hypoxia. Altogether, these results show that hypoxic stress can induce a bona fide autophagic response in D. melanogaster comparable to that induced by starvation, being this mechanism an adaptive response to hypoxia.