Characterization of the autophagic response to hypoxia in Drosophila melanogaster

WAPPNER, PABLO; VALKO, A.; MELANI M.

Buenos Aires

Conferencia; Buenos Aires Research Conference Autophagy 2017 "Molecular Mechanisms in Biology and Diseases"; 2017

Facultad de Farmacia y Bioquímica, UBA

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 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 more lysosomes and augmented Vps34 activity respectively. We used the doubly tagged GFP-mCherry-Atg8 to analyze autophagic flux under hypoxic conditions, in comparison to starvation-induced autophagy. We observed autophagosomes forming as early as 2 hours of hypoxia. After 6 hours of hypoxia 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 larvae mutants for atg1 or sima, main hypoxic regulator. On the contrary, starvation-induced autophagy does not depend on sima. Finally, larvae mutants for atg1 or atg3 showed drastic lifespan reductions when they developed in a hypoxic environment. Altogether, these results show for the first time 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 which is dependent on sima and atg1.