Atg7-dependent autophagy promotes neuronal health, stress tolerance, and longevity but is dispensable for metamorphosis in Drosophila

Abstract

Autophagy, a cellular process of cytoplasmic degradation and recycling, is induced in Drosophila larval tissues during metamorphosis, potentially contributing to their destruction or reorganization. Unexpectedly, we find that flies lacking the core autophagy regulator Atg7 are viable, despite severe defects in autophagy. Although metamorphic cell death is perturbed in Atg7 mutants, the larval-adult midgut transition proceeds normally, with extended pupal development compensating for reduced autophagy. Atg7 −/− adults are short-lived, hypersensitive to nutrient and oxidative stress, and accumulate ubiquitin-positive aggregates in degenerating neurons. Thus, normal levels of autophagy are crucial for stress survival and continuous cellular renewal, but not metamorphosis.Supplemental material is available at http://www.genesdev.org.

Drosophila Rab2 controls endosome-lysosome fusion and LAMP delivery to late endosomes

“…S7B), suggesting that it is part of the normal life cycle of the Rab2 protein. The lumenal level of mCherry-Rab2 was strongly reduced in a Atg7 d77 null mutant background, in which macroautophagy is abolished [74] (Fig. S7C).…”

“…The αTub84B-Rab7.YFP strain [92] was a gift from Dr. Suzanne Eaton (Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany). The line carrying the cathD-mCherry transgene controlled by the endogenous cathD promoter [30] and the Atg7 d77 line [74] were a gift from Dr. Gábor Juhász (Eötvös Loránd University, Budapest, Hungary). pm-Cherry-GFP-Atg8a was a gift from Dr. Tor Erik Rusten (University of Oslo, Oslo, Norway).…”

The initiator caspase Dronc is subject of enhanced autophagy upon proteasome impairment in Drosophila

“…The autophagy gene Atg7 encodes the E1-activating enzyme for the two ubiquitin-like conjugation systems and is an important regulator for autophagy. 14,16 As proteasome impairment does not affect the protein levels of Dronc in epithelial disc cells, we tested the possibility that autophagy may control it. We downregulated Atg7 function by RNAi or inactivated Atg7 in mutant cell clones in eye imaginal discs.…”

“…Atg7 d14 is a mutant allele as described. 16 UAS-Atg7 RNAi targets Atg7 by RNAi. 17,75 UAS-Flag-dronc encodes a Dronc protein with an N-terminal Flag-tag.…”

“…14,15 Atg7 is an enzyme 1 (E1)-activating enzyme involved in both conjugation pathways 14 and essential for autophagy. 16 The incorporation of Atg8 fusion proteins (for example, with green fluorescent protein (GFP) and/or mCherry) into autophagosomes is often used as a marker for autophagosomes 17 and autophagic flux. 18 Although it was initially assumed that the UPS and autophagy are independent of each other, recent evidence has suggested that there is crosstalk and feedback between the two 1,[19][20][21][22][23][24][25][26][27] (reviewed by Park and Cuervo, 3 Wojcik 28 and Lamark and Johansen 29 ).…”