Autophagy-related gene 7 is downstream of heat shock protein 27 in the regulation of eye morphology, polyglutamine toxicity, and lifespan in Drosophila

Shih-Fen Chen,Yi-Chun Chen,Horng-Dar Wang,Ming-Lun Kang,Chun-Pu Lin,Chao-Yung Wang,Guang-Chao Chen,Cheng-Wen Huang,Pei-Yu Wang,Wan-Hua Li,Hong-Wen Tang

doi:10.1186/1423-0127-19-52

Abstract

BackgroundAutophagy and molecular chaperones both regulate protein homeostasis and maintain important physiological functions. Atg7 (autophagy-related gene 7) and Hsp27 (heat shock protein 27) are involved in the regulation of neurodegeneration and aging. However, the genetic connection between Atg7 and Hsp27 is not known.MethodsThe appearances of the fly eyes from the different genetic interactions with or without polyglutamine toxicity were examined by light microscopy and scanning electronic microscopy. Immunofluorescence was used to check the effect of Atg7 and Hsp27 knockdown on the formation of autophagosomes. The lifespan of altered expression of Hsp27 or Atg7 and that of the combination of the two different gene expression were measured.ResultsWe used the Drosophila eye as a model system to examine the epistatic relationship between Hsp27 and Atg7. We found that both genes are involved in normal eye development, and that overexpression of Atg7 could eliminate the need for Hsp27 but Hsp27 could not rescue Atg7 deficient phenotypes. Using a polyglutamine toxicity assay (41Q) to model neurodegeneration, we showed that both Atg7 and Hsp27 can suppress weak, toxic effect by 41Q, and that overexpression of Atg7 improves the worsened mosaic eyes by the knockdown of Hsp27 under 41Q. We also showed that overexpression of Atg7 extends lifespan and the knockdown of Atg7 or Hsp27 by RNAi reduces lifespan. RNAi-knockdown of Atg7 expression can block the extended lifespan phenotype by Hsp27 overexpression, and overexpression of Atg7 can extend lifespan even under Hsp27 knockdown by RNAi.ConclusionsWe propose that Atg7 acts downstream of Hsp27 in the regulation of eye morphology, polyglutamine toxicity, and lifespan in Drosophila.

Highlights

Autophagy and molecular chaperones both regulate protein homeostasis and maintain important physiological functions
Autophagy-related gene 7 is downstream of heat shock protein 27 in the regulation of Drosophila eye phenotype Protein homeostasis plays an important role in lifespan and stress response [1, 2]
We examined the effects of altering Heat shock protein 27 (Hsp27) and Autophagy-related gene 7 (Atg7) expression in the Drosophila eye using the GMR-Gal4 driver followed by the analyses of eye morphology utilizing scanning electron microscopy and light microscopy

Summary

Introduction

Autophagy and molecular chaperones both regulate protein homeostasis and maintain important physiological functions. Atg (autophagy-related gene 7) and Hsp (heat shock protein 27) are involved in the regulation of neurodegeneration and aging. Protein homeostasis is important in maintaining physiological function to protect against cellular degeneration [4]. Autophagy and molecular chaperones are two defensive systems utilized to uphold cellular protein quality and homeostasis [5, 6]. Autophagy participates in many physiological functions including aging and neurodegeneration [8, 9], and mounting evidence demonstrates that autophagy participates in the regulation of lifespan in different species [10,11,12]. In Drosophila, Atg7-null mutants are short-lived and hypersensitive to starvation and oxidative stress [17], and the neuronal overexpression of Atg8a regulates lifespan and tolerance to oxidative stress [18]. Suppression of basal autophagy in the central nervous system causes neurodegeneration in Atg conditional knockout mice [19, 22]

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Results

Conclusion