title: Autophagy-related gene 7 is downstream of heat shock protein 27 in the regulation of eye morphology, polyglutamine toxicity, and lifespan in Drosophila.
abstract: BACKGROUND
  Autophagy 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.
  
  
  METHODS
  The 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.
  
  
  RESULTS
  We 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.
  
  
  CONCLUSIONS
  We propose that Atg7 acts downstream of Hsp27 in the regulation of eye morphology, polyglutamine toxicity, and lifespan in Drosophila.
authors.affiliation: Institute of Biotechnology, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, HsinChu, 30013, Taiwan.
authors.forename: Shih-Fen
authors.initials: SF
authors.lastname: Chen
authors.forename: Ming-Lun
authors.initials: ML
authors.lastname: Kang
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Chen
authors.forename: Hong-Wen
authors.initials: HW
authors.lastname: Tang
authors.forename: Cheng-Wen
authors.initials: CW
authors.lastname: Huang
authors.forename: Wan-Hua
authors.initials: WH
authors.lastname: Li
authors.forename: Chun-Pu
authors.initials: CP
authors.lastname: Lin
authors.forename: Chao-Yung
authors.initials: CY
authors.lastname: Wang
authors.forename: Pei-Yu
authors.initials: PY
authors.lastname: Wang
authors.forename: Guang-Chao
authors.initials: GC
authors.lastname: Chen
authors.forename: Horng-Dar
authors.initials: HD
authors.lastname: Wang
mesh_terms: D000818:Animals; D001343:Autophagy / Q000235:genetics; D000071193:Autophagy-Related Protein 7; D004330:Drosophila / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004843:Epistasis, Genetic / Q000235:genetics; D005123:Eye / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D055551:HSP27 Heat-Shock Proteins / Q000235:genetics* / Q000502:physiology; D010455:Peptides / Q000633:toxicity; D034622:RNA Interference
chemical_list: C530193:Atg7 protein, Drosophila; D029721:Drosophila Proteins; D055551:HSP27 Heat-Shock Proteins; D010455:Peptides; C097188:polyglutamine; D000071193:Autophagy-Related Protein 7