Loss of ubiquitinated protein autophagy is compensated by persistent cnc/NFE2L2/Nrf2 antioxidant responses

Autophagy. 2022 Oct;18(10):2385-2396. doi: 10.1080/15548627.2022.2037852. Epub 2022 Feb 20.

Abstract

SQSTM1/p62-type selective macroautophagy/autophagy receptors cross-link poly-ubiquitinated cargo and autophagosomal LC3/Atg8 proteins to deliver them for lysosomal degradation. Consequently, loss of autophagy leads to accumulation of polyubiquitinated protein aggregates that are also frequently seen in various human diseases, but their physiological relevance is incompletely understood. Here, using a genetically non-redundant Drosophila model, we show that specific disruption of ubiquitinated protein autophagy and concomitant formation of polyubiquitinated aggregates has hardly any effect on bulk autophagy, proteasome activity and fly healthspan. We find that accumulation of ref(2)P/SQSTM1 due to a mutation that disrupts its binding to Atg8a results in the co-sequestering of Keap1 and thus activates the cnc/NFE2L2/Nrf2 antioxidant pathway. These mutant flies have increased tolerance to oxidative stress and reduced levels of aging-associated mitochondrial superoxide. Interestingly, ubiquitin overexpression in ref(2)P point mutants prevents the formation of large aggregates and restores the cargo recognition ability of ref(2)P, although it does not prevent the activation of antioxidant responses. Taken together, potential detrimental effects of impaired ubiquitinated protein autophagy are compensated by the aggregation-induced antioxidant response.Abbreviations: Atg8a: Autophagy-related 8a; cnc: cap-n-collar; IFM: indirect flight muscle; KEAP1: kelch like ECH associated protein 1; LIR: LC3-interacting region; NFE2L2/Nrf2: NFE2 like bZIP transcription factor 2; PB1: Phox and Bem1; ref(2)P: refractory to sigma P; SAR: selective autophagy receptor; UBA: ubiquitin-associated.

Keywords: Autophagic receptor; Drosophila; autophagy; longevity; oxidative stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antioxidants / pharmacology
  • Autophagy* / physiology
  • Autophagy-Related Protein 8 Family / metabolism
  • Carrier Proteins
  • Drosophila / metabolism
  • Humans
  • Kelch-Like ECH-Associated Protein 1 / genetics
  • Kelch-Like ECH-Associated Protein 1 / metabolism
  • NF-E2-Related Factor 2* / metabolism
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Aggregates
  • Sequestosome-1 Protein / metabolism
  • Superoxides / metabolism
  • Ubiquitin / metabolism
  • Ubiquitinated Proteins / metabolism

Substances

  • Antioxidants
  • Autophagy-Related Protein 8 Family
  • Carrier Proteins
  • Kelch-Like ECH-Associated Protein 1
  • NF-E2-Related Factor 2
  • NFE2L2 protein, human
  • Protein Aggregates
  • Sequestosome-1 Protein
  • Ubiquitin
  • Ubiquitinated Proteins
  • Superoxides
  • Proteasome Endopeptidase Complex

Grant support

This work was supported by the National Research, Development and Innovation Office[KKP129797; GINOP-2.3.2-15-2016-00032; FK132183; National Laboratory for Biotechnology program; PD135587] and the Hungarian Academy of Sciences [LP-2014/2; BO/00078/18; UNKP-20-5; UNKP-19-4].