Mapping the degradation pathway of a disease-linked aspartoacylase variant

PLoS Genet. 2021 Apr 29;17(4):e1009539. doi: 10.1371/journal.pgen.1009539. eCollection 2021 Apr.

Abstract

Canavan disease is a severe progressive neurodegenerative disorder that is characterized by swelling and spongy degeneration of brain white matter. The disease is genetically linked to polymorphisms in the aspartoacylase (ASPA) gene, including the substitution C152W. ASPA C152W is associated with greatly reduced protein levels in cells, yet biophysical experiments suggest a wild-type like thermal stability. Here, we use ASPA C152W as a model to investigate the degradation pathway of a disease-causing protein variant. When we expressed ASPA C152W in Saccharomyces cerevisiae, we found a decreased steady state compared to wild-type ASPA as a result of increased proteasomal degradation. However, molecular dynamics simulations of ASPA C152W did not substantially deviate from wild-type ASPA, indicating that the native state is structurally preserved. Instead, we suggest that the C152W substitution interferes with the de novo folding pathway resulting in increased proteasomal degradation before reaching its stable conformation. Systematic mapping of the protein quality control components acting on misfolded and aggregation-prone species of C152W, revealed that the degradation is highly dependent on the molecular chaperone Hsp70, its co-chaperone Hsp110 as well as several quality control E3 ubiquitin-protein ligases, including Ubr1. In addition, the disaggregase Hsp104 facilitated refolding of aggregated ASPA C152W, while Cdc48 mediated degradation of insoluble ASPA protein. In human cells, ASPA C152W displayed increased proteasomal turnover that was similarly dependent on Hsp70 and Hsp110. Our findings underscore the use of yeast to determine the protein quality control components involved in the degradation of human pathogenic variants in order to identify potential therapeutic targets.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amidohydrolases / genetics*
  • Amino Acid Substitution / genetics
  • Canavan Disease / genetics*
  • Canavan Disease / pathology
  • HSP110 Heat-Shock Proteins / genetics*
  • HSP70 Heat-Shock Proteins / genetics*
  • Heat-Shock Proteins / genetics
  • Humans
  • Molecular Chaperones / genetics
  • Mutation / genetics
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins / genetics
  • Ubiquitin-Protein Ligases / genetics

Substances

  • HSP110 Heat-Shock Proteins
  • HSP70 Heat-Shock Proteins
  • Heat-Shock Proteins
  • Molecular Chaperones
  • Saccharomyces cerevisiae Proteins
  • HsP104 protein, S cerevisiae
  • UBR1 protein, S cerevisiae
  • Ubiquitin-Protein Ligases
  • Amidohydrolases
  • aspartoacylase

Grants and funding

This work was supported by the Novo Nordisk Foundation (https:// novonordiskfonden.dk) challenge programme PRISM (to K.L.L., A.S. & R.H.P.) and NNF18OC0052441 (to R.H.P.), the Lundbeck Foundation (https://www.lundbeckfonden.com) R249-2017-510 (to L.C. & R.H.P.) and R272-2017-452 and R209-2015-3283 (to A.S.), and Danish Council for Independent Research (Natur og Univers, Det Frie Forskningsråd) (https://dff.dk) 7014-00039B (to R.H.P.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.