A Robust Assay to Monitor Ataxin-3 Amyloid Fibril Assembly

Cells. 2022 Jun 19;11(12):1969. doi: 10.3390/cells11121969.


Spinocerebellar ataxia type 3 (SCA3) is caused by the expansion of a glutamine repeat in the protein ataxin-3, which is deposited as intracellular aggregates in affected brain regions. Despite the controversial role of ataxin-3 amyloid structures in SCA3 pathology, the identification of molecules with the capacity to prevent aberrant self-assembly and stabilize functional conformation(s) of ataxin-3 is a key to the development of therapeutic solutions. Amyloid-specific kinetic assays are routinely used to measure rates of protein self-assembly in vitro and are employed during screening for fibrillation inhibitors. The high tendency of ataxin-3 to assemble into oligomeric structures implies that minor changes in experimental conditions can modify ataxin-3 amyloid assembly kinetics. Here, we determine the self-association rates of ataxin-3 and present a detailed study of the aggregation of normal and pathogenic ataxin-3, highlighting the experimental conditions that should be considered when implementing and validating ataxin-3 amyloid progress curves in different settings and in the presence of ataxin-3 interactors. This assay provides a unique and robust platform to screen for modulators of the first steps of ataxin-3 aggregation-a starting point for further studies with cell and animal models of SCA3.

Keywords: equilibrium dissociation constant; polyglutamine expansion; reproducibility; self-association rates; switchSENSE; thioflavin-T; ubiquitin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid* / metabolism
  • Animals
  • Ataxin-3 / metabolism
  • Brain / metabolism
  • Machado-Joseph Disease* / metabolism
  • Machado-Joseph Disease* / pathology
  • Peptides / metabolism


  • Amyloid
  • Peptides
  • Ataxin-3

Grant support

This study was supported by FEDER funds through the COMPETE 2020—Operacional Programme for Competitiveness and Internationalisation (POCI), Portugal 2020; Portuguese funds through FCT in the framework of the projects “PQTools: Molecular tools for Machado-Joseph Disease” (POCI-01-0145-FEDER-031173), “NAPPIT-MJD:Nuclear ataxin-3 protein-protein interactions as therapeutic targets in Machado-Joseph disease” (POCI-01-0145-FEDER-029056), “AggreGATE: Targeting diffusible oligomers of alpha-synuclein and ataxin-3: a drug repurposing opportunity for the treatment of neurodegenerative diseases” (POCI-01-0145-FEDER-031323), and “Institute for Research and Innovation in Health Sciences” (POCI-01-0145-FEDER-007274); the European Union’s Horizon 2020 Research and Innovation programme under grant agreement ID 952334 “PhasAGE”. The work was also supported by a research grant from National Ataxia Foundation to A.S. F.F. is the recipient of an FCT PhD fellowship (SFRH/BD/133009/2017). The funders had no role in the design, collection, analysis or interpretation of the data, or in the writing of the manuscript.