Epigallocatechin-3-gallate and tetracycline differently affect ataxin-3 fibrillogenesis and reduce toxicity in spinocerebellar ataxia type 3 model

Hum Mol Genet. 2014 Dec 15;23(24):6542-52. doi: 10.1093/hmg/ddu373. Epub 2014 Jul 16.


The polyglutamine (polyQ)-containing protein ataxin-3 (AT3) triggers the neurodegenerative disease spinocerebellar ataxia type 3 (SCA3) when its polyQ tract is expanded beyond a critical length. This results in protein aggregation and generation of toxic oligomers and fibrils. Currently, no effective treatment is available for such and other polyQ diseases. Therefore, plenty of investigations are being carried on to assess the mechanism of action and the therapeutic potential of anti-amyloid agents. The polyphenol compound epigallocatechin-3-gallate (EGCG) and tetracycline have been shown to exert some effect in preventing fibrillogenesis of amyloidogenic proteins. Here, we have incubated an expanded AT3 variant with either compound to assess their effects on the aggregation pattern. The process was monitored by atomic force microscopy and Fourier transform infrared spectroscopy. Whereas in the absence of any treatment, AT3 gives rise to amyloid β-rich fibrils, whose hallmark is the typical glutamine side-chain hydrogen bonding, when incubated in the presence of EGCG it generated soluble, SDS-resistant aggregates, much poorer in β-sheets and devoid of any ordered side-chain hydrogen bonding. These are off-pathway species that persist until the latest incubation time and are virtually absent in the control sample. In contrast, tetracycline did not produce major alterations in the structural features of the aggregated species compared with the control, but substantially increased their solubility. Both compounds significantly reduced toxicity, as shown by the MTT assay in COS-7 cell line and in a transgenic Caenorhabditis elegans strain expressing in the nervous system an AT3 expanded variant in fusion with GFP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid / antagonists & inhibitors*
  • Amyloid / chemistry
  • Amyloid / metabolism
  • Animals
  • Ataxin-3
  • COS Cells
  • Caenorhabditis elegans / drug effects*
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / metabolism
  • Caenorhabditis elegans Proteins / chemistry*
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism
  • Catechin / analogs & derivatives*
  • Catechin / pharmacology
  • Cell Survival / drug effects
  • Chlorocebus aethiops
  • Disease Models, Animal
  • Gene Expression
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Hydrogen Bonding
  • Machado-Joseph Disease / drug therapy*
  • Machado-Joseph Disease / genetics
  • Machado-Joseph Disease / metabolism
  • Machado-Joseph Disease / pathology
  • Microscopy, Atomic Force
  • Nerve Tissue Proteins / chemistry*
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Neuroprotective Agents / pharmacology*
  • Protein Aggregates / drug effects
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Spectroscopy, Fourier Transform Infrared
  • Tetracycline / pharmacology*


  • Amyloid
  • Caenorhabditis elegans Proteins
  • Nerve Tissue Proteins
  • Neuroprotective Agents
  • Protein Aggregates
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Catechin
  • epigallocatechin gallate
  • Ataxin-3
  • atx-3 protein, C elegans
  • Tetracycline