A peptidylic inhibitor for neutralizing expanded CAG RNA-induced nucleolar stress in polyglutamine diseases

RNA. 2018 Apr;24(4):486-498. doi: 10.1261/rna.062703.117. Epub 2018 Jan 2.

Abstract

Polyglutamine (polyQ) diseases are a class of progressive neurodegenerative disorders characterized by the expression of both expanded CAG RNA and misfolded polyQ protein. We previously reported that the direct interaction between expanded CAG RNA and nucleolar protein nucleolin (NCL) impedes preribosomal RNA (pre-rRNA) transcription, and eventually triggers nucleolar stress-induced apoptosis in polyQ diseases. Here, we report that a 21-amino acid peptide, named "beta-structured inhibitor for neurodegenerative diseases" (BIND), effectively suppresses toxicity induced by expanded CAG RNA. When administered to a cell model, BIND potently inhibited cell death induced by expanded CAG RNA with an IC50 value of ∼0.7 µM. We showed that the function of BIND is dependent on Glu2, Lys13, Gly14, Ile18, Glu19, and Phe20. BIND treatment restored the subcellular localization of nucleolar marker protein and the expression level of pre-45s rRNA Through isothermal titration calorimetry analysis, we demonstrated that BIND suppresses nucleolar stress via a direct interaction with CAG RNA in a length-dependent manner. The mean binding constants (KD) of BIND to SCA2CAG22 , SCA2CAG42 , SCA2CAG55 , and SCA2CAG72 RNA are 17.28, 5.60, 4.83, and 0.66 µM, respectively. In vivo, BIND ameliorates retinal degeneration and climbing defects, and extends the lifespan of Drosophila expressing expanded CAG RNA. These effects suggested that BIND can suppress neurodegeneration in diverse polyQ disease models in vivo and in vitro without exerting observable cytotoxic effect. Our results collectively demonstrated that BIND is an effective inhibitor of expanded CAG RNA-induced toxicity in polyQ diseases.

Keywords: Drosophila; Huntington's disease; spinocerebellar ataxias.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Death / drug effects
  • Drosophila / genetics
  • HEK293 Cells
  • Humans
  • Huntington Disease / genetics
  • Huntington Disease / pathology
  • Huntington Disease / therapy*
  • Nucleolin
  • Peptides / metabolism
  • Peptides / pharmacology*
  • Phosphoproteins / genetics
  • Protein Folding
  • Proteostasis Deficiencies / genetics*
  • Proteostasis Deficiencies / pathology
  • Proteostasis Deficiencies / therapy
  • RNA, Ribosomal / genetics
  • RNA-Binding Proteins / genetics
  • Spinocerebellar Ataxias / genetics
  • Spinocerebellar Ataxias / pathology
  • Spinocerebellar Ataxias / therapy*
  • Transcription, Genetic / genetics
  • Trinucleotide Repeats / drug effects
  • Trinucleotide Repeats / genetics*

Substances

  • Peptides
  • Phosphoproteins
  • RNA, Ribosomal
  • RNA-Binding Proteins
  • polyglutamine