Immiscible inclusion bodies formed by polyglutamine and poly(glycine-alanine) are enriched with distinct proteomes but converge in proteins that are risk factors for disease and involved in protein degradation

PLoS One. 2020 Aug 28;15(8):e0233247. doi: 10.1371/journal.pone.0233247. eCollection 2020.

Abstract

Poly(glycine-alanine) (polyGA) is one of the polydipeptides expressed in Frontotemporal Dementia and/or Amyotrophic Lateral Sclerosis 1 caused by C9ORF72 mutations and accumulates as inclusion bodies in the brain of patients. Superficially these inclusions are similar to those formed by polyglutamine (polyQ)-expanded Huntingtin exon 1 (Httex1) in Huntington's disease. Both have been reported to form an amyloid-like structure suggesting they might aggregate via similar mechanisms and therefore recruit the same repertoire of endogenous proteins. When co-expressed in the same cell, polyGA101 and Httex1(Q97) inclusions adopted immiscible phases suggesting different endogenous proteins would be enriched. Proteomic analyses identified 822 proteins in the inclusions. Only 7 were specific to polyGA and 4 specific to Httex1(Q97). Quantitation demonstrated distinct enrichment patterns for the proteins not specific to each inclusion type (up to ~8-fold normalized to total mass). The proteasome, microtubules, TriC chaperones, and translational machinery were enriched in polyGA aggregates, whereas Dnaj chaperones, nuclear envelope and RNA splicing proteins were enriched in Httex1(Q97) aggregates. Both structures revealed a collection of folding and degradation machinery including proteins in the Httex1(Q97) aggregates that are risk factors for other neurodegenerative diseases involving protein aggregation when mutated, which suggests a convergence point in the pathomechanisms of these diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • C9orf72 Protein / genetics
  • C9orf72 Protein / metabolism
  • Cell Line
  • Exons
  • Humans
  • Huntingtin Protein / genetics
  • Huntingtin Protein / metabolism
  • Inclusion Bodies / genetics
  • Inclusion Bodies / metabolism*
  • Inclusion Bodies / pathology
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Mice
  • Microscopy, Confocal
  • Mutation
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Neurodegenerative Diseases / genetics
  • Neurodegenerative Diseases / metabolism
  • Neurodegenerative Diseases / pathology
  • Peptides / genetics
  • Peptides / metabolism*
  • Protein Aggregation, Pathological / genetics
  • Protein Aggregation, Pathological / metabolism
  • Protein Aggregation, Pathological / pathology
  • Proteins / genetics
  • Proteins / metabolism*
  • Proteolysis
  • Proteome / genetics
  • Proteome / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Risk Factors
  • Solubility

Substances

  • C9orf72 Protein
  • C9orf72 protein, human
  • HTT protein, human
  • Huntingtin Protein
  • Luminescent Proteins
  • Nerve Tissue Proteins
  • Peptides
  • Proteins
  • Proteome
  • Recombinant Fusion Proteins
  • poly(glycyl-alanyl)
  • polyglutamine

Grant support

This work was funded by grants to DMH (National Health and Medical Research Council APP1161803 (https://www.nhmrc.gov.au/) and Motor Neuron Disease Research Institute, Australia small grant (https://www.mndaust.asn.au/Discover-our-research/About-MNDRIA.aspx)) and to DMH and GER (Australian Research Council DP170103093) (https://www.arc.gov.au/). MR acknowledges support from an Australian Government Research Training Program (RTP) Scholarship via the University of Melbourne (https://scholarships.unimelb.edu.au/awards/research-training-program-scholarship) and an Egyptian Ministry of Higher Education and Scientific Research PhD scholarship (http://portal.mohesr.gov.eg/en-us/Pages/default.aspx). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.