In Situ Structure of Neuronal C9orf72 Poly-GA Aggregates Reveals Proteasome Recruitment

Cell. 2018 Feb 8;172(4):696-705.e12. doi: 10.1016/j.cell.2017.12.030. Epub 2018 Feb 1.


Protein aggregation and dysfunction of the ubiquitin-proteasome system are hallmarks of many neurodegenerative diseases. Here, we address the elusive link between these phenomena by employing cryo-electron tomography to dissect the molecular architecture of protein aggregates within intact neurons at high resolution. We focus on the poly-Gly-Ala (poly-GA) aggregates resulting from aberrant translation of an expanded GGGGCC repeat in C9orf72, the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia. We find that poly-GA aggregates consist of densely packed twisted ribbons that recruit numerous 26S proteasome complexes, while other macromolecules are largely excluded. Proximity to poly-GA ribbons stabilizes a transient substrate-processing conformation of the 26S proteasome, suggesting stalled degradation. Thus, poly-GA aggregates may compromise neuronal proteostasis by driving the accumulation and functional impairment of a large fraction of cellular proteasomes.

Keywords: ALS; FTD; UPS; cryo-EM; cryo-ET; cryo-FIB; cryoelectron microscopy; dipeptide-repeat proteins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / analogs & derivatives*
  • Alanine / genetics
  • Alanine / metabolism
  • Amyotrophic Lateral Sclerosis / genetics
  • Amyotrophic Lateral Sclerosis / metabolism
  • Amyotrophic Lateral Sclerosis / pathology
  • Animals
  • C9orf72 Protein* / genetics
  • C9orf72 Protein* / metabolism
  • Frontotemporal Dementia / genetics
  • Frontotemporal Dementia / metabolism
  • Frontotemporal Dementia / pathology
  • HEK293 Cells
  • Humans
  • Neurons* / metabolism
  • Neurons* / pathology
  • Polyglutamic Acid* / genetics
  • Polyglutamic Acid* / metabolism
  • Proteasome Endopeptidase Complex* / genetics
  • Proteasome Endopeptidase Complex* / metabolism
  • Protein Aggregates*
  • Protein Biosynthesis
  • Protein Stability
  • Protein Structure, Quaternary
  • Rats
  • Rats, Sprague-Dawley


  • C9orf72 Protein
  • Protein Aggregates
  • Polyglutamic Acid
  • poly(glutamic acid-alanine)
  • Proteasome Endopeptidase Complex
  • ATP dependent 26S protease
  • Alanine