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

• Published in: Cell Vol. 172; no. 4; pp. 696 - 705.e12
• Main Authors: Guo, Qiang, Lehmer, Carina, Martínez-Sánchez, Antonio, Rudack, Till, Beck, Florian, Hartmann, Hannelore, Pérez-Berlanga, Manuela, Frottin, Frédéric, Hipp, Mark S., Hartl, F. Ulrich, Edbauer, Dieter, Baumeister, Wolfgang, Fernández-Busnadiego, Rubén
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 08-02-2018
• Subjects: Alanine - analogs & derivatives; Alanine - genetics; Alanine - metabolism; ALS; Amyotrophic Lateral Sclerosis - genetics; Amyotrophic Lateral Sclerosis - metabolism; Amyotrophic Lateral Sclerosis - pathology; Animals; C9orf72 Protein - genetics; C9orf72 Protein - metabolism; cryo-EM; cryo-ET; cryo-FIB; cryoelectron microscopy; dipeptide-repeat proteins; Frontotemporal Dementia - genetics; Frontotemporal Dementia - metabolism; Frontotemporal Dementia - pathology; FTD; 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; UPS; cryo-FIB; cryoelectron microscopy; dipeptide-repeat proteins; FTD; ALS; UPS; cryo-ET; cryo-EM
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2017.12.030

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.
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•Neuronal C9orf72 poly-GA aggregates were analyzed by cryoelectron tomography•Poly-GA aggregates in neurons consist of planar twisted ribbons•Poly-GA aggregates recruit proteasomes while excluding other large macromolecules•Interactions with poly-GA aggregates lead to proteasome stalling
Neuronal poly-GA aggregates linked to amyotrophic lateral sclerosis and frontotemporal dementia selectively sequester proteasomes.