Ribosome inhibition by C9ORF72-ALS/FTD-associated poly-PR and poly-GR proteins revealed by cryo-EM

• Published in: Nature communications 2022-05, Vol.13 (1), p.2776-13, Article 2776
• Main Authors: Loveland, Anna B., Svidritskiy, Egor, Susorov, Denis, Lee, Soojin, Park, Alexander, Zvornicanin, Sarah, Demo, Gabriel, Gao, Fen-Biao, Korostelev, Andrei A.
• Format: Article
• Language: English
• Subjects: 101/28; 631/337/574/1789; 631/378/1689/1285; 631/45/535/1258/1259; 631/45/611; 631/535/1258/1259; Amyotrophic lateral sclerosis; Amyotrophic Lateral Sclerosis - genetics; Amyotrophic Lateral Sclerosis - metabolism; C9orf72 Protein - genetics; C9orf72 Protein - metabolism; Cryoelectron Microscopy; Dementia disorders; Dipeptides - metabolism; Electron microscopy; Erythromycin; Frontotemporal dementia; Frontotemporal Dementia - genetics; Frontotemporal Dementia - metabolism; Glycine; Humanities and Social Sciences; Humans; multidisciplinary; Polypeptides; Proteins; Proteins - genetics; Proteins - metabolism; Ribosomes - metabolism; Science; Science (multidisciplinary); Toxicity; Transferases; Translation; Tunnels
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-30418-0

Toxic dipeptide-repeat (DPR) proteins are produced from expanded G 4 C 2 repeats in the C9ORF72 gene, the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Two DPR proteins, poly-PR and poly-GR, repress cellular translation but the molecular mechanism remains unknown. Here we show that poly-PR and poly-GR of ≥20 repeats inhibit the ribosome’s peptidyl-transferase activity at nanomolar concentrations, comparable to specific translation inhibitors. High-resolution cryogenic electron microscopy (cryo-EM) reveals that poly-PR and poly-GR block the polypeptide tunnel of the ribosome, extending into the peptidyl-transferase center (PTC). Consistent with these findings, the macrolide erythromycin, which binds in the tunnel, competes with poly-PR and restores peptidyl-transferase activity. Our results demonstrate that strong and specific binding of poly-PR and poly-GR in the ribosomal tunnel blocks translation, revealing the structural basis of their toxicity in C9ORF72 -ALS/FTD. The expansion of GGGGCC repeats in the C9ORF72 gene results in the production of disease causing abnormal proteins with polymeric glycine-arginine (poly-GR) and polymeric proline-arginine (poly-PR). Here the authors demonstrate a structural mechanism of how poly-GR and poly-PR inhibit translation and how they might also perturb ribosome assembly.