title: Nucleolar stress and impaired stress granule formation contribute to C9orf72 RAN translation-induced cytotoxicity.
abstract: Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are the two common neurodegenerative diseases that have been associated with the GGGGCC·GGCCCC repeat RNA expansion in a noncoding region of C9orf72. It has been previously reported that unconventional repeat-associated non-ATG (RAN) translation of GGGGCC·GGCCCC repeats produces five types of dipeptide-repeat proteins (referred to as RAN proteins): poly-glycine-alanine (GA), poly-glycine-proline (GP), poly-glycine-arginine (GR), poly-proline-arginine (PR) and poly-proline-alanine (PA). Although protein aggregates of RAN proteins have been found in patients, it is unclear whether RAN protein aggregation induces neurotoxicity. In the present study, we aimed to understand the biological properties of all five types of RAN proteins. Surprisingly, our results showed that none of these RAN proteins was aggregate-prone in our cellular model and that the turnover of these RAN proteins was not affected by the ubiquitin-proteasome system or autophagy. Moreover, poly-GR and poly-PR, but not poly-GA, poly-GP or poly-PA, localized to the nucleolus and induced the translocation of the key nucleolar component nucleophosmin, leading to nucleolar stress and cell death. This poly-GR- and poly-PR-mediated defect in nucleolar function was associated with the suppression of ribosomal RNA synthesis and the impairment of stress granule formation. Taken together, the results of the present study suggest a simple model of the molecular mechanisms underlying RAN translation-mediated cytotoxicity in C9orf72-linked ALS/FTD in which nucleolar stress, but not protein aggregation, is the primary contributor to C9orf72-linked neurodegeneration.
authors.affiliation: Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences.
authors.forename: Zhouteng
authors.initials: Z
authors.lastname: Tao
authors.affiliation: Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences.
authors.forename: Hongfeng
authors.initials: H
authors.lastname: Wang
authors.affiliation: Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences.
authors.forename: Qin
authors.initials: Q
authors.lastname: Xia
authors.affiliation: Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences.
authors.forename: Ke
authors.initials: K
authors.lastname: Li
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences.
authors.forename: Kai
authors.initials: K
authors.lastname: Li
authors.affiliation: Department of Pharmacology, College of Pharmaceutical Sciences.
authors.forename: Xiaogang
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Laboratory of Chemical Biology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Xu
authors.affiliation: Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Key Laboratory of Brain Function and Disease, School of Life Sciences, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230027, China zheng.ying@suda.edu.cn wanggh@suda.edu.cn.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Wang
authors.affiliation: Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu 215021, China and zheng.ying@suda.edu.cn wanggh@suda.edu.cn.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Ying
mesh_terms: D000073885:C9orf72 Protein; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002466:Cell Nucleolus / Q000235:genetics* / Q000378:metabolism; D004151:Dipeptides / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D015870:Gene Expression; D017930:Genes, Reporter; D006801:Humans; D045586:Intranuclear Inclusion Bodies; D008954:Models, Biological; D009842:Oligopeptides / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D066329:Protein Aggregates; D014176:Protein Biosynthesis / Q000235:genetics*; D021381:Protein Transport; D011506:Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D004151:Dipeptides; D009842:Oligopeptides; D066329:Protein Aggregates; D011506:Proteins; D011993:Recombinant Fusion Proteins