title: The Proline/Arginine Dipeptide from Hexanucleotide Repeat ExpandedC9ORF72Inhibits the Proteasome.
abstract: An intronic hexanucleotide repeat expansion (HRE) mutation in theC9ORF72gene is the most common cause of familial ALS and frontotemporal dementia (FTD) and is found in ∼7% of individuals with apparently sporadic disease. Several different diamino acid peptides can be generated from the HRE by noncanonical translation (repeat-associated non-ATG translation, or RAN translation), and some of these peptides can be toxic. Here, we studied the effects of two arginine containing RAN translation products [proline/arginine repeated 20 times (PR20) and glycine/arginine repeated 20 times (GR20)] in primary rat spinal cord neuron cultures grown on an astrocyte feeder layer. We find that PR20kills motor neurons with an LD50of 2 µM, but in contrast to the effects of other ALS-causing mutant proteins (i.e., SOD or TDP43), PR20does not evoke the biochemical signature of mitochondrial dysfunction, ER stress, or mTORC down-regulation. PR20does result in a time-dependent build-up of ubiquitylated substrates, and this is associated with a reduction of flux through both autophagic and proteasomal degradation pathways. GR20, however, does not have these effects. The effects of PR20on the proteasome are likely to be direct because (1) PR20physically associates with proteasomes in biochemical assays, and (2) PR20inhibits the degradation of a ubiquitylated test substrate when presented to purified proteasomes. Application of a proteasomal activator (IU1) blocks the toxic effects of PR20on motor neuron survival. This work suggests that proteasomal activators have therapeutic potential in individuals withC9ORF72HRE.
authors.affiliation: Department of Chemical and Biomolecular Engineering, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, PA, 19104; Department of Biology, College of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, 19104.
authors.forename: Rahul
authors.identifier: 0000-0001-8263-2455
authors.initials: R
authors.lastname: Gupta
authors.affiliation: Department of Biochemistry, College of Arts and Sciences, University of Pennsylvania , Philadelphia, PA, 19104.
authors.forename: Matthews
authors.initials: M
authors.lastname: Lan
authors.affiliation: Division of Neurology, Department of Pediatrics, Research Institute, Children's Hospital of Philadelphia , Philadelphia, PA, 19104.
authors.forename: Jelena
authors.initials: J
authors.lastname: Mojsilovic-Petrovic
authors.affiliation: Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine , Seoul 03080, Republic of Korea.
authors.forename: Won Hoon
authors.initials: WH
authors.lastname: Choi
authors.affiliation: Department of Neurology, University of Michigan , Ann Arbor, MI, 48109.
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Safren
authors.affiliation: Department of Neurology, University of Michigan , Ann Arbor, MI, 48109.
authors.forename: Sami
authors.initials: S
authors.lastname: Barmada
authors.affiliation: Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine , Seoul 03080, Republic of Korea.
authors.forename: Min Jae
authors.identifier: 0000-0002-3252-6467
authors.initials: MJ
authors.lastname: Lee
authors.affiliation: Division of Neurology, Department of Pediatrics, Research Institute, Children's Hospital of Philadelphia, Philadelphia, PA, 19104; Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104.
authors.forename: Robert
authors.initials: R
authors.lastname: Kalb
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018920:Coculture Techniques; D042622:DNA Repeat Expansion; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010455:Peptides / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
chemical_list: C000624307:GR20 peptide; D020662:Guanine Nucleotide Exchange Factors; C000624306:PR20 peptide; D010455:Peptides; D061988:Proteasome Inhibitors; D046988:Proteasome Endopeptidase Complex
keywords: ALS; frontotemporal dementia; lysosome-autophagy; motor neuron; proteasome 