1
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Craig RA, De Vicente J, Estrada AA, Feng JA, Lexa KW, Canet MJ, Dowdle WE, Erickson RI, Flores BN, Haddick PCG, Kane LA, Lewcock JW, Moerke NJ, Poda SB, Sweeney Z, Takahashi RH, Tong V, Wang J, Yulyaningsih E, Solanoy H, Scearce-Levie K, Sanchez PE, Tang L, Xu M, Zhang R, Osipov M. Discovery of DNL343: A Potent, Selective, and Brain-Penetrant eIF2B Activator Designed for the Treatment of Neurodegenerative Diseases. J Med Chem 2024; 67:5758-5782. [PMID: 38511649 DOI: 10.1021/acs.jmedchem.3c02422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2024]
Abstract
Eukaryotic translation initiation factor 2B (eIF2B) is a key component of the integrated stress response (ISR), which regulates protein synthesis and stress granule formation in response to cellular insult. Modulation of the ISR has been proposed as a therapeutic strategy for treatment of neurodegenerative diseases such as vanishing white matter (VWM) disease and amyotrophic lateral sclerosis (ALS) based on its ability to improve cellular homeostasis and prevent neuronal degeneration. Herein, we report the small-molecule discovery campaign that identified potent, selective, and CNS-penetrant eIF2B activators using both structure- and ligand-based drug design. These discovery efforts culminated in the identification of DNL343, which demonstrated a desirable preclinical drug profile, including a long half-life and high oral bioavailability across preclinical species. DNL343 was progressed into clinical studies and is currently undergoing evaluation in late-stage clinical trials for ALS.
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Affiliation(s)
- Robert A Craig
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Javier De Vicente
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Anthony A Estrada
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Jianwen A Feng
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Katrina W Lexa
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Mark J Canet
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - William E Dowdle
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Rebecca I Erickson
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Brittany N Flores
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Patrick C G Haddick
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Lesley A Kane
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Joseph W Lewcock
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Nathan J Moerke
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Suresh B Poda
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Zachary Sweeney
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Ryan H Takahashi
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Vincent Tong
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Jing Wang
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Ernie Yulyaningsih
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Hilda Solanoy
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | | | - Pascal E Sanchez
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
| | - Liwei Tang
- Department of Chemistry, WuXi AppTec Co., Ltd., Tianjin 300457, China
| | - Musheng Xu
- Department of Chemistry, WuXi AppTec Co., Ltd., Tianjin 300457, China
| | - Rui Zhang
- Department of Chemistry, WuXi AppTec Co., Ltd., Tianjin 300457, China
| | - Maksim Osipov
- Denali Therapeutics Inc., South San Francisco, California 94080, United States
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2
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Wright SE, Rodriguez CM, Monroe J, Xing J, Krans A, Flores BN, Barsur V, Ivanova MI, Koutmou KS, Barmada SJ, Todd PK. CGG repeats trigger translational frameshifts that generate aggregation-prone chimeric proteins. Nucleic Acids Res 2022; 50:8674-8689. [PMID: 35904811 PMCID: PMC9410890 DOI: 10.1093/nar/gkac626] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 07/13/2022] [Indexed: 11/25/2022] Open
Abstract
CGG repeat expansions in the FMR1 5’UTR cause the neurodegenerative disease Fragile X-associated tremor/ataxia syndrome (FXTAS). These repeats form stable RNA secondary structures that support aberrant translation in the absence of an AUG start codon (RAN translation), producing aggregate-prone peptides that accumulate within intranuclear neuronal inclusions and contribute to neurotoxicity. Here, we show that the most abundant RAN translation product, FMRpolyG, is markedly less toxic when generated from a construct with a non-repetitive alternating codon sequence in place of the CGG repeat. While exploring the mechanism of this differential toxicity, we observed a +1 translational frameshift within the CGG repeat from the arginine to glycine reading frame. Frameshifts occurred within the first few translated repeats and were triggered predominantly by RNA sequence and structural features. Short chimeric R/G peptides form aggregates distinct from those formed by either pure arginine or glycine, and these chimeras induce toxicity in cultured rodent neurons. Together, this work suggests that CGG repeats support translational frameshifting and that chimeric RAN translated peptides may contribute to CGG repeat-associated toxicity in FXTAS and related disorders.
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Affiliation(s)
- Shannon E Wright
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Caitlin M Rodriguez
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA.,Department of Genetics, Stanford University School of Medicine, Stanford, CA 84305, USA
| | - Jeremy Monroe
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jiazheng Xing
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Amy Krans
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,VA Ann Arbor Healthcare System, Ann Arbor, MI 48105, USA
| | - Brittany N Flores
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Venkatesha Barsur
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Magdalena I Ivanova
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,Biophysics Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Kristin S Koutmou
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Sami J Barmada
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Peter K Todd
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,VA Ann Arbor Healthcare System, Ann Arbor, MI 48105, USA
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3
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He F, Flores BN, Krans A, Frazer M, Natla S, Niraula S, Adefioye O, Barmada SJ, Todd PK. The carboxyl termini of RAN translated GGGGCC nucleotide repeat expansions modulate toxicity in models of ALS/FTD. Acta Neuropathol Commun 2020; 8:122. [PMID: 32753055 PMCID: PMC7401224 DOI: 10.1186/s40478-020-01002-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 07/22/2020] [Indexed: 12/13/2022] Open
Abstract
An intronic hexanucleotide repeat expansion in C9ORF72 causes familial and sporadic amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). This repeat is thought to elicit toxicity through RNA mediated protein sequestration and repeat-associated non-AUG (RAN) translation of dipeptide repeat proteins (DPRs). We generated a series of transgenic Drosophila models expressing GGGGCC (G4C2) repeats either inside of an artificial intron within a GFP reporter or within the 5' untranslated region (UTR) of GFP placed in different downstream reading frames. Expression of 484 intronic repeats elicited minimal alterations in eye morphology, viability, longevity, or larval crawling but did trigger RNA foci formation, consistent with prior reports. In contrast, insertion of repeats into the 5' UTR elicited differential toxicity that was dependent on the reading frame of GFP relative to the repeat. Greater toxicity correlated with a short and unstructured carboxyl terminus (C-terminus) in the glycine-arginine (GR) RAN protein reading frame. This change in C-terminal sequence triggered nuclear accumulation of all three RAN DPRs. A similar differential toxicity and dependence on the GR C-terminus was observed when repeats were expressed in rodent neurons. The presence of the native C-termini across all three reading frames was partly protective. Taken together, these findings suggest that C-terminal sequences outside of the repeat region may alter the behavior and toxicity of dipeptide repeat proteins derived from GGGGCC repeats.
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4
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Flores BN, Li X, Malik AM, Martinez J, Beg AA, Barmada SJ. An Intramolecular Salt Bridge Linking TDP43 RNA Binding, Protein Stability, and TDP43-Dependent Neurodegeneration. Cell Rep 2020; 27:1133-1150.e8. [PMID: 31018129 PMCID: PMC6499398 DOI: 10.1016/j.celrep.2019.03.093] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 01/28/2019] [Accepted: 03/25/2019] [Indexed: 12/13/2022] Open
Abstract
The majority of individuals with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) exhibit neuronal cytoplasmic inclusions rich in the RNA binding protein TDP43. Even so, the relation between the RNA binding properties of TDP43 and neurodegeneration remains obscure. Here, we show that engineered mutations disrupting a salt bridge between the RNA recognition motifs of TDP43 interfere with RNA binding and eliminate the recognition of native TDP43 substrates. The same mutations dramatically destabilize TDP43, alter its subcellular localization, and abrogate TDP43-dependent neuro-degeneration. Worms harboring homologous TDP-1 mutations phenocopy knockout strains, confirming the necessity of salt bridge residues for TDP43 function. Moreover, the accumulation of functional TDP43, but not RNA binding-deficient variants, disproportionately affects transcripts encoding ribo-some and oxidative phosphorylation components. These studies demonstrate the significance of the salt bridge in sustaining TDP43 stability and RNA binding properties, factors that are crucial for neurodegeneration arising from TDP43 deposition in ALS and FTD. Flores et al. uncover essential roles for an intramolecular salt bridge in the function of TDP43, an RNA binding protein implicated in neurodegenerative diseases. Salt bridge interruption attenuates TDP43 RNA binding affinity and specificity, destabilizes the protein, and prevents TDP43-mediated neurotoxicity arising from misprocessing of ribosomal and mitochondrial transcripts.
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Affiliation(s)
- Brittany N Flores
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI 48104, USA; Department of Neurology, University of Michigan, Ann Arbor, MI 48104, USA
| | - Xingli Li
- Department of Neurology, University of Michigan, Ann Arbor, MI 48104, USA
| | - Ahmed M Malik
- Medical Scientist Training Program, University of Michigan, Ann Arbor, MI 48104, USA; Neuroscience Graduate Program, Department of Pharmacology, University of Michigan, Ann Arbor, MI 48104, USA
| | - Jose Martinez
- Neuroscience Graduate Program, Department of Pharmacology, University of Michigan, Ann Arbor, MI 48104, USA
| | - Asim A Beg
- Neuroscience Graduate Program, Department of Pharmacology, University of Michigan, Ann Arbor, MI 48104, USA
| | - Sami J Barmada
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI 48104, USA; Department of Neurology, University of Michigan, Ann Arbor, MI 48104, USA; Neuroscience Graduate Program, Department of Pharmacology, University of Michigan, Ann Arbor, MI 48104, USA.
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5
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Rodriguez CM, Wright SE, Kearse MG, Haenfler JM, Flores BN, Liu Y, Ifrim MF, Glineburg MR, Krans A, Jafar-Nejad P, Sutton MA, Bassell GJ, Parent JM, Rigo F, Barmada SJ, Todd PK. A native function for RAN translation and CGG repeats in regulating fragile X protein synthesis. Nat Neurosci 2020; 23:386-397. [PMID: 32066985 PMCID: PMC7668390 DOI: 10.1038/s41593-020-0590-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 01/10/2020] [Indexed: 02/07/2023]
Abstract
Repeat-associated non-AUG translation of expanded CGG repeats (CGG RAN) from the FMR1 5’ UTR produces toxic proteins that contribute to neurodegeneration in Fragile X-associated Tremor/Ataxia Syndrome (FXTAS). Here we describe how unexpanded CGG repeats and their translation play conserved roles in regulating FMRP synthesis. In neurons, CGG RAN acts as an inhibitory upstream open reading frame to suppress basal FMRP production. Activation of mGluR5 receptors enhances FMRP synthesis. This enhancement requires both the CGG repeat and CGG RAN initiation sites. Using non-cleaving antisense oligonucleotides (ASOs), we selectively blocked RAN translation. This ASO blockade enhanced endogenous human neuronal FMRP expression. In human and rodent neurons, RAN blocking ASOs suppressed repeat toxicity and prolonged survival. These findings delineate a native function for CGG repeats and RAN translation in regulating basal and activity-dependent FMRP synthesis and demonstrate the therapeutic potential of modulating CGG RAN translation in fragile X-associated disorders.
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Affiliation(s)
- Caitlin M Rodriguez
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Shannon E Wright
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Michael G Kearse
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,Department of Biological Chemistry and Pharmacology, Center for RNA Biology, Ohio State University, Columbus, OH, USA
| | - Jill M Haenfler
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Brittany N Flores
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Yu Liu
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Marius F Ifrim
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Mary R Glineburg
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Amy Krans
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,VA Ann Arbor Healthcare System, Ann Arbor, MI, USA
| | | | - Michael A Sutton
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Jack M Parent
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,VA Ann Arbor Healthcare System, Ann Arbor, MI, USA
| | - Frank Rigo
- Ionis Pharmaceuticals, Carlsbad, CA, USA
| | - Sami J Barmada
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Peter K Todd
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA. .,VA Ann Arbor Healthcare System, Ann Arbor, MI, USA.
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6
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Green KM, Sheth UJ, Flores BN, Wright SE, Sutter AB, Kearse MG, Barmada SJ, Ivanova MI, Todd PK. High-throughput screening yields several small-molecule inhibitors of repeat-associated non-AUG translation. J Biol Chem 2019; 294:18624-18638. [PMID: 31649034 DOI: 10.1074/jbc.ra119.009951] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 10/16/2019] [Indexed: 12/18/2022] Open
Abstract
Repeat-associated non-AUG (RAN) translation is a noncanonical translation initiation event that occurs at nucleotide-repeat expansion mutations that are associated with several neurodegenerative diseases, including fragile X-associated tremor ataxia syndrome (FXTAS), ALS, and frontotemporal dementia (FTD). Translation of expanded repeats produces toxic proteins that accumulate in human brains and contribute to disease pathogenesis. Consequently, RAN translation constitutes a potentially important therapeutic target for managing multiple neurodegenerative disorders. Here, we adapted a previously developed RAN translation assay to a high-throughput format to screen 3,253 bioactive compounds for inhibition of RAN translation of expanded CGG repeats associated with FXTAS. We identified five diverse small molecules that dose-dependently inhibited CGG RAN translation, while relatively sparing canonical translation. All five compounds also inhibited RAN translation of expanded GGGGCC repeats associated with ALS and FTD. Using CD and native gel analyses, we found evidence that three of these compounds, BIX01294, CP-31398, and propidium iodide, bind directly to the repeat RNAs. These findings provide proof-of-principle supporting the development of selective small-molecule RAN translation inhibitors that act across multiple disease-causing repeats.
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Affiliation(s)
- Katelyn M Green
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109; Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan 48109
| | - Udit J Sheth
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109
| | - Brittany N Flores
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109; Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan 48109
| | - Shannon E Wright
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109
| | - Alexandra B Sutter
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109
| | - Michael G Kearse
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Chemistry and Pharmacology, Center for RNA Biology, Ohio State University, Columbus, Ohio 43210
| | - Sami J Barmada
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109; Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan 48109
| | - Magdalena I Ivanova
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109; Biophysics Program, University of Michigan, Ann Arbor, Michigan 48109
| | - Peter K Todd
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109; Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, Michigan 48109; Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, Michigan 48105.
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Linsalata AE, He F, Malik AM, Glineburg MR, Green KM, Natla S, Flores BN, Krans A, Archbold HC, Fedak SJ, Barmada SJ, Todd PK. DDX3X and specific initiation factors modulate FMR1 repeat-associated non-AUG-initiated translation. EMBO Rep 2019; 20:e47498. [PMID: 31347257 DOI: 10.15252/embr.201847498] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 06/19/2019] [Accepted: 06/26/2019] [Indexed: 12/12/2022] Open
Abstract
A CGG trinucleotide repeat expansion in the 5' UTR of FMR1 causes the neurodegenerative disorder Fragile X-associated tremor/ataxia syndrome (FXTAS). This repeat supports a non-canonical mode of protein synthesis known as repeat-associated, non-AUG (RAN) translation. The mechanism underlying RAN translation at CGG repeats remains unclear. To identify modifiers of RAN translation and potential therapeutic targets, we performed a candidate-based screen of eukaryotic initiation factors and RNA helicases in cell-based assays and a Drosophila melanogaster model of FXTAS. We identified multiple modifiers of toxicity and RAN translation from an expanded CGG repeat in the context of the FMR1 5'UTR. These include the DEAD-box RNA helicase belle/DDX3X, the helicase accessory factors EIF4B/4H, and the start codon selectivity factors EIF1 and EIF5. Disrupting belle/DDX3X selectively inhibited FMR1 RAN translation in Drosophila in vivo and cultured human cells, and mitigated repeat-induced toxicity in Drosophila and primary rodent neurons. These findings implicate RNA secondary structure and start codon fidelity as critical elements mediating FMR1 RAN translation and identify potential targets for treating repeat-associated neurodegeneration.
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Affiliation(s)
- Alexander E Linsalata
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, USA.,Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Fang He
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,Department of Biological and Health Sciences, Texas A&M University, Kingsville, Kingsville, TX, USA
| | - Ahmed M Malik
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | | | - Katelyn M Green
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, USA.,Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Sam Natla
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Brittany N Flores
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, USA.,Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Amy Krans
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | | | - Stephen J Fedak
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Sami J Barmada
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Peter K Todd
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.,Ann Arbor VA Medical Center, Ann Arbor, MI, USA
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8
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Flores BN, Dulchavsky ME, Krans A, Sawaya MR, Paulson HL, Todd PK, Barmada SJ, Ivanova MI. Distinct C9orf72-Associated Dipeptide Repeat Structures Correlate with Neuronal Toxicity. PLoS One 2016; 11:e0165084. [PMID: 27776165 PMCID: PMC5077081 DOI: 10.1371/journal.pone.0165084] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 10/05/2016] [Indexed: 12/14/2022] Open
Abstract
Hexanucleotide repeat expansions in C9orf72 are the most common inherited cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The expansions elicit toxicity in part through repeat-associated non-AUG (RAN) translation of the intronic (GGGGCC)n sequence into dipeptide repeat-containing proteins (DPRs). Little is known, however, about the structural characteristics and aggregation propensities of the dipeptide units comprising DPRs. To address this question, we synthesized dipeptide units corresponding to the three sense-strand RAN translation products, analyzed their structures by circular dichroism, electron microscopy and dye binding assays, and assessed their relative toxicity when applied to primary cortical neurons. Short, glycine-arginine (GR)3 dipeptides formed spherical aggregates and selectively reduced neuronal survival compared to glycine-alanine (GA)3 and glycine-proline (GP)3 dipeptides. Doubling peptide length had little effect on the structure of GR or GP peptides, but (GA)6 peptides formed β-sheet rich aggregates that bound thioflavin T and Congo red yet lacked the typical fibrillar morphology of amyloids. Aging of (GA)6 dipeptides increased their β-sheet content and enhanced their toxicity when applied to neurons. We also observed that the relative toxicity of each tested dipeptide was proportional to peptide internalization. Our results demonstrate that different C9orf72-related dipeptides exhibit distinct structural properties that correlate with their relative toxicity.
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Affiliation(s)
- Brittany N. Flores
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Mark E. Dulchavsky
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Amy Krans
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Michael R. Sawaya
- UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, California, United States of America
| | - Henry L. Paulson
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, United States of America
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Peter K. Todd
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, United States of America
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, United States of America
- Veterans Affairs Medical Center, Ann Arbor, Michigan, United States of America
| | - Sami J. Barmada
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, United States of America
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail: (MII); (SJB)
| | - Magdalena I. Ivanova
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, United States of America
- Biophysics Program, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail: (MII); (SJB)
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