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García Morato J, Gloeckner CJ, Kahle PJ. Proteomics elucidating physiological and pathological functions of TDP-43. Proteomics 2023; 23:e2200410. [PMID: 37671599 DOI: 10.1002/pmic.202200410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 08/02/2023] [Accepted: 08/10/2023] [Indexed: 09/07/2023]
Abstract
Trans-activation response DNA binding protein of 43 kDa (TDP-43) regulates a great variety of cellular processes in the nucleus and cytosol. In addition, a defined subset of neurodegenerative diseases is characterized by nuclear depletion of TDP-43 as well as cytosolic mislocalization and aggregation. To perform its diverse functions TDP-43 can associate with different ribonucleoprotein complexes. Combined with transcriptomics, MS interactome studies have unveiled associations between TDP-43 and the spliceosome machinery, polysomes and RNA granules. Moreover, the highly dynamic, low-valency interactions regulated by its low-complexity domain calls for innovative proximity labeling methodologies. In addition to protein partners, the analysis of post-translational modifications showed that they may play a role in the nucleocytoplasmic shuttling, RNA binding, liquid-liquid phase separation and protein aggregation of TDP-43. Here we review the various TDP-43 ribonucleoprotein complexes characterized so far, how they contribute to the diverse functions of TDP-43, and roles of post-translational modifications. Further understanding of the fluid dynamic properties of TDP-43 in ribonucleoprotein complexes, RNA granules, and self-assemblies will advance the understanding of RNA processing in cells and perhaps help to develop novel therapeutic approaches for TDPopathies.
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Affiliation(s)
- Jorge García Morato
- Laboratory of Functional Neurogenetics, Department of Neurodegeneration, German Center of Neurodegenerative Diseases and Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Christian Johannes Gloeckner
- Research Group Functional Neuroproteomics, German Center of Neurodegenerative Diseases, Tübingen, Germany
- Core Facility for Medical Bioanalytics, Institute for Ophthalmic Research, Center for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Philipp J Kahle
- Laboratory of Functional Neurogenetics, Department of Neurodegeneration, German Center of Neurodegenerative Diseases and Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Department of Biochemistry, University of Tübingen, Tübingen, Germany
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2
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Francois-Moutal L, Scott DD, Khanna M. Direct targeting of TDP-43, from small molecules to biologics: the therapeutic landscape. RSC Chem Biol 2021; 2:1158-1166. [PMID: 34458829 PMCID: PMC8341936 DOI: 10.1039/d1cb00110h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 06/18/2021] [Indexed: 11/21/2022] Open
Abstract
Tar DNA binding (TDP)-43 proteinopathy, typically described as cytoplasmic accumulation of highly modified and misfolded TDP-43 molecules, is characteristic of several neurodegenerative diseases such as Amyotrophic Lateral Sclerosis (ALS) and limbic-predominant age-related TDP-43 encephalopathy (LATE). TDP-43 proposed proteinopathies include homeostatic imbalance between nuclear and cytoplasmic localization, aggregation of ubiquitinated and hyper-phosphorylated TDP-43, and an increase in protein truncation of cytoplasmic TDP-43. Given the therapeutic interest of targeting TDP-43, this review focuses on the current landscape of strategies, ranging from biologics to small molecules, that directly target TDP-43. Antibodies, peptides and compounds have been designed or found to recognize specific TDP-43 sequences but alleviate TDP-43 toxicity through different mechanisms. While two antibodies described here were able to induce degradation of pathological TDP-43, the peptides and small molecules were primarily designed to reduce aggregation of TDP-43. Furthermore, we discuss promising emerging therapeutic targets.
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Affiliation(s)
- Liberty Francois-Moutal
- Department of Pharmacology, College of Medicine, University of Arizona 1501 North Campbell Drive, P.O. Box 245050 Tucson AZ 85724 USA +520-626-2204 +520-626-2147
- Center of Innovation in Brain Science Tucson AZ 85721 USA
| | - David Donald Scott
- Department of Pharmacology, College of Medicine, University of Arizona 1501 North Campbell Drive, P.O. Box 245050 Tucson AZ 85724 USA +520-626-2204 +520-626-2147
- Center of Innovation in Brain Science Tucson AZ 85721 USA
| | - May Khanna
- Department of Pharmacology, College of Medicine, University of Arizona 1501 North Campbell Drive, P.O. Box 245050 Tucson AZ 85724 USA +520-626-2204 +520-626-2147
- Center of Innovation in Brain Science Tucson AZ 85721 USA
- Bio5 Institute, University of Arizona Tucson USA
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3
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Klingl YE, Pakravan D, Van Den Bosch L. Opportunities for histone deacetylase inhibition in amyotrophic lateral sclerosis. Br J Pharmacol 2021; 178:1353-1372. [PMID: 32726472 PMCID: PMC9327724 DOI: 10.1111/bph.15217] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 07/03/2020] [Accepted: 07/07/2020] [Indexed: 12/12/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease. ALS patients suffer from a progressive loss of motor neurons, leading to respiratory failure within 3 to 5 years after diagnosis. Available therapies only slow down the disease progression moderately or extend the lifespan by a few months. Epigenetic hallmarks have been linked to the disease, creating an avenue for potential therapeutic approaches. Interference with one class of epigenetic enzymes, histone deacetylases, has been shown to affect neurodegeneration in many preclinical models. Consequently, it is crucial to improve our understanding about histone deacetylases and their inhibitors in (pre)clinical models of ALS. We conclude that selective inhibitors with high tolerability and safety and sufficient blood-brain barrier permeability will be needed to interfere with both epigenetic and non-epigenetic targets of these enzymes. LINKED ARTICLES: This article is part of a themed issue on Neurochemistry in Japan. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.6/issuetoc.
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Affiliation(s)
- Yvonne E. Klingl
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI)KU Leuven‐University of LeuvenLeuvenBelgium
- Laboratory of NeurobiologyVIB, Center for Brain & Disease ResearchLeuvenBelgium
| | - Donya Pakravan
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI)KU Leuven‐University of LeuvenLeuvenBelgium
- Laboratory of NeurobiologyVIB, Center for Brain & Disease ResearchLeuvenBelgium
| | - Ludo Van Den Bosch
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute (LBI)KU Leuven‐University of LeuvenLeuvenBelgium
- Laboratory of NeurobiologyVIB, Center for Brain & Disease ResearchLeuvenBelgium
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Wang Y, Patani R. Novel therapeutic targets for amyotrophic lateral sclerosis: ribonucleoproteins and cellular autonomy. Expert Opin Ther Targets 2020; 24:971-984. [PMID: 32746659 DOI: 10.1080/14728222.2020.1805734] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Amyotrophic lateral sclerosis (ALS) is a devastating disease with a lifetime risk of approximately 1:400. It is incurable and invariably fatal. Average survival is between 3 and 5 years and patients become increasingly paralyzed, losing the ability to speak, eat, and breathe. Therapies in development either (i) target specific familial forms of ALS (comprising a minority of around 10% of cases) or ii) emanate from (over)reliance on animal models or non-human/non-neuronal cell models. There is a desperate and unmet clinical need for effective treatments. Deciphering the primacy and relative contributions of defective protein homeostasis and RNA metabolism in ALS across different model systems will facilitate the identification of putative therapeutic targets. AREAS COVERED This review examines the putative common primary molecular events that lead to ALS pathogenesis. We focus on deregulated RNA metabolism, protein mislocalization/pathological aggregation and the role of glia in ALS-related motor neuron degeneration. Finally, we describe promising targets for therapeutic evaluation. EXPERT OPINION Moving forward, an effective strategy could be achieved by a poly-therapeutic approach which targets both deregulated RNA metabolism and protein dyshomeostasis in the relevant cell types, at the appropriate phase of disease.
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Affiliation(s)
- Yiran Wang
- Department of Neuromuscular Diseases, Queen Square Institute of Neurology, University College London , London, UK.,Human Stem Cells and Neurodegeneration Laboratory, The Francis Crick Institute , London, UK
| | - Rickie Patani
- Department of Neuromuscular Diseases, Queen Square Institute of Neurology, University College London , London, UK.,Human Stem Cells and Neurodegeneration Laboratory, The Francis Crick Institute , London, UK
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5
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Proteotoxicity and Neurodegenerative Diseases. Int J Mol Sci 2020; 21:ijms21165646. [PMID: 32781742 PMCID: PMC7460676 DOI: 10.3390/ijms21165646] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 08/01/2020] [Accepted: 08/04/2020] [Indexed: 02/07/2023] Open
Abstract
Neurodegenerative diseases are a major burden for our society, affecting millions of people worldwide. A main goal of past and current research is to enhance our understanding of the mechanisms underlying proteotoxicity, a common theme among these incurable and debilitating conditions. Cell proteome alteration is considered to be one of the main driving forces that triggers neurodegeneration, and unraveling the biological complexity behind the affected molecular pathways constitutes a daunting challenge. This review summarizes the current state on key processes that lead to cellular proteotoxicity in Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, providing a comprehensive landscape of recent literature. A foundational understanding of how proteotoxicity affects disease etiology and progression may provide essential insight towards potential targets amenable of therapeutic intervention.
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6
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Buratti E. Targeting TDP-43 proteinopathy with drugs and drug-like small molecules. Br J Pharmacol 2020; 178:1298-1315. [PMID: 32469420 DOI: 10.1111/bph.15148] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 05/19/2020] [Accepted: 05/20/2020] [Indexed: 02/06/2023] Open
Abstract
Following the discovery of the involvement of the ribonucleoprotein TDP-43 in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD), a major research focus has been to develop treatments that can prevent or alleviate these disease conditions. One pharmacological approach has been to use TDP-43-based disease models to test small molecules and drugs already known to have some therapeutic effect in a variety of neurodegenerative conditions. In parallel, various disease models have been used to perform high-throughput screens of drugs and small compound libraries. The aim of this review will be to provide a general overview of the compounds that have been described to alter pathological characteristics of TDP-43. These include expression levels, cytoplasmic mis-localization, post-translational modifications, cleavage, stress granule recruitment and aggregation. In parallel, this review will also address the use of compounds that modify the autophagic/proteasome systems that are known to target TDP-43 misfolding and aggregation. LINKED ARTICLES: This article is part of a themed issue on Neurochemistry in Japan. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.6/issuetoc.
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Affiliation(s)
- Emanuele Buratti
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy
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7
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Loganathan S, Lehmkuhl EM, Eck RJ, Zarnescu DC. To Be or Not To Be…Toxic-Is RNA Association With TDP-43 Complexes Deleterious or Protective in Neurodegeneration? Front Mol Biosci 2020; 6:154. [PMID: 31998750 PMCID: PMC6965497 DOI: 10.3389/fmolb.2019.00154] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 12/12/2019] [Indexed: 12/13/2022] Open
Abstract
TAR DNA binding protein (TDP-43) is a nucleic acid binding protein associated with insoluble cytoplasmic aggregates in several neurodegenerative disorders, including 97% of the ALS cases. In healthy individuals, TDP-43 is primarily localized to the nucleus; it can shuttle between the nucleus and the cytoplasm, and is involved in several aspects of RNA processing including transcription, splicing, RNA stability, transport, localization, stress granule (SG) formation, and translation. Upon stress, TDP-43 aggregates in the cytoplasm and associates with several types of RNA and protein assemblies, resulting in nuclear depletion of TDP-43. Under conditions of prolonged stress, cytoplasmic TDP-43 undergoes liquid-liquid phase separation (LLPS) and becomes less mobile. Evidence exists to support a scenario in which insoluble TDP-43 complexes sequester RNA and/or proteins causing disturbances in both ribostasis and proteostasis, which in turn contribute to neurodegeneration. However, the relationship between RNA binding and TDP-43 toxicity remains unclear. Recent studies provide conflicting views on the role of RNA in TDP-43 toxicity, with some finding RNA as a toxic factor whereby RNA binding contributes to TDP-43 toxicity, while others find RNA to be a protective factor that inhibits TDP-43 aggregation. Here we review and discuss these recent reports, which ultimately highlight the importance of understanding the heterogeneity of TDP-43 assemblies and collectively point to solubilizing TDP-43 as a potential therapeutic strategy.
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Affiliation(s)
| | - Erik M Lehmkuhl
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, United States
| | - Randall J Eck
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, United States.,Department of Neuroscience, University of Arizona, Tucson, AZ, United States
| | - Daniela C Zarnescu
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, United States.,Department of Neuroscience, University of Arizona, Tucson, AZ, United States
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8
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Dios AM, Babu S, Granucci EJ, Mueller KA, Mills AN, Alshikho MJ, Zürcher NR, Cernasov P, Gilbert TM, Glass JD, Berry JD, Atassi N, Hooker JM, Sadri-Vakili G. Class I and II histone deacetylase expression is not altered in human amyotrophic lateral sclerosis: Neuropathological and positron emission tomography molecular neuroimaging evidence. Muscle Nerve 2019; 60:443-452. [PMID: 31241177 DOI: 10.1002/mus.26620] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 06/21/2019] [Accepted: 06/23/2019] [Indexed: 02/06/2023]
Abstract
INTRODUCTION There is an unmet need for mechanism-based biomarkers and effective disease modifying treatments in amyotrophic lateral sclerosis (ALS). Previous findings have provided evidence that histone deacetylases (HDAC) are altered in ALS, providing a rationale for testing HDAC inhibitors as a therapeutic option. METHODS We measured class I and II HDAC protein and transcript levels together with acetylation levels of downstream substrates by using Western blotting in postmortem tissue of ALS and controls. [11 C]Martinostat, a novel HDAC positron emission tomography ligand, was also used to assess in vivo brain HDAC alterations in patients with ALS and healthy controls (HC). RESULTS There was no significant difference in HDAC levels between patients with ALS and controls as measured by Western blotting and reverse-transcription quantitative polymerase chain reaction. Similarly, no differences were detected in [11 C]Martinostat-positron emission tomography uptake in ALS participants compared with HCs. DISCUSSION These findings provide evidence that alterations in HDAC isoforms are not a dominant pathological feature at the bulk tissue level in ALS.
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Affiliation(s)
- Amanda M Dios
- Sean M Healey & AMG Center for ALS at Mass General, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Suma Babu
- Sean M Healey & AMG Center for ALS at Mass General, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Eric J Granucci
- Sean M Healey & AMG Center for ALS at Mass General, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Kaly A Mueller
- Sean M Healey & AMG Center for ALS at Mass General, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Alexandra N Mills
- Sean M Healey & AMG Center for ALS at Mass General, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Mohamad J Alshikho
- Sean M Healey & AMG Center for ALS at Mass General, Massachusetts General Hospital, Boston, Massachusetts, USA.,Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
| | - Nicole R Zürcher
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
| | - Paul Cernasov
- Sean M Healey & AMG Center for ALS at Mass General, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Tonya M Gilbert
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
| | - Jonathan D Glass
- Department of Neurology, Emory University, Atlanta, Georgia, USA
| | - James D Berry
- Sean M Healey & AMG Center for ALS at Mass General, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Nazem Atassi
- Sean M Healey & AMG Center for ALS at Mass General, Massachusetts General Hospital, Boston, Massachusetts, USA.,Sanofi-Genzyme, Cambridge, Massachusetts, USA
| | - Jacob M Hooker
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
| | - Ghazaleh Sadri-Vakili
- Sean M Healey & AMG Center for ALS at Mass General, Massachusetts General Hospital, Boston, Massachusetts, USA
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9
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François-Moutal L, Felemban R, Scott DD, Sayegh MR, Miranda VG, Perez-Miller S, Khanna R, Gokhale V, Zarnescu DC, Khanna M. Small Molecule Targeting TDP-43's RNA Recognition Motifs Reduces Locomotor Defects in a Drosophila Model of Amyotrophic Lateral Sclerosis (ALS). ACS Chem Biol 2019; 14:2006-2013. [PMID: 31241884 DOI: 10.1021/acschembio.9b00481] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
RNA dysregulation likely contributes to disease pathogenesis of amyotrophic lateral sclerosis (ALS) and other neurodegenerative diseases. A pathological form of the transactive response (TAR) DNA binding protein (TDP-43) binds to RNA in stress granules and forms membraneless, amyloid-like TDP-43 aggregates in the cytoplasm of ALS motor neurons. In this study, we hypothesized that by targeting the RNA recognition motif (RRM) domains of TDP-43 that confer a pathogenic interaction between TDP-43 and RNA, motor neuron toxicity could be reduced. In silico docking of 50000 compounds to the RRM domains of TDP-43 identified a small molecule (rTRD01) that (i) bound to TDP-43's RRM1 and RRM2 domains, (ii) partially disrupted TDP-43's interaction with the hexanucleotide RNA repeat of the disease-linked c9orf72 gene, but not with (UG)6 canonical binding sequence of TDP-43, and (iii) improved larval turning, an assay measuring neuromuscular coordination and strength, in an ALS fly model based on the overexpression of mutant TDP-43. Our findings provide an instructive example of a chemical biology approach pivoted to discover small molecules targeting RNA-protein interactions in neurodegenerative diseases.
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Affiliation(s)
- Liberty François-Moutal
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona 85724, United States
- Center for Innovation in Brain Science, University of Arizona, Tucson, Arizona 85721, United States
| | - Razaz Felemban
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona 85724, United States
- Center for Innovation in Brain Science, University of Arizona, Tucson, Arizona 85721, United States
- King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard, Jeddah, Kingdom of Saudi Arabia
| | - David D. Scott
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona 85724, United States
- Center for Innovation in Brain Science, University of Arizona, Tucson, Arizona 85721, United States
| | - Melissa R. Sayegh
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, United States
- Department of Neuroscience, University of Arizona, Tucson, Arizona 85721, United States
- Department of Neurology, University of Arizona, Tucson Arizona 85721, United States
| | - Victor G. Miranda
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona 85724, United States
- Center for Innovation in Brain Science, University of Arizona, Tucson, Arizona 85721, United States
| | - Samantha Perez-Miller
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona 85724, United States
- Center for Innovation in Brain Science, University of Arizona, Tucson, Arizona 85721, United States
| | - Rajesh Khanna
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona 85724, United States
| | - Vijay Gokhale
- Bio5 Institute, University of Arizona, Tucson, Arizona 85721, United States
| | - Daniela C. Zarnescu
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, United States
- Department of Neuroscience, University of Arizona, Tucson, Arizona 85721, United States
- Department of Neurology, University of Arizona, Tucson Arizona 85721, United States
| | - May Khanna
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona 85724, United States
- Center for Innovation in Brain Science, University of Arizona, Tucson, Arizona 85721, United States
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10
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Nshogoza G, Liu Y, Gao J, Liu M, Moududee SA, Ma R, Li F, Zhang J, Wu J, Shi Y, Ruan K. NMR Fragment-Based Screening against Tandem RNA Recognition Motifs of TDP-43. Int J Mol Sci 2019; 20:ijms20133230. [PMID: 31262091 PMCID: PMC6651732 DOI: 10.3390/ijms20133230] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Revised: 06/27/2019] [Accepted: 06/28/2019] [Indexed: 01/10/2023] Open
Abstract
The TDP-43 is originally a nuclear protein but translocates to the cytoplasm in the pathological condition. TDP-43, as an RNA-binding protein, consists of two RNA Recognition Motifs (RRM1 and RRM2). RRMs are known to involve both protein-nucleotide and protein-protein interactions and mediate the formation of stress granules. Thus, they assist the entire TDP-43 protein with participating in neurodegenerative and cancer diseases. Consequently, they are potential therapeutic targets. Protein-observed and ligand-observed nuclear magnetic resonance (NMR) spectroscopy were used to uncover the small molecule inhibitors against the tandem RRM of TDP-43. We identified three hits weakly binding the tandem RRMs using the ligand-observed NMR fragment-based screening. The binding topology of these hits is then depicted by chemical shift perturbations (CSP) of the 15N-labeled tandem RRM and RRM2, respectively, and modeled by the CSP-guided High Ambiguity Driven biomolecular DOCKing (HADDOCK). These hits mainly bind to the RRM2 domain, which suggests the druggability of the RRM2 domain of TDP-43. These hits also facilitate further studies regarding the hit-to-lead evolution against the TDP-43 RRM domain.
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Affiliation(s)
- Gilbert Nshogoza
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Yaqian Liu
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Jia Gao
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Mingqing Liu
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Sayed Ala Moududee
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Rongsheng Ma
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Fudong Li
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Jiahai Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Jihui Wu
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Yunyu Shi
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
- CAS, Center for Excellence in Biomacromolecules, Chinese Academy of Sciences, Beijing 100101, China
| | - Ke Ruan
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China.
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11
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Yin P, Guo X, Yang W, Yan S, Yang S, Zhao T, Sun Q, Liu Y, Li S, Li XJ. Caspase-4 mediates cytoplasmic accumulation of TDP-43 in the primate brains. Acta Neuropathol 2019; 137:919-937. [PMID: 30810811 PMCID: PMC6531422 DOI: 10.1007/s00401-019-01979-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/20/2019] [Accepted: 02/21/2019] [Indexed: 12/12/2022]
Abstract
The cytoplasmic accumulation of the nuclear TAR DNA-binding protein 43 (TDP-43) is a pathologic hallmark in amyotrophic lateral sclerosis, frontotemporal lobar degeneration, and other neurological disorders. However, most transgenic TDP-43 rodent models show predominant nuclear distribution of TDP-43 in the brain. By expressing mutant TDP-43 (M337V) in the brains of rhesus monkeys and mice, we verified that mutant TDP-43 is distributed in the cytoplasm of the monkey brain and that the majority of mutant TDP-43 remains in the nuclei of the mouse brain. The primate-specific caspase-4, but not mouse homologue caspase-11, could remove the NLS-containing N-terminal domain and generate fragmented TDP-43 that accumulates in the cytoplasm. Moreover, increased expression of caspase-4 in the monkey brain promotes the cytoplasmic accumulation of endogenous TDP-43, and suppressing caspase-4 reduces the cytoplasmic distribution of endogenous TDP-43 in cultured human neural cells. Our findings suggest that primate-specific caspase-4-mediated cleavage of TDP-43 accounts for its cytoplasmic mislocalization in the primate brains and may serve as a potential therapeutic target.
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Affiliation(s)
- Peng Yin
- Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Guangdong-Hongkong-Macau Institute of CNS Regeneration, Jinan University, Guangzhou, 510632, China
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Xiangyu Guo
- Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Guangdong-Hongkong-Macau Institute of CNS Regeneration, Jinan University, Guangzhou, 510632, China
| | - Weili Yang
- Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Guangdong-Hongkong-Macau Institute of CNS Regeneration, Jinan University, Guangzhou, 510632, China
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Sen Yan
- Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Guangdong-Hongkong-Macau Institute of CNS Regeneration, Jinan University, Guangzhou, 510632, China
| | - Su Yang
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Ting Zhao
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Qiang Sun
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yunbo Liu
- Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100021, China.
| | - Shihua Li
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, 30322, USA.
| | - Xiao-Jiang Li
- Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Guangdong-Hongkong-Macau Institute of CNS Regeneration, Jinan University, Guangzhou, 510632, China.
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, 30322, USA.
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Berning BA, Walker AK. The Pathobiology of TDP-43 C-Terminal Fragments in ALS and FTLD. Front Neurosci 2019; 13:335. [PMID: 31031584 PMCID: PMC6470282 DOI: 10.3389/fnins.2019.00335] [Citation(s) in RCA: 106] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 03/22/2019] [Indexed: 12/11/2022] Open
Abstract
During neurodegenerative disease, the multifunctional RNA-binding protein TDP-43 undergoes a vast array of post-translational modifications, including phosphorylation, acetylation, and cleavage. Many of these alterations may directly contribute to the pathogenesis of TDP-43 proteinopathies, which include most forms of amyotrophic lateral sclerosis (ALS) and approximately half of all frontotemporal dementia, pathologically identified as frontotemporal lobar degeneration (FTLD) with TDP-43 pathology. However, the relative contributions of the various TDP-43 post-translational modifications to disease remain unclear, and indeed some may be secondary epiphenomena rather than disease-causative. It is therefore critical to determine the involvement of each modification in disease processes to allow the design of targeted treatments. In particular, TDP-43 C-terminal fragments (CTFs) accumulate in the brains of people with ALS and FTLD and are therefore described as a neuropathological signature of these diseases. Remarkably, these TDP-43 CTFs are rarely observed in the spinal cord, even in ALS which involves dramatic degeneration of spinal motor neurons. Therefore, TDP-43 CTFs are not produced non-specifically in the course of all forms of TDP-43-related neurodegeneration, but rather variably arise due to additional factors influenced by regional heterogeneity in the central nervous system. In this review, we summarize how TDP-43 CTFs are generated and degraded by cells, and critique evidence from studies of TDP-43 CTF pathology in human disease tissues, as well as cell and animal models, to analyze the pathophysiological relevance of TDP-43 CTFs to ALS and FTLD. Numerous studies now indicate that, although TDP-43 CTFs are prevalent in ALS and FTLD brains, disease-related pathology is only variably reproduced in TDP-43 CTF cell culture models. Furthermore, TDP-43 CTF expression in both transgenic and viral-mediated in vivo models largely fails to induce motor or behavioral dysfunction reminiscent of human disease. We therefore conclude that although TDP-43 CTFs are a hallmark of TDP-43-related neurodegeneration in the brain, they are not a primary cause of ALS or FTLD.
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Affiliation(s)
- Britt A. Berning
- Neurodegeneration Pathobiology Laboratory, Queensland Brain Institute, University of Queensland, Brisbane, QLD, Australia
| | - Adam K. Walker
- Neurodegeneration Pathobiology Laboratory, Queensland Brain Institute, University of Queensland, Brisbane, QLD, Australia
- Centre for Motor Neuron Disease Research, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, North Ryde, NSW, Australia
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13
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Prasad A, Bharathi V, Sivalingam V, Girdhar A, Patel BK. Molecular Mechanisms of TDP-43 Misfolding and Pathology in Amyotrophic Lateral Sclerosis. Front Mol Neurosci 2019; 12:25. [PMID: 30837838 PMCID: PMC6382748 DOI: 10.3389/fnmol.2019.00025] [Citation(s) in RCA: 417] [Impact Index Per Article: 83.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 01/21/2019] [Indexed: 12/11/2022] Open
Abstract
TAR DNA binding protein 43 (TDP-43) is a versatile RNA/DNA binding protein involved in RNA-related metabolism. Hyper-phosphorylated and ubiquitinated TDP-43 deposits act as inclusion bodies in the brain and spinal cord of patients with the motor neuron diseases: amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). While the majority of ALS cases (90-95%) are sporadic (sALS), among familial ALS cases 5-10% involve the inheritance of mutations in the TARDBP gene and the remaining (90-95%) are due to mutations in other genes such as: C9ORF72, SOD1, FUS, and NEK1 etc. Strikingly however, the majority of sporadic ALS patients (up to 97%) also contain the TDP-43 protein deposited in the neuronal inclusions, which suggests of its pivotal role in the ALS pathology. Thus, unraveling the molecular mechanisms of the TDP-43 pathology seems central to the ALS therapeutics, hence, we comprehensively review the current understanding of the TDP-43's pathology in ALS. We discuss the roles of TDP-43's mutations, its cytoplasmic mis-localization and aberrant post-translational modifications in ALS. Also, we evaluate TDP-43's amyloid-like in vitro aggregation, its physiological vs. pathological oligomerization in vivo, liquid-liquid phase separation (LLPS), and potential prion-like propagation propensity of the TDP-43 inclusions. Finally, we describe the various evolving TDP-43-induced toxicity mechanisms, such as the impairment of endocytosis and mitotoxicity etc. and also discuss the emerging strategies toward TDP-43 disaggregation and ALS therapeutics.
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Affiliation(s)
| | | | | | | | - Basant K. Patel
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Sangareddy, India
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14
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Hu Y, Ge W, Wang X, Sutendra G, Zhao K, Dedeić Z, Slee EA, Baer C, Lu X. Caspase cleavage of iASPP potentiates its ability to inhibit p53 and NF-κB. Oncotarget 2015; 6:42478-90. [PMID: 26646590 PMCID: PMC4767446 DOI: 10.18632/oncotarget.6478] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 11/25/2015] [Indexed: 12/14/2022] Open
Abstract
An intriguing biological question relating to cell signaling is how the inflammatory mediator NF-kB and the tumour suppressor protein p53 can be induced by similar triggers, like DNA damage or infection, yet have seemingly opposing or sometimes cooperative biological functions. For example, the NF-κB subunit RelA/p65 has been shown to inhibit apoptosis, whereas p53 induces apoptosis. One potential explanation may be their co-regulation by common cellular factors: inhibitor of Apoptosis Stimulating p53 Protein (iASPP) is one such common regulator of both RelA/p65 and p53. Here we show that iASPP is a novel substrate of caspases in response to apoptotic stimuli. Caspase cleaves the N-terminal region of iASPP at SSLD294 resulting in a prominent 80kDa fragment of iASPP. This caspase cleavage site is conserved in various species from zebrafish to Homo sapiens. The 80kDa fragment of iASPP translocates from the cytoplasm to the nucleus via the RaDAR nuclear import pathway, independent of p53. The 80kDa iASPP fragment can bind and inhibit p53 or RelA/p65 more efficiently than full-length iASPP. Overall, these data reveal a potential novel regulation of p53 and RelA/p65 activities in response to apoptotic stimuli.
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Affiliation(s)
- Ying Hu
- The School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
- Ludwig Institute for Cancer Research Ltd., Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Wenjie Ge
- The School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Xingwen Wang
- The School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Gopinath Sutendra
- Ludwig Institute for Cancer Research Ltd., Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Kunming Zhao
- The School of Life Science and Technology, Harbin Institute of Technology, Harbin, China
| | - Zinaida Dedeić
- Ludwig Institute for Cancer Research Ltd., Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Elizabeth A. Slee
- Ludwig Institute for Cancer Research Ltd., Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Caroline Baer
- Ludwig Institute for Cancer Research Ltd., Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Xin Lu
- Ludwig Institute for Cancer Research Ltd., Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
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15
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Coyne AN, Yamada SB, Siddegowda BB, Estes PS, Zaepfel BL, Johannesmeyer JS, Lockwood DB, Pham LT, Hart MP, Cassel JA, Freibaum B, Boehringer AV, Taylor JP, Reitz AB, Gitler AD, Zarnescu DC. Fragile X protein mitigates TDP-43 toxicity by remodeling RNA granules and restoring translation. Hum Mol Genet 2015; 24:6886-98. [PMID: 26385636 DOI: 10.1093/hmg/ddv389] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 09/14/2015] [Indexed: 12/12/2022] Open
Abstract
RNA dysregulation is a newly recognized disease mechanism in amyotrophic lateral sclerosis (ALS). Here we identify Drosophila fragile X mental retardation protein (dFMRP) as a robust genetic modifier of TDP-43-dependent toxicity in a Drosophila model of ALS. We find that dFMRP overexpression (dFMRP OE) mitigates TDP-43 dependent locomotor defects and reduced lifespan in Drosophila. TDP-43 and FMRP form a complex in flies and human cells. In motor neurons, TDP-43 expression increases the association of dFMRP with stress granules and colocalizes with polyA binding protein in a variant-dependent manner. Furthermore, dFMRP dosage modulates TDP-43 solubility and molecular mobility with overexpression of dFMRP resulting in a significant reduction of TDP-43 in the aggregate fraction. Polysome fractionation experiments indicate that dFMRP OE also relieves the translation inhibition of futsch mRNA, a TDP-43 target mRNA, which regulates neuromuscular synapse architecture. Restoration of futsch translation by dFMRP OE mitigates Futsch-dependent morphological phenotypes at the neuromuscular junction including synaptic size and presence of satellite boutons. Our data suggest a model whereby dFMRP is neuroprotective by remodeling TDP-43 containing RNA granules, reducing aggregation and restoring the translation of specific mRNAs in motor neurons.
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Affiliation(s)
- Alyssa N Coyne
- Department of Molecular and Cellular Biology, Department of Neuroscience
| | | | | | | | | | | | - Donovan B Lockwood
- Department of Molecular and Cellular Biology, Department of Neuroscience
| | - Linh T Pham
- Department of Molecular and Cellular Biology
| | - Michael P Hart
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | | | - Brian Freibaum
- Department of Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Ashley V Boehringer
- Department of Molecular and Cellular Biology, Department of Neuroscience, Department of Neurology, University of Arizona, Tucson, AZ, USA
| | - J Paul Taylor
- Department of Neurobiology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | | | - Aaron D Gitler
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | - Daniela C Zarnescu
- Department of Molecular and Cellular Biology, Department of Neuroscience, Department of Neurology, University of Arizona, Tucson, AZ, USA,
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Nan YN, Zhu JY, Tan Y, Zhang Q, Jia W, Hua Q. Staurosporine induced apoptosis rapidly downregulates TDP- 43 in glioma cells. Asian Pac J Cancer Prev 2015; 15:3575-9. [PMID: 24870760 DOI: 10.7314/apjcp.2014.15.8.3575] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
TDP-43 is a ubiquitously expressed DNA/RNA binding protein that has recently attracted attention for its involvement in neurodegenerative diseases. While TDP-43 has been found to participate in various important cellular activities including stress and apoptosis, little is known about its role in cancer cells. Here we report that staurosporine (STS) induced apoptosis in U87 glioma cells is associated with rapid downregulation of TDP-43 at both mRNA and protein levels. The latter is dependent on activation of caspase 3. More importantly, we have shown that knockdown of TDP-43 by specific siRNA dramatically enhanced cytotoxicity of STS. These results suggest that normal level of TDP-43 may be protective for cancer cells under apoptotic insult.
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Affiliation(s)
- Yi-Nan Nan
- School of Preclinical Medicine, Center Laboratory, Beijing University of Chinese Medicine, Beijing, China E-mail : ;
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17
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Budini M, Baralle FE, Buratti E. Targeting TDP-43 in neurodegenerative diseases. Expert Opin Ther Targets 2014; 18:617-32. [DOI: 10.1517/14728222.2014.896905] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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18
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De Marco G, Lomartire A, Mandili G, Lupino E, Buccinnà B, Ramondetti C, Moglia C, Novelli F, Piccinini M, Mostert M, Rinaudo MT, Chiò A, Calvo A. Reduced cellular Ca(2+) availability enhances TDP-43 cleavage by apoptotic caspases. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:725-34. [PMID: 24440855 DOI: 10.1016/j.bbamcr.2014.01.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 12/20/2013] [Accepted: 01/08/2014] [Indexed: 12/13/2022]
Abstract
Accumulation of transactive response DNA binding protein (TDP-43) fragments in motor neurons is a post mortem hallmark of different neurodegenerative diseases. TDP-43 fragments are the products of the apoptotic caspases-3 and -7. Either excessive or insufficient cellular Ca(2+) availability is associated with activation of apoptotic caspases. However, as far as we know, it is not described whether activation of caspases, due to restricted intracellular Ca(2+), affects TDP-43 cleavage. Here we show that in various cell lineages with restricted Ca(2+) availability, TDP-43 is initially cleaved by caspases-3 and -7 and then, also by caspases-6 and -8 once activated by caspase-3. Furthermore, we disclose the existence of a TDP-43 caspase-mediated fragment of 15kDa, in addition to the well-known fragments of 35 and 25kDa. Interestingly, with respect to the other two fragments this novel fragment is the major product of caspase activity on murine TDP-43 whereas in human cell lines the opposite occurs. This outcome should be considered when murine models are used to investigate TDP-43 proteinopathies.
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Affiliation(s)
- Giovanni De Marco
- 'Rita Levi Montalcini' Department of Neuroscience, University of Turin, Turin, Italy; Department of Oncology, University of Turin, Turin, Italy
| | - Annarosa Lomartire
- 'Rita Levi Montalcini' Department of Neuroscience, University of Turin, Turin, Italy; Department of Oncology, University of Turin, Turin, Italy
| | - Giorgia Mandili
- Center for Experimental Research and Medical Studies (CeRMS), University of Turin, Turin, Italy; Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | - Elisa Lupino
- Department of Oncology, University of Turin, Turin, Italy
| | | | | | - Cristina Moglia
- 'Rita Levi Montalcini' Department of Neuroscience, University of Turin, Turin, Italy; CRESLA Turin, AOU Città della Salute e della Scienza, Turin, Italy
| | - Francesco Novelli
- Center for Experimental Research and Medical Studies (CeRMS), University of Turin, Turin, Italy; Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | | | - Michael Mostert
- Department of Public Health and Pediatric Sciences, University of Turin, Turin, Italy
| | | | - Adriano Chiò
- 'Rita Levi Montalcini' Department of Neuroscience, University of Turin, Turin, Italy; CRESLA Turin, AOU Città della Salute e della Scienza, Turin, Italy
| | - Andrea Calvo
- 'Rita Levi Montalcini' Department of Neuroscience, University of Turin, Turin, Italy; CRESLA Turin, AOU Città della Salute e della Scienza, Turin, Italy
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Limpert AS, Mattmann ME, Cosford NDP. Recent progress in the discovery of small molecules for the treatment of amyotrophic lateral sclerosis (ALS). Beilstein J Org Chem 2013; 9:717-32. [PMID: 23766784 PMCID: PMC3678841 DOI: 10.3762/bjoc.9.82] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 03/07/2013] [Indexed: 12/13/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder with few therapeutic options. While several gene mutations have been implicated in ALS, the exact cause of neuronal dysfunction is unknown and motor neurons of affected individuals display numerous cellular abnormalities. Ongoing efforts to develop novel ALS treatments involve the identification of small molecules targeting specific mechanisms of neuronal pathology, including glutamate excitotoxicity, mutant protein aggregation, endoplasmic reticulum (ER) stress, loss of trophic factors, oxidative stress, or neuroinflammation. Herein, we review recent advances in the discovery and preclinical characterization of lead compounds that may ultimately provide novel drugs to treat patients suffering from ALS.
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Affiliation(s)
- Allison S Limpert
- Apoptosis and Cell Death Research Program, Sanford-Burnham Medical Research Institute, 10901 N. Torrey Pines Road, La Jolla, California 92037, United States
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20
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Cassel JA, Reitz AB. Ubiquilin-2 (UBQLN2) binds with high affinity to the C-terminal region of TDP-43 and modulates TDP-43 levels in H4 cells: characterization of inhibition by nucleic acids and 4-aminoquinolines. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:964-71. [PMID: 23541532 DOI: 10.1016/j.bbapap.2013.03.020] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 03/18/2013] [Accepted: 03/20/2013] [Indexed: 12/13/2022]
Abstract
Recently, it was reported that mutations in the ubiquitin-like protein ubiquilin-2 (UBQLN2) are associated with X-linked amyotrophic lateral sclerosis (ALS), and that both wild-type and mutant UBQLN2 can co-localize with aggregates of C-terminal fragments of TAR DNA binding protein (TDP-43). Here, we describe a high affinity interaction between UBQLN2 and TDP-43 and demonstrate that overexpression of both UBQLN2 and TDP-43 reduces levels of both exogenous and endogenous TDP-43 in human H4 cells. UBQLN2 bound with high affinity to both full length TDP-43 and a C-terminal TDP-43 fragment (261-414 aa) with KD values of 6.2nM and 8.7nM, respectively. Both DNA oligonucleotides and 4-aminoquinolines, which bind to TDP-43, also inhibited UBQLN2 binding to TDP-43 with similar rank order affinities compared to inhibition of oligonucleotide binding to TDP-43. Inhibitor characterization experiments demonstrated that the DNA oligonucleotides noncompetitively inhibited UBQLN2 binding to TDP-43, which is consistent with UBQLN2 binding to the C-terminal region of TDP-43. Interestingly, the 4-aminoquinolines were competitive inhibitors of UBQLN2 binding to TDP-43, suggesting that these compounds also bind to the C-terminal region of TDP-43. In support of the biochemical data, co-immunoprecipitation experiments demonstrated that both TDP-43 and UBQLN2 interact in human neuroglioma H4 cells. Finally, overexpression of UBQLN2 in the presence of overexpressed full length TDP-43 or C-terminal TDP-43 (170-414) dramatically lowered levels of both full length TDP-43 and C-terminal TDP-43 fragments (CTFs). Consequently, these data suggest that UBQLN2 enhances the clearance of TDP-43 and TDP-43 CTFs and therefore may play a role in the development of TDP-43 associated neurotoxicity.
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Mechanistic evaluation of a novel small molecule targeting mitochondria in pancreatic cancer cells. PLoS One 2013; 8:e54346. [PMID: 23349858 PMCID: PMC3549929 DOI: 10.1371/journal.pone.0054346] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 12/12/2012] [Indexed: 12/25/2022] Open
Abstract
Background Pancreatic cancer is one of the deadliest cancers with a 5-year survival rate of 6%. Therapeutic options are very limited and there is an unmet medical need for safe and efficacious treatments. Cancer cell metabolism and mitochondria provide unexplored targets for this disease. We recently identified a novel class of triphenylphosphonium salts, TP compounds, with broad- spectrum anticancer properties. We examined the ability of our prototypical compound TP421– chosen for its fluorescent properties – to inhibit the growth of pancreatic cancer cells and further investigated the molecular mechanisms by which it exerts its anticancer effects. Methodology/Principal Findings TP421 exhibited sub-micromolar IC50 values in all the pancreatic cancer cell lines tested using MTT and colony formation assays. TP421 localized predominantly to mitochondria and induced G0/G1 arrest, ROS accumulation, and activation of several stress-regulated kinases. Caspase and PARP-1 cleavage were observed indicating an apoptotic response while LC3B-II and p62 were accumulated indicating inhibition of autophagy. Furthermore, TP421 induced de-phosphorylation of key signaling molecules involved in FAK mediated adhesion that correlated with inhibition of cell migration. Conclusions/Significance TP421 is a representative compound of a new promising class of mitochondrial-targeted agents useful for pancreatic cancer treatment. Because of their unique mechanism of action and efficacy further development is warranted.
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