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Daniels N, Bindoff AD, Vickers JC, King AE, Collins JM. Vulnerability of neurofilament-expressing neurons in frontotemporal dementia. Mol Cell Neurosci 2024:103974. [PMID: 39369804 DOI: 10.1016/j.mcn.2024.103974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2024] [Revised: 09/23/2024] [Accepted: 09/30/2024] [Indexed: 10/08/2024] Open
Abstract
Frontotemporal dementia (FTD) is an umbrella term for several early onset dementias, that are caused by frontotemporal lobar degeneration (FTLD), which involves the atrophy of the frontal and temporal lobes of the brain. Neuron loss in the frontal and temporal lobes is a characteristic feature of FTLD, however the selective vulnerability of different neuronal populations in this group of diseases is not fully understood. Neurofilament-expressing neurons have been shown to be selectively vulnerable in other neurodegenerative diseases, including Alzheimer's disease and amyotrophic lateral sclerosis, therefore we sought to investigate whether this neuronal population is vulnerable in FTLD. We also examined whether neuronal sub-type vulnerability differed between FTLD with TDP-43 inclusions (FTLD-TDP) and FTLD with tau inclusions (FTLD-Tau). Post-mortem human tissue from the superior frontal gyrus (SFG) of FTLD-TDP (n = 15), FTLD-Tau (n = 8) and aged Control cases (n = 6) was immunolabelled using antibodies against non-phosphorylated neurofilaments (SMI32 antibody), calretinin and NeuN, to explore neuronal cell loss. The presence of non-phosphorylated neurofilament immunolabelling in axons of the SFG white matter was also quantified as a measure of axon pathology, as axonal neurofilaments are normally phosphorylated. We demonstrate the selective loss of neurofilament-expressing neurons in both FTLD-TDP and FTLD-Tau cases compared to aged Controls. We also show that non-phosphorylated neurofilament axonal pathology in the SFG white matter was associated with increasing age, but not FTLD. This data suggests neurofilament-expressing neurons are vulnerable in both FTLD-TDP and FTLD-Tau.
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Affiliation(s)
- Nina Daniels
- Wicking Dementia Research and Education Centre, University of Tasmania, Hobart, Tasmania, Australia.
| | - Aidan D Bindoff
- Wicking Dementia Research and Education Centre, University of Tasmania, Hobart, Tasmania, Australia
| | - James C Vickers
- Wicking Dementia Research and Education Centre, University of Tasmania, Hobart, Tasmania, Australia
| | - Anna E King
- Wicking Dementia Research and Education Centre, University of Tasmania, Hobart, Tasmania, Australia
| | - Jessica M Collins
- Wicking Dementia Research and Education Centre, University of Tasmania, Hobart, Tasmania, Australia
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2
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Lefebvre-Omar C, Liu E, Dalle C, d'Incamps BL, Bigou S, Daube C, Karpf L, Davenne M, Robil N, Jost Mousseau C, Blanchard S, Tournaire G, Nicaise C, Salachas F, Lacomblez L, Seilhean D, Lobsiger CS, Millecamps S, Boillée S, Bohl D. Neurofilament accumulations in amyotrophic lateral sclerosis patients' motor neurons impair axonal initial segment integrity. Cell Mol Life Sci 2023; 80:150. [PMID: 37184603 DOI: 10.1007/s00018-023-04797-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 04/24/2023] [Accepted: 05/03/2023] [Indexed: 05/16/2023]
Abstract
Amyotrophic lateral sclerosis (ALS) is the most common motor neuron (MN) disease in adults with no curative treatment. Neurofilament (NF) level in patient' fluids have recently emerged as the prime biomarker of ALS disease progression, while NF accumulation in MNs of patients is the oldest and one of the best pathological hallmarks. However, the way NF accumulations could lead to MN degeneration remains unknown. To assess NF accumulations and study the impact on MNs, we compared MNs derived from induced pluripotent stem cells (iPSC) of patients carrying mutations in C9orf72, SOD1 and TARDBP genes, the three main ALS genetic causes. We show that in all mutant MNs, light NF (NF-L) chains rapidly accumulate in MN soma, while the phosphorylated heavy/medium NF (pNF-M/H) chains pile up in axonal proximal regions of only C9orf72 and SOD1 MNs. Excitability abnormalities were also only observed in these latter MNs. We demonstrate that the integrity of the MN axonal initial segment (AIS), the region of action potential initiation and responsible for maintaining axonal integrity, is impaired in the presence of pNF-M/H accumulations in C9orf72 and SOD1 MNs. We establish a strong correlation between these pNF-M/H accumulations, an AIS distal shift, increased axonal calibers and modified repartition of sodium channels. The results expand our understanding of how NF accumulation could dysregulate components of the axonal cytoskeleton and disrupt MN homeostasis. With recent cumulative evidence that AIS alterations are implicated in different brain diseases, preserving AIS integrity could have important therapeutic implications for ALS.
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Affiliation(s)
- Cynthia Lefebvre-Omar
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Elise Liu
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Carine Dalle
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Boris Lamotte d'Incamps
- Université Paris-Cité, CNRS, Saints-Pères Paris Institute for the Neurosciences, Paris, France
| | - Stéphanie Bigou
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Clément Daube
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Léa Karpf
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Marc Davenne
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | | | - Coline Jost Mousseau
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Stéphane Blanchard
- Institut Pasteur, INSERM U1115, Unité Biothérapies pour les Maladies Neurodégénératives, Paris, France
| | - Guillaume Tournaire
- Institut Pasteur, INSERM U1115, Unité Biothérapies pour les Maladies Neurodégénératives, Paris, France
| | | | - François Salachas
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
- Département de Neurologie, Assistance Publique Hôpitaux de Paris (APHP), Centre de Référence SLA Ile de France, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Lucette Lacomblez
- Département de Neurologie, Assistance Publique Hôpitaux de Paris (APHP), Centre de Référence SLA Ile de France, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Danielle Seilhean
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
- Département de Neuropathologie, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Christian S Lobsiger
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Stéphanie Millecamps
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Séverine Boillée
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Delphine Bohl
- Sorbonne Université, Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, AP-HP, Hôpital de la Pitié-Salpêtrière, Paris, France.
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Kumar S, Phaneuf D, Cordeau P, Boutej H, Kriz J, Julien JP. Induction of autophagy mitigates TDP-43 pathology and translational repression of neurofilament mRNAs in mouse models of ALS/FTD. Mol Neurodegener 2021; 16:1. [PMID: 33413517 PMCID: PMC7792109 DOI: 10.1186/s13024-020-00420-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 12/14/2020] [Indexed: 12/11/2022] Open
Abstract
Background TDP-43 proteinopathy is a pathological hallmark of many neurodegenerative diseases including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). So far, there is no therapy available for these neurodegenerative diseases. In addition, the impact of TDP-43 proteinopathy on neuronal translational profile also remains unknown. Methods Biochemical, immunohistology and assay-based studies were done with cell cultures and transgenic mice models. We also used Ribotag with microarray and proteomic analysis to determine the neuronal translational profile in the mice model of ALS/FTD. Results Here, we report that oral administration of a novel analog (IMS-088) of withaferin-A, an antagonist of nuclear factor kappa-B (NF-ĸB) essential modulator (NEMO), induced autophagy and reduced TDP-43 proteinopathy in the brain and spinal cord of transgenic mice expressing human TDP-43 mutants, models of ALS/FTD. Treatment with IMS-088 ameliorated cognitive impairment, reduced gliosis in the brain of ALS/FTD mouse models. With the Ribotrap method, we investigated the impact of TDP-43 proteinopathy and IMS-088 treatment on the translation profile of neurons of one-year old hTDP-43A315T mice. TDP-43 proteinopathy caused translational dysregulation of specific mRNAs including translational suppression of neurofilament mRNAs resulting in 3 to 4-fold decrease in levels type IV neurofilament proteins. Oral administration of IMS-088 rescued the translational defects associated with TDP-43 proteinopathy and restored the synthesis of neurofilament proteins, which are essential for axon integrity and synaptic function. Conclusions Our study revealed that induction of autophagy reduces TDP-43 pathology and ameliorates the translational defect seen in mice models of ALS/FTD. Based on these results, we suggest IMS-088 and perhaps other inducers of autophagy should be considered as potential therapeutics for neurodegenerative disorders with TDP-43 proteinopathies. Supplementary Information The online version contains supplementary material available at 10.1186/s13024-020-00420-5.
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Affiliation(s)
- Sunny Kumar
- Department of Psychiatry and Neuroscience, CERVO Brain Research Centre, University Laval, 2601, Chemin de la Canardière, Quebec City, QC, G1J 2G3, Canada
| | - Daniel Phaneuf
- Department of Psychiatry and Neuroscience, CERVO Brain Research Centre, University Laval, 2601, Chemin de la Canardière, Quebec City, QC, G1J 2G3, Canada
| | - Pierre Cordeau
- Department of Psychiatry and Neuroscience, CERVO Brain Research Centre, University Laval, 2601, Chemin de la Canardière, Quebec City, QC, G1J 2G3, Canada
| | - Hejer Boutej
- Department of Psychiatry and Neuroscience, CERVO Brain Research Centre, University Laval, 2601, Chemin de la Canardière, Quebec City, QC, G1J 2G3, Canada
| | - Jasna Kriz
- Department of Psychiatry and Neuroscience, CERVO Brain Research Centre, University Laval, 2601, Chemin de la Canardière, Quebec City, QC, G1J 2G3, Canada
| | - Jean-Pierre Julien
- Department of Psychiatry and Neuroscience, CERVO Brain Research Centre, University Laval, 2601, Chemin de la Canardière, Quebec City, QC, G1J 2G3, Canada.
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Moll T, Shaw PJ, Cooper-Knock J. Disrupted glycosylation of lipids and proteins is a cause of neurodegeneration. Brain 2020; 143:1332-1340. [PMID: 31724708 PMCID: PMC7241952 DOI: 10.1093/brain/awz358] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 09/10/2019] [Accepted: 09/16/2019] [Indexed: 12/13/2022] Open
Abstract
Glycosyltransferases represent a large family of enzymes that catalyse the biosynthesis of oligosaccharides, polysaccharides, and glycoconjugates. A number of studies have implicated glycosyltransferases in the pathogenesis of neurodegenerative diseases but differentiating cause from effect has been difficult. We have recently discovered that mutations proximal to the substrate binding site of glycosyltransferase 8 domain containing 1 (GLT8D1) are associated with familial amyotrophic lateral sclerosis (ALS). We demonstrated that ALS-associated mutations reduce activity of the enzyme suggesting a loss-of-function mechanism that is an attractive therapeutic target. Our work is the first evidence that isolated dysfunction of a glycosyltransferase is sufficient to cause a neurodegenerative disease, but connection between neurodegeneration and genetic variation within glycosyltransferases is not new. Previous studies have identified associations between mutations in UGT8 and sporadic ALS, and between ST6GAL1 mutations and conversion of mild cognitive impairment into clinical Alzheimer’s disease. In this review we consider potential mechanisms connecting glycosyltransferase dysfunction to neurodegeneration. The most prominent candidates are ganglioside synthesis and impaired addition of O-linked β-N-acetylglucosamine (O-GlcNAc) groups to proteins important for axonal and synaptic function. Special consideration is given to examples where genetic mutations within glycosyltransferases are associated with neurodegeneration in recognition of the fact that these changes are likely to be upstream causes present from birth.
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Affiliation(s)
- Tobias Moll
- Sheffield Institute for Translational Neuroscience (SITraN), Sheffield, UK
| | - Pamela J Shaw
- Sheffield Institute for Translational Neuroscience (SITraN), Sheffield, UK
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5
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Castellanos-Montiel MJ, Chaineau M, Durcan TM. The Neglected Genes of ALS: Cytoskeletal Dynamics Impact Synaptic Degeneration in ALS. Front Cell Neurosci 2020; 14:594975. [PMID: 33281562 PMCID: PMC7691654 DOI: 10.3389/fncel.2020.594975] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 10/21/2020] [Indexed: 12/11/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that selectively affects motor neurons (MNs) of the cortex, brainstem, and spinal cord. Several genes have been linked to both familial (fALS) and sporadic (sALS) cases of ALS. Among all the ALS-related genes, a group of genes known to directly affect cytoskeletal dynamics (ALS2, DCTN1, PFN1, KIF5A, NF-L, NF-H, PRPH, SPAST, and TUBA4A) is of high importance for MN health and survival, considering that MNs are large polarized cells with axons that can reach up to 1 m in length. In particular, cytoskeletal dynamics facilitate the transport of organelles and molecules across the long axonal distances within the cell, playing a key role in synapse maintenance. The majority of ALS-related genes affecting cytoskeletal dynamics were identified within the past two decades, making it a new area to explore for ALS. The purpose of this review is to provide insights into ALS-associated cytoskeletal genes and outline how recent studies have pointed towards novel pathways that might be impacted in ALS. Further studies making use of extensive analysis models to look for true hits, the newest technologies such as CRIPSR/Cas9, human induced pluripotent stem cells (iPSCs) and axon sequencing, as well as the development of more transgenic animal models could potentially help to: differentiate the variants that truly act as a primary cause of the disease from the ones that act as risk factors or disease modifiers, identify potential interactions between two or more ALS-related genes in disease onset and progression and increase our understanding of the molecular mechanisms leading to cytoskeletal defects. Altogether, this information will give us a hint on the real contribution of the cytoskeletal ALS-related genes during this lethal disease.
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Affiliation(s)
| | - Mathilde Chaineau
- Early Drug Discovery Unit (EDDU), Montreal Neurological Institute-Hospital, McGill University, Montreal, QC, Canada
| | - Thomas M Durcan
- Early Drug Discovery Unit (EDDU), Montreal Neurological Institute-Hospital, McGill University, Montreal, QC, Canada
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6
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Zucchi E, Lu CH, Cho Y, Chang R, Adiutori R, Zubiri I, Ceroni M, Cereda C, Pansarasa O, Greensmith L, Malaspina A, Petzold A. A motor neuron strategy to save time and energy in neurodegeneration: adaptive protein stoichiometry. J Neurochem 2019; 146:631-641. [PMID: 29959860 PMCID: PMC6175430 DOI: 10.1111/jnc.14542] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 06/07/2018] [Accepted: 06/21/2018] [Indexed: 01/01/2023]
Abstract
Neurofilament proteins (Nf) are a biomarker of disease progression in amyotrophic lateral sclerosis (ALS). This study investigated whether there are major differences in expression from in vivo measurements of neurofilament isoforms, from the light chain, NfL (68 kDa), compared with larger proteins, the medium chain (NfM, 150 kDa) and the heavy (NfH, 200‐210 kDa) chains in ALS patients and healthy controls. New immunological methods were combined with Nf subunit stoichiometry calculations and Monte Carlo simulations of a coarse‐grained Nf brush model. Based on a physiological Nf subunit stoichiometry of 7 : 3 : 2 (NfL:NfM:NfH), we found an ‘adaptive’ Nf subunit stoichiometry of 24 : 2.4 : 1.6 in ALS. Adaptive Nf stoichiometry preserved NfL gyration radius in the Nf brush model. The energy and time requirements for Nf translation were 56 ± 27k ATP (5.6 h) in control subjects compared to 123 ± 102k (12.3 h) in ALS with ‘adaptive’ (24:2.4:1.6) Nf stoichiometry (not significant) and increased significantly to 355 ± 330k (35.5 h) with ‘luxury’ (7:3:2) Nf subunit stoichiometry (p < 0.0001 for each comparison). Longitudinal disease progression‐related energy consumption was highest with a ‘luxury’ (7:3:2) Nf stoichiometry. Therefore, an energy and time‐saving option for motor neurons is to shift protein expression from larger to smaller (cheaper) subunits, at little or no costs on a protein structural level, to compensate for increased energy demands. ![]()
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Affiliation(s)
- Elisabetta Zucchi
- Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,Center of Genomic and post-Genomic, IRCCS Mondino Foundation, Pavia, Italy
| | - Ching-Hua Lu
- Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,Department of Neurology, China Medical University Hospital, Taichung City, Taiwan
| | - Yunju Cho
- Department of Chemistry, Kwangwoon University, Seoul, Korea
| | - Rakwoo Chang
- Department of Chemistry, Kwangwoon University, Seoul, Korea
| | - Rocco Adiutori
- Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Irene Zubiri
- Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Mauro Ceroni
- Department of Brain and Behavioural Sciences, University of Pavia, Pavia, Italy.,General Neurology Unit, IRCCS Mondino Foundation, Pavia, Italy
| | - Cristina Cereda
- Center of Genomic and post-Genomic, IRCCS Mondino Foundation, Pavia, Italy
| | - Orietta Pansarasa
- Center of Genomic and post-Genomic, IRCCS Mondino Foundation, Pavia, Italy
| | - Linda Greensmith
- Sobell Department of Motor Neuroscience and Movement Disorders, MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, University College London, London, UK
| | - Andrea Malaspina
- Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Axel Petzold
- Department of Neuromuscular Diseases, MRC Centre for Neuromuscular Diseases, Queen Square, London, UK.,The National Hospital for Neurology and Neurosurgery, Queen Square, London, UK.,Moorfields Eye Hospital, London, UK.,Amsterdam UMC, Departments of Neurology and Ophthalmology, De Boelelaan, Amsterdam, NL
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7
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Lancaster E, Li J, Hanania T, Liem R, Scheideler MA, Scherer SS. Myelinated axons fail to develop properly in a genetically authentic mouse model of Charcot-Marie-Tooth disease type 2E. Exp Neurol 2018; 308:13-25. [PMID: 29940160 DOI: 10.1016/j.expneurol.2018.06.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 06/14/2018] [Accepted: 06/19/2018] [Indexed: 11/25/2022]
Abstract
We have analyzed a mouse model of Charcot-Marie-Tooth disease 2E (CMT2E) harboring a heterozygous p.Asn98Ser (p.N98S) Nefl mutation, whose human counterpart results in a severe, early-onset neuropathy. Behavioral, electrophysiological, and pathological analyses were done on separate cohorts of NeflN98S/+ mutant mice and their wild type Nefl+/+ littermates between 8 and 48 weeks of age. The motor performance of NeflN98S/+ mice, as evidenced by altered balance and gait measures, was impaired at every age examined (from 6 to 25 weeks of age). At all times examined, myelinated axons were smaller and contained markedly fewer neurofilaments in NeflN98S/+ mice, in all examined aspects of the PNS, from the nerve roots to the distal ends of the sciatic and caudal nerves. Similarly, the myelinated axons in the various tracts of the spinal cord and in the optic nerves were smaller and contained fewer neurofilaments in mutant mice. The myelinated axons in both the PNS and the CNS of mutant mice had relatively thicker myelin sheaths. The amplitude and the nerve conduction velocity of the caudal nerves were reduced in proportion with the diminished sizes of myelinated axons. Conspicuous aggregations of neurofilaments were only seen in primary sensory and motor neurons, and were largely confined to the cell bodies and proximal axons. There was evidence of axonal degeneration and regeneration of myelinated axons, mostly in distal nerves. In summary, the p.N98S mutation causes a profound reduction of neurofilaments in the myelinated axons of the PNS and CNS, resulting in substantially reduced axonal diameters, particularly of large myelinated axons, and distal axon loss in the PNS.
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Affiliation(s)
- Eunjoo Lancaster
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - Jian Li
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - Taleen Hanania
- Psychogenics Inc 215 College Road Paramus, NJ 07652, United States
| | - Ronald Liem
- Department of Pathology, Columbia University College of Physicians & Surgeons, New York, NY 10032, United States
| | | | - Steven S Scherer
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
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8
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Mancuso R, Navarro X. Sigma-1 Receptor in Motoneuron Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 964:235-254. [PMID: 28315275 DOI: 10.1007/978-3-319-50174-1_16] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Amyotrophic Lateral Sclerosis (ALS ) is a neurodegenerative disease affecting spinal cord and brain motoneurons , leading to paralysis and early death. Multiple etiopathogenic mechanisms appear to contribute in the development of ALS , including glutamate excitotoxicity, oxidative stress , protein misfolding, mitochondrial defects, impaired axonal transport, inflammation and glial cell alterations. The Sigma-1 receptor is highly expressed in motoneurons of the spinal cord, particularly enriched in the endoplasmic reticulum (ER) at postsynaptic cisternae of cholinergic C-terminals. Several evidences point to participation of Sigma-1R alterations in motoneuron degeneration. Thus, mutations of the transmembrane domain of the Sigma-1R have been described in familial ALS cases. Interestingly, Sigma-1R KO mice display muscle weakness and motoneuron loss. On the other hand, Sigma-1R agonists promote neuroprotection and neurite elongation through activation of protein kinase C on motoneurons in vitro and in vivo after ventral root avulsion. Remarkably, treatment of SOD1 mice, the most usual animal model of ALS , with Sigma-1R agonists resulted in significantly enhanced motoneuron function and preservation, and increased animal survival. Sigma-1R activation also reduced microglial reactivity and increased the glial expression of neurotrophic factors. Two main interconnected mechanisms seem to underlie the effects of Sigma-1R manipulation on motoneurons: modulation of neuronal excitability and regulation of calcium homeostasis. In addition, Sigma-1R also contributes to regulating protein degradation, and reducing oxidative stress. Therefore, the multi-functional nature of the Sigma-1R represents an attractive target for treating aspects of ALS and other motoneuron diseases .
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Affiliation(s)
- Renzo Mancuso
- Center for Biological Sciences, University of Southampton, Southampton General Hospital, SO16 6YD, Southampton, UK
| | - Xavier Navarro
- Institute of Neurosciences and Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain.
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9
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Positron emission tomography in amyotrophic lateral sclerosis: Towards targeting of molecular pathological hallmarks. Eur J Nucl Med Mol Imaging 2016; 44:533-547. [DOI: 10.1007/s00259-016-3587-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Accepted: 11/23/2016] [Indexed: 12/18/2022]
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10
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A Stochastic Multiscale Model That Explains the Segregation of Axonal Microtubules and Neurofilaments in Neurological Diseases. PLoS Comput Biol 2015; 11:e1004406. [PMID: 26285012 PMCID: PMC4540448 DOI: 10.1371/journal.pcbi.1004406] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 06/17/2015] [Indexed: 11/19/2022] Open
Abstract
The organization of the axonal cytoskeleton is a key determinant of the normal function of an axon, which is a long thin projection of a neuron. Under normal conditions two axonal cytoskeletal polymers, microtubules and neurofilaments, align longitudinally in axons and are interspersed in axonal cross-sections. However, in many neurotoxic and neurodegenerative disorders, microtubules and neurofilaments segregate apart from each other, with microtubules and membranous organelles clustered centrally and neurofilaments displaced to the periphery. This striking segregation precedes the abnormal and excessive neurofilament accumulation in these diseases, which in turn leads to focal axonal swellings. While neurofilament accumulation suggests an impairment of neurofilament transport along axons, the underlying mechanism of their segregation from microtubules remains poorly understood for over 30 years. To address this question, we developed a stochastic multiscale model for the cross-sectional distribution of microtubules and neurofilaments in axons. The model describes microtubules, neurofilaments and organelles as interacting particles in a 2D cross-section, and is built upon molecular processes that occur on a time scale of seconds or shorter. It incorporates the longitudinal transport of neurofilaments and organelles through this domain by allowing stochastic arrival and departure of these cargoes, and integrates the dynamic interactions of these cargoes with microtubules mediated by molecular motors. Simulations of the model demonstrate that organelles can pull nearby microtubules together, and in the absence of neurofilament transport, this mechanism gradually segregates microtubules from neurofilaments on a time scale of hours, similar to that observed in toxic neuropathies. This suggests that the microtubule-neurofilament segregation can be a consequence of the selective impairment of neurofilament transport. The model generates the experimentally testable prediction that the rate and extent of segregation will be dependent on the sizes of the moving organelles as well as the density of their traffic. The shape and function of axons is dependent on a dynamic system of microscopic intracellular protein polymers (microtubules, neurofilaments and microfilaments) that comprise the axonal cytoskeleton. Neurofilaments are cargoes of intracellular transport that move along microtubule tracks, and they accumulate abnormally in axons in many neurotoxic and neurodegenerative disorders. Intriguingly, it has been reported that neurofilaments and microtubules, which are normally interspersed in axonal cross-sections, often segregate apart from each other in these disorders, which is something that is never observed in healthy axons. Here we describe a stochastic multiscale computational model that explains the mechanism of this striking segregation and offers insights into the mechanism of neurofilament accumulation in disease.
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Mancuso R, Navarro X. Amyotrophic lateral sclerosis: Current perspectives from basic research to the clinic. Prog Neurobiol 2015; 133:1-26. [PMID: 26253783 DOI: 10.1016/j.pneurobio.2015.07.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 07/30/2015] [Accepted: 07/31/2015] [Indexed: 02/07/2023]
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive degeneration of upper and lower motoneurons, leading to muscle weakness and paralysis, and finally death. Considerable recent advances have been made in basic research and preclinical therapeutic attempts using experimental models, leading to increasing clinical and translational research in the context of this disease. In this review we aim to summarize the most relevant findings from a variety of aspects about ALS, including evaluation methods, animal models, pathophysiology, and clinical findings, with particular emphasis in understanding the role of every contributing mechanism to the disease for elucidating the causes underlying degeneration of motoneurons and the development of new therapeutic strategies.
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Affiliation(s)
- Renzo Mancuso
- Institute of Neurosciences and Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain
| | - Xavier Navarro
- Institute of Neurosciences and Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain.
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Häggmark A, Mikus M, Mohsenchian A, Hong MG, Forsström B, Gajewska B, Barańczyk-Kuźma A, Uhlén M, Schwenk JM, Kuźma-Kozakiewicz M, Nilsson P. Plasma profiling reveals three proteins associated to amyotrophic lateral sclerosis. Ann Clin Transl Neurol 2014; 1:544-53. [PMID: 25356426 PMCID: PMC4184557 DOI: 10.1002/acn3.83] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 06/12/2014] [Accepted: 06/12/2014] [Indexed: 01/13/2023] Open
Abstract
Objective Amyotrophic lateral sclerosis (ALS) is the most common adult motor neuron disease leading to muscular paralysis and death within 3–5 years from onset. Currently, there are no reliable and sensitive markers able to substantially shorten the diagnosis delay. The objective of the study was to analyze a large number of proteins in plasma from patients with various clinical phenotypes of ALS in search for novel proteins or protein profiles that could serve as potential indicators of disease. Methods Affinity proteomics in the form of antibody suspension bead arrays were applied to profile plasma samples from 367 ALS patients and 101 controls. The plasma protein content was directly labeled and protein profiles obtained using 352 antibodies from the Human Protein Atlas targeting 278 proteins. A focused bead array was then built to further profile eight selected protein targets in all available samples. Results Disease-associated significant differences were observed and replicated for profiles from antibodies targeting the proteins: neurofilament medium polypeptide (NEFM), solute carrier family 25 (SLC25A20), and regulator of G-protein signaling 18 (RGS18). Interpretation Upon further validation in several independent cohorts with inclusion of a broad range of other neurological disorders as controls, the alterations of these three protein profiles in plasma could potentially provide new molecular markers of disease that contribute to the quest of understanding ALS pathology.
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Affiliation(s)
- Anna Häggmark
- SciLifeLab, School of Biotechnology, KTH-Royal Institute of Technology Stockholm, Sweden
| | - Maria Mikus
- SciLifeLab, School of Biotechnology, KTH-Royal Institute of Technology Stockholm, Sweden
| | - Atefeh Mohsenchian
- SciLifeLab, School of Biotechnology, KTH-Royal Institute of Technology Stockholm, Sweden
| | - Mun-Gwan Hong
- SciLifeLab, School of Biotechnology, KTH-Royal Institute of Technology Stockholm, Sweden
| | - Björn Forsström
- SciLifeLab, School of Biotechnology, KTH-Royal Institute of Technology Stockholm, Sweden
| | - Beata Gajewska
- Department of Biochemistry, Medical University of Warsaw Warsaw, Poland ; Neurodegenerative Diseases Research Group, Medical University of Warsaw Warsaw, Poland
| | - Anna Barańczyk-Kuźma
- Department of Biochemistry, Medical University of Warsaw Warsaw, Poland ; Neurodegenerative Diseases Research Group, Medical University of Warsaw Warsaw, Poland
| | - Mathias Uhlén
- SciLifeLab, School of Biotechnology, KTH-Royal Institute of Technology Stockholm, Sweden
| | - Jochen M Schwenk
- SciLifeLab, School of Biotechnology, KTH-Royal Institute of Technology Stockholm, Sweden
| | - Magdalena Kuźma-Kozakiewicz
- Neurodegenerative Diseases Research Group, Medical University of Warsaw Warsaw, Poland ; Department of Neurology, Medical University of Warsaw Warsaw, Poland
| | - Peter Nilsson
- SciLifeLab, School of Biotechnology, KTH-Royal Institute of Technology Stockholm, Sweden
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Mòdol L, Mancuso R, Alé A, Francos-Quijorna I, Navarro X. Differential effects on KCC2 expression and spasticity of ALS and traumatic injuries to motoneurons. Front Cell Neurosci 2014; 8:7. [PMID: 24478630 PMCID: PMC3900854 DOI: 10.3389/fncel.2014.00007] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 01/06/2014] [Indexed: 12/11/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease manifested by progressive muscle atrophy and paralysis due to the loss of upper and lower motoneurons (MN). Spasticity appears in ALS patients leading to further disabling consequences. Loss of the inhibitory tone induced by downregulation of the potassium chloride cotransporter 2 (KCC2) in MN has been proposed to importantly contribute to the spastic behavior after spinal cord injury (SCI). The aim of the present study was to test whether the alterations in the expression of KCC2 are linked to the appearance of spasticity in the SODG93A ALS murine model. We compared SODG93A mice to wild type mice subjected to SCI to mimic the spinal MN disconnection from motor descending pathways, and to sciatic nerve lesion to mimic the loss of MN connectivity to muscle. Electrophysiological results show that loss of motor function is observed at presymptomatic stage (8 weeks) in SODG93A mice but hyperreflexia and spasticity do not appear until a late stage (16 weeks). However, KCC2 was not downregulated despite MN suffered disconnection both from muscles and upper MNs. Further experiments revealed decreased gephyrin expression, as a general marker of inhibitory systems, accompanied by a reduction in the number of Renshaw interneurons. Moreover, 5-HT fibers were increased in the ventral horn of the lumbar spinal cord at late stage of disease progression in SOD1G93A mice. Taken together, the present results indicate that spasticity appears late in the ALS model, and may be mediated by a decrease in inhibitory interneurons and an increase of 5-HT transmission, while the absence of down-regulation of KCC2 could rather indicate an inability of MNs to respond to insults.
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Affiliation(s)
- Laura Mòdol
- Department of Cell Biology, Physiology, and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Institute of Neurosciences, Universitat Autònoma de Barcelona Bellaterra, Spain
| | - Renzo Mancuso
- Department of Cell Biology, Physiology, and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Institute of Neurosciences, Universitat Autònoma de Barcelona Bellaterra, Spain
| | - Albert Alé
- Department of Cell Biology, Physiology, and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Institute of Neurosciences, Universitat Autònoma de Barcelona Bellaterra, Spain
| | - Isaac Francos-Quijorna
- Department of Cell Biology, Physiology, and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Institute of Neurosciences, Universitat Autònoma de Barcelona Bellaterra, Spain
| | - Xavier Navarro
- Department of Cell Biology, Physiology, and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Institute of Neurosciences, Universitat Autònoma de Barcelona Bellaterra, Spain
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14
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Regional alterations in cortical thickness and white matter integrity in amyotrophic lateral sclerosis. J Neurol 2014; 261:412-21. [PMID: 24452838 DOI: 10.1007/s00415-013-7215-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 12/09/2013] [Accepted: 12/10/2013] [Indexed: 12/11/2022]
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15
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Holmgren A, Bouhy D, De Winter V, Asselbergh B, Timmermans JP, Irobi J, Timmerman V. Charcot-Marie-Tooth causing HSPB1 mutations increase Cdk5-mediated phosphorylation of neurofilaments. Acta Neuropathol 2013; 126:93-108. [PMID: 23728742 PMCID: PMC3963106 DOI: 10.1007/s00401-013-1133-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 05/03/2013] [Accepted: 05/21/2013] [Indexed: 01/21/2023]
Abstract
Mutations in the small heat shock protein HSPB1 (HSP27) are a cause of axonal Charcot-Marie-Tooth neuropathy (CMT2F) and distal hereditary motor neuropathy. To better understand the effect of mutations in HSPB1 on the neuronal cytoskeleton, we stably transduced neuronal cells with wild-type and mutant HSPB1 and investigated axonal transport of neurofilaments (NFs). We observed that mutant HSPB1 affected the binding of NFs to the anterograde motor protein kinesin, reducing anterograde transport of NFs. These deficits were associated with an increased phosphorylation of NFs and cyclin-dependent kinase Cdk5. As Cdk5 mediates NF phosphorylation, inhibition of Cdk5/p35 restored NF phosphorylation level, as well as NF binding to kinesin in mutant HSPB1 neuronal cells. Altogether, we demonstrate that HSPB1 mutations induce hyperphosphorylation of NFs through Cdk5 and reduce anterograde transport of NFs.
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Affiliation(s)
- Anne Holmgren
- Department of Molecular Genetics, VIB and University of Antwerp, 2610 Antwerpen, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, 2610 Antwerpen, Belgium
| | - Delphine Bouhy
- Department of Molecular Genetics, VIB and University of Antwerp, 2610 Antwerpen, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, 2610 Antwerpen, Belgium
| | - Vicky De Winter
- Department of Molecular Genetics, VIB and University of Antwerp, 2610 Antwerpen, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, 2610 Antwerpen, Belgium
| | - Bob Asselbergh
- Department of Molecular Genetics, VIB and University of Antwerp, 2610 Antwerpen, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, 2610 Antwerpen, Belgium
| | - Jean-Pierre Timmermans
- Laboratory of Cell Biology and Histology, Department of Veterinary Sciences, University of Antwerp, 2020 Antwerpen, Belgium
| | - Joy Irobi
- Department of Molecular Genetics, VIB and University of Antwerp, 2610 Antwerpen, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, 2610 Antwerpen, Belgium
| | - Vincent Timmerman
- Department of Molecular Genetics, VIB and University of Antwerp, 2610 Antwerpen, Belgium
- Laboratory of Neurogenetics, Institute Born-Bunge, 2610 Antwerpen, Belgium
- Peripheral Neuropathy Group, VIB Department of Molecular Genetics, University of Antwerp, Universiteitsplein 1, 2610 Antwerpen, Belgium
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16
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Lee J, Kim S, Chang R, Jayanthi L, Gebremichael Y. Effects of molecular model, ionic strength, divalent ions, and hydrophobic interaction on human neurofilament conformation. J Chem Phys 2013; 138:015103. [DOI: 10.1063/1.4773297] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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17
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Redler RL, Dokholyan NV. The complex molecular biology of amyotrophic lateral sclerosis (ALS). PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 107:215-62. [PMID: 22482452 DOI: 10.1016/b978-0-12-385883-2.00002-3] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disorder that causes selective death of motor neurons followed by paralysis and death. A subset of ALS cases is caused by mutations in the gene for Cu, Zn superoxide dismutase (SOD1), which impart a toxic gain of function to this antioxidant enzyme. This neurotoxic property is widely believed to stem from an increased propensity to misfold and aggregate caused by decreased stability of the native homodimer or a tendency to lose stabilizing posttranslational modifications. Study of the molecular mechanisms of SOD1-related ALS has revealed a complex array of interconnected pathological processes, including glutamate excitotoxicity, dysregulation of neurotrophic factors and axon guidance proteins, axonal transport defects, mitochondrial dysfunction, deficient protein quality control, and aberrant RNA processing. Many of these pathologies are directly exacerbated by misfolded and aggregated SOD1 and/or cytosolic calcium overload, suggesting the primacy of these events in disease etiology and their potential as targets for therapeutic intervention.
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Affiliation(s)
- Rachel L Redler
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA
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18
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Ling KKY, Gibbs RM, Feng Z, Ko CP. Severe neuromuscular denervation of clinically relevant muscles in a mouse model of spinal muscular atrophy. Hum Mol Genet 2011; 21:185-95. [PMID: 21968514 DOI: 10.1093/hmg/ddr453] [Citation(s) in RCA: 151] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Spinal muscular atrophy (SMA), a motoneuron disease caused by a deficiency of the survival of motor neuron (SMN) protein, is characterized by motoneuron loss and muscle weakness. It remains unclear whether widespread loss of neuromuscular junctions (NMJs) is involved in SMA pathogenesis. We undertook a systematic examination of NMJ innervation patterns in >20 muscles in the SMNΔ7 SMA mouse model. We found that severe denervation (<50% fully innervated endplates) occurs selectively in many vulnerable axial muscles and several appendicular muscles at the disease end stage. Since these vulnerable muscles were located throughout the body and were comprised of varying muscle fiber types, it is unlikely that muscle location or fiber type determines susceptibility to denervation. Furthermore, we found a similar extent of neurofilament accumulation at NMJs in both vulnerable and resistant muscles before the onset of denervation, suggesting that neurofilament accumulation does not predict subsequent NMJ denervation. Since vulnerable muscles were initially innervated, but later denervated, loss of innervation in SMA may be attributed to defects in synapse maintenance. Finally, we found that denervation was amendable by trichostatin A (TSA) treatment, which increased innervation in clinically relevant muscles in TSA-treated SMNΔ7 mice. Our findings suggest that neuromuscular denervation in vulnerable muscles is a widespread pathology in SMA, and can serve as a preparation for elucidating the biological basis of synapse loss, and for evaluating therapeutic efficacy.
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Affiliation(s)
- Karen K Y Ling
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
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19
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Riboldi G, Nizzardo M, Simone C, Falcone M, Bresolin N, Comi GP, Corti S. ALS genetic modifiers that increase survival of SOD1 mice and are suitable for therapeutic development. Prog Neurobiol 2011; 95:133-48. [PMID: 21816207 DOI: 10.1016/j.pneurobio.2011.07.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Accepted: 07/19/2011] [Indexed: 12/11/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a frequently fatal motor neuron disease without any cure. To find molecular therapeutic targets, several studies crossed transgenic ALS murine models with animals transgenic for some ALS target genes. We aimed to revise the new discoveries and new works in this field. We selected the 10 most promising genes, according to their capability when down-regulated or up-regulated in ALS animal models, for increasing life span and mitigating disease progression: XBP-1, NogoA and NogoB, dynein, heavy and medium neurofilament, NOX1 and NOX2, MLC-mIGF-1, NSE-VEGF, and MMP-9. Interestingly, some crucial modifier genes have been described as being involved in common pathways, the most significant of which are inflammation and cytoskeletal activities. The endoplasmic reticulum also seems to play an important role in ALS pathogenesis, as it is involved in different selected gene pathways. In addition, these genes have evident links to each other, introducing the hypothesis of a single unknown, common pathway involving all of these identified genes and others to be discovered.
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Affiliation(s)
- Giulietta Riboldi
- Department of Neurological Sciences, Dino Ferrari Centre, University of Milan, IRCCS Fondazione Ca' Granda-Ospedale Maggiore Policlinico, Milan, Italy
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20
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Balaratnasingam C, Morgan WH, Bass L, Kang M, Cringle SJ, Yu DY. Axotomy-induced cytoskeleton changes in unmyelinated mammalian central nervous system axons. Neuroscience 2011; 177:269-82. [PMID: 21215300 DOI: 10.1016/j.neuroscience.2010.12.053] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Revised: 12/21/2010] [Accepted: 12/27/2010] [Indexed: 10/18/2022]
Abstract
Oligodendrocyte-derived myelin retards the ability of CNS axons to regenerate following transection. The intrinsic response of CNS axons to an axotomy insult may be vastly different in the absence of myelin. However, the paucity of adequate experimental models has limited detailed investigation of cellular behaviour following axon transection in an unmyelinated CNS environment. In this study we perform laser-induced axotomy of the porcine retinal ganglion cell axon, a physiologically unmyelinated, mature CNS axon that is structurally similar to humans to infer knowledge about axonal behaviour in the absence of myelin. Axotomy-induced changes to the neuronal cytoskeleton and supporting astrocytes during the early stages after transection are delineated by examining the sequence of neurofilament subunit, microtubule (TUB), microtubule associated protein (MAP), glial fibrillary acidic protein (GFAP) and terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling (TUNEL) modification. Axonal transection induced an increase in the expression of neurofilament light at regions within, and immediately adjacent to, sites of axotomy. Other neurofilament subunits were not altered at sites of transection. Unlike myelinated axons where an increase in GFAP staining within hypertrophic glial scars have been shown to inhibit axonal repair we demonstrate a decrease in GFAP staining within regions of increased or preserved neurofilament expression. The behaviour of TUB and MAP proteins following transection of unmyelinated CNS axons are similar to what has previously been described in myelinated CNS axons. This study provides fundamental insights into astrocyte and axonal behaviour acutely after axotomy and demonstrates a series of degenerative events in unmyelinated CNS axons, which in comparison to prior reports are different to myelinated CNS axons. The findings of this report have relevance to understanding pathogenic mechanisms underlying neuro-degeneration in the CNS.
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Affiliation(s)
- C Balaratnasingam
- Centre for Ophthalmology and Visual Science, The University of Western Australia, 2 Verdun Street, Nedlands, Perth, Australia
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21
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Liu YL, Guo YS, Xu L, Wu SY, Wu DX, Yang C, Li CY. Ultrastructural evidence of neurofilament involvement in immune-mediated motor neuron injury. Neurol Res 2008; 30:990-4. [PMID: 18662498 DOI: 10.1179/016164108x323780] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive neurological disorder. A pathologic hallmark of ALS is accumulation of neurofilaments in proximal axons of affected motor neurones. As the neurofilaments involved in immune-mediated spinal cord ventral horn motor neuron degeneration and loss, we developed immune-mediated motor neuron injury animal model by inoculating Lewis rats with swine spinal cord homogenate and investigated the ultrastructural features of neurofilament accumulation using transmission electron microscopy. Our results showed that there was aberrant accumulation of neurofilaments in perikarya and processes of remaining motor neurons in recipient animals, which is similar to those observed in ALS patients. These findings suggest that immune-mediated motor neuron injury may share a common pathogenesis with ALS.
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Affiliation(s)
- Ya-Ling Liu
- Department of Neurology, Second Hospital of Hebei Medical University, 215 He-Ping West Road, Shijiazhuang, China
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22
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Jaitovich A, Mehta S, Na N, Ciechanover A, Goldman RD, Ridge KM. Ubiquitin-proteasome-mediated degradation of keratin intermediate filaments in mechanically stimulated A549 cells. J Biol Chem 2008; 283:25348-25355. [PMID: 18617517 DOI: 10.1074/jbc.m801635200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We previously reported that shear stress induces phosphorylation and disassembly of keratin intermediate filaments (IFs). Shear stress also induces a time- and strain-dependent degradation of keratin IFs, and the current study examines the mechanisms involved in degradation of keratin proteins in human A549 cells exposed to 0-24 h of shear stress (7.5-30 dynes/cm(2)). Ubiquitin was found to be covalently associated with keratin proteins immunoprecipitated from shear-stressed cells, and pretreatment with the proteasomal inhibitor MG132 prevented the degradation of the keratin IF network. Importantly, phosphorylation of K8 Ser-73 is required for the shear stress-mediated ubiquitination, disassembly, and degradation of the keratin IF network. Immunofluorescence microscopy revealed that shear stress caused the thin array of keratin fibrils observed in control cells to be reorganized into a perinuclear aggregate, known as an aggresome, and that ubiquitin was also associated with this structure. Finally, the E2 enzymes, UbcH5b, -c, and Ubc3, but not E2-25K are required for the shear stress-mediated ubiquitin-proteasomal degradation of keratin proteins. These data suggest that shear stress promotes the disassembly and degradation of the keratin IF network via phosphorylation and the ubiquitin-proteasome pathway.
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Affiliation(s)
- Ariel Jaitovich
- Division of Pulmonary and Critical Care Medicine, Illinois 60611
| | - Semil Mehta
- Division of Pulmonary and Critical Care Medicine, Illinois 60611
| | - Ni Na
- Division of Pulmonary and Critical Care Medicine, Illinois 60611
| | - Aaron Ciechanover
- The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | - Robert D Goldman
- Division of Pulmonary and Critical Care Medicine, Illinois 60611; Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
| | - Karen M Ridge
- Division of Pulmonary and Critical Care Medicine, Illinois 60611; Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611.
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Hayashi S, Yamazaki T, Okamoto K. Nonapoptotic cell death caused by the inhibition of RNA polymerase disrupts organelle distribution. J Neurol Sci 2007; 256:10-20. [PMID: 17360003 DOI: 10.1016/j.jns.2007.01.077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Revised: 01/18/2007] [Accepted: 01/23/2007] [Indexed: 11/20/2022]
Abstract
It is controversial whether the mode of cell death induced by CAG repeat diseases is apoptotic. One technical problem that affects this issue is that the very methods used for DNA injection may induce artificial apoptosis. A recent study demonstrated that the functions of RNA polymerase II are disrupted in spinocerebellar ataxia type 1 (SCA 1) pathology, one of the CAG repeat diseases, and that alpha-amanitin can inhibit the activity of RNA polymerase. To examine the cell death mechanisms involved in CAG repeat diseases, we treated cultured rat neurons with alpha-amanitin to avoid the artifacts caused by DNA transfection. Mature and immature rat neurons were treated with alpha-amanitin for 4-6 days and the effects of the treatment on the elongation of neurites, the distribution or morphology of organelles, and the nature of cell death were assessed by immunocytochemistry and quantitative analysis. Neurons exhibited a disruption of neurite elongation and eventually died by day 15 of the treatment. However, apoptosis was not detected. When the neurons survived well, but showed altered neurites, Golgi complexes and lysosomes exhibited changes in their normal intracellular distribution or morphology, but the endoplasmic reticulum and mitochondria did not. The distribution of phosphorylated Trk receptors was also disrupted in the neurites of treated neurons. The signal intensity of the dynein intermediate chain was markedly decreased in the treated neurons. Thus, organelle transport systems, particularly a minus-end-directed microtubule-dependent pathway, would be disrupted by the inhibition of RNA polymerase, and this change is likely to be an early event involved in SCA 1 pathology.
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Affiliation(s)
- Shintaro Hayashi
- Department of Neurology, Gunma University, Graduate School of Medicine, 3-39-15 Showa-Machi, Maebashi, Gunma, Japan
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Petzold A. Neurofilament phosphoforms: surrogate markers for axonal injury, degeneration and loss. J Neurol Sci 2005; 233:183-98. [PMID: 15896809 DOI: 10.1016/j.jns.2005.03.015] [Citation(s) in RCA: 484] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This review on the role of neurofilaments as surrogate markers for axonal degeneration in neurological diseases provides a brief background to protein synthesis, assembly, function and degeneration. Methodological techniques for quantification are described and a protein nomenclature is proposed. The relevance for recognising anti-neurofilament autoantibodies is noted. Pathological implications are discussed in view of immunocytochemical, cell-culture and genetic findings. With reference to the present symposium on multiple sclerosis, the current literature on body fluid levels of neurofilaments in demyelinating disease is summarised.
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Affiliation(s)
- Axel Petzold
- Department of Neuroimmunology, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
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Lüdemann N, Clement A, Hans VH, Leschik J, Behl C, Brandt R. O-glycosylation of the tail domain of neurofilament protein M in human neurons and in spinal cord tissue of a rat model of amyotrophic lateral sclerosis (ALS). J Biol Chem 2005; 280:31648-58. [PMID: 16006557 DOI: 10.1074/jbc.m504395200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian neurofilaments (NFs) are modified by post-translational modifications that are thought to regulate NF assembly and organization. Whereas phosphorylation has been intensely studied, the role of another common modification, the attachment of O-linked N-acetylglucosamine (GlcNAc) to individual serine and threonine residues, is hardly understood. We generated a novel monoclonal antibody that specifically recognizes an O-glycosylated epitope in the tail domain of NF-M and allows determination of the glycosylation state at this residue. The antibody displays strong species preference for human NF-M, shows some reactivity with rat but not with mouse or bovine NF-M. By immunohistochemistry and Western blot analysis of biopsy-derived human temporal lobe tissue we show that immunoreactivity is highly enriched in axons parallel to hyperphosphorylated NFs. Treatment of cultured neurons with the GlcNAcase inhibitor PUGNAc causes a 40% increase in immunoreactivity within 1 h, which is completely reversible and parallels the total increase in cellular O-GlcNAc modification. Treatment with the mitogen-activated protein kinase kinase inhibitor PD-98059 leads to a similar increase in immunoreactivity. In spinal cord tissue of a transgenic rat model for amyotrophic lateral sclerosis, immunoreactivity is strongly decreased compared with wild-type animals while phosphorylation is increased. The data suggest that hyperphosphorylation and tail domain O-glycosylation of NFs are synchronously regulated in axons of human neurons in situ and that O-glycosylation of NF-M is highly dynamic and closely interweaved with phosphorylation cascades and may have a pathophysiological role.
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Affiliation(s)
- Nina Lüdemann
- Department of Neurobiology, University of Osnabrück, Barbarastrasse 11, D-49076 Osnabrück
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26
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Brandt R, Hundelt M, Shahani N. Tau alteration and neuronal degeneration in tauopathies: mechanisms and models. Biochim Biophys Acta Mol Basis Dis 2005; 1739:331-54. [PMID: 15615650 DOI: 10.1016/j.bbadis.2004.06.018] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Accepted: 06/15/2004] [Indexed: 12/19/2022]
Abstract
Tau becomes characteristically altered both functionally and structurally in several neurodegenerative diseases now collectively called tauopathies. Although increasing evidence supports that alterations of tau may directly cause neuronal degeneration and cell death, the mechanisms, which render tau to become a toxic agent are still unclear. In addition, it is obscure, whether neurodegeneration in tauopathies occurs via a common mechanism or specific differences exist. The aim of this review is to provide an overview about the different experimental models that currently exist, how they are used to determine the role of tau during degeneration and what has been learnt from them concerning the mechanistic role of tau in the disease process. The review begins with a discussion about similarities and differences in tau alteration in paradigmatic tauopathies such as frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) and Alzheimer's disease (AD). The second part concentrates on major experimental models that have been used to address the mechanistic role of tau during degeneration. This will include a discussion of cell-free assays, culture models using cell lines or dissociated neurons, and animal models. How these models aid to understand (i) alterations in the function of tau as a microtubule-associated protein (MAP), (ii) direct cytotoxicity of altered tau protein, and (iii) the potential role of tau aggregation in neurodegenerative processes will be the central theme of this part. The review ends with concluding remarks about a general mechanistic model of the role of tau alteration and neuronal degeneration in tauopathies and future perspectives.
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Affiliation(s)
- Roland Brandt
- Department of Neurobiology, University of Osnabrück, Barbarastrasse 11, D-49076 Osnabrück, Germany.
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Zatloukal K, Stumptner C, Fuchsbichler A, Fickert P, Lackner C, Trauner M, Denk H. The keratin cytoskeleton in liver diseases. J Pathol 2004; 204:367-76. [PMID: 15495250 DOI: 10.1002/path.1649] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The keratin intermediate filament (IF) cytoskeleton of hepatocytes has continuously gained medical relevance over the last two decades. Originally it was mainly recognized as a differentiation marker for diagnostic purposes in pathology. However, keratin IFs were soon identified as major cellular structures to be affected in a variety of chronic liver diseases, such as alcoholic and non-alcoholic steatohepatitis (ASH, NASH), copper toxicosis, and cholestasis. Based on observations in keratin gene knock-out mice, the insight into the functional role of keratins was extended from a mere structural role providing mechanical stability to hepatocytes, to an additional role as target and modulator of toxic stress and apoptosis. The functional relevance of keratins in human diseases has recently been underlined by the identification of mutations in keratin genes in patients with liver cirrhosis.
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Affiliation(s)
- Kurt Zatloukal
- Institute of Pathology, Medical University of Graz, A-8036 Graz, Austria.
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Lalonde R, Dumont M, Paly E, London J, Strazielle C. Characterization of hemizygous SOD1/wild-type transgenic mice with the SHIRPA primary screen and tests of sensorimotor function and anxiety. Brain Res Bull 2004; 64:251-8. [PMID: 15464862 DOI: 10.1016/j.brainresbull.2004.07.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2003] [Revised: 06/21/2004] [Accepted: 07/21/2004] [Indexed: 10/26/2022]
Abstract
SOD1 is one of several overexpressed genes in Down's syndrome. In order to dissect genetic causes of the syndrome, hemizygous human wild-type SOD1 transgenic mice were compared to FVB/N non-transgenic controls at 3 months of age in the SHIRPA primary screen of neurologic function as well as in tests of motor activity and coordination. The responsiveness of SOD1/wt transgenic mice to visual and somatosensory stimuli was reduced in placing, pinna, corneal, and toe-pinch tests. In addition, SOD1/wt transgenic mice crossed fewer segments on a stationary beam. On the contrary, there was no intergroup difference for motor activity and anxiety in open-field and emergence tests and for latencies before falling on the stationary beam, coat-hanger, and rotorod. These results indicate mild deficits in sensorimotor responsiveness in a mouse model expressing human SOD1 and that the overexpressed gene may be responsible for some Down symptoms.
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Affiliation(s)
- R Lalonde
- Faculté de Médecine et de Pharmacie, Université de Rouen, INSERM U614, Bâtiment de Recherche, 22 bld Gambetta, Salle 1D18, 76183 Rouen, Cedex, France.
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29
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Bruneteau G, Demeret S, Meininger V. Physiopathologie de la Sclérose Latérale Amyotrophique : approches thérapeutiques. Rev Neurol (Paris) 2004; 160:235-41. [PMID: 15034483 DOI: 10.1016/s0035-3787(04)70897-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The finding in 1993 of a mutation of the copper zinc super oxyde dismutase (SOD1) provides a major breakthrough in the understanding of the etiopathogenic mechanism of amyotrophic lateral sclerosis. Various mechanisms are commonly implied in the motor neurons degeneration. Excitotoxicity and calcium metabolism abnormalities are one of the most frequently confirmed hypotheses. It allowed proposing riluzole which remains the only one drug proved to be active in the disease. The role of growth factors remains controversial and all therapeutic trials performed with these molecules remained negative. Oxidative stress abnormalities are demonstrated by number of studies but their direct therapeutic application remains to be demonstrated. Apoptosis and the role of mitochondria has been definitely confirmed and open a new therapeutic avenue for the next few years.
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Affiliation(s)
- G Bruneteau
- Fédération de neurologie Mazarin, Hôpital de la Salpêtrière, Paris
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30
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Zatloukal K, Stumptner C, Fuchsbichler A, Janig E, Denk H. Intermediate Filament Protein Inclusions. Methods Cell Biol 2004; 78:205-28. [PMID: 15646620 DOI: 10.1016/s0091-679x(04)78008-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Kurt Zatloukal
- Institute of Pathology, Medical University of Graz, A-8036 Graz, Austria
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31
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Rhee SD, Kim E, Yoon SK, Yang SD, Okumoto M, Han SS, Song CW. Fine Localization of Nefl and Nef3 and its Exclusion as Candidate Gene for Lens Rupture 2(lr2). Exp Anim 2004; 53:295-301. [PMID: 15297702 DOI: 10.1538/expanim.53.295] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Cataract causing lr2 gene is found in the CXSD mouse, which is a recombinant inbred strain of BALB/c and STS mice. For the process of positional cloning of lr2, several candidate genes were selected in the middle region of chromosome 14, but most of them were excluded by combination of recombination and homozygosity mapping. Components of neurofilament proteins, neurofilament light polypeptide (Nefl) and neurofilament3 medium (Nef3), were linked to D14Mit87 which was not separated from the lr2 locus in the homozygosity mapping. When the expression levels of Nefl and Nef3 in eyes were compared in CXSD and BALB/c mice, there were no differences in expression levels. The cDNA sequences of the two genes from CXSD, BALB/c and STS mice were subsequently compared. Several nucleotide differences in cDNA sequences were detected between the mice strains but the majority of the changes were silent mutations that did not alter the amino acids. The sole amino acid difference, E567K in the glutamate rich region of Nfm, between BALB/c and CXSD was found to be a simple genetic polymorphism because the same substitution existed in STS, a non-cataract mouse strain. Therefore we excluded Nefl and Nef3 from the candidate genes for lr2 based on expression and mutation analyses.
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Affiliation(s)
- Sang Dal Rhee
- Korea Research Institute of Chemical Technology, Yusong-gu, Taejon
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Lalonde R, Eyer J, Wunderle V, Strazielle C. Characterization of NFH-LacZ transgenic mice with the SHIRPA primary screening battery and tests of motor coordination, exploratory activity, and spatial learning. Behav Processes 2003; 63:9-19. [PMID: 12763264 DOI: 10.1016/s0376-6357(03)00013-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
NFH-LacZ transgenic mice express a fusion protein between a truncated form of the endogenous neurofilament of heavy molecular weight and the complete E. coli beta-galactosidase. NFH-LacZ transgenic mice could be distinguished from controls in the SHIRPA neurological battery by the appearance of action tremor and hindlimb clasping and a lower body weight. Despite normal exploratory activity and spatial learning, NFH-LacZ transgenic mice were deficient in stationary beam, coat-hanger, and rotorod tests of motor coordination. These results are concordant with neuropathological findings in spinal motoneurons and the cerebellum and indicate that despite the absence of paralysis, these transgenic mice may serve as an experimental model of the early stage of amyotrophic lateral sclerosis.
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Affiliation(s)
- R Lalonde
- Faculté de Médecine et de Pharmacie, Université de Rouen, INSERM EMI 9906, IFRNP, Bâtiment de Recherche, Cedex 76183, Rouen, France
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Dubois M, Strazielle C, Eyer J, Lalonde R. Sensorimotor functions in transgenic mice expressing the neurofilament/heavy-LacZ fusion protein on two genetic backgrounds. Neuroscience 2002; 112:447-54. [PMID: 12044462 DOI: 10.1016/s0306-4522(02)00076-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
NFH-LacZ transgenic mice are characterized by expression of a non-endogenous fusion protein between a truncated form of mouse NFH (neurofilament of heavy molecular weight) and the complete Escherichia coli beta-galactosidase protein. These transgenic mice were compared to their respective controls on two background strains (C3H and FVB) in several sensorimotor tests. NFH-LacZ mice were deficient in tests requiring balance and equilibrium in a manner generally independent of genetic background. In particular, NFH-LacZ mice fell more quickly than controls from two stationary beams and had fewer rears in an open-field. The transgenic mice were also impaired during the initial trials of sensorimotor learning on the rotorod. We conclude that despite the absence of overt signs of sensorimotor weakness in their home cage, the disruption of the NFH gene, causing neurofilament accumulations in the cell body and diminished axonal calibers of motoneurons, is sufficient to cause motor deficits that resemble the early stages of amyotrophic lateral sclerosis.
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Affiliation(s)
- M Dubois
- Université de Rouen, Faculté des Sciences, UPRES PSY.CO-1780, Laboratoire de Neurobiologie de l'Apprentissage, Mont-Saint-Aignan, France
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LaMonte BH, Wallace KE, Holloway BA, Shelly SS, Ascaño J, Tokito M, Van Winkle T, Howland DS, Holzbaur ELF. Disruption of dynein/dynactin inhibits axonal transport in motor neurons causing late-onset progressive degeneration. Neuron 2002; 34:715-27. [PMID: 12062019 DOI: 10.1016/s0896-6273(02)00696-7] [Citation(s) in RCA: 393] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
To test the hypothesis that inhibition of axonal transport is sufficient to cause motor neuron degeneration such as that observed in amyotrophic lateral sclerosis (ALS), we engineered a targeted disruption of the dynein-dynactin complex in postnatal motor neurons of transgenic mice. Dynamitin overexpression was found to disassemble dynactin, a required activator of cytoplasmic dynein, resulting in an inhibition of retrograde axonal transport. Mice overexpressing dynamitin demonstrate a late-onset progressive motor neuron degenerative disease characterized by decreased strength and endurance, motor neuron degeneration and loss, and denervation of muscle. Previous transgenic mouse models of ALS have shown abnormalities in microtubule-based axonal transport. In this report, we describe a mouse model that confirms the critical role of disrupted axonal transport in the pathogenesis of motor neuron degenerative disease.
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Affiliation(s)
- Bernadette H LaMonte
- Department of Physiology, School of Medicine, University of Pennsylvania, 3700 Hamilton Walk, Philadelphia 19104, USA
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Abstract
Brain tissue has a remarkable ability to accumulate glutamate. This ability is due to glutamate transporter proteins present in the plasma membranes of both glial cells and neurons. The transporter proteins represent the only (significant) mechanism for removal of glutamate from the extracellular fluid and their importance for the long-term maintenance of low and non-toxic concentrations of glutamate is now well documented. In addition to this simple, but essential glutamate removal role, the glutamate transporters appear to have more sophisticated functions in the modulation of neurotransmission. They may modify the time course of synaptic events, the extent and pattern of activation and desensitization of receptors outside the synaptic cleft and at neighboring synapses (intersynaptic cross-talk). Further, the glutamate transporters provide glutamate for synthesis of e.g. GABA, glutathione and protein, and for energy production. They also play roles in peripheral organs and tissues (e.g. bone, heart, intestine, kidneys, pancreas and placenta). Glutamate uptake appears to be modulated on virtually all possible levels, i.e. DNA transcription, mRNA splicing and degradation, protein synthesis and targeting, and actual amino acid transport activity and associated ion channel activities. A variety of soluble compounds (e.g. glutamate, cytokines and growth factors) influence glutamate transporter expression and activities. Neither the normal functioning of glutamatergic synapses nor the pathogenesis of major neurological diseases (e.g. cerebral ischemia, hypoglycemia, amyotrophic lateral sclerosis, Alzheimer's disease, traumatic brain injury, epilepsy and schizophrenia) as well as non-neurological diseases (e.g. osteoporosis) can be properly understood unless more is learned about these transporter proteins. Like glutamate itself, glutamate transporters are somehow involved in almost all aspects of normal and abnormal brain activity.
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Affiliation(s)
- N C Danbolt
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1105, Blindern, N-0317, Oslo, Norway
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Shahani N, Gourie-Devi M, Nalini A, Raju TR. Cyclophosphamide attenuates the degenerative changes induced by CSF from patients with amyotrophic lateral sclerosis in the neonatal rat spinal cord. J Neurol Sci 2001; 185:109-18. [PMID: 11311291 DOI: 10.1016/s0022-510x(01)00479-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Our earlier studies have shown that cerebrospinal fluid (CSF) of patients with amyotrophic lateral sclerosis (ALS), when intrathecally injected into the neonatal rats, produces an aberrant phosphorylation of neurofilaments (NF) in the ventral horn neurons and reactive astrogliosis in the spinal cord. We wanted to investigate the effect of cyclophosphamide in the spinal cords of neonatal rats exposed to ALS-CSF. A single dose (5 microg in 5 microl saline) of cyclophosphamide was injected, 24 h after the administration of CSF samples from ALS and non-ALS neurological patients into the spinal subarachnoid space of 3-day-old rat pups. Rats were sacrificed after a period of 24 h, and stained with antibodies against the phosphorylated NF (SMI-31 antibody) and glial fibrillary acidic protein (GFAP). Cyclophosphamide treatment resulted in a 50% decrease in the number of SMI-31 stained neuronal soma in ventral horns of spinal cords of ALS-CSF exposed rats. This was accompanied by a decrease in the number of GFAP immunoreactive astrocytes. Furthermore, lactate dehydrogenase (LDH) activity was also decreased significantly, following cyclophosphamide treatment. These results suggest that cyclophosphamide could exert a neuroprotective effect against the neurotoxic action of factor(s) present in the ALS-CSF.
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Affiliation(s)
- N Shahani
- Department of Neurology, National Institute of Mental Health and Neuro Sciences (NIMHANS) P.O. Box 2900, Hosur Road, 560 029, Bangalore, India
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Grierson AJ, Johnson GV, Miller CC. Three different human tau isoforms and rat neurofilament light, middle and heavy chain proteins are cellular substrates for transglutaminase. Neurosci Lett 2001; 298:9-12. [PMID: 11154823 DOI: 10.1016/s0304-3940(00)01714-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Abnormal aggregates of tau and neurofilaments are pathologies of Alzheimer's disease. Some of these aggregates are insoluble in chaotropic salts and ionic detergents but the mechanisms that lead to this are not clear. One suggestion is that it is due to crosslinking by tissue transglutaminase. Both tau and neurofilaments can be crosslinked by transglutaminase in vitro and one isoform of tau is now known to be a cellular transglutaminase substrate. However there is no evidence to demonstrate that neurofilaments are cellular substrates for transglutaminase and it is not clear whether other isoforms of tau are equally susceptible to transglutaminase crosslinking. Here, we demonstrate that three different tau isoforms and neurofilament light, middle and heavy chain proteins are all cellular substrates for transglutaminase.
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Affiliation(s)
- A J Grierson
- Department of Neuroscience, The Institute of Psychiatry, De Crespigny Park, Denmark Hill, SE5 8AF, London, UK
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38
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Kriz J, Zhu Q, Julien JP, Padjen AL. Electrophysiological properties of axons in mice lacking neurofilament subunit genes: disparity between conduction velocity and axon diameter in absence of NF-H. Brain Res 2000; 885:32-44. [PMID: 11121527 DOI: 10.1016/s0006-8993(00)02899-7] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Neurofilament proteins (NFs) are made by co-polymerization of three intermediate filament proteins, NF-L, NF-M and NF-H and constitute the most abundant cytoskeletal element in large myelinated axons. NFs have a well-established role as intrinsic determinants of axon caliber with all the functional implications, but the role of each individual NF subunit is much less clear. The aim of our study was to examine functional properties of large myelinated axons with altered morphology from mice bearing a targeted disruption of each NF genes (NF-L -/-, NF-M-/- and NF-H -/- mice). Membrane properties, action potentials and single axon refractory period were measured in isolated sciatic nerves in vitro, using intra-axonal microelectrode recording in conjunction with current-clamp technique. Some results were obtained from whole nerves by sucrose-gap recording. The NF-knockout mice showed several deficits in physiological properties of low-threshold fibers. In keeping with smaller axon diameter, the conduction velocity was significantly decreased in NF-L -/- and NF-M -/- transgenic animals (control, 39.9+/-1.8 m/s, NF-M -/-; 23.5+/-1. 4 m/s, and NF-L-/-; 12.0+/-0.7 m/s, mean+/-S.E.M.; intra-axonal recording; similar ratios obtained by sucrose-gap recording; 22-26 degrees C). However, in spite of their preserved caliber, large myelinated axons in NF-H -/- mice also showed a significant decrease in conduction velocity (22.8+/-1.0 m/s, mean+/-S.E.M.). Although action potential amplitudes, duration and shape did not differ between control axons and transgenic animals, the refractory period was prolonged in NF-H -/- and NF-M -/- animals. Intracellular injections of 200 ms depolarizing and hyperpolarizing currents revealed outward and inward rectification in all animal groups. In comparison to control animals, NF-H -/- mice expressed a significant decrease in outward rectification. Potassium channel blockers (4AP and TEA) and cesium ions were able to block outward and inward rectification in all myelinated axons in qualitatively the same manner. These results suggest that NF-H may have a specific role in modulating ion channel functions in large myelinated fibers.
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Affiliation(s)
- J Kriz
- Department of Pharmacology and Therapeutics, the Montreal General Hospital Research Institute, McGill University, 3655 Sir William Osler Promenade (ex-Drummond Street), QC H3G 1Y6, Montréal, Canada
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Pant HC, Grant P. Regulation of axonal neurofilament phosphorylation. CURRENT TOPICS IN CELLULAR REGULATION 2000; 36:133-50. [PMID: 10842750 DOI: 10.1016/s0070-2137(01)80006-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Affiliation(s)
- H C Pant
- Laboratory of Neurochemistry, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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Formation of intermediate filament protein aggregates with disparate effects in two transgenic mouse models lacking the neurofilament light subunit. J Neurosci 2000. [PMID: 10884316 DOI: 10.1523/jneurosci.20-14-05321.2000] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Protein aggregates containing intermediate filaments (IFs) are a hallmark of degenerating spinal motor neurons in amyotrophic lateral sclerosis (ALS). Recently, we reported that a deficiency in neurofilament light subunit (NF-L), a phenomenon associated with ALS, promoted the formation of IF inclusions with ensuing motor neuron death in transgenic mice overproducing peripherin, a type III IF protein detected in axonal inclusions of ALS patients. To further assess the role of NF-L in the formation of abnormal IF inclusions, we generated transgenic mice overexpressing human neurofilament heavy subunits (hNF-H) in a context of targeted disruption of the NF-L gene (hH;L-/- mice). The hH;L-/- mice exhibited motor dysfunction, and they developed nonfilamentous protein aggregates containing NF-H and peripherin proteins in the perikarya of spinal motor neurons. However, the perikaryal protein aggregates in the hH;L-/- mice did not provoke motor neuron death, unlike toxic IF inclusions induced by peripherin overexpression in NF-L null mice (Per;L-/- mice). Our results indicate that different types of IF protein aggregates with distinct properties may occur in a context of NF-L deficiency and that an axonal localization of such aggregates may be an important factor of toxicity.
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Dupuis L, de Tapia M, René F, Lutz-Bucher B, Gordon JW, Mercken L, Pradier L, Loeffler JP. Differential screening of mutated SOD1 transgenic mice reveals early up-regulation of a fast axonal transport component in spinal cord motor neurons. Neurobiol Dis 2000; 7:274-85. [PMID: 10964600 DOI: 10.1006/nbdi.2000.0292] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present study we analyze the molecular mechanisms underlying motor neuron degeneration in familial amyotrophic lateral sclerosis (FALS). For this, we used a transgenic mouse model expressing the Cu/Zn superoxide dismutase (SOD1) gene with a Gly(86) to Arg (G86R) mutation equivalent to that found in a subset of human FALS. Using an optimized suppression subtractive hybridization method, a cDNA specifically up-regulated during the asymptomatic phase in the lumbar spinal cord of G86R mice was identified by sequence analysis as the KIF3-associated protein (KAP3), a regulator of fast axonal transport. RT-PCR analysis revealed that KAP3 induction was an early event arising long before axonal degeneration. Immunohistochemical studies further revealed that KAP3 protein predominantly accumulates in large motor neurons of the ventral spinal cord. We further demonstrated that KAP3 up-regulation occurs independent of any change in the other components of the kinesin II complex. However, since the ubiquitous KIF1A motor is up-regulated, our results show an early and complex rearrangement of the fast axonal transport machinery in the course of FALS pathology.
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Affiliation(s)
- L Dupuis
- Laboratoire de Neurophysiologie Cellulaire et Intégrée, UMR CNRS 7519, Institut de Physiologie et Chimie Biologique, 21 Rue René Descartes, Strasbourg Cédex, 67084, France
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Yabe JT, Jung C, Chan WK, Shea TB. Phospho-dependent association of neurofilament proteins with kinesin in situ. CELL MOTILITY AND THE CYTOSKELETON 2000; 45:249-62. [PMID: 10744858 DOI: 10.1002/(sici)1097-0169(200004)45:4<249::aid-cm1>3.0.co;2-m] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Recent studies demonstrate co-localization of kinesin with neurofilament (NF) subunits in culture and suggest that kinesin participates in NF subunit distribution. We sought to determine whether kinesin was also associated with NF subunits in situ. Axonal transport of NF subunits in mouse optic nerve was perturbed by the microtubule (MT)-depolymerizing drug vinblastine, indicating that NF transport was dependent upon MT dynamics. Kinesin co-precipitated during immunoprecipitation of NF subunits from optic nerve. The association of NFs and kinesin was regulated by NF phosphorylation, since (1) NF subunits bearing developmentally delayed phospho-epitopes did not co-purify in a microtubule motor preparation from CNS while less phosphorylated forms did; (2) subunits bearing these phospho-epitopes were selectively not co-precipitated with kinesin; and (3) phosphorylation under cell-free conditions diminished the association of NF subunits with kinesin. The nature and extent of this association was further examined by intravitreal injection of (35)S-methionine and monitoring NF subunit transport along optic axons. As previously described by several laboratories, the wave of NF subunits underwent a progressive broadening during continued transport. The front, but not the trail, of this broadening wave of NF subunits was co-precipitated with kinesin, indicating that (1) the fastest-moving NFs were associated with kinesin, and (2) that dissociation from kinesin may foster trailing of NF subunits during continued transport. These data suggest that kinesin participates in NF axonal transport either by directly translocating NFs and/or by linking NFs to transporting MTs. Both Triton-soluble as well as cytoskeleton-associated NF subunits were co-precipitated with kinesin; these data are considered in terms of the form(s) in which NF subunits undergo axonal transport.
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Affiliation(s)
- J T Yabe
- Center for Cellular Neurobiology and Neurodegeneration Research, Department of Biological Sciences, University of Massachusetts-Lowell, Lowell, Massachusetts 01854, USA
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43
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Affiliation(s)
- H Denk
- Department of Pathology, University of Graz School of Medicine, Austria.
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44
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Stumptner C, Omary MB, Fickert P, Denk H, Zatloukal K. Hepatocyte cytokeratins are hyperphosphorylated at multiple sites in human alcoholic hepatitis and in a mallory body mouse model. THE AMERICAN JOURNAL OF PATHOLOGY 2000; 156:77-90. [PMID: 10623656 PMCID: PMC1868635 DOI: 10.1016/s0002-9440(10)64708-6] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Alcoholic hepatitis (AH) is associated with cytokeratin 8 and 18 (CK8/18) accumulation as cytoplasmic inclusion bodies, termed Mallory bodies (MBs). Studies with MB mouse models and cultured hepatocytes suggested that CK8/18 hyperphosphorylation might be involved in MB formation. However, no data exist on phosphorylation of CK8/18 in human AH. In this study, antibodies that selectively recognize phosphorylated epitopes of CK8 or CK18 were used to analyze CK8/18 phosphorylation states in normal human and murine livers, human AH biopsies, and livers of 3,5-diethoxycarbonyl-1, 4-dihydrocollidine (DDC)-intoxicated mice, the last serving as model for MB induction. Hepatocyte cytokeratins become hyperphosphorylated at multiple sites in AH and in DDC-intoxicated mice. Hyperphosphorylation of CK8/18 occurred rapidly, after 1 day of DDC intoxication and preceded architectural changes of the cytoskeleton. In long-term DDC-intoxicated mice as well as in human AH, MBs preferentially contain hyperphosphorylated CK8/18 as compared with the cytoplasmic cytokeratin intermediate filament network suggesting that CK8/18 hyperphosphorylation may play a contributing role in MB pathogenesis. Furthermore, the site-specific phosphorylation of cytokeratin in different stages of MB induction provides indirect evidence for the involvement of a variety of protein kinases known to be activated in stress responses, mitosis, and apoptosis.
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Affiliation(s)
- C Stumptner
- Departments of Pathology and Medicine, University of Graz, Graz, Austria
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Flowers JM, Leigh PN, Davies AM, Ninkina NN, Buchman VL, Vaughan J, Wood NW, Powell JF. Mutations in the gene encoding human persyn are not associated with amyotrophic lateral sclerosis or familial Parkinson's disease. Neurosci Lett 1999; 274:21-4. [PMID: 10530510 DOI: 10.1016/s0304-3940(99)00673-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The synucleins are a family of small proteins expressed in nervous tissue, which have been implicated in neurodegeneration. Using single strand conformation polymorphism analysis we screened for polymorphisms and mutations in the gene encoding human persyn, a recently discovered member of the synuclein family, in controls, patients with sporadic or familial amyotrophic lateral sclerosis (ALS) or familial Parkinson's disease (PD). Six polymorphisms in the genomic sequence of persyn were detected; A590C (5' untranslated region), G1943C (exon 3), G2049A (intron 3), T4502C (intron 3), T4552A (exon 4) and C5019T (3' untranslated region). However no associations with disease state were found in our sample group.
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Affiliation(s)
- J M Flowers
- Clinical Neurosciences, Institute of Psychiatry and Guy's, King's and St. Thomas' School of Medicine, Denmark Hill, London, UK.
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Uchida A, Yorifuji H, Lee VMY, Kishimoto T, Hisanaga SI. Neurofilaments of aged rats: The strengthened interneurofilament interaction and the reduced amount of NF-M. J Neurosci Res 1999. [DOI: 10.1002/(sici)1097-4547(19991015)58:2<337::aid-jnr14>3.0.co;2-j] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
We have investigated the axonal transport of neurofilament protein in cultured neurons by constricting single axons with fine glass fibers. We observed a rapid accumulation of anterogradely and retrogradely transported membranous organelles on both sides of the constrictions and a more gradual accumulation of neurofilament protein proximal to the constrictions. Neurofilament protein accumulation was dependent on the presence of metabolic substrates and was blocked by iodoacetate, which is an inhibitor of glycolysis. These data indicate that neurofilament protein moves anterogradely in these axons by a mechanism that is directly or indirectly dependent on nucleoside triphosphates. The average transport rate was estimated to be at least 130 micrometer/h (3.1 mm/d), and approximately 90% of the accumulated neurofilament protein remained in the axon after detergent extraction, suggesting that it was present in a polymerized form. Electron microscopy demonstrated that there were an abnormally large number of neurofilament polymers proximal to the constrictions. These data suggest that the neurofilament proteins were transported either as assembled polymers or in a nonpolymeric form that assembled locally at the site of accumulation. This study represents the first demonstration of the axonal transport of neurofilament protein in cultured neurons.
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Affiliation(s)
- T J Koehnle
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, Ohio 45701, USA
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Abstract
Significant progress has been made in the identification of genes and chromosomal loci associated with several types of motor neuron disease. Of particular interest is recent work on the pathogenic mechanisms underlying these diseases, especially studies in in vitro model systems and in transgenic and gene-targeted mice.
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Affiliation(s)
- P C Wong
- Department of Pathology, Division of Neuropathology, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, Maryland 21205-2196, USA.
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Julien JP, Couillard-Després S, Meier J. Transgenic mice in the study of ALS: the role of neurofilaments. Brain Pathol 1998; 8:759-69. [PMID: 9804382 PMCID: PMC8098559 DOI: 10.1111/j.1750-3639.1998.tb00199.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is an adult-onset neurological disorder of multiple etiologies that affects primarily motor neurons in the brain and spinal cord. Abnormal accumulations of neurofilaments (NFs) in motor neurons and a down-regulation of mRNA for the NF light subunit (NF-L) are associated with ALS, but it remains unclear to what extent these NF perturbations contribute to human disease. Transgenic mouse studies demonstrated that overexpression of normal and mutant NF proteins can sometimes provoke a motor neuronopathy characterized by the presence of abnormal NF accumulations resembling those found in ALS. Remarkably, the motor neuronopathy in transgenic mice overexpressing human NF heavy (NF-H) subunits was rescued by the co-expression of a human NF-L transgene at levels that restored a correct stoichiometry of NF-L to NF-H subunits. Transgenic approaches have also been used to investigate the role of NFs in disease caused by Cu/Zn superoxide dismutase (SOD1) mutations, which is responsible for approximately 2% cases of ALS. Studies with transgenic mice expressing low levels of a fusion NF-H/lacZ protein, in which NFs are withheld from the axonal compartment, suggested that axonal NFs are not toxic intermediates required for SOD1-mediated disease. On the contrary, overexpression of human NF-H proteins was found to confer an effective protection against mutant SOD1 toxicity in transgenic mice, a phenomenon that may be due to the ability of NF proteins to chelate calcium. In conclusion, transgenic studies showed that disorganized NFs can sometimes have noxious effects resulting in neuronopathy. However, in the context of motor neuron disease caused by mutant SOD1, there is emerging evidence that NF proteins rather play a protective role.
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Affiliation(s)
- J P Julien
- Centre for Research in Neuroscience, McGill University, The Montreal General Hospital Research Institute, Québec, Canada.
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Julien JP, Mushynski WE. Neurofilaments in health and disease. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1998; 61:1-23. [PMID: 9752717 DOI: 10.1016/s0079-6603(08)60823-5] [Citation(s) in RCA: 202] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This article reviews current knowledge of neurofilament structure, phosphorylation, and function and neurofilament involvement in disease. Neurofilaments are obligate heteropolymers requiring the NF-L subunit together with either the NF-M or the NF-H subunit for polymer formation. Neurofilaments are very dynamic structures; they contain phosphorylation sites for a large number of protein kinases, including protein kinase A (PKA), protein kinase C (PKC), cyclin-dependent kinase 5 (Cdk5), extracellular signal regulated kinase (ERK), glycogen synthase kinase-3 (GSK-3), and stress-activated protein kinase gamma (SAPK gamma). Most of the neurofilament phosphorylation sites, located in tail regions of NF-M and NF-H, consist of the repeat sequence motif, Lys-Ser-Pro (KSP). In addition to the well-established role of neurofilaments in the control of axon caliber, there is growing evidence based on transgenic mouse studies that neurofilaments can affect the dynamics and perhaps the function of other cytoskeletal elements, such as microtubules and actin filaments. Perturbations in phosphorylation or in metabolism of neurofilaments are frequently observed in neurodegenerative diseases. A down-regulation of mRNA encoding neurofilament proteins and the presence of neurofilament deposits are common features of human neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Parkinson's disease, and Alzheimer's disease. Although the extent to which neurofilament abnormalities contribute to pathogenesis in these human diseases remains unknown, emerging evidence, based primarily on transgenic mouse studies and on the discovery of deletion mutations in the NF-H gene of some ALS eases, suggests that disorganized neurofilaments can provoke selective degeneration and death of neurons. An interference of axonal transport by disorganized neurofilaments has been proposed as one possible mechanism of neurofilament-induced pathology. Other factors that can potentially lead to the accumulation of neurofilaments will be discussed as well as the emerging evidence for neurofilaments as being possible targets of oxidative damage by mutations in the superoxide dismutase enzyme (SOD1); such mutations are responsible for approximately 20% of familial ALS cases.
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Affiliation(s)
- J P Julien
- Centre for Research in Neuroscience, McGill University, Montreal, Canada
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