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Ding EA, Kumar S. Neurofilament Biophysics: From Structure to Biomechanics. Mol Biol Cell 2024; 35:re1. [PMID: 38598299 PMCID: PMC11151108 DOI: 10.1091/mbc.e23-11-0438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 03/25/2024] [Accepted: 04/04/2024] [Indexed: 04/12/2024] Open
Abstract
Neurofilaments (NFs) are multisubunit, neuron-specific intermediate filaments consisting of a 10-nm diameter filament "core" surrounded by a layer of long intrinsically disordered protein (IDP) "tails." NFs are thought to regulate axonal caliber during development and then stabilize the mature axon, with NF subunit misregulation, mutation, and aggregation featuring prominently in multiple neurological diseases. The field's understanding of NF structure, mechanics, and function has been deeply informed by a rich variety of biochemical, cell biological, and mouse genetic studies spanning more than four decades. These studies have contributed much to our collective understanding of NF function in axonal physiology and disease. In recent years, however, there has been a resurgence of interest in NF subunit proteins in two new contexts: as potential blood- and cerebrospinal fluid-based biomarkers of neuronal damage, and as model IDPs with intriguing properties. Here, we review established principles and more recent discoveries in NF structure and function. Where possible, we place these findings in the context of biophysics of NF assembly, interaction, and contributions to axonal mechanics.
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Affiliation(s)
- Erika A. Ding
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720
| | - Sanjay Kumar
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA 94158
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Aguilar G, Pagano N, Manuelidis L. Reduced Expression of Prion Protein With Increased Interferon-β Fail to Limit Creutzfeldt-Jakob Disease Agent Replication in Differentiating Neuronal Cells. Front Physiol 2022; 13:837662. [PMID: 35250638 PMCID: PMC8895124 DOI: 10.3389/fphys.2022.837662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 01/20/2022] [Indexed: 11/17/2022] Open
Abstract
Immortalized uninfected septal (SEP) neurons proliferate but after physiological mitotic arrest they express differentiated neuronal characteristics including enhanced cell-to-cell membrane contacts and ≥ 8 fold increases in host prion protein (PrP). We compared proliferating uninfected and Creutzfeldt-Jakob Disease (CJD) agent infected cells with their arrested counterparts over 33 days by quantitative mRNA and protein blot analyses. Surprisingly, uninfected arrested cells increased interferon-β (IFN-β) mRNA by 2.5–8 fold; IFN-β mRNA elevations were not previously associated with neuronal differentiation. SEP cells with high CJD infectivity titers produced a much larger 40–68-fold increase in IFN-β mRNA, a classic host anti-viral response that is virucidal for RNA but not DNA viruses. High titers of CJD agent also induced dramatic decreases in host PrP, a protein needed for productive agent replication. Uninfected arrested cells produced large sustained 20–30-fold increases in PrP mRNA and protein, whereas CJD arrested cells showed only transient small 5-fold increases in PrP. A > 10-fold increase in infectivity, but not PrP misfolding, induced host PrP reductions that can limit CJD agent replication. In contrast to neuronal lineage cells, functionally distinct migratory microglia with high titers of CJD agent do not induce an IFN-β mRNA response. Because they have 1/50th of PrP of an average brain cell, microglia would be unable to produce the many new infectious particles needed to induce a large IFN-β response by host cells. Instead, microglia and related cells can be persistent reservoirs of infection and spread. Phase separations of agent-associated molecules in neurons, microglia and other cell types can yield new insights into the molecular structure, persistent, and evasive behavior of CJD-type agents.
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Klimovich P, Rubina K, Sysoeva V, Semina E. New Frontiers in Peripheral Nerve Regeneration: Concerns and Remedies. Int J Mol Sci 2021; 22:13380. [PMID: 34948176 PMCID: PMC8703705 DOI: 10.3390/ijms222413380] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 11/30/2021] [Accepted: 12/07/2021] [Indexed: 01/08/2023] Open
Abstract
Topical advances in studying molecular and cellular mechanisms responsible for regeneration in the peripheral nervous system have highlighted the ability of the nervous system to repair itself. Still, serious injuries represent a challenge for the morphological and functional regeneration of peripheral nerves, calling for new treatment strategies that maximize nerve regeneration and recovery. This review presents the canonical view of the basic mechanisms of nerve regeneration and novel data on the role of exosomes and their transferred microRNAs in intracellular communication, regulation of axonal growth, Schwann cell migration and proliferation, and stromal cell functioning. An integrated comprehensive understanding of the current mechanistic underpinnings will open the venue for developing new clinical strategies to ensure full regeneration in the peripheral nervous system.
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Affiliation(s)
- Polina Klimovich
- National Cardiology Research Center Ministry of Health of the Russian Federation, Institute of Experimental Cardiology, 121552 Moscow, Russia; (P.K.); (E.S.)
- Faculty of Medicine, Lomonosov Moscow State University, 119991 Moscow, Russia;
| | - Kseniya Rubina
- Faculty of Medicine, Lomonosov Moscow State University, 119991 Moscow, Russia;
| | - Veronika Sysoeva
- Faculty of Medicine, Lomonosov Moscow State University, 119991 Moscow, Russia;
| | - Ekaterina Semina
- National Cardiology Research Center Ministry of Health of the Russian Federation, Institute of Experimental Cardiology, 121552 Moscow, Russia; (P.K.); (E.S.)
- Faculty of Medicine, Lomonosov Moscow State University, 119991 Moscow, Russia;
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Chan G, Morgan WH, Yu DY, Balaratnasingam C. Quantitative analysis of astrocyte and axonal density relationships: Glia to neuron ratio in the optic nerve laminar regions. Exp Eye Res 2020; 198:108154. [PMID: 32712181 DOI: 10.1016/j.exer.2020.108154] [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: 05/10/2020] [Revised: 07/06/2020] [Accepted: 07/16/2020] [Indexed: 12/01/2022]
Abstract
Astrocytes are critical for the maintenance of retinal ganglion cell (RGC) axonal function and viability, and form a key component of the functional neurovascular unit. Recently, we described the quantitative properties of astrocytes in relation to the capillary distributions in optic nerve laminar regions. Here, we provide a quantitative analysis of astrocytes and RGC axons in longitudinal sections of optic nerve tissue. Histological and immunocytochemical techniques are used to demonstrate the density of astrocytes, RGC axons and glia-neuron ratios across the pre laminar, lamina cribrosa and post laminar compartments of the optic nerve head (ONH). A study of human, pig, horse and rat optic nerves was performed and comparisons are made between species. This study demonstrates that the distribution of astrocytes correlates closely with the density of axonal processes, in accordance with the functional requirement of different regions of the ganglion cell axon. There was a consistency of glia-neuron ratios in the majority of laminar compartments, except for the human and rat prelaminar regions, which demonstrated lower ratios of astrocyte to axonal processes. The distribution of astrocytes may reflect a functional susceptibility to development of disease in the prelaminar region of the optic nerve. Interspecies comparison at the lamina cribrosa showed strikingly consistent glia-neuron ratios. Collectively, our findings suggest there may be a critical ratio of glia to neuron needed to maintain healthy cellular physiology across different laminar compartments of the optic nerve, with particular importance for the health of the lamina cribrosa region. It is possible that, in disease processes, the glia-neuron relationships across the different laminar compartments may be perturbed and this may be relevant for the development of glaucoma. Emerging technologies may further aid our understanding in how the physiology of optic nerve tissue cellular structure may be affected by changes to ONH characteristics and elevated intraocular pressure induced damage. Such findings may also permit the early identification of RGC axonal injury by identifying quantifiable changes in structural tissue architecture when pathophysiological pathways predominate.
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Affiliation(s)
- Geoffrey Chan
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Perth, Australia; Lions Eye Institute, The University of Western Australia, Perth, Australia.
| | - William H Morgan
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Perth, Australia; Lions Eye Institute, The University of Western Australia, Perth, Australia.
| | - Dao-Yi Yu
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Perth, Australia; Lions Eye Institute, The University of Western Australia, Perth, Australia.
| | - Chandrakumar Balaratnasingam
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Perth, Australia; Lions Eye Institute, The University of Western Australia, Perth, Australia.
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Kumar A, Xu Y, Du Y. Stem Cells from Human Trabecular Meshwork Hold the Potential to Develop into Ocular and Non-Ocular Lineages After Long-Term Storage. Stem Cells Dev 2019; 29:49-61. [PMID: 31680626 DOI: 10.1089/scd.2019.0169] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Stem cells from the eye hold a great potential for vision restoration and can also be used for regeneration in other tissues. In this study, we characterized the stem cell properties of Trabecular meshwork stem cells (TMSCs) after long-term cryopreservation (∼8 years). TMSCs derived from four donors were examined for their viability and proliferation, as well as stem cell marker expression. Spheroid formation, colony formation, and multipotency were investigated. We observed that TMSCs were fully viable with variable proliferation ability. They expressed the stem cell markers CD90, CD166, CD105, CD73, OCT4, SSEA4, Notch1, KLF4, ABCG2, Nestin, and HNK1 detected by flow cytometry, quantitative polymerase chain reaction, or immunofluorescent staining. They could form spheroids and colonies after thawing. All TMSCs were able to differentiate into osteocytes, neural cells, and trabecular meshwork (TM) cells, but not adipocytes. Differentiated TM cells responded to dexamethasone treatment with increased expression of myocilin and angiopoietin-like 7 (ANGPTL7). In a nutshell, our study demonstrated that TMSCs retain their stem cell properties after long-term cryopreservation and hence can be an effective cell therapy source for various clinical applications.
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Affiliation(s)
- Ajay Kumar
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Yi Xu
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Yiqin Du
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Developmental Biology, University of Pittsburgh, Pittsburgh, Pennsylvania.,McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
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Rodrigues ACZ, Messi ML, Wang ZM, Abba MC, Pereyra A, Birbrair A, Zhang T, O’Meara M, Kwan P, Lopez EIS, Willis MS, Mintz A, Files DC, Furdui C, Oppenheim RW, Delbono O. The sympathetic nervous system regulates skeletal muscle motor innervation and acetylcholine receptor stability. Acta Physiol (Oxf) 2019; 225:e13195. [PMID: 30269419 PMCID: PMC7224611 DOI: 10.1111/apha.13195] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 09/23/2018] [Accepted: 09/26/2018] [Indexed: 12/19/2022]
Abstract
AIM Symptoms of autonomic failure are frequently the presentation of advanced age and neurodegenerative diseases that impair adaptation to common physiologic stressors. The aim of this work was to examine the interaction between the sympathetic and motor nervous system, the involvement of the sympathetic nervous system (SNS) in neuromuscular junction (NMJ) presynaptic motor function, the stability of postsynaptic molecular organization, and the skeletal muscle composition and function. METHODS Since muscle weakness is a symptom of diseases characterized by autonomic dysfunction, we studied the impact of regional sympathetic ablation on muscle motor innervation by using transcriptome analysis, retrograde tracing of the sympathetic outflow to the skeletal muscle, confocal and electron microscopy, NMJ transmission by electrophysiological methods, protein analysis, and state of the art microsurgical techniques, in C57BL6, MuRF1KO and Thy-1 mice. RESULTS We found that the SNS regulates motor nerve synaptic vesicle release, skeletal muscle transcriptome, muscle force generated by motor nerve activity, axonal neurofilament phosphorylation, myelin thickness, and myofibre subtype composition and CSA. The SNS also modulates the levels of postsynaptic membrane acetylcholine receptor by regulating the Gαi2 -Hdac4-Myogenin-MuRF1pathway, which is prevented by the overexpression of the guanine nucleotide-binding protein Gαi2 (Q205L), a constitutively active mutant G protein subunit. CONCLUSION The SNS regulates NMJ transmission, maintains optimal Gαi2 expression, and prevents any increase in Hdac4, myogenin, MuRF1, and miR-206. SNS ablation leads to upregulation of MuRF1, muscle atrophy, and downregulation of postsynaptic AChR. Our findings are relevant to clinical conditions characterized by progressive decline of sympathetic innervation, such as neurodegenerative diseases and aging.
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Affiliation(s)
- Anna C. Z. Rodrigues
- Department of Internal Medicine, Gerontology, Wake Forest School of Medicine, Winston-Salem, North Carolina
- Neuroscience Program, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Maria L. Messi
- Department of Internal Medicine, Gerontology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Zhong-Min Wang
- Department of Internal Medicine, Gerontology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Martin C. Abba
- Basic and Applied Immunological Research Center (CINIBA), School of Medicine, National University of La Plata, Buenos Aires, Argentina
| | - Andrea Pereyra
- Department of Internal Medicine, Gerontology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Alexander Birbrair
- Department of Internal Medicine, Gerontology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Tan Zhang
- Department of Internal Medicine, Gerontology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Meaghan O’Meara
- Department of Internal Medicine, Gerontology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Ping Kwan
- Department of Internal Medicine, Gerontology, Wake Forest School of Medicine, Winston-Salem, North Carolina
- Neuroscience Program, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Elsa I. S. Lopez
- Department of Internal Medicine, Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Monte S. Willis
- Department of Pathology, McAllister Heart Institute, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina
| | - Akiva Mintz
- Department of Radiology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - D. Clark Files
- Department of Internal Medicine, Gerontology, Wake Forest School of Medicine, Winston-Salem, North Carolina
- Department of Internal Medicine, Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
- Department of Internal Medicine, Pulmonary, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Cristina Furdui
- Department of Internal Medicine, Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Ronald W. Oppenheim
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | - Osvaldo Delbono
- Department of Internal Medicine, Gerontology, Wake Forest School of Medicine, Winston-Salem, North Carolina
- Neuroscience Program, Wake Forest School of Medicine, Winston-Salem, North Carolina
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Local Acceleration of Neurofilament Transport at Nodes of Ranvier. J Neurosci 2018; 39:663-677. [PMID: 30541916 DOI: 10.1523/jneurosci.2272-18.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 10/24/2018] [Accepted: 10/26/2018] [Indexed: 11/21/2022] Open
Abstract
Myelinated axons are constricted at nodes of Ranvier. These constrictions are important physiologically because they increase the speed of saltatory nerve conduction, but they also represent potential bottlenecks for the movement of axonally transported cargoes. One type of cargo are neurofilaments, which are abundant space-filling cytoskeletal polymers that function to increase axon caliber. Neurofilaments move bidirectionally along axons, alternating between rapid movements and prolonged pauses. Strikingly, axon constriction at nodes is accompanied by a reduction in neurofilament number that can be as much as 10-fold in the largest axons. To investigate how neurofilaments navigate these constrictions, we developed a transgenic mouse strain that expresses a photoactivatable fluorescent neurofilament protein in neurons. We used the pulse-escape fluorescence photoactivation technique to analyze neurofilament transport in mature myelinated axons of tibial nerves from male and female mice of this strain ex vivo Fluorescent neurofilaments departed the activated region more rapidly in nodes than in flanking internodes, indicating that neurofilament transport is faster in nodes. By computational modeling, we showed that this nodal acceleration can be explained largely by a local increase in the duty cycle of neurofilament transport (i.e., the proportion of the time that the neurofilaments spend moving). We propose that this transient acceleration functions to maintain a constant neurofilament flux across nodal constrictions, much as the current increases where a river narrows its banks. In this way, neurofilaments are prevented from piling up in the flanking internodes, ensuring a stable neurofilament distribution and uniform axonal morphology across these physiologically important axonal domains.SIGNIFICANCE STATEMENT Myelinated axons are constricted at nodes of Ranvier, resulting in a marked local decrease in neurofilament number. These constrictions are important physiologically because they increase the efficiency of saltatory nerve conduction, but they also represent potential bottlenecks for the axonal transport of neurofilaments, which move along axons in a rapid intermittent manner. Imaging of neurofilament transport in mature myelinated axons ex vivo reveals that neurofilament polymers navigate these nodal axonal constrictions by accelerating transiently, much as the current increases where a river narrows its banks. This local acceleration is necessary to ensure a stable axonal morphology across nodal constrictions, which may explain the vulnerability of nodes of Ranvier to neurofilament accumulations in animal models of neurotoxic neuropathies and neurodegenerative diseases.
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Wang H, Wu M, Zhan C, Ma E, Yang M, Yang X, Li Y. Neurofilament proteins in axonal regeneration and neurodegenerative diseases. Neural Regen Res 2015; 7:620-6. [PMID: 25745454 PMCID: PMC4346988 DOI: 10.3969/j.issn.1673-5374.2012.08.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 02/05/2012] [Indexed: 12/21/2022] Open
Abstract
Neurofilament protein is a component of the mature neuronal cytoskeleton, and it interacts with the zygosome, which is mediated by neurofilament-related proteins. Neurofilament protein regulates enzyme function and the structure of linker proteins. In addition, neurofilament gene expression plays an important role in nervous system development. Previous studies have shown that neurofilament gene transcriptional regulation is crucial for neurofilament protein expression, especially in axonal regeneration and degenerative diseases. Post-transcriptional regulation increased neurofilament protein gene transcription during axonal regeneration, ultimately resulting in a pattern of neurofilament protein expression. An expression imbalance of post-transcriptional regulatory proteins and other disorders could lead to amyotrophic lateral sclerosis or other neurodegenerative diseases. These findings indicated that after transcription, neurofilament protein regulated expression of related proteins and promoted regeneration of damaged axons, suggesting that regulation disorders could lead to neurodegenerative diseases.
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Affiliation(s)
- Haitao Wang
- Department of Spine Surgery, China-Japan Union Hospital, Jilin University, Changchun 130033, Jilin Province, China
| | - Minfei Wu
- Department of Spine Surgery, China-Japan Union Hospital, Jilin University, Changchun 130033, Jilin Province, China
| | - Chuanjun Zhan
- Department of Spine Surgery, China-Japan Union Hospital, Jilin University, Changchun 130033, Jilin Province, China
| | - Enyuan Ma
- Department of Orthopedic Surgery, Beihua University Affiliated Hospital, Jilin 132000, Jilin Province, China
| | - Maoguang Yang
- Department of Spine Surgery, China-Japan Union Hospital, Jilin University, Changchun 130033, Jilin Province, China
| | - Xiaoyu Yang
- Department of Spine Surgery, China-Japan Union Hospital, Jilin University, Changchun 130033, Jilin Province, China
| | - Yingpu Li
- Department of Spine Surgery, China-Japan Union Hospital, Jilin University, Changchun 130033, Jilin Province, China
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Regulation of mitochondrial transport and inter-microtubule spacing by tau phosphorylation at the sites hyperphosphorylated in Alzheimer's disease. J Neurosci 2012; 32:2430-41. [PMID: 22396417 DOI: 10.1523/jneurosci.5927-11.2012] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The microtubule-associated protein Tau is a major component of the neurofibrillary tangles that serve as a neuropathological hallmark of Alzheimer's disease. Tau is a substrate for protein phosphorylation at multiple sites and occurs in tangles in a hyperphosphorylated state. However, the physiological functions of Tau phosphorylation or how it may contribute mechanistically to Alzheimer's pathophysiology are not completely understood. Here, we examined the function of human Tau phosphorylation at three sites, Ser199, Ser202, and Thr205, which together comprise the AT8 sites that mark abnormal phosphorylation in Alzheimer's disease. Overexpression of wild-type Tau or mutated forms in which these sites had been changed to either unphosphorylatable alanines or phosphomimetic aspartates inhibited mitochondrial movement in the neurite processes of PC12 cells as well as the axons of mouse brain cortical neurons. However, the greatest effects on mitochondrial translocation were induced by phosphomimetic mutations. These mutations also caused expansion of the space between microtubules in cultured cells when membrane tension was reduced by disrupting actin filaments. Thus, Tau phosphorylation at the AT8 sites may have meaningful effects on mitochondrial movement, likely by controlling microtubule spacing. Hyperphosphorylation of the AT8 sites may contribute to axonal degeneration by disrupting mitochondrial transport in Alzheimer's disease.
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Szaro BG, Strong MJ. Regulation of Cytoskeletal Composition in Neurons: Transcriptional and Post-transcriptional Control in Development, Regeneration, and Disease. ADVANCES IN NEUROBIOLOGY 2011. [DOI: 10.1007/978-1-4419-6787-9_24] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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Szaro BG, Strong MJ. Post-transcriptional control of neurofilaments: New roles in development, regeneration and neurodegenerative disease. Trends Neurosci 2010; 33:27-37. [DOI: 10.1016/j.tins.2009.10.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2009] [Revised: 09/21/2009] [Accepted: 10/06/2009] [Indexed: 12/17/2022]
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Rangaraju S, Hankins D, Madorsky I, Madorsky E, Lee WH, Carter CS, Leeuwenburgh C, Notterpek L. Molecular architecture of myelinated peripheral nerves is supported by calorie restriction with aging. Aging Cell 2009; 8:178-91. [PMID: 19239416 DOI: 10.1111/j.1474-9726.2009.00460.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Peripheral nerves from aged animals exhibit features of degeneration, including marked fiber loss, morphological irregularities in myelinated axons and notable reduction in the expression of myelin proteins. To investigate how protein homeostatic mechanisms change with age within the peripheral nervous system, we isolated Schwann cells from the sciatic nerves of young and old rats. The responsiveness of cells from aged nerves to stress stimuli is weakened, which in part may account for the observed age-associated alterations in glial and axonal proteins in vivo. Although calorie restriction is known to slow the aging process in the central nervous system, its influence on peripheral nerves has not been investigated in detail. To determine if dietary restriction is beneficial for peripheral nerve health and glial function, we studied sciatic nerves from rats of four distinct ages (8, 18, 29 and 38 months) kept on an ad libitum (AL) or a 40% calorie restricted diet. Age-associated reduction in the expression of the major myelin proteins and widening of the nodes of Ranvier are attenuated by the dietary intervention, which is paralleled with the maintenance of a differentiated Schwann cell phenotype. The improvements in nerve architecture with diet restriction, in part, are underlined by sustained expression of protein chaperones and markers of the autophagy-lysosomal pathway. Together, the in vitro and in vivo results suggest that there might be an age-limit by which dietary intervention needs to be initiated to elicit a beneficial response on peripheral nerve health.
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Affiliation(s)
- Sunitha Rangaraju
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL 32610-0244, USA
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Gotow T. Neurons in the Klotho Mutant Mouse Show Biochemical and Morphological Characteristics Resembling Age-Related Disorders. Tzu Chi Med J 2008. [DOI: 10.1016/s1016-3190(08)60030-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Miller KE, Heidemann SR. What is slow axonal transport? Exp Cell Res 2008; 314:1981-90. [DOI: 10.1016/j.yexcr.2008.03.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Revised: 02/29/2008] [Accepted: 03/06/2008] [Indexed: 12/26/2022]
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Shiozaki M, Yoshimura K, Shibata M, Koike M, Matsuura N, Uchiyama Y, Gotow T. Morphological and biochemical signs of age-related neurodegenerative changes in klotho mutant mice. Neuroscience 2008; 152:924-41. [PMID: 18343589 DOI: 10.1016/j.neuroscience.2008.01.032] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Revised: 01/07/2008] [Accepted: 01/22/2008] [Indexed: 12/23/2022]
Abstract
Klotho mutant mice, defective in the klotho gene, develop multiple age-related disorders with very short lifespans. Introduction of the exogenous klotho gene into these mutant mice leads to an improvement in their phenotypes, while overexpression of this gene in wild-type mice significantly extends their lifespan. These observations suggest that the klotho gene/protein has an anti-aging function. Since there have been only a few reports with some disagreement about results on the CNS of the mutant mice, we tried to clarify whether the CNS neurons generate aging-like features, even in premature stages, using biochemical and morphological approaches. Results obtained from the mutant mice, when compared with wild-type mice, were as follows. Neurofilaments (NFs) were increased significantly in axons, with the subunit proteins showing a significant enhancement in phosphorylation or expression of NF-H or NF-L, respectively. Microtubules in Purkinje cell dendrites were closer to each other, and in the CNS tissue tubulin was unaltered, but microtubule-associated protein (MAP) 2 was significantly reduced in expression. Neuronal cellular organelles were morphologically disordered. Lysosomes, cathepsin D and light chain 3 of MAP1A/B (LC3) were augmented with the appearance of putative autophagy-related structures. Antiapoptotic Bcl-xL and proapoptotic Bax were reduced and enhanced, respectively, and mitogen-activated protein kinase was reduced. Synapse-related proteins and structures were decreased. Neuronal degeneration was evident in hippocampal pyramidal cells, and possibly in Purkinje cells. Astrocytic glial filaments and glial fibrillary acidic protein were increased in density and expression, respectively. Together, the CNS neuronal alterations in klotho mutant mice were quite similar to those found in aged animals, including even premature death, so this mouse should be a more appropriate animal model for CNS aging than those previously reported.
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Affiliation(s)
- M Shiozaki
- Laboratory of Cell Biology, College of Nutrition, Koshien University, 10-1 Momijigaoka, Takarazuka, Hyogo 665-0006, Japan
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Cross DJ, Flexman JA, Anzai Y, Maravilla KR, Minoshima S. Age-related decrease in axonal transport measured by MR imaging in vivo. Neuroimage 2007; 39:915-26. [PMID: 17980625 DOI: 10.1016/j.neuroimage.2007.08.036] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2007] [Revised: 07/18/2007] [Accepted: 08/17/2007] [Indexed: 10/22/2022] Open
Abstract
Axonal transport is a crucial process for neuronal homeostasis and cell functions. In vitro studies have indicated transport rates decrease with age. Disruption of axonal transport has been implicated in age-associated neurodegenerative disorders. We hypothesized that aged rats would show decreased transport in the brain, which could be measured using in vivo manganese-enhanced MR imaging (Mn-MRI) and parametric estimation. Serial T1-weighted images were obtained at pre- and post-administration of MnCl(2) in rats scanned longitudinally (n=4) and in a separate aged group (n=3). Subtraction analysis was performed for group-wise statistical comparison on a pixel-by-pixel basis. Change in intensity over time was plotted for the olfactory bulb and anterior and posterior olfactory tract. Bulk transport of material was estimated over an initial 72 h. Tracer kinetic estimation of time-intensity data, based on a mass transport model, used intensity change in the bulb as input function for subsequent changes in the tract. Time to the peak of Mn(2+) flow was estimated for both anterior and posterior tracts. Results indicated age-related decreases in axonal transport rate and bulk transport of material in the olfactory tract of living rat brains. Longitudinally scanned, mid-age group was decreased by 58% and the aged group by 71% of young rate (neuronal transport=4.07+/-1.24 mm/h, 1.72+/-0.89 mm/h, and 1.16+/-0.18 mm/h for young, mid-age, and aged, respectively). Neuronal transport rate decreases correlated with increased age. The use of kinetic analysis combined with dynamic manganese enhanced MR imaging provides a unique opportunity to study this important neuronal process.
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Affiliation(s)
- Donna J Cross
- Washington National Regional Primate Center, Washington, USA
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Schumacher M, Guennoun R, Ghoumari A, Massaad C, Robert F, El-Etr M, Akwa Y, Rajkowski K, Baulieu EE. Novel perspectives for progesterone in hormone replacement therapy, with special reference to the nervous system. Endocr Rev 2007; 28:387-439. [PMID: 17431228 DOI: 10.1210/er.2006-0050] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The utility and safety of postmenopausal hormone replacement therapy has recently been put into question by large clinical trials. Their outcome has been extensively commented upon, but discussions have mainly been limited to the effects of estrogens. In fact, progestagens are generally only considered with respect to their usefulness in preventing estrogen stimulation of uterine hyperplasia and malignancy. In addition, various risks have been attributed to progestagens and their omission from hormone replacement therapy has been considered, but this may underestimate their potential benefits and therapeutic promises. A major reason for the controversial reputation of progestagens is that they are generally considered as a single class. Moreover, the term progesterone is often used as a generic one for the different types of both natural and synthetic progestagens. This is not appropriate because natural progesterone has properties very distinct from the synthetic progestins. Within the nervous system, the neuroprotective and promyelinating effects of progesterone are promising, not only for preventing but also for reversing age-dependent changes and dysfunctions. There is indeed strong evidence that the aging nervous system remains at least to some extent sensitive to these beneficial effects of progesterone. The actions of progesterone in peripheral target tissues including breast, blood vessels, and bones are less well understood, but there is evidence for the beneficial effects of progesterone. The variety of signaling mechanisms of progesterone offers exciting possibilities for the development of more selective, efficient, and safe progestagens. The recognition that progesterone is synthesized by neurons and glial cells requires a reevaluation of hormonal aging.
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Affiliation(s)
- Michael Schumacher
- INSERM UMR 788, 80, rue du Général Leclerc, 94276 Kremlin-Bicêtre, France.
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18
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Abstract
Balance in the elderly population is a major concern given the often catastrophic and disabling consequences of fall-related injuries. Structural and functional declines of the somatosensory system occur with aging and potentially contribute to postural instability in older adults. The objectives of this article are: (1) to discuss the evidence regarding age-related anatomical and physiological changes that occur in the peripheral proprioceptive and cutaneous systems, (2) to relate the basic science research to the current evidence regarding clinical changes associated with normal aging, and (3) to review the evidence regarding age-related proprioceptive and cutaneous clinical changes and relate it to research examining balance performance in older adults. The article is organized by an examination of the receptors responsible for activating afferent pathways (muscle spindle, golgi tendon organ, and articular and cutaneous receptors) and the corresponding sensory afferent fibers and neurons. It integrates basic science laboratory findings with clinical evidence suggesting that advanced aging results in a decline in cutaneous sensation and proprioception. The potential relationship between postural instability and sensory impairments in older adults also is discussed. Current laboratory and clinical evidence suggests that aging results in: (1) diverse and nonuniform declines in the morphology and physiological function of the various sensory structures examined, (2) preferential loss of distal large myelinated sensory fibers and receptors, and (3) impaired distal lower-extremity proprioception, vibration and discriminative touch, and balance. These findings provide foundational knowledge that emphasizes the importance of using reliable and valid sensory testing protocols for older adults and the need for further research that clarifies the relationship between sensory impairment and balance.
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Affiliation(s)
- Scott W Shaffer
- College of Health Sciences, University of Kentucky, Lexington, KY 40536-0200, USA.
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Yu S, Son F, Yu J, Zhao X, Yu L, Li G, Xie K. Acrylamide alters cytoskeletal protein level in rat sciatic nerves. Neurochem Res 2006; 31:1197-204. [PMID: 17043767 DOI: 10.1007/s11064-006-9176-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2006] [Accepted: 09/15/2006] [Indexed: 11/24/2022]
Abstract
Occupational exposure and experimental intoxication with acrylamide (ACR) produce neuropathy characterized by nerve degeneration. To investigate the mechanism of ACR-induced neuropathy, male adult Wistar rats were given ACR (20, 40 mg/kg i.p. 3 days/week) for 8 weeks. Sciatic nerves were Triton-extracted and centrifuged at a high speed (100,000 x g) to yield pellet and supernatant fractions. The contents of six cytoskeletal proteins (NF-L, NF-M, NF-H, alpha-tubulin, beta-tubulin, and beta-actin) in both fractions were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Results showed that the three neurofilament (NF) subunits (NF-L, NF-M, NF-H) in both the pellet and the supernatant fraction decreased significantly (P < 0.01) in the high-dosing group, except for NF-M in the pellet. alpha-tubulin, beta-tubulin, and beta-actin increased significantly in the supernatant (P < 0.01), whereas both alpha-tubulin and beta-tubulin decreased significantly in the pellet (P < 0.01). However, beta-actin was not altered significantly in the sciatic nerves pellet. These findings suggest that ACR altered the cytoskeletal protein level in sciatic nerve, which may be one of the molecular mechanisms of ACR-induced peripheral neuropathy.
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Affiliation(s)
- Sufang Yu
- Institute of toxicology, Shandong University, 44 Wenhua Xi Road, Jinan, 250012, Shandong, P.R. China
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20
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Abstract
In contrast to most eukaryotic cells, neurons possess long, highly branched processes called axons and dendrites. In large mammals, such as humans, some axons reach lengths of over 1 m. These lengths pose a major challenge to the movement of proteins, vesicles, and organelles between presynaptic sites and cell bodies. To overcome this challenge axons and dendrites rely upon specialized transport machinery consisting of cytoskeletal motor proteins generating directed movements along cytoskeletal tracks. Not only are these transport systems crucial to maintain neuronal viability and differentiation, but considerable experimental evidence suggests that failure of axonal transport may play a role in the development or progression of neurological diseases such as Alzheimer's disease.
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Affiliation(s)
- Gorazd B Stokin
- Institute of Clinical Neurophysiology, Division of Neurology, University Medical Center, SI-1525 Ljubljana, Slovenia.
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Lopachin RM, Jortner BS, Reid ML, Monir A. Gamma-Diketone central neuropathy: quantitative analyses of cytoskeletal components in myelinated axons of the rat rubrospinal tract. Neurotoxicology 2005; 26:1021-30. [PMID: 15964632 DOI: 10.1016/j.neuro.2005.04.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Accepted: 04/27/2005] [Indexed: 10/25/2022]
Abstract
Loss of axon caliber is a primary component of gamma-diketone neuropathy [LoPachin RM, DeCaprio AP. gamma-Diketone central neuropathy: axon atrophy and the role of cytoskeletal protein adduction. Toxicol Appl Pharmacol 2004;199:20-34]. It is possible that this effect is mediated by changes in the density of cytoskeletal components and corresponding spatial relationships. To examine this possibility, morphometric methods were used to quantify the effects of 2,5-hexanedione (HD) intoxication on neurofilament-microtubule densities and nearest neighbor distances in myelinated rubrospinal axons. Rats were exposed to HD at one of two daily dose-rates (175 or 400 mg/kg per day, gavage) until a moderate level of neurotoxicity was achieved (99 or 21 days of intoxication, respectively) as determined by gait analysis and measurements of hindlimb grip strength. Results indicate that, regardless of dose-rate, HD intoxication did not cause changes in axonal neurofilament (NF) density, but did significantly increase microtubule (MT) density. No consistent alterations in interneurofilament or NF-MT distances were detected by ultrastructural morphometric analyses. These data suggest that the axon atrophy induced by HD was not mediated by major disruptions of stationary cytoskeletal organization. Recent biochemical studies of spinal cord from HD intoxicated rats showed that, although the NF protein content in the stationary cytoskeleton (polymer fraction) was not affected, the mobile subunit pool was depleted substantially [LoPachin RM, He D, Reid ML, Opanashuk LA. 2,5-Hexanedione-induced changes in the monomeric neurofilament protein content of rat spinal cord fractions. Toxicol Appl Pharmacol 2004;198:61-73]. The stability of the polymer fraction during HD intoxication is consistent with the absence of significant ultrastructural modifications noted in the present study. Together, these findings implicate loss of mobile NF proteins as the primary mechanism of axon atrophy.
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Affiliation(s)
- Richard M Lopachin
- Department of Anesthesiology, Albert Einstein College of Medicine, Montefiore Medical Center, Moses Research Tower-7, 111 E. 2210th St., Bronx, NY 10467-2490, USA.
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