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Kotaich F, Caillol D, Bomont P. Neurofilaments in health and Charcot-Marie-Tooth disease. Front Cell Dev Biol 2023; 11:1275155. [PMID: 38164457 PMCID: PMC10758125 DOI: 10.3389/fcell.2023.1275155] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 10/02/2023] [Indexed: 01/03/2024] Open
Abstract
Neurofilaments (NFs) are the most abundant component of mature neurons, that interconnect with actin and microtubules to form the cytoskeleton. Specifically expressed in the nervous system, NFs present the particularity within the Intermediate Filament family of being formed by four subunits, the neurofilament light (NF-L), medium (NF-M), heavy (NF-H) proteins and α-internexin or peripherin. Here, we review the current knowledge on NF proteins and neurofilaments, from their domain structures and their model of assembly to the dynamics of their transport and degradation along the axon. The formation of the filament and its behaviour are regulated by various determinants, including post-transcriptional (miRNA and RBP proteins) and post-translational (phosphorylation and ubiquitination) modifiers. Altogether, the complex set of modifications enable the neuron to establish a stable but elastic NF array constituting the structural scaffold of the axon, while permitting the local expression of NF proteins and providing the dynamics necessary to fulfil local demands and respond to stimuli and injury. Thus, in addition to their roles in mechano-resistance, radial axonal outgrowth and nerve conduction, NFs control microtubule dynamics, organelle distribution and neurotransmission at the synapse. We discuss how the studies of neurodegenerative diseases with NF aggregation shed light on the biology of NFs. In particular, the NEFL and NEFH genes are mutated in Charcot-Marie-Tooth (CMT) disease, the most common inherited neurological disorder of the peripheral nervous system. The clinical features of the CMT forms (axonal CMT2E, CMT2CC; demyelinating CMT1F; intermediate I-CMT) with symptoms affecting the central nervous system (CNS) will allow us to further investigate the physiological roles of NFs in the brain. Thus, NF-CMT mouse models exhibit various degrees of sensory-motor deficits associated with CNS symptoms. Cellular systems brought findings regarding the dominant effect of NF-L mutants on NF aggregation and transport, although these have been recently challenged. Neurofilament detection without NF-L in recessive CMT is puzzling, calling for a re-examination of the current model in which NF-L is indispensable for NF assembly. Overall, we discuss how the fundamental and translational fields are feeding each-other to increase but also challenge our knowledge of NF biology, and to develop therapeutic avenues for CMT and neurodegenerative diseases with NF aggregation.
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Affiliation(s)
| | | | - Pascale Bomont
- ERC team, NeuroMyoGene Institute-Pathophysiology and Genetics of Neuron and Muscle, Inserm U1315, CNRS UMR5261, University of Lyon 1, Lyon, France
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2
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Stone EJ, Kolb SJ, Brown A. A review and analysis of the clinical literature on Charcot-Marie-Tooth disease caused by mutations in neurofilament protein L. Cytoskeleton (Hoboken) 2021; 78:97-110. [PMID: 33993654 PMCID: PMC10174713 DOI: 10.1002/cm.21676] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 05/05/2021] [Accepted: 05/06/2021] [Indexed: 01/22/2023]
Abstract
Charcot-Marie-Tooth disease (CMT) is one of the most common inherited neurological disorders and can be caused by mutations in over 100 different genes. One of the causative genes is NEFL on chromosome 8 which encodes neurofilament light protein (NEFL), one of five proteins that co-assemble to form neurofilaments. At least 34 different CMT-causing mutations in NEFL have been reported which span the head, rod, and tail domains of the protein. The majority of these mutations are inherited dominantly, but some are inherited recessively. The resulting disease is classified variably in clinical reports based on electrodiagnostic studies as either axonal (type 2; CMT2E), demyelinating (type 1; CMT1F), or a form intermediate between the two (dominant intermediate; DI-CMTG). In this article, we first present a brief introduction to CMT and neurofilaments. We then collate and analyze the data from the clinical literature on the disease classification, age of onset and electrodiagnostic test results for the various mutations. We find that mutations in the head, rod, and tail domains can all cause disease with early onset and profound neurological impairment, with a trend toward greater severity for head domain mutations. We also find that the disease classification does not correlate with specific mutation or domain. In fact, different individuals with the same mutation can be classified as having axonal, demyelinating, or dominant intermediate forms of the disease. This suggests that the classification of the disease as CMT2E, CMT1F or DI-CMTG has more to do with variable disease presentation than to differences in the underlying disease mechanism, which is most likely primarily axonal in all cases.
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Affiliation(s)
- Elizabeth J Stone
- Department of Neuroscience, Ohio State University, Columbus, Ohio, USA.,Neuroscience Graduate Program, Ohio State University, Columbus, Ohio, USA
| | - Stephen J Kolb
- Department of Neurology, Ohio State University, Columbus, Ohio, USA.,Department of Biological Chemistry and Pharmacology, Ohio State University, Columbus, Ohio, USA
| | - Anthony Brown
- Department of Neuroscience, Ohio State University, Columbus, Ohio, USA
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3
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Fenn JD, Monsma PC, Brown A. Axonal neurofilaments exhibit frequent and complex folding behaviors. Cytoskeleton (Hoboken) 2019; 75:258-280. [PMID: 29683261 DOI: 10.1002/cm.21448] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 03/30/2018] [Accepted: 04/03/2018] [Indexed: 01/19/2023]
Abstract
Neurofilaments are flexible cytoskeletal polymers that are capable of folding and unfolding between their bouts of bidirectional movement along axons. Here we present a detailed characterization of this behavior in cultured neurons using kymograph analysis with approximately 30 ms temporal resolution. We analyzed 781 filaments ranging from 0.6-42 µm in length. We observed complex behaviors including pinch folds, hairpin folds, orientation changes (flips), and occasional severing and annealing events. On average, the filaments spent approximately 40% of their time in some sort of folded configuration. A small proportion of filaments (4%) moved while folded, but most (96%) moved in an outstretched configuration. Collectively, our observations suggest that motors may interact with neurofilaments at multiple points along their length, but preferentially at their ends. In addition, the prevalence of neurofilament folding and the tendency of neurofilaments to straighten out when they move, suggest that an important function of the movement of these polymers in axons may be to maintain them in an outstretched and longitudinally co-aligned configuration. Thus, neurofilament movement may function as much to organize these polymers as to move them, and this could explain why they spend so much time engaged in apparently unproductive bidirectional movement.
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Affiliation(s)
- J Daniel Fenn
- Department of Neuroscience, Ohio State University, Columbus, Ohio, 43210.,Medical Scientist Training Program, Ohio State University, Columbus, Ohio, 43210
| | - Paula C Monsma
- Department of Neuroscience, Ohio State University, Columbus, Ohio, 43210
| | - Anthony Brown
- Department of Neuroscience, Ohio State University, Columbus, Ohio, 43210
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4
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Malacrida A, Meregalli C, Rodriguez-Menendez V, Nicolini G. Chemotherapy-Induced Peripheral Neuropathy and Changes in Cytoskeleton. Int J Mol Sci 2019; 20:E2287. [PMID: 31075828 PMCID: PMC6540147 DOI: 10.3390/ijms20092287] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 05/06/2019] [Accepted: 05/07/2019] [Indexed: 12/23/2022] Open
Abstract
Despite the different antineoplastic mechanisms of action, peripheral neurotoxicity induced by all chemotherapy drugs (anti-tubulin agents, platinum compounds, proteasome inhibitors, thalidomide) is associated with neuron morphological changes ascribable to cytoskeleton modifications. The "dying back" degeneration of distal terminals (sensory nerves) of dorsal root ganglia sensory neurons, observed in animal models, in in vitro cultures and biopsies of patients is the most evident hallmark of the perturbation of the cytoskeleton. On the other hand, in highly polarized cells like neurons, the cytoskeleton carries out its role not only in axons but also has a fundamental role in dendrite plasticity and in the organization of soma. In the literature, there are many studies focused on the antineoplastic-induced alteration of microtubule organization (and consequently, fast axonal transport defects) while very few studies have investigated the effect of the different classes of drugs on microfilaments, intermediate filaments and associated proteins. Therefore, in this review, we will focus on: (1) Highlighting the fundamental role of the crosstalk among the three filamentous subsystems and (2) investigating pivotal cytoskeleton-associated proteins.
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Affiliation(s)
- Alessio Malacrida
- School of Medicine and Surgery, Experimental Neurology Unit and Milan Center for Neuroscience, University of Milano-Bicocca, via Cadore 48, 20900 Monza, MB, Italy.
| | - Cristina Meregalli
- School of Medicine and Surgery, Experimental Neurology Unit and Milan Center for Neuroscience, University of Milano-Bicocca, via Cadore 48, 20900 Monza, MB, Italy.
| | - Virginia Rodriguez-Menendez
- School of Medicine and Surgery, Experimental Neurology Unit and Milan Center for Neuroscience, University of Milano-Bicocca, via Cadore 48, 20900 Monza, MB, Italy.
| | - Gabriella Nicolini
- School of Medicine and Surgery, Experimental Neurology Unit and Milan Center for Neuroscience, University of Milano-Bicocca, via Cadore 48, 20900 Monza, MB, Italy.
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5
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Okrugin BM, Richter RP, Leermakers FAM, Neelov IM, Borisov OV, Zhulina EB. Structure and properties of polydisperse polyelectrolyte brushes studied by self-consistent field theory. SOFT MATTER 2018; 14:6230-6242. [PMID: 30027975 DOI: 10.1039/c8sm01138a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Two complementary self-consistent field theoretical approaches are used to analyze the equilibrium structure of binary and ternary brushes of polyions with different degrees of polymerization. Stratification in binary brushes is predicted: the shorter chains are entirely embedded in the proximal sublayer depleted of end-points of longer chains while the peripheral sublayer contains exclusively terminal segments of longer chains. The boundary between sublayers is enriched with counterions that neutralize the residual charge of the proximal sublayer. These analytical predictions for binary brushes are confirmed and extended to ternary brushes using the numerical Scheutjens-Fleer approach.
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Affiliation(s)
- Boris M Okrugin
- CIC biomaGUNE, Biosurface Lab, Paseo Miramon 182, 20014 San Sebastian, Spain
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6
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Yuan A, Rao MV, Veeranna, Nixon RA. Neurofilaments and Neurofilament Proteins in Health and Disease. Cold Spring Harb Perspect Biol 2017; 9:9/4/a018309. [PMID: 28373358 DOI: 10.1101/cshperspect.a018309] [Citation(s) in RCA: 431] [Impact Index Per Article: 61.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
SUMMARYNeurofilaments (NFs) are unique among tissue-specific classes of intermediate filaments (IFs) in being heteropolymers composed of four subunits (NF-L [neurofilament light]; NF-M [neurofilament middle]; NF-H [neurofilament heavy]; and α-internexin or peripherin), each having different domain structures and functions. Here, we review how NFs provide structural support for the highly asymmetric geometries of neurons and, especially, for the marked radial expansion of myelinated axons crucial for effective nerve conduction velocity. NFs in axons extensively cross-bridge and interconnect with other non-IF components of the cytoskeleton, including microtubules, actin filaments, and other fibrous cytoskeletal elements, to establish a regionally specialized network that undergoes exceptionally slow local turnover and serves as a docking platform to organize other organelles and proteins. We also discuss how a small pool of oligomeric and short filamentous precursors in the slow phase of axonal transport maintains this network. A complex pattern of phosphorylation and dephosphorylation events on each subunit modulates filament assembly, turnover, and organization within the axonal cytoskeleton. Multiple factors, and especially turnover rate, determine the size of the network, which can vary substantially along the axon. NF gene mutations cause several neuroaxonal disorders characterized by disrupted subunit assembly and NF aggregation. Additional NF alterations are associated with varied neuropsychiatric disorders. New evidence that subunits of NFs exist within postsynaptic terminal boutons and influence neurotransmission suggests how NF proteins might contribute to normal synaptic function and neuropsychiatric disease states.
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Affiliation(s)
- Aidong Yuan
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, New York 10962.,Department of Psychiatry, New York University School of Medicine, New York, New York 10016
| | - Mala V Rao
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, New York 10962.,Department of Psychiatry, New York University School of Medicine, New York, New York 10016
| | - Veeranna
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, New York 10962.,Department of Psychiatry, New York University School of Medicine, New York, New York 10016
| | - Ralph A Nixon
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, New York 10962.,Department of Psychiatry, New York University School of Medicine, New York, New York 10016.,Cell Biology, New York University School of Medicine, New York, New York 10016
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7
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Deek J, Chung PJ, Safinya CR. Neurofilament networks: Salt-responsive hydrogels with sidearm-dependent phase behavior. Biochim Biophys Acta Gen Subj 2016; 1860:1560-9. [PMID: 26993199 DOI: 10.1016/j.bbagen.2016.03.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 02/28/2016] [Accepted: 03/11/2016] [Indexed: 10/22/2022]
Abstract
BACKGROUND Neurofilaments (NFs) - the neuron-specific intermediate filament proteins - are assembled into 10nm wide filaments in a tightly controlled ratio of three different monomer types: NF-Low (NF-L), NF-Medium (NF-M), and NF-High (NF-H). Previous work on reconstituted bovine NF hydrogels has shown the dependence of network properties, including filament alignment and spacing, on the subunit composition. METHODS We use polarized optical microscopy and SAXS to explore the full salt-dependent phase behavior of reconstituted bovine NF networks as a function of various binary and ternary subunit ratios. RESULTS We observe three salt-induced liquid crystalline phases: the liquid-ordered B(G) and N(G) phases, and the disordered I(G) phase. We note the emergent sidearm roles, particularly that of NF-H in driving the parallel to cross-filament transition, and the counter-role of NF-M in suppressing the I(G) phase. CONCLUSIONS In copolymers of NF-LH, NF-H shifts the I(G) to N(G) transition to nearer physiological salt concentrations, as compared to NF-M in copolymers of NF-LM. For ternary mixtures, the role of NF-H is modulated by the ratio of NF-M, where beneath 10wt.% NF-M, NF-H drives the transition to the disordered phase, and above which NF-H increases interfilament spacing. GENERAL SIGNIFICANCE Understanding the role of individual subunits in regulating the network structure will enable us to understand the mechanisms that drive the dysfunction of these networks, as observed in diseased conditions.
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Affiliation(s)
- Joanna Deek
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106, United States.
| | - Peter J Chung
- Department of Physics, University of California, Santa Barbara, CA 93106, United States; Department of Materials, University of California, Santa Barbara, CA 93106, United States; Department of Molecular, Cellular, & Developmental Biology, University of California, Santa Barbara, CA 93106, United States.
| | - Cyrus R Safinya
- Department of Physics, University of California, Santa Barbara, CA 93106, United States; Department of Materials, University of California, Santa Barbara, CA 93106, United States; Department of Molecular, Cellular, & Developmental Biology, University of California, Santa Barbara, CA 93106, United States.
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8
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Targeting caspase-6 and caspase-8 to promote neuronal survival following ischemic stroke. Cell Death Dis 2015; 6:e1967. [PMID: 26539914 PMCID: PMC4670918 DOI: 10.1038/cddis.2015.272] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 08/18/2015] [Accepted: 08/24/2015] [Indexed: 01/06/2023]
Abstract
Previous studies show that caspase-6 and caspase-8 are involved in neuronal apoptosis and regenerative failure after trauma of the adult central nervous system (CNS). In this study, we evaluated whether caspase-6 or -8 inhibitors can reduce cerebral or retinal injury after ischemia. Cerebral infarct volume, relative to appropriate controls, was significantly reduced in groups treated with caspase-6 or -8 inhibitors. Concomitantly, these treatments also reduced neurological deficits, reduced edema, increased cell proliferation, and increased neurofilament levels in the injured cerebrum. Caspase-6 and -8 inhibitors, or siRNAs, also increased retinal ganglion cell survival at 14 days after ischemic injury. Caspase-6 or -8 inhibition also decreased caspase-3, -6, and caspase-8 cleavage when assayed by western blot and reduced caspase-3 and -6 activities in colorimetric assays. We have shown that caspase-6 or caspase-8 inhibition decreases the neuropathological consequences of cerebral or retinal infarction, thereby emphasizing their importance in ischemic neuronal degeneration. As such, caspase-6 and -8 are potential targets for future therapies aimed at attenuating the devastating functional losses that result from retinal or cerebral stroke.
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9
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Yuan A, Hassinger L, Rao MV, Julien JP, Miller CCJ, Nixon RA. Dissociation of Axonal Neurofilament Content from Its Transport Rate. PLoS One 2015. [PMID: 26208164 PMCID: PMC4514674 DOI: 10.1371/journal.pone.0133848] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The axonal cytoskeleton of neurofilament (NF) is a long-lived network of fibrous elements believed to be a stationary structure maintained by a small pool of transported cytoskeletal precursors. Accordingly, it may be predicted that NF content in axons can vary independently from the transport rate of NF. In the present report, we confirm this prediction by showing that human NFH transgenic mice and transgenic mice expressing human NFL Ser55 (Asp) develop nearly identical abnormal patterns of NF accumulation and distribution in association with opposite changes in NF slow transport rates. We also show that the rate of NF transport in wild-type mice remains constant along a length of the optic axon where NF content varies 3-fold. Moreover, knockout mice lacking NFH develop even more extreme (6-fold) proximal to distal variation in NF number, which is associated with a normal wild-type rate of NF transport. The independence of regional NF content and NF transport is consistent with previous evidence suggesting that the rate of incorporation of transported NF precursors into a metabolically stable stationary cytoskeletal network is the major determinant of axonal NF content, enabling the generation of the striking local variations in NF number seen along axons.
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Affiliation(s)
- Aidong Yuan
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, New York, United States of America
- Department of Psychiatry, New York University School of Medicine, New York, New York, United States of America
- * E-mail: (AY); (RAN)
| | - Linda Hassinger
- Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, Massachusetts, United States of America
| | - Mala V. Rao
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, New York, United States of America
- Department of Psychiatry, New York University School of Medicine, New York, New York, United States of America
| | - Jean-Pierre Julien
- Centre de Recherche du Centre Hospitalier de l'Université Laval, Département d'anatomie et physiologie de l'Université Laval, Québec, Canada
| | - Christopher C. J. Miller
- Department of Neuroscience, Institute of Psychiatry, Kings College London, London, United Kingdom
- Clinical Neurosciences, Institute of Psychiatry, Kings College London, London, United Kingdom
| | - Ralph A. Nixon
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, New York, United States of America
- Department of Psychiatry, New York University School of Medicine, New York, New York, United States of America
- Department of Cell Biology, New York University School of Medicine, New York, New York, United States of America
- * E-mail: (AY); (RAN)
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10
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FitzGibbon T, Nestorovski Z. Human intraretinal myelination: axon diameters and axon/myelin thickness ratios. Indian J Ophthalmol 2014; 61:567-75. [PMID: 24212308 PMCID: PMC3853453 DOI: 10.4103/0301-4738.121075] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Purpose: Human intraretinal myelination of ganglion cell axons occurs in about 1% of the population. We examined myelin thickness and axon diameter in human retinal specimens containing myelinated retinal ganglion cell axons. Materials and Methods: Two eyes containing myelinated patches were prepared for electron microscopy. Two areas were examined in one retina and five in the second retina. Measurements were compared to normal retinal and optic nerve samples and the rabbit retina, which normally contains myelinated axons. Measurements were made using a graphics tablet. Results: Mean axon diameter of myelinated axons at all locations were significantly larger than unmyelinated axons (P ≤ 0.01). Myelinated axons within the patches were significantly larger than axons within the optic nerve (P < 0.01). The relationship between axon diameter/fiber diameter (the G-ratio) seen in the retinal sites differed from that in the nerve. G-ratios were higher and myelin thickness was positively correlated to axon diameter (P < 0.01) in the retina but negatively correlated to axon diameter in the nerve (P < 0.001). Conclusion: Intraretinally myelinated axons are larger than non-myelinated axons from the same population and suggests that glial cells can induce diameter changes in retinal axons that are not normally myelinated. This effect is more dramatic on intraretinal axons compared with the normal transition zone as axons enter the optic nerve and these changes are abnormal. Whether intraretinal myelin alters axonal conduction velocity or blocks axonal conduction remains to be clarified and these issues may have different clinical outcomes.
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Affiliation(s)
- Thomas FitzGibbon
- Department of Clinical Ophthalmology; School of Medical Sciences and Bosch Institute, Discipline of Anatomy and Histology, University of Sydney, NSW 2006, Australia,
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11
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Guharoy M, Szabo B, Martos SC, Kosol S, Tompa P. Intrinsic Structural Disorder in Cytoskeletal Proteins. Cytoskeleton (Hoboken) 2013; 70:550-71. [DOI: 10.1002/cm.21118] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 05/26/2013] [Accepted: 05/29/2013] [Indexed: 12/11/2022]
Affiliation(s)
- Mainak Guharoy
- VIB Department of Structural Biology; Vrije Universiteit Brussel; Brussels Belgium
| | - Beata Szabo
- Institute of Enzymology; Research Centre for Natural Sciences, Hungarian Academy of Sciences; Budapest Hungary
| | | | - Simone Kosol
- VIB Department of Structural Biology; Vrije Universiteit Brussel; Brussels Belgium
| | - Peter Tompa
- VIB Department of Structural Biology; Vrije Universiteit Brussel; Brussels Belgium
- Institute of Enzymology; Research Centre for Natural Sciences, Hungarian Academy of Sciences; Budapest Hungary
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12
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Miao L, Teng J, Lin J, Liao X, Chen J. 14-3-3 proteins interact with neurofilament protein-L and regulate dynamic assembly of neurofilaments. J Cell Sci 2012; 126:427-36. [PMID: 23230147 DOI: 10.1242/jcs.105817] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Neurofilament protein-L (NF-L) is the core component of neurofilaments. Recent studies indicate that the NF-L mutations reported in human Charcot-Marie-Tooth (CMT) disease lead to the formation of NF-L aggregates and result in axon degeneration of motor and sensory neurons, which are thought to be the cause of CMT disease type 2E. In the present study, we investigated the dynamic regulation of NF-L assembly and the mechanism of aggregate formation of CMT NF-L mutants. We report that 14-3-3 proteins interact with NF-L in a phosphorylation-dependent manner. Investigation of mutations of phospho-serine sites at the head domain of NF-L revealed that several phosphorylation sites, particularly Ser43 and Ser55, were important for 14-3-3 binding. 14-3-3 overexpression resulted in a significant increase in the dynamic exchange rate of NF-L subunits and induced striking disassembly of neurofilaments. CMT NF-L mutants, particularly those with mutations in the Pro8 and Pro22 sites of the NF-L head domain, led to substantially diminished interaction between 14-3-3 and NF-L, which resulted in the formation of NF-L aggregates and the disruption of the neurofilament co-assembly of NF-L and NF-M. However, aggregate formation in CMT NF-L mutants was downregulated by 14-3-3 overexpression. Taken together, these results suggest the important role of 14-3-3 in the dynamic regulation of NF-L assembly, and in the capacity to prevent the formation of NF-L aggregates. Thus, the 14-3-3 proteins are a possible molecular target for CMT disease therapy.
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Affiliation(s)
- Linqing Miao
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering, College of Life Sciences, Peking University, Beijing 100871, China
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13
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Rao MV, Yuan A, Campbell J, Kumar A, Nixon RA. The C-terminal domains of NF-H and NF-M subunits maintain axonal neurofilament content by blocking turnover of the stationary neurofilament network. PLoS One 2012; 7:e44320. [PMID: 23028520 PMCID: PMC3448626 DOI: 10.1371/journal.pone.0044320] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 08/01/2012] [Indexed: 02/03/2023] Open
Abstract
Newly synthesized neurofilaments or protofilaments are incorporated into a highly stable stationary cytoskeleton network as they are transported along axons. Although the heavily phosphorylated carboxyl-terminal tail domains of the heavy and medium neurofilament (NF) subunits have been proposed to contribute to this process and particularly to stability of this structure, their function is still obscure. Here we show in NF-H/M tail deletion [NF-(H/M)(tailΔ)] mice that the deletion of both of these domains selectively lowers NF levels 3-6 fold along optic axons without altering either rates of subunit synthesis or the rate of slow axonal transport of NF. Pulse labeling studies carried out over 90 days revealed a significantly faster rate of disappearance of NF from the stationary NF network of optic axons in NF-(H/M)(tailΔ) mice. Faster NF disappearance was accompanied by elevated levels of NF-L proteolytic fragments in NF-(H/M)(tailΔ) axons. We conclude that NF-H and NF-M C-terminal domains do not normally regulate NF transport rates as previously proposed, but instead increase the proteolytic resistance of NF, thereby stabilizing the stationary neurofilament cytoskeleton along axons.
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Affiliation(s)
- Mala V Rao
- Center for Dementia Research, Nathan Kline Institute, Orangeburg, New York, United States of America.
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14
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Zhang G, Jin L, Selzer ME. Assembly properties of lamprey neurofilament subunits and their expression after spinal cord transection. J Comp Neurol 2012; 519:3657-71. [PMID: 21618230 DOI: 10.1002/cne.22673] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In mammals neurofilaments (NF) are formed by coassembly of three subunits: NFL, NFM, and NFH (light, medium, and heavy). It had been believed that lampreys have only one subunit, NF180. However, a previous study showed that NF180 could not self-assemble but could coassemble with rat NFL, suggesting the existence of additional NF subunits in lamprey. More recently, we cloned three additional NF subunits. These new subunits and NF180 have now been transfected in combinations into SW13cl.2Vim(-) cells, which lack endogenous cytoplasmic intermediate filaments. None of the subunits could self-assemble. No combination of NF subunits could form filaments in the absence of lamprey NFL (L-NFL). Assembly occurred at 28°C, but not at 37°C. L-NFL could form thick NF bundles with NF180 but not with NF132 and NF95, which formed only fine filamentous arrays. To determine which parts of the NF subunits are required for filament or bundle formation, we constructed deletion mutants of NF180 and cotransfected them with L-NFL. As with mammalian NF, only constructs with intact head and core domains could form filaments with L-NFL. However, the full length of NF180 was required to form NF bundles. As with NF180, in situ hybridization indicated that mRNA for L-NFL and NF132 was downregulated in identified reticulospinal neurons by 5 weeks after spinal cord transection, but was reexpressed at 10 weeks selectively in those neurons whose axons have a high probability of regenerating. This is consistent with a possible role of NFs in the mechanism of axon regeneration.
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Affiliation(s)
- Guixin Zhang
- Shriners Hospitals Pediatric Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
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15
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Kim SK, Kim H, Yang YR, Suh PG, Chang JS. Phosphatidylinositol phosphates directly bind to neurofilament light chain (NF-L) for the regulation of NF-L self assembly. Exp Mol Med 2011; 43:153-60. [PMID: 21339697 DOI: 10.3858/emm.2011.43.3.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Phosphatidylinositol phosphates (PtdInsPs) are ubiquitous membrane phospholipids that play diverse roles in cell growth and differentiation. To clarify the regulation mechanism acting on neurofilament light chain (NF-L) self assembly, we examined the effects of various PtdInsPs on this process. We found that PtdInsPs, including PI(4,5)P((2)), directly bind to the positively charged Arg(54) of murine NF-L, and this binding promotes NF-L self assembly in vitro. Mutant NF-L (R53A/R54A) proteins lacking binding affinity to PtdInsPs did not have the same effect, but the mutant NF-L proteins showed greater self assembly than the wild-type in the absence of any PtdInsP. These results collectively suggest that Arg(54) plays a pivotal role in NF-L self assembly by binding with PtdInsPs.
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Affiliation(s)
- Sung-Kuk Kim
- Department of Life Science, College of Natural Science, Daejin University, Kyeonggido, Korea
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16
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Paulussen M, Jacobs S, Van der Gucht E, Hof PR, Arckens L. Cytoarchitecture of the mouse neocortex revealed by the low-molecular-weight neurofilament protein subunit. Brain Struct Funct 2011; 216:183-99. [DOI: 10.1007/s00429-011-0311-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Accepted: 03/13/2011] [Indexed: 12/20/2022]
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17
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Alpha-Internexin: The Fourth Subunit of Neurofilaments in the Mature CNS. ADVANCES IN NEUROBIOLOGY 2011. [DOI: 10.1007/978-1-4419-6787-9_8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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18
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Hirokawa N. From electron microscopy to molecular cell biology, molecular genetics and structural biology: intracellular transport and kinesin superfamily proteins, KIFs: genes, structure, dynamics and functions. Microscopy (Oxf) 2011; 60 Suppl 1:S63-S92. [PMID: 21844601 DOI: 10.1093/jmicro/dfr051] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023] Open
Abstract
Cells transport and sort various proteins and lipids following synthesis as distinct types of membranous organelles and protein complexes to the correct destination at appropriate velocities. This intracellular transport is fundamental for cell morphogenesis, survival and functioning not only in highly polarized neurons but also in all types of cells in general. By developing quick-freeze electron microscopy (EM), new filamentous structures associated with cytoskeletons are uncovered. The characterization of chemical structures and functions of these new filamentous structures led us to discover kinesin superfamily molecular motors, KIFs. In this review, I discuss the identification of these new structures and characterization of their functions using molecular cell biology and molecular genetics. KIFs not only play significant roles by transporting various cargoes along microtubule rails, but also play unexpected fundamental roles on various important physiological processes such as learning and memory, brain wiring, development of central nervous system and peripheral nervous system, activity-dependent neuronal survival, development of early embryo, left-right determination of our body and tumourigenesis. Furthermore, by combining single-molecule biophysics with structural biology such as cryo-electrom microscopy and X-ray crystallography, atomic structures of KIF1A motor protein of almost all states during ATP hydrolysis have been determined and a common mechanism of motility has been proposed. Thus, this type of studies could be a good example of really integrative multidisciplinary life science in the twenty-first century.
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Affiliation(s)
- Nobutaka Hirokawa
- Department of Cell Biology and Anatomy, Graduate School of Medicine, University of Tokyo, Hongo, 7-3-1, Bunkyo-ku, Tokyo, Japan 113-0033.
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19
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Zhulina EB, Leermakers FAM. The polymer brush model of neurofilament projections: effect of protein composition. Biophys J 2010; 98:462-9. [PMID: 20141760 DOI: 10.1016/j.bpj.2009.10.033] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 10/20/2009] [Accepted: 10/21/2009] [Indexed: 01/11/2023] Open
Abstract
Applying self-consistent field theory, we consider a coarse-grained model for the polymerlike projections of neurofilament (NF) proteins that form a brush structure around neurofilaments. We focus on effects of molecular composition, which is the relative occurrence of NF-H, NF-M, and NF-L proteins, on the organization of NF projection domains. We consider NF brushes with selectively truncated projections, and with a varied ratio L:H:M of constituent tails. Our conclusion is that the NF brush structure is remarkably tolerant with respect to the variation in M and H chains. Results compare favorably with experimental data on model animals, provided that due attention is paid on the level of phosphorylation of the KSP repeats.
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Affiliation(s)
- E B Zhulina
- Institute of Macromolecular Compounds of the Russian Academy of Sciences, St. Petersburg, Russia
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20
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Mähönen AJ, Makkonen KE, Laakkonen JP, Ihalainen TO, Kukkonen SP, Kaikkonen MU, Vihinen-Ranta M, Ylä-Herttuala S, Airenne KJ. Culture medium induced vimentin reorganization associates with enhanced baculovirus-mediated gene delivery. J Biotechnol 2009; 145:111-9. [PMID: 19903502 DOI: 10.1016/j.jbiotec.2009.11.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Revised: 09/16/2009] [Accepted: 11/03/2009] [Indexed: 01/04/2023]
Abstract
Baculoviruses can express transgenes under mammalian promoters in a wide range of vertebrate cells. However, the success of transgene expression is dependent on both the appropriate cell type and culture conditions. We studied the mechanism behind the substantial effect of the cell culture medium on efficiency of the baculovirus transduction in different cell lines. We tested six cell culture mediums; the highest transduction efficiency was detected in the presence of RPMI 1640 medium. Vimentin, a major component of type III intermediate filaments, was reorganized in the optimized medium, which associated with enhanced nuclear entry of baculoviruses. Accordingly, the phosphorylation pattern of vimentin was changed in the studied cell lines. These results suggest that vimentin has an important role in baculovirus entry into vertebrate cells. Enhanced gene delivery in the optimized medium was observed also with adenoviruses and lentiviruses. The results highlight the general importance of the culture medium in the assembly of the cytoskeleton network and in viral gene delivery.
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Affiliation(s)
- Anssi J Mähönen
- A.I. Virtanen Institute, Department of Biotechnology and Molecular Medicine, University of Kuopio Kuopio, Finland.
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21
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Lee IB, Kim SK, Chung SH, Kim H, Kwon TK, Min DS, Chang JS. The effect of rod domain A148V mutation of neurofilament light chain on filament formation. BMB Rep 2009; 41:868-74. [PMID: 19123978 DOI: 10.5483/bmbrep.2008.41.12.868] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neurofilaments (NFs) are neuronal intermediate filaments composed of light (NF-L), middle (NF-M), and heavy (NF-H) subunits. NF-L self-assembles into a "core" filament with which NF-M or NF-H co-assembles to form the neuronal intermediate filament. Recent reports show that point mutations of the NF-L gene result in Charcot-Marie-Tooth disease (CMT). However, the most recently described rod domain mutant of human NF-L (A148V) has not been characterized in cellular level. We cloned human NF-L and used it to engineer the A148V. In phenotypic analysis using SW13 cells, A148V mutation completely abolished filament formation despite of presence of NF-M. Moreover, A148V mutation reduced the levels of in vitro self-assembly using GST-NF-L (H/R) fusion protein whereas control (A296T) mutant did not affect the filament formation. These results suggest that alanine at position 148 is essentially required for NF-L self-assembly leading to subsequent filament formation in neuronal cells.
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Affiliation(s)
- In-Bum Lee
- Department of Life Science, College of Natural Science, Daejin University, Pocheon, Korea
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22
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Phosphorylation of highly conserved neurofilament medium KSP repeats is not required for myelin-dependent radial axonal growth. J Neurosci 2009; 29:1277-84. [PMID: 19193875 DOI: 10.1523/jneurosci.3765-08.2009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurofilament medium (NF-M) is essential for the acquisition of normal axonal caliber in response to a myelin-dependent "outside-in" trigger for radial axonal growth. Removal of the tail domain and lysine-serine-proline (KSP) repeats of NF-M, but not neurofilament heavy, produced axons with impaired radial growth and reduced conduction velocities. These earlier findings supported myelin-dependent phosphorylation of NF-M KSP repeats as an essential component of axonal growth. As a direct test of whether phosphorylation of NF-M KSP repeats is the target for the myelin-derived signal, gene replacement has now been used to produce mice in which all serines of NF-M's KSP repeats have been replaced with phosphorylation-incompetent alanines. This substitution did not alter accumulation of the neurofilaments or their subunits. Axonal caliber and motor neuron conduction velocity of mice expressing KSP phospho-incompetent NF-M were also indistinguishable from wild-type mice. Thus, phosphorylation of NF-M KSP repeats is not an essential component for the acquisition of normal axonal caliber mediated by myelin-dependent outside-in signaling.
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23
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Lee S, Chu B, Yao J, Shea TB, Hall GF. The glutamate-rich region of the larger lamprey neurofilament sidearm is essential for proper neurofilament architecture. Brain Res 2008; 1231:1-5. [DOI: 10.1016/j.brainres.2008.07.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 06/20/2008] [Accepted: 07/04/2008] [Indexed: 11/26/2022]
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24
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Tong X, Zhai Z, Chen J. Coil-1 of rod domain of NF-L is essential for its assemblyin vivo. SCIENCE IN CHINA. SERIES C, LIFE SCIENCES 2008; 42:449-56. [PMID: 18726507 DOI: 10.1007/bf02881767] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/1998] [Indexed: 11/28/2022]
Abstract
Neurofilaments take highly ordered structures composed of parallel mays of 10 nm filaments linked to each other with frequent cross-bridge. It is composed of three components named NF-L, NF-M and NF-H. NF-L is able to form filamentous network alone in Sf9 cells, while M could not. To identify which domain is essential for the assembly of NF-L, two chimera proteins named ML and MML were constructed: ML was composed of the head domain of NF-M and other domains of NF-L; MML was composed of the head and Coil-1 domains of NF-M and Coil-2 and tail domains of NF-L. ML was not only able to form filaments in Sf9 cells, but also co-assemble with NF-M into parallel filamentous bundles. MML could not assemble into filaments. Thus the Coil-1 domain of NF-L was essential for its assembly.
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Affiliation(s)
- X Tong
- College of Life Sciences, Peking University, 100871, Beijing, China
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25
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Perkins GA, Sosinsky GE, Ghassemzadeh S, Perez A, Jones Y, Ellisman MH. Electron tomographic analysis of cytoskeletal cross-bridges in the paranodal region of the node of Ranvier in peripheral nerves. J Struct Biol 2007; 161:469-80. [PMID: 18096402 DOI: 10.1016/j.jsb.2007.10.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 10/05/2007] [Accepted: 10/08/2007] [Indexed: 11/25/2022]
Abstract
The node of Ranvier is a site for ionic conductances along myelinated nerves and governs the saltatory transmission of action potentials. Defects in the cross-bridging and spacing of the cytoskeleton are a prominent pathological feature in diseases of the peripheral nerve. Electron tomography was used to examine cytoskeletal-cytoskeletal, membrane-cytoskeletal, and heterologous cell connections in the paranodal region of the node of Ranvier in peripheral nerves. Focal attachment of cytoskeletal filaments to each other and to the axolemma and paranodal membranes of the Schwann cell via narrow cross-bridges was visualized in both neuronal and glial cytoplasm. A subset of intermediate filaments associates with the cytoplasmic surfaces of supramolecular complexes of transmembrane structures that are presumed to include known and unknown junctional proteins. Mitochondria were linked to both microtubules and neurofilaments in the axoplasm and to neighboring smooth endoplasmic reticulum by narrow cross-bridges. Tubular cisternae in the glial cytoplasm were also linked to the paranodal glial cytoplasmic loop juxtanodal membrane by short cross-bridges. In the extracellular matrix between axon and Schwann cell, junctional bridges formed long cylinders linking the two membranes. Interactions between cytoskeleton, membranes, and extracellular matrix associations in the paranodal region are likely critical not only for scaffolding, but also for intracellular and extracellular communication.
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Affiliation(s)
- Guy A Perkins
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California, San Diego, 9500 Gilman Drive, La jolla, CA 92093-0608, USA.
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26
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Kim SK, Cho SM, Lee IB, Lee YH, Kang JH, Choi JH, Suh PG, Chang JS. In vitro assay of neurofilament light chain self-assembly using truncated mutants. J Neurosci Methods 2007; 161:199-204. [PMID: 17157386 DOI: 10.1016/j.jneumeth.2006.10.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Revised: 10/27/2006] [Accepted: 10/31/2006] [Indexed: 10/23/2022]
Abstract
Neurofilaments (NFs) are heteropolymers composed of light (NF-L), middle (NF-M), and heavy (NF-H) subunits, present in most neurons. NF-L polymerizes on its own to provide a scaffold on which regular NFs form via the cross-bridging of NF-M or NF-H. To clarify the mechanism of regulation of NF-L self-assembly, we developed an assay using truncated mutant NF-L fused to glutathione-S transferase (GST). Western immunoblotting data show that the GST-fused head-rod domains of NF-L are necessary and sufficient for detecting assembled NF-L. The levels of self-assembled NF-L subunits detected using GST fusion proteins were consistent with those detected by electron microscopy and turbidity assay. Our results collectively imply that GST-fused head-rod domains of NF-L are critical tools for analyzing NF-L self-assembly in vitro.
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Affiliation(s)
- Sung-Kuk Kim
- Department of Life Science, College of Natural Science, Daejin University, Kyeonggido 487-711, Republic of Korea
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27
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Abstract
Peripheral neuropathy is a common disorder seen in general neurology and neuromuscular specialty clinics. Treatment options directed at the underlying cause can only be offered in a handful of conditions, such as those with possible autoimmune etiology. The remainder fall into the idiopathic or genetic category with no known treatment. This review surveys the evidence supporting the rationale for the therapeutic use of neurotrophins and other neurotrophic factors in these disorders in relationship to the underlying pathobiological process. Previous clinical trials are assessed, and increasingly better understood and appreciated therapeutic potential of neurotrophins is emphasized.
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Affiliation(s)
- Zarife Sahenk
- Neuromuscular Pathology, The Ohio State University, Columbus Children's Research Institute, Neuromuscular Program, Columbus, Ohio 43205, USA.
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28
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Xiao S, McLean J, Robertson J. Neuronal intermediate filaments and ALS: a new look at an old question. Biochim Biophys Acta Mol Basis Dis 2006; 1762:1001-12. [PMID: 17045786 DOI: 10.1016/j.bbadis.2006.09.003] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 08/31/2006] [Accepted: 09/05/2006] [Indexed: 01/15/2023]
Abstract
One of the pathological hallmarks of ALS is the presence of axonal spheroids and perikaryal accumulations/aggregations comprised of the neuronal intermediate filament proteins, neurofilaments and peripherin. These abnormalities represent a point of convergence of both familial and sporadic forms of the disease and understanding their formation may reveal shared pathways in what is otherwise considered a highly heterogeneous disorder. Here we provide a review of the basic biology of neurofilaments and peripherin and the evidence linking them with ALS disease pathogenesis.
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Affiliation(s)
- Shangxi Xiao
- Department of Laboratory Medicine and Pathobiology, Centre for Research in Neurodegenerative Diseases, University of Toronto, Tanz Neuroscience Building, 6, Queen's Park Crescent West, Toronto, ON, Canada M5S 3H2
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29
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Yuan A, Nixon RA, Rao MV. Deleting the phosphorylated tail domain of the neurofilament heavy subunit does not alter neurofilament transport rate in vivo. Neurosci Lett 2005; 393:264-8. [PMID: 16266786 DOI: 10.1016/j.neulet.2005.10.029] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Revised: 09/07/2005] [Accepted: 10/01/2005] [Indexed: 11/25/2022]
Abstract
Phosphorylation of the carboxyl tail domains of the neurofilament heavy (NF-H) and middle molecular weight (NF-M) subunits has been proposed to regulate the axonal transport of neurofilaments. To test this hypothesis, we recently constructed mice lacking the extensively phosphorylated NF-H tail domain (NF-HtailDelta) and showed that the transport rate of neurofilaments in optic axons is unaltered in the absence of this domain [M.V. Rao, M.L. Garcia, Y. Miyazaki, T. Gotow, A. Yuan, S. Mattina, C.M. Ward, N.A. Calcutt, Y. Uchiyama, R.A. Nixon, D.W. Cleveland, Gene replacement in mice reveals that the heavily phosphorylated tail of neurofilament heavy subunit does not affect axonal caliber or the transit of cargoes in slow axonal transport, J. Cell Biol. 158 (2002) 681-693]. However, Shea et al. proposed that deletion of NF-H carboxyl-terminal region accelerates the transport of a subpopulation of neurofilaments based on minor differences between tail-deleted and control mice in our axonal transport analysis. Here, we present additional evidence that neurofilament transport rate is unchanged after deleting the phosphorylated NF-H tail domain, establishing unequivocally that the NF-H tail domain alone does not regulate the rate of neurofilament transport in optic axons in vivo. Possible roles for tail domains as cross-bridges between a neurofilament and its neighbors or other cytoskeletal elements is discussed.
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Affiliation(s)
- Aidong Yuan
- Center for Dementia Research, Nathan Kline Institute, New York University School of Medicine, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA
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30
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Jung C, Lee S, Ortiz D, Zhu Q, Julien JP, Shea TB. The high and middle molecular weight neurofilament subunits regulate the association of neurofilaments with kinesin: inhibition by phosphorylation of the high molecular weight subunit. ACTA ACUST UNITED AC 2005; 141:151-5. [PMID: 16246456 DOI: 10.1016/j.molbrainres.2005.08.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2004] [Revised: 07/11/2005] [Accepted: 08/15/2005] [Indexed: 11/21/2022]
Abstract
Kinesin participates in axonal transport of neurofilaments (NFs), but the mode by which they attach to kinesin is unclear. We compared the association of NFs with kinesin in mice expressing or lacking NF-H or NF-M. In normal and M-/- mice, the leading edge of metabolically labeled NF subunits was selectively co-precipitated with kinesin. By contrast, the entire wave of radiolabeled subunits co-precipitated with kinesin in H-/- mice. Similar bulk levels of NFs co-precipitated with kinesin from normal and H-/- mice, but reduced levels co-precipitated from M-/- mice. These data suggest that both NF-H and NF-M regulate the association of NFs with kinesin. They further indicate that phosphorylation of NF-H dissociates NFs from kinesin and provides a mechanism by which NF-H phosphorylation can contribute to the slowing of NF axonal transport.
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Affiliation(s)
- Cheolwha Jung
- Center for Cellular Neurobiology and Neurodegeneration Research, Department of Biological Sciences, University of Massachusetts, Lowell, One University Avenue, Lowell, MA 01854, USA
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31
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LoPachin RM, He D, Reid ML. 2,5-Hexanedione-induced changes in the neurofilament subunit pools of rat peripheral nerve. Neurotoxicology 2005; 26:229-40. [PMID: 15713344 DOI: 10.1016/j.neuro.2004.09.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Accepted: 09/29/2004] [Indexed: 11/27/2022]
Abstract
Axon atrophy is the principle morphological feature of the peripheral neuropathy induced by 2,5-hexanedione (HD). Axon caliber is determined by a stationary neurofilamentous cytoskeleton that is maintained through dynamic interactions with mobile neurofilament (NF) subunits. To determine the effects of HD on the stationary and mobile NF pools, groups of rats were exposed to HD at dosing schedules (175 mg/kg x 101 days or 400 mg/kg x 26 days) that produced moderate levels of neurological deficits and, as assessed by previous studies, prevalent axon atrophy in peripheral nerve. Sciatic and tibial nerves from HD-intoxicated rats and their age-matched controls were triton-extracted and separated by differential centrifugation into a high-speed pellet (P1) of NF polymer and a corresponding supernatant fraction (S1), which presumably contained mobile monomer. Cytoskeletal proteins (NF-L, NF-M, NF-H and beta-tubulin) in each fraction were determined by immunoblot analysis. Results show that regardless of HD dose-rate, triton-soluble NF subunits in the supernatant fractions were significantly reduced, whereas triton-insoluble proteins in the corresponding pellets were inconsistently affected. Beta-tubulin also exhibited inconsistent fractional changes, while abnormal higher molecular weight NF proteins were detected primarily in the triton-insoluble fraction. Studies with antibodies directed against phosphorylated (RT97) and non-phosphorylated (SMI32) epitopes on NF-H did not reveal major changes in subunit phosphorylation. These results suggest that HD intoxication is primarily associated with depletion of soluble NF proteins, which could produce axon atrophy through disruption of cytoskeletal turnover and maintenance.
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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. 210th St., Bronx, NY 10467, USA.
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32
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Kumar S, Hoh JH. Modulation of repulsive forces between neurofilaments by sidearm phosphorylation. Biochem Biophys Res Commun 2004; 324:489-96. [PMID: 15474454 DOI: 10.1016/j.bbrc.2004.09.076] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2004] [Indexed: 10/26/2022]
Abstract
Recent studies have advanced the notion that the axonal organization of neurofilaments (NFs) is based on mutual steric repulsion between the unstructured "sidearm" domains of adjacent NFs. Here, we present experimental evidence that these repulsive forces are modulated by the degree of sidearm phosphorylation. When NFs are sedimented into a gelatinous pellet, pellet volume falls with increasing ionic strength and enzymatic dephosphorylation; sedimentation of phosphorylated NFs in the presence of divalent cations also dramatically reduces pellet volume. Further, atomic force microscopy imaging of isolated mammalian NFs reveals robust exclusion of colloidal particles from the NF backbone that is reduced at high ionic strength and attenuated when the filaments are enzymatically dephosphorylated. Phosphate-phosphate repulsion on the NF sidearm appears to modulate NF excluded volume in a graded fashion, thereby controlling axonal NF organization through interfilament forces.
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Affiliation(s)
- Sanjay Kumar
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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33
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Dubey M, Hoda S, Chan WKH, Pimenta A, Ortiz DD, Shea TB. Reexpression of vimentin in differentiated neuroblastoma cells enhances elongation of axonal neurites. J Neurosci Res 2004; 78:245-9. [PMID: 15378517 DOI: 10.1002/jnr.20146] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Vimentin (Vm) is initially expressed by early neuronal precursors in situ and in culture. Vm is essential for neuritogenesis at least in culture and is gradually replaced by neurofilaments (NFs) because of down-regulation of Vm expression. This period is accompanied by a slowing of axonal elongation. We examined whether continued expression of Vm could foster continued axonal elongation. NB2a/d1 cells differentiated with dibutyryl cAMP were transfected with constructs expressing Vm or the middle-molecular-weight NF subunit (NF-M) each conjugated to green fluorescent protein (GFP). Axonal neurites of cells expressing GFP-Vm were 30% longer than those of nonexpressing cells, or cells expressing GFP-M, and exhibited a decrease in neurite caliber. Expression of GFP-M did not enhance axonal neurite length but significantly increased caliber. These findings provide further evidence of a role for Vm in axonal outgrowth. Culturing of nontransfected cells on laminin increased neurite length, but cells expressing GFP-Vm demonstrated an equivalent increase whether cultured on laminin or culture plastic. Axonal neurites of cells expressing GFP-Vm turned to avoid a nonfavorable substrate (nitrocellulose), but culturing of these cells on nitrocellulose did not impair axonal outgrowth. These latter findings indicate that the more robust outgrowth following reexpression of Vm is independent of a favorable or nonfavorable substrate but that axonal neurites of these cells still interact with the substrate to the extent that the substrate can influence directionality.
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Affiliation(s)
- Maya Dubey
- Center for Cellular Neurobiology and Neurodegeneration Research, Department of Biological Sciences, University of Massachusetts Lowell, Lowell, Massachusetts 01854, USA
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34
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Milenkovic I, Filipovic R, Nedeljkovic N, Pekovic S, Culic M, Rakic L, Stojiljkovic M. Spatio-temporal changes in neurofilament proteins immunoreactivity following kainate-induced cerebellar lesion in rats. Cell Mol Neurobiol 2004; 24:367-78. [PMID: 15206820 DOI: 10.1023/b:cemn.0000022769.44211.2b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
1. Spatio-temporal changes in phosphorylated (pNFP) and nonphosphorylated (npNFP) neurofilament proteins were assessed immunocytochemicaly in adult rat cerebellum, 2-30 days following unilateral injection of kainic acid (KA) or physiological saline (s.c.). 2. Analysis of the staining intensity and pattern demonstrated that injection of both KA and physiological saline elicited significant and long-lasting increase of pNFP and npNFP immunoreactivity, at the ipsilateral, and to lesser extent at the contralateral side of lesion. 3. Kainate intoxication induced abundant expression of pNFP and npNFP in cerebellar white matter, as well as in all layers of perilesioned cortex. Higher pNFP expression was evidenced in the Purkinje cell layer, particularly at cell bodies, initial segments, and proximal dendrites, which normally do not contain pNFP. In addition, synaptophysin immunocytochemistry was used as a marker of synaptogenesis and plasticity. 4. Spatio-temporal pattern of NFP and synaptophysin expression suggests that perilesioned cortex undergoes dynamic changes following brain demage and possess a reparative capacity to abridge the consequences of brain trauma.
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Affiliation(s)
- I Milenkovic
- Department of Neurobiology and Neurochemistry, Institute of Biological Research Sinisa Stanković, Belgrade, Serbia and Montenegro
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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. [PMID: 15207649 DOI: 10.1016/j.taap.2004.03.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2003] [Accepted: 03/01/2004] [Indexed: 11/20/2022]
Abstract
Quantitative morphometric analyses have demonstrated that axon atrophy is the primary neuropathic feature in the CNS and PNS of rats intoxicated with 2,5-hexanedione (HD). Axon caliber is maintained by the exchange of mobile neurofilament (NF) subunits with the stationary polymer and, therefore, HD might produce atrophy by disrupting cytoskeletal turnover. To evaluate this possibility, groups of rats were exposed to HD at dosing schedules (175 mg/kg x 101 days or 400 mg/kg x 26 days) that produced moderate levels of neurological deficits and prevalent axon atrophy in spinal cord white matter tracts. Lumbar spinal cord regions from HD-intoxicated rats and their age-matched controls were Triton-extracted and separated by differential fractionation into a low-speed, insoluble pellet (P1) of NF polymer and a high-speed supernatant fraction (S2), which presumably contained mobile monomer. Cytoskeletal protein contents (NF-L, -M, -H, and beta-tubulin) in each fraction were determined by immunoblot analysis. Results show that regardless of HD dose-rate, the NF polymer in P1 remained unaffected, although soluble monomer in the S2 fraction was depleted significantly (60-80% reduction). Fractional beta-tubulin contents were inconsistently affected and abnormal higher-molecular-weight NF proteins were detected in the P1 fraction only. Studies with antibodies directed against phosphorylated (RT97) and nonphosphorylated (SMI32) epitopes on NF-H and measurements of corresponding isoelectric range suggested that alterations in phosphorylation were not involved. The selective depletion of Triton-soluble protein suggested that HD adduction of NFs interfered with the dynamic interactions of the polymeric and mobile monomeric pools.
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Affiliation(s)
- Richard M LoPachin
- Department of Anesthesiology, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY 10467, USA.
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36
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LoPachin RM, DeCaprio AP. γ-Diketone neuropathy: axon atrophy and the role of cytoskeletal protein adduction. Toxicol Appl Pharmacol 2004; 199:20-34. [PMID: 15289087 DOI: 10.1016/j.taap.2004.03.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2003] [Accepted: 03/09/2004] [Indexed: 10/26/2022]
Abstract
Multifocal giant neurofilamentous axonal swellings and secondary distal degeneration have been historically considered the hallmark features of gamma-diketone neuropathy. Accordingly, research conducted over the past 25 years has been directed toward discerning mechanisms of axonal swelling. However, this neuropathological convention has been challenged by recent observations that swollen axons were an exclusive product of long-term 2.5-hexanedione (HD) intoxication at lower daily dose-rates (e.g., 175 mg/kg/day); that is, higher HD dose-rates (e.g., 400 mg/kg/day) produced neurological deficits in the absence of axonal swellings. The observation that neurological toxicity can be expressed without axonal swelling suggests that this lesion is not an important pathophysiological event. Instead, several research groups have now shown that axon atrophy is prevalent in nervous tissues of laboratory animals intoxicated over a wide range of HD dose-rates. The well-documented nerve conduction defects associated with axon atrophy, in conjunction with the temporal correspondence between this lesion and the onset of neurological deficits, strongly suggest that atrophy has pathophysiological significance. In this commentary, we present evidence that supports a pathognomonic role for axon atrophy in gamma-diketone neuropathy and suggests that the functional consequences of this lesion mediate the corresponding neurological toxicity. Previous research has demonstrated that HD interacts with proteins via formation of pyrrole adducts. We therefore discuss the possibility that this chemical process is essential to the mechanism of atrophy. Evidence presented in this review suggests that "distal axonopathy" is an inaccurate classification and future nosological schemes should be based on the apparent primacy of axon atrophy.
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Affiliation(s)
- Richard M LoPachin
- Department of Anesthesiology, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY 10467-2490, USA.
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37
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Helfand BT, Chang L, Goldman RD. Intermediate filaments are dynamic and motile elements of cellular architecture. J Cell Sci 2004; 117:133-41. [PMID: 14676269 DOI: 10.1242/jcs.00936] [Citation(s) in RCA: 196] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Recent evidence showing that intermediate filaments (IFs) are dynamic, motile elements of the cytoskeletal repertoire of vertebrate cells has overturned the long-standing view that they simply form static 'space filling' cytoplasmic networks. In fact, many types of IF are now known to engage in a remarkable array of movements that are closely associated with their assembly, disassembly and subcellular organization. Some of these motile properties are intrinsic to IFs and others are attributable to molecular crosstalk with either microtubules or actin-containing microfilaments. This crosstalk is, to a large extent, mediated by molecular motors, including conventional kinesin and cytoplasmic dynein. These motors are responsible for the high-speed delivery of nonfilamentous IF precursors and short filaments to specific regions of the cytoplasm, where they assemble into long IFs. Interestingly, the patterns and speeds of IF movements vary in different cell types and even within different regions of the same cell. These differences in motility may be related to their interactions with different types of molecular motor and/or other factors, such as IF-associated proteins.
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Affiliation(s)
- Brian T Helfand
- Feinberg School of Medicine, Northwestern University, Department of Cell and Molecular Biology, 303 E. Chicago Avenue, Chicago, IL 60611, USA
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Garcia ML, Lobsiger CS, Shah SB, Deerinck TJ, Crum J, Young D, Ward CM, Crawford TO, Gotow T, Uchiyama Y, Ellisman MH, Calcutt NA, Cleveland DW. NF-M is an essential target for the myelin-directed "outside-in" signaling cascade that mediates radial axonal growth. ACTA ACUST UNITED AC 2004; 163:1011-20. [PMID: 14662745 PMCID: PMC2173620 DOI: 10.1083/jcb.200308159] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Neurofilaments are essential for acquisition of normal axonal calibers. Several lines of evidence have suggested that neurofilament-dependent structuring of axoplasm arises through an “outside-in” signaling cascade originating from myelinating cells. Implicated as targets in this cascade are the highly phosphorylated KSP domains of neurofilament subunits NF-H and NF-M. These are nearly stoichiometrically phosphorylated in myelinated internodes where radial axonal growth takes place, but not in the smaller, unmyelinated nodes. Gene replacement has now been used to produce mice expressing normal levels of the three neurofilament subunits, but which are deleted in the known phosphorylation sites within either NF-M or within both NF-M and NF-H. This has revealed that the tail domain of NF-M, with seven KSP motifs, is an essential target for the myelination-dependent outside-in signaling cascade that determines axonal caliber and conduction velocity of motor axons.
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Affiliation(s)
- Michael L Garcia
- Ludwig Institute for Cancer Research, Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093, USA
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39
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Krüger R, Fischer C, Schulte T, Strauss KM, Müller T, Woitalla D, Berg D, Hungs M, Gobbele R, Berger K, Epplen JT, Riess O, Schöls L. Mutation analysis of the neurofilament M gene in Parkinson's disease. Neurosci Lett 2004; 351:125-9. [PMID: 14583397 DOI: 10.1016/s0304-3940(03)00903-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Neurofilament M, a major component of Lewy bodies, represents an interesting candidate in the pathogenesis of Parkinson's disease (PD). We performed detailed mutation analyses of the NF-M gene in 322 familial and sporadic PD patients. Two polymorphisms (Ala475Thr and Gly697Arg) occurred at similar frequencies in PD patients and controls. A Pro725Gln substitution and a deletion of valine in position 829 were identified in two PD patients. These substitutions affect residues of the NF-M protein that are highly conserved among different species. None of our patients carried the Gly336Ser substitution, which has been described in familial PD. Our results argue against a major role of NF-M in PD. However, rare variants of the NF-M gene may act as susceptibility factors for PD and functional analyses of the identified variations are warranted to decipher possible mechanisms in neurodegeneration.
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Affiliation(s)
- Rejko Krüger
- Department of Neurology, Neurodegeneration Laboratory, University of Tübingen, Hoppe-Seyler-Strasse 3, D-72076, Tübingen, Germany.
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40
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Rao MV, Campbell J, Yuan A, Kumar A, Gotow T, Uchiyama Y, Nixon RA. The neurofilament middle molecular mass subunit carboxyl-terminal tail domains is essential for the radial growth and cytoskeletal architecture of axons but not for regulating neurofilament transport rate. J Cell Biol 2003; 163:1021-31. [PMID: 14662746 PMCID: PMC2173612 DOI: 10.1083/jcb.200308076] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2003] [Accepted: 10/17/2003] [Indexed: 11/26/2022] Open
Abstract
The phosphorylated carboxyl-terminal "tail" domains of the neurofilament (NF) subunits, NF heavy (NF-H) and NF medium (NF-M) subunits, have been proposed to regulate axon radial growth, neurofilament spacing, and neurofilament transport rate, but direct in vivo evidence is lacking. Because deletion of the tail domain of NF-H did not alter these axonal properties (Rao, M.V., M.L. Garcia, Y. Miyazaki, T. Gotow, A. Yuan, S. Mattina, C.M. Ward, N.S. Calcutt, Y. Uchiyama, R.A. Nixon, and D.W. Cleveland. 2002. J. Cell Biol. 158:681-693), we investigated possible functions of the NF-M tail domain by constructing NF-M tail-deleted (NF-MtailDelta) mutant mice using an embryonic stem cell-mediated "gene knockin" approach that preserves normal ratios of the three neurofilament subunits. Mutant NF-MtailDelta mice exhibited severely inhibited radial growth of both motor and sensory axons. Caliber reduction was accompanied by reduced spacing between neurofilaments and loss of long cross-bridges with no change in neurofilament protein content. These observations define distinctive functions of the NF-M tail in regulating axon caliber by modulating the organization of the neurofilament network within axons. Surprisingly, the average rate of axonal transport of neurofilaments was unaltered despite these substantial effects on axon morphology. These results demonstrate that NF-M tail-mediated interactions of neurofilaments, independent of NF transport rate, are critical determinants of the size and cytoskeletal architecture of axons, and are mediated, in part, by the highly phosphorylated tail domain of NF-M.
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Affiliation(s)
- Mala V Rao
- Nathan Kline Institute, NYU School of Medicine, 140 Old Orangeburg Rd., Orangeburg, NY 10962, USA.
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41
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Abstract
Neurofilament assembly requires at minimum the polymerization of neurofilament light chain (NF-L) with either neurofilament medium chain (NF-M) or neurofilament heavy chain (NF-H) subunits, but requirements for their axonal transport have long been controversial. Using a gene deletion approach, we generated mice containing only NF-L or NF-M. In vivo pulse radiolabeling analyses in retinal ganglion cell neurons revealed that NF-L alone is incapable of efficient transport, whereas nearly one-half of the normal level of NF-M is transported along optic axons in the absence of the other triplet subunits. Under these conditions, however, NF-M transport is completely abolished by deleting alpha-internexin. Our results strongly suggest that efficient neurofilament protein transport in vivo minimally requires hetero-oligomer formation. They also show that NF-M can partner with intermediate filament proteins other than the NF-H and NF-L subunits in neurons to support slow transport and possibly other functions of neuronal intermediate filaments.
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42
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Helfand BT, Mendez MG, Pugh J, Delsert C, Goldman RD. A role for intermediate filaments in determining and maintaining the shape of nerve cells. Mol Biol Cell 2003; 14:5069-81. [PMID: 14595112 PMCID: PMC284808 DOI: 10.1091/mbc.e03-06-0376] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
To date, the functions of most neural intermediate filament (IF) proteins have remained elusive. Peripherin is a type III intermediate filament (IF) protein that is expressed in developing and in differentiated neurons of the peripheral and enteric nervous systems. It is also the major IF protein expressed in PC12 cells, a widely used model for studies of peripheral neurons. Dramatic increases in peripherin expression have been shown to coincide with the initiation and outgrowth of axons during development and regeneration, suggesting that peripherin plays an important role in axon formation. Recently, small interfering RNAs (siRNA) have provided efficient ways to deplete specific proteins within mammalian cells. In this study, it has been found that peripherin-siRNA depletes peripherin and inhibits the initiation, extension, and maintenance of neurites in PC12 cells. Furthermore, the results of these experiments demonstrate that peripherin IF are critical determinants of the overall shape and architecture of neurons.
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Affiliation(s)
- Brian T Helfand
- Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA
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43
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Yuan A, Rao MV, Kumar A, Julien JP, Nixon RA. Neurofilament transport in vivo minimally requires hetero-oligomer formation. J Neurosci 2003; 23:9452-8. [PMID: 14561875 PMCID: PMC6740570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023] Open
Abstract
Neurofilament assembly requires at minimum the polymerization of neurofilament light chain (NF-L) with either neurofilament medium chain (NF-M) or neurofilament heavy chain (NF-H) subunits, but requirements for their axonal transport have long been controversial. Using a gene deletion approach, we generated mice containing only NF-L or NF-M. In vivo pulse radiolabeling analyses in retinal ganglion cell neurons revealed that NF-L alone is incapable of efficient transport, whereas nearly one-half of the normal level of NF-M is transported along optic axons in the absence of the other triplet subunits. Under these conditions, however, NF-M transport is completely abolished by deleting alpha-internexin. Our results strongly suggest that efficient neurofilament protein transport in vivo minimally requires hetero-oligomer formation. They also show that NF-M can partner with intermediate filament proteins other than the NF-H and NF-L subunits in neurons to support slow transport and possibly other functions of neuronal intermediate filaments.
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Affiliation(s)
- Aidong Yuan
- Center for Dementia Research, Nathan Kline Institute, New York University School of Medicine, Orangeburg, New York 10962, USA.
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44
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Zheng YL, Li BS, Pant HC. Phosphorylation of the head domain of neurofilament protein (NF-M): a factor regulating topographic phosphorylation of NF-M tail domain KSP sites in neurons. J Biol Chem 2003; 278:24026-32. [PMID: 12695506 DOI: 10.1074/jbc.m303079200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In neurons the phosphorylation of neurofilament (NF) proteins NF-M and NF-H is topographically regulated. Although kinases and NF subunits are synthesized in cell bodies, extensive phosphorylation of the KSP repeats in tail domains of NF-M and NF-H occurs primarily in axons. The nature of this regulation, however, is not understood. As obligate heteropolymers, NF assembly requires interactions between the core NF-L with NF-M or NF-H subunits, a process inhibited by NF head domain phosphorylation. Phosphorylation of head domains at protein kinase A (PKA)-specific sites seems to occur transiently in cell bodies after NF subunit synthesis. We have proposed that transient phosphorylation of head domains prevents NF assembly in the soma and inhibits tail domain phosphorylation; i.e. assembly and KSP phosphorylation in axons depends on prior dephosphorylation of head domain sites. Deregulation of this process leads to pathological accumulations of phosphorylated NFs in the soma as seen in some neurodegenerative disorders. To test this hypothesis, we studied the effect of PKA phosphorylation of the NF-M head domain on phosphorylation of tail domain KSP sites. In rat cortical neurons we showed that head domain phosphorylation of endogenous NF-M by forskolin-activated PKA inhibits NF-M tail domain phosphorylation. To demonstrate the site specificity of PKA phosphorylation and its effect on tail domain phosphorylation, we transfected NIH3T3 cells with NF-M mutated at PKA-specific head domain serine residues. Epidermal growth factor stimulation of cells with mutant NF-M in the presence of forskolin exhibited no inhibition of NF-tail domain phosphorylation compared with the wild type NF-M-transfected cells. This is consistent with our hypothesis that transient phosphorylation of NF-M head domains inhibits tail domain phosphorylation and suggests this as one of several mechanisms underlying topographic regulation.
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Affiliation(s)
- Ya-Li Zheng
- Laboratory of Neurochemistry, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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45
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Helfand BT, Loomis P, Yoon M, Goldman RD. Rapid transport of neural intermediate filament protein. J Cell Sci 2003; 116:2345-59. [PMID: 12711702 DOI: 10.1242/jcs.00526] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Peripherin is a neural intermediate filament protein that is expressed in peripheral and enteric neurons, as well as in PC12 cells. A determination of the motile properties of peripherin has been undertaken in PC12 cells during different stages of neurite outgrowth. The results reveal that non-filamentous, non-membrane bound peripherin particles and short peripherin intermediate filaments, termed 'squiggles', are transported at high speed throughout PC12 cell bodies, neurites and growth cones. These movements are bi-directional, and the majority require microtubules along with their associated molecular motors, conventional kinesin and cytoplasmic dynein. Our data demonstrate that peripherin particles and squiggles can move as components of a rapid transport system capable of delivering cytoskeletal subunits to the most distal regions of neurites over relatively short time periods.
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Affiliation(s)
- Brian T Helfand
- Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Ward 11-145, Chicago, IL 60611, USA
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46
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Abstract
Neurofilaments are one of the major components of the neuronal cytoskeleton and are responsible for maintaining the calibre of axons. They are modified by post-translational changes that are regulated in complex fashions including by the interaction with neighbouring glial cells. Neurofilament accumulations are seen in several neurological diseases and neurofilament mutations have now been associated with Charcot-Marie-Tooth disease, Parkinson's disease and amyotrophic lateral sclerosis. In this review, we discuss the structure, normal function and molecular pathology of neurofilaments.
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Affiliation(s)
- Ammar Al-Chalabi
- Departments of Neuroscience and Neurology, Institute of Psychiatry, King's College London, London SE5 8AF, UK.
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47
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Fernyhough P, Schmidt RE. Neurofilaments in diabetic neuropathy. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2003; 50:115-44. [PMID: 12198808 DOI: 10.1016/s0074-7742(02)50075-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This review discusses the role of abnormal neurofilament (NF) expression, processing, and structure as an etiological factor in diabetic neuropathy. Diabetic sensory and autonomic neuropathy in humans is associated with a spectrum of structural changes in peripheral nerve that includes axonal degeneration, paranodal demyelination, and loss of myelinated fibers-- the latter is probably the result of a dying-back of distal axons. NF filaments are composed of three subunit proteins, NFL, NFM, and NFH, and are major constituents of the axonal cylinder. It is clear that any abnormality in synthesis, delivery, or processing of these critical proteins could lead to severe impairments in axon structure and function. This article describes mechanisms of synthesis, phosphorylation, and delivery of NF and discusses how these processes may be abnormal in diabetics. The pathological alterations in the ganglion and preipheral nerve that occur in sensory and autonomic neuropath will be outlined and related to possible abnormal processing of NF. A major focus is the role or aberrant NF phosphorylation and its possible involvement in the imparied delivery of NF to the distal axon. Identification of stress-activated protein kinases (SAPKs) as NF kinases is discussed in detail and it is proposed that hyperglycemia-induced activation of SAPKs may be a primary etiological event in diabetic neuropathy.
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Affiliation(s)
- Paul Fernyhough
- School of Biological Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
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48
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Aranda-Espinoza H, Carl P, Leterrier JF, Janmey P, Discher DE. Domain unfolding in neurofilament sidearms: effects of phosphorylation and ATP. FEBS Lett 2002; 531:397-401. [PMID: 12435582 DOI: 10.1016/s0014-5793(02)03515-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Lateral projections of neurofilaments (NF) called sidearms (SA) affect axon stability and caliber. SA phosphorylation is thought to modulate inter-NF distance and interactions between NF and other subcellular organelles. SA were probed by atomic force microscopy (AFM) and dynamic light scattering (DLS) as a function of phosphorylation and ATP content. DLS shows SA are larger when phosphorylated, and AFM shows four unfoldable domains in SA regardless of phosphorylation state or the presence of ATP. However, the native phosphorylated SA requires three-fold higher force to unfold by AFM than dephosphorylated SA, suggesting a less pliant as well as larger structure when phosphorylated.
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Affiliation(s)
- Helim Aranda-Espinoza
- Institute for Medicine and Engineering, 1080 Vagelos Research Laboratory, 3340 Smith Walk, University of Pennsylvania, Philadelphia, PA 19104, USA.
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49
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Rao MV, Garcia ML, Miyazaki Y, Gotow T, Yuan A, Mattina S, Ward CM, Calcutt NA, Uchiyama Y, Nixon RA, Cleveland DW. Gene replacement in mice reveals that the heavily phosphorylated tail of neurofilament heavy subunit does not affect axonal caliber or the transit of cargoes in slow axonal transport. J Cell Biol 2002; 158:681-93. [PMID: 12186852 PMCID: PMC2174004 DOI: 10.1083/jcb.200202037] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2002] [Revised: 06/24/2002] [Accepted: 06/25/2002] [Indexed: 11/22/2022] Open
Abstract
The COOH-terminal tail of mammalian neurofilament heavy subunit (NF-H), the largest neurofilament subunit, contains 44-51 lysine-serine-proline repeats that are nearly stoichiometrically phosphorylated after assembly into neurofilaments in axons. Phosphorylation of these repeats has been implicated in promotion of radial growth of axons, control of nearest neighbor distances between neurofilaments or from neurofilaments to other structural components in axons, and as a determinant of slow axonal transport. These roles have now been tested through analysis of mice in which the NF-H gene was replaced by one deleted in the NF-H tail. Loss of the NF-H tail and all of its phosphorylation sites does not affect the number of neurofilaments, alter the ratios of the three neurofilament subunits, or affect the number of microtubules in axons. Additionally, it does not reduce interfilament spacing of most neurofilaments, the speed of action potential propagation, or mature cross-sectional areas of large motor or sensory axons, although its absence slows the speed of acquisition of normal diameters. Most surprisingly, at least in optic nerve axons, loss of the NF-H tail does not affect the rate of transport of neurofilament subunits.
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Affiliation(s)
- Mala V Rao
- Nathan Kline Institute, New York University School of Medicine, Orangeburg, NY 10962, USA.
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50
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Pan N, Sun Y, Chen S, Jin Y, Chen J. NF-L and NF-M are expressed in epithelial cells and coassemble with keratin or vimentin. CHINESE SCIENCE BULLETIN-CHINESE 2001. [DOI: 10.1007/bf02900594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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