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Rosenbluth J, Schiff R, Lam P. Effects of osmolality on PLP-null myelin structure: implications re axon damage. Brain Res 2008; 1253:191-7. [PMID: 19094971 DOI: 10.1016/j.brainres.2008.11.066] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Revised: 11/14/2008] [Accepted: 11/18/2008] [Indexed: 10/21/2022]
Abstract
In order to test the adhesiveness of PLP-null compact myelin lamellae we soaked aldehyde-fixed CNS specimens from PLP-null and control mice overnight in distilled water, in Ringer's solution or in Ringer's solution with added 1 M sucrose. Subsequent examination of the tissue by EM showed that both PLP-null and control white matter soaked in Ringer remained largely compact. After the distilled water soak, control myelin was virtually unchanged, but PLP-null myelin showed some decompaction, i.e., separation of myelin lamellae from one another. After the sucrose/Ringer soak, normal myelin developed foci of decompaction, but the great majority of lamellae remained compact. In the PLP-null specimens, in contrast, many of the myelin sheaths became almost completely decompacted. Such sheaths became thicker overall and were comprised of lamellae widely separated from one another by irregular spaces. Thus, in normal animals, fixed CNS myelin lamellae are firmly adherent and resist separation; PLP-null myelin lamellae, in contrast, are poorly adherent and more readily separated. Mechanisms by which impaired adhesiveness of PLP-null myelin lamellae and fluctuations in osmolality in vivo might underlie slowing of conduction and axon damage are discussed.
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Affiliation(s)
- Jack Rosenbluth
- Department of Physiology and Neuroscience, New York University School of Medicine, New York, NY 10016, USA.
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Yoshikawa F, Sato Y, Tohyama K, Akagi T, Hashikawa T, Nagakura-Takagi Y, Sekine Y, Morita N, Baba H, Suzuki Y, Sugano S, Sato A, Furuichi T. Opalin, a transmembrane sialylglycoprotein located in the central nervous system myelin paranodal loop membrane. J Biol Chem 2008; 283:20830-40. [PMID: 18490449 PMCID: PMC3258930 DOI: 10.1074/jbc.m801314200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Revised: 04/22/2008] [Indexed: 01/13/2023] Open
Abstract
In contrast to compact myelin, the series of paranodal loops located in the outermost lateral region of myelin is non-compact; the intracellular space is filled by a continuous channel of cytoplasm, the extracellular surfaces between neighboring loops keep a definite distance, but the loop membranes have junctional specializations. Although the proteins that form compact myelin have been well studied, the protein components of paranodal loop membranes are not fully understood. This report describes the biochemical characterization and expression of Opalin as a novel membrane protein in paranodal loops. Mouse Opalin is composed of a short N-terminal extracellular domain (amino acid residues 1-30), a transmembrane domain (residues 31-53), and a long C-terminal intracellular domain (residues 54-143). Opalin is enriched in myelin of the central nervous system, but not that of the peripheral nervous system of mice. Enzymatic deglycosylation showed that myelin Opalin contained N- and O-glycans, and that the O-glycans, at least, had negatively charged sialic acids. We identified two N-glycan sites at Asn-6 and Asn-12 and an O-glycan site at Thr-14 in the extracellular domain. Site-directed mutations at the glycan sites impaired the cell surface localization of Opalin. In addition to the somata and processes of oligodendrocytes, Opalin immunoreactivity was observed in myelinated axons in a spiral fashion, and was concentrated in the paranodal loop region. Immunogold electron microscopy demonstrated that Opalin was localized at particular sites in the paranodal loop membrane. These results suggest a role for highly sialylglycosylated Opalin in an intermembranous function of the myelin paranodal loops in the central nervous system.
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Affiliation(s)
- Fumio Yoshikawa
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Yumi Sato
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Koujiro Tohyama
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Takumi Akagi
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Tsutomu Hashikawa
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Yuko Nagakura-Takagi
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Yukiko Sekine
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Noriyuki Morita
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Hiroko Baba
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Yutaka Suzuki
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Sumio Sugano
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Akira Sato
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
| | - Teiichi Furuichi
- Laboratory for Molecular Neurogenesis and
Laboratory for Neural Architecture, RIKEN Brain
Science Institute, Wako 351-0198, The Center for
Electron Microscopy and Bio-Imaging Research, Iwate Medical University,
Morioka 020-8505, the Tokyo University of
Pharmacy and Life Sciences, Hachioji 192-0392, and the
Department of Frontier Science, University of Tokyo,
Tokyo 108-8639, Japan
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Werner HB, Kuhlmann K, Shen S, Uecker M, Schardt A, Dimova K, Orfaniotou F, Dhaunchak A, Brinkmann BG, Möbius W, Guarente L, Casaccia-Bonnefil P, Jahn O, Nave KA. Proteolipid protein is required for transport of sirtuin 2 into CNS myelin. J Neurosci 2007; 27:7717-30. [PMID: 17634366 PMCID: PMC2676101 DOI: 10.1523/jneurosci.1254-07.2007] [Citation(s) in RCA: 193] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Mice lacking the expression of proteolipid protein (PLP)/DM20 in oligodendrocytes provide a genuine model for spastic paraplegia (SPG-2). Their axons are well myelinated but exhibit impaired axonal transport and progressive degeneration, which is difficult to attribute to the absence of a single myelin protein. We hypothesized that secondary molecular changes in PLP(null) myelin contribute to the loss of PLP/DM20-dependent neuroprotection and provide more insight into glia-axonal interactions in this disease model. By gel-based proteome analysis, we identified >160 proteins in purified myelin membranes, which allowed us to systematically monitor the CNS myelin proteome of adult PLP(null) mice, before the onset of disease. We identified three proteins of the septin family to be reduced in abundance, but the nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase sirtuin 2 (SIRT2) was virtually absent. SIRT2 is expressed throughout the oligodendrocyte lineage, and immunoelectron microscopy revealed its association with myelin. Loss of SIRT2 in PLP(null) was posttranscriptional, suggesting that PLP/DM20 is required for its transport into the myelin compartment. Because normal SIRT2 activity is controlled by the NAD+/NADH ratio, its function may be coupled to the axo-glial metabolism and the long-term support of axons by oligodendrocytes.
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Affiliation(s)
- Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, D-37075 Goettingen, Germany.
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DeBruin LS, Haines JD, Bienzle D, Harauz G. Partitioning of myelin basic protein into membrane microdomains in a spontaneously demyelinating mouse model for multiple sclerosisThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Membrane Proteins in Health and Disease. Biochem Cell Biol 2006; 84:993-1005. [PMID: 17215885 DOI: 10.1139/o06-180] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
We have characterized the lipid rafts in myelin from a spontaneously demyelinating mouse line (ND4), and from control mice (CD1 background), as a function of age and severity of disease. Myelin was isolated from the brains of CD1 and ND4 mice at various ages, and cold lysed with 1.5% CHAPS (3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulphonate). The lysate was separated by low-speed centrifugation into supernatant and pellet fractions, which were characterized by Western blotting for myelin basic protein (MBP) isoforms and their post-translationally modified variants. We found that, with maturation and with disease progression, there was a specific redistribution of the 14–21.5 kDa MBP isoforms (classic exon-II-containing vs exon-II-lacking) and phosphorylated forms into the supernatant and pellet. Further fractionation of the supernatant to yield detergent-resistant membranes (DRMs), representing coalesced lipid rafts, showed these to be highly enriched in exon-II-lacking MBP isoforms, and deficient in methylated MBP variants, in mice of both genotypes. The DRMs from the ND4 mice appeared to be enriched in MBP phosphorylated by MAP kinase at Thr95 (murine 18.5 kDa numbering). These studies indicate that different splice isoforms and post-translationally modified charge variants of MBP are targeted to different microdomains in the myelin membrane, implying multifunctionality of this protein family in myelin maintenance.
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Affiliation(s)
- Lillian S DeBruin
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
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