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Normal Cortical Myelination in Galectin-4-Deficient Mice. Cells 2022; 11:cells11213485. [DOI: 10.3390/cells11213485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/26/2022] [Accepted: 10/27/2022] [Indexed: 11/06/2022] Open
Abstract
Myelin, critical for the correct function of the nervous system, is organized in different patterns that can include long non-myelinated axonal segments. How myelin patterning is regulated remains unexplained. The carbohydrate-binding protein galectin-4 (Gal-4) influences oligodendrocyte differentiation in vitro and is associated with non-myelinable axon segments (NMS) in cultured neurons. In consequence, Gal-4 has been proposed as a myelin patterning regulator, although no in vivo studies have corroborated this hypothesis. We used Gal-4-deficient mice (Lgals4-KO) to study the role of Gal-4 in cortical myelination in vivo. We show that cultured neurons of Lgals4-KO mice form NMS that are regulated as in control neurons. In addition, oligodendrocyte/myelin markers expression measured by biochemical and immunochemical means, and cortical myelin microstructure studied by in-depth image analysis appear unaltered in these animals. Consistently, myelin displays an essentially normal function assessed by in vivo electrophysiology and locomotion analyses. In conclusion, cortical myelin of Lgals4-KO mice does not show any significant defect in composition, organization or function, pointing to a negligible role of Gal-4 in myelination in vivo or, as discussed, to unknown mechanisms that compensate its absence.
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2
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Veneri FA, Prada V, Mastrangelo R, Ferri C, Nobbio L, Passalacqua M, Milanesi M, Bianchi F, Del Carro U, Vallat JM, Duong P, Svaren J, Schenone A, Grandis M, D’Antonio M. A novel mouse model of CMT1B identifies hyperglycosylation as a new pathogenetic mechanism. Hum Mol Genet 2022; 31:4255-4274. [PMID: 35908287 PMCID: PMC9759335 DOI: 10.1093/hmg/ddac170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 07/19/2022] [Accepted: 07/20/2022] [Indexed: 01/21/2023] Open
Abstract
Mutations in the Myelin Protein Zero gene (MPZ), encoding P0, the major structural glycoprotein of peripheral nerve myelin, are the cause of Charcot-Marie-Tooth (CMT) type 1B neuropathy, and most P0 mutations appear to act through gain-of-function mechanisms. Here, we investigated how misglycosylation, a pathomechanism encompassing several genetic disorders, may affect P0 function. Using in vitro assays, we showed that gain of glycosylation is more damaging for P0 trafficking and functionality as compared with a loss of glycosylation. Hence, we generated, via CRISPR/Cas9, a mouse model carrying the MPZD61N mutation, predicted to generate a new N-glycosylation site in P0. In humans, MPZD61N causes a severe early-onset form of CMT1B, suggesting that hyperglycosylation may interfere with myelin formation, leading to pathology. We show here that MPZD61N/+ mice develop a tremor as early as P15 which worsens with age and correlates with a significant motor impairment, reduced muscular strength and substantial alterations in neurophysiology. The pathological analysis confirmed a dysmyelinating phenotype characterized by diffuse hypomyelination and focal hypermyelination. We find that the mutant P0D61N does not cause significant endoplasmic reticulum stress, a common pathomechanism in CMT1B, but is properly trafficked to myelin where it causes myelin uncompaction. Finally, we show that myelinating dorsal root ganglia cultures from MPZD61N mice replicate some of the abnormalities seen in vivo, suggesting that they may represent a valuable tool to investigate therapeutic approaches. Collectively, our data indicate that the MPZD61N/+ mouse represents an authentic model of severe CMT1B affirming gain-of-glycosylation in P0 as a novel pathomechanism of disease.
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Affiliation(s)
- Francesca A Veneri
- Biology of Myelin Unit, Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy,Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genova, IRCCS AOU San Martino-IST, 16132 Genova, Italy
| | - Valeria Prada
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genova, IRCCS AOU San Martino-IST, 16132 Genova, Italy
| | - Rosa Mastrangelo
- Biology of Myelin Unit, Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Cinzia Ferri
- Biology of Myelin Unit, Division of Genetics and Cell Biology, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Lucilla Nobbio
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genova, IRCCS AOU San Martino-IST, 16132 Genova, Italy
| | - Mario Passalacqua
- Department of Experimental Medicine, University of Genova, 16132 Genova, Italy
| | - Maria Milanesi
- Experimental Oncology and Immunology, Department of Molecular and Translational Medicine, University of Brescia, 25123 Brescia, Italy
| | - Francesca Bianchi
- Movement Disorders Unit, Division of Neuroscience, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Ubaldo Del Carro
- Movement Disorders Unit, Division of Neuroscience, IRCCS Ospedale San Raffaele, 20132 Milan, Italy
| | - Jean-Michel Vallat
- Department and Laboratory of Neurology, National Reference Center for ‘Rare Peripheral Neuropathies’, University Hospital of Limoges (CHU Limoges), Dupuytren Hospital, 87000 Limoges, France
| | - Phu Duong
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - John Svaren
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Angelo Schenone
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genova, IRCCS AOU San Martino-IST, 16132 Genova, Italy,Department of Neurology, IRCCS Ospedale Policlinico San Martino, 16132 Genova, Italy
| | - Marina Grandis
- To whom correspondence should be addressed at: Department of Neurology, IRCCS Ospedale Policlinico San Martino, Largo Daneo 3, 16132 Genova, Italy. Tel: +39 010 3537562; (M.G.); San Raffaele Scientific Institute, DIBIT, via Olgettina 58, 20132 Milan, Italy. Tel: +39 02 26435307; (M.D.)
| | - Maurizio D’Antonio
- To whom correspondence should be addressed at: Department of Neurology, IRCCS Ospedale Policlinico San Martino, Largo Daneo 3, 16132 Genova, Italy. Tel: +39 010 3537562; (M.G.); San Raffaele Scientific Institute, DIBIT, via Olgettina 58, 20132 Milan, Italy. Tel: +39 02 26435307; (M.D.)
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Mathews R, Ramya L. A comparative study for the intermediate states of myelin oligodendrocyte glycoprotein in the absence and presence of glycan - A computational approach. J Mol Graph Model 2019; 96:107517. [PMID: 31881468 DOI: 10.1016/j.jmgm.2019.107517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/19/2019] [Accepted: 12/19/2019] [Indexed: 10/25/2022]
Abstract
Myelin Oligodendrocyte glycoprotein (MOG) is found to play an important role in providing structural integrity to myelin sheath at the same time it acts as an auto-antigen which might lead to Multiple Sclerosis (MS). What causes this specific property of being an auto-antigen is still not known. Here we present molecular dynamics simulation studies of unfolding and folding of the protein MOG in both the absence and presence of N-glycan in order to understand the role of glycosylation in the stability and flexibility of the protein. The main results from these studies show that the glycosylation increases the stability of the protein MOG and inhibits the complete unfolding of MOG in the SMD. From the folding studies using TMD, it was observed that the glycan helps the protein to attain the near-native folded conformation. However, it was also observed from the direct TMD studies that the pathway of protein folding was enhanced by the trace-back of intermediate states in the presence of glycan.
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Affiliation(s)
- Rita Mathews
- School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, Tamilnadu, India
| | - L Ramya
- School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, Tamilnadu, India.
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4
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Ramya L. Role of N-glycan in the structural changes of myelin oligodendrocyte glycoprotein and its complex with an antibody. J Biomol Struct Dyn 2019; 38:1649-1658. [PMID: 31057084 DOI: 10.1080/07391102.2019.1614999] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Myelin Oligodendrocyte Glycoprotein (MOG) is found on the external surface of the myelin sheath and plays an important role in neurodegenerative diseases. It was observed that the protein MOG acts as an autoantigen and results in demyelination. The cause for the sudden change of protein to be autoantigen is still unclear. Here we present the molecular dynamics simulation studies of MOG in both unbound and bound states with an antibody. Both these systems were studied in the absence and presence of N-glycan in order to understand the effect of glycosylation in the MOG conformational changes. The results indicate that the glycosylation decreases the flexibility of protein in both free and bound states. Glycan influence the interaction of the complex with the water molecules whereas free protein MOG interaction with water molecules was not affected by the glycosylation. Glycan changes the 310 helices adjacent to the antibody interacting epitope MOG35-55 to turns.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- L Ramya
- School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, Tamilnadu, India
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5
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Gilloteaux J, Subramanian K, Solomon N, Nicaise C. The leptin receptor mutation of the obese Zucker rat causes sciatic nerve demyelination with a centripetal pattern defect. Ultrastruct Pathol 2018; 42:377-408. [PMID: 30339059 DOI: 10.1080/01913123.2018.1522405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Young male Zucker rats with a leptin receptor mutation are obese, have a non-insulin-dependent diabetes mellitus (NIDDM), and other endocrinopathies. Tibial branches of the sciatic nerve reveal a progressive demyelination that progresses out of the Schwann cells (SCs) where electron-contrast deposits are accumulated while the minor lines or intermembranous SC contacts display exaggerated spacings. Cajal bands contain diversely contrasted vesicles adjacent to the abaxonal myelin layer with blemishes; they appear dispatched centripetally out of many narrow electron densities, regularly spaced around the myelin annulus. These anomalies widen and yield into sectors across the stacked myelin layers. Throughout the worse degradations, the adaxonal membrane remains along the axonal neuroplasm. This peripheral neuropathy with irresponsive leptin cannot modulate hypothalamic-pituitary-adrenal axis and SC neurosteroids, thus exacerbates NIDDM condition. Additionally, the ultrastructure of the progressive myelin alterations may have unraveled a peculiar, centripetal mode of trafficking maintenance of the peripheral nervous system myelin, while some adhesive glycoproteins remain between myelin layers, somewhat hindering the axon mutilation. Heading title: Peripheral neuropathy and myelin.
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Affiliation(s)
- Jacques Gilloteaux
- a Department of Anatomical Sciences , St George's University School of Medicine, K.B. Taylor Global Scholar's Program at Northumbria University , Newcastle upon Tyne , UK.,b Unité de Recherche en Physiologie Moléculaire (URPhyM), Laboratoire de Neurodégénérescence et Régénération, Département de Médecine , Université de Namur , Namur , Belgium
| | - Kritika Subramanian
- a Department of Anatomical Sciences , St George's University School of Medicine, K.B. Taylor Global Scholar's Program at Northumbria University , Newcastle upon Tyne , UK.,c Department of Clinical and Epidemiological Virology , Rega Institute of Medical Research, Katholiele Universiteit Leuven , Leuven , Belgium
| | - Nadia Solomon
- a Department of Anatomical Sciences , St George's University School of Medicine, K.B. Taylor Global Scholar's Program at Northumbria University , Newcastle upon Tyne , UK
| | - Charles Nicaise
- b Unité de Recherche en Physiologie Moléculaire (URPhyM), Laboratoire de Neurodégénérescence et Régénération, Département de Médecine , Université de Namur , Namur , Belgium
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García-Mateo N, Pascua-Maestro R, Pérez-Castellanos A, Lillo C, Sanchez D, Ganfornina MD. Myelin extracellular leaflet compaction requires apolipoprotein D membrane management to optimize lysosomal-dependent recycling and glycocalyx removal. Glia 2017; 66:670-687. [PMID: 29222871 DOI: 10.1002/glia.23274] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 11/09/2017] [Accepted: 11/17/2017] [Indexed: 11/07/2022]
Abstract
To compact the extracellular sides of myelin, an important transition must take place: from membrane sliding, while building the wraps, to membrane adhesion and water exclusion. Removal of the negatively charged glycocalyx becomes the limiting factor in such transition. What is required to initiate this membrane-zipping process? Knocking-out the Lipocalin Apolipoprotein D (ApoD), essential for lysosomal functional integrity in glial cells, results in a specific defect in myelin extracellular leaflet compaction in peripheral and central nervous system, which results in reduced conduction velocity and suboptimal behavioral outputs: motor learning is compromised. Myelination initiation, growth, intracellular leaflet compaction, myelin thickness or internodal length remain unaltered. Lack of ApoD specifically modifies Plp and P0 protein expression, but not Mbp or Mag. Late in myelin maturation period, ApoD affects lipogenic and growth-related, but not stress-responsive, signaling pathways. Without ApoD, the sialylated glycocalyx is maintained and ganglioside content remains high. In peripheral nervous system, Neu3 membrane sialidase and lysosomal Neu1 are coordinately expressed with ApoD in subsets of Schwann cells. ApoD-KO myelin becomes depleted of Neu3 and enriched in Fyn, a kinase with pivotal roles in transducing axon-derived signals into myelin properties. In the absence of ApoD, partial permeabilization of lysosomes alters Neu1 location as well. Exogenous ApoD rescues ApoD-KO hypersialylated glycocalyx in astrocytes, demonstrating that ApoD is necessary and sufficient to control glycocalyx composition in glial cells. By ensuring lysosomal functional integrity and adequate subcellular location of effector and regulatory proteins, ApoD guarantees the glycolipid recycling and glycocalyx removal required to complete myelin compaction.
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Affiliation(s)
- Nadia García-Mateo
- Instituto de Biología y Genética Molecular-Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid-CSIC, Valladolid, Spain
| | - Raquel Pascua-Maestro
- Instituto de Biología y Genética Molecular-Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid-CSIC, Valladolid, Spain
| | - Alberto Pérez-Castellanos
- Instituto de Biología y Genética Molecular-Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid-CSIC, Valladolid, Spain
| | - Concepción Lillo
- Instituto de Neurociencias de Castilla y León, IBSAL, Universidad de Salamanca, Salamanca, Spain
| | - Diego Sanchez
- Instituto de Biología y Genética Molecular-Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid-CSIC, Valladolid, Spain
| | - Maria D Ganfornina
- Instituto de Biología y Genética Molecular-Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid-CSIC, Valladolid, Spain
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7
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Yoshimura T, Hayashi A, Handa-Narumi M, Yagi H, Ohno N, Koike T, Yamaguchi Y, Uchimura K, Kadomatsu K, Sedzik J, Kitamura K, Kato K, Trapp BD, Baba H, Ikenaka K. GlcNAc6ST-1 regulates sulfation of N-glycans and myelination in the peripheral nervous system. Sci Rep 2017; 7:42257. [PMID: 28186137 PMCID: PMC5301494 DOI: 10.1038/srep42257] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 01/05/2017] [Indexed: 01/09/2023] Open
Abstract
Highly specialized glial cells wrap axons with a multilayered myelin membrane in vertebrates. Myelin serves essential roles in the functioning of the nervous system. Axonal degeneration is the major cause of permanent neurological disability in primary myelin diseases. Many glycoproteins have been identified in myelin, and a lack of one myelin glycoprotein results in abnormal myelin structures in many cases. However, the roles of glycans on myelin glycoproteins remain poorly understood. Here, we report that sulfated N-glycans are involved in peripheral nervous system (PNS) myelination. PNS myelin glycoproteins contain highly abundant sulfated N-glycans. Major sulfated N-glycans were identified in both porcine and mouse PNS myelin, demonstrating that the 6-O-sulfation of N-acetylglucosamine (GlcNAc-6-O-sulfation) is highly conserved in PNS myelin between these species. P0 protein, the most abundant glycoprotein in PNS myelin and mutations in which at the glycosylation site cause Charcot-Marie-Tooth neuropathy, has abundant GlcNAc-6-O-sulfated N-glycans. Mice deficient in N-acetylglucosamine-6-O-sulfotransferase-1 (GlcNAc6ST-1) failed to synthesize sulfated N-glycans and exhibited abnormal myelination and axonal degeneration in the PNS. Taken together, this study demonstrates that GlcNAc6ST-1 modulates PNS myelination and myelinated axonal survival through the GlcNAc-6-O-sulfation of N-glycans on glycoproteins. These findings may provide novel insights into the pathogenesis of peripheral neuropathy.
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Affiliation(s)
- Takeshi Yoshimura
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
- Department of Physiological Sciences, School of Life Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
| | - Akiko Hayashi
- Department of Molecular Neurobiology, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
| | - Mai Handa-Narumi
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
- Department of Physiological Sciences, School of Life Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
| | - Hirokazu Yagi
- Department of Structural Biology and Biomolecular Engineering, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Aichi 467-8603, Japan
| | - Nobuhiko Ohno
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
- Department of Physiological Sciences, School of Life Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
| | - Takako Koike
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
| | - Yoshihide Yamaguchi
- Department of Molecular Neurobiology, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
| | - Kenji Uchimura
- Department of Biochemistry, Graduate School of Medicine, Nagoya University, Nagoya, Aichi 466-8550, Japan
| | - Kenji Kadomatsu
- Department of Biochemistry, Graduate School of Medicine, Nagoya University, Nagoya, Aichi 466-8550, Japan
| | - Jan Sedzik
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
- Department of Chemical Engineering and Technology, Protein Crystallization Facility, Royal Institute of Technology, KTH, Stockholm 10044, Sweden
| | - Kunio Kitamura
- Faculty of Health and Medical Care, Saitama Medical University, Hidaka, Saitama 350-1241, Japan
| | - Koichi Kato
- Department of Structural Biology and Biomolecular Engineering, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Aichi 467-8603, Japan
- Institute for Molecular Science and Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
| | - Bruce D. Trapp
- Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Hiroko Baba
- Department of Molecular Neurobiology, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
| | - Kazuhiro Ikenaka
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
- Department of Physiological Sciences, School of Life Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
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8
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Partial Immunoblotting of 2D-Gels: A Novel Method to Identify Post-Translationally Modified Proteins Exemplified for the Myelin Acetylome. Proteomes 2017; 5:proteomes5010003. [PMID: 28248254 PMCID: PMC5372224 DOI: 10.3390/proteomes5010003] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 12/23/2016] [Accepted: 01/04/2017] [Indexed: 11/17/2022] Open
Abstract
Post-translational modifications (PTMs) play a key role in regulating protein function, yet their identification is technically demanding. Here, we present a straightforward workflow to systematically identify post-translationally modified proteins based on two-dimensional gel electrophoresis. Upon colloidal Coomassie staining the proteins are partially transferred, and the investigated PTMs are immunodetected. This strategy allows tracking back the immunopositive antigens to the corresponding spots on the original gel, from which they are excised and mass spectrometrically identified. Candidate proteins are validated on the same membrane by immunodetection using a second fluorescence channel. We exemplify the power of partial immunoblotting with the identification of lysine-acetylated proteins in myelin, the oligodendroglial membrane that insulates neuronal axons. The excellent consistency of the detected fluorescence signals at all levels allows the differential comparison of PTMs across multiple conditions. Beyond PTM screening, our multi-level workflow can be readily adapted to clinical applications such as identifying auto-immune antigens or host-pathogen interactions.
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Pronker MF, Lemstra S, Snijder J, Heck AJR, Thies-Weesie DME, Pasterkamp RJ, Janssen BJC. Structural basis of myelin-associated glycoprotein adhesion and signalling. Nat Commun 2016; 7:13584. [PMID: 27922006 PMCID: PMC5150538 DOI: 10.1038/ncomms13584] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 10/17/2016] [Indexed: 01/06/2023] Open
Abstract
Myelin-associated glycoprotein (MAG) is a myelin-expressed cell-adhesion and bi-directional signalling molecule. MAG maintains the myelin–axon spacing by interacting with specific neuronal glycolipids (gangliosides), inhibits axon regeneration and controls myelin formation. The mechanisms underlying MAG adhesion and signalling are unresolved. We present crystal structures of the MAG full ectodomain, which reveal an extended conformation of five Ig domains and a homodimeric arrangement involving membrane-proximal domains Ig4 and Ig5. MAG-oligosaccharide complex structures and biophysical assays show how MAG engages axonal gangliosides at domain Ig1. Two post-translational modifications were identified—N-linked glycosylation at the dimerization interface and tryptophan C-mannosylation proximal to the ganglioside binding site—that appear to have regulatory functions. Structure-guided mutations and neurite outgrowth assays demonstrate MAG dimerization and carbohydrate recognition are essential for its regeneration-inhibiting properties. The combination of trans ganglioside binding and cis homodimerization explains how MAG maintains the myelin–axon spacing and provides a mechanism for MAG-mediated bi-directional signalling. Myelin-associated glycoprotein (MAG) maintains myelin-axon spacing. Here, the authors report the crystal structures of the MAG full ectodomain in complex with oligosaccharide, and use additional assays to provide insights into the mechanism of MAG-mediated signalling.
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Affiliation(s)
- Matti F Pronker
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Suzanne Lemstra
- Department for Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
| | - Joost Snijder
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Department of Chemistry and Department of Pharmaceutical Sciences, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Department of Chemistry and Department of Pharmaceutical Sciences, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Dominique M E Thies-Weesie
- Van't Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute of Nanomaterials Science, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - R Jeroen Pasterkamp
- Department for Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
| | - Bert J C Janssen
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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10
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Glu-tubulin is a marker for Schwann cells and can distinguish between schwannomas and neurofibromas. Histochem Cell Biol 2016; 146:467-77. [PMID: 27278446 DOI: 10.1007/s00418-016-1455-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/25/2016] [Indexed: 10/21/2022]
Abstract
Schwann cells generate myelin sheaths around the axons of the peripheral nervous system, thus facilitating efficient nerve impulse propagation. Two main tumor types can arise from peripheral nerves, schwannomas and neurofibromas, which are sometimes difficult to distinguish and may require the use of diagnostic biomarkers. Here, we characterize a new marker for Schwann cells and its potential use as a diagnostic marker for schwannomas. Immunohistochemistry for Glu-tubulin, a posttranslational modification of α-tubulin, was performed in mouse and human tissues. This technique labels Schwann cells but not oligodendrocytes. All peripheral nerves were immunoreactive for this antibody, including large nerve trunks, thin myelinated nerves, as well as the myenteric and submucous plexus of the digestive tract. In the mouse brain, many neurons were immunoreactive for Glu-tubulin but oligodendrocytes were negative. During embryo development, immunoreactive nerves were already found at E10. In Schwann cells, the staining is restricted to the myelin sheaths and is not present in the perinuclear cytoplasm or the Ranvier nodes. Primary cultures of fibroblasts and Schwann cells were established from mouse sciatic nerves, and Western blot analysis showed that Glu-tubulin immunoreactivity was found in the Schwann cells but not in the fibroblasts. Clinical specimens of schwannomas (n = 20) and neurofibromas (n = 20) were stained with anti-Glu-tubulin antibodies. Schwannomas presented a strong staining in all tumor cells, whereas neurofibromas had a light speckled staining pattern, easily distinguishable from the one found in schwannomas. In conclusion, Glu-tubulin can be used as a marker of Schwann cells and can help in diagnosing peripheral nerve tumors.
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11
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Oliveira MJ, Águas AP. High concentration of phosphorus is a distinctive feature of myelin. An X-Ray elemental microanalysis study using freeze-fracture scanning electron microscopy of rat sciatic nerve. Microsc Res Tech 2015; 78:537-9. [DOI: 10.1002/jemt.22506] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 03/26/2015] [Indexed: 11/08/2022]
Affiliation(s)
| | - Artur P. Águas
- Department of Anatomy and UMIB; ICBAS, University of Porto; Porto Portugal
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