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He L, Jiang W, Li J, Wang C. Crystal structure of Ankyrin-G in complex with a fragment of Neurofascin reveals binding mechanisms required for integrity of the axon initial segment. J Biol Chem 2022; 298:102272. [PMID: 35850303 PMCID: PMC9396398 DOI: 10.1016/j.jbc.2022.102272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 07/12/2022] [Accepted: 07/13/2022] [Indexed: 11/23/2022] Open
Abstract
The axon initial segment (AIS) has characteristically dense clustering of voltage-gated sodium channels (Nav), cell adhesion molecule Neurofascin 186 (Nfasc), and neuronal scaffold protein Ankyrin-G (AnkG) in neurons, which facilitates generation of an action potential and maintenance of axonal polarity. However, the mechanisms underlying AIS assembly, maintenance, and plasticity remain poorly understood. Here, we report the high-resolution crystal structure of the AnkG ankyrin repeat (ANK repeat) domain in complex with its binding site in the Nfasc cytoplasmic tail that shows, in conjunction with binding affinity assays with serial truncation variants, the molecular basis of AnkG–Nfasc binding. We confirm AnkG interacts with the FIGQY motif in Nfasc, and we identify another region required for their high affinity binding. Our structural analysis revealed that ANK repeats form 4 hydrophobic or hydrophilic layers in the AnkG inner groove that coordinate interactions with essential Nfasc residues, including F1202, E1204, and Y1212. Moreover, we show disruption of the AnkG–Nfasc complex abolishes Nfasc enrichment at the AIS in cultured mouse hippocampal neurons. Finally, our structural and biochemical analysis indicated that L1 syndrome-associated mutations in L1CAM, a member of the L1 immunoglobulin family proteins including Nfasc, L1CAM, NrCAM, and CHL1, compromise binding with ankyrins. Taken together, these results define the mechanisms underlying AnkG–Nfasc complex formation and show that AnkG-dependent clustering of Nfasc is required for AIS integrity.
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Affiliation(s)
- Liping He
- Department of Neurology, The First Affiliated Hospital of USTC, Ministry of Education Key Laboratory for Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Biomedical Sciences and Health Laboratory of Anhui Province, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, P. R. China
| | - Wenli Jiang
- Department of Neurology, The First Affiliated Hospital of USTC, Ministry of Education Key Laboratory for Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Biomedical Sciences and Health Laboratory of Anhui Province, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, P. R. China
| | - Jianchao Li
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou, P. R. China.
| | - Chao Wang
- Department of Neurology, The First Affiliated Hospital of USTC, Ministry of Education Key Laboratory for Cellular Dynamics, Hefei National Research Center for Physical Sciences at the Microscale, Biomedical Sciences and Health Laboratory of Anhui Province, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, P. R. China.
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2
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Middleton SJ, Perez-Sanchez J, Dawes JM. The structure of sensory afferent compartments in health and disease. J Anat 2021; 241:1186-1210. [PMID: 34528255 PMCID: PMC9558153 DOI: 10.1111/joa.13544] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 08/12/2021] [Accepted: 08/30/2021] [Indexed: 12/20/2022] Open
Abstract
Primary sensory neurons are a heterogeneous population of cells able to respond to both innocuous and noxious stimuli. Like most neurons they are highly compartmentalised, allowing them to detect, convey and transfer sensory information. These compartments include specialised sensory endings in the skin, the nodes of Ranvier in myelinated axons, the cell soma and their central terminals in the spinal cord. In this review, we will highlight the importance of these compartments to primary afferent function, describe how these structures are compromised following nerve damage and how this relates to neuropathic pain.
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Affiliation(s)
- Steven J Middleton
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | | | - John M Dawes
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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3
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Abstract
The nodes of Ranvier have clustered Na+ and K+ channels necessary for rapid and efficient axonal action potential conduction. However, detailed mechanisms of channel clustering have only recently been identified: they include two independent axon-glia interactions that converge on distinct axonal cytoskeletons. Here, we discuss how glial cell adhesion molecules and the extracellular matrix molecules that bind them assemble combinations of ankyrins, spectrins and other cytoskeletal scaffolding proteins, which cluster ion channels. We present a detailed molecular model, incorporating these overlapping mechanisms, to explain how the nodes of Ranvier are assembled in both the peripheral and central nervous systems.
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Otani Y, Ohno N, Cui J, Yamaguchi Y, Baba H. Upregulation of large myelin protein zero leads to Charcot-Marie-Tooth disease-like neuropathy in mice. Commun Biol 2020; 3:121. [PMID: 32170207 PMCID: PMC7070019 DOI: 10.1038/s42003-020-0854-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Accepted: 02/24/2020] [Indexed: 01/01/2023] Open
Abstract
Charcot-Marie-Tooth (CMT) disease is a hereditary neuropathy mainly caused by gene mutation of peripheral myelin proteins including myelin protein zero (P0, MPZ). Large myelin protein zero (L-MPZ) is an isoform of P0 that contains an extended polypeptide synthesized by translational readthrough at the C-terminus in tetrapods, including humans. The physiological role of L-MPZ and consequences of an altered L-MPZ/P0 ratio in peripheral myelin are not known. To clarify this, we used genome editing to generate a mouse line (L-MPZ mice) that produced L-MPZ instead of P0. Motor tests and electrophysiological, immunohistological, and electron microscopy analyses show that homozygous L-MPZ mice exhibit CMT-like phenotypes including thin and/or loose myelin, increased small-caliber axons, and disorganized axo-glial interactions. Heterozygous mice show a milder phenotype. These results highlight the importance of an appropriate L-MPZ/P0 ratio and show that aberrant readthrough of a myelin protein causes neuropathy.
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Affiliation(s)
- Yoshinori Otani
- Department of Molecular Neurobiology, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan
| | - Nobuhiko Ohno
- Department of Anatomy, Division of Histology and Cell Biology, School of Medicine, Jichi Medical University, Shimotsuke, Japan
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, Okazaki, Japan
| | - Jingjing Cui
- Department of Molecular Neurobiology, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan
| | - Yoshihide Yamaguchi
- Department of Molecular Neurobiology, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan.
| | - Hiroko Baba
- Department of Molecular Neurobiology, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan
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5
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Avila F, Mickelson JR, Schaefer RJ, McCue ME. Genome-Wide Signatures of Selection Reveal Genes Associated With Performance in American Quarter Horse Subpopulations. Front Genet 2018; 9:249. [PMID: 30105047 PMCID: PMC6060370 DOI: 10.3389/fgene.2018.00249] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 06/22/2018] [Indexed: 11/13/2022] Open
Abstract
Selective breeding for athletic performance in various disciplines has resulted in population stratification within the American Quarter Horse (QH) breed. The goals of this study were to utilize high density genotype data to: (1) identify genomic regions undergoing positive selection within and among QH subpopulations; (2) investigate haplotype structure within each QH subpopulation; and (3) identify candidate genes within genomic regions of interest (ROI), as well as biological pathways, predicted to play a role in elite performance in each group. For that, 65K SNP genotyping data on 143 elite individuals from 6 QH subpopulations (cutting, halter, racing, reining, western pleasure, and working cow) were imputed to 2M SNPs. Signatures of selection were identified using FST-based (di ) and haplotype-based (hapFLK) analyses, accompanied by identification of local haplotype structure and sharing within subpopulations (hapQTL). Regions undergoing positive selection were identified on all 31 autosomes, and ROI on 2 chromosomes were identified by all 3 methods combined. Genes within each ROI were retrieved and used to identify pathways and genes that might contribute to performance in each subpopulation. These included, among others, candidate genes associated with skeletal muscle development, metabolism, and central nervous system development. This work improves our understanding of equine breed development, and provides breeders with a better understanding of how selective breeding impacts the performance of QH populations.
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Affiliation(s)
- Felipe Avila
- Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, United States
| | - James R Mickelson
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, United States
| | - Robert J Schaefer
- Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, United States
| | - Molly E McCue
- Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, United States
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Early and Late Loss of the Cytoskeletal Scaffolding Protein, Ankyrin G Reveals Its Role in Maturation and Maintenance of Nodes of Ranvier in Myelinated Axons. J Neurosci 2017; 37:2524-2538. [PMID: 28148727 DOI: 10.1523/jneurosci.2661-16.2017] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 12/15/2016] [Accepted: 01/25/2017] [Indexed: 11/21/2022] Open
Abstract
The mechanisms that govern node of Ranvier organization, stability, and long-term maintenance remain to be fully elucidated. One of the molecular components of the node is the cytoskeletal scaffolding protein, ankyrin G (AnkG), which interacts with multiple members of the nodal complex. The role of AnkG in nodal organization and maintenance is still not clearly defined as to whether AnkG functions as an initial nodal organizer or whether it functions as a nodal stabilizer after the nodal complex has been assembled. Using a mouse model system, we report here that perinatal and juvenile neuronal ablation of AnkG has differential consequences on nodal stability. Early loss of AnkG creates immature nodes with abnormal morphology, which undergo accelerated destabilization within a month, resulting in rapid voltage-gated sodium (NaV) channel and βIV spectrin loss with reduced effects on neurofascin 186. On the other hand, late ablation of AnkG from established nodal complexes leads to slow but progressive nodal destabilization over 10 months, primarily affecting βIV spectrin, followed by NaV channels, with modest impact on neurofascin 186. We also show that ankyrin R and βI spectrin are not sufficient to prevent nodal disorganization after AnkG ablation. Additionally, nodal disorganization in both early and late AnkG mutants is accompanied by axonal pathology and neurological dysfunction. Together, our results suggest that AnkG plays an indispensable role in the maturation and long-term stabilization of the newly assembled nodal complex, and that loss of AnkG after nodal stabilization does not lead to rapid nodal disassembly but to loss of specific nodal components in a time-dependent manner.SIGNIFICANCE STATEMENT Nodes of Ranvier are the myelin-free gaps along myelinated axons that allow fast communication between neurons and their target cells by propagating action potentials in a saltatory manner. The cytoskeletal scaffolding protein ankyrin G (AnkG) has been thought to play an important role in node formation; however, its precise role in nodal assembly, stability, and maintenance is still not clear. By using spatiotemporal ablation of AnkG, we report its differential role in nodal maturation and stabilization. We show that early AnkG-deficient nodes fail to mature and undergo rapid destabilization. In contrast, nodes that assemble with AnkG are much more stable and undergo gradual disintegration with sequential loss of nodal components in the absence of AnkG.
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Colombelli C, Palmisano M, Eshed-Eisenbach Y, Zambroni D, Pavoni E, Ferri C, Saccucci S, Nicole S, Soininen R, McKee KK, Yurchenco PD, Peles E, Wrabetz L, Feltri ML. Perlecan is recruited by dystroglycan to nodes of Ranvier and binds the clustering molecule gliomedin. J Cell Biol 2015; 208:313-29. [PMID: 25646087 PMCID: PMC4315246 DOI: 10.1083/jcb.201403111] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 12/18/2014] [Indexed: 01/09/2023] Open
Abstract
Fast neural conduction requires accumulation of Na(+) channels at nodes of Ranvier. Dedicated adhesion molecules on myelinating cells and axons govern node organization. Among those, specific laminins and dystroglycan complexes contribute to Na(+) channel clustering at peripheral nodes by unknown mechanisms. We show that in addition to facing the basal lamina, dystroglycan is found near the nodal matrix around axons, binds matrix components, and participates in initial events of nodogenesis. We identify the dystroglycan-ligand perlecan as a novel nodal component and show that dystroglycan is required for the selective accumulation of perlecan at nodes. Perlecan binds the clustering molecule gliomedin and enhances clustering of node of Ranvier components. These data show that proteoglycans have specific roles in peripheral nodes and indicate that peripheral and central axons use similar strategies but different molecules to form nodes of Ranvier. Further, our data indicate that dystroglycan binds free matrix that is not organized in a basal lamina.
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Affiliation(s)
- Cristina Colombelli
- Division of Genetics and Cell Biology, San Raffaele Hospital, 20132 Milan, Italy
| | - Marilena Palmisano
- Division of Genetics and Cell Biology, San Raffaele Hospital, 20132 Milan, Italy Department of Biochemistry and Department of Neurology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14203 Department of Biochemistry and Department of Neurology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14203
| | - Yael Eshed-Eisenbach
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Desirée Zambroni
- Division of Genetics and Cell Biology, San Raffaele Hospital, 20132 Milan, Italy
| | - Ernesto Pavoni
- Division of Genetics and Cell Biology, San Raffaele Hospital, 20132 Milan, Italy
| | - Cinzia Ferri
- Division of Genetics and Cell Biology, San Raffaele Hospital, 20132 Milan, Italy
| | - Stefania Saccucci
- Division of Genetics and Cell Biology, San Raffaele Hospital, 20132 Milan, Italy
| | - Sophie Nicole
- Institut du Cerveau et de la Moelle Épinière, 75013 Paris, France Institut National de la Santé et de la Recherche Médicale, U1127, 75019 Paris, France Sorbonne Universités, Université Pierre et Marie Currie, UMRS1127, 75252 Paris, France Centre National de la Recherche Scientifique, UMR 7225, 75013 Paris, France
| | - Raija Soininen
- Oulu Center for Cell-Extracellular Matrix Research, University of Oulu, 90014 Oulu, Finland
| | | | | | - Elior Peles
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Lawrence Wrabetz
- Division of Genetics and Cell Biology, San Raffaele Hospital, 20132 Milan, Italy Department of Biochemistry and Department of Neurology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14203 Department of Biochemistry and Department of Neurology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14203
| | - M Laura Feltri
- Division of Genetics and Cell Biology, San Raffaele Hospital, 20132 Milan, Italy Department of Biochemistry and Department of Neurology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14203 Department of Biochemistry and Department of Neurology, Hunter James Kelly Research Institute, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14203
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8
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Ebel J, Beuter S, Wuchter J, Kriebel M, Volkmer H. Organisation and Control of Neuronal Connectivity and Myelination by Cell Adhesion Molecule Neurofascin. ADVANCES IN NEUROBIOLOGY 2014; 8:231-47. [DOI: 10.1007/978-1-4614-8090-7_10] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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9
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Nagaraj K, Mualla R, Hortsch M. The L1 Family of Cell Adhesion Molecules: A Sickening Number of Mutations and Protein Functions. ADVANCES IN NEUROBIOLOGY 2014; 8:195-229. [DOI: 10.1007/978-1-4614-8090-7_9] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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10
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Buttermore ED, Thaxton CL, Bhat MA. Organization and maintenance of molecular domains in myelinated axons. J Neurosci Res 2013; 91:603-22. [PMID: 23404451 DOI: 10.1002/jnr.23197] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 09/19/2012] [Accepted: 11/28/2012] [Indexed: 01/17/2023]
Abstract
Over a century ago, Ramon y Cajal first proposed the idea of a directionality involved in nerve conduction and neuronal communication. Decades later, it was discovered that myelin, produced by glial cells, insulated axons with periodic breaks where nodes of Ranvier (nodes) form to allow for saltatory conduction. In the peripheral nervous system (PNS), Schwann cells are the glia that can either individually myelinate the axon from one neuron or ensheath axons of many neurons. In the central nervous system (CNS), oligodendrocytes are the glia that myelinate axons from different neurons. Review of more recent studies revealed that this myelination created polarized domains adjacent to the nodes. However, the molecular mechanisms responsible for the organization of axonal domains are only now beginning to be elucidated. The molecular domains in myelinated axons include the axon initial segment (AIS), where various ion channels are clustered and action potentials are initiated; the node, where sodium channels are clustered and action potentials are propagated; the paranode, where myelin loops contact with the axolemma; the juxtaparanode (JXP), where delayed-rectifier potassium channels are clustered; and the internode, where myelin is compactly wrapped. Each domain contains a unique subset of proteins critical for the domain's function. However, the roles of these proteins in axonal domain organization are not fully understood. In this review, we highlight recent advances on the molecular nature and functions of some of the components of each axonal domain and their roles in axonal domain organization and maintenance for proper neuronal communication.
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Affiliation(s)
- Elizabeth D Buttermore
- Curriculum in Neurobiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
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11
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Pinceau organization in the cerebellum requires distinct functions of neurofascin in Purkinje and basket neurons during postnatal development. J Neurosci 2012; 32:4724-42. [PMID: 22492029 DOI: 10.1523/jneurosci.5602-11.2012] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Basket axon collaterals synapse onto the Purkinje soma/axon initial segment (AIS) area to form specialized structures, the pinceau, which are critical for normal cerebellar function. Mechanistic details of how the pinceau become organized during cerebellar development are poorly understood. Loss of cytoskeletal adaptor protein Ankyrin G (AnkG) results in mislocalization of the cell adhesion molecule Neurofascin (Nfasc) at the Purkinje AIS and abnormal organization of the pinceau. Loss of Nfasc in adult Purkinje neurons leads to slow disorganization of the Purkinje AIS and pinceau morphology. Here, we used mouse conditional knock-out techniques to show that selective loss of Nfasc, specifically in Purkinje neurons during early development, prevented maturation of the AIS and resulted in loss of Purkinje neuron spontaneous activity and pinceau disorganization. Loss of Nfasc in both Purkinje and basket neurons caused abnormal basket axon collateral branching and targeting to Purkinje soma/AIS, leading to extensive pinceau disorganization, Purkinje neuron degeneration, and severe ataxia. Our studies reveal that the Purkinje Nfasc is required for AIS maturation and for maintaining stable contacts between basket axon terminals and the Purkinje AIS during pinceau organization, while the basket neuron Nfasc in combination with Purkinje Nfasc is required for proper basket axon collateral outgrowth and targeting to Purkinje soma/AIS. Thus, cerebellar pinceau organization requires coordinated mechanisms involving specific Nfasc functions in both Purkinje and basket neurons.
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12
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Labasque M, Devaux JJ, Lévêque C, Faivre-Sarrailh C. Fibronectin type III-like domains of neurofascin-186 protein mediate gliomedin binding and its clustering at the developing nodes of Ranvier. J Biol Chem 2011; 286:42426-42434. [PMID: 22009740 DOI: 10.1074/jbc.m111.266353] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The cell adhesion molecules (CAMs) of the immunoglobulin superfamily (Ig-CAMs) play a crucial role in the organization of the node of Ranvier in myelinated axons. In the peripheral nervous system, Gliomedin (Gldn) secreted by Schwann cell microvilli binds NgCAM-related CAM (NrCAM) and Neurofascin-186 (NF186) and direct the nodal clustering of voltage-gated sodium channels (Nav). NF186 is the single axonal Gldn partner to ensure Nav clustering at nodes, whereas NrCAM is only required in glial cells (Feinberg, K., Eshed-Eisenbach, Y., Frechter, S., Amor, V., Salomon, D., Sabanay, H., Dupree, J. L., Grumet, M., Brophy, P. J., Shrager, P., and Peles, E. (2010) Neuron 65, 490-502). The olfactomedin domain of Gldn is implicated in the interaction with nodal Ig-CAMs. However, the interacting modules of NrCAM or NF186 involved in Gldn association are unknown. Here, we report that fibronectin type III-like (FnIII) domains of both Ig-CAMs mediate their interaction with Gldn in pulldown and cell binding assays. Using surface plasmon resonance assays, we determined that NrCAM and NF186 display similar affinity constant for their association with Gldn (K(D) of 0.9 and 5.7 nm, respectively). We characterized the FnIII domains 1 and 2 of NF186 as interacting modules that ensure association with Gldn. We found that the soluble FnIII domains of NF186 (FnIII-Fc) bind on Schwann cells and inhibit Gldn and Nav clustering at heminodes, the precursors of mature nodes in myelinating cultures. Our study reveals the unexpected importance of FnIII domains of Ig-CAMs in the organization of nodes of Ranvier in peripheral axons. Thus, NF186 utilizes distinct modules to organize the multimeric nodal complex.
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Affiliation(s)
- Marilyne Labasque
- Aix-Marseille Université, Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille, 13344 Marseille, France; CNRS UMR 6231, 13344 Marseille, France
| | - Jérôme J Devaux
- Aix-Marseille Université, Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille, 13344 Marseille, France; CNRS UMR 6231, 13344 Marseille, France
| | | | - Catherine Faivre-Sarrailh
- Aix-Marseille Université, Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille, 13344 Marseille, France; CNRS UMR 6231, 13344 Marseille, France.
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Zonta B, Desmazieres A, Rinaldi A, Tait S, Sherman DL, Nolan MF, Brophy PJ. A critical role for Neurofascin in regulating action potential initiation through maintenance of the axon initial segment. Neuron 2011; 69:945-56. [PMID: 21382554 PMCID: PMC3057015 DOI: 10.1016/j.neuron.2011.02.021] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/06/2011] [Indexed: 12/22/2022]
Abstract
The axon initial segment (AIS) is critical for the initiation and propagation of action potentials. Assembly of the AIS requires interactions between scaffolding molecules and voltage-gated sodium channels, but the molecular mechanisms that stabilize the AIS are poorly understood. The neuronal isoform of Neurofascin, Nfasc186, clusters voltage-gated sodium channels at nodes of Ranvier in myelinated nerves: here, we investigate its role in AIS assembly and stabilization. Inactivation of the Nfasc gene in cerebellar Purkinje cells of adult mice causes rapid loss of Nfasc186 from the AIS but not from nodes of Ranvier. This causes AIS disintegration, impairment of motor learning and the abolition of the spontaneous tonic discharge typical of Purkinje cells. Nevertheless, action potentials with a modified waveform can still be evoked and basic motor abilities remain intact. We propose that Nfasc186 optimizes communication between mature neurons by anchoring the key elements of the adult AIS complex.
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Affiliation(s)
- Barbara Zonta
- Centre for Neuroregeneration, University of Edinburgh, Edinburgh, UK
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14
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Thaxton C, Pillai AM, Pribisko AL, Dupree JL, Bhat MA. Nodes of Ranvier act as barriers to restrict invasion of flanking paranodal domains in myelinated axons. Neuron 2011; 69:244-57. [PMID: 21262464 DOI: 10.1016/j.neuron.2010.12.016] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/12/2010] [Indexed: 11/16/2022]
Abstract
Accumulation of voltage-gated sodium (Na(v)) channels at nodes of Ranvier is paramount for action potential propagation along myelinated fibers, yet the mechanisms governing nodal development, organization, and stabilization remain unresolved. Here, we report that genetic ablation of the neuron-specific isoform of Neurofascin (Nfasc(NF¹⁸⁶)) in vivo results in nodal disorganization, including loss of Na(v) channel and ankyrin-G (AnkG) enrichment at nodes in the peripheral nervous system (PNS) and central nervous system (CNS). Interestingly, the presence of paranodal domains failed to rescue nodal organization in the PNS and the CNS. Most importantly, using ultrastructural analysis, we demonstrate that the paranodal domains invade the nodal space in Nfasc(NF¹⁸⁶) mutant axons and occlude node formation. Our results suggest that Nfasc(NF¹⁸⁶)-dependent assembly of the nodal complex acts as a molecular boundary to restrict the movement of flanking paranodal domains into the nodal area, thereby facilitating the stereotypic axonal domain organization and saltatory conduction along myelinated axons.
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Affiliation(s)
- Courtney Thaxton
- Department of Cell and Molecular Physiology, University of North Carolina School of Medicine, Chapel Hill, Chapel Hill, NC 27599-7545, USA
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15
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Hund TJ, Koval OM, Li J, Wright PJ, Qian L, Snyder JS, Gudmundsson H, Kline CF, Davidson NP, Cardona N, Rasband MN, Anderson ME, Mohler PJ. A β(IV)-spectrin/CaMKII signaling complex is essential for membrane excitability in mice. J Clin Invest 2010; 120:3508-19. [PMID: 20877009 DOI: 10.1172/jci43621] [Citation(s) in RCA: 210] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Accepted: 07/28/2010] [Indexed: 02/04/2023] Open
Abstract
Ion channel function is fundamental to the existence of life. In metazoans, the coordinate activities of voltage-gated Na(+) channels underlie cellular excitability and control neuronal communication, cardiac excitation-contraction coupling, and skeletal muscle function. However, despite decades of research and linkage of Na(+) channel dysfunction with arrhythmia, epilepsy, and myotonia, little progress has been made toward understanding the fundamental processes that regulate this family of proteins. Here, we have identified β(IV)-spectrin as a multifunctional regulatory platform for Na(+) channels in mice. We found that β(IV)-spectrin targeted critical structural and regulatory proteins to excitable membranes in the heart and brain. Animal models harboring mutant β(IV)-spectrin alleles displayed aberrant cellular excitability and whole animal physiology. Moreover, we identified a regulatory mechanism for Na(+) channels, via direct phosphorylation by β(IV)-spectrin-targeted calcium/calmodulin-dependent kinase II (CaMKII). Collectively, our data define an unexpected but indispensable molecular platform that determines membrane excitability in the mouse heart and brain.
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Affiliation(s)
- Thomas J Hund
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA.
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Babiarz J, Kane-Goldsmith N, Basak S, Liu K, Young W, Grumet M. Juvenile and adult olfactory ensheathing cells bundle and myelinate dorsal root ganglion axons in culture. Exp Neurol 2010; 229:72-9. [PMID: 20850435 DOI: 10.1016/j.expneurol.2010.08.028] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 07/29/2010] [Accepted: 08/25/2010] [Indexed: 01/09/2023]
Abstract
Olfactory ensheathing cells (OEC), which normally associate closely with but do not myelinate axons in situ, myelinate axons in the adult mammalian spinal cord. They are of clinical interest as candidate cells for autologous transplantation but the ability of OEC to myelinate axons in vitro has been controversial. To clarify this issue, we isolated OEC from olfactory bulbs (OB) of juvenile and adult rats expressing GFP and analyzed their ability to myelinate axons. Using a well-defined assay for myelination of dorsal root ganglia (DRG) axons in culture, we found that OEC from juvenile pups associated with and then myelinated DRG axons. OEC assembled into bundles with the axons by 1week and required more than a week before myelination on axons was detected. In contrast, rat Schwann cells did not bundle axons and they formed P0(+) and MBP(+) myelin segments after as little as 1week. Most of the OEC in culture exhibited staining for calponin, a marker that was not found on Schwann cells in culture, whereas in both OEC and Schwann cell populations nearly all cells were positive for p75NTR and GFAP. These results confirm previous reports showing only subtle immunological differences between Schwann cells and OEC. Besides differences in the rate of myelination, we detected two additional functional differences in the interactions of OEC and Schwann cells with DRG axons. First, the diameter of OEC generated myelin was greater than for Schwann cell myelin on DRG axons. Second, OEC but not Schwann cells myelinated DRG axons in the absence of vitamin C. OEC isolated from adult OB were also found to bundle and myelinate DRG axons but the latter occurred only after incubation times of at least 3weeks. The results indicate that adult OEC require longer incubation times than juvenile OEC to myelinate axons and suggest that patterns of myelination by OEC and Schwann cells are distinguishable at least on axons in vitro. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.
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Affiliation(s)
- Joanne Babiarz
- W.M. Keck Center for Collaborative Neuroscience, Rutgers, State University of New Jersey, 604 Allison Rd., Piscataway, NJ 08854-8082, USA
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17
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Baines A. Evolution of the spectrin-based membrane skeleton. Transfus Clin Biol 2010; 17:95-103. [DOI: 10.1016/j.tracli.2010.06.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Accepted: 06/23/2010] [Indexed: 12/16/2022]
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18
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In vivo deletion of immunoglobulin domains 5 and 6 in neurofascin (Nfasc) reveals domain-specific requirements in myelinated axons. J Neurosci 2010; 30:4868-76. [PMID: 20371806 DOI: 10.1523/jneurosci.5951-09.2010] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The formation of paranodal axo-glial junctions is critical for the rapid and efficient propagation of nerve impulses. Genetic ablation of genes encoding the critical paranodal proteins Caspr, contactin (Cont), and the myelinating glia-specific isoform of Neurofascin (Nfasc(NF155)) results in the disruption of the paranodal axo-glial junctions, loss of ion channel segregation, and impaired nerve conduction, but the mechanisms regulating their interactions remain elusive. Here, we report that loss of immunoglobulin (Ig) domains 5 and 6 in Nfasc(NF155) in mice phenocopies complete ablation of Nfasc(NF155). The mutant mice lack paranodal septate junctions, resulting in the diffusion of Caspr and Cont from the paranodes, and redistribution of the juxtaparanodal potassium channels toward the nodes. Although critical for Nfasc(NF155) function, we find that Ig5-6 are dispensable for nodal Nfasc(NF186) function. Moreover, in vitro binding assays using Ig5-6 deletion constructs reveal their importance for the association of Nfasc(NF155) with Cont. These findings provide the first molecular evidence demonstrating domain-specific requirements controlling the association of the paranodal tripartite complex in vivo. Our studies further emphasize that in vivo structure/function analysis is necessary to define the unique protein-protein interactions that differentially regulate the functions of Neurofascins during axonal domain organization.
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19
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Kirschbaum K, Kriebel M, Kranz EU, Pötz O, Volkmer H. Analysis of non-canonical fibroblast growth factor receptor 1 (FGFR1) interaction reveals regulatory and activating domains of neurofascin. J Biol Chem 2009; 284:28533-42. [PMID: 19666467 PMCID: PMC2781396 DOI: 10.1074/jbc.m109.004440] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Revised: 07/15/2009] [Indexed: 11/06/2022] Open
Abstract
Fibroblast growth factor receptors (FGFRs) are important for many different mechanisms, including cell migration, proliferation, differentiation, and survival. Here, we show a new link between FGFR1 and the cell adhesion molecule neurofascin, which is important for neurite outgrowth. After overexpression in HEK293 cells, embryonal neurofascin isoform NF166 was able to associate with FGFR1, whereas the adult isoform NF186, differing from NF166 in additional extracellular sequences, was deficient. Pharmacological inhibitors and overexpression of dominant negative components of the FGFR signaling pathway pointed to the activation of FGFR1 after association with neurofascin in neurite outgrowth assays in chick tectal neurons and rat PC12-E2 cells. Both extra- and intracellular domains of embryonal neurofascin isoform NF166 were able to form complexes with FGFR1 independently. However, the cytosolic domain was both necessary and sufficient for the activation of FGFR1. Cytosolic serine residues 56 and 100 were shown to be essential for the neurite outgrowth-promoting activity of neurofascin, whereas both amino acid residues were dispensable for FGFR1 association. In conclusion, the data suggest a neurofascin intracellular domain, which activates FGFR1 for neurite outgrowth, whereas the extracellular domain functions as an additional, regulatory FGFR1 interaction domain in the course of development.
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Affiliation(s)
| | | | | | - Oliver Pötz
- Biochemistry, Naturwissenschaftliches und Medizinisches Institut an der Universität Tübingen, Markwiesenstrasse 55, 72770 Reutlingen, Germany
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20
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Katidou M, Vidaki M, Strigini M, Karagogeos D. The immunoglobulin superfamily of neuronal cell adhesion molecules: lessons from animal models and correlation with human disease. Biotechnol J 2009; 3:1564-80. [PMID: 19072911 DOI: 10.1002/biot.200800281] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Neuronal cell adhesion molecules of the immunoglobulin superfamily (IgCAMs) play a crucial role in the formation of neural circuits at different levels: cell migration, axonal and dendritic targeting as well as synapse formation. Furthermore, in perinatal and adult life, neuronal IgCAMs are required for the formation and maintenance of specialized axonal membrane domains, synaptic plasticity and neurogenesis. Mutations in the corresponding human genes have been correlated to several human neuronal disorders. Perturbing neuronal IgCAMs in animal models provides powerful means to understand the molecular and cellular basis of such human disorders. In this review, we concentrate on the NCAM, L1 and contactin subfamilies of neuronal IgCAMs summarizing recent functional studies from model systems and highlighting their links to disease pathogenesis.
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Affiliation(s)
- Markella Katidou
- University of Crete, Faculty of Medicine, Vassilika Vouton, Heraklion, Crete, Greece
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21
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Susuki K, Rasband MN. Molecular mechanisms of node of Ranvier formation. Curr Opin Cell Biol 2008; 20:616-23. [PMID: 18929652 DOI: 10.1016/j.ceb.2008.09.007] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 09/17/2008] [Accepted: 09/18/2008] [Indexed: 10/21/2022]
Abstract
Action potential propagation along myelinated nerve fibers requires high-density protein complexes that include voltage-gated Na(+) channels at the nodes of Ranvier. Several complementary mechanisms may be involved in node assembly including: (1) interaction of nodal cell adhesion molecules with the extracellular matrix; (2) restriction of membrane protein mobility by paranodal junctions; and (3) stabilization of ion channel clusters by axonal cytoskeletal scaffolds. In the peripheral nervous system, a secreted glial protein at the nodal extracellular matrix interacts with axonal cell adhesion molecules to initiate node formation. In the central nervous system, both glial soluble factors and paranodal axoglial junctions may function in a complementary manner to contribute to node formation.
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Affiliation(s)
- Keiichiro Susuki
- Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston TX 77030, USA
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22
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Cunha SR, Mohler PJ. Obscurin targets ankyrin-B and protein phosphatase 2A to the cardiac M-line. J Biol Chem 2008; 283:31968-80. [PMID: 18782775 DOI: 10.1074/jbc.m806050200] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ankyrin-B targets ion channels and transporters in excitable cells. Dysfunction in ankyrin-B-based pathways results in defects in cardiac physiology. Despite a wealth of knowledge regarding the role of ankyrin-B for cardiac function, little is known regarding the mechanisms underlying ankyrin-B regulation. Moreover, the pathways underlying ankyrin-B targeting in heart are unclear. We report that alternative splicing regulates ankyrin-B localization and function in cardiomyocytes. Specifically, we identify a novel exon (exon 43') in the ankyrin-B regulatory domain that mediates interaction with the Rho-GEF obscurin. Ankyrin-B transcripts harboring exon 43' represent the primary cardiac isoform in human and mouse. We demonstrate that ankyrin-B and obscurin are co-localized at the M-line of myocytes and co-immunoprecipitate from heart. We define the structural requirements for ankyrin-B/obscurin interaction to two motifs in the ankyrin-B regulatory domain and demonstrate that both are critical for obscurin/ankyrin-B interaction. In addition, we demonstrate that interaction with obscurin is required for ankyrin-B M-line targeting. Specifically, both obscurin-binding motifs are required for the M-line targeting of a GFP-ankyrin-B regulatory domain. Moreover, this construct acts as a dominant-negative by competing with endogenous ankyrin-B for obscurin-binding at the M-line, thus providing a powerful new tool to evaluate the function of obscurin/ankyrin-B interactions. With this new tool, we demonstrate that the obscurin/ankyrin-B interaction is critical for recruitment of PP2A to the cardiac M-line. Together, these data provide the first evidence for the molecular basis of ankyrin-B and PP2A targeting and function at the cardiac M-line. Finally, we report that ankyrin-B R1788W is localized adjacent to the ankyrin-B obscurin-binding motif and increases binding activity for obscurin. In summary, our new findings demonstrate that ANK2 is subject to alternative splicing that gives rise to unique polypeptides with diverse roles in cardiac function.
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Affiliation(s)
- Shane R Cunha
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA.
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23
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Zonta B, Tait S, Melrose S, Anderson H, Harroch S, Higginson J, Sherman DL, Brophy PJ. Glial and neuronal isoforms of Neurofascin have distinct roles in the assembly of nodes of Ranvier in the central nervous system. ACTA ACUST UNITED AC 2008; 181:1169-77. [PMID: 18573915 PMCID: PMC2442198 DOI: 10.1083/jcb.200712154] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Rapid nerve impulse conduction in myelinated axons requires the concentration of voltage-gated sodium channels at nodes of Ranvier. Myelin-forming oligodendrocytes in the central nervous system (CNS) induce the clustering of sodium channels into nodal complexes flanked by paranodal axoglial junctions. However, the molecular mechanisms for nodal complex assembly in the CNS are unknown. Two isoforms of Neurofascin, neuronal Nfasc186 and glial Nfasc155, are components of the nodal and paranodal complexes, respectively. Neurofascin-null mice have disrupted nodal and paranodal complexes. We show that transgenic Nfasc186 can rescue the nodal complex when expressed in Nfasc−/− mice in the absence of the Nfasc155–Caspr–Contactin adhesion complex. Reconstitution of the axoglial adhesion complex by expressing transgenic Nfasc155 in oligodendrocytes also rescues the nodal complex independently of Nfasc186. Furthermore, the Nfasc155 adhesion complex has an additional function in promoting the migration of myelinating processes along CNS axons. We propose that glial and neuronal Neurofascins have distinct functions in the assembly of the CNS node of Ranvier.
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Affiliation(s)
- Barbara Zonta
- Centre for Neuroscience Research, Royal Dick School of Veterinary Studies, University of Edinburgh, Edinburgh EH9 1QH, Scotland, UK
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24
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Cusdin FS, Clare JJ, Jackson AP. Trafficking and cellular distribution of voltage-gated sodium channels. Traffic 2007; 9:17-26. [PMID: 17988224 DOI: 10.1111/j.1600-0854.2007.00673.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electrical excitability in cells such as neurons and myocytes depends not only upon the expression of voltage-gated sodium channels but also on their correct targeting within the plasma membrane. Placing sodium channels within a broader cell biological context is beginning to shed new light on a variety of important questions such as the integration of neuronal signaling. Mutations that affect sodium channel trafficking have been shown to underlie several life-threatening conditions including cardiac arrhythmias, revealing an important clinical context to these studies.
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Affiliation(s)
- Fiona S Cusdin
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
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25
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Basak S, Raju K, Babiarz J, Kane-Goldsmith N, Koticha D, Grumet M. Differential expression and functions of neuronal and glial neurofascin isoforms and splice variants during PNS development. Dev Biol 2007; 311:408-22. [PMID: 17936266 DOI: 10.1016/j.ydbio.2007.08.045] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Revised: 08/22/2007] [Accepted: 08/23/2007] [Indexed: 10/22/2022]
Abstract
The cell adhesion molecule neurofascin (NF) has a major neuronal isoform (NF186) containing a mucin-like domain followed by a fifth fibronectin type III repeat while these domains are absent from glial NF155. Neuronal NF isoforms lacking one or both of these domains are expressed transiently in embryonic dorsal root ganglia (DRG). These two domains are co-expressed in mature NF186, which peaks in expression prior to birth and then persists almost exclusively at nodes of Ranvier on myelinated axons. In contrast, glial NF155 is only detected postnatally with the onset of myelination. All these forms of NF bound homophilically and to Schwann cells but only the mature NF186 isoform inhibits cell adhesion, and this activity may be important in formation of the node of Ranvier. Schwann cells deficient in NF155 myelinated DRG axons in a delayed manner and they showed significantly decreased clustering of both NF and Caspr in regions where paranodes normally form. The combined results suggest that NF186 is expressed prenatally on DRG neurons and it may modulate their adhesive interactions with Schwann cells, which express NF155 postnatally and require it for development of axon-glial paranodal junctions.
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Affiliation(s)
- Sayantani Basak
- W. M. Keck Center for Collaborative Neuroscience and Dept. of Cell Biology and Neuroscience, Rutgers University, 604 Allison Rd., Piscataway, NJ 08854-8082, USA
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26
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Dzhashiashvili Y, Zhang Y, Galinska J, Lam I, Grumet M, Salzer JL. Nodes of Ranvier and axon initial segments are ankyrin G-dependent domains that assemble by distinct mechanisms. ACTA ACUST UNITED AC 2007; 177:857-70. [PMID: 17548513 PMCID: PMC2064285 DOI: 10.1083/jcb.200612012] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Axon initial segments (AISs) and nodes of Ranvier are sites of action potential generation and propagation, respectively. Both domains are enriched in sodium channels complexed with adhesion molecules (neurofascin [NF] 186 and NrCAM) and cytoskeletal proteins (ankyrin G and βIV spectrin). We show that the AIS and peripheral nervous system (PNS) nodes both require ankyrin G but assemble by distinct mechanisms. The AIS is intrinsically specified; it forms independent of NF186, which is targeted to this site via intracellular interactions that require ankyrin G. In contrast, NF186 is targeted to the node, and independently cleared from the internode, by interactions of its ectodomain with myelinating Schwann cells. NF186 is critical for and initiates PNS node assembly by recruiting ankyrin G, which is required for the localization of sodium channels and the entire nodal complex. Thus, initial segments assemble from the inside out driven by the intrinsic accumulation of ankyrin G, whereas PNS nodes assemble from the outside in, specified by Schwann cells, which direct the NF186-dependent recruitment of ankyrin G.
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Affiliation(s)
- Yulia Dzhashiashvili
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016, USA
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27
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Eshed Y, Feinberg K, Carey DJ, Peles E. Secreted gliomedin is a perinodal matrix component of peripheral nerves. ACTA ACUST UNITED AC 2007; 177:551-62. [PMID: 17485493 PMCID: PMC2064815 DOI: 10.1083/jcb.200612139] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The interaction between gliomedin and the axonodal cell adhesion molecules (CAMs) neurofascin and NrCAM induces the clustering of Na+ channels at the nodes of Ranvier. We define new interactions of gliomedin that are essential for its clustering activity. We show that gliomedin exists as both transmembrane and secreted forms that are generated by proteolytic cleavage of the protein, and that only the latter is detected at the nodes of Ranvier. The secreted extracellular domain of gliomedin binds to Schwann cells and is incorporated into the extracellular matrix (ECM) in a heparin-dependent manner, suggesting the involvement of heparan sulfate proteoglycans (HSPGs). Furthermore, we show that the N-terminal region of gliomedin serves as an oligomerization domain that mediates self-association of the molecule, which is required for its binding to neurofascin and NrCAM. Our results indicate that the deposition of gliomedin multimers at the nodal gap by binding to HSPGs facilitates the clustering of the axonodal CAMs and Na+ channels.
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Affiliation(s)
- Yael Eshed
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot, Israel
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28
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Spiegel I, Adamsky K, Eshed Y, Milo R, Sarig–Nadir O, Horresh I, Scherer SS, Rasband MN, Peles E. A central role for Necl4 (SynCAM4) in Schwann cell-axon interaction and myelination. Nat Neurosci 2007; 10:861-9. [PMID: 17558405 PMCID: PMC2836764 DOI: 10.1038/nn1915] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2007] [Accepted: 05/05/2007] [Indexed: 12/21/2022]
Abstract
Myelination in the peripheral nervous system requires close contact between Schwann cells and the axon, but the underlying molecular basis remains largely unknown. Here we show that cell adhesion molecules (CAMs) of the nectin-like (Necl, also known as SynCAM or Cadm) family mediate Schwann cell-axon interaction during myelination. Necl4 is the main Necl expressed by myelinating Schwann cells and is located along the internodes in direct apposition to Necl1, which is localized on axons. Necl4 serves as the glial binding partner for axonal Necl1, and the interaction between these two CAMs mediates Schwann cell adhesion. The disruption of the interaction between Necl1 and Necl4 by their soluble extracellular domains, or the expression of a dominant-negative Necl4 in Schwann cells, inhibits myelination. These results suggest that Necl proteins are important for mediating axon-glia contact during myelination in peripheral nerves.
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Affiliation(s)
- Ivo Spiegel
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Konstantin Adamsky
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yael Eshed
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ron Milo
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Offra Sarig–Nadir
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ido Horresh
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Steven S. Scherer
- Department of Neurology, University of Pennsylvania Medical School, Philadelphia, PA 19104, USA
| | - Matthew N. Rasband
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06032, USA
| | - Elior Peles
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
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29
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Boiko T, Vakulenko M, Ewers H, Yap CC, Norden C, Winckler B. Ankyrin-dependent and -independent mechanisms orchestrate axonal compartmentalization of L1 family members neurofascin and L1/neuron-glia cell adhesion molecule. J Neurosci 2007; 27:590-603. [PMID: 17234591 PMCID: PMC6672792 DOI: 10.1523/jneurosci.4302-06.2007] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Axonal initial segments (IS) and nodes of Ranvier are functionally important membrane subdomains in which the clustering of electrogenic channels enables action potential initiation and propagation. In addition, the initial segment contributes to neuronal polarity by serving as a diffusion barrier. To study the mechanisms of axonal compartmentalization, we focused on two L1 family of cell adhesion molecules (L1-CAMs) [L1/neuron-glia cell adhesion molecule (L1/NgCAM) and neurofascin (NF)] and two neuronal ankyrins (ankB and ankG). NF and ankG accumulate specifically at the initial segment, whereas L1/NgCAM and ankB are expressed along the entire lengths of axons. We find that L1/NgCAM and NF show distinct modes of steady-state accumulation during axon outgrowth in cultured hippocampal neurons. Despite their different steady-state localizations, both L1/NgCAM and NF show slow diffusion and low detergent extractability specifically in the initial segment but fast diffusion and high detergent extractability in the distal axon. We propose that L1-CAMs do not strongly bind ankB in the distal axon because of spatial regulation of ankyrin affinity by phosphorylation. NF, conversely, is initially enriched in an ankyrin-independent manner in the axon generally and accumulates progressively in the initial segment attributable to preferential binding to ankG. Our results suggest that NF and L1/NgCAM accumulate in the axon by an ankyrin-independent pathway, but retention at the IS requires ankyrin binding.
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Affiliation(s)
- Tatiana Boiko
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia 22908
| | - Max Vakulenko
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia 22908
| | - Helge Ewers
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia 22908
| | - Chan Choo Yap
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia 22908
| | - Caren Norden
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia 22908
| | - Bettina Winckler
- Department of Neuroscience, University of Virginia, Charlottesville, Virginia 22908
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30
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Schafer DP, Rasband MN. Glial regulation of the axonal membrane at nodes of Ranvier. Curr Opin Neurobiol 2006; 16:508-14. [PMID: 16945520 DOI: 10.1016/j.conb.2006.08.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Accepted: 08/23/2006] [Indexed: 11/27/2022]
Abstract
Action potential conduction in myelinated nerve fibers depends on a polarized axonal membrane. Voltage-gated Na(+) and K(+) channels are clustered at nodes of Ranvier and mediate the transmembrane currents necessary for rapid saltatory conduction. Paranodal junctions flank nodes and function as attachment sites for myelin and as paracellular and membrane protein diffusion barriers. Common molecular mechanisms, directed by myelinating glia, are used to establish these axonal membrane domains. Initially, heterophilic interactions between glial and axonal cell adhesion molecules define the locations where nodes or paranodes form. Subsequently, within each domain, axonal cell adhesion molecules are stabilized and retained through interactions with cytoskeletal and scaffolding proteins, including ankyrins and spectrins.
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Affiliation(s)
- Dorothy P Schafer
- Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington CT 06032, USA
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