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Astrocytes as Context for the Involvement of Myelin and Nodes of Ranvier in the Pathophysiology of Depression and Stress-Related Disorders. JOURNAL OF PSYCHIATRY AND BRAIN SCIENCE 2023; 8:e230001. [PMID: 36866235 PMCID: PMC9976698 DOI: 10.20900/jpbs.20230001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
Astrocytes, despite some shared features as glial cells supporting neuronal function in gray and white matter, participate and adapt their morphology and neurochemistry in a plethora of distinct regulatory tasks in specific neural environments. In the white matter, a large proportion of the processes branching from the astrocytes' cell bodies establish contacts with oligodendrocytes and the myelin they form, while the tips of many astrocyte branches closely associate with nodes of Ranvier. Stability of myelin has been shown to greatly depend on astrocyte-to-oligodendrocyte communication, while the integrity of action potentials that regenerate at nodes of Ranvier has been shown to depend on extracellular matrix components heavily contributed by astrocytes. Several lines of evidence are starting to show that in human subjects with affective disorders and in animal models of chronic stress there are significant changes in myelin components, white matter astrocytes and nodes of Ranvier that have direct relevance to connectivity alterations in those disorders. Some of these changes involve the expression of connexins supporting astrocyte-to-oligodendrocyte gap junctions, extracellular matrix components produced by astrocytes around nodes of Ranvier, specific types of astrocyte glutamate transporters, and neurotrophic factors secreted by astrocytes that are involved in the development and plasticity of myelin. Future studies should further examine the mechanisms responsible for those changes in white matter astrocytes, their putative contribution to pathological connectivity in affective disorders, and the possibility of leveraging that knowledge to design new therapies for psychiatric disorders.
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Lillis M, Zaccardi NJ, Heiman MG. Axon-dendrite and apical-basolateral sorting in a single neuron. Genetics 2022; 221:iyac036. [PMID: 35244146 PMCID: PMC9071548 DOI: 10.1093/genetics/iyac036] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 02/18/2022] [Indexed: 11/13/2022] Open
Abstract
Cells are highly organized machines with functionally specialized compartments. For example, membrane proteins are localized to axons or dendrites in neurons and to apical or basolateral surfaces in epithelial cells. Interestingly, many sensory cells-including vertebrate photoreceptors and olfactory neurons-exhibit both neuronal and epithelial features. Here, we show that Caenorhabditis elegans amphid neurons simultaneously exhibit axon-dendrite sorting like a neuron and apical-basolateral sorting like an epithelial cell. The distal ∼5-10 µm of the dendrite is apical, while the remainder of the dendrite, soma, and axon are basolateral. To determine how proteins are sorted among these compartments, we studied the localization of the conserved adhesion molecule SAX-7/L1CAM. Using minimal synthetic transmembrane proteins, we found that the 91-aa cytoplasmic tail of SAX-7 is necessary and sufficient to direct basolateral localization. Basolateral localization can be fully recapitulated using either of 2 short (10-aa or 19-aa) tail sequences that, respectively, resemble dileucine and Tyr-based motifs known to mediate sorting in mammalian epithelia. The Tyr-based motif is conserved in human L1CAM but had not previously been assigned a function. Disrupting key residues in either sequence leads to apical localization, while "improving" them to match epithelial sorting motifs leads to axon-only localization. Indeed, changing only 2 residues in a short motif is sufficient to redirect the protein between apical, basolateral, and axonal localization. Our results demonstrate that axon-dendrite and apical-basolateral sorting pathways can coexist in a single cell, and suggest that subtle changes to short sequence motifs are sufficient to redirect proteins between these pathways.
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Affiliation(s)
- Monique Lillis
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children's Hospital, Boston, MA 02115, USA
| | - Nathan J Zaccardi
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children's Hospital, Boston, MA 02115, USA
| | - Maxwell G Heiman
- Department of Genetics, Blavatnik Institute, Harvard Medical School and Boston Children's Hospital, Boston, MA 02115, USA
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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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Lubetzki C, Sol-Foulon N, Desmazières A. Nodes of Ranvier during development and repair in the CNS. Nat Rev Neurol 2020; 16:426-439. [DOI: 10.1038/s41582-020-0375-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2020] [Indexed: 01/01/2023]
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Accumulation of Neurofascin at Nodes of Ranvier Is Regulated by a Paranodal Switch. J Neurosci 2020; 40:5709-5723. [PMID: 32554548 DOI: 10.1523/jneurosci.0830-19.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 04/29/2020] [Accepted: 06/02/2020] [Indexed: 12/18/2022] Open
Abstract
The paranodal junctions flank mature nodes of Ranvier and provide a barrier between ion channels at the nodes and juxtaparanodes. These junctions also promote node assembly and maintenance by mechanisms that are poorly understood. Here, we examine their role in the accumulation of NF186, a key adhesion molecule of PNS and CNS nodes. We previously showed that NF186 is initially targeted/accumulates via its ectodomain to forming PNS (hemi)nodes by diffusion trapping, whereas it is later targeted to mature nodes by a transport-dependent mechanism mediated by its cytoplasmic segment. To address the role of the paranodes in this switch, we compared accumulation of NF186 ectodomain and cytoplasmic domain constructs in WT versus paranode defective (i.e., Caspr-null) mice. Both pathways are affected in the paranodal mutants. In the PNS of Caspr-null mice, diffusion trapping mediated by the NF186 ectodomain aberrantly persists into adulthood, whereas the cytoplasmic domain/transport-dependent targeting is impaired. In contrast, accumulation of NF186 at CNS nodes does not undergo a switch; it is predominantly targeted to both forming and mature CNS nodes via its cytoplasmic domain and requires intact paranodes. Fluorescence recovery after photobleaching analysis indicates that the paranodes provide a membrane diffusion barrier that normally precludes diffusion of NF186 to nodes. Linkage of paranodal proteins to the underlying cytoskeleton likely contributes to this diffusion barrier based on 4.1B and βII spectrin expression in Caspr-null mice. Together, these results implicate the paranodes as membrane diffusion barriers that regulate targeting to nodes and highlight differences in the assembly of PNS and CNS nodes.SIGNIFICANCE STATEMENT Nodes of Ranvier are essential for effective saltatory conduction along myelinated axons. A major question is how the various axonal proteins that comprise the multimeric nodal complex accumulate at this site. Here we examine how targeting of NF186, a key nodal adhesion molecule, is regulated by the flanking paranodal junctions. We show that the transition from diffusion-trapping to transport-dependent accumulation of NF186 requires the paranodal junctions. We also demonstrate that these junctions are a barrier to diffusion of axonal proteins into the node and highlight differences in PNS and CNS node assembly. These results provide new insights into the mechanism of node assembly and the pathophysiology of neurologic disorders in which impaired paranodal function contributes to clinical disability.
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6
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Dubessy AL, Mazuir E, Rappeneau Q, Ou S, Abi Ghanem C, Piquand K, Aigrot MS, Thétiot M, Desmazières A, Chan E, Fitzgibbon M, Fleming M, Krauss R, Zalc B, Ranscht B, Lubetzki C, Sol-Foulon N. Role of a Contactin multi-molecular complex secreted by oligodendrocytes in nodal protein clustering in the CNS. Glia 2019; 67:2248-2263. [PMID: 31328333 PMCID: PMC6851800 DOI: 10.1002/glia.23681] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 06/12/2019] [Accepted: 06/14/2019] [Indexed: 01/06/2023]
Abstract
The fast and reliable propagation of action potentials along myelinated fibers relies on the clustering of voltage‐gated sodium channels at nodes of Ranvier. Axo‐glial communication is required for assembly of nodal proteins in the central nervous system, yet the underlying mechanisms remain poorly understood. Oligodendrocytes are known to support node of Ranvier assembly through paranodal junction formation. In addition, the formation of early nodal protein clusters (or prenodes) along axons prior to myelination has been reported, and can be induced by oligodendrocyte conditioned medium (OCM). Our recent work on cultured hippocampal neurons showed that OCM‐induced prenodes are associated with an increased conduction velocity (Freeman et al., 2015). We here unravel the nature of the oligodendroglial secreted factors. Mass spectrometry analysis of OCM identified several candidate proteins (i.e., Contactin‐1, ChL1, NrCAM, Noelin2, RPTP/Phosphacan, and Tenascin‐R). We show that Contactin‐1 combined with RPTP/Phosphacan or Tenascin‐R induces clusters of nodal proteins along hippocampal GABAergic axons. Furthermore, Contactin‐1‐immunodepleted OCM or OCM from Cntn1‐null mice display significantly reduced clustering activity, that is restored by addition of soluble Contactin‐1. Altogether, our results identify Contactin‐1 secreted by oligodendrocytes as a novel factor that may influence early steps of nodal sodium channel cluster formation along specific axon populations.
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Affiliation(s)
- Anne-Laure Dubessy
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France.,Assistance Publique-Hôpitaux de Paris, GH Pitié-Salpêtrière, Paris, France
| | - Elisa Mazuir
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
| | - Quentin Rappeneau
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
| | - Sokounthie Ou
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
| | - Charly Abi Ghanem
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Kevin Piquand
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
| | - Marie-Stéphane Aigrot
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
| | - Melina Thétiot
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
| | - Anne Desmazières
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
| | - Eric Chan
- Vertex Pharmaceuticals Incorporated, Boston, Massachusetts
| | | | - Mark Fleming
- Vertex Pharmaceuticals Incorporated, Boston, Massachusetts
| | - Raul Krauss
- Disarm Therapeutics, Cambridge, Massachusetts
| | - Bernard Zalc
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
| | - Barbara Ranscht
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Catherine Lubetzki
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France.,Assistance Publique-Hôpitaux de Paris, GH Pitié-Salpêtrière, Paris, France
| | - Nathalie Sol-Foulon
- Sorbonne Université, Inserm, CNRS, UMR7225, Institut du Cerveau et de la Moelle épinière, ICM, Paris, France
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Harley RJ, Murdy JP, Wang Z, Kelly MC, Ropp TJF, Park SH, Maness PF, Manis PB, Coate TM. Neuronal cell adhesion molecule (NrCAM) is expressed by sensory cells in the cochlea and is necessary for proper cochlear innervation and sensory domain patterning during development. Dev Dyn 2018; 247:934-950. [PMID: 29536590 PMCID: PMC6105381 DOI: 10.1002/dvdy.24629] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 03/06/2018] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND In the cochlea, auditory development depends on precise patterns of innervation by afferent and efferent nerve fibers, as well as a stereotyped arrangement of hair and supporting cells. Neuronal cell adhesion molecule (NrCAM) is a homophilic cell adhesion molecule that controls diverse aspects of nervous system development, but the function of NrCAM in cochlear development is not well understood. RESULTS Throughout cochlear innervation, NrCAM is detectable on spiral ganglion neuron (SGN) afferent and olivocochlear efferent fibers, and on the membranes of developing hair and supporting cells. Neonatal Nrcam-null cochleae show errors in type II SGN fasciculation, reduced efferent innervation, and defects in the stereotyped packing of hair and supporting cells. Nrcam loss also leads to dramatic changes in the profiles of presynaptic afferent and efferent synaptic markers at the time of hearing onset. Despite these numerous developmental defects, Nrcam-null adults do not show defects in auditory acuity, and by postnatal day 21, the developmental deficits in ribbon synapse distribution and sensory domain structure appear to have been corrected. CONCLUSIONS NrCAM is expressed by several neural and sensory epithelial subtypes within the developing cochlea, and the loss of Nrcam confers numerous, but nonpermanent, developmental defects in innervation and sensory domain patterning. Developmental Dynamics 247:934-950, 2018. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Randall J. Harley
- Department of Biology, Georgetown University, 37 and O St. NW, Regents Hall 410, Washington, DC 20007, USA
| | - Joseph P. Murdy
- Department of Biology, Georgetown University, 37 and O St. NW, Regents Hall 410, Washington, DC 20007, USA
| | - Zhirong Wang
- Department of Biology, Georgetown University, 37 and O St. NW, Regents Hall 410, Washington, DC 20007, USA
| | - Michael C. Kelly
- Laboratory of Cochlear Development, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 35 Convent Dr., Bethesda, MD 20892, USA
| | - Tessa-Jonne F. Ropp
- Department of Otolaryngology/Head and Neck Surgery, The University of North Carolina at Chapel Hill, B251 Marsico Hall, CB#7070, 125 Mason Farm Rd., Chapel Hill, NC 27599, USA
| | - SeHoon H. Park
- Department of Biology, Georgetown University, 37 and O St. NW, Regents Hall 410, Washington, DC 20007, USA
| | - Patricia F. Maness
- Department of Biochemistry and Biophysics, The University of North Carolina School of Medicine, 120 Mason Farm Rd., suite 3020, CB#7260, Chapel Hill, NC 27599, USA
| | - Paul B. Manis
- Department of Otolaryngology/Head and Neck Surgery and Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, B027 Marsico Hall, CB#7070. 125 Mason Farm Rd., Chapel Hill, NC 27599
| | - Thomas M. Coate
- Department of Biology, Georgetown University, 37 and O St. NW, Regents Hall 410, Washington, DC 20007, USA
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8
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O'Hare Doig RL, Chiha W, Giacci MK, Yates NJ, Bartlett CA, Smith NM, Hodgetts SI, Harvey AR, Fitzgerald M. Specific ion channels contribute to key elements of pathology during secondary degeneration following neurotrauma. BMC Neurosci 2017; 18:62. [PMID: 28806920 PMCID: PMC5557315 DOI: 10.1186/s12868-017-0380-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 08/05/2017] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Following partial injury to the central nervous system, cells beyond the initial injury site undergo secondary degeneration, exacerbating loss of neurons, compact myelin and function. Changes in Ca2+ flux are associated with metabolic and structural changes, but it is not yet clear how flux through specific ion channels contributes to the various pathologies. Here, partial optic nerve transection in adult female rats was used to model secondary degeneration. Treatment with combinations of three ion channel inhibitors was used as a tool to investigate which elements of oxidative and structural damage related to long term functional outcomes. The inhibitors employed were the voltage gated Ca2+ channel inhibitor Lomerizine (Lom), the Ca2+ permeable AMPA receptor inhibitor YM872 and the P2X7 receptor inhibitor oxATP. RESULTS Following partial optic nerve transection, hyper-phosphorylation of Tau and acetylated tubulin immunoreactivity were increased, and Nogo-A immunoreactivity was decreased, indicating that axonal changes occurred acutely. All combinations of ion channel inhibitors reduced hyper-phosphorylation of Tau and increased Nogo-A immunoreactivity at day 3 after injury. However, only Lom/oxATP or all three inhibitors in combination significantly reduced acetylated tubulin immunoreactivity. Most combinations of ion channel inhibitors were effective in restoring the lengths of the paranode and the paranodal gap, indicative of the length of the node of Ranvier, following injury. However, only all three inhibitors in combination restored to normal Ankyrin G length at the node of Ranvier. Similarly, HNE immunoreactivity and loss of oligodendrocyte precursor cells were only limited by treatment with all three ion channel inhibitors in combination. CONCLUSIONS Data indicate that inhibiting any of a range of ion channels preserves certain elements of axon and node structure and limits some oxidative damage following injury, whereas ionic flux through all three channels must be inhibited to prevent lipid peroxidation and preserve Ankyrin G distribution and OPCs.
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Affiliation(s)
- Ryan L O'Hare Doig
- Experimental and Regenerative Neurosciences, School of Biological Sciences, The University of Western Australia, Crawley, WA, 6009, Australia.,Experimental and Regenerative Neurosciences, School of Human Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Wissam Chiha
- Experimental and Regenerative Neurosciences, School of Biological Sciences, The University of Western Australia, Crawley, WA, 6009, Australia.,Experimental and Regenerative Neurosciences, School of Human Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Marcus K Giacci
- Experimental and Regenerative Neurosciences, School of Biological Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Nathanael J Yates
- Experimental and Regenerative Neurosciences, School of Biological Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Carole A Bartlett
- Experimental and Regenerative Neurosciences, School of Biological Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Nicole M Smith
- Experimental and Regenerative Neurosciences, School of Biological Sciences, The University of Western Australia, Crawley, WA, 6009, Australia.,Experimental and Regenerative Neurosciences, School of Chemistry and Biochemistry, The University of Western Australia, Crawley, WA, 6009, Australia
| | - Stuart I Hodgetts
- Experimental and Regenerative Neurosciences, School of Human Sciences, The University of Western Australia, Crawley, WA, 6009, Australia.,Perron Institute for Neurological and Translational Science, Verdun St, Nedlands, WA, 6009, Australia
| | - Alan R Harvey
- Experimental and Regenerative Neurosciences, School of Human Sciences, The University of Western Australia, Crawley, WA, 6009, Australia.,Perron Institute for Neurological and Translational Science, Verdun St, Nedlands, WA, 6009, Australia
| | - Melinda Fitzgerald
- Experimental and Regenerative Neurosciences, School of Biological Sciences, The University of Western Australia, Crawley, WA, 6009, Australia. .,Curtin Health Innovation Research Institute, Curtin University, Perth, WA, Australia. .,Perron Institute for Neurological and Translational Science, Verdun St, Nedlands, WA, 6009, Australia.
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9
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Xenopus laevis neuronal cell adhesion molecule (nrcam): plasticity of a CAM in the developing nervous system. Dev Genes Evol 2016; 227:61-67. [PMID: 27942869 DOI: 10.1007/s00427-016-0569-9] [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: 08/03/2016] [Accepted: 11/24/2016] [Indexed: 10/20/2022]
Abstract
Neuron-glial-related cell adhesion molecule (NRCAM) is a neuronal cell adhesion molecule of the L1 immunoglobulin superfamily, which plays diverse roles during nervous system development including axon growth and guidance, synapse formation, and formation of the myelinated nerve. Perturbations in NRCAM function cause a wide variety of disorders, which can affect wiring and targeting of neurons, or cause psychiatric disorders as well as cancers through abnormal modulation of signaling events. In the present study, we characterize the Xenopus laevis homolog of nrcam. Expression of Xenopus nrcam is most abundant along the dorsal midline throughout the developing brain and in the outer nuclear layer of the retina.
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10
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Freeman SA, Desmazières A, Fricker D, Lubetzki C, Sol-Foulon N. Mechanisms of sodium channel clustering and its influence on axonal impulse conduction. Cell Mol Life Sci 2016; 73:723-35. [PMID: 26514731 PMCID: PMC4735253 DOI: 10.1007/s00018-015-2081-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 10/21/2015] [Accepted: 10/22/2015] [Indexed: 12/16/2022]
Abstract
The efficient propagation of action potentials along nervous fibers is necessary for animals to interact with the environment with timeliness and precision. Myelination of axons is an essential step to ensure fast action potential propagation by saltatory conduction, a process that requires highly concentrated voltage-gated sodium channels at the nodes of Ranvier. Recent studies suggest that the clustering of sodium channels can influence axonal impulse conduction in both myelinated and unmyelinated fibers, which could have major implications in disease, particularly demyelinating pathology. This comprehensive review summarizes the mechanisms governing the clustering of sodium channels at the peripheral and central nervous system nodes and the specific roles of their clustering in influencing action potential conduction. We further highlight the classical biophysical parameters implicated in conduction timing, followed by a detailed discussion on how sodium channel clustering along unmyelinated axons can impact axonal impulse conduction in both physiological and pathological contexts.
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Affiliation(s)
- Sean A Freeman
- ICM-GHU Pitié-Salpêtrière, Sorbonne Universités UPMC Univ Paris 06, UMR_S 1127, 75013, Paris, France.
- Inserm U1127, 75013, Paris, France.
- CNRS UMR7225, 75013, Paris, France.
| | - Anne Desmazières
- ICM-GHU Pitié-Salpêtrière, Sorbonne Universités UPMC Univ Paris 06, UMR_S 1127, 75013, Paris, France.
- Inserm U1127, 75013, Paris, France.
- CNRS UMR7225, 75013, Paris, France.
| | - Desdemona Fricker
- ICM-GHU Pitié-Salpêtrière, Sorbonne Universités UPMC Univ Paris 06, UMR_S 1127, 75013, Paris, France.
- Inserm U1127, 75013, Paris, France.
- CNRS UMR7225, 75013, Paris, France.
| | - Catherine Lubetzki
- ICM-GHU Pitié-Salpêtrière, Sorbonne Universités UPMC Univ Paris 06, UMR_S 1127, 75013, Paris, France.
- Inserm U1127, 75013, Paris, France.
- CNRS UMR7225, 75013, Paris, France.
- Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, Paris, France.
| | - Nathalie Sol-Foulon
- ICM-GHU Pitié-Salpêtrière, Sorbonne Universités UPMC Univ Paris 06, UMR_S 1127, 75013, Paris, France.
- Inserm U1127, 75013, Paris, France.
- CNRS UMR7225, 75013, Paris, France.
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11
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Acceleration of conduction velocity linked to clustering of nodal components precedes myelination. Proc Natl Acad Sci U S A 2015; 112:E321-8. [PMID: 25561543 DOI: 10.1073/pnas.1419099112] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
High-density accumulation of voltage-gated sodium (Nav) channels at nodes of Ranvier ensures rapid saltatory conduction along myelinated axons. To gain insight into mechanisms of node assembly in the CNS, we focused on early steps of nodal protein clustering. We show in hippocampal cultures that prenodes (i.e., clusters of Nav channels colocalizing with the scaffold protein ankyrinG and nodal cell adhesion molecules) are detected before myelin deposition along axons. These clusters can be induced on purified neurons by addition of oligodendroglial-secreted factor(s), whereas ankyrinG silencing prevents their formation. The Nav isoforms Nav1.1, Nav1.2, and Nav1.6 are detected at prenodes, with Nav1.6 progressively replacing Nav1.2 over time in hippocampal neurons cultured with oligodendrocytes and astrocytes. However, the oligodendrocyte-secreted factor(s) can induce the clustering of Nav1.1 and Nav1.2 but not of Nav1.6 on purified neurons. We observed that prenodes are restricted to GABAergic neurons, whereas clustering of nodal proteins only occurs concomitantly with myelin ensheathment on pyramidal neurons, implying separate mechanisms of assembly among different neuronal subpopulations. To address the functional significance of these early clusters, we used single-axon electrophysiological recordings in vitro and showed that prenode formation is sufficient to accelerate the speed of axonal conduction before myelination. Finally, we provide evidence that prenodal clusters are also detected in vivo before myelination, further strengthening their physiological relevance.
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12
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Amor V, Feinberg K, Eshed-Eisenbach Y, Vainshtein A, Frechter S, Grumet M, Rosenbluth J, Peles E. Long-term maintenance of Na+ channels at nodes of Ranvier depends on glial contact mediated by gliomedin and NrCAM. J Neurosci 2014; 34:5089-98. [PMID: 24719088 PMCID: PMC3983794 DOI: 10.1523/jneurosci.4752-13.2014] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Clustering of Na(+) channels at the nodes of Ranvier is coordinated by myelinating glia. In the peripheral nervous system, axoglial contact at the nodes is mediated by the binding of gliomedin and glial NrCAM to axonal neurofascin 186 (NF186). This interaction is crucial for the initial clustering of Na(+) channels at heminodes. As a result, it is not clear whether continued axon-glial contact at nodes of Ranvier is required to maintain these channels at the nodal axolemma. Here, we report that, in contrast to mice that lack either gliomedin or NrCAM, absence of both molecules (and hence the glial clustering signal) resulted in a gradual loss of Na(+) channels and other axonal components from the nodes, the formation of binary nodes, and dysregulation of nodal gap length. Therefore, these mice exhibit neurological abnormalities and slower nerve conduction. Disintegration of the nodes occurred in an orderly manner, starting with the disappearance of neurofascin 186, followed by the loss of Na(+) channels and ankyrin G, and then βIV spectrin, a sequence that reflects the assembly of nodes during development. Finally, the absence of gliomedin and NrCAM led to the invasion of the outermost layer of the Schwann cell membrane beyond the nodal area and the formation of paranodal-like junctions at the nodal gap. Our results reveal that axon-glial contact mediated by gliomedin, NrCAM, and NF186 not only plays a role in Na(+) channel clustering during development, but also contributes to the long-term maintenance of Na(+) channels at nodes of Ranvier.
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Affiliation(s)
- Veronique Amor
- 1Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Konstantin Feinberg
- 1Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Yael Eshed-Eisenbach
- 1Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Anya Vainshtein
- 1Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Shahar Frechter
- 1Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Martin Grumet
- 2 W.M. Keck Center for Collaborative Neuroscience, Rutgers University, Piscataway, New Jersey 08854; and
| | - Jack Rosenbluth
- 3Department of Neuroscience and Physiology, New York University School of Medicine, New York, New York 10016
| | - Elior Peles
- 1Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel;
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13
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Genetic deletion of Cadm4 results in myelin abnormalities resembling Charcot-Marie-Tooth neuropathy. J Neurosci 2013; 33:10950-61. [PMID: 23825401 DOI: 10.1523/jneurosci.0571-13.2013] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The interaction between myelinating Schwann cells and the axons they ensheath is mediated by cell adhesion molecules of the Cadm/Necl/SynCAM family. This family consists of four members: Cadm4/Necl4 and Cadm1/Necl2 are found in both glia and axons, whereas Cadm2/Necl3 and Cadm3/Necl1 are expressed by sensory and motor neurons. By generating mice lacking each of the Cadm genes, we now demonstrate that Cadm4 plays a role in the establishment of the myelin unit in the peripheral nervous system. Mice lacking Cadm4 (PGK-Cre/Cadm4(fl/fl)), but not Cadm1, Cadm2, or Cadm3, develop focal hypermyelination characterized by tomacula and myelin outfoldings, which are the hallmark of several Charcot-Marie-Tooth neuropathies. The absence of Cadm4 also resulted in abnormal axon-glial contact and redistribution of ion channels along the axon. These neuropathological features were also found in transgenic mice expressing a dominant-negative mutant of Cadm4 lacking its cytoplasmic domain in myelinating glia Tg(mbp-Cadm4dCT), as well as in mice lacking Cadm4 specifically in Schwann cells (DHH-Cre/Cadm4(fl/fl)). Consistent with these abnormalities, both PGK-Cre/Cadm4(fl/fl) and Tg(mbp-Cadm4dCT) mice exhibit impaired motor function and slower nerve conduction velocity. These findings indicate that Cadm4 regulates the growth of the myelin unit and the organization of the underlying axonal membrane.
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Hadas Y, Nitzan N, Furley AJW, Kozlov SV, Klar A. Distinct cis regulatory elements govern the expression of TAG1 in embryonic sensory ganglia and spinal cord. PLoS One 2013; 8:e57960. [PMID: 23469119 PMCID: PMC3582508 DOI: 10.1371/journal.pone.0057960] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 01/29/2013] [Indexed: 01/06/2023] Open
Abstract
Cell fate commitment of spinal progenitor neurons is initiated by long-range, midline-derived, morphogens that regulate an array of transcription factors that, in turn, act sequentially or in parallel to control neuronal differentiation. Included among these are transcription factors that regulate the expression of receptors for guidance cues, thereby determining axonal trajectories. The Ig/FNIII superfamily molecules TAG1/Axonin1/CNTN2 (TAG1) and Neurofascin (Nfasc) are co-expressed in numerous neuronal cell types in the CNS and PNS – for example motor, DRG and interneurons - both promote neurite outgrowth and both are required for the architecture and function of nodes of Ranvier. The genes encoding TAG1 and Nfasc are adjacent in the genome, an arrangement which is evolutionarily conserved. To study the transcriptional network that governs TAG1 and Nfasc expression in spinal motor and commissural neurons, we set out to identify cis elements that regulate their expression. Two evolutionarily conserved DNA modules, one located between the Nfasc and TAG1 genes and the second directly 5′ to the first exon and encompassing the first intron of TAG1, were identified that direct complementary expression to the CNS and PNS, respectively, of the embryonic hindbrain and spinal cord. Sequential deletions and point mutations of the CNS enhancer element revealed a 130bp element containing three conserved E-boxes required for motor neuron expression. In combination, these two elements appear to recapitulate a major part of the pattern of TAG1 expression in the embryonic nervous system.
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Affiliation(s)
- Yoav Hadas
- Dept. of medical neurobiology, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Noa Nitzan
- Dept. of medical neurobiology, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Andrew J. W. Furley
- Department of Biomedical Science, University of Sheffield, Western Bank, Sheffield, United Kingdom
- * E-mail: (AV); (SVK); (AJWF)
| | - Serguei V. Kozlov
- Center for Advanced Preclinical Research, SAIC-Frederick, Inc., Frederick National Laboratory for Cancer Research (FNLCR), Frederick, Maryland, United States of America
- * E-mail: (AV); (SVK); (AJWF)
| | - Avihu Klar
- Dept. of medical neurobiology, IMRIC, Hebrew University-Hadassah Medical School, Jerusalem, Israel
- * E-mail: (AV); (SVK); (AJWF)
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15
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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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Brandao KE, Dell'Acqua ML, Levinson SR. A-kinase anchoring protein 150 expression in a specific subset of TRPV1- and CaV 1.2-positive nociceptive rat dorsal root ganglion neurons. J Comp Neurol 2012; 520:81-99. [PMID: 21674494 PMCID: PMC4807902 DOI: 10.1002/cne.22692] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Modulation of phosphorylation states of ion channels is a critical step in the development of hyperalgesia during inflammation. Modulatory enhancement of channel activity may increase neuronal excitability and affect downstream targets such as gene transcription. The specificity required for such regulation of ion channels quickly occurs via targeting of protein kinases and phosphatases by the scaffolding A-kinase anchoring protein 79/150 (AKAP79/150). AKAP79/150 has been implicated in inflammatory pain by targeting protein kinase A (PKA) and protein kinase C (PKC) to the transient receptor potential vanilloid 1 (TRPV1) channel in peripheral sensory neurons, thus lowering threshold for activation of the channel by multiple inflammatory reagents. However, the expression pattern of AKAP150 in peripheral sensory neurons is unknown. Here we identify the peripheral neuron subtypes that express AKAP150, the subcellular distribution of AKAP150, and the potential target ion channels in rat dorsal root ganglion (DRG) slices. We found that AKAP150 is expressed predominantly in a subset of small DRG sensory neurons, where it is localized at the plasma membrane of the soma, axon initial segment, and small fibers. Most of these neurons are peripherin positive and produce C fibers, although a small portion produce Aδ fibers. Furthermore, we demonstrate that AKAP79/150 colocalizes with TRPV1 and Ca(V) 1.2 in the soma and axon initial segment. Thus AKAP150 is expressed in small, nociceptive DRG neurons, where it is targeted to membrane regions and where it may play a role in the modulation of ion channel phosphorylation states required for hyperalgesia.
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Affiliation(s)
- Katherine E Brandao
- Program in Neuroscience, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO 80045, USA
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17
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Sakurai T. The role of NrCAM in neural development and disorders--beyond a simple glue in the brain. Mol Cell Neurosci 2011; 49:351-63. [PMID: 22182708 DOI: 10.1016/j.mcn.2011.12.002] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2011] [Revised: 11/03/2011] [Accepted: 12/02/2011] [Indexed: 12/15/2022] Open
Abstract
NrCAM is a neuronal cell adhesion molecule of the L1 family of immunoglobulin super family. It plays a wide variety of roles in neural development, including cell proliferation and differentiation, axon growth and guidance, synapse formation, and the formation of the myelinated nerve structure. NrCAM functions in cell adhesion and modulates signaling pathways in neural development through multiple molecular interactions with guidance and other factors. Alterations in NrCAM structure/expression are associated with psychiatric disorders such as autism and drug addiction and with tumor progression. The mechanisms of NrCAM participation in development and how these might be perturbed in disorders are reviewed.
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Affiliation(s)
- Takeshi Sakurai
- Medical Innovation Center, Kyoto University Graduate School of Medicine, Japan.
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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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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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20
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Feinberg K, Eshed-Eisenbach Y, Frechter S, Amor V, Salomon D, Sabanay H, Dupree JL, Grumet M, Brophy PJ, Shrager P, Peles E. A glial signal consisting of gliomedin and NrCAM clusters axonal Na+ channels during the formation of nodes of Ranvier. Neuron 2010; 65:490-502. [PMID: 20188654 DOI: 10.1016/j.neuron.2010.02.004] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/03/2010] [Indexed: 11/30/2022]
Abstract
Saltatory conduction requires high-density accumulation of Na(+) channels at the nodes of Ranvier. Nodal Na(+) channel clustering in the peripheral nervous system is regulated by myelinating Schwann cells through unknown mechanisms. During development, Na(+) channels are first clustered at heminodes that border each myelin segment, and later in the mature nodes that are formed by the fusion of two heminodes. Here, we show that initial clustering of Na(+) channels at heminodes requires glial NrCAM and gliomedin, as well as their axonal receptor neurofascin 186 (NF186). We further demonstrate that heminodal clustering coincides with a second, paranodal junction (PNJ)-dependent mechanism that allows Na(+) channels to accumulate at mature nodes by restricting their distribution between two growing myelin internodes. We propose that Schwann cells assemble the nodes of Ranvier by capturing Na(+) channels at heminodes and by constraining their distribution to the nodal gap. Together, these two cooperating mechanisms ensure fast and efficient conduction in myelinated nerves.
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Affiliation(s)
- Konstantin Feinberg
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
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Abstract
In eukaryotic cells, ankyrins serve as adaptor proteins that link membrane proteins to the underlying cytoskeleton. These adaptor proteins form protein complexes consisting of integral membrane proteins, signalling molecules and cytoskeletal components. With their modular architecture and ability to interact with many proteins, ankyrins organize and stabilize these protein networks, thereby establishing the infrastructure of membrane domains with specialized functions. To this end, ankyrin collaborates with a number of proteins including cytoskeletal proteins, cell adhesion molecules and large structural proteins. This review addresses the targeting and stabilization of protein networks related to ankyrin interactions with the cytoskeletal protein β-spectrin, L1-cell adhesion molecules and the large myofibrillar protein obscurin. The significance of these interactions for differential targeting of cardiac proteins and neuronal membrane formation is also presented. Finally, this review concludes with a discussion about ankyrin dysfunction in human diseases such as haemolytic anaemia, cardiac arrhythmia and neurological disorders.
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Affiliation(s)
- Shane R Cunha
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, USA.
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22
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Concurrent Lpin1 and Nrcam mouse mutations result in severe peripheral neuropathy with transitory hindlimb paralysis. J Neurosci 2009; 29:12089-100. [PMID: 19793967 DOI: 10.1523/jneurosci.2029-09.2009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Peripheral neuropathy is a broad category of disorders with a diverse etiology, grouped together by their common pathogenic effect on the peripheral nervous system (PNS). Because of the heterogeneity observed to be responsible for these disorders, a forward genetics method of gene discovery was used to identify additional affected pathways. In this report, we describe the mutant mouse line 20884, generated by N-ethyl-N-nitrosourea mutagenesis, which is characterized by adult-onset transitory hindlimb paralysis. Linkage mapping revealed that two point mutations are responsible for the phenotype: a partial loss-of-function mutation in the gene for phosphatidate phosphatase Lpin1 and a truncation mutation in the gene that encodes the neuronal cell adhesion molecule NrCAM. To investigate how the 20884 Lpin1 and Nrcam mutations interact to produce the paralysis phenotype, the double mutant and both single mutants were analyzed by quantitative behavioral, histological, and electrophysiological means. The Lpin1(20884) mutant and the double mutant are characterized by similar levels of demyelination and aberrant myelin structures. Nevertheless, the double mutant exhibits more severe electrophysiological abnormalities than the Lpin1(20884) mutant. The Nrcam(20884) mutant is characterized by normal sciatic nerve morphology and a mild electrophysiological defect. Comparison of the double mutant phenotype with the two single mutants does not point to an additive relationship between the two defects; rather, the Lpin1(20884) and Nrcam(20884) defects appear to act synergistically to produce the 20884 phenotype. It is proposed that the absence of NrCAM in a demyelinating environment has a deleterious effect, possibly by impairing the process of remyelination.
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23
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Thaxton C, Bhat MA. Myelination and regional domain differentiation of the axon. Results Probl Cell Differ 2009; 48:1-28. [PMID: 19343313 DOI: 10.1007/400_2009_3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
During evolution, as organisms increased in complexity and function, the need for the ensheathment and insulation of axons by glia became vital for faster conductance of action potentials in nerves. Myelination, as the process is termed, facilitates the formation of discrete domains within the axolemma that are enriched in ion channels, and macromolecular complexes consisting of cell adhesion molecules and cytoskeletal regulators. While it is known that glia play a substantial role in the coordination and organization of these domains, the mechanisms involved and signals transduced between the axon and glia, as well as the proteins regulating axo-glial junction formation remain elusive. Emerging evidence has shed light on the processes regulating myelination and domain differentiation, and key molecules have been identified that are required for their assembly and maintenance. This review highlights these recent findings, and relates their significance to domain disorganization as seen in several demyelinating disorders and other neuropathies.
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Affiliation(s)
- Courtney Thaxton
- Department of Cell and Molecular Physiology, Curriculum in Neurobiology, UNC-Neuroscience Center and Neurodevelopmental Disorders Research Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7545, USA
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24
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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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Abstract
PURPOSE OF REVIEW The development of successful myelin repair strategies depends on the detailed knowledge of the cellular and molecular processes underlying demyelination and remyelination in the central nervous system of animal models and in patients with multiple sclerosis (MS). Based on the complexity of the demyelination and remyelination processes, it should be expected that effective therapeutic approaches will require a combination of strategies for immunomodulation, neuroprotection, and myelin replacement. This brief review highlights recent cellular and molecular findings and indicates that future therapeutic strategies to enhance remyelination may also require combinatorial treatment to accomplish. RECENT FINDINGS The relapsing-remitting course of some forms of multiple sclerosis has typically fueled hope for effective repair of multiple sclerosis lesions, if demyelinating activity could be attenuated. Recent findings support the potential of endogenous neural stem cells and progenitor cells to generate remyelinating oligodendrocytes. Importantly, interactions with viable axons and supportive astrocytic responses are required for endogenous immature cells to fulfill their potential remyelinating capacity. SUMMARY The research described here will help in identifying the major obstacles to effective remyelination and potential therapeutic targets to guide development of comprehensive approaches for testing in animal models and eventual treatment of patients with multiple sclerosis.
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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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27
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García-Frigola C, Carreres MI, Vegar C, Mason C, Herrera E. Zic2 promotes axonal divergence at the optic chiasm midline by EphB1-dependent and -independent mechanisms. Development 2008; 135:1833-41. [DOI: 10.1242/dev.020693] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Axons of retinal ganglion cells (RGCs) make a divergent choice at the optic chiasm to cross or avoid the midline in order to project to ipsilateral and contralateral targets, thereby establishing the binocular visual pathway. The zinc-finger transcription factor Zic2 and a member of the Eph family of receptor tyrosine kinases, EphB1, are both essential for proper development of the ipsilateral projection at the mammalian optic chiasm midline. Here, we demonstrate in mouse by functional experiments in vivo that Zic2 is not only required but is also sufficient to change the trajectory of RGC axons from crossed to uncrossed. In addition, our results reveal that this transcription factor regulates the expression of EphB1 in RGCs and also suggest the existence of an additional EphB1-independent pathway controlled by Zic2 that contributes to retinal axon divergence at the midline.
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Affiliation(s)
- Cristina García-Frigola
- Instituto de Neurociencias de Alicante (Consejo Superior de Investigaciones Científicas-Universidad Miguel Hernández, CSIC-UMH). Campus San Juan, Avd. Ramón y Cajal s/n, Alicante 03550, Spain
| | - Maria Isabel Carreres
- Instituto de Neurociencias de Alicante (Consejo Superior de Investigaciones Científicas-Universidad Miguel Hernández, CSIC-UMH). Campus San Juan, Avd. Ramón y Cajal s/n, Alicante 03550, Spain
| | - Celia Vegar
- Instituto de Neurociencias de Alicante (Consejo Superior de Investigaciones Científicas-Universidad Miguel Hernández, CSIC-UMH). Campus San Juan, Avd. Ramón y Cajal s/n, Alicante 03550, Spain
| | - Carol Mason
- Departments of Pathology and Cell Biology, Department of Neuroscience,Columbia University, College of Physicians and Surgeons, 630 W. 168th Street,New York, NY 10032, USA
| | - Eloísa Herrera
- Instituto de Neurociencias de Alicante (Consejo Superior de Investigaciones Científicas-Universidad Miguel Hernández, CSIC-UMH). Campus San Juan, Avd. Ramón y Cajal s/n, Alicante 03550, Spain
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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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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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Cloning and expression of a zebrafish SCN1B ortholog and identification of a species-specific splice variant. BMC Genomics 2007; 8:226. [PMID: 17623064 PMCID: PMC1965480 DOI: 10.1186/1471-2164-8-226] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Accepted: 07/10/2007] [Indexed: 12/03/2022] Open
Abstract
Background Voltage-gated Na+ channel β1 (Scn1b) subunits are multi-functional proteins that play roles in current modulation, channel cell surface expression, cell adhesion, cell migration, and neurite outgrowth. We have shown previously that β1 modulates electrical excitability in vivo using a mouse model. Scn1b null mice exhibit spontaneous seizures and ataxia, slowed action potential conduction, decreased numbers of nodes of Ranvier in myelinated axons, alterations in nodal architecture, and differences in Na+ channel α subunit localization. The early death of these mice at postnatal day 19, however, make them a challenging model system to study. As a first step toward development of an alternative model to investigate the physiological roles of β1 subunits in vivo we cloned two β1-like subunit cDNAs from D. rerio. Results Two β1-like subunit mRNAs from zebrafish, scn1ba_tv1 and scn1ba_tv2, arise from alternative splicing of scn1ba. The deduced amino acid sequences of Scn1ba_tv1 and Scn1ba_tv2 are identical except for their C-terminal domains. The C-terminus of Scn1ba_tv1 contains a tyrosine residue similar to that found to be critical for ankyrin association and Na+ channel modulation in mammalian β1. In contrast, Scn1ba_tv2 contains a unique, species-specific C-terminal domain that does not contain a tyrosine. Immunohistochemical analysis shows that, while the expression patterns of Scn1ba_tv1 and Scn1ba_tv2 overlap in some areas of the brain, retina, spinal cord, and skeletal muscle, only Scn1ba_tv1 is expressed in optic nerve where its staining pattern suggests nodal expression. Both scn1ba splice forms modulate Na+ currents expressed by zebrafish scn8aa, resulting in shifts in channel gating mode, increased current amplitude, negative shifts in the voltage dependence of current activation and inactivation, and increases in the rate of recovery from inactivation, similar to the function of mammalian β1 subunits. In contrast to mammalian β1, however, neither zebrafish subunit produces a complete shift to the fast gating mode and neither subunit produces complete channel inactivation or recovery from inactivation. Conclusion These data add to our understanding of structure-function relationships in Na+ channel β1 subunits and establish zebrafish as an ideal system in which to determine the contribution of scn1ba to electrical excitability in vivo.
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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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32
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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: 155] [Impact Index Per Article: 9.1] [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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33
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Williams SE, Grumet M, Colman DR, Henkemeyer M, Mason CA, Sakurai T. A role for Nr-CAM in the patterning of binocular visual pathways. Neuron 2006; 50:535-47. [PMID: 16701205 DOI: 10.1016/j.neuron.2006.03.037] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2005] [Revised: 02/23/2006] [Accepted: 03/28/2006] [Indexed: 01/06/2023]
Abstract
Retinal ganglion cell (RGC) axons diverge within the optic chiasm to project to opposite sides of the brain. In mouse, contralateral RGCs are distributed throughout the retina, whereas ipsilateral RGCs are restricted to the ventrotemporal crescent (VTC). While repulsive guidance mechanisms play a major role in the formation of the ipsilateral projection, little is known about the contribution of growth-promoting interactions to the formation of binocular visual projections. Here, we show that the cell adhesion molecule Nr-CAM is expressed by RGCs that project contralaterally and is critical for the guidance of late-born RGCs within the VTC. Blocking Nr-CAM function causes an increase in the size of the ipsilateral projection and reduces neurite outgrowth on chiasm cells in an age- and region-specific manner. Finally, we demonstrate that EphB1/ephrin-B2-mediated repulsion and Nr-CAM-mediated attraction comprise distinct molecular programs that each contributes to the proper formation of binocular visual pathways.
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Affiliation(s)
- Scott E Williams
- Center for Neurobiology and Behavior and Department of Pathology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA
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34
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Koticha D, Maurel P, Zanazzi G, Kane-Goldsmith N, Basak S, Babiarz J, Salzer J, Grumet M. Neurofascin interactions play a critical role in clustering sodium channels, ankyrin G and beta IV spectrin at peripheral nodes of Ranvier. Dev Biol 2006; 293:1-12. [PMID: 16566914 DOI: 10.1016/j.ydbio.2005.05.028] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2005] [Revised: 05/06/2005] [Accepted: 05/11/2005] [Indexed: 01/06/2023]
Abstract
The Ig cell adhesion molecules (CAM) neurofascin (NF) and Nr-CAM are localized at developing nodes of Ranvier in peripheral myelinated axons prior to clustering of Na+ channels. Different isoforms of NF are expressed on neurons and glia, and NF binding on both cells has been suggested to play roles in node and paranode formation. To clarify the role of NF further, we analyzed effects of NF-Fc fusion proteins in Schwann cell-DRG neuron myelinating cocultures. NF-Fc significantly inhibited nodal clustering of Na+ channels, ankyrin G, and betaIV spectrin, and modestly reduced Caspr clustering at paranodal junctions; it did not significantly affect lengths or numbers of myelin-positive segments, axon initial segments, or accumulations of phosphorylated-ERM proteins in Schwann cell nodal microvilli. NF-Fc binds to Schwann cells but little or no binding to DRG neurons was detected. The results suggest a critical early role for axonal NF in clustering of Na+ channels at nodes of Ranvier via interactions with receptors on Schwann cells.
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Affiliation(s)
- Darshan Koticha
- W. M. Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, 604 Allison Road, Piscataway, NJ 08854-8082, USA
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35
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Occhi S, Zambroni D, Del Carro U, Amadio S, Sirkowski EE, Scherer SS, Campbell KP, Moore SA, Chen ZL, Strickland S, Di Muzio A, Uncini A, Wrabetz L, Feltri ML. Both laminin and Schwann cell dystroglycan are necessary for proper clustering of sodium channels at nodes of Ranvier. J Neurosci 2006; 25:9418-27. [PMID: 16221851 PMCID: PMC1409814 DOI: 10.1523/jneurosci.2068-05.2005] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Nodes of Ranvier are specialized axonal domains, at which voltage-gated sodium channels cluster. How axons cluster molecules in discrete domains is mostly unknown. Both axons and glia probably provide constraining mechanisms that contribute to domain formation. Proper sodium channel clustering in peripheral nerves depends on contact from Schwann cell microvilli, where at least one molecule, gliomedin, binds the sodium channel complex and induces its clustering. Furthermore, mice lacking Schwann cell dystroglycan have aberrant microvilli and poorly clustered sodium channels. Dystroglycan could interact at the basal lamina or at the axonglial surface. Because dystroglycan is a laminin receptor, and laminin 2 mutations [merosin-deficient congenital muscular dystrophy (MDC1A)] cause reduced nerve conduction velocity, we asked whether laminins are involved. Here, we show that the composition of both laminins and the dystroglycan complex at nodes differs from that of internodes. Mice defective in laminin 2 have poorly formed microvilli and abnormal sodium clusters. These abnormalities are similar, albeit less severe, than those of mice lacking dystroglycan. However, mice lacking all Schwann cell laminins show severe nodal abnormalities, suggesting that other laminins compensate for the lack of laminin 2. Thus, although laminins are located at a distance from the axoglial junction, they are required for proper clustering of sodium channels. Laminins, through their specific nodal receptors and cytoskeletal linkages, may participate in the formation of mechanisms that constrain clusters at nodes. Finally, abnormal sodium channel clusters are present in a patient with MDC1A, providing a molecular basis for the reduced nerve conduction velocity in this disorder.
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Affiliation(s)
- Simona Occhi
- Dibit, San Raffaele Scientific Institute, 20132 Milan, Italy
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36
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Pruss T, Kranz EU, Niere M, Volkmer H. A regulated switch of chick neurofascin isoforms modulates ligand recognition and neurite extension. Mol Cell Neurosci 2006; 31:354-65. [PMID: 16314110 DOI: 10.1016/j.mcn.2005.10.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2005] [Revised: 09/30/2005] [Accepted: 10/12/2005] [Indexed: 10/25/2022] Open
Abstract
Neural cell adhesion molecule neurofascin regulates the induction of neurite outgrowth, the establishment of synaptic connectivity and myelination. Neurofascin isoforms are generated by spatially and temporally controlled alternative splicing. Isoform NF166 is predominantly expressed in dorsal root ganglia from embryonal day 5 (E5) to E8, and a further neurofascin isoform NF185 appears at E9. Expression of neurofascin and its binding partner axonin-1 on sensory fibers implies functional interactions for neurite outgrowth. E7 sensory neurons require NF166-axonin-1 interactions for neurite extension, accordingly. The contribution of NF166-axonin-1 interaction for neurite outgrowth decreases in parallel with the appearance of NF185 on sensory neurons at E9. This finding may be explained by (1) alleviated intrinsic capability to use axonin-1 as a cellular receptor and (2) reduced binding of axonin-1 to NF185. Finally, NF166, but not NF185, serves as a cellular receptor for neurite induction via homophilic interactions with a neurofascin substrate.
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Affiliation(s)
- Thomas Pruss
- NMI Naturwissenschaftliches und Medizinisches Institut an der Universität Tübingen, NMI, Markwiesenstr. 55, 72770 Reutlingen, Germany
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37
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Sherman DL, Tait S, Melrose S, Johnson R, Zonta B, Court FA, Macklin WB, Meek S, Smith AJH, Cottrell DF, Brophy PJ. Neurofascins Are Required to Establish Axonal Domains for Saltatory Conduction. Neuron 2005; 48:737-42. [PMID: 16337912 DOI: 10.1016/j.neuron.2005.10.019] [Citation(s) in RCA: 234] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Revised: 09/23/2005] [Accepted: 10/07/2005] [Indexed: 10/25/2022]
Abstract
Voltage-gated sodium channels are concentrated in myelinated nerves at the nodes of Ranvier flanked by paranodal axoglial junctions. Establishment of these essential nodal and paranodal domains is determined by myelin-forming glia, but the mechanisms are not clear. Here, we show that two isoforms of Neurofascin, Nfasc155 in glia and Nfasc186 in neurons, are required for the assembly of these specialized domains. In Neurofascin-null mice, neither paranodal adhesion junctions nor nodal complexes are formed. Transgenic expression of Nfasc155 in the myelinating glia of Nfasc-/- nerves rescues the axoglial adhesion complex by recruiting the axonal proteins Caspr and Contactin to the paranodes. However, in the absence of Nfasc186, sodium channels remain diffusely distributed along the axon. Our study shows that the two major Neurofascins play essential roles in assembling the nodal and paranodal domains of myelinated axons; therefore, they are essential for the transition to saltatory conduction in developing vertebrate nerves.
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Affiliation(s)
- Diane L Sherman
- Centre for Neuroscience Research, University of Edinburgh, Edinburgh EH9 1QH, United Kingdom
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38
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Koticha D, Babiarz J, Kane-Goldsmith N, Jacob J, Raju K, Grumet M. Cell adhesion and neurite outgrowth are promoted by neurofascin NF155 and inhibited by NF186. Mol Cell Neurosci 2005; 30:137-48. [PMID: 16061393 DOI: 10.1016/j.mcn.2005.06.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2004] [Revised: 06/10/2005] [Accepted: 06/28/2005] [Indexed: 01/06/2023] Open
Abstract
Neurofascin (NF) is a neural cell adhesion molecule in the L1-family containing six Ig domains and multiple fibronectin type III (FnIII) repeats in its extracellular region. NF has many splicing variants and two of these are exemplars that have different cellular patterns of expression during development. NF186, which is expressed on neurons, contains an unusual mucin-like region and NF155, which is expressed on glia, contains a unique FnIII repeat with an RGD motif. Analysis of Fc fusion proteins representing different extracellular regions of NF indicate that NF186 inhibits cell adhesion and neurite outgrowth, and the inhibition is associated with the region containing the mucin-like domain. NF155 promotes neural cell adhesion and neurite outgrowth, and the RGD motif in its third FnIII repeat is critical for cell spreading and neurite outgrowth. The results suggest that different splicing variants of NF expressed on neurons and glia play distinct roles during neural development.
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Affiliation(s)
- Darshan Koticha
- W. M. Keck Center for Collaborative Neuroscience, Rutgers, State University of New Jersey, Piscataway, NJ 08854-8082, USA
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39
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Chahine M, Ziane R, Vijayaragavan K, Okamura Y. Regulation of Na v channels in sensory neurons. Trends Pharmacol Sci 2005; 26:496-502. [PMID: 16125256 DOI: 10.1016/j.tips.2005.08.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2005] [Revised: 07/11/2005] [Accepted: 08/11/2005] [Indexed: 12/22/2022]
Abstract
Voltage-gated Na(+) channels have an essential role in the biophysical properties of nociceptive neurons. Factors that regulate Na(+) channel function are of interest from both pathophysiological and therapeutic perspectives. Increasing evidence indicates that changes in expression or inappropriate modulation of these channels leads to electrical instability of the cell membrane and the inappropriate spontaneous activity that is observed following nerve injury, and that this might contribute to neuropathic pain. The role of Na(v) channels in nociception depends on modulation by factors such as auxiliary beta-subunits, cytoskeletal proteins and the phosphorylation state of neurons. In this review we describe the modulation of Na(v) channels on sensory neurons by auxiliary beta-subunits, protein kinases and cytoskeletal proteins.
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Affiliation(s)
- Mohamed Chahine
- Laval Hospital, Research Centre, Sainte-Foy, Quebec G1V 4G5, Canada.
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40
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Abstract
The evolution of complex nervous systems in vertebrates has been accompanied by, and probably dependent on, the acquisition of the myelin sheath. Although there has been substantial progress in our understanding of the factors that determine glial cell fate, much less is known about the cellular mechanisms that determine how the myelin sheath is extended and stabilized around axons. This review highlights four crucial stages of myelination, namely, the selection of axons and initiation of cell-cell interactions between them and glial cells, the establishment of stable intercellular contact and assembly of the nodes of Ranvier, regulation of myelin thickness and, finally, longitudinal extension of myelin segments in response to the lengthening of axons during postnatal growth.
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Affiliation(s)
- Diane L Sherman
- Centre for Neuroscience Research, University of Edinburgh, Summerhall, Edinburgh EH9 1QH, UK
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41
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Abstract
An enormous literature has been developed on investigations of the growth and guidance of axons during development and after injury. In this review, we provide a guide to this literature as a resource for biomedical investigators. We first review briefly the molecular biology that is known to regulate migration of the growth cone and branching of axonal arbors. We then outline some important fundamental considerations that are important to the modeling of the phenomenology of these guidance effects and of what is known of their underlying internal mechanisms. We conclude by providing some thoughts on the outlook for future biomedical modeling in the field.
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Affiliation(s)
- Susan Maskery
- Biomedical Informatics, Windber Research Institute, Windber, PA 15963, USA.
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42
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Moody WJ, Bosma MM. Ion Channel Development, Spontaneous Activity, and Activity-Dependent Development in Nerve and Muscle Cells. Physiol Rev 2005; 85:883-941. [PMID: 15987798 DOI: 10.1152/physrev.00017.2004] [Citation(s) in RCA: 274] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
At specific stages of development, nerve and muscle cells generate spontaneous electrical activity that is required for normal maturation of intrinsic excitability and synaptic connectivity. The patterns of this spontaneous activity are not simply immature versions of the mature activity, but rather are highly specialized to initiate and control many aspects of neuronal development. The configuration of voltage- and ligand-gated ion channels that are expressed early in development regulate the timing and waveform of this activity. They also regulate Ca2+influx during spontaneous activity, which is the first step in triggering activity-dependent developmental programs. For these reasons, the properties of voltage- and ligand-gated ion channels expressed by developing neurons and muscle cells often differ markedly from those of adult cells. When viewed from this perspective, the reasons for complex patterns of ion channel emergence and regression during development become much clearer.
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Affiliation(s)
- William J Moody
- Department of Biology, University of Washington, Seattle, Washington 98195, USA.
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43
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Eshed Y, Feinberg K, Poliak S, Sabanay H, Sarig-Nadir O, Spiegel I, Bermingham JR, Peles E. Gliomedin Mediates Schwann Cell-Axon Interaction and the Molecular Assembly of the Nodes of Ranvier. Neuron 2005; 47:215-29. [PMID: 16039564 DOI: 10.1016/j.neuron.2005.06.026] [Citation(s) in RCA: 239] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Revised: 05/16/2005] [Accepted: 06/26/2005] [Indexed: 01/06/2023]
Abstract
Accumulation of Na(+) channels at the nodes of Ranvier is a prerequisite for saltatory conduction. In peripheral nerves, clustering of these channels along the axolemma is regulated by myelinating Schwann cells through a yet unknown mechanism. We report the identification of gliomedin, a glial ligand for neurofascin and NrCAM, two axonal immunoglobulin cell adhesion molecules that are associated with Na+ channels at the nodes of Ranvier. Gliomedin is expressed by myelinating Schwann cells and accumulates at the edges of each myelin segment during development, where it aligns with the forming nodes. Eliminating the expression of gliomedin by RNAi, or the addition of a soluble extracellular domain of neurofascin to myelinating cultures, which caused the redistribution of gliomedin along the internodes, abolished node formation. Furthermore, a soluble gliomedin induced nodal-like clusters of Na+ channels in the absence of Schwann cells. We propose that gliomedin provides a glial cue for the formation of peripheral nodes of Ranvier.
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MESH Headings
- Age Factors
- Amino Acid Sequence
- Animals
- Ankyrins/metabolism
- Axons/metabolism
- Blotting, Northern/methods
- Blotting, Western/methods
- Cell Adhesion Molecules/immunology
- Cell Adhesion Molecules/metabolism
- Cell Adhesion Molecules, Neuronal/metabolism
- Cell Compartmentation
- Cells, Cultured
- Chlorocebus aethiops
- Claudins
- Cloning, Molecular/methods
- Cytoskeletal Proteins
- Fluorescent Antibody Technique/methods
- Ganglia, Spinal/metabolism
- Gene Expression Regulation, Developmental
- Humans
- Macromolecular Substances/immunology
- Macromolecular Substances/metabolism
- Membrane Proteins/metabolism
- Microfilament Proteins/metabolism
- Microscopy, Immunoelectron/methods
- Myelin Basic Protein/metabolism
- Myelin-Associated Glycoprotein/metabolism
- Neurofilament Proteins/metabolism
- Phosphoproteins/metabolism
- Protein Binding/physiology
- Protein Structure, Tertiary
- Ranvier's Nodes/metabolism
- Ranvier's Nodes/ultrastructure
- Rats
- Receptors, Peptide/metabolism
- S100 Proteins/metabolism
- Schwann Cells/metabolism
- Schwann Cells/ultrastructure
- Sciatic Nerve/growth & development
- Sciatic Nerve/metabolism
- Sodium Channels/metabolism
- Spectrin/metabolism
- Transfection/methods
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Affiliation(s)
- Yael Eshed
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
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44
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Corfas G, Velardez MO, Ko CP, Ratner N, Peles E. Mechanisms and roles of axon-Schwann cell interactions. J Neurosci 2005; 24:9250-60. [PMID: 15496660 PMCID: PMC6730082 DOI: 10.1523/jneurosci.3649-04.2004] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Gabriel Corfas
- Division of Neuroscience, Children's Hospital, Boston, Massachusetts 02115, USA
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45
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McEwen DP, Isom LL. Heterophilic Interactions of Sodium Channel β1 Subunits with Axonal and Glial Cell Adhesion Molecules. J Biol Chem 2004; 279:52744-52. [PMID: 15466474 DOI: 10.1074/jbc.m405990200] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Voltage-gated sodium channels localize at high density in axon initial segments and nodes of Ranvier in myelinated axons. Sodium channels consist of a pore-forming alpha subunit and at least one beta subunit. beta1 is a member of the immunoglobulin superfamily of cell adhesion molecules and interacts homophilically and heterophilically with contactin and Nf186. In this study, we characterized beta1 interactions with contactin and Nf186 in greater detail and investigated interactions of beta1 with NrCAM, Nf155, and sodium channel beta2 and beta3 subunits. Using Fc fusion proteins and immunocytochemical techniques, we show that beta1 interacts with the fibronectin-like domains of contactin. beta1 also interacts with NrCAM, Nf155, sodium channel beta2, and Nf186 but not with sodium channel beta3. The interaction of the extracellular domains of beta1 and beta2 requires the region 169TEEEGKTDGEGNA181 located in the intracellular domain of beta2. Interaction of beta1 with Nf186 results in increased Nav).2 cell surface density over alpha alone, similar to that shown previously for contactin and beta2. We propose that beta1 is the critical communication link between sodium channels, nodal cell adhesion molecules, and ankyrinG.
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Affiliation(s)
- Dyke P McEwen
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109-0632, USA
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Sima AAF, Zhang W, Li ZG, Murakawa Y, Pierson CR. Molecular alterations underlie nodal and paranodal degeneration in type 1 diabetic neuropathy and are prevented by C-peptide. Diabetes 2004; 53:1556-63. [PMID: 15161761 DOI: 10.2337/diabetes.53.6.1556] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
To explore the molecular abnormalities underlying the degeneration of the node of Ranvier, a characteristic aberration of type 1 diabetic neuropathy, we examined in type 1 BB/Wor and type 2 BBZDR/Wor rats changes in expression of key molecules that make up the nodal and paranodal apparatus of peripheral nerve. Their posttranslational modifications were examined in vitro. Their responsiveness to restored insulin action was examined in type 1 animals replenished with proinsulin C-peptide. In sciatic nerve, the expression of contactin, receptor protein tyrosine phosphatase beta, and the Na(+)-channel beta(1) subunit, paranodal caspr and nodal ankyrin(G) was unaltered in 2-month type 1 diabetic BB/Wor rats but significantly decreased after 8 months of diabetes. These abnormalities were prevented by C-peptide administered to type 1 BB/Wor rats and did not occur in duration- and hyperglycemia-matched type 2 BBZDR/Wor rats. The expression of the alpha-Na(+)-channel subunit was unaltered. In SH-SY5Y cells, only the combination of insulin and C-peptide normalized posttranslational O-linked N-acetylglucosamine modifications and maximized serine phosphorylation of ankyrin(G) and p85 binding to caspr. The beneficial effects of C-peptide resulted in significant normalization of the nerve conduction deficits. These data describe for the first time the progressive molecular aberrations underlying nodal and paranodal degenerative changes in type 1 diabetic neuropathy and demonstrate that they are preventable by insulinomimetic C-peptide.
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Affiliation(s)
- Anders A F Sima
- Wayne State University, Department of Pathology, 540 E. Canfield Avenue, Detroit, MI 48201, USA.
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Abstract
Cell adhesion molecules of the immunoglobulin superfamily (IgSF CAMs) were discovered 25 years ago based on their role in cell-cell adhesion. Ever since, they have played a major role in developmental neuroscience research. The elucidation of IgSF CAM structure and function has been tightly linked to the establishment of new areas of research. Over the years, our view of the role of the IgSF CAMs has changed. First, they were thought to provide "specific glue" segregating subtypes of cells in the nervous system. Soon it became clear that IgSF CAMs can do much more. The focus shifted from simple adhesion to CAM-associated signaling that was shown to be involved in the promotion of axon growth and the regulation of cell migration. From there it was a small step to axon guidance, a field that has been given a lot of attention during the last decade. More recently, the involvement of IgSF CAMs in synapse formation and maturation has been discovered, although this last step in the formation of neural circuits was thought to be the domain of other families of cell adhesion molecules, such as the neuroligins, the neurexins, and the cadherins. Certainly, the most striking discovery in the context of IgSF CAMs has been the diversity of signaling mechanisms that are associated with them. The versatility of signals and their complexity make IgSF CAMs a perfect tool for brain development.
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Affiliation(s)
- E T Stoeckli
- Institute of Zoology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland,
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Suzuki A, Hoshi T, Ishibashi T, Hayashi A, Yamaguchi Y, Baba H. Paranodal axoglial junction is required for the maintenance of the Nav1.6-type sodium channel in the node of Ranvier in the optic nerves but not in peripheral nerve fibers in the sulfatide-deficient mice. Glia 2004; 46:274-83. [PMID: 15048850 DOI: 10.1002/glia.20008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
In myelinated axons, voltage-gated sodium channels specifically cluster at the nodes of Ranvier, while voltage-gated potassium channels are located at the juxtaparanodes. These characteristic localizations are influenced by myelination. During development, Nav1.2 first appears in the predicted nodes during myelination, and Nav1.6 replaces it in the mature nodes. Such replacements may be important physiologically. We examined the influence of the paranodal junction on switching of sodium channel subunits using the sulfatide-deficient mouse. This mutant displayed disruption of paranodal axoglial junctions and altered nodal lengths and channel distributions. The initial switching of Nav1.2 to Nav1.6 occurred in the mutant optic nerves; however, the number of Nav1.2-positive clusters was significantly higher than in wild-type mice. Although no signs of demyelination were observed at least up to 36 weeks of age, sodium channel clusters decreased markedly with age. Interestingly, Nav1.2 stayed in some of the nodal regions, especially where the nodal lengths were elongated, while Nav1.6 tended to remain in the normal-length nodes. The results in the mutant optic nerves suggested that paranodal junction formation may be necessary for complete replacement of nodal Nav1.2 to Nav1.6 during development as well as maintenance of Nav1.6 clusters at the nodes. Such subtype abnormality was not observed in the sciatic nerve, where paranodal disruption was observed. Thus, the paranodal junction significantly influences the retention of Nav1.6 in the node, which is followed by disorganization of nodal structures. However, its importance may differ between the central and peripheral nervous system.
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Affiliation(s)
- Ayaka Suzuki
- Department of Molecular Neurobiology, School of Pharmacy, Tokyo University of Pharmacy and Life Science, Hachioji, Japan
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Abstract
Molecular events involved in Na+ channel clustering at the node of Ranvier have been investigated during early development. NrCAM, an ankyrinG-binding protein, precedes Na+ channels at cluster sites adjacent to the tips of Schwann cell processes. Both Na+ channel and ankyrinG sequestration at developing nodes are delayed in NrCAM null mutants. The action of NrCAM is manifest locally at individual nodes, rather than affecting overall neuronal expression, and is linked to glial interactions. During remyelination, Na+ channel clusters at new nodes are initially labile, and anchoring to the cytoskeleton appears to grow progressively with time. The distance between Na+ channel clusters across remyelinating Schwann cells (nascent internodes) increases markedly from 83 to 274 microm during node formation, arguing against schemes in which the loci of nodes are fixed in advance by the axon. A hypothesis for node formation in which axonal Na+ channels move by lateral diffusion from regions of Schwann cell contact, with clustering dependent on linkage to the cytoskeleton by ankyrinG, is proposed and tested in a computational model. To match experimental measurements, this latter reaction needs fast kinetics, and the early arrival of NrCAM is postulated to contribute to this requirement.
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50
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Abstract
Efficient and rapid propagation of action potentials in myelinated axons depends on the molecular specialization of the nodes of Ranvier. The nodal region is organized into several distinct domains, each of which contains a unique set of ion channels, cell-adhesion molecules and cytoplasmic adaptor proteins. Voltage-gated Na+ channels - which are concentrated at the nodes - are separated from K+ channels - which are clustered at the juxtaparanodal region - by a specialized axoglial contact that is formed between the axon and the myelinating cell at the paranodes. This local differentiation of myelinated axons is tightly regulated by oligodendrocytes and myelinating Schwann cells, and is achieved through complex mechanisms that are used by another specialized cell-cell contact - the synapse.
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Affiliation(s)
- Sebastian Poliak
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot, Israel
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