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Dhanapalaratnam R, Issar T, Poynten AM, Milner KL, Kwai NCG, Krishnan AV. Progression of axonal excitability abnormalities with increasing clinical severity of diabetic peripheral neuropathy. Clin Neurophysiol 2024; 160:12-18. [PMID: 38367309 DOI: 10.1016/j.clinph.2024.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 01/18/2024] [Accepted: 02/05/2024] [Indexed: 02/19/2024]
Abstract
OBJECTIVE Diabetic peripheral neuropathy (DPN) is a frequent complication for persons with type 2 diabetes. Previous studies have failed to demonstrate any significant impact of treatment for DPN. The present study assessed the role of axonal ion channel dysfunction in DPN and explored the hypothesis that there may be a progressive change in ion channel abnormalities that varied with disease stage. METHODS Neurophysiological studies were conducted using axonal excitability techniques, a clinical method of assessing ion channel dysfunction. Studies were conducted in 178 persons with type 2 diabetes, with participants allocated into four groups according to clinical severity of neuropathy, assessed using the Total Neuropathy Grade. RESULTS Analysis of excitability data demonstrated a progressive and stepwise reduction in two parameters that are related to the activity of Kv1.1 channels, namely superexcitability and depolarizing threshold electrotonus at 10-20 ms (p < 0.001), and mathematical modelling of axonal excitability findings supported progressive upregulation of Kv1.1 conductances with increasing greater disease severity. CONCLUSION The findings are consistent with a progressive upregulation of juxtaparanodal Kv1.1 conductances with increasing clinical severity of diabetic peripheral neuropathy. SIGNIFICANCE From a translational perspective, the study suggests that blockade of Kv1.1 channels using 4-aminopyridine derivatives such as fampridine may be a potential treatment for DPN.
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Affiliation(s)
- Roshan Dhanapalaratnam
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Neurology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Tushar Issar
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia
| | - Ann M Poynten
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Kerry-Lee Milner
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Endocrinology, Prince of Wales Hospital, Sydney, NSW 2031, Australia
| | - Natalie C G Kwai
- School of Medical, Indigenous and Health Sciences, University of Wollongong, Australia
| | - Arun V Krishnan
- School of Clinical Medicine, UNSW Sydney, NSW 2031, Australia; Department of Neurology, Prince of Wales Hospital, Sydney, NSW 2031, Australia.
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Lorenzo DN, Edwards RJ, Slavutsky AL. Spectrins: molecular organizers and targets of neurological disorders. Nat Rev Neurosci 2023; 24:195-212. [PMID: 36697767 PMCID: PMC10598481 DOI: 10.1038/s41583-022-00674-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/22/2022] [Indexed: 01/26/2023]
Abstract
Spectrins are cytoskeletal proteins that are expressed ubiquitously in the mammalian nervous system. Pathogenic variants in SPTAN1, SPTBN1, SPTBN2 and SPTBN4, four of the six genes encoding neuronal spectrins, cause neurological disorders. Despite their structural similarity and shared role as molecular organizers at the cell membrane, spectrins vary in expression, subcellular localization and specialization in neurons, and this variation partly underlies non-overlapping disease presentations across spectrinopathies. Here, we summarize recent progress in discerning the local and long-range organization and diverse functions of neuronal spectrins. We provide an overview of functional studies using mouse models, which, together with growing human genetic and clinical data, are helping to illuminate the aetiology of neurological spectrinopathies. These approaches are all critical on the path to plausible therapeutic solutions.
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Affiliation(s)
- Damaris N Lorenzo
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| | - Reginald J Edwards
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Anastasia L Slavutsky
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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Derks MFL, Harlizius B, Lopes MS, Greijdanus-van der Putten SWM, Dibbits B, Laport K, Megens HJ, Groenen MAM. Detection of a Frameshift Deletion in the SPTBN4 Gene Leads to Prevention of Severe Myopathy and Postnatal Mortality in Pigs. Front Genet 2019; 10:1226. [PMID: 31850074 PMCID: PMC6902008 DOI: 10.3389/fgene.2019.01226] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 11/05/2019] [Indexed: 11/26/2022] Open
Abstract
Piglet mortality is a complex phenotype that depends on the environment, selection on piglet health, but also on the interaction between the piglet and sow. However, also monogenic recessive defects contribute to piglet mortality. Selective breeding has decreased overall piglet mortality by improving both mothering abilities and piglet viability. However, variants underlying recessive monogenic defects are usually not well captured within the breeding values, potentially drifting to higher frequency as a result of intense selection or genetic drift. This study describes the identification by whole-genome sequencing of a recessive 16-bp deletion in the SPTBN4 gene causing postnatal mortality in a pig breeding line. The deletion induces a frameshift and a premature stop codon, producing an impaired and truncated spectrin beta non-erythrocytic 4 protein (SPTBN4). Applying medium density single nucleotide polymorphism (SNP) data available for all breeding animals, a pregnant carrier sow sired by a carrier boar was identified. Of the resulting piglets, two confirmed homozygous piglets suffered from severe myopathy, hind-limb paralysis, and tremors. Histopathological examination showed dispersed degeneration and decrease of cross-striations in the dorsal and hind-limb muscle fibers of the affected piglets. Hence, the affected piglets are unable to walk or drink, usually resulting in death within a few hours after birth. This study demonstrates how growing genomic resources in pig breeding can be applied to identify rare syndromes in breeding populations, that are usually poorly documented and often are not even known to have a genetic basis. The study allows to prevent carrier-by-carrier matings, thereby gradually decreasing the frequency of the detrimental allele and avoiding the birth of affected piglets, improving animal welfare. Finally, these "natural knockouts" increase our understanding of gene function within the mammalian clade, and provide a potential model for human disease.
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Affiliation(s)
- Martijn F. L. Derks
- Animal Breeding and Genomics, Wageningen University & Research, Wageningen, Netherlands
| | | | - Marcos S. Lopes
- Topigs Norsvin Research Center, Beuningen, Netherlands
- Topigs Norsvin, Curitiba, Brazil
| | | | - Bert Dibbits
- Animal Breeding and Genomics, Wageningen University & Research, Wageningen, Netherlands
| | - Kimberley Laport
- Animal Breeding and Genomics, Wageningen University & Research, Wageningen, Netherlands
| | - Hendrik-Jan Megens
- Animal Breeding and Genomics, Wageningen University & Research, Wageningen, Netherlands
| | - Martien A. M. Groenen
- Animal Breeding and Genomics, Wageningen University & Research, Wageningen, Netherlands
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Tamadon H, Ghasemi Z, Ghasemi F, Hosseinmardi N, Vatanpour H, Janahmadi M. Characterization of Functional Effects of Two New Active Fractions Isolated From Scorpion Venom on Neuronal Ca 2+ Spikes: A Possible Action on Ca 2+-Dependent Dependent K + Channels. Basic Clin Neurosci 2019. [PMID: 31031893 PMCID: PMC6484188 DOI: 10.32598/bcn.9.10.352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
INTRODUCTION It is a long time that natural toxin research is conducted to unlock the medical potential of toxins. Although venoms-toxins cause pathophysiological conditions, they may be effective to treat several diseases. Since toxins including scorpion toxins target voltage-gated ion channels, they may have profound effects on excitable cells. Therefore, elucidating the cellular and electrophysiological impacts of toxins, particularly scorpion toxins would be helpful in future drug development opportunities. METHODS Intracellular recording was made from F1 cells of Helix aspersa in the presence of calcium Ringer solution in which Na+ and K+ channels were blocked. Then, the modulation of channel function in the presence of extracellular application of F4 and F6 toxins and kaliotoxin (KTX; 50 nM and 1 μM) was examined by assessing the electrophysiological characteristics of calcium spikes. RESULTS The two active toxin fractions, similar to KTX, a known Ca2+-activated K+ channel blocker, reduced the amplitude of AHP, enhanced the firing frequency of calcium spikes and broadened the duration of Ca2+ spikes. Therefore, it might be inferred that these two new fractions induce neuronal hyperexcitability possibly, in part, by blocking calcium-activated potassium channel current. However, this supposition requires further investigation using voltage clamping technique. CONCLUSION These toxin fractions may act as blocker of calcium-activated potassium channels.
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Affiliation(s)
- Hanieh Tamadon
- Department of Physiology, Neuroscience Research Center,
School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Zahra Ghasemi
- Department of Physiology, School of Medicine, Tarbiat
Modares University, Tehran, Iran
| | - Fatemeh Ghasemi
- Department of Physiology, Neuroscience Research Center,
School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Narges Hosseinmardi
- Department of Physiology, Neuroscience Research Center,
School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Hossein Vatanpour
- Department of Toxicology and Pharmacology, School of
Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mahyar Janahmadi
- Department of Physiology, Neuroscience Research Center,
School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Corresponding Author: Mahyar
Janahmadi, PhD.Address: Department of Physiology, Neuroscience Research
Center, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Tel: +98 (21) 22439971
E-mail:;
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Lazarov E, Dannemeyer M, Feulner B, Enderlein J, Gutnick MJ, Wolf F, Neef A. An axon initial segment is required for temporal precision in action potential encoding by neuronal populations. SCIENCE ADVANCES 2018; 4:eaau8621. [PMID: 30498783 PMCID: PMC6261658 DOI: 10.1126/sciadv.aau8621] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Accepted: 10/26/2018] [Indexed: 06/09/2023]
Abstract
Central neurons initiate action potentials (APs) in the axon initial segment (AIS), a compartment characterized by a high concentration of voltage-dependent ion channels and specialized cytoskeletal anchoring proteins arranged in a regular nanoscale pattern. Although the AIS was a key evolutionary innovation in neurons, the functional benefits it confers are not clear. Using a mutation of the AIS cytoskeletal protein βIV-spectrin, we here establish an in vitro model of neurons with a perturbed AIS architecture that retains nanoscale order but loses the ability to maintain a high NaV density. Combining experiments and simulations, we show that a high NaV density in the AIS is not required for axonal AP initiation; it is, however, crucial for a high bandwidth of information encoding and AP timing precision. Our results provide the first experimental demonstration of axonal AP initiation without high axonal channel density and suggest that increasing the bandwidth of the neuronal code and, hence, the computational efficiency of network function, was a major benefit of the evolution of the AIS.
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Affiliation(s)
- Elinor Lazarov
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
- Bernstein Center for Computational Neuroscience, Georg-August-University Göttingen, Am Faßberg 17, 37077 Göttingen, Germany
- University Medical Center Göttingen, Department of Pediatrics and Adolescent Medicine, Division of Pediatric Neurology, Robert Koch Str. 40, 37075 Göttingen, Germany
| | - Melanie Dannemeyer
- Bernstein Center for Computational Neuroscience, Georg-August-University Göttingen, Am Faßberg 17, 37077 Göttingen, Germany
- III. Institute of Physics, Georg-August-University Göttingen, Friedrich Hund Pl. 1, 37077 Göttingen, Germany
| | - Barbara Feulner
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
- Bernstein Center for Computational Neuroscience, Georg-August-University Göttingen, Am Faßberg 17, 37077 Göttingen, Germany
- Max Planck Institute for Experimental Medicine, Hermann Rein St. 3, 37075 Göttingen, Germany
| | - Jörg Enderlein
- Bernstein Center for Computational Neuroscience, Georg-August-University Göttingen, Am Faßberg 17, 37077 Göttingen, Germany
- III. Institute of Physics, Georg-August-University Göttingen, Friedrich Hund Pl. 1, 37077 Göttingen, Germany
| | - Michael J. Gutnick
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel
| | - Fred Wolf
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
- Bernstein Center for Computational Neuroscience, Georg-August-University Göttingen, Am Faßberg 17, 37077 Göttingen, Germany
- Max Planck Institute for Experimental Medicine, Hermann Rein St. 3, 37075 Göttingen, Germany
- Institute for Nonlinear Dynamics, Georg-August-University Göttingen, Friedrich Hund Pl. 1, 37077 Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration, Von-Siebold-Straße 3A, 37075 Göttingen, Germany
- Campus Institute for Dynamics of Biological Networks, Hermann Rein St. 3, 37075 Göttingen, Germany
| | - Andreas Neef
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17, 37077 Göttingen, Germany
- Bernstein Center for Computational Neuroscience, Georg-August-University Göttingen, Am Faßberg 17, 37077 Göttingen, Germany
- Max Planck Institute for Experimental Medicine, Hermann Rein St. 3, 37075 Göttingen, Germany
- Institute for Nonlinear Dynamics, Georg-August-University Göttingen, Friedrich Hund Pl. 1, 37077 Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration, Von-Siebold-Straße 3A, 37075 Göttingen, Germany
- Campus Institute for Dynamics of Biological Networks, Hermann Rein St. 3, 37075 Göttingen, Germany
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Wang CC, Ortiz-González XR, Yum SW, Gill SM, White A, Kelter E, Seaver LH, Lee S, Wiley G, Gaffney PM, Wierenga KJ, Rasband MN. βIV Spectrinopathies Cause Profound Intellectual Disability, Congenital Hypotonia, and Motor Axonal Neuropathy. Am J Hum Genet 2018; 102:1158-1168. [PMID: 29861105 PMCID: PMC5992132 DOI: 10.1016/j.ajhg.2018.04.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 04/24/2018] [Indexed: 12/31/2022] Open
Abstract
βIV spectrin links ankyrinG (AnkG) and clustered ion channels at axon initial segments (AISs) and nodes of Ranvier to the axonal cytoskeleton. Here, we report bi-allelic pathogenic SPTBN4 variants (three homozygous and two compound heterozygous) that cause a severe neurological syndrome that includes congenital hypotonia, intellectual disability, and motor axonal and auditory neuropathy. We introduced these variants into βIV spectrin, expressed these in neurons, and found that 5/7 were loss-of-function variants disrupting AIS localization or abolishing phosphoinositide binding. Nerve biopsies from an individual with a loss-of-function variant had reduced nodal Na+ channels and no nodal KCNQ2 K+ channels. Modeling the disease in mice revealed that although ankyrinR (AnkR) and βI spectrin can cluster Na+ channels and partially compensate for the loss of AnkG and βIV spectrin at nodes of Ranvier, AnkR and βI spectrin cannot cluster KCNQ2- and KCNQ3-subunit-containing K+ channels. Our findings define a class of spectrinopathies and reveal the molecular pathologies causing nervous-system dysfunction.
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Affiliation(s)
- Chih-Chuan Wang
- Department of Neuroscience and Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA
| | - Xilma R Ortiz-González
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Division of Neurology, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Sabrina W Yum
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Division of Neurology, Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Sara M Gill
- Department of Audiology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Amy White
- Department of Audiology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Erin Kelter
- Women and Children's Hospital of Buffalo, Buffalo, NY 14203, USA
| | - Laurie H Seaver
- Spectrum Health Medical Genetics, MSU College of Human Medicine, Department of Pediatrics and Human Development, Grand Rapids, MI 49503, USA
| | - Sansan Lee
- Hawai'i Community Genetics, Honolulu, HI 96814, USA
| | - Graham Wiley
- Division of Genomics and Data Sciences, Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA
| | - Patrick M Gaffney
- Division of Genomics and Data Sciences, Arthritis and Clinical Immunology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA
| | - Klaas J Wierenga
- Department of Pediatrics, Oklahoma University Health Sciences Center, Oklahoma City, OK 73104, USA.
| | - Matthew N Rasband
- Department of Neuroscience and Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA.
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Ghezzi F, Monni L, Nistri A. Functional up-regulation of the M-current by retigabine contrasts hyperexcitability and excitotoxicity on rat hypoglossal motoneurons. J Physiol 2018; 596:2611-2629. [PMID: 29736957 DOI: 10.1113/jp275906] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 04/23/2018] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS Excessive neuronal excitability characterizes several neuropathological conditions, including neurodegenerative diseases such as amyotrophic lateral sclerosis. Hypoglossal motoneurons (HMs), which control tongue muscles, are extremely vulnerable to this disease and undergo damage and death when exposed to an excessive glutamate extracellular concentration that causes excitotoxicity. Our laboratory devised an in vitro model of excitotoxicity obtained by pharmacological blockade of glutamate transporters. In this paradigm, HMs display hyperexcitability, collective bursting and eventually cell death. The results of the present study show that pharmacological up-regulation of a K+ current (M-current), via application of the anti-convulsant retigabine, prevented all hallmarks of HM excitotoxicity, comprising bursting, generation of reactive oxygen species, expression of toxic markers and cell death. ○Our data may have translational value to develop new treatments against neurological diseases by using positive pharmacological modulators of the M-current. ABSTRACT Neuronal hyperexcitability is a symptom characterizing several neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS). In the ALS bulbar form, hypoglossal motoneurons (HMs) are an early target for neurodegeneration because of their high vulnerability to metabolic insults. In recent years, our laboratory has developed an in vitro model of a brainstem slice comprising the hypoglossal nucleus in which HM neurodegeneration is achieved by blocking glutamate clearance with dl-threo-β-benzyloxyaspartate (TBOA), thus leading to delayed excitotoxicity. During this process, HMs display a set of hallmarks such as hyperexcitability (and network bursting), reactive oxygen species (ROS) generation and, finally, cell death. The present study aimed to investigate whether blocking early hyperexcitability and bursting with the anti-convulsant drug retigabine was sufficient to achieve neuroprotection against excitotoxicity. Retigabine is a selective positive allosteric modulator of the M-current (IM ), an endogenous mechanism that neurons (comprising HMs) express to dampen excitability. Retigabine (10 μm; co-applied with TBOA) contrasted ROS generation, release of endogenous toxic factors into the HM cytoplasm and excitotoxicity-induced HM death. Electrophysiological experiments showed that retigabine readily contrasted and arrested bursting evoked by TBOA administration. Because neuronal IM subunits (Kv7.2, Kv7.3 and Kv7.5) were expressed in the hypoglossal nucleus and in functionally connected medullary nuclei, we suggest that they were responsible for the strong reduction in network excitability, a potent phenomenon for achieving neuroprotection against TBOA-induced excitotoxicity. The results of the present study may have translational value for testing novel positive pharmacological modulators of the IM under pathological conditions (including neurodegenerative disorders) characterized by excessive neuronal excitability.
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Affiliation(s)
- Filippo Ghezzi
- Department of Neuroscience, International School for Advanced Studies (SISSA), Trieste, Italy
| | - Laura Monni
- Department of Neuroscience, International School for Advanced Studies (SISSA), Trieste, Italy
| | - Andrea Nistri
- Department of Neuroscience, International School for Advanced Studies (SISSA), Trieste, Italy
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Huang CYM, Rasband MN. Axon initial segments: structure, function, and disease. Ann N Y Acad Sci 2018; 1420:46-61. [PMID: 29749636 DOI: 10.1111/nyas.13718] [Citation(s) in RCA: 106] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 03/13/2018] [Accepted: 03/17/2018] [Indexed: 11/28/2022]
Abstract
The axon initial segment (AIS) is located at the proximal axon and is the site of action potential initiation. This reflects the high density of ion channels found at the AIS. Adaptive changes to the location and length of the AIS can fine-tune the excitability of neurons and modulate plasticity in response to activity. The AIS plays an important role in maintaining neuronal polarity by regulating the trafficking and distribution of proteins that function in somatodendritic or axonal compartments of the neuron. In this review, we provide an overview of the AIS cytoarchitecture, mechanism of assembly, and recent studies revealing mechanisms of differential transport at the AIS that maintain axon and dendrite identities. We further discuss how genetic mutations in AIS components (i.e., ankyrins, ion channels, and spectrins) and injuries may cause neurological disorders.
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Affiliation(s)
| | - Matthew N Rasband
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas
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Garcia-Caballero A, Zhang FX, Hodgkinson V, Huang J, Chen L, Souza IA, Cain S, Kass J, Alles S, Snutch TP, Zamponi GW. T-type calcium channels functionally interact with spectrin (α/β) and ankyrin B. Mol Brain 2018; 11:24. [PMID: 29720258 PMCID: PMC5930937 DOI: 10.1186/s13041-018-0368-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 04/23/2018] [Indexed: 12/17/2022] Open
Abstract
This study describes the functional interaction between the Cav3.1 and Cav3.2 T-type calcium channels and cytoskeletal spectrin (α/β) and ankyrin B proteins. The interactions were identified utilizing a proteomic approach to identify proteins that interact with a conserved negatively charged cytosolic region present in the carboxy-terminus of T-type calcium channels. Deletion of this stretch of amino acids decreased binding of Cav3.1 and Cav3.2 calcium channels to spectrin (α/β) and ankyrin B and notably also reduced T-type whole cell current densities in expression systems. Furthermore, fluorescence recovery after photobleaching analysis of mutant channels lacking the proximal C-terminus region revealed reduced recovery of both Cav3.1 and Cav3.2 mutant channels in hippocampal neurons. Knockdown of spectrin α and ankyrin B decreased the density of endogenous Cav3.2 in hippocampal neurons. These findings reveal spectrin (α/β) / ankyrin B cytoskeletal and signaling proteins as key regulators of T-type calcium channels expressed in the nervous system.
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Affiliation(s)
- Agustin Garcia-Caballero
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada
| | - Fang-Xiong Zhang
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada
| | - Victoria Hodgkinson
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada
| | - Junting Huang
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada
| | - Lina Chen
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada
| | - Ivana A Souza
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada
| | - Stuart Cain
- Michael Smith Laboratories and Djavad Mowafaghian Centre for Brain Health, University of British Colombia, Vancouver, BC, Canada
| | - Jennifer Kass
- Michael Smith Laboratories and Djavad Mowafaghian Centre for Brain Health, University of British Colombia, Vancouver, BC, Canada
| | - Sascha Alles
- Michael Smith Laboratories and Djavad Mowafaghian Centre for Brain Health, University of British Colombia, Vancouver, BC, Canada
| | - Terrance P Snutch
- Michael Smith Laboratories and Djavad Mowafaghian Centre for Brain Health, University of British Colombia, Vancouver, BC, Canada
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr. NW, Calgary, T2N 4N1, Canada.
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Knierim E, Gill E, Seifert F, Morales-Gonzalez S, Unudurthi SD, Hund TJ, Stenzel W, Schuelke M. A recessive mutation in beta-IV-spectrin (SPTBN4) associates with congenital myopathy, neuropathy, and central deafness. Hum Genet 2017; 136:903-910. [PMID: 28540413 DOI: 10.1007/s00439-017-1814-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 05/16/2017] [Indexed: 12/30/2022]
Abstract
Congenital myopathies are a heterogeneous group of muscle disorders that are often genetically determined. Here, we investigated a boy with congenital myopathy, deafness, and neuropathy from a consanguineous Kurdish family by autozygosity mapping and whole exome sequencing. We found a homozygous nonsense mutation in SPTBN4 [c.1597C>T, NM_020971.2; p.(Q533*), NP_066022.2; ClinVar SUB2292235] encoding βIV-spectrin, a non-erythrocytic member of the β-spectrin family. Western blot confirmed the absence of the full-length 288 kDa isoform in muscle and of a specific 72 kDa isoform in fibroblasts. Clinical symptoms of the patient largely corresponded to those described for the quivering mouse, a loss-of-function animal model. Since the human phenotype of βIV-spectrin deficiency included a myopathy with incomplete congenital fiber-type disproportion, we investigated muscle of the quivering (qv4J) mouse and found complete absence of type 1 fibers (fiber-type 2 uniformity). Immunohistology confirmed expression of βIV-spectrin in normal human and mouse muscle at the sarcolemma and its absence in patient and quivering (qv4J) mouse. SPTBN4 mRNA-expression levels in healthy skeletal muscle were found in the range of other regulatory proteins. More patients have to be described to confirm the triad of congenital myopathy, neuropathy and deafness as the defining symptom complex for βIV-spectrin deficiency.
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Affiliation(s)
- Ellen Knierim
- NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany.,Department of Neuropediatrics, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Augustenburger Platz 1, 13353, Berlin, Germany
| | - Esther Gill
- NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Franziska Seifert
- NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Susanne Morales-Gonzalez
- NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Sathya D Unudurthi
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA.,Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH, USA
| | - Thomas J Hund
- The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH, USA.,Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH, USA
| | - Werner Stenzel
- Department of Neuropathology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany
| | - Markus Schuelke
- NeuroCure Clinical Research Center, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Berlin, Germany. .,Department of Neuropediatrics, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health (BIH), Augustenburger Platz 1, 13353, Berlin, Germany.
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Vallat JM, Yuki N, Sekiguchi K, Kokubun N, Oka N, Mathis S, Magy L, Sherman DL, Brophy PJ, Devaux JJ. Paranodal lesions in chronic inflammatory demyelinating polyneuropathy associated with anti-Neurofascin 155 antibodies. Neuromuscul Disord 2017; 27:290-293. [DOI: 10.1016/j.nmd.2016.10.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 10/04/2016] [Accepted: 10/18/2016] [Indexed: 11/29/2022]
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Ultrastructural anatomy of nodes of Ranvier in the peripheral nervous system as revealed by STED microscopy. Proc Natl Acad Sci U S A 2016; 114:E191-E199. [PMID: 28003466 DOI: 10.1073/pnas.1619553114] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We used stimulated emission depletion (STED) superresolution microscopy to analyze the nanoscale organization of 12 glial and axonal proteins at the nodes of Ranvier of teased sciatic nerve fibers. Cytoskeletal proteins of the axon (betaIV spectrin, ankyrin G) exhibit a high degree of one-dimensional longitudinal order at nodal gaps. In contrast, axonal and glial nodal adhesion molecules [neurofascin-186, neuron glial-related cell adhesion molecule (NrCAM)] can arrange in a more complex, 2D hexagonal-like lattice but still feature a ∼190-nm periodicity. Such a lattice-like organization is also found for glial actin. Sodium and potassium channels exhibit a one-dimensional periodicity, with the Nav channels appearing to have a lower degree of organization. At paranodes, both axonal proteins (betaII spectrin, Caspr) and glial proteins (neurofascin-155, ankyrin B) form periodic quasi-one-dimensional arrangements, with a high degree of interdependence between the position of the axonal and the glial proteins. The results indicate the presence of mechanisms that finely align the cytoskeleton of the axon with the one of the Schwann cells, both at paranodal junctions (with myelin loops) and at nodal gaps (with microvilli). Taken together, our observations reveal the importance of the lateral organization of proteins at the nodes of Ranvier and pave the way for deeper investigations of the molecular ultrastructural mechanisms involved in action potential propagation, the formation of the nodes, axon-glia interactions, and demyelination diseases.
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Martin PM, Cifuentes-Diaz C, Devaux J, Garcia M, Bureau J, Thomasseau S, Klingler E, Girault JA, Goutebroze L. Schwannomin-interacting Protein 1 Isoform IQCJ-SCHIP1 Is a Multipartner Ankyrin- and Spectrin-binding Protein Involved in the Organization of Nodes of Ranvier. J Biol Chem 2016; 292:2441-2456. [PMID: 27979964 DOI: 10.1074/jbc.m116.758029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 12/14/2016] [Indexed: 11/06/2022] Open
Abstract
The nodes of Ranvier are essential regions for action potential conduction in myelinated fibers. They are enriched in multimolecular complexes composed of voltage-gated Nav and Kv7 channels associated with cell adhesion molecules. Cytoskeletal proteins ankyrin-G (AnkG) and βIV-spectrin control the organization of these complexes and provide mechanical support to the plasma membrane. IQCJ-SCHIP1 is a cytoplasmic protein present in axon initial segments and nodes of Ranvier. It interacts with AnkG and is absent from nodes and axon initial segments of βIV-spectrin and AnkG mutant mice. Here, we show that IQCJ-SCHIP1 also interacts with βIV-spectrin and Kv7.2/3 channels and self-associates, suggesting a scaffolding role in organizing nodal proteins. IQCJ-SCHIP1 binding requires a βIV-spectrin-specific domain and Kv7 channel 1-5-10 calmodulin-binding motifs. We then investigate the role of IQCJ-SCHIP1 in vivo by studying peripheral myelinated fibers in Schip1 knock-out mutant mice. The major nodal proteins are normally enriched at nodes in these mice, indicating that IQCJ-SCHIP1 is not required for their nodal accumulation. However, morphometric and ultrastructural analyses show an altered shape of nodes similar to that observed in βIV-spectrin mutant mice, revealing that IQCJ-SCHIP1 contributes to nodal membrane-associated cytoskeleton organization, likely through its interactions with the AnkG/βIV-spectrin network. Our work reveals that IQCJ-SCHIP1 interacts with several major nodal proteins, and we suggest that it contributes to a higher organizational level of the AnkG/βIV-spectrin network critical for node integrity.
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Affiliation(s)
- Pierre-Marie Martin
- From INSERM, UMR-S 839, F-75005 Paris.,the Université Pierre et Marie Curie (UPMC)-Sorbonne Universités, UMR-S 839, 75005 Paris.,the Institut du Fer à Moulin, 75005 Paris, and
| | - Carmen Cifuentes-Diaz
- From INSERM, UMR-S 839, F-75005 Paris.,the Université Pierre et Marie Curie (UPMC)-Sorbonne Universités, UMR-S 839, 75005 Paris.,the Institut du Fer à Moulin, 75005 Paris, and
| | - Jérôme Devaux
- the Aix Marseille University, CNRS, CRN2M, 13344 Marseille, France
| | - Marta Garcia
- From INSERM, UMR-S 839, F-75005 Paris.,the Université Pierre et Marie Curie (UPMC)-Sorbonne Universités, UMR-S 839, 75005 Paris.,the Institut du Fer à Moulin, 75005 Paris, and
| | - Jocelyne Bureau
- From INSERM, UMR-S 839, F-75005 Paris.,the Université Pierre et Marie Curie (UPMC)-Sorbonne Universités, UMR-S 839, 75005 Paris.,the Institut du Fer à Moulin, 75005 Paris, and
| | - Sylvie Thomasseau
- From INSERM, UMR-S 839, F-75005 Paris.,the Université Pierre et Marie Curie (UPMC)-Sorbonne Universités, UMR-S 839, 75005 Paris.,the Institut du Fer à Moulin, 75005 Paris, and
| | - Esther Klingler
- From INSERM, UMR-S 839, F-75005 Paris.,the Université Pierre et Marie Curie (UPMC)-Sorbonne Universités, UMR-S 839, 75005 Paris.,the Institut du Fer à Moulin, 75005 Paris, and
| | - Jean-Antoine Girault
- From INSERM, UMR-S 839, F-75005 Paris.,the Université Pierre et Marie Curie (UPMC)-Sorbonne Universités, UMR-S 839, 75005 Paris.,the Institut du Fer à Moulin, 75005 Paris, and
| | - Laurence Goutebroze
- the Université Pierre et Marie Curie (UPMC)-Sorbonne Universités, UMR-S 839, 75005 Paris, .,the Institut du Fer à Moulin, 75005 Paris, and
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15
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Devaux JJ, Miura Y, Fukami Y, Inoue T, Manso C, Belghazi M, Sekiguchi K, Kokubun N, Ichikawa H, Wong AHY, Yuki N. Neurofascin-155 IgG4 in chronic inflammatory demyelinating polyneuropathy. Neurology 2016; 86:800-7. [PMID: 26843559 PMCID: PMC4793783 DOI: 10.1212/wnl.0000000000002418] [Citation(s) in RCA: 179] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 10/01/2015] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE We report the clinical and serologic features of Japanese patients with chronic inflammatory demyelinating polyneuropathy (CIDP) displaying anti-neurofascin-155 (NF155) immunoglobulin G4 (IgG4) antibodies. METHODS In sera from 533 patients with CIDP, anti-NF155 IgG4 antibodies were detected by ELISA. Binding of IgG antibodies to central and peripheral nerves was tested. RESULTS Anti-NF155 IgG4 antibodies were identified in 38 patients (7%) with CIDP, but not in disease controls or normal participants. These patients were younger at onset as compared to 100 anti-NF155-negative patients with CIDP. Twenty-eight patients (74%) presented with sensory ataxia, 16 (42%) showed tremor, 5 (13%) presented with cerebellar ataxia associated with nystagmus, 3 (8%) had demyelinating lesions in the CNS, and 20 of 25 (80%) had poor response to IV immunoglobulin. The clinical features of the antibody-positive patients were statistically more frequent as compared to negative patients with CIDP (n = 100). Anti-NF155 IgG antibodies targeted similarly central and peripheral paranodes. CONCLUSION Anti-NF155 IgG4 antibodies were associated with a subgroup of patients with CIDP showing a younger age at onset, ataxia, tremor, CNS demyelination, and a poor response to IV immunoglobulin. The autoantibodies may serve as a biomarker to improve patients' diagnosis and guide treatments.
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Affiliation(s)
- Jérôme J Devaux
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan
| | - Yumako Miura
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan
| | - Yuki Fukami
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan
| | - Takayuki Inoue
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan
| | - Constance Manso
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan
| | - Maya Belghazi
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan
| | - Kenji Sekiguchi
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan
| | - Norito Kokubun
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan
| | - Hiroo Ichikawa
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan
| | - Anna Hiu Yi Wong
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan
| | - Nobuhiro Yuki
- From Aix-Marseille Université (J.J.D., C.M., M.B.), CNRS, CRN2M-UMR 7286, Marseille, France; Departments of Medicine (Y.M., Y.F., T.I., A.H.Y.W., N.Y.) and Physiology (N.Y.), Yong Loo Lin School of Medicine, National University of Singapore; Brain and Mind Centre (N.Y.), University of Sydney, Australia; Division of Neurology (K.S.), Kobe University Graduate School of Medicine; Department of Neurology (N.K.), Dokkyo Medical University, Tochigi; and Department of Neurology (H.I.), Brain Nerve Center, Showa University Fujigaoka Hospital, Tokyo, Japan.
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Svahn J, Antoine JC, Camdessanché JP. Pathophysiology and biomarkers in chronic inflammatory demyelinating polyradiculoneuropathies. Rev Neurol (Paris) 2014; 170:808-17. [PMID: 25459126 DOI: 10.1016/j.neurol.2014.10.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an acquired dysimmune disorder characterized by strong heterogeneity in terms of clinical manifestations, prognostic and response to treatment. To date, its pathophysiology and potential target antigens are not totally identified despite substantial progress in the understanding of the involved molecular mechanisms. Recent researches in the field have underlined the importance of cell-mediated immunity (lymphocytesT CD4+, CD8+ and macrophages), the breakdown of blood-nerve barrier, a failure of T-cell regulation, and the disruption of nodal and paranodal organization at the node of Ranvier. This last point is possibly mediated by autoantibodies towards axoglial adhesion molecules which may disrupt sodium and potassium voltage-gated channels clustering leading to a failure of saltatory conduction and the apparition of conduction blocks. The purpose of this article is to overview the main pathophysiologic mechanisms and biomarkers identified in CIDP.
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Affiliation(s)
- J Svahn
- Inserm 1028 CNRS UMR5292, équipe neuro-oncologie neuro-inflammation, faculté de médecine Jacques-Lisfranc, 42023 Saint-Étienne cedex 2, France; Université Claude-Bernard Lyon 1, 69003 Lyon, France
| | - J-C Antoine
- Inserm 1028 CNRS UMR5292, équipe neuro-oncologie neuro-inflammation, faculté de médecine Jacques-Lisfranc, 42023 Saint-Étienne cedex 2, France; Service de neurologie, hôpital Nord, CHU de Saint-Étienne, 42055 Saint-Étienne cedex 02, France; Centre référent maladies neuromusculaires rares Rhône-Alpes, CHU de Saint-Étienne, 42055 Saint-Étienne cedex 02, France
| | - J-P Camdessanché
- Inserm 1028 CNRS UMR5292, équipe neuro-oncologie neuro-inflammation, faculté de médecine Jacques-Lisfranc, 42023 Saint-Étienne cedex 2, France; Service de neurologie, hôpital Nord, CHU de Saint-Étienne, 42055 Saint-Étienne cedex 02, France; Centre référent maladies neuromusculaires rares Rhône-Alpes, CHU de Saint-Étienne, 42055 Saint-Étienne cedex 02, France.
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17
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Devaux JJ. [New insights on the organization of the nodes of Ranvier]. Rev Neurol (Paris) 2014; 170:819-24. [PMID: 25459119 DOI: 10.1016/j.neurol.2014.03.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 03/05/2014] [Indexed: 01/06/2023]
Abstract
Myelin plays a crucial role in the rapid and saltatory conduction of the nerve impulse along myelinated axons. In addition, myelin closely regulates the organization of the axonal compartments. This organization involves several complex mechanisms including axo-glial contact, diffusion barriers, the cytoskeletal network, and the extracellular matrix. In peripheral nerves, the axo-glial contact dictates the formation of the nodes and the clustering of the voltage-gated sodium channels (Nav). The axo-glial contact at nodes implicates adhesion molecules expressed by the Schwann cell (gliomedin and NrCAM), which binds a partner, neurofascin-186, on the axonal side. This complex is essential for the recruitment of ankyrin-G, a cytoskeletal scaffolding protein, which binds and concentrates Nav channels at nodes. The paranodal junctions flanking the nodes also play a complementary function in node formation. These junctions are formed by the association of contactin-1/caspr-1/neurofascin-155 and create a diffusion barrier, which traps proteins at the nodes and dampens their diffusion along the internode. In the central nervous system, the mechanisms of node formation are different and the formation of the paranodal junctions precedes the aggregation of Nav channels at nodes. However, node formation can still happen in absence of paranodal junctions in the CNS. One explanation is that NF186 interacts with components of the extracellular matrix around the node and thereby stabilizes the aggregation of nodal proteins. It is likely that many other proteins are also implicated in the signaling pathways that regulate the differentiation of the axonal compartments. The nature and function of these proteins are yet to be identified.
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Affiliation(s)
- J J Devaux
- Centre de recherche en neurobiologie et neurophysiologie de Marseille, faculté de médecine secteur Nord, Aix-Marseille université, CNRS-UMR7286, 51, boulevard Pierre-Dramard, CS80011, 13344 Marseille cedex 15, France.
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18
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Liu W, Devaux JJ. Calmodulin orchestrates the heteromeric assembly and the trafficking of KCNQ2/3 (Kv7.2/3) channels in neurons. Mol Cell Neurosci 2013; 58:40-52. [PMID: 24333508 DOI: 10.1016/j.mcn.2013.12.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 11/25/2013] [Accepted: 12/04/2013] [Indexed: 10/25/2022] Open
Abstract
Mutations in KCNQ2 and KCNQ3 genes are responsible for benign familial neonatal seizures and epileptic encephalopathies. Some of these mutations have been shown to alter the binding of calmodulin (CaM) to specific C-terminal motifs of KCNQ subunits, known as the A and B helices. Here, we show that the mutation I342A in the A helix of KCNQ3 abolishes CaM interaction and strongly decreases the heteromeric association with KCNQ2. The assembly of KCNQ2 with KCNQ3 is essential for their expression at the axon initial segment (AIS). We find that the I342A mutation alters the targeting of KCNQ2/3 subunits at the AIS. However, the traffic of the mutant channels was rescued by provision of exogenous CaM. We show that CaM enhances the heteromeric association of KCNQ2/KCNQ3-I342A subunits by binding to their B helices in a calcium-dependent manner. To further assert the implication of CaM in channel assembly, we inserted a mutation in the second coil-coil domain of KCNQ2 (KCNQ2-L638P) to prevent its heteromerization with KCNQ3. We observe that the expression of a Ca(2+)-insensitive form of CaM favours the assembly of KCNQ3 with KCNQ2-L638P. Our data thus indicate that both apoCaM and Ca(2+)/CaM bind to the C-terminal domains of KCNQ2 and KCNQ3 subunits, and regulate their heteromeric assembly. Hence, CaM may control the composition and distribution of KCNQ channels in neurons.
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Affiliation(s)
- Wenjing Liu
- Aix Marseille Université, CNRS, CRN2M-UMR7286, 13344 Marseille Cedex 15, Marseille, France
| | - Jérôme J Devaux
- Aix Marseille Université, CNRS, CRN2M-UMR7286, 13344 Marseille Cedex 15, Marseille, France.
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Faivre-Sarrailh C, Devaux JJ. Neuro-glial interactions at the nodes of Ranvier: implication in health and diseases. Front Cell Neurosci 2013; 7:196. [PMID: 24194699 PMCID: PMC3810605 DOI: 10.3389/fncel.2013.00196] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 10/08/2013] [Indexed: 01/06/2023] Open
Abstract
Specific cell adhesion molecules (CAMs) are dedicated to the formation of axo-glial contacts at the nodes of Ranvier of myelinated axons. They play a central role in the organization and maintenance of the axonal domains: the node, paranode, and juxtaparanode. In particular, CAMs are essential for the accumulation of voltage-gated sodium channels at the nodal gap that ensures the rapid and saltatory propagation of the action potentials (APs). The mechanisms regulating node formation are distinct in the central and peripheral nervous systems, and recent studies have highlighted the relative contribution of paranodal junctions and nodal extracellular matrix. In addition, CAMs at the juxtaparanodal domains mediate the clustering of voltage-gated potassium channels which regulate the axonal excitability. In several human pathologies, the axo-glial contacts are altered leading to disruption of the nodes of Ranvier or mis-localization of the ion channels along the axons. Node alterations and the failure of APs to propagate correctly from nodes to nodes along the axons both contribute to the disabilities in demyelinating diseases. This article reviews the mechanisms regulating the association of the axo-glial complexes and the role of CAMs in inherited and acquired neurological diseases.
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Force spectroscopy measurements show that cortical neurons exposed to excitotoxic agonists stiffen before showing evidence of bleb damage. PLoS One 2013; 8:e73499. [PMID: 24023686 PMCID: PMC3758302 DOI: 10.1371/journal.pone.0073499] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 07/22/2013] [Indexed: 12/12/2022] Open
Abstract
In ischemic and traumatic brain injury, hyperactivated glutamate (N-methyl-D-aspartic acid, NMDA) and sodium (Nav) channels trigger excitotoxic neuron death. Na+, Ca++ and H2O influx into affected neurons elicits swelling (increased cell volume) and pathological blebbing (disassociation of the plasma membrane’s bilayer from its spectrin-actomyosin matrix). Though usually conflated in injured tissue, cell swelling and blebbing are distinct processes. Around an injury core, salvageable neurons could be mildly swollen without yet having suffered the bleb-type membrane damage that, by rendering channels leaky and pumps dysfunctional, exacerbates the excitotoxic positive feedback spiral. Recognizing when neuronal inflation signifies non-lethal osmotic swelling versus blebbing should further efforts to salvage injury-penumbra neurons. To assess whether the mechanical properties of osmotically-swollen versus excitotoxically-blebbing neurons might be cytomechanically distinguishable, we measured cortical neuron elasticity (gauged via atomic force microscopy (AFM)-based force spectroscopy) upon brief exposure to hypotonicity or to excitotoxic agonists (glutamate and Nav channel activators, NMDA and veratridine). Though unperturbed by solution exchange per se, elasticity increased abruptly with hypotonicity, with NMDA and with veratridine. Neurons then invariably softened towards or below the pre-treatment level, sometimes starting before the washout. The initial channel-mediated stiffening bespeaks an abrupt elevation of hydrostatic pressure linked to NMDA or Nav channel-mediated ion/H2O fluxes, together with increased [Ca++]int-mediated submembrane actomyosin contractility. The subsequent softening to below-control levels is consistent with the onset of a lethal level of bleb damage. These findings indicate that dissection/identification of molecular events during the excitotoxic transition from stiff/swollen to soft/blebbing is warranted and should be feasible.
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Abstract
All cells are influenced by mechanical forces. In the brain, force-generating and load-bearing proteins twist, turn, ratchet, flex, compress, expand and bend to mediate neuronal signalling and plasticity. Although the functions of mechanosensitive proteins have been thoroughly described in classical sensory systems, the effects of endogenous mechanical energy on cellular function in the brain have received less attention, and many working models in neuroscience do not currently integrate principles of cellular mechanics. An understanding of cellular-mechanical concepts is essential to allow the integration of mechanobiology into ongoing studies of brain structure and function.
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Altered distribution of juxtaparanodal kv1.2 subunits mediates peripheral nerve hyperexcitability in type 2 diabetes mellitus. J Neurosci 2012; 32:7493-8. [PMID: 22649228 DOI: 10.1523/jneurosci.0719-12.2012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Peripheral nerve hyperexcitability (PNH) is one of the distal peripheral neuropathy phenotypes often present in patients affected by type 2 diabetes mellitus (T2DM). Through in vivo and ex vivo electrophysiological recordings in db/db mice, a model of T2DM, we observed that, in addition to reduced nerve conduction velocity, db/db mice also develop PNH. By using pharmacological inhibitors, we demonstrated that the PNH is mediated by the decreased activity of K(v)1-channels. In agreement with these data, we observed that the diabetic condition led to a reduced presence of the K(v)1.2-subunits in juxtaparanodal regions of peripheral nerves in db/db mice and in nerve biopsies from T2DM patients. Together, these observations indicate that the T2DM condition leads to potassium channel-mediated PNH, thus identifying them as a potential drug target to treat some of the DPN related symptoms.
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23
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Glasscock E, Qian J, Kole MJ, Noebels JL. Transcompartmental reversal of single fibre hyperexcitability in juxtaparanodal Kv1.1-deficient vagus nerve axons by activation of nodal KCNQ channels. J Physiol 2012; 590:3913-26. [PMID: 22641786 DOI: 10.1113/jphysiol.2012.235606] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Kv1.1 channels cluster at juxtaparanodes of myelinated axons in the vagus nerve, the primary conduit for parasympathetic innervation of the heart. Kcna1-null mice lacking these channels exhibit neurocardiac dysfunction manifested by atropine-sensitive atrioventricular conduction blocks and bradycardia that may culminate in sudden death. To evaluate whether loss of Kv1.1 channels alters electrogenic properties within the nerve, we compared the intrinsic excitability of single myelinated A- and Aδ-axons from excised cervical vagus nerves of young adult Kcna1-null mice and age-matched, wild-type littermate controls. Although action potential shapes and relative refractory periods varied little between genotypes, Kv1.1-deficient large myelinated A-axons showed a fivefold increase in susceptibility to 4-aminopyridine (4-AP)-induced spontaneous ectopic firing. Since the repolarizing currents of juxtaparanodal Kv1 channels and nodal KCNQ potassium channels both act to dampen repetitive activity, we examined whether augmenting nodal KCNQ activation could compensate for Kv1.1 loss and reverse the spontaneous hyperexcitability in Kv1.1-deficient A-axons. Application of the selective KCNQ opener flupirtine raised A-axon firing threshold while profoundly suppressing 4-AP-induced spontaneous firing, demonstrating a functional synergy between the two compartments. We conclude that juxtaparanodal Kv1.1-deficiency causes intrinsic hyperexcitability in large myelinated axons in vagus nerve which could contribute to autonomic dysfunction in Kcna1-null mice, and that KCNQ openers reveal a transcompartmental synergy between Kv1 and KCNQ channels in regulating axonal excitability.
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Affiliation(s)
- Edward Glasscock
- J. L. Noebels: Department of Neurology, Baylor College of Medicine, One Baylor Plaza, NB220, Houston, TX 77030, USA.
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Brunetti O, Imbrici P, Botti FM, Pettorossi VE, D'Adamo MC, Valentino M, Zammit C, Mora M, Gibertini S, Di Giovanni G, Muscat R, Pessia M. Kv1.1 knock-in ataxic mice exhibit spontaneous myokymic activity exacerbated by fatigue, ischemia and low temperature. Neurobiol Dis 2012; 47:310-21. [PMID: 22609489 PMCID: PMC3402927 DOI: 10.1016/j.nbd.2012.05.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 04/18/2012] [Accepted: 05/08/2012] [Indexed: 01/13/2023] Open
Abstract
Episodic ataxia type 1 (EA1) is an autosomal dominant neurological disorder characterized by myokymia and attacks of ataxic gait often precipitated by stress. Several genetic mutations have been identified in the Shaker-like K+ channel Kv1.1 (KCNA1) of EA1 individuals, including V408A, which result in remarkable channel dysfunction. By inserting the heterozygous V408A, mutation in one Kv1.1 allele, a mouse model of EA1 has been generated (Kv1.1V408A/+). Here, we investigated the neuromuscular transmission of Kv1.1V408A/+ ataxic mice and their susceptibility to physiologically relevant stressors. By using in vivo preparations of lateral gastrocnemius (LG) nerve–muscle from Kv1.1+/+ and Kv1.1V408A/+ mice, we show that the mutant animals exhibit spontaneous myokymic discharges consisting of repeated singlets, duplets or multiplets, despite motor nerve axotomy. Two-photon laser scanning microscopy from the motor nerve, ex vivo, revealed spontaneous Ca2 + signals that occurred abnormally only in preparations dissected from Kv1.1V408A/+ mice. Spontaneous bursting activity, as well as that evoked by sciatic nerve stimulation, was exacerbated by muscle fatigue, ischemia and low temperatures. These stressors also increased the amplitude of compound muscle action potential. Such abnormal neuromuscular transmission did not alter fiber type composition, neuromuscular junction and vascularization of LG muscle, analyzed by light and electron microscopy. Taken together these findings provide direct evidence that identifies the motor nerve as an important generator of myokymic activity, that dysfunction of Kv1.1 channels alters Ca2 + homeostasis in motor axons, and also strongly suggest that muscle fatigue contributes more than PNS fatigue to exacerbate the myokymia/neuromyotonia phenotype. More broadly, this study points out that juxtaparanodal K+ channels composed of Kv1.1 subunits exert an important role in dampening the excitability of motor nerve axons during fatigue or ischemic insult.
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Affiliation(s)
- Orazio Brunetti
- Section of Human Physiology, University of Perugia School of Medicine, Perugia, Italy
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25
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Bangratz M, Sarrazin N, Devaux J, Zambroni D, Echaniz-Laguna A, René F, Boërio D, Davoine CS, Fontaine B, Feltri ML, Benoit E, Nicole S. A mouse model of Schwartz-Jampel syndrome reveals myelinating Schwann cell dysfunction with persistent axonal depolarization in vitro and distal peripheral nerve hyperexcitability when perlecan is lacking. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 180:2040-55. [PMID: 22449950 DOI: 10.1016/j.ajpath.2012.01.035] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 12/22/2011] [Accepted: 01/10/2012] [Indexed: 12/31/2022]
Abstract
Congenital peripheral nerve hyperexcitability (PNH) is usually associated with impaired function of voltage-gated K(+) channels (VGKCs) in neuromyotonia and demyelination in peripheral neuropathies. Schwartz-Jampel syndrome (SJS) is a form of PNH that is due to hypomorphic mutations of perlecan, the major proteoglycan of basement membranes. Schwann cell basement membrane and its cell receptors are critical for the myelination and organization of the nodes of Ranvier. We therefore studied a mouse model of SJS to determine whether a role for perlecan in these functions could account for PNH when perlecan is lacking. We revealed a role for perlecan in the longitudinal elongation and organization of myelinating Schwann cells because perlecan-deficient mice had shorter internodes, more numerous Schmidt-Lanterman incisures, and increased amounts of internodal fast VGKCs. Perlecan-deficient mice did not display demyelination events along the nerve trunk but developed dysmyelination of the preterminal segment associated with denervation processes at the neuromuscular junction. Investigating the excitability properties of the peripheral nerve suggested a persistent axonal depolarization during nerve firing in vitro, most likely due to defective K(+) homeostasis, and excluded the nerve trunk as the original site for PNH. Altogether, our data shed light on perlecan function by revealing critical roles in Schwann cell physiology and suggest that PNH in SJS originates distally from synergistic actions of peripheral nerve and neuromuscular junction changes.
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Affiliation(s)
- Marie Bangratz
- INSERM, U975, Research Center of the Brain and Spinal Cord Institute, U975, Paris, France
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26
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Zhang Y, Bekku Y, Dzhashiashvili Y, Armenti S, Meng X, Sasaki Y, Milbrandt J, Salzer JL. Assembly and maintenance of nodes of ranvier rely on distinct sources of proteins and targeting mechanisms. Neuron 2012; 73:92-107. [PMID: 22243749 DOI: 10.1016/j.neuron.2011.10.016] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/17/2011] [Indexed: 01/29/2023]
Abstract
VIDEO ABSTRACT We have investigated the source(s) and targeting of components to PNS nodes of Ranvier. We show adhesion molecules are freely diffusible within the axon membrane and accumulate at forming nodes from local sources, whereas ion channels and cytoskeletal components are largely immobile and require transport to the node. We further characterize targeting of NF186, an adhesion molecule that pioneers node formation. NF186 redistributes to nascent nodes from a mobile, surface pool. Its initial accumulation and clearance from the internode require extracellular interactions, whereas targeting to mature nodes, i.e., those flanked by paranodal junctions, requires intracellular interactions. After incorporation into the node, NF186 is immobile, stable, and promotes node integrity. Thus, nodes assemble from two sources: adhesion molecules, which initiate assembly, accumulate by diffusion trapping via interactions with Schwann cells, whereas ion channels and cytoskeletal components accumulate via subsequent transport. In mature nodes, components turnover slowly and are replenished via transport.
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Affiliation(s)
- Yanqing Zhang
- Smilow Neuroscience Program, New York University Langone Medical Center, New York, NY 10016, USA
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27
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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: 28] [Impact Index Per Article: 2.3] [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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28
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Cifuentes-Diaz C, Chareyre F, Garcia M, Devaux J, Carnaud M, Levasseur G, Niwa-Kawakita M, Harroch S, Girault JA, Giovannini M, Goutebroze L. Protein 4.1B contributes to the organization of peripheral myelinated axons. PLoS One 2011; 6:e25043. [PMID: 21966409 PMCID: PMC3180372 DOI: 10.1371/journal.pone.0025043] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 08/23/2011] [Indexed: 12/26/2022] Open
Abstract
Neurons are characterized by extremely long axons. This exceptional cell shape is likely to depend on multiple factors including interactions between the cytoskeleton and membrane proteins. In many cell types, members of the protein 4.1 family play an important role in tethering the cortical actin-spectrin cytoskeleton to the plasma membrane. Protein 4.1B is localized in myelinated axons, enriched in paranodal and juxtaparanodal regions, and also all along the internodes, but not at nodes of Ranvier where are localized the voltage-dependent sodium channels responsible for action potential propagation. To shed light on the role of protein 4.1B in the general organization of myelinated peripheral axons, we studied 4.1B knockout mice. These mice displayed a mildly impaired gait and motility. Whereas nodes were unaffected, the distribution of Caspr/paranodin, which anchors 4.1B to the membrane, was disorganized in paranodal regions and its levels were decreased. In juxtaparanodes, the enrichment of Caspr2, which also interacts with 4.1B, and of the associated TAG-1 and Kv1.1, was absent in mutant mice, whereas their levels were unaltered. Ultrastructural abnormalities were observed both at paranodes and juxtaparanodes. Axon calibers were slightly diminished in phrenic nerves and preterminal motor axons were dysmorphic in skeletal muscle. βII spectrin enrichment was decreased along the axolemma. Electrophysiological recordings at 3 post-natal weeks showed the occurrence of spontaneous and evoked repetitive activity indicating neuronal hyperexcitability, without change in conduction velocity. Thus, our results show that in myelinated axons 4.1B contributes to the stabilization of membrane proteins at paranodes, to the clustering of juxtaparanodal proteins, and to the regulation of the internodal axon caliber.
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Affiliation(s)
- Carmen Cifuentes-Diaz
- Inserm, UMR-S 839, Paris, France
- Université Pierre et Marie Curie (UPMC), Paris, France
- Institut du Fer à Moulin, Paris, France
| | - Fabrice Chareyre
- Inserm, U674, Institut Universitaire d'Hématologie, Paris, France
| | - Marta Garcia
- Inserm, UMR-S 839, Paris, France
- Université Pierre et Marie Curie (UPMC), Paris, France
- Institut du Fer à Moulin, Paris, France
| | - Jérôme Devaux
- Département de Signalisation Neuronale, CRN2M, UMR 6231, CNRS, Université de la Méditerranée-Université Paul Cézanne, IFR Jean Roche, Marseille, France
| | - Michèle Carnaud
- Inserm, UMR-S 839, Paris, France
- Université Pierre et Marie Curie (UPMC), Paris, France
- Institut du Fer à Moulin, Paris, France
| | - Grégoire Levasseur
- Inserm, UMR-S 839, Paris, France
- Université Pierre et Marie Curie (UPMC), Paris, France
- Institut du Fer à Moulin, Paris, France
| | | | - Sheila Harroch
- Département de Neuroscience, Institut Pasteur, Paris, France
| | - Jean-Antoine Girault
- Inserm, UMR-S 839, Paris, France
- Université Pierre et Marie Curie (UPMC), Paris, France
- Institut du Fer à Moulin, Paris, France
- * E-mail:
| | - Marco Giovannini
- Inserm, U674, Institut Universitaire d'Hématologie, Paris, France
| | - Laurence Goutebroze
- Inserm, UMR-S 839, Paris, France
- Université Pierre et Marie Curie (UPMC), Paris, France
- Institut du Fer à Moulin, Paris, France
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