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Garrido JJ. Contribution of Axon Initial Segment Structure and Channels to Brain Pathology. Cells 2023; 12:cells12081210. [PMID: 37190119 DOI: 10.3390/cells12081210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Revised: 04/17/2023] [Accepted: 04/20/2023] [Indexed: 05/17/2023] Open
Abstract
Brain channelopathies are a group of neurological disorders that result from genetic mutations affecting ion channels in the brain. Ion channels are specialized proteins that play a crucial role in the electrical activity of nerve cells by controlling the flow of ions such as sodium, potassium, and calcium. When these channels are not functioning properly, they can cause a wide range of neurological symptoms such as seizures, movement disorders, and cognitive impairment. In this context, the axon initial segment (AIS) is the site of action potential initiation in most neurons. This region is characterized by a high density of voltage-gated sodium channels (VGSCs), which are responsible for the rapid depolarization that occurs when the neuron is stimulated. The AIS is also enriched in other ion channels, such as potassium channels, that play a role in shaping the action potential waveform and determining the firing frequency of the neuron. In addition to ion channels, the AIS contains a complex cytoskeletal structure that helps to anchor the channels in place and regulate their function. Therefore, alterations in this complex structure of ion channels, scaffold proteins, and specialized cytoskeleton may also cause brain channelopathies not necessarily associated with ion channel mutations. This review will focus on how the AISs structure, plasticity, and composition alterations may generate changes in action potentials and neuronal dysfunction leading to brain diseases. AIS function alterations may be the consequence of voltage-gated ion channel mutations, but also may be due to ligand-activated channels and receptors and AIS structural and membrane proteins that support the function of voltage-gated ion channels.
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Affiliation(s)
- Juan José Garrido
- Instituto Cajal, CSIC, 28002 Madrid, Spain
- Alzheimer's Disease and Other Degenerative Dementias, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), 28002 Madrid, Spain
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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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5
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Bartley CM, Ngo TT, Cadwell CR, Harroud A, Schubert RD, Alvarenga BD, Hawes IA, Zorn KC, Hunyh T, Teliska LH, Kung AF, Shah S, Gelfand JM, Chow FC, Rasband MN, Dubey D, Pittock SJ, DeRisi JL, Wilson MR, Pleasure SJ. Dual ankyrinG and subpial autoantibodies in a man with well-controlled HIV infection with steroid-responsive meningoencephalitis: A case report. Front Neurol 2023; 13:1102484. [PMID: 36756346 PMCID: PMC9900111 DOI: 10.3389/fneur.2022.1102484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 12/16/2022] [Indexed: 01/24/2023] Open
Abstract
Neuroinvasive infection is the most common cause of meningoencephalitis in people living with human immunodeficiency virus (HIV), but autoimmune etiologies have been reported. We present the case of a 51-year-old man living with HIV infection with steroid-responsive meningoencephalitis whose comprehensive pathogen testing was non-diagnostic. Subsequent tissue-based immunofluorescence with acute-phase cerebrospinal fluid revealed anti-neural antibodies localizing to the axon initial segment (AIS), the node of Ranvier (NoR), and the subpial space. Phage display immunoprecipitation sequencing identified ankyrinG (AnkG) as the leading candidate autoantigen. A synthetic blocking peptide encoding the PhIP-Seq-identified AnkG epitope neutralized CSF IgG binding to the AIS and NoR, thereby confirming a monoepitopic AnkG antibody response. However, subpial immunostaining persisted, indicating the presence of additional autoantibodies. Review of archival tissue-based staining identified candidate AnkG autoantibodies in a 60-year-old woman with metastatic ovarian cancer and seizures that were subsequently validated by cell-based assay. AnkG antibodies were not detected by tissue-based assay and/or PhIP-Seq in control CSF (N = 39), HIV CSF (N = 79), or other suspected and confirmed neuroinflammatory CSF cases (N = 1,236). Therefore, AnkG autoantibodies in CSF are rare but extend the catalog of AIS and NoR autoantibodies associated with neurological autoimmunity.
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Affiliation(s)
- Christopher M. Bartley
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Psychiatry and Behavioral Sciences, University of California, San Francisco, San Francisco, CA, United States
| | - Thomas T. Ngo
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Psychiatry and Behavioral Sciences, University of California, San Francisco, San Francisco, CA, United States
| | - Cathryn R. Cadwell
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, United States
- Department of Pathology, University of California, San Francisco, San Francisco, CA, United States
| | - Adil Harroud
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Ryan D. Schubert
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Bonny D. Alvarenga
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Isobel A. Hawes
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
- Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, CA, United States
| | - Kelsey C. Zorn
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, United States
| | - Trung Hunyh
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Lindsay H. Teliska
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States
| | - Andrew F. Kung
- School of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Shailee Shah
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, United States
- Center for Multiple Sclerosis and Autoimmune Neurology, Mayo Clinic, Rochester, MN, United States
| | - Jeffrey M. Gelfand
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Felicia C. Chow
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Matthew N. Rasband
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States
| | - Divyanshu Dubey
- Department of Neurology, Mayo Clinic Foundation, Rochester, MN, United States
- Department of Laboratory Medicine and Pathology, Mayo Clinic Foundation, Rochester, MN, United States
| | - Sean J. Pittock
- Center for Multiple Sclerosis and Autoimmune Neurology, Mayo Clinic, Rochester, MN, United States
- Department of Neurology, Mayo Clinic Foundation, Rochester, MN, United States
- Department of Laboratory Medicine and Pathology, Mayo Clinic Foundation, Rochester, MN, United States
| | - Joseph L. DeRisi
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, United States
- Chan Zuckerberg Biohub, San Francisco, CA, United States
| | - Michael R. Wilson
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
| | - Samuel J. Pleasure
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
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