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Saiz A, Graus F. Neuronal antibodies in nonparaneoplastic autoimmune cerebellar ataxias. Curr Opin Neurol 2024; 37:322-328. [PMID: 38483149 DOI: 10.1097/wco.0000000000001260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2024]
Abstract
PURPOSE OF REVIEW To describe relevant advances in nonparaneoplastic autoimmune cerebellar ataxias (ACA) with neuronal antibodies. RECENT FINDINGS Apart from metabotropic glutamate receptor 1(mGluR1) antibodies, in recent years, the number of neuronal antibodies against surface antigens in ACA has increased with the description of glutamate kainate receptor subunit 2 (GluK2) antibodies in young patients with cerebellitis. Around 20% of patients with contactin-associated protein-like 2 (CASPR2) encephalitis also present prominent cerebellar ataxia. However, isolate cerebellar ataxia is unusual (<4%). Outcome in patients with neuronal antibodies against surface antigens remains suboptimal despite the cerebellar ataxia probably is antibody-mediated.Concerning neuronal antibodies against intracellular antigens, up to 25% of patients with glutamic acid decarboxylase (GAD) antibodies present transient episodes of vertigo or diplopia that antedate the development of the ACA. There is in-vitro evidence that septin-5 is partially exposed to the membrane and the antibodies may interfere with septin-5 function. The clinical significance of the remaining antibodies against intracellular antigens remains unclear. SUMMARY The number of antibodies against surface antigens is increasing in ACA, but the response to the immunotherapy remains suboptimal. More studies are needed to clarify the role of most of the antibodies against intracellular antigens described in these patients.
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Affiliation(s)
- Albert Saiz
- Service of Neurology, Hospital Clinic
- Neuroimmunology Program, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Francesc Graus
- Neuroimmunology Program, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
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2
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Segal Y, Zekeridou A. Interest of rare autoantibodies in autoimmune encephalitis and paraneoplastic neurological syndromes: the utility (or futility) of rare antibody discovery. Curr Opin Neurol 2024; 37:295-304. [PMID: 38533672 DOI: 10.1097/wco.0000000000001261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2024]
Abstract
PURPOSE OF REVIEW The increasing recognition and diagnosis of autoimmune encephalitis (AE) and paraneoplastic neurological syndromes (PNS) is partly due to neural autoantibody testing and discovery. The past two decades witnessed an exponential growth in the number of identified neural antibodies. This review aims to summarize recent rare antibody discoveries in the context of central nervous system (CNS) autoimmunity and evaluate the ongoing debate about their utility. RECENT FINDINGS In the last 5 years alone 15 novel neural autoantibody specificities were identified. These include rare neural antibody biomarkers of autoimmune encephalitis, cerebellar ataxia or other movement disorders, including multifocal presentations. SUMMARY Although the clinical applications of these rare antibody discoveries may be limited by the low number of positive cases, they still provide important diagnostic, prognostic, and therapeutic insights.
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Affiliation(s)
- Yahel Segal
- Department of Laboratory Medicine and Pathology
| | - Anastasia Zekeridou
- Department of Laboratory Medicine and Pathology
- Department of Neurology
- Center for Multiple Sclerosis and Autoimmune Neurology, Mayo Clinic, Rochester, Minnesota, USA
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3
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Budhram A, Flanagan EP. Optimizing the diagnostic performance of neural antibody testing for paraneoplastic and autoimmune encephalitis in clinical practice. HANDBOOK OF CLINICAL NEUROLOGY 2024; 200:365-382. [PMID: 38494290 DOI: 10.1016/b978-0-12-823912-4.00002-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
The detection of neural antibodies in patients with paraneoplastic and autoimmune encephalitis has majorly advanced the diagnosis and management of neural antibody-associated diseases. Although testing for these antibodies has historically been restricted to specialized centers, assay commercialization has made this testing available to clinical chemistry laboratories worldwide. This improved test accessibility has led to reduced turnaround time and expedited diagnosis, which are beneficial to patient care. However, as the utilization of these assays has increased, so too has the need to evaluate how they perform in the clinical setting. In this chapter, we discuss assays for neural antibody detection that are in routine use, draw attention to their limitations and provide strategies to help clinicians and laboratorians overcome them, all with the aim of optimizing neural antibody testing for paraneoplastic and autoimmune encephalitis in clinical practice.
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Affiliation(s)
- Adrian Budhram
- Department of Clinical Neurological Sciences, Western University, London Health Sciences Centre, London, ON, Canada; Department of Pathology and Laboratory Medicine, Western University, London Health Sciences Centre, London, ON, Canada.
| | - Eoin P Flanagan
- Department of Neurology, Mayo Clinic, Rochester, MN, United States; Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, United States
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Zhu Q, Combs ME, Liu J, Bai X, Wang WB, Herring LE, Liu J, Locasale JW, Bowles DE, Gross RT, Pla MM, Mack CP, Taylor JM. GRAF1 integrates PINK1-Parkin signaling and actin dynamics to mediate cardiac mitochondrial homeostasis. Nat Commun 2023; 14:8187. [PMID: 38081847 PMCID: PMC10713658 DOI: 10.1038/s41467-023-43889-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 11/22/2023] [Indexed: 12/18/2023] Open
Abstract
The serine/threonine kinase, PINK1, and the E3 ubiquitin ligase, Parkin, are known to facilitate LC3-dependent autophagosomal encasement and lysosomal clearance of dysfunctional mitochondria, and defects in this process contribute to a variety of cardiometabolic and neurological diseases. Although recent evidence indicates that dynamic actin remodeling plays an important role in PINK1/Parkin-mediated mitochondrial autophagy (mitophagy), the underlying signaling mechanisms remain unknown. Here, we identify the RhoGAP GRAF1 (Arhgap26) as a PINK1 substrate that regulates mitophagy. GRAF1 promotes the release of damaged mitochondria from F-actin anchors, regulates mitochondrial-associated Arp2/3-mediated actin remodeling and facilitates Parkin-LC3 interactions to enhance mitochondria capture by autophagosomes. Graf1 phosphorylation on PINK1-dependent sites is dysregulated in human heart failure, and cardiomyocyte-restricted Graf1 depletion in mice blunts mitochondrial clearance and attenuates compensatory metabolic adaptations to stress. Overall, we identify GRAF1 as an enzyme that coordinates cytoskeletal and metabolic remodeling to promote cardioprotection.
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Affiliation(s)
- Qiang Zhu
- Department of Pathology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Matthew E Combs
- Department of Pathology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Juan Liu
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Xue Bai
- Department of Pathology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Wenbo B Wang
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Laura E Herring
- UNC Proteomics Core Facility, Department of Pharmacology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Jiandong Liu
- Department of Pathology, University of North Carolina, Chapel Hill, NC, 27599, USA
- McAllister Heart Institute University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Jason W Locasale
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Dawn E Bowles
- Division of Surgical Sciences, Duke University Medical Center, Durham, NC, 27710, USA
| | - Ryan T Gross
- Division of Surgical Sciences, Duke University Medical Center, Durham, NC, 27710, USA
| | - Michelle Mendiola Pla
- Division of Surgical Sciences, Duke University Medical Center, Durham, NC, 27710, USA
| | - Christopher P Mack
- Department of Pathology, University of North Carolina, Chapel Hill, NC, 27599, USA
- McAllister Heart Institute University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Joan M Taylor
- Department of Pathology, University of North Carolina, Chapel Hill, NC, 27599, USA.
- McAllister Heart Institute University of North Carolina, Chapel Hill, NC, 27599, USA.
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Rho GTPase-activating protein 17 (ARHGAP17) as additional autoimmune target in ARHGAP26-IgG/anti-Ca autoantibody-associated autoimmune encephalitis. J Neurol 2023; 270:1776-1780. [PMID: 36333454 PMCID: PMC9971044 DOI: 10.1007/s00415-022-11417-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 09/30/2022] [Accepted: 10/01/2022] [Indexed: 11/06/2022]
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Gaig C, Graus F. Motor symptoms in nonparaneoplastic CNS disorders associated with neural antibodies. HANDBOOK OF CLINICAL NEUROLOGY 2023; 196:277-294. [PMID: 37620074 DOI: 10.1016/b978-0-323-98817-9.00004-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/26/2023]
Abstract
Motor symptoms are common, and sometimes predominant, in almost all nonparaneoplastic CNS disorders associated with neural antibodies. These CNS disorders can be classified into five groups: (1) Autoimmune encephalitis with antibodies against synaptic receptors, (2) cerebellar ataxias associated with neuronal antibodies that mostly target intracellular antigens. (3) Stiff-person syndrome and progressive encephalomyelitis with rigidity and myoclonus which have antibodies against glutamic acid decarboxylase and glycine receptor, respectively. Both diseases have in common the presence of predominant muscle stiffness and rigidity. (4) Three diseases associated with glial antibodies. Two present motor symptoms mainly due to the involvement of the spinal cord: neuromyelitis optica spectrum disorders with aquaporin-4 antibodies and myelin oligodendrocyte glycoprotein antibody-associated disease. The third disorder is the meningoencephalitis associated with glial fibrillar acidic protein antibodies which frequently also presents a myelopathy. (5) Two antibody-related diseases which are characterized by prominent sleep dysfunction: anti-IgLON5 disease, a disorder that frequently presents a variety of movement disorders, and Morvan syndrome associated with contactin-associated protein-like 2 antibodies and clinical manifestations of peripheral nerve hyperexcitability. In this chapter, we describe the main clinical features of these five groups with particular emphasis on the presence, frequency, and types of motor symptoms.
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Affiliation(s)
- Carles Gaig
- Neurology Service, Hospital Clínic of Barcelona, Barcelona, Spain
| | - Francesc Graus
- Neuroimmunology Program, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.
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Jarius S, Komorowski L, Regula JU, Haas J, Brakopp S, Wildemann B. Rho GTPase-activating protein 10 (ARHGAP10/GRAF2) is a novel autoantibody target in patients with autoimmune encephalitis. J Neurol 2022; 269:5420-5430. [PMID: 35624318 PMCID: PMC9468106 DOI: 10.1007/s00415-022-11178-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 05/04/2022] [Accepted: 05/05/2022] [Indexed: 11/30/2022]
Abstract
Background In 2010, we described a novel immunoglobulin G (IgG) autoantibody (termed anti-Ca after the index case) targeting Rho GTPase-activating protein 26 (ARHGAP26, also termed GTPase regulator associated with focal adhesion kinase [GRAF], or oligophrenin-like protein 1 [OPHN1L]) in autoimmune cerebellar ataxia (ACA). Later, ARHGAP26-IgG/anti-Ca was reported in patients with limbic encephalitis/cognitive decline or peripheral neuropathy. In several of the reported cases, the syndrome was associated with cancer. ARHGAP10/GRAF2, which is expressed throughout the central nervous system, shares significant sequence homology with ARHGAP26/GRAF. Mutations in the ARHGAP10 gene have been linked to cognitive and psychiatric symptoms and schizophrenia. Objective To assess whether ARHGAP26-IgG/anti-Ca co-reacts with ARHGAP10. Methods Serological testing for ARHGAP10/GRAF2 autoantibodies by recombinant cell-based assays and isotype and IgG subclass analyses. Results 26/31 serum samples (84%) from 9/12 (75%) ARHGAP26-IgG/anti-Ca-positive patients and 4/6 ARHGAP26-IgG/anti-Ca-positive CSF samples from four patients were positive also for ARHGAP10-IgG. ARHGAP10-IgG (termed anti-Ca2) remained detectable in the long-term (up to 109 months) and belonged mainly to the complement-activating IgG1 subclass. Median ARHGAP26-IgG/anti-Ca and median ARHGAP10-IgG/anti-Ca2 serum titres were 1:3200 and 1:1000, respectively, with extraordinarily high titres in some samples (ARHGAP26-IgG/anti-Ca: up to 1:1000,000; ARHGAP10-IgG: up to 1:32,000). ARHGAP26/anti-Ca serum titres exceeded those of ARHGAP10-IgG in all samples but one. A subset of patients was positive also for ARHGAP10-IgM and ARHGAP10-IgA. CSF/serum ratios and antibody index calculation suggested intrathecal production of ARHGAP26-IgG/anti-Ca and anti-ARHGAP10. Of 101 control samples, 100 were completely negative for ARHGAP10-IgG; a single control sample bound weakly (1:10) to the ARHGAP10-transfected cells. Conclusions We demonstrate that a substantial proportion of patients with ARHGAP26-IgG/anti-Ca-positive autoimmune encephalitis co-react with ARHGAP10. Further studies on the clinical and diagnostic implications of ARHGAP10-IgG/anti-Ca2 seropositivity in patients with autoimmune encephalitis are warranted. Supplementary Information The online version contains supplementary material available at 10.1007/s00415-022-11178-9.
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Affiliation(s)
- Sven Jarius
- Molecular Neuroimmunology Group, Department of Neurology, University of Heidelberg, Heidelberg, Germany.
| | - Lars Komorowski
- Institute for Experimental Immunology, EUROIMMUN Medizinische Labordiagnostika AG, Lübeck, Germany
| | - Jens U Regula
- Department of Neurology, University of Heidelberg, Heidelberg, Germany.,Department of Neurology, SRH Kurpfalzkrankenhaus Heidelberg, Heidelberg, Germany
| | - Jürgen Haas
- Molecular Neuroimmunology Group, Department of Neurology, University of Heidelberg, Heidelberg, Germany
| | - Stefanie Brakopp
- Institute for Experimental Immunology, EUROIMMUN Medizinische Labordiagnostika AG, Lübeck, Germany
| | - Brigitte Wildemann
- Molecular Neuroimmunology Group, Department of Neurology, University of Heidelberg, Heidelberg, Germany
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Update on Paraneoplastic Cerebellar Degeneration. Brain Sci 2021; 11:brainsci11111414. [PMID: 34827413 PMCID: PMC8615604 DOI: 10.3390/brainsci11111414] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/20/2021] [Accepted: 10/21/2021] [Indexed: 12/16/2022] Open
Abstract
Purpose of review: To provide an update on paraneoplastic cerebellar degeneration (PCD), the involved antibodies and tumors, as well as management strategies. Recent findings: PCD represents the second most common presentation of the recently established class of immune mediated cerebellar ataxias (IMCAs). Although rare in general, PCD is one of the most frequent paraneoplastic presentations and characterized clinically by a rapidly progressive cerebellar syndrome. In recent years, several antibodies have been described in association with the clinical syndrome related to PCD; their clinical significance, however, has yet to be determined. The 2021 updated diagnostic criteria for paraneoplastic neurologic symptoms help to establish the diagnosis of PCD, direct cancer screening, and to evaluate the presence of these newly identified antibodies. Recognition of the clinical syndrome and prompt identification of a specific antibody are essential for early detection of an underlying malignancy and initiation of an appropriate treatment, which represents the best opportunity to modulate the course of the disease. As clinical symptoms can precede tumor diagnosis by years, co-occurrence of specific symptoms and antibodies should prompt continuous surveillance of the patient. Summary: We provide an in-depth overview on PCD, summarize recent findings related to PCD, and highlight the transformed diagnostic approach.
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