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Neuromyelitis optica IgG does not alter aquaporin-4 water permeability, plasma membrane M1/M23 isoform content, or supramolecular assembly.

Rossi, A; Ratelade, J; Papadopoulos, MC; Bennett, JL; Verkman, AS (2012) Neuromyelitis optica IgG does not alter aquaporin-4 water permeability, plasma membrane M1/M23 isoform content, or supramolecular assembly. Glia, 60 (12). 2027 - 2039. https://doi.org/10.1002/glia.22417
SGUL Authors: Papadopoulos, Marios

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Abstract

Neuromyelitis optica (NMO) is thought to be caused by immunoglobulin G autoantibodies (NMO-IgG) against astrocyte water channel aquaporin-4 (AQP4). A recent study (Hinson et al. (2012) Proc Natl Acad Sci USA 109:1245-1250) reported that NMO-IgG inhibits AQP4 water permeability directly and causes rapid cellular internalization of the M1 but not M23 isoform of AQP4, resulting in AQP4 clustering, enhanced complement-dependent cytotoxicity, and tissue swelling. Here, we report evidence challenging this proposed mechanism of NMO-IgG-mediated pathology. We measured osmotic water permeability by stopped-flow light scattering on plasma membrane vesicles isolated from AQP4-expressing CHO cells, an approach that can detect changes in water permeability as small as 5% and is not confounded by internalization effects. We found similar single-molecule water permeability for M1-AQP4 tetramers and M23-AQP4 clusters (orthogonal arrays of particles, OAPs). Exposure of AQP4 to high concentrations of NMO-IgG from six seropositive NMO patients, and to high-affinity recombinant monoclonal NMO antibodies, did not reduce AQP4 water permeability. Also, NMO-IgG did not reduce water permeability in AQP4-reconstituted proteoliposomes. In transfected cells expressing M1- or M23-AQP4 individually, NMO-IgG caused more rapid internalization of M23- than M1-AQP4. In cells coexpressing both isoforms, M1- and M23-AQP4 comingled in OAPs that were internalized together in response to NMO-IgG. Super-resolution imaging and native gel electrophoresis showed that the size of AQP4 OAPs was not altered by NMO sera or recombinant NMO antibodies. We conclude that NMO-IgG does not: (i) inhibit AQP4 water permeability, (ii) cause preferential internalization of M1-AQP4, or (iii) cause intramembrane AQP4 clustering.

Item Type: Article
Additional Information: PMCID: PMC3586219
Keywords: Animals, Antibodies, Monoclonal, Aquaporin 4, Autoantibodies, CHO Cells, Cell Line, Tumor, Cell Membrane, Cell Membrane Permeability, Cricetinae, Cricetulus, Humans, Immunoglobulin G, Multiprotein Complexes, Neuromyelitis Optica, Protein Binding, Protein Isoforms, Water
SGUL Research Institute / Research Centre: Academic Structure > Molecular and Clinical Sciences Research Institute (MCS)
Academic Structure > Molecular and Clinical Sciences Research Institute (MCS) > Neuroscience (INCCNS)
Journal or Publication Title: Glia
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Dates:
DateEvent
1 December 2012Published
PubMed ID: 22987455
Web of Science ID: 22987455
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URI: https://openaccess.sgul.ac.uk/id/eprint/103925
Publisher's version: https://doi.org/10.1002/glia.22417

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