PMID- 37582613 OWN - NLM STAT- MEDLINE DCOM- 20230817 LR - 20240214 IS - 2332-7812 (Electronic) IS - 2332-7812 (Linking) VI - 10 IP - 6 DP - 2023 Nov TI - IgG1-3 MuSK Antibodies Inhibit AChR Cluster Formation, Restored by SHP2 Inhibitor, Despite Normal MuSK, DOK7, or AChR Subunit Phosphorylation. LID - 10.1212/NXI.0000000000200147 [doi] LID - e200147 AB - BACKGROUND AND OBJECTIVES: Up to 50% of patients with myasthenia gravis (MG) without acetylcholine receptor antibodies (AChR-Abs) have antibodies to muscle-specific kinase (MuSK). Most MuSK antibodies (MuSK-Abs) are IgG4 and inhibit agrin-induced MuSK phosphorylation, leading to impaired clustering of AChRs at the developing or mature neuromuscular junction. However, IgG1-3 MuSK-Abs also exist in MuSK-MG patients, and their potential mechanisms have not been explored fully. METHODS: C2C12 myotubes were exposed to MuSK-MG plasma IgG1-3 or IgG4, with or without purified agrin. MuSK, Downstream of Kinase 7 (DOK7), and betaAChR were immunoprecipitated and their phosphorylation levels identified by immunoblotting. Agrin and agrin-independent AChR clusters were measured by immunofluorescence and AChR numbers by binding of (125)I-alpha-bungarotoxin. Transcriptomic analysis was performed on treated myotubes. RESULTS: IgG1-3 MuSK-Abs impaired AChR clustering without inhibiting agrin-induced MuSK phosphorylation. Moreover, the well-established pathway initiated by MuSK through DOK7, resulting in betaAChR phosphorylation, was not impaired by MuSK-IgG1-3 and was agrin-independent. Nevertheless, the AChR clusters did not form, and both the number of AChR microclusters that precede full cluster formation and the myotube surface AChRs were reduced. Transcriptomic analysis did not throw light on the pathways involved. However, the SHP2 inhibitor, NSC-87877, increased the number of microclusters and led to fully formed AChR clusters. DISCUSSION: MuSK-IgG1-3 is pathogenic but seems to act through a noncanonical pathway. Further studies should throw light on the mechanisms involved at the neuromuscular junction. CI - Copyright (c) 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology. FAU - Cao, Michelangelo AU - Cao M AUID- ORCID: 0000-0001-6249-2870 AD - From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy. FAU - Liu, Wei-Wei AU - Liu WW AUID- ORCID: 0009-0003-2424-4990 AD - From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy. FAU - Maxwell, Susan AU - Maxwell S AUID- ORCID: 0009-0009-6514-149X AD - From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy. FAU - Huda, Saif AU - Huda S AUID- ORCID: 0000-0003-0980-3750 AD - From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy. FAU - Webster, Richard AU - Webster R AUID- ORCID: 0000-0001-7893-1348 AD - From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy. FAU - Evoli, Amelia AU - Evoli A AD - From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy. FAU - Beeson, David AU - Beeson D AUID- ORCID: 0000-0001-9395-7132 AD - From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy. FAU - Cossins, Judith A AU - Cossins JA AUID- ORCID: 0000-0003-2323-622X AD - From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy. FAU - Vincent, Angela AU - Vincent A AD - From the Nuffield Department of Clinical Neurosciences (M.C., W.W.L., S.M., R.W., D.B., J.A.C., A.V.), University of Oxford; Norfolk and Norwich University Hospital (M.C.); The Walton Centre NHS Foundation Trust (S.H.), Liverpool, United Kingdom; and Department of Neuroscience (A.E.), Catholic University, Rome, Italy. angela.vincent@ndcn.ox.ac.uk. LA - eng GR - MR/M006824/1/MRC_/Medical Research Council/United Kingdom PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20230815 PL - United States TA - Neurol Neuroimmunol Neuroinflamm JT - Neurology(R) neuroimmunology & neuroinflammation JID - 101636388 RN - 0 (Agrin) RN - 0 (DOK7 protein, human) RN - 0 (Immunoglobulin G) RN - 0 (Muscle Proteins) RN - EC 2.7.10.1 (Receptor Protein-Tyrosine Kinases) RN - 0 (Receptors, Cholinergic) SB - IM MH - Humans MH - Agrin/pharmacology MH - Immunoglobulin G MH - Muscle Proteins/metabolism MH - *Myasthenia Gravis/drug therapy MH - Phosphorylation MH - *Receptor Protein-Tyrosine Kinases MH - Receptors, Cholinergic PMC - PMC10427144 COIS- A. Vincent received a proportion of royalties for a patent held by the University of Oxford for use of MuSK for antibody assays, licensed to Athena Diagnostics, that expired in 2021. The other authors report no relevant disclosures. Go to Neurology.org/NN for full disclosures. EDAT- 2023/08/16 00:42 MHDA- 2023/08/17 06:43 PMCR- 2023/08/15 CRDT- 2023/08/15 20:52 PHST- 2023/04/06 00:00 [received] PHST- 2023/06/07 00:00 [accepted] PHST- 2023/08/17 06:43 [medline] PHST- 2023/08/16 00:42 [pubmed] PHST- 2023/08/15 20:52 [entrez] PHST- 2023/08/15 00:00 [pmc-release] AID - 10/6/e200147 [pii] AID - NXI-2023-000215 [pii] AID - 10.1212/NXI.0000000000200147 [doi] PST - epublish SO - Neurol Neuroimmunol Neuroinflamm. 2023 Aug 15;10(6):e200147. doi: 10.1212/NXI.0000000000200147. Print 2023 Nov.