Preserving neuromuscular synapses in ALS by stimulating MuSK with a therapeutic agonist antibody

Cantor, Sarah; Zhang, Wei; Delestrée, Nicolas; Remédio, Leonor; Mentis, George Z.; Burden, Steven J.

doi:10.7554/elife.34375

Cited by 63 publications

(70 citation statements)

References 43 publications

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“…The amplified Agrin-induced phosphorylation may be associated with the binding to the Ig-like domain 2. We reason the mAbs dimerized MuSK, by nature of their bivalency and monospecificity, which led to the autophosphorylation, as this has been observed through using agonistic MuSK mAbs (19,74,75). However, it remains to be determined how binding to domains outside of Iglike domain 1 mediated downstream activation of MuSK and other molecules in the NMJ.…”

Section: Musk Autoantibody Igg Subclasses and Epitope Recognitionmentioning

confidence: 88%

“…Thus, these mAbs behave in a manner opposite to that which is observed with serum-derived IgG. Given their recombinant expression, all of our mAbs were divalent and monospecific and consequently they effectively cross-linked MuSK, which has been shown to affect phosphorylation in murine models (19,74,75). The IgG4 mAbs may participate in Fab-arm exchange (predominantly with IgG4 antibodies of other specificities) in vivo and thus could still inhibit clustering but not crosslink MuSK and thereby not amplify autophosphorylation.…”

Section: Musk Autoantibody Igg Subclasses and Epitope Recognitionmentioning

confidence: 95%

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Isolation and characterization of rare circulating autoantibody-producing cells from patients with muscle-specific kinase myasthenia gravis

Takata

Stathopoulos

Cao

et al. 2018

Preprint

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Myasthenia gravis (MG) is a chronic autoimmune disorder characterized by muscle weakness and caused by autoantibodies that bind to functional membrane proteins at the neuromuscular junction. Most patients have autoantibodies to the acetylcholine receptor (AChR), but a subset of patients instead have autoantibodies to muscle specific tyrosine kinase (MuSK). MuSK is an essential component of the Agrin/Lipoprotein receptor-related protein 4(LRP4)/MuSK/downstream of tyrosine kinase 7 (DOK7) pathway that is responsible for synaptic differentiation, including clustering of AChRs at the neuromuscular junction, both during development and in adult muscle. Nerve-released Agrin binds to LRP4 which then binds to MuSK, stimulating autophosphorylation and recruitment of DOK7 to complete the membrane component of the pathway. Serum-derived IgG4 subclass MuSK autoantibodies prevent the binding of LRP4 to MuSK, subsequently impairing autophosphorylation, resulting in the loss of Agrin-induced AChR clustering in the mouse myotube-forming C2C12 line. Although this autoimmune mechanism appears well understood, MuSK autoantibodies from patients are polyclonal. Most are IgG4 but IgG1, 2 and 3 are also present and can achieve similar results on AChR clustering. In addition, most bind the first Ig-like domain in MuSK, however some patients harbor serum autoantibodies that recognize other domains in MuSK. We sought to establish individual MuSK IgG clones so that the disease mechanisms could be better understood. We isolated MuSK autoantibody-expressing B cells from MuSK MG patients with a fluorescenttagged MuSK antigen multimer and generated a panel of human monoclonal autoantibodies(mAbs) from these cells. We produced 77 mAbs from single B cells collected from six MuSK MG patients. Here we focused on three highly specific mAbs that bound quantitatively to MuSK in solution, to MuSK-expressing HEK cells and at mouse neuromuscular junctions where they colocalized with AChRs. These three IgG isotype mAbs (two IgG4 and one IgG3 subclass) recognized the Ig-like domain 2 of MuSK. The three MuSK mAbs inhibited Agrin induced-AChR clustering in C2C12 myotubes, but intriguingly, they enhanced rather than inhibited MuSK phosphorylation. This approach for ex vivo isolation of MuSK MG autoantibody-producing cells and production of human recombinant mAbs has identified distinct autoantibody specificities and likely divergent effector mechanisms. Collectively, these findings will enable a better understanding of MuSK autoantibody-mediated pathology.

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Section: Musk Autoantibody Igg Subclasses and Epitope Recognitionmentioning

confidence: 88%

Section: Musk Autoantibody Igg Subclasses and Epitope Recognitionmentioning

confidence: 95%

Isolation and characterization of rare circulating autoantibody-producing cells from patients with muscle-specific kinase myasthenia gravis

Takata

Stathopoulos

Cao

et al. 2018

Preprint

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“…Recently, a monoclonal MuSK antibody was shown to stimulate MuSK phosphorylation and to preserve NMJs in a motor neuron disease model. 23 Using new or repurposed drugs to enhance MuSK phosphorylation, or other downstream components of the signaling pathway, could be beneficial in MuSK-Ab myasthenia and perhaps in other disorders of neuromuscular transmission where loss of AChRs or disruption of the NMJ structure underlies the muscle weakness.…”

Section: Discussionmentioning

confidence: 99%

SHP2 inhibitor protects AChRs from effects of myasthenia gravis MuSK antibody

Huda

Cao

Rosa

et al. 2020

Neurol Neuroimmunol Neuroinflamm

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ObjectiveTo determine whether an SRC homology 2 domain-containing phosphotyrosine phosphatase 2 (SHP2) inhibitor would increase muscle-specific kinase (MuSK) phosphorylation and override the inhibitory effect of MuSK-antibodies (Abs). MethodsThe effect of the SHP2 inhibitor NSC-87877 on MuSK phosphorylation and AChR clustering was tested in C2C12 myotubes with 31 MuSK-myasthenia gravis (MG) sera and purified MuSK-MG IgG4 preparations. ResultsIn the absence of MuSK-MG Abs, NSC-87877 increased MuSK phosphorylation and the number of AChR clusters in C2C12 myotubes in vitro and in DOK7-overexpressing C2C12 myotubes that form spontaneous AChR clusters. In the presence of MuSK-MG sera, the AChR clusters were reduced, as expected, but NSC-87877 was able to protect or restore the clusters. Two purified MuSK-MG IgG4 preparations inhibited both MuSK phosphorylation and AChR cluster formation, and in both, clusters were restored with NSC-87877. ConclusionsStimulating the agrin-LRP4-MuSK-DOK7 AChR clustering pathway with NSC-87877, or other drugs, could represent a novel therapeutic approach for MuSK-MG and could potentially improve other NMJ disorders with reduced AChR numbers or disrupted NMJs. Myastheniafollowing collection(s): This article, along with others on similar topics, appears in the Permissions & Licensing http://nn.neurology.org/misc/about.xhtml#permissions its entirety can be found online at: Information about reproducing this article in parts (figures,tables) or in Reprints http://nn.neurology.org/misc/addir.xhtml#reprintsus Information about ordering reprints can be found online: Academy of Neurology.. All rights reserved. Online

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“…Precise targeting of MuSK autoantibody-expressing B cells with CAAR-T cells [53] gains further justification by the additional mechanistic details provided in the current study. An agonist antibody to MuSK, which stimulated muscular signaling, showed promising effects in a mouse model of amyotrophic lateral sclerosis (ALS) [54]. Our data, showing that early naïve precursors of antibody-secreting cells (ASCs) have high affinity BCRs, provides further interest in the use of such technology, as naïve precursors, as well as ASCs may be eliminated by this strategy.…”

Section: Immunomodulating Therapy In Musk Mgmentioning

confidence: 81%

Self-antigen driven affinity maturation is required for pathogenic monovalent IgG4 autoantibody development

Fichtner

Vieni

et al. 2020

Preprint

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Pathogenic IgG4 autoantibodies in autoimmune myasthenia gravis (MG) are functionally monovalent as a result of Fab-arm exchange. The origin and development of these unique autoantibodies are not well understood. We examined MG patient-derived monoclonal autoantibodies (mAbs), their corresponding germline-encoded unmutated common ancestors (UCA) and monovalent antigen-binding fragments (Fabs) to investigate how antigen-driven affinity maturation contributes to both binding and immunopathology. Mature mAbs, their UCA counterparts and mature monovalent Fabs bound to the autoantigen and retained their pathogenic capacity. However, monovalent UCA Fabs still bound the autoantigen but lost their pathogenic capacity. The mature Fabs were characterized by very high affinity (sub-nanomolar) driven by a rapid on-rate and slow off-rate. However, the UCA affinity was approximately 100fold less than that of the mature Fabs, which was driven by a rapid off-rate. Crystal structures of two Fabs shed light on how mutations acquired during affinity maturation may contribute to increased MuSK binding affinity. These collective findings indicate that the autoantigen initiates the autoimmune response in MuSK MG and drives autoimmunity through the accumulation of somatic hypermutation such that monovalent IgG4 Fab-arm exchanged MG autoantibodies reach a high affinity threshold required for pathogenic capacity.

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Preserving neuromuscular synapses in ALS by stimulating MuSK with a therapeutic agonist antibody

Cited by 63 publications

References 43 publications

Isolation and characterization of rare circulating autoantibody-producing cells from patients with muscle-specific kinase myasthenia gravis

Isolation and characterization of rare circulating autoantibody-producing cells from patients with muscle-specific kinase myasthenia gravis

SHP2 inhibitor protects AChRs from effects of myasthenia gravis MuSK antibody

Self-antigen driven affinity maturation is required for pathogenic monovalent IgG4 autoantibody development

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