Biology subjects

Vergoossen, D. L. E.

Publications and source records attributed to Vergoossen, D. L. E..

6 recordsLinked to original sources

bioRxiv2026

MuSK antibodies differently affect the MuSK signaling cascade depending on valency and epitope specificity

Muscle-specific kinase (MuSK) is a pivotal player in forming and maintaining healthy neuromuscular junctions (NMJ). In MuSK myasthenia gravis (MG), autoantibodies targeting MuSK disrupt its function, impairing neuromuscular transmission and causing fatigable skeletal muscle weakness. MuSK autoantibodies predominantly belong to the IgG4 subclass, which bind in a monovalent fashion due to Fab-arm exchange, although autoantibodies of other subclasses also exist. Polyclonal autoreactive IgG from patients may therefore harbor a variety of monovalent and bivalent MuSK antibodies with potentially distinct effects on MuSK signaling. To further unravel the pathomechanisms underlying MuSK MG, we have investigated how MuSK antibody-binding affects MuSK functioning with a diverse panel of (patient-derived) monoclonal MuSK antibodies. Our findings reveal that the valency of antibody-binding influences binding kinetics to MuSK, inhibition of agrin-induced MuSK activation, Dok7 binding to MuSK and NMJ gene expression. Monovalent binding to the frizzled domain of MuSK did not inhibit agrin-induced MuSK activation, while monovalent binding to the Ig-like domain 1 does. Moreover, the kinetics of Dok7 degradation induced by bivalent MuSK antibodies appear to depend on binding-epitope of MuSK. Surprisingly, none of the clones tested (both bivalent and monovalent) increased MuSK internalization. Taken together, the cumulative pathogenic effect of polyclonal MuSK antibodies in individual MuSK MG patients thus likely depends on autoantibody titer, affinity and the unique composition of MuSK autoantibodies varying in epitope and valency. This research enriches our understanding of the intricate interactions between antibodies and MuSK in MuSK MG and offers potential insights into novel therapeutic strategies using MuSK antibodies.

immunology↗

bioRxiv2024

Patient-specific therapeutic benefit of MuSK agonist antibody ARGX-119 in MuSK myasthenia gravis passive transfer models

Muscle-specific kinase (MuSK) orchestrates establishment and maintenance of neuromuscular synapses, which enable muscle contraction. Autoantibodies targeting MuSK cause myasthenia gravis (MG), a disease characterized by fatigable skeletal muscle weakness which requires chronic immunosuppressive treatment and ventilatory support at some point in [~]30% of patients. MuSK autoantibodies are predominantly IgG4 and are bispecific, functionally monovalent antibodies due to Fab-arm exchange. Through monovalent binding, MuSK IgG4 autoantibodies act as antagonists on the MuSK signalling pathway, impairing neuromuscular synaptic function. In contrast, bivalent MuSK antibodies act as agonists of the MuSK signalling pathway. Since symptoms in MuSK MG are largely caused by antagonistic monovalent MuSK antibodies, we hypothesized that a bivalent MuSK agonist could rescue MuSK MG, bypassing the need for generalized immunosuppression. In this study, we investigated whether an agonist antibody targeting the Frizzled-like domain of MuSK, ARGX-119, can ameliorate disease in MuSK MG models induced by passive transfer of polyclonal IgG4 from unrelated patients. For each patient material we first established the minimal dose for a progressive MG phenotype based on muscle function tests. ARGX-119 significantly improved survival and muscle weakness in a mouse model induced by one patient material, but not by three others. Mechanistically, this patient-specific efficacy could not be explained by autoantibody epitope specificity, titer or competition for ARGX-119 binding, but rather correlated to the presence of MuSK activating antibodies in some patients. We further provide evidence that an in vitro assay may predict which patients potentially benefit from ARGX-119 and that this treatment, when effective in MuSK MG mice, follows a bell-shaped dose-effect curve. These results provide first proof of concept of a MuSK agonist in a clinically relevant model for MuSK MG. We anticipate this to be a starting point for investigating the therapeutic benefit of ARGX-119 in MuSK MG and other neuromuscular diseases hallmarked by neuromuscular synaptic dysfunction. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/606156v1_figu1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@15c08faorg.highwire.dtl.DTLVardef@1517281org.highwire.dtl.DTLVardef@3498c2org.highwire.dtl.DTLVardef@118e9af_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIMuSK agonist ARGX-119 can rescue MuSK MG in a patient-specific manner C_LIO_LIMuSK agonism follows a bell-shaped efficacy curve in this MuSK MG mouse model C_LIO_LIVariation in ARGX-119 efficacy between patient models is not explained by competition for binding on MuSK, but rather appears related to an agonistic fraction of patient antibodies C_LIO_LIAn in vitro assay is potentially predictive for treatment efficacy of the MuSK agonist C_LI

neuroscience↗

bioRxiv2024

ARGX-119, a therapeutic agonist antibody targeting MuSK

ARGX-119 is a novel, humanized, agonist monoclonal SIMPLE Antibody specific for muscle-specific kinase (MuSK) that is being developed for treatment of patients with neuromuscular diseases. ARGX-119 is the first monoclonal antibody (mAb) that binds with high affinity to the Frizzled-like domain of human, non-human primate, rat and mouse MuSK, without off-target binding, making it suitable for clinical development. Within the Fc-region, ARGX-119 harbors L234A, L235A mutations to diminish potential immune-activating effector functions. Its mode-of-action is to activate MuSK without interfering with its natural ligand neural Agrin, and cluster acetylcholine receptors (AChRs) in a dose-dependent manner, thereby stabilizing neuromuscular function. In a mouse model for DOK7 congenital myasthenia (CM), ARGX-119 prevented early postnatal lethality and reversed disease relapse by restoring neuromuscular function and reducing muscle weakness and fatigability in a dose-dependent manner. Pharmacokinetic (PK) studies in non-human primates, rats and mice revealed non-linear PK behavior of ARGX-119, indicative of target-mediated-drug disposition (TMDD) and in vivo target engagement. Instability of neuromuscular synapses contributes to symptoms in many neuromuscular diseases for example congenital myasthenia (CM), amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). ARGX-119 is a novel, first-in-class MuSK agonist mAb in clinical development. Based on this proof-of-concept study, it has the potential to alleviate neuromuscular diseases hallmarked by impaired neuromuscular synaptic function. One sentence summaryARGX-119 is a novel first-in-class MuSK agonist monoclonal antibody in clinical development for treatment of neuromuscular diseases.

neuroscience↗

bioRxiv2021

A novel post-translational proteomics platform identifies neurite outgrowth impairments in Parkinson's disease GBA-N370S dopamine neurons

The causes of Parkinsons disease (PD) likely involve complex interactions between environmental factors and susceptibility genes with variants at the GBA locus encoding the glucocerebrosidase (GCase) enzyme being the strongest common genetic risk factor for PD. To understand GBA-related disease mechanisms, we used a novel multipart-enrichment proteomics and post-translational modification workflow to simultaneously identify peptides with phosphorylation, reversible cysteine-modifications or sialylated N-linked glycosylation, alongside unmodified proteins. We identified large numbers of dysregulated proteins and post-translational modifications (PTMs) in heterozygous GBA-N370S PD patient induced pluripotent stem cells (iPSC)-derived dopamine neurons. Alterations in glycosylation status of lysosomal proteins identified disturbances in the autophagy-lysosomal pathway, concurrent with upstream perturbations in mTOR phosphorylation and activity in GBA-N370S iPSC-dopamine neurons. In addition, the strategy revealed several native and modified proteins encoded by PD-associated genes to be dysregulated in GBA-N370S neurons, enhancing our understanding of the wider role of GBA mutations on the neuronal proteome. Integrated pathway analysis of all datasets revealed impaired neuritogenesis in GBA-N370S PD iPSC-dopamine neurons and identified tau (MAPT) as a key mediator of this process. Using a functional assay, we confirmed neurite outgrowth deficits in GBA-N370S PD neurons and a central role for tau in this process. Furthermore, pharmacological restoration of GCase activity in GBA-N370S PD patient neurons rescued the neurite outgrowth deficit. Overall, this study demonstrates the potential of PTMomics to elucidate novel neurodegeneration-associated pathways and identify phenotypes and potential drug targets in complex disease models.

neuroscience↗

bioRxiv2021

Timing and localization of myasthenia gravis-related gene expression

Myasthenia gravis (MG) is an acquired autoimmune disorder caused by autoantibodies binding acetylcholine receptors (AChR), muscle-specific kinase (MuSK), agrin or low-density lipoprotein receptor-related protein 4 (Lrp4). These autoantibodies inhibit neuromuscular transmission by blocking the function of these proteins, and thereby cause fluctuating skeletal muscle weakness. Several reports suggest that these autoantibodies might also affect the central nervous system (CNS) in MG patients. A comprehensive overview of the timing and localization of the expression of MG-related antigens in other organs is currently lacking. To investigate the spatio-temporal expression of MG-related genes outside skeletal muscle, we used in silico tools to assess public expression databases. Acetylcholine esterase, nicotinic AChR 1 subunit, agrin, collagen Q, Dok7, Lrp4, MuSK and rapsyn were included as MG-related genes because of their well-known involvement in either congenital or autoimmune MG. We investigated expression of MG-related genes in 1) all human tissues using GTEx data, 2) specific brain regions, 3) neurodevelopmental stages, and 4) cell types using datasets from the Allen Institute for Brain Sciences. MG-related genes show heterogenous spatio-temporal expression patterns in the human body as well as in the CNS. For each of these genes several (new) tissues, brain areas and cortical cell types with (relatively) high expression were identified suggesting a potential role for these genes outside skeletal muscle. The possible presence of MG-related antigens outside skeletal muscle suggests that autoimmune MG, congenital MG or treatments targeting the same proteins may affect MG-related protein function in other organs.

genetics↗

bioRxiv2020

Functional monovalency amplifies the pathogenicity of anti-MuSK IgG4 in myasthenia gravis

Human IgG4 usually displays anti-inflammatory activity, and observations of IgG4 autoantibodies causing severe autoimmune disorders are therefore poorly understood. In blood, IgG4 antibodies naturally engage in a stochastic process termed Fab-arm exchange in which unrelated IgG4s exchange half-molecules continuously. The resulting IgG4 antibodies are composed of two different binding sites, thereby acquiring monovalent binding and inability to cross-link for each antigen recognized. Here, we demonstrate this process amplifies autoantibody pathogenicity in a classic IgG4-mediated autoimmune disease: muscle-specific kinase (MuSK) myasthenia gravis (MG). In mice, monovalent anti-MuSK IgG4s caused rapid and severe myasthenic muscle weakness, whereas the same antibodies in their parental bivalent form were less potent or did not induce a phenotype. Mechanistically this could be explained by opposing effects on MuSK signaling. Isotype switching to IgG4 in an autoimmune response thereby may be a critical step in the development of disease. Our study establishes functional monovalency as a novel pathogenic mechanism in IgG4-mediated autoimmune disease and potentially other disorders. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=146 HEIGHT=200 SRC="FIGDIR/small/296293v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@45c221org.highwire.dtl.DTLVardef@1cc31cdorg.highwire.dtl.DTLVardef@d9b09borg.highwire.dtl.DTLVardef@1d9b681_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗