Autoantibody of NRIP, a novel AChR‐interacting protein, plays a detrimental role in myasthenia gravis

Tsai, Li‐Kai; Chen, I-Hsin; Chao, Chi‐Chao; Hsueh, Hsueh‐Wen; Chen, Hsin-Hsiung; Huang, Yi‐Hui Christine; Weng, Rong-Wei; Lai, Tai‐Shuan; Tsai, Yi‐Chieh; Tsao, Yeou‐Ping; Chen, Show‐Li

doi:10.1002/jcsm.12697

Cited by 4 publications

(1 citation statement)

References 26 publications

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“…Additionally, NRIP can bind to α-actinin 2 (ACTN2) to regulate the length of the Z-band and maintain the integrity of the sarcomere structure in heart muscles (Yang et al, 2019). Moreover, NRIP also directly binds with acetylcholine receptor (AChR) to form AChR complexes for neuron muscular junction formation (Tsai et al, 2021). Deprivation of NRIP in muscle not only causes muscle cell pathology and abnormal neuron muscular junction, but also decreases α−motor neuron number (Chen et al, 2018); indicating that muscle NRIP can retrogradely regulate motor neuron growth in the spinal cord.…”

Section: Discussionmentioning

confidence: 99%

Nuclear receptor interaction protein (NRIP) as a novel actin-binding protein involved in invadosome formation for myoblast fusion

Chen

Han

et al. 2022

Preprint

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To investigate the role of nuclear receptor interaction protein (NRIP) in myoblast fusion, both the primary myoblasts from muscle-specific NRIP-knockout mice and NRIP-null C2C12 cells (KO19 cells) exhibited a significant deficit in the fusion index during myogenesis; on the other hand, overexpressed NRIP in KO19 cells could rescue myotube formation. Furthermore, NRIP was found to interact with actin directly and reciprocally that is an invadosome component for myoblast fusion. Endogenous NRIP colocalized with components of invadosome such as F-actin, Tks5, and cortactin at the tips of cells during C2C12 differentiation, and exogenous NRIP was enriched with actin at the tip of attacking cells during myogenic fusion, implying that NRIP is a novel invadosome component. Using time-lapse microscopy and cell–cell fusion assays further confirmed NRIP directly participates in cell fusion through actin. Moreover, to map the domain of NRIP–actin binding, NRIP interacted with actin either through WD40 domains directly for binding or indirectly through the IQ domain for α-actinin 2 binding with actin. NRIP with actin binding was strongly correlated with invadosome formation and myotube fusion. Collectively, NRIP acts as a novel actin-binding protein through its WD40 or the IQ to form invadosomes that trigger myoblast fusion.

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Section: Discussionmentioning

confidence: 99%

Nuclear receptor interaction protein (NRIP) as a novel actin-binding protein involved in invadosome formation for myoblast fusion

Chen

Han

et al. 2022

Preprint

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Autoantibody of NRIP, a novel AChR‐interacting protein, plays a detrimental role in myasthenia gravis

Tsai

Chen

Chao

et al. 2021

J cachexia sarcopenia muscle

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Background Nuclear receptor interaction protein (NRIP) co‐localizes with acetylcholine receptor (AChR) at the neuromuscular junction (NMJ), and NRIP deficiency causes aberrant NMJ architecture. However, the normal physiological and pathophysiological roles of NRIP in NMJ are still unclear. Methods We investigated the co‐localization and interaction of NRIP with AChR‐associated proteins using immunofluorescence and immunoprecipitation assay, respectively. The binding affinity of AChR‐associated proteins was analysed in muscle‐restricted NRIP knockout mice and NRIP knockout muscle cells (C2C12). We further collected the sera from 43 patients with myasthenia gravis (MG), an NMJ disorder. The existence and features of anti‐NRIP autoantibody in sera were studied using Western blot and epitope mapping. Results NRIP co‐localized with AChR, rapsyn and α‐actinin 2 (ACTN2) in gastrocnemius muscles of mice; and α‐bungarotoxin (BTX) pull‐down assay revealed NRIP with rapsyn and ACTN2 in complexes from muscle tissues and cells. NRIP directly binds with α subunit of AChR (AChRα) in vitro and in vivo to affect the binding affinity of AChR with rapsyn and rapsyn with ACTN2. In 43 patients with MG (age, 58.4 ± 14.5 years; female, 55.8%), we detected six of them (14.0%) having anti‐NRIP autoantibody. The presence of anti‐NRIP autoantibody correlated with a more severe type of MG when AChR autoantibody existed (P = 0.011). The higher the titre of anti‐NRIP autoantibody, the more severe MG severity (P = 0.032). The main immunogenic region is likely on the IQ motif of NRIP. We also showed the IgG subclass of anti‐NRIP autoantibody mainly to be IgG1. Conclusions NRIP is a novel AChRα binding protein and involves structural NMJ formation, which acts as a scaffold to stabilize AChR–rapsyn–ACTN2 complexes. Anti‐NRIP autoantibody is a novel autoantibody in MG and plays a detrimental role in MG with the coexistence of anti‐AChR autoantibody.

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AAV-NRIP gene therapy ameliorates motor neuron degeneration and muscle atrophy in ALS model mice

Chen,

Yeo,

Huang

et al. 2024

Skeletal Muscle

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Background Amyotrophic lateral sclerosis (ALS) is characterized by progressive motor neuron (MN) degeneration, leading to neuromuscular junction (NMJ) dismantling and severe muscle atrophy. The nuclear receptor interaction protein (NRIP) functions as a multifunctional protein. It directly interacts with calmodulin or α-actinin 2, serving as a calcium sensor for muscle contraction and maintaining sarcomere integrity. Additionally, NRIP binds with the acetylcholine receptor (AChR) for NMJ stabilization. Loss of NRIP in muscles results in progressive motor neuron degeneration with abnormal NMJ architecture, resembling ALS phenotypes. Therefore, we hypothesize that NRIP could be a therapeutic factor for ALS. Methods We used SOD1 G93A mice, expressing human SOD1 with the ALS-linked G93A mutation, as an ALS model. An adeno-associated virus vector encoding the human NRIP gene (AAV-NRIP) was generated and injected into the muscles of SOD1 G93A mice at 60 days of age, before disease onset. Pathological and behavioral changes were measured to evaluate the therapeutic effects of AAV-NRIP on the disease progression of SOD1 G93A mice. Results SOD1 G93A mice exhibited lower NRIP expression than wild-type mice in both the spinal cord and skeletal muscle tissues. Forced NRIP expression through AAV-NRIP intramuscular injection was observed in skeletal muscles and retrogradely transduced into the spinal cord. AAV-NRIP gene therapy enhanced movement distance and rearing frequencies in SOD1 G93A mice. Moreover, AAV-NRIP increased myofiber size and slow myosin expression, ameliorated NMJ degeneration and axon terminal denervation at NMJ, and increased the number of α-motor neurons (α-MNs) and compound muscle action potential (CMAP) in SOD1 G93A mice. Conclusions AAV-NRIP gene therapy ameliorates muscle atrophy, motor neuron degeneration, and axon terminal denervation at NMJ, leading to increased NMJ transmission and improved motor functions in SOD1 G93A mice. Collectively, AAV-NRIP could be a potential therapeutic drug for ALS.

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Autoantibody of NRIP, a novel AChR‐interacting protein, plays a detrimental role in myasthenia gravis

Cited by 4 publications

References 26 publications

Nuclear receptor interaction protein (NRIP) as a novel actin-binding protein involved in invadosome formation for myoblast fusion

Nuclear receptor interaction protein (NRIP) as a novel actin-binding protein involved in invadosome formation for myoblast fusion

Autoantibody of NRIP, a novel AChR‐interacting protein, plays a detrimental role in myasthenia gravis

AAV-NRIP gene therapy ameliorates motor neuron degeneration and muscle atrophy in ALS model mice

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