NRIP 自身抗体，一种新型的乙酰胆碱受体相互作用蛋白，在重症肌无力中发挥有害作用。

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

机构信息

Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan.

Department of Neurology, National Taiwan University Hospital, Hsinchu Branch, Hsinchu, Taiwan.

出版信息

J Cachexia Sarcopenia Muscle. 2021 Jun;12(3):665-676. doi: 10.1002/jcsm.12697. Epub 2021 Mar 26.

DOI:10.1002/jcsm.12697

PMID:33773096

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC8200423/

Abstract

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.

摘要

背景

核受体相互作用蛋白（NRIP）与乙酰胆碱受体（AChR）在神经肌肉接头（NMJ）共定位，NRIP 缺乏会导致 NMJ 结构异常。然而，NRIP 在 NMJ 中的正常生理和病理生理作用仍不清楚。

方法

我们使用免疫荧光和免疫沉淀检测分别研究了 NRIP 与 AChR 相关蛋白的共定位和相互作用。在肌肉特异性 NRIP 敲除小鼠和 NRIP 敲除肌肉细胞（C2C12）中分析了 AChR 相关蛋白的结合亲和力。我们还从 43 名重症肌无力（MG）患者中收集了血清，MG 是一种 NMJ 疾病。使用 Western blot 和表位作图研究了血清中抗 NRIP 自身抗体的存在和特征。

结果

NRIP 在小鼠的腓肠肌中与 AChR、rapsyn 和 α-肌动蛋白 2（ACTN2）共定位；BTX 下拉实验显示 NRIP 与肌组织和细胞中的 rapsyn 和 ACTN2 复合物。NRIP 在体外和体内直接与 AChR 的α亚基（AChRα）结合，影响 AChR 与 rapsyn 和 rapsyn 与 ACTN2 的结合亲和力。在 43 名 MG 患者（年龄 58.4±14.5 岁；女性 55.8%）中，我们检测到其中 6 名（14.0%）患者存在抗 NRIP 自身抗体。当存在 AChR 自身抗体时，存在抗 NRIP 自身抗体与更严重的 MG 类型相关（P=0.011）。抗 NRIP 自身抗体滴度越高，MG 严重程度越严重（P=0.032）。主要免疫原性区域可能位于 NRIP 的 IQ 基序上。我们还显示了抗 NRIP 自身抗体的 IgG 亚类主要为 IgG1。