NRIP自身抗體在重症肌無力所扮演的角色

The Role of NRIP Autoantibodies in Myasthenia Gravis

陳亦欣(I-Hsin Chen)

指導教授 ： 陳小梨

國立臺灣大學/醫學院/微生物學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202003615

摘要

核受體交互作用蛋白 (Nuclear receptor interaction protein, NRIP)，是一種鈣離子依賴性的攜鈣素 (calmodulin) 結合蛋白，由860個胺基酸組成，具有7個WD40 domain和1個IQ domain。在實驗室先前的研究中，我們發現NRIP可以調節肌肉的收縮和再生。此外，NRIP在小鼠腓腸肌中與乙醯膽鹼受體 (acetylcholine receptors, AChR) 複合物共定位，其中乙醯膽鹼受體複合物包括輔肌動蛋白異構體 (α-actitin 2, ACTN2)，受體相連突觸蛋白 (rapsyn) 和AChR。而在本研究中，我們發現小鼠肌母細胞 (C2C12 cells) 中的內生性NRIP與內生性AChR彼此可有交互作用，從而進一步證實NRIP是AChR複合物在神經肌肉接合處 (neuromuscular junction, NMJ) 上的一個組成部分。
重症肌無力 (myasthenia gravis, MG) 是一種自體免疫疾病，其常見特徵是眼睛或骨骼肌的疲勞與無力。重症肌無力是由自身抗體攻擊NMJ的突觸後膜所引起，而在這項研究中，我們新發現了一種與MG相關的自身抗體，即NRIP自身抗體。我們使用西方墨點法 (Western blot) 對43名MG患者的血清進行了NRIP自身抗體檢測，發現了6例(14.0%)具有NRIP自身抗體的患者。我們還對NRIP自身抗體進行了抗原表位 (epitope) 分析，並確定了它們的主要免疫原性區域 (main immunogenic region, MIR) 可能位於NRIP之C端的IQ domain。此外，我們也分析了NRIP自身抗體的IgG亞類，發現它們主要由IgG1組成。為了了解NRIP自身抗體在MG中的角色，我們尚分析了MG患者的嚴重程度與NRIP自身抗體存在的相關性。我們發現，當AChR自身抗體存在時，若擁有NRIP自身抗體則會與更嚴重的MG有所關連。此外，MG嚴重程度會隨NRIP自身抗體的濃度上升而增加。綜上所述，NRIP自身抗體是一種新發現的MG相關自身抗體，其或可作為較嚴重型的MG之標誌。

關鍵字

核受體交互作用蛋白 ； 重症肌無力 ； 自身抗體 ； 抗原表位 ； IgG亞類

並列摘要

Nuclear receptor interaction protein (NRIP) is a Ca2+-dependent calmodulin binding protein, consisting of 860 amino acids, with 7 WD40 domains and 1 IQ motif. In our previous study, we found that NRIP can regulate muscle contraction and regeneration. NRIP colocalized with acetylcholine receptor (AChR) complex protein, including ACTN2, rapsyn, and AChR in gastrocnemius muscles of mice. In this study, we further demonstrated that endogenous NRIP can reciprocally interact with AChR in C2C12 cells, confirming that NRIP is a component of AChR complex at neuromuscular junction (NMJ).
Myasthenia gravis (MG) is an autoimmune disease, characterized by fatigue and weakness of ocular or skeletal muscles. MG is caused by autoantibodies against postsynaptic membrane of NMJ. In this study, we identified a novel MG-related autoantibody, NRIP autoantibody. We used Western blot to do NRIP autoantibodies test of the sera from 43 MG patients and found 6 patients (14.0%) having NRIP autoantibodies. We also performed epitope mapping of NRIP autoantibodies and found that their main immunogenic region is likely on the IQ motif of NRIP, which is on the NRIP-C terminal. In addition, we showed the IgG subclass of NRIP autoantibodies mainly to be IgG1. To understand the role of NRIP autoantibodies in MG, we also analyzed the correlation of MG severity and the presence of NRIP autoantibodies in patients with MG. We found that the presence of NRIP autoantibodies well correlated with a more severe form of MG when AChR autoantibodies existed. Besides, the higher the concentration of NRIP autoantibodies, the more severe MG severity. In conclusion, NRIP autoantibody is a newly identified MG-related autoantibody, which may be a biomarker of severe MG.

並列關鍵字

NRIP ； myasthenia gravis ； autoantibodies ； epitope ； IgG subclass

參考文獻

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