Department of Health Sciences, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; Office of the Saskatchewan Multiple Sclerosis Clinical Research Chair, University of Saskatchewan, Saskatoon, SK S7K 0M7, Canada; Cameco MS Neuroscience Research Centre, College of Medicine, University of Saskatchewan, Saskatoon, SK S7K 0M7, Canada.
Office of the Saskatchewan Multiple Sclerosis Clinical Research Chair, University of Saskatchewan, Saskatoon, SK S7K 0M7, Canada; Cameco MS Neuroscience Research Centre, College of Medicine, University of Saskatchewan, Saskatoon, SK S7K 0M7, Canada; Neurology Division, Department of Medicine, University of Saskatchewan, Saskatoon, SK S7N 0X8, Canada.
Neurobiol Dis. 2022 Aug;170:105775. doi: 10.1016/j.nbd.2022.105775. Epub 2022 May 23.
Neurodegeneration, the progressive loss or damage to neurons and axons, underlies permanent disability in multiple sclerosis (MS); yet its mechanisms are incompletely understood. Recent data indicates autoimmunity to several intraneuronal antigens, including the RNA binding protein (RBP) heterogenous nuclear ribonucleoprotein A1 (hnRNP A1), as contributors to neurodegeneration. We previously showed that addition of anti-hnRNP A1 antibodies, which target the same immunodominant domain of MS IgG, to mice with experimental autoimmune encephalomyelitis (EAE) worsened disease and resulted in an exacerbation of hnRNP A1 dysfunction including cytoplasmic mislocalization of hnRNP A1, stress granule (SG) formation and neurodegeneration in the chronic stages of disease. Because this previous study focused on a singular timepoint during EAE, it is unclear whether anti-hnRNP A1 antibody induced hnRNP A1 dysfunction caused neurodegeneration or was result of it. In the present study, we analyzed in vivo and in vitro models of anti-hnRNP A1 antibody-mediated autoimmunity for markers of hnRNP A1 dysfunction and neurodegeneration over a time course to gain a better understanding of the connection between hnRNP A1 dysfunction and neurodegeneration. Anti-hnRNP A1 antibody treatment resulted in increased neuronal hnRNP A1 mislocalization and nuclear depletion temporally followed by altered RNA expression and SG formation, and lastly an increase in necroptotic signalling and neuronal cell death. Treatment with necrostatin-1s inhibited necroptosis and partially rescued anti-hnRNP A1 antibody-mediated neurodegeneration while clathrin knockdown specifically inhibited anti-hnRNP A1 antibody uptake into neurons. This data identifies a novel antibody-mediated mechanism of neurodegeneration, which may be targeted to inhibit neurodegeneration and prevent permanent neurological decline in persons living with MS.
神经退行性变，即神经元和轴突的进行性丧失或损伤，是多发性硬化症（MS）导致永久性残疾的基础；但其机制尚不完全清楚。最近的数据表明，针对包括 RNA 结合蛋白（RBP）异质性核核糖核蛋白 A1（hnRNP A1）在内的多种神经元内抗原的自身免疫是神经退行性变的原因之一。我们之前的研究表明，在实验性自身免疫性脑脊髓炎（EAE）小鼠中加入针对 MS IgG 相同免疫显性结构域的抗 hnRNP A1 抗体，会加重疾病并导致 hnRNP A1 功能障碍恶化，包括 hnRNP A1 细胞质定位异常、应激颗粒（SG）形成和疾病慢性阶段的神经退行性变。由于之前的研究主要集中在 EAE 的单一时间点，因此尚不清楚抗 hnRNP A1 抗体诱导的 hnRNP A1 功能障碍是否导致了神经退行性变，还是其结果。在本研究中，我们分析了体内和体外抗 hnRNP A1 抗体介导的自身免疫模型，以研究 hnRNP A1 功能障碍和神经退行性变的标志物随时间的变化，以更好地理解 hnRNP A1 功能障碍与神经退行性变之间的联系。抗 hnRNP A1 抗体治疗导致神经元 hnRNP A1 定位异常增加，核内 hnRNP A1 耗竭，随后 RNA 表达改变和 SG 形成，最后坏死性凋亡信号增加和神经元细胞死亡。使用 necrostatin-1s 抑制坏死性凋亡可部分挽救抗 hnRNP A1 抗体介导的神经退行性变，而网格蛋白敲低则特异性抑制抗 hnRNP A1 抗体进入神经元。该数据确定了一种新的抗体介导的神经退行性变机制，该机制可能成为抑制神经退行性变和防止多发性硬化症患者永久性神经衰退的靶点。
