Musai Jon, Jayaraman Sahana, Pak Katherine, Pinal-Fernandez Iago, Muñoz-Braceras Sandra, Casal-Dominguez Maria, Cho Eric, Fitisemanu Fa'alataitaua M, Burbelo Peter D, Kaplan Mariana J, Warner Blake M, Schiffenbauer Adam I, Selva-O'Callaghan Albert, Milisenda José César, Rider Lisa G, Larman H Benjamin, Mammen Andrew L
Muscle Disease Section, National Institute of Arthritis and Musculoskeletal and Skin Disease, National Institutes of Health, Bethesda, MD, USA.
Johns Hopkins University School of Medicine, Baltimore, MD, USA.
bioRxiv. 2025 Jan 19:2025.01.15.633218. doi: 10.1101/2025.01.15.633218.
In dermatomyositis patients with anti-Mi2 autoantibodies, autoantibodies can enter muscle cells, leading to the aberrant expression of genes normally repressed by the Mi2/nucleosome remodeling and deacetylation (NuRD) complex. However, the mechanism by which autoantibodies interfere with Mi2/NuRD function remains unclear. This study aimed to identify additional autoantibodies in anti-Mi2-positive patients as well as the specific epitopes recognized by anti-Mi2 and any novel autoantibodies.
Phage ImmunoPrecipitation Sequencing (PhIP-Seq) was used to screen serum samples from anti-Mi2-positive myositis patients for autoantibodies. Enzyme-linked immunosorbent assays (ELISA) and luciferase immunoprecipitation system (LIPS) immunoassays were used to detect autoantibodies in serum samples from myositis patients and healthy controls.
PhIP-Seq identified autoantibodies recognizing the autoimmune regulator (AIRE) in sera from anti-Mi2 autoantibody-positive patients. Both anti-AIRE and anti-Mi2 autoantibodies predominantly recognized a homologous region of the plant homeodomain zinc finger type I (PHD1), which is critical for AIRE and Mi2/NuRD function. ELISA and LIPS testing showed that anti-Mi2 autoantibody-positive patients were positive for anti-AIRE autoantibodies, while AIRE reactivity was largely absent in healthy comparators, anti-Mi2 autoantibody-negative-myositis, and other autoimmune diseases. Affinity-purified anti-Mi2 autoantibodies recognized both Mi2 and AIRE by ELISA, whereas anti-Mi2-depleted immunoglobulin fractions did not recognize either protein.
Autoantibodies recognizing Mi2 also recognize AIRE at a homologous PHD1 finger. This region is required by the Mi2/NuRD complex to anchor the nucleosome and consequently repress gene expression. Our findings suggest that anti-Mi2 autoantibodies disrupt NuRD complex function by binding to the PHD1 domain. Further studies are needed to determine if anti-Mi2 autoantibodies bind other PHD1-containing proteins and their functional implications.
在患有抗Mi2自身抗体的皮肌炎患者中，自身抗体可进入肌肉细胞，导致通常由Mi2/核小体重塑和去乙酰化（NuRD）复合物抑制的基因异常表达。然而，自身抗体干扰Mi2/NuRD功能的机制仍不清楚。本研究旨在鉴定抗Mi2阳性患者中的其他自身抗体，以及抗Mi2和任何新的自身抗体所识别的特定表位。
采用噬菌体免疫沉淀测序（PhIP-Seq）技术，从抗Mi2阳性肌炎患者的血清样本中筛选自身抗体。采用酶联免疫吸附测定（ELISA）和荧光素酶免疫沉淀系统（LIPS）免疫测定法，检测肌炎患者和健康对照者血清样本中的自身抗体。
PhIP-Seq在抗Mi2自身抗体阳性患者的血清中鉴定出识别自身免疫调节因子（AIRE）的自身抗体。抗AIRE和抗Mi2自身抗体主要识别I型植物同源结构域锌指（PHD1）的同源区域，该区域对AIRE和Mi2/NuRD功能至关重要。ELISA和LIPS检测显示，抗Mi2自身抗体阳性患者的抗AIRE自身抗体呈阳性，而在健康对照者、抗Mi2自身抗体阴性的肌炎患者和其他自身免疫性疾病中，AIRE反应性基本不存在。亲和纯化的抗Mi2自身抗体通过ELISA可识别Mi2和AIRE，而去除抗Mi2的免疫球蛋白组分则不能识别这两种蛋白。
识别Mi2的自身抗体在同源的PHD1指处也识别AIRE。Mi2/NuRD复合物需要该区域来锚定核小体，从而抑制基因表达。我们的研究结果表明，抗Mi2自身抗体通过与PHD1结构域结合来破坏NuRD复合物的功能。需要进一步研究以确定抗Mi2自身抗体是否结合其他含PHD1的蛋白及其功能意义。
