LINE1-ORF0 in SLE pathogenesis

项目摘要/摘要 系统性红斑狼疮(SLE)是一种以持续性为特征的多系统自身免疫性疾病 干扰素信号和高滴度自身抗体导致免疫介导的组织损伤。一个不正常的人 反转录转座子是一类转座元件，它的核酸积累与此有关 对以持续产生干扰素-I为特征的疾病，如系统性红斑狼疮。尤其是非基因的反转录转座子 LTRLINE1(L1)家族在系统性红斑狼疮患者中被激活。最近，人们发现， L1s编码的RNA结合蛋白(ORF1p)和ORF2p核酸内切酶/逆转录酶是SLE 自身抗原，支持L1元件可能在SLE发病机制中发挥作用的观点。这项建议是 重点研究了最近在L15‘UTR中发现的反义开放阅读框架(ORF)， 命名为ORF0。ORF0编码71个氨基酸残基的小核蛋白(ORF0p)，它增加了 L1移动性。ORF0有几个独特的特征，这可能对潜在的机制有关键的影响 L1s在SLE发病机制中的作用首先，能够编码全长ORF0p(~781)的ORF0基因座的数量 基因座)比ORF1和ORF2(约80-100个活跃拷贝)高出约8-10倍。因此，在L1激活的设置中， 例如在SLE中，预计ORF0p的抗原性将比ORF1p和ORF2p更强。 其次，ORF0有两个突出的剪接供体部位，它们与下游的剪接受体协同作用 基因组序列，产生ORF0p-融合蛋白。这就是说，“宿主”蛋白的N端是 被ORF0p N-末端序列取代，产生杂交蛋白。基于这个前提，我们中央 假设SLE中L1的激活导致ORF0的失调，从而驱动抗ORF0p的产生 抗体和杂交ORF0p融合蛋白的异常表达，产生靶向于 SLE。事实上，我们的初步研究表明，ORF0p是SLE的一种自身抗原。这一行动的主要目标是 探索性/发展性研究资助金用于研究抗ORF0p抗体在儿童中的临床意义 并解决SLE患者存在ORF0p-宿主融合异常产生的假设 含有狼疮自身抗原的蛋白质。

PROJECT SUMMARY/ABSTRACT Systemic lupus erythematosus (SLE) is a multisystemic autoimmune disease characterized by sustained interferon (IFN) signaling and high titer autoantibodies leading to immune-mediated tissue damage. An abnormal accumulation of nucleic acids derived from retrotransposons, a class of transposable element, has been linked to diseases characterized by sustained IFN-I production, such as SLE. In particular, retrotransposons of the non- LTR LINE1 (L1) family have been shown to be activated in patients with SLE. More recently, it was found that the RNA-binding protein (ORF1p) and the ORF2p endonuclease/reverse transcriptase encoded by L1s are SLE autoantigens, supporting the notion that L1 elements may play a role in SLE pathogenesis. This proposal is focused on the study of a recently discovered antisense open reading frame (ORF) found in the L1 5’UTR, termed ORF0. ORF0 encodes for a small nuclear protein (ORF0p) of 71 amino acid residues, which increases L1 mobility. ORF0 has several unique features, which may have critical implications on the potential mechanistic role of L1s in SLE pathogenesis. First, the number of ORF0 loci capable of encoding full-length ORF0p (~781 loci) is ~8-10 times higher than ORF1 and ORF2 (~80–100 active copies). Thus, in the setting of L1 activation, such as in SLE, it is expected that the antigenic load of ORF0p would be more robust than ORF1p and ORF2p. Second, ORF0 has two prominent splice donor sites that act in concert with splice acceptors in downstream genomic sequences, generating ORF0p-fusion proteins. This is, the N-terminus of the “host” protein would be replaced by the ORF0p N-terminal sequence, producing hybrid proteins. Based on this premise, our central hypothesis is that L1 activation in SLE leads to ORF0 dysregulation, which drives the production of anti-ORF0p antibodies and an abnormal expression of hybrid ORF0p-fusion proteins, generating neoantigens targeted in SLE. Indeed, our preliminary studies demonstrate that ORF0p is an autoantigen in SLE. The major goal of this exploratory/developmental research grant is to investigate the clinical significance of anti-ORF0p antibodies in SLE and to address the hypothesis that patients with SLE have an abnormal production of ORF0p-host fusion proteins containing lupus autoantigens.