LINE1-ORF0 in SLE pathogenesis

项目概要/摘要 系统性红斑狼疮（SLE）是一种多系统自身免疫性疾病， 干扰素（IFN）信号传导和高滴度自身抗体导致免疫介导的组织损伤。异常 逆转录转座子（一种转座因子）产生的核酸积累与 以持续产生IFN-I为特征的疾病，如SLE。特别是，非- LTR LINE 1（L1）家族在SLE患者中被激活。最近发现， 由L1编码的RNA结合蛋白（ORF 1 p）和ORF 2 p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 集中于最近发现的在L1 5 'UTR中的反义开放阅读框（ORF）的研究， 称为ORF 0。ORF 0编码71个氨基酸残基的小核蛋白（ORF 0 p），其增加了 L1移动性ORF 0具有几个独特的特征，这可能对潜在的机制具有重要意义。 L1在SLE发病机制中的作用。首先，能够编码全长ORF 0 p的ORF 0位点的数目（~781 基因座）比ORF 1和ORF 2高约8-10倍（约80-100个活性拷贝）。因此，在L1激活的设置中， 例如在SLE中，预期ORF 0 p的抗原负荷将比ORF 1 p和ORF 2 p更稳健。 第二，ORF 0具有两个突出的剪接供体位点，其与下游的剪接受体协同作用。 基因组序列，产生ORF 0 p-融合蛋白。也就是说，“宿主”蛋白质的N-末端将是 被ORF 0 p N-末端序列取代，产生杂合蛋白。基于这一前提，我们的中央 一种假设是SLE中L1激活导致ORF 0失调，这驱动了抗ORF 0 p的产生 抗体和杂合ORF 0 p融合蛋白的异常表达，产生靶向 SLE。事实上，我们的初步研究表明ORF 0 p是SLE的自身抗原。这个项目的主要目标是 探索性/发展性研究补助金的目的是研究抗ORF 0 p抗体在 SLE患者存在ORF 0 p-宿主融合蛋白异常表达的假设 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.