狼疮肾炎（LN）是我国最常见的继发性肾小球疾病，仍缺乏特异性治疗，15-35%的患者对激素联合免疫抑制剂治疗无效（NR），增加不良预后的风险。我们前期的研究利用NR患者白细胞和肾组织通过核糖体印迹测序、生物信息学分析及体外实验筛选出小肽RLN，并发现：①RLN蛋白在LN患者白细胞及小鼠肾组织中高表达；②敲除RLN基因可改善小鼠LN的进展；③LN患者白细胞和小鼠LN肾脏检测到RLN Ser41高磷酸化水平；④NR患者血清可促进人系膜细胞RLN Ser41磷酸化，RLN S41/A点突变可显著降低NR患者血清对人系膜细胞的增生促进作用。我们推测，RLN是促进LN发生和发展的重要分子，RLN通过Ser41 的磷酸化而发挥其生物学功能。本项目拟通过阻断RLN联合免疫抑制剂探讨RLN是否是治疗LN的潜在新靶点，利用RLN S41/A点突变小鼠探讨其分子机制，为LN的治疗提供新的潜在药物作用靶点。

Lupus nephritis (LN) is the leading cause of secondary glomerulonephritis in China. 15-35% patients with LN have no response to combination therapy (Steroid + immunosuppressive reagents) and will progress to end-stage renal disease within 10 years. Currently we still lack the specific treatments to LN. To address this major unmet clinical need, we performed a Ribosome Profiling to analyse mRNA expression, Parallel reaction monitoring (PRM)-based targeted mass spectrometry to do qualitative and quantitative analysis of protein expression and bioinformatics screen in human LN peripheral white blood cells. We have identified a RNA transcript which contains a short 198 nucleotide open reading frame which encodes a highly conserved 66 amino acid peptide which we have named Regulator of Lupus Nephritis (RLN). We also performed RT-qPCR to corroborate RLN expression in LN kidney tissue samples. We made an antibody to this peptide and confirmed up-regulation of RLN in human and experimental LN. Next, we created RLN deficient (MRL/lpr;RLN-/-) mice and showed them to be substantially protected from LN. Our in vitro functional studies identified that RLN is regulated by phosphorylation (at Ser41). Western blotting identified RLN S41 phosphorylation in peripheral white blood cells in patients with LN and in progressive LN in MRL/lpr mice. We have created mice with single amino acid mutation in RLN (RLNS41/A mice) to prevent phosphorylation. Thus, we hypothesize that: (i) RLN is a novel regulator of LN, and; (ii) the biological actions of RLN depend upon its phosphorylation at Ser41. .AIMS OF STUDY.1. To determine whether the combination of complete blockade of RLN (RLN-/-) and current therapy drugs is superior to a single blockade in the development and progression of mouse LN in MRL/lpr mice..2. To investigate the molecular mechanisms by which RLN S41 phosphorylation coordinates its biological actions..OUTCOMES AND SIGNIFICANCE .This project is based upon the screening of clinical specimens to identify novel molecules involved in progressive LN. Up-regulation of RLN in mouse kidney disease validates these models for pre-clinical studies of the therapeutic potential of RLN blockade. We are testing a novel concept that RLN promotes progressive LN through its phosphorylation at Ser41..INNOVATION AND OUTCOMES.1. Investigation of a major new regulator of LN using a suite of unique reagents..2. A major advance in our understanding of development and progression of LN.