The Role of Interleukin-15 Receptor-alpha Variants in the Pathogenesis of FSGS

摘要 局灶性节段性肾小球硬化(FSGS)是一种以激素为特征的临床病理诊断 难治性肾病综合征(NS)，肾小球毛细血管簇局灶性瘢痕形成，进展迅速 肾病分期(ESKD)。在过去的三年里，FSGS的发病率增加了10倍以上 几十年来，这种疾病在非裔美国人(AA)人口中高度流行。事实上，美国汽车协会占了 40%的ESKD病例是由FSGS引起的，尽管只占总人口的13%。 FSGS是目前最常见的引起ESKD的原发肾小球疾病。它的一个特点是 疾病是指肾小球足细胞数量减少。因此，足细胞被认为起着关键作用 在FSGS的发病机制中起重要作用。 对家族形式的FSGS的研究为疾病过程提供了关键的见解。这些研究 已经确定了30多个基因的突变，这些基因富含在肾小球足细胞中。这些基因的突变 尽管在AA人群中进展为ESKD的风险很高，但在AA中是罕见的。我们的实验室有 收集了30多个常染色体显性遗传FSGS的AA家系。使用这个独特的资源，我已经确定了一个 白介素15受体α(IL-15RαK47R)中罕见的杂合性错义变体是唯一 在常染色体显性遗传FSGS的AA家系中与疾病分离。该变量出现在 高亲和力的“寿司”受体的配基结合域，并被预测为破坏SIFT和 多酚分析。为了支持突变的破坏作用，我们发现IL-15RαK47R点 突变会损害IL-15诱导的生存信号。根据这些初步数据，我假设 IL-15RαK47R是一种亚型、功能丧失的变体，它促进受损的生存信号，导致 足细胞凋亡。为了验证这一假设，我们提出了3个具体目标： 1.确定IL-15RαK47R变异体对足细胞促生存信号的影响 2.鉴定IL-15Rα缺陷小鼠的肾脏表型，以及 3.确定IL-15Rα罕见变异在本组AA合并FSGS患者中的患病率。 拟议中的实验将对FSGS的分子发病机制产生深刻的见解，并可能揭示 新的治疗靶点。 在这个奖项的任期内，我希望在用小鼠建立人类肾小球疾病模型方面开发新的技能 并生成提交独立调查员奖所需的数据，重点是确定 FSGS的分子发病机制。我这项提议的导师罗伯特·斯珀尼博士是该领域的领军人物 在细胞生物学和整体动物建模方面有丰富的经验，并作为研究导师具有丰富的经验。而且，我的 导师团队，我在生化和肾脏病方面的经验，以及杜克独特的训练环境 大学使我处于独特的地位，能够实现这项提议中概述的科学目标。

ABSTRACT Focal segmental glomerulosclerosis (FSGS) is a clinical-pathologic diagnosis characterized by steroid resistant nephrotic syndrome (NS), focal scarring of the glomerular capillary tuft and rapid progression to end stage kidney disease (ESKD). The incidence of FSGS has increased more than 10-fold over the past three decades and the disease is highly prevalent in the African Americans (AA) population. Indeed, AAs account for 40% of all cases of ESKD due to FSGS despite comprising only 13% of the general population. FSGS is now the most common primary glomerular disorder causing ESKD. A characteristic feature of the disease is a reduced number of glomerular podocytes. As a result, podocytes are thought to play a pivotal role in the pathogenesis of FSGS. The study of familial forms of FSGS has provided key insights into the disease process. These studies have identified mutations in over 30 genes that are enriched in glomerular podocytes. Mutations in these genes are rare in AAs despite the high risk for progression to ESKD in the AA population. Our laboratory has collected over 30 AA kindreds with autosomal dominant FSGS. Using this unique resource, I have identified a rare heterozygous missense variant in the interleukin-15 receptor-α (IL-15RαK47R) as the only variant that segregates with the disease in an AA kindred with autosomal dominant FSGS. The variant occurs within the high-affinity “sushi” ligand binding domain of the receptor and is predicted to be damaging by SIFT and polyphen analyses. In support of a damaging effect of the mutation, we found that the IL-15RαK47R point mutation impairs IL-15-induced prosuvival signaling. Based on these preliminary data, I hypothesize that the IL-15RαK47R is a hypomorphic, loss-of-function variant that promotes impaired prosurvival signaling, resulting in podocyte apoptosis. To investigate this hypothesis, 3 specific aims are proposed: 1. Determine the effect of the IL-15Rα K47R variant on podocyte pro-survival signaling 2. Characterize the renal phenotype of the IL-15Rα-deficient mouse, and 3. Determine the prevalence of rare variants in IL-15Rα in our cohort of AA patients with FSGS. The proposed experiments will generate insights into the molecular pathogenesis of FSGS and may uncover novel therapeutic targets. Over the term of this award, I hope to develop new skills in human glomerular disease modeling in mice and to generate the data necessary for submission of an independent investigator award focused on defining the molecular pathogenesis of FSGS. My mentor for this proposal, Dr. Robert Spurney, is a leader in the field of cell biology and whole animal modeling and has extensive experience as a research mentor. Moreover, my mentor team, my experience in biochemistry and Nephrology, and the unique training environment of Duke University uniquely positions me to achieve the scientific objectives outlined in this proposal.