原发性局灶节段性肾小球硬化(FSGS)是构成难治性原发性肾病综合征的主要类型，其发病机制尚未阐明。已发现患者血中的可溶性尿激酶受体(suPAR)通过与足细胞足突裂隙膜复合物的整合素β3结合、激活并通过细胞内信号转导导致足细胞病变而引起发病。但目前尚不清楚是suPAR是否还能通过结合足突在基底膜上的锚着蛋白整合素β1参与发病。本研究使用SiRNA敲低uPAR和整合素基因表达的细胞及使用基因敲除动物，以及高亲和力的小分子短肽阻断suPAR的功能结构域，包括使用核素标记的microPET活体示踪技术进一步观察在同一动物体内随疾病发生发展，suPAR表达，与整合素β3及β1的结合能力、对足突裂隙膜的组成蛋白及足细胞内信号转导的变化，为今后的治疗新思路提供重要依据。

Focal segmental glomerulosclerosis (FSGS) is an important cause of steroid-resistant nephrotic syndrome in both children and adults. The etiology and pathophysiology of primary FSGS is still unclear. Recent studies have discovered that the urokinase plasminogen activator receptor, uPAR (CD87) and soluble urokinase receptor in circulation may play a crucial role in FSGS mainly through its ability to form signaling complexes with other transmembrane proteins such as integrins. Podocyte anchored to the glomerular basement membrane by a3β1, expressing a5β3 integrin in slit diaphragm complex between foot processes. Moreover, they showed that circulating suPAR activated podocyte β3 integrin, causing foot process effacement, proteinuria, and a histological picture consistent with FSGS. suPAR represents the soluble form of the urokinase type plasminogen activator receptor (uPAR), which is a glycosyl-phosphatidylinositol (GPI)-anchored three-domain membrane protein that can bind to several ligands. Our previous work revealed that suPAR level associated with progression and outcome of FSGS, and addressed the interaction between uPAR and integrin β1. Our hereby proposal will continue to study on mechanism of uPAR and integrin interaction for pathogenesis of podocyte injury. By in vitro and in vivo studies performed on model of Puromycin Aminonucleoside and Adriamycin induced nephropathy for podocyte injury. To accomplish the objective, we knock down the activity of PLAUR and ITGβ3 gene in podocytes. Using a high affinity uPAR peptide antagonist AE105 to specifically block the binding domain of uPAR to integrins, We will demonstrate that down regulate the binding ability of uPAR domain to integrins in podocytes could restore the of slit diaphragm proteins and cytoskeleton structure in vitro via ERK/AKT phosphorylation pathway. To quantitatively in vivo assess expression level of uPAR and interaction with integrins in podocyte, and cell migrations by using a high affinity uPAR peptide antagonist AE105 conjugated with DOTA and labeled with 64Cu (64Cu-DOTA-AE105), detected by micro PET performed in three knock-out animal FSGS models (PLAUR-/-,ITG β1-/-, ITGβ3-/-). The innovations of this proposal are that clarifying the interaction domain between uPAR and integrin β1/β3, and intend to explore the mechanism of uPAR in podocytopathy and Better understanding of the mechanisms of suPAR in podocytes injury may provide new clues for prevention and treatment of glomerulosclerosis.