The soluble urokinase plasminogen activator receptor (suPAR) has been implicated in the pathogenesis of kidney diseases including primary and recurrent focal and segmental glomerulosclerosis (FSGS), diabetic nephropathy, and acute kidney injuries (AKI). Elevated serum suPAR concentration is a negative prognostic indicator in multiple critical clinical conditions. This study has examined the initial transduction steps used by suPAR in cultured mouse podocytes. We now report that the receptor for advanced glycation end-products (RAGE) co-immunoprecipitates with αV and β3 integrin subunits, which have been previously shown to initiate suPAR signal transduction at the podocyte cell surface. siRNA knock-down of RAGE attenuated Src phosphorylation evoked by either suPAR or by glycated albumin (AGE-BSA), a prototypical RAGE agonist. suPAR effects on Src phosphorylation were also blocked by the structurally dissimilar RAGE antagonists FPS-ZM1 and azeliragon, as well as by cilengitide, an inhibitor of outside-in signaling through αV-integrins. FPS-ZM1 also blocked Src phosphorylation evoked by AGE-BSA. FPS-ZM1 blocked increases in cell surface TRPC6 abundance, cytosolic reactive oxygen species (ROS) and activation of the small GTPase Rac1 evoked by either suPAR or AGE-BSA. In addition, FPS-ZM1 inhibited Src phosphorylation evoked by serum collected from a patient with recurrent FSGS during a relapse. The magnitude of this inhibition was indistinguishable from the effect produced by a neutralizing antibody against suPAR. These data suggest that orally bioavailable small molecule RAGE antagonists could represent a useful therapeutic strategy for a wide range of clinical conditions associated with elevated serum suPAR, including primary FSGS and AKI.

可溶性尿激酶纤溶酶原激活物受体 (suPAR) 与肾脏疾病的发病机制有关，包括原发性和复发性局灶节段性肾小球硬化 (FSGS)、糖尿病肾病和急性肾损伤 (AKI)。升高的血清 suPAR 浓度是多种关键临床条件下的阴性预后指标。本研究检查了 suPAR 在培养的小鼠足细胞中使用的初始转导步骤。我们现在报道晚期糖基化终产物受体 (RAGE) 与 αV 和 β3 整合素亚基共免疫沉淀，先前已显示其在足细胞表面启动 suPAR 信号转导。RAGE 的 siRNA 敲低减弱了由 suPAR 或由典型的 RAGE 激动剂糖化白蛋白 (AGE-BSA) 引起的 Src 磷酸化。suPAR 对 Src 磷酸化的影响也被结构不同的 RAGE 拮抗剂 FPS-ZM1 和 azeliragon 以及西仑吉肽（一种通过 αV-整合素的由外向内信号传导的抑制剂）阻断。FPS-ZM1 还阻断了由 AGE-BSA 引起的 Src 磷酸化。FPS-ZM1 阻止了 suPAR 或 AGE-BSA 引起的细胞表面 TRPC6 丰度、细胞溶质活性氧 (ROS) 和小 GTPase Rac1 激活的增加。此外，FPS-ZM1 抑制了在复发期间从复发性 FSGS 患者收集的血清引起的 Src 磷酸化。这种抑制的幅度与针对 suPAR 的中和抗体产生的效果无法区分。