FBXO28/TRAF6复合物调控补体效应物致Thy-1肾炎大鼠GMC增生的机制研究

Human mesangial proliferative glomerulonephritis (MsPGN) is a disease with high incidence, which is histologically characterized by marked proliferation of glomerular mesangial cells (GMC). However, the mechanism of GMC proliferation in MsPGN remains unclear. It has been demonstrated that sublytic C5b-9 complex can trigger GMC proliferation. Our previous studies have revealed that the activation of ubiquitin ligase TRAF6, FBXO28（FBXO28 was found to form a complex with TRAF6), signaling molecule Erk8 and transcription factor Sp1/c-Myc as well as the ubiquitination of Erk8 were induced both in the renal tissues of Thy-1 nephritis rats (Thy-1N, a model of MsPGN) and in the GMC exposed to sublytic C5b-9. However the role of FBXO28/TRAF6 complex in the GMC proliferation of rats with Thy-1 nephritis has not been elucidated. Therefore, we attempt to explore the effects of FBXO28/TRAF6 complex-mediated Erk8 ubiquitination and the subsequent Sp1/c-Myc activation on the GMC proliferation induced by sublytic C5b-9 in Thy-1 nephritis and its mechanism. The purpose of this study is to reveal the key mechanism of GMC proliferation in rat Thy-1 nephritis, and further to provide new insights into preventing and treating human MsPGN.

人类系膜增生性肾炎（MsPGN）发病率高，其肾小球系膜细胞（GMC）增生病变是医学界难题之一。亚溶解型（sublytic）C5b-9作为疾病启动原可介导GMC增生。我们的研究发现，大鼠Thy-1肾炎（MsPGN模型）肾组织内和体外用sublytic C5b-9刺激GMC均可激活泛素酶TRAF6、FBXO28（为课题前期筛查到的一种可与TRAF6结合的分子）、信号分子Erk8和转录因子Sp1/c-Myc，并伴有Erk8的泛素化，但FBXO28/TRAF6复合物在大鼠Thy-1肾炎中调控sublytic C5b-9诱导GMC增生的作用并未阐明。因此，本研究拟探讨FBXO28/TRAF6复合物泛素化修饰Erk8调控Sp1/c-Myc活化在sublytic C5b-9引发的Thy-1肾炎GMC增生病变中的作用及机制。旨在揭示大鼠Thy-1肾炎GMC增生的关键靶标，进而为防治人类MsPGN提供依据。

人类系膜增生性肾炎（MsPGN）发病率高，其主要病理变化为肾小球系膜细胞（GMC）增殖和细胞外基质（ECM）积聚。业已发现，亚溶解型（sublytic）C5b-9作为疾病启动原可介导GMC增殖和ECM分泌，但其分子机制目前尚不清楚。我们的研究发现，大鼠Thy-1肾炎（MsPGN模型）肾组织内和体外用sublytic C5b-9刺激的大鼠GMC中泛素酶（FBXO28、TRAF6）、转录因子MZF1和增殖相关基因RGC-32的表达显著上调，信号分子ERK5的磷酸化亦明显增强。体外沉默或敲除上述基因均可显著抑制由sublytic C5b-9诱导的大鼠GMC增殖和ECM分泌。进一步研究揭示，由sublytic C5b-9刺激大鼠GMC后上调的FBXO28和TRAF6形成复合物，FBXO28/TRAF6复合物与ERK5结合后促进ERK5的多聚泛素化（K63位）和磷酸化修饰，活化后的ERK5再通过上调转录因子MZF1启动靶基因RGC-32的转录与表达。体内实验表明，沉默大鼠肾组织中的FBXO28、TRAF6、ERK5、MZF1和RGC-32基因可减轻大鼠Thy-1肾炎GMC增殖和ECM积聚以及尿蛋白分泌水平。上述这些实验结果提示，sublytic C5b-9刺激Thy-1肾炎大鼠GMC后，通过上调FBXO28和TRAF6的表达以及FBXO28/TRAF6复合物的形成促进ERK5/MZF1/RGC-32通路的活化，诱导GMC的增生病变。本研究揭示了大鼠Thy-1肾炎GMC增生的相关调控机制，为防治人类MsPGN提供了潜在的分子靶标。