SOX9乙酰化与磷酸化交互作用调控Thy-1肾炎GMC增生的效应与机制

Human mesangial proliferative glomerulonephritis (MsPGN) is a disease with high incidence, and the abnormal proliferation of glomerular mesangial cells (GMC) leading to kidney fibrosis is a difficult problem in the medical research field all over the world. Our previous studies have found the proliferative reaction of GMC and the production of some proliferative cytokines (FGF1, PDGFα and TGFβ1) at the early stage of renal tissue in the rats with Thy-1 nephritis ( a model of MsPGN). Given that the transcriptional factor SOX9 and transcriptional coactivator GCN5 with acetyltransferase activity as well as protein kinase ERK1/2 were markedly co-upregulated both in the renal tissue of rat Thy-1 nephritis and in the GMC stimulated with sublytic C5b-9, and in order to elucidate the role and mechanism of some key molecules including post-translation modifications (PTMs) on GMC proliferation triggered by sublytic C5b-9, we attempt to explore the role of SOX9, and the cross-talk effect of acetylated SOX9 by GCN5 and phosphorylated SOX9 by ERK1/2 on the proliferation of GMC and the production of three proliferative cytokines(FGF1, PDGFα and TGFβ1). The purpose of the study is to reveal key molecules role and PTMs mechanism in the renal proliferative lesions of rats Thy-1 nephritis, and further to provide an important evidence for developing drugs and preventing or treating human MsPGN.

人类系膜增生性肾小球肾炎（MsPGN）发病率高，其肾小球系膜细胞（GMC）异常增生引发肾脏纤维化是医学界难题之一。我们发现，大鼠Thy-1肾炎（MsPGN模型）发病早期，肾组织中有GMC增殖反应和促增殖因子（FGF1、PDGFα和TGFβ1）的合成。鉴于转录因子SOX9和有乙酰转移酶活性的转录辅激活因子GCN5及蛋白激酶ERK1/2均是Thy-1肾炎大鼠肾组织和亚溶解型补体攻膜复合物（sublytic C5b-9）诱导GMC同期上调表达的基因，故为了研究sublytic C5b-9启动GMC增生关键分子的作用和翻译后修饰（PTMs）调控机制，本课题拟从体内外探讨SOX9的促增生效应和其同时被GCN5乙酰化及被ERK1/2磷酸化修饰后的交互作用及其对细胞增生和促增殖因子生成的影响，旨在为揭示Thy-1肾炎增生病变的关键分子和PTMs调控机制，并为研发靶向药物和防治人类MsPGN提供科学依据。

系膜增生性肾炎（MsPGN）属于人类常见的肾小球疾病，其病变特征是肾小球系膜细胞（GMC）过度增生和细胞外基质的异常积聚，且患者GMC表面可见补体C5b-9的沉积。大鼠Thy-1肾炎（Thy-1N）是MsPGN的动物模型，其病变具有亚溶解（sublytic）C5b-9的依赖性。用sublytic C5b-9体外刺激GMC后能诱导某些促增生因子的表达，但其促增生的机制尚未阐明。本研究利用Thy-1N大鼠和培养的GMC进行实验发现，Thy-1N大鼠肾组织及受sublytic C5b-9刺激的GMC中既见FGF1, PDGFα和Cyclin D1表达，又有转录因子SOX9、转录辅激活因子GCN5及蛋白激酶ERK1/2的表达与活化，且后三种表达时相均早于3种因子的产生。进一步机制研究揭示，sublytic C5b-9刺激的GMC，其SOX9能与FGF1、PDGFα和Cyclin D1基因启动子结合，且GCN5与SOX9结合后还能乙酰化SOX9第62位赖氨酸（K62），进而增加了前述因子的表达，导致GMC增生。同时，由sublytic C5b-9活化的ERK1/2也能与SOX9结合，介导其64和181位丝氨酸磷酸化，并提高GCN5表达促使SOX9乙酰化，两者共同作用增加了促增生因子的生成。此外，沉默肾内相应基因后不仅能抑制Thy-1N大鼠SOX9的磷酸化和乙酰化及促增生因子的产生，而且还可减轻GMC增生和尿蛋白的分泌。再者，MsPGN患者肾切片染色显示，GCN5、SOX9、FGF1、PDGFα和ERK1/2、Cyclin D1均呈阳性。综上结果表明，Thy-1N发病时，由sublytic C5b-9诱导GMC增生的机制涉及SOX9、GCN5及ERK1/2和促增生因子的共同参与，且与SOX9的乙酰化和磷酸化交互调控明显相关。这些研究成果为探讨大鼠Thy-1N和人类MsPGN的发病机制等提供了新的启示。