MAD2B-mediated SnoN downregulation is implicated in fibroblast activation and tubulointerstitial fibrosis
MAD2B-mediated SnoN downregulation is implicated in fibroblast activation and tubulointerstitial fibrosis
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MAD2B 介导的 SnoN 下调与成纤维细胞活化和肾小管间质纤维化有关
DOI：
10.1152/ajprenal.00600.2015
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发表时间：
2016-07-01
影响因子：
4.2
通讯作者：
Zhang, Chun
中科院分区：
文献类型：
--
作者：
Tang, Hui;Su, Hua;Zhang, Chun
MAD 2B是一种后期促进复合物/环体（APC/C）抑制剂，是DNA聚合酶zeta的一个小亚基，在有丝分裂检查点控制和DNA修复中起着不可或缺的作用。以前，我们确定MAD 2B在肾小球和肾小管间质中表达，并参与高糖诱导的足细胞损伤。然而，它在其他肾脏疾病中的作用仍然难以捉摸。在本研究中，我们的目的是说明MAD 2B在肾纤维化发病机制中的潜在作用。免疫荧光和Western blotting检测发现MAD 2B在肾小管间质纤维化（TIF）和单侧输尿管梗阻（UUO）小鼠中表达明显增加。广泛认为，在TIF期间，常驻成纤维细胞是产生胶原的肌成纤维细胞的主要来源。因此，我们通过免疫印迹法评估了暴露于转化生长因子（TGF）-β 1的成纤维细胞（NRK-49 F）中的MAD 2B水平，并显示MAD 2B以时间依赖性方式上调。有趣的是，SnoN，TGF-β 1/Smad信号通路的转录抑制因子，在TGF-β 1处理的成纤维细胞以及TIF患者和UUO小鼠的肾皮质中减少。无论是在体外还是在体内，通过慢病毒转染的MAD 2B的局部遗传消耗可以保持SnoN丰度并抑制Smad 3磷酸化，这最终抑制成纤维细胞活化、ECM积累并减轻TIF的严重性。然而，泛素连接酶APC/C不参与MAD 2B介导的SnoN下降，尽管该过程是泛素化依赖的。总之，我们的观察结果表明，除了细胞周期管理，MAD 2B在成纤维细胞活化和TIF过程中通过抑制SnoN表达具有促纤维化作用。靶向MAD 2B-SnoN通路是TIF的有希望的干预措施。
MAD2B, an anaphase-promoting complex/cyclosome (APC/C) inhibitor and a small subunit of DNA polymerase zeta, is indispensible for mitotic checkpoint control and DNA repair. Previously, we established that MAD2B is expressed in glomerular and tubulointerstitial compartments and participates in high glucose-induced podocyte injury. However, its role in other renal diseases remains elusive. In the present study, we aim to illustrate the potential role of MAD2B in the pathogenesis of renal fibrosis. By immunofluorescence and Western blotting, we found MAD2B expression is obviously increased in tubulointerstitial fibrosis (TIF) patients and unilateral ureteral obstruction (UUO) mice. It is widely accepted that resident fibroblasts are the major source of collagen-producing myofibroblasts during TIF. Therefore, we evaluated the level of MAD2B in fibroblasts (NRK-49F) exposed to transforming growth factor (TGF)-beta 1 by immunoblotting and revealed that MAD2B is upregulated in a time-dependent manner. Intriguingly, SnoN, a transcriptional repressor of the TGF-beta 1/Smad signaling pathway, is decreased in TGF-beta 1-treated fibroblasts as well as the kidney cortex from TIF patients and UUO mice. Either in vitro or in vivo, local genetic depletion of MAD2B by lentiviral transfection could preserve SnoN abundance and suppress Smad3 phosphorylation, which finally dampens fibroblast activation, ECM accumulation, and alleviates the severity of TIF. However, the ubiquitin ligase APC/C is not involved in the MAD2B-mediated SnoN decline, although this process is ubiquitination dependent. In conclusion, our observation proposes that besides cell cycle management, MAD2B has a profibrotic role during fibroblast activation and TIF by suppressing SnoN expression. Targeting the MAD2B-SnoN pathway is a promising intervention for TIF.