Liu Shuxin, Xie Yuansheng, Lv Yang, Qin Fufang, Fu Bo, Shi Suozhu, Yin Zhong, Hong Quan, Zhang Xueguang, Wang Jianzhong, Chang Ming, Chen Xiangmei
Institute of Nephrology, Chinese PLA General Hospital, Beijing, PR China.
Am J Nephrol. 2010;32(5):447-55. doi: 10.1159/000320334. Epub 2010 Oct 6.
BACKGROUND/AIMS: Mizoribine (MZR) can inhibit mesangial cell (MC) proliferation, but the mechanism remains unknown. In this study, we investigated the inhibitory effect of MZR on MC proliferation via a cell cycle regulatory protein-dependent mechanism.
We investigated the effect of MZR on MC proliferation and expression of cell cycle regulatory proteins such as cyclin D1, cyclin-dependent kinase 2 and p27(kip1) in primary cultured rat MCs. We further focused on analyzing the effects of MZR on S phase kinase-associated protein 2 (Skp2), which played a crucial role in p27(kip1) degradation.
MZR effectively inhibited MC proliferation in primary cultured rat MCs, reduced the expression of cyclin D1 and cyclin-dependent kinase 2, while it dramatically increased the protein level of p27(kip1), maintained the nucleus location of p27(kip1) and induced G1/S arrest. In contrast to the protein level, MZR produced no changes in p27(kip1) mRNA abundance. MZR impaired p27(kip1) degradation through downregulating the expression of Skp2 and this effect was not dependent on its inhibition on DNA synthesis. Skp2 overexpression abolished MZR-induced p27(kip1) accumulation.
These results suggested that MZR-induced p27(kip1) accumulation was at least partly mediated by Skp2, and that Skp2 might be a novel target of MZR inhibiting MC proliferation.
背景/目的：咪唑立宾（MZR）可抑制系膜细胞（MC）增殖，但其机制尚不清楚。在本研究中，我们通过细胞周期调节蛋白依赖性机制研究了MZR对MC增殖的抑制作用。
我们研究了MZR对原代培养大鼠MC增殖以及细胞周期调节蛋白如细胞周期蛋白D1、细胞周期蛋白依赖性激酶2和p27（kip1）表达的影响。我们进一步着重分析了MZR对S期激酶相关蛋白2（Skp2）的影响，Skp2在p27（kip1）降解中起关键作用。
MZR有效抑制原代培养大鼠MC的增殖，降低细胞周期蛋白D1和细胞周期蛋白依赖性激酶2的表达，同时显著增加p27（kip1）的蛋白水平，维持p27（kip1）的核定位并诱导G1/S期阻滞。与蛋白水平相反，MZR对p27（kip1）mRNA丰度无影响。MZR通过下调Skp2的表达损害p27（kip1）的降解，且这种作用不依赖于其对DNA合成的抑制。Skp2过表达消除了MZR诱导的p27（kip1）积累。
这些结果表明，MZR诱导的p27（kip1）积累至少部分由Skp2介导，且Skp2可能是MZR抑制MC增殖的新靶点。
