Department of Nephrology, Shengjing Hospital of China Medical University, Shenyang, Liaoning, People's Republic of China.
Department of Nephrology, Shengjing Hospital of China Medical University, Shenyang, Liaoning, People's Republic of China.
Lab Invest. 2023 Feb;103(2):100016. doi: 10.1016/j.labinv.2022.100016. Epub 2023 Jan 10.
Renal fibrosis is the major pathologic manifestation of chronic kidney disease (CKD). LIM and cysteine-rich domains 1 (LMCD1) is upregulated in the kidney tissue from patients with CKD and the transforming growth factor β1 (TGF-β1)-treated human renal tubular epithelial cell line human kidney 2 (HK-2) (Gene Expression Omnibus: GSE66494 and GSE23338). Previously, we have demonstrated that the knockdown of LMCD1 ameliorated renal fibrosis in mice by blocking the activation of the extracellular signal-regulated kinase pathway. In this study, we sought to further investigate whether LMCD1 affects TGF-β1-induced epithelial-mesenchymal transition (EMT) of kidney tubular epithelial cells and its potential role in the TGF-β1/Smad signaling pathway. First, we confirmed that LMCD1 expression was increased in the fibrotic kidneys of patients with CKD compared with that in normal kidneys and that LMCD1 was predominantly localized in the renal tubules. LMCD1 and mesenchymal markers were upregulated in obstructed kidney tissues of mice at 21 days after unilateral ureteral obstruction surgery compared with the tissues in sham mice. Next, we demonstrated that TGF-β1 significantly increased LMCD1 expression through Smad-mediated transcription in HK-2 cells in vitro. In turn, LMCD1 acted as a transcriptional coactivator of E2F transcription factor 1 to promote the transcription of TGF-β1. Moreover, TGF-β1 increased the interaction between LMCD1 and Smad ubiquitination regulatory factor 2 (Smurf2) and accelerated Smurf2-mediated LMCD1 degradation via the ubiquitination system. The knockdown of LMCD1 inhibited TGF-β1-induced EMT in both HK-2 cells and unilateral ureteral obstruction mice. Our results indicate a positive feedback loop between TGF-β1 and LMCD1 for EMT induction in HK-2 cells and that Smurf2 acts as a negative regulator in this process by accelerating LMCD1 degradation.
肾纤维化是慢性肾脏病（CKD）的主要病理表现。LIM 和含半胱氨酸丰富域 1（LMCD1）在 CKD 患者的肾脏组织和转化生长因子β1（TGF-β1）处理的人肾小管上皮细胞系人肾 2（HK-2）中上调（基因表达综合数据库：GSE66494 和 GSE23338）。此前，我们已经证明，通过阻断细胞外信号调节激酶途径的激活，LMCD1 的敲低可改善小鼠的肾纤维化。在这项研究中，我们试图进一步研究 LMCD1 是否影响 TGF-β1 诱导的肾小管上皮细胞上皮-间充质转化（EMT）及其在 TGF-β1/Smad 信号通路中的潜在作用。首先，我们证实与正常肾脏相比，CKD 患者纤维化肾脏中的 LMCD1 表达增加，并且 LMCD1 主要定位于肾小管中。与假手术小鼠的组织相比，单侧输尿管梗阻手术后 21 天，梗阻小鼠的肾脏组织中 LMCD1 和间充质标志物上调。接下来，我们证明 TGF-β1 通过 Smad 介导的转录在体外显著增加 HK-2 细胞中的 LMCD1 表达。反过来，LMCD1 作为 E2F 转录因子 1 的转录共激活因子发挥作用，促进 TGF-β1 的转录。此外，TGF-β1 增加了 LMCD1 和 Smad 泛素化调节因子 2（Smurf2）之间的相互作用，并通过泛素化系统加速 Smurf2 介导的 LMCD1 降解。LMCD1 的敲低抑制了 TGF-β1 在 HK-2 细胞和单侧输尿管梗阻小鼠中诱导的 EMT。我们的结果表明 TGF-β1 和 LMCD1 之间存在 EMT 诱导的正反馈回路，Smurf2 通过加速 LMCD1 降解在该过程中起负调节作用。
