Circ-0017076通过“海绵状”吸附miR-185调控Stim1介导的Ca2+内流在人肾小管上皮细胞-间充质转分化中的作用及分子机制研究

Epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells is one of the main reasons that caused renal tubular interstitial fibrosis, and the molecular mechanism is unclear. Circular RNA (circRNA) is a kind of special non-coding RNA which is abundant in rna-binding protein. CircRNA can act as molecular "sponge" of micrornas (miRNA sponge) and combine to make the effect of endogenous competition with miRNA. This competition is dedicated to remove the miRNA from the target genes, thus promotes the expression of target genes. This study found that has_circ_0017076 was highly expressed in human renal fibrosis organization, and could promote calcium influx, EMT process and Stim1 protein activation of SOCC calcium channel in the human renal tubular epithelial cells, and recovery increases of the expression of miR-185 would reduce it. Therefore, this study aims to investigate whether the has_circ_0017076 accelerate calcium influx and EMT process through a competitive combination of miR-185 to lift the inhibition of the expression of stim1 in renal tubular epithelial cell, in order to find new effective therapeutic targets on renal tubular interstitial fibrosis.

肾小管上皮细胞-间充质转分化是引起肾小管间质纤维化的主要原因之一，其发生机制尚不清楚。环状RNA(circRNA)是一类富含RNA结合蛋白的特殊非编码RNA，circRNA可充当miRNA分子“海绵”与miRNA内源性竞争结合，进而解除miRNA对其靶基因mRNA的抑制，从而促进靶基因的表达。本研究发现has_circ_0017076在人体肾脏纤维化组织中呈高表达状态，且可以促进人肾小管上皮细胞SOCC钙通道Stim1蛋白激活、Ca2+内流和EMT进程，而恢复上调miR-185的表达能够削减has_circ_0017076这一作用。因此，本研究将致力于探讨has_circ_0017076是否通过竞争性结合miR-185从而解除对stim1表达的抑制，并最终诱导了肾小管上皮细胞的Ca2+内流和EMT进程，以期探寻新的肾小管间质纤维化的有效治疗靶点。

肾间质纤维化(Renal interstitial fibrosis，RIF)是进行性慢性肾病的常见病理标志。环状RNA (Circular RNAs，circRNAs)与某些肾脏疾病有关，但它们在RIF中的作用在很大程度上是未知的。本研究探讨了circRNA_0017076在RIF中的作用及其潜在机制。CircRNA_0017076在转化生长因子-β1 (transforming growth factor-β1，TGF-β1)处理的肾小管上皮细胞( renal tubular epithelial cells，RTECs)和RIF患者肾活检标本中表达明显上调。功能分析表明，circRNA_0017076与microRNA-185-5p (miR-185-5p)共定位，并通过直接结合miR-185-5p抑制miR-185-5p的功能。在体外，circRNA_0017076的敲除抑制了Ca2+内流介导的RTECs上皮-间充质转化(epithelial-to-mesenchymal transition, EMT)，并下调了miR-185-5p的靶蛋白基质相互作用分子1 (stromal interaction molecule 1，STIM1)的表达。通过靶向miR-185-5p/STIM1轴，沉默mmu_circ_0004488可以减缓单侧输尿管梗阻(unilateral ureteral obstruction，UUO)小鼠肾脏的纤维化病变。我们首次发现circRNA_0017076作为miR-185-5p的海绵，其调控STIM1基因表达并参与RIF。我们的研究结果支持circRNA_0017076作为RIF疾病的潜在治疗靶点。