Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555-1079, USA.
J Hypertens. 2012 May;30(5):917-25. doi: 10.1097/HJH.0b013e3283525124.
Apurinic/apyrimidinic-endonuclease 1 (APE1) heterozygous mice have chronically elevated blood pressure. Renin of the renin-angiotensin (ANG) system for blood pressure maintenance regulates production of ANG II, a vasoactive hormone. Renin expression and secretion from kidney juxtaglomerular cells are regulated by intracellular calcium. Our objective in this study is to investigate APE1's regulatory role in renin expression.
Effect of APE1 on calcium-mediated modulation of renin expression was examined by real-time reverse transcriptase-PCR, Western analysis and renin promoter-dependent luciferase activity in APE1-knockdown, APE1-overexpressing or control mouse kidney As4.1 cells. Furthermore, coimmunoprecipitation and chromatin immunoprecipitation assays were utilized to examine the association of APE1 with histone deacetylase (HDAC)1 corepressor complex and their recruitment to renin enhancer. Finally, kidney renin mRNA level and plasma-renin activity were measured in wild-type and APE1-heterozygous mice.
Here we show that APE1 is involved in calcium-mediated repression of renin gene. Our results further indicate that APE1 is a component of HDAC1 corepressor complex bound to renin-enhancer region. Increase in intracellular calcium ion concentration enhances the association of APE1 with HDAC1 corepressor complex and their recruitment to the enhancer region. Furthermore, APE1's N-terminal region is critical for formation and recruitment of the enhancer-bound corepressor complex. Increased renin expression in kidneys and higher plasma-renin activity in APE1 heterozygous mice further supports APE1's corepressor role in vivo.
This study uncovers APE1's function as a novel negative regulator of renin expression, and thereby in blood pressure maintenance.
嘌呤/嘧啶核酸内切酶 1（APE1）杂合子小鼠具有慢性高血压。肾素-血管紧张素（ANG）系统是维持血压的关键，其调节血管活性激素 ANG II 的产生。肾素在肾小球旁细胞中的表达和分泌受细胞内钙离子的调节。本研究旨在探讨 APE1 在肾素表达中的调节作用。
通过实时逆转录 PCR、Western 分析和 APE1 敲低、过表达或对照小鼠肾脏 As4.1 细胞中的肾素启动子依赖性荧光素酶活性，研究 APE1 对钙介导的肾素表达调节的影响。此外，还利用共免疫沉淀和染色质免疫沉淀检测 APE1 与组蛋白去乙酰化酶（HDAC）1 核心抑制复合物的关联及其向肾素增强子的募集。最后，在野生型和 APE1 杂合子小鼠中测量肾脏肾素 mRNA 水平和血浆肾素活性。
本研究表明 APE1 参与了钙介导的肾素基因抑制。研究结果进一步表明，APE1 是与肾素增强子区域结合的 HDAC1 核心抑制复合物的组成部分。细胞内钙离子浓度增加增强了 APE1 与 HDAC1 核心抑制复合物的结合及其向增强子区域的募集。此外，APE1 的 N 端区域对于增强子结合的核心抑制复合物的形成和募集至关重要。肾脏中肾素表达增加和 APE1 杂合子小鼠血浆肾素活性升高进一步支持了 APE1 在体内作为肾素表达负调控因子的作用。
本研究揭示了 APE1 作为肾素表达的新型负调控因子的功能，从而维持血压。
