KLF4 诱导circRPS6KA1表达在调控VSMC向pDC样细胞转化中的作用和分子机制

Based on our previous findings that: (1) atherogenic factor oxidized phospholipids POVPC can upregulate the expression of KLF4 and the pDC (plasmacytoid dendritic cell) marker CD123; (2) overexpression of KLF4 dramatically increases CD123 expression and KLF4 can not bind to CD123 gene promoter to regulate its transcription directly; (3) KLF4 markedly promotes circRPS6KA1 formation; (4) circRPS6KA1 can induce CD123 expression, we propose that KLF4-induced circRPS6KA1 expression plays a key role in the switching of VSMC to pDC induced by POVPC. In the present study, we sought to explore whether KLF4 induces circRPS6KA1 formation by interacting with the RNA binding protein RBM25 and whether circRPS6KA1 activates CD123 transcription by recruiting the RNA polymerase II to the CD123 gene promoter. In addition, we will further study whether circRPS6KA1 forms feedback loop with KLF4 in VSMC to regulate the expression of CD123. Our study will indentify the role of KLF4-circRPS6KA1 axis in POVPC-induced switching of VSMC to pDC.

基于前期发现（1）致动脉粥样硬化因素氧化磷脂POVPC明显上调KLF4和人浆细胞样树突状细胞（plasmacytoid dendritic cell, pDC）标志基因CD123表达；（2）KLF4过表达显著促进CD123表达，且KLF4不能结合到CD123基因启动子区直接激活该基因转录；（3）KLF4显著促进内含子环状RNA circRPS6KA1的形成；（4）circRPS6KA1显著诱导CD123表达，我们提出KLF4通过促进circRPS6KA1表达在POVPC诱导VSMC向pDC样细胞转化中发挥重要作用的新观点。本项目拟明确KLF4通过与RNA结合蛋白RBM25相互作用促进circRPS6KA1形成，研究circRPS6KA1是否将RNA聚合酶II募集到CD123启动子上并激活转录，阐明KLF4-circRPS6KA1轴在POVPC诱导VSMC向pDC样细胞转化中的作用。

血管平滑肌细胞（vascular smooth muscle cell, VSMC）表型转化（phenotypic switching）是高血压、动脉粥样硬化（Atherosclerosis, As）和血管成形术后再狭窄等血管重塑性疾病发生发展的先决条件和基本细胞病理学变化。锌指转录因子Krüppel-like factor 4（KLF4）是一种多能转录因子，在VSMC表型转化中发挥重要作用。有氧糖酵解不仅在肿瘤的发生发展中发挥重要的作用，还在细胞重编程和转分化等过程中发挥着重要作用。KLF4能否通过调控糖酵解过程调节VSMC表型转化，目前尚不清楚。本研究发现：（1）KLF4能促进VSMC向浆细胞样树突状细胞（plasmacytoid dendritic cell, pDC）样细胞转化；（2）KLF4通过促进糖酵解诱导VSMC向pDC样细胞转化；（3）KLF4上调circCTDP1和翻译延长因子eEF1A2表达，后两者能相互作用促进PFKFB3翻译，从而促进PFKFB3蛋白表达，加强糖酵解过程；（4）体内、外实验证实，肠道菌群代谢产物三甲胺-N-氧化物（Trimethylamine-N-oxide, TMAO）通过诱导KLF4表达，促进VSMC向pDC样细胞转化。本项目首次明确KLF4参与VSMC向pDC样细胞转化；率先阐明KLF4调控糖代谢在VSMC向pDC样细胞转化中的作用；深入探究KLF4调控糖代谢的分子机制。本项目将糖代谢与心血管事件关联，提出致As因素促进VSMC向炎性细胞样细胞转化的新机制，为防治As等疾病提供新的干预靶点。