SRRM4介导Abi1可变剪接调控平滑肌细胞表型转化在动脉粥样硬化中的关键作用和机制研究

Vascular remolding is the pathological base of atherosclerosis. Vascular smooth muscle cell (VSMC) phenotypic switch from contractile to proliferative plays a vital role in vascular remolding. By analyzing whole transcriptome data from contractile and proliferative VSMC, we found expression of the splicing factor SRRM4 is increased in proliferative VSMC. Moreover, we also identified that an alternative splice variant of Abi1 gene, Abi1-p, is highly expressed within proliferative VSMC. Abi1-p contains an additional proline-rich region and can active Erk1/2 signaling. Therefore, we hypothesize that upregulation of SRRM4 drives phenotypic switch of VSMC. Structurally and functionally reprogramed by SRRM4, Abi1-p confers VSMC proliferative phenotype through promoting expression of proliferative markers and repressing contractile markers. In this study, we propose to use in vitro and in vivo methods to reveal the mechanism by which SRRM4 and Abi1-p drive VSMC phenotypic switch. We will also try to validate whether targeting SRRM4 and Abi1-p associated signaling can prevent VSMC phenotypic switch and vascular remolding. This study may guide the development of novel therapeutics aimed at atherosclerosis.

血管重塑是动脉粥样硬化形成的病理基础。血管平滑肌细胞（VSMC）由收缩型变为增殖型的表型转化是导致血管重塑的重要原因。我们前期研究通过全转录组RNA测序发现VSMC表型转化过程中，剪接因子SRRM4及其下游靶基因Abi1剪接异构体Abi1-p的表达显著上调。Abi1-p具有额外的富脯氨酸蛋白结合域，我们推测其可能通过激活Erk1/2信号通路参与VSMC表型转化，但具体作用机制仍有待揭示。本课题拟利用分子生物学方法和生物信息学技术，在细胞以及临床样本层面，通过系统生物学研究手段，阐明SRRM4通过介导Abi1可变剪接调控VSMC表型转化的机制，并验证干预SRRM4及Abi1-p相关信号通路对调控VSMC表型转化、抑制血管重塑进而延缓动脉粥样硬化进程的关键作用，为临床治疗动脉粥样硬化提供新的作用靶点。

血管重塑是动脉粥样硬化形成的病理基础。血管平滑肌细胞（VSMC）的表型转化是导致血管重塑的重要原因。我们通过全转录组RNA测序在下肢动脉硬化闭塞（ASO）患者血管组织中发现VSMC表型转化过程中，剪接因子SRRM4表达上调，MBNL1表达下调，同时伴有下游靶基因Abi1剪接异构体Abi1-Δe10的表达显著上调。进一步分析发现，SRRM4及MBNL1通过不同的作用机制相互拮抗调控Abi1基因中外显子10的接入，进而相互拮抗的调控Abi1基因可变剪接及剪接异构体Abi1-Δe10表达。细胞生物学实验发现，过表达剪接异构体Abi1-Δe10上调VSMC细胞增殖及迁移，同时促进VSMC吞噬能力，同时抑制VSMC细胞收缩能力。此外Abi1-Δe10上调VSMC细胞表达巨噬细胞标志物CD68，下调收缩性平滑肌细胞标志物aSMA，表明Abi1-Δe10诱导VSMC表型转化。分子生物学研究发现，Abi1-Δe10上调小分子GTP酶Rac1催化活性及膜定位，进而激活其下游通路。Rac1激活后，通过NOX1/ROS轴，调控干细胞因子KLF4表达及核定位，促进VSMC表型转化。抑制Rac1及NOX1活性逆转了Abi1-Δe10介导的VSMC表型转化。综上，本研究发现ASO患者血管平滑肌细胞中剪接因子SRRM4及MBNL1相互拮抗，共同调控Abi1基因可变剪接。SRRM4上调或MBNL1下调均会导致Abi1可变剪接失调。本研究也首次发现了Abi1基因除了细胞收缩外全新的病理生理功能即Abi1-Δe10/Rac1/NOX1/ROS/KLF4轴调控血管平滑肌细胞表型转化。本研究对阐明ASO发病机制具有一定的科学意义，同时为临床ASO的转化治疗方式提供了新的应用前景.

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