PDZK1调节Mas稳定性参与AMI后心肌纤维化的机制研究

Myocardial fibrosis is one of the main reasons which induce high mortality rate of heart failure after AMI. To explore its mechanism and find therapeutic targets have become scientific problems to be solved urgently. A number of studies have shown that Mas, as an Ang- (1-7) specific receptor, was significantly reduced in myocardial tissue of myocardial fibrosis rats. It has been reported that Mas receptor levels were significantly down-regulated in fibrotic myocardium, but studies focused on intracellular and post-translational modifications of Mas were lacked. Previous studies found that there is PDZ binding domain in the carboxyl terminus of Mas. For the first time, we found that PDZK1 interacts with the carboxyl terminus of Mas receptor through the PDZ1 domain. In animal models of myocardial fibrosis, PDZK1 and Mas receptors were significantly decreased, and when cardiac fibroblasts were pretreated by proteasome inhibitor, Mas receptor expressed higher than hypoxia group. Therefore, we proposed that in myocardial fibrosis after AMI, the significant decrease of PDZK1 relieved the inhibitory effect on the proteasome and caused the decrease of the stability of Mas receptor. The low level of Mas receptor led to imbalance of RAS system in the heart and promoted myocardial fibrosis. This study intends to reveal the mechanism by which PDZK1 regulates the stability of Mas receptor during myocardial fibrosis, and elucidates the role of PDZK1 in regulating the stability of Mas receptor in myocardial fibrosis and provides a scientific basis for the prevention and treatment of myocardial fibrosis.

心肌纤维化是AMI后心力衰竭死亡率居高不下的重要原因之一，探讨其发生机制并寻找治疗靶点成为亟待解决的科学问题。多项研究表明Mas作为Ang-(1-7)特异性受体，在心肌纤维化大鼠心肌组织中表达显著降低。但关于Mas调控心肌纤维化的研究多集中于发现受体表达降低及下游信号通路变化上，其胞内调节和翻译后修饰却缺乏研究。前期研究发现Mas羧基端存在PDZ结合结构域，且PDZK1通过PDZ1结构域与Mas羧基端相互作用；在心肌纤维化模型中PDZK1及Mas受体显著下调，应用蛋白酶体抑制剂后，Mas受体表达较模型组升高。因此提出假说：心肌纤维化中PDZK1表达下调解除了其对蛋白酶体的抑制作用，引起Mas受体稳定性降低，低水平的Mas促进心肌纤维化。本课题拟通过动物及细胞实验揭示PDZK1调节Mas受体稳定性的机制，阐明PDZK1调节Mas受体稳定性在心肌纤维化中的作用，为心肌纤维化的防治提供科学依据。

心肌纤维化是AMI后心力衰竭死亡率居高不下的重要原因之一，探讨其发生机制并寻找治疗靶点成为亟待解决的科学问题。多项研究表明Mas作为Ang-(1-7)特异性受体，在心肌纤维化大鼠心肌组织中表达显著降低。但关于Mas调控心肌纤维化的研究多集中于发现受体表达降低及下游信号通路变化上，其胞内调节和翻译后修饰却缺乏研究。前期研究发现Mas羧基端存在PDZ结合结构域，且PDZK1通过PDZ1结构域与Mas羧基端相互作用；在心肌纤维化模型中PDZK1及Mas受体显著下调，应用蛋白酶体抑制剂后，Mas受体表达较模型组升高。因此提出假说：心肌纤维化中PDZK1表达下调解除了其对蛋白酶体的抑制作用，引起Mas受体稳定性降低，低水平的Mas促进心肌纤维化。本研究按照实验计划观察了Mas受体及PDZK1的表达水平与心室重塑的关系，明确了PDZK1与Mas受体相互作用的具体位点，探讨了PDZK1与Mas受体相互作用对Mas受体泛素化/稳定性的影响以及PDZK1调节Mas受体稳定性对心室重塑的影响。证实了在心室重塑中，PDZK1 表达显著降低解除了其对蛋白酶体的抑制作用，引起 Mas 受体的稳定性降低，低水平的 Mas 受体导致心脏 RAS 系统失衡，从而促进心室重塑的假说。研究共分为四部分：（一）PDZK1通过PDZ1结构域与Mas羧基端相互作用；（二）PDZK1通过抑制蛋白酶体途径增加Mas受体稳定性；（三）PDZK1靶向Mas受体改善急性心肌梗死诱导的心肌纤维化；（四）PDZK1靶向Mas受体改善高血压心室重塑。研究结果为探索Mas受体的胞内调节和翻译后修饰提供科学依据，为心室重塑的防治提供理论依据。