Vascular Smooth Muscle Protein Quality Control and Aortic Aneurysm Formation

项目总结 腹主动脉瘤(Aaa)是一种发病率高、病死率高、致死率高的疾病。 致命的夹层和破裂的可能性。目前还没有经过验证的药物治疗方法可以预防 AAA级。VSMC变性在AAA发病机制中起重要作用，但其机制仍然存在 难以捉摸。泛素蛋白酶体系统(UPS)作为一种重要的蛋白质质量控制机制，通过 降解错误折叠的蛋白质和多余的正常蛋白质。而UPS不足导致的蛋白质毒性 功能已被广泛接受为多种退行性疾病的重要机制， AAA患者是否存在UPS功能障碍尚不清楚。人AAA组织中OUR通路的分析 揭示了UPS功能与AAA之间的关联。在AAA小鼠模型中，泛素化的积聚 蛋白质是UPS性能受损的标志，在VSMC变性和AAA形成之前， 随着疾病的发展而加重。这表明，UPS性能不足可能会成为一种新奇的 AAA病因学的潜在机制。MYOCD是VSMC收缩基因程序的主开关。多么 MYOCD受调控，在AAA中的功能尚不清楚。VSMC中的批量RNA-seq显示UPS- 除了与VSMC收缩相关的基因外，MYOCD上调的顶级基因程序中还有相关的途径。 MYOCD强制表达改善培养的UPS性能同时抑制VSMC变性 VSMC和VSMC特异性MYOCD转基因(TG)小鼠在AAA形成的早期阶段。MYOCD 上调UPS功能的两个关键分子NFE2L1和KLHL3的表达。这些证据 提示MYOCD在UPS功能中的新作用。磷酸二酯酶(PDE)，通过催化水解酶 CAMP和cGMP特异性调控环核苷酸信号转导，在VSMC病理生理过程中发挥重要作用 是治疗多种人类疾病的有效药物靶点。我们发现PDE10A是诱导最强的PDE 在AAA形成过程中，MYOCD蛋白的表达受到抑制。PDE10A的抑制作用 增加MYOCD蛋白，改善UPS性能，并抑制AAA的形成。这些令人兴奋的东西 初步研究结果支持一种新的假说，即PDE10A下调MYOCD蛋白会损害UPS 表现，导致VSMC变性和AAA。我们提出了三个目的来检验这一假设。目标1 将使用新的VSMC特异性MYOCD基因敲除和TG小鼠来确定MYOCD在血管紧张素Ⅱ诱导的功能中的作用 AAA模型。Aim 2将使用一种新的UPS报告鼠系和生化分析来确定其重要性 MYOCD调节的AAA中UPS功能的变化以及MYOCD如何调节UPS功能。目标3将决定如何 PDE10促进MYOCD蛋白降解和PDE10A在UPS性能和AAA形成中的作用。 该提案将首次解决UPS性能在VSMC退变和AAA中的重要性 形成，并阐明了一种新的调控级联，包括可药物上游调节剂(PDE10A)和 一种下游效应器(MYOCD)，用于保护UPS的性能和蛋白质平衡。

PROJECT SUMMARY Abdominal aortic aneurysm (AAA) is a devastating disease carrying high morbidity and mortality due to the high likelihood of fatal dissection and rupture. There are currently no proven pharmaceutical treatments to prevent AAA progression. VSMC degeneration contributes largely to AAA pathogenesis, but the mechanism remains elusive. The ubiquitin proteasome system (UPS) serves as an essential protein quality control mechanism by degrading misfolded proteins and surplus normal proteins. While proteotoxicity resulting from insufficient UPS function has been widely accepted as an important mechanism for multiple degenerative human conditions, the implication of UPS dysfunction in AAA is completely unknown. Our pathway analysis in human AAA tissues revealed an association of UPS function with AAA. In a mouse model of AAA, accumulation of ubiquitinated proteins, a hallmark of impaired UPS performance, precedes VSMC degeneration and AAA formation and is exacerbated with disease progression. This suggests that inadequate UPS performance may act as a novel mechanism underlying AAA etiology. MYOCD is a master switch of VSMC contractile gene program. How MYOCD is regulated and functions in AAA is unknown. Bulk RNA-seq in VSMCs showed an enrichment of UPS- related pathways in the top MYOCD-upregulated gene programs besides those relevant to VSMC contraction. Forced expression of MYOCD improved UPS performance while suppressing VSMC degeneration in cultured VSMCs and VSMC-specific MYOCD transgenic (Tg) mice at the early stage of AAA formation. MYOCD increased the expression of NFE2L1 and KLHL3, two key players of UPS function. These lines of evidence suggest a novel role of MYOCD in UPS function. Phosphodiesterases (PDEs), by catalyzing the hydrolysis of cAMP and cGMP to specifically modulate cyclic nucleotide signaling, play critical roles in VSMC pathophysiology and are proven drug targets for multiple human diseases. We found that PDE10A was the most induced PDE family member during AAA formation, while MYOCD protein expression was suppressed. Inhibition of PDE10A increased MYOCD protein, improved UPS performance, and suppressed AAA formation. These exciting preliminary findings support a novel hypothesis that downregulation of MYOCD protein by PDE10A impairs UPS performance, leading to VSMC degeneration and AAA. We propose three Aims to test this hypothesis. Aim 1 will use novel VSMC-specific Myocd knockout and Tg mice to determine the function of MYOCD in AngII-induced AAA model. Aim 2 will use a novel UPS reporter mouse line and biochemical assays to determine the importance of UPS function in MYOCD-regulated AAA and how MYOCD modulates UPS function. Aim 3 will determine how PDE10 promotes MYOCD protein degradation and PDE10A functions in UPS performance and AAA formation. This proposal will address for the first time the importance of UPS performance in VSMC degeneration and AAA formation, and elucidate a novel regulatory cascade comprising a druggable upstream modulator (PDE10A) and a downstream effector (MYOCD) in safeguarding UPS performance and proteostasis.