The Role of Amino Acid Starvation Response Kinase GCN2 in Abdominal Aortic Aneurysm

项目摘要：腹主动脉瘤(AAA)是一种威胁生命的疾病，约有150万人受到影响。 美国人，特别是老年人口。尽管破裂时死亡率很高(80%-90%)，但有一种 AAA的临床治疗缺乏有效的药物治疗。手术修复仍然是唯一有效的方法 选择；然而，它们不仅被认为是创伤性的和有风险的，而且对大多数人来说也没有指明 新诊断的AAA患者。因此，有一个迫切的未得到满足的需求，即开发非手术策略来 包含AAA进展。限制氨基酸的饮食成为一种有希望的抗击方法 心血管疾病。我们的研究第一次证明了饮食中蛋氨酸或 亮氨酸限制抑制大鼠腹主动脉瘤模型的发展。众所周知，这样的饮食习惯 限制触发氨基酸饥饿反应，这是一种由新陈代谢驱动的强有力的保护机制 应激蛋白2(GCN2)。事实上，在我们的初步研究中，沉默大鼠的GCN2 腹主动脉抵消蛋氨酸限制对AAA的好处，提示 GCN2在恢复主动脉内稳中的作用通过蛋氨酸限制激活GCN2保护顺畅 防止肌肉细胞(SMC)退化，这是AAA的关键决定因素之一 相反，在AAA的临床标本中强烈地观察到GCN2活性降低，并且 GCN2沉默有效地削弱了对SMC变性的保护作用。最后，我们偶然地 GCN2在其1475位精氨酸(R1475)上被肽基精氨酸脱亚胺酶3(PADI3)瓜氨酸化 饥饿感应域中的残留物。GCN2的这种翻译后修饰(PTM)在 AAA，并与抑制的GCN2活性相关。总的来说，这些初步结果导致了我们的中央 假设：GCN2在防止SMC退变和AAA形成中起关键作用，其 活性受PADI3介导的瓜氨酸化负性调节；GCN2激活策略提供了一种新的 有效预防和干预腹主动脉瘤的范例。在目标1中，我们将剖析GCN2在 使用人和小鼠的SMC来维护SMC的动态平衡及其下游信号。在目标2中， 我们将描述一种负性调节GCN2活性的新的PTM调节机制，并描述其生物学特性 GCN2瓜氨酸化对SMC的影响。在目标3中，我们将确定机制和治疗 利用转基因(SMC特异性GCN2基因敲除小鼠)和AAA中GCN2激活的意义 饮食干预方法(限制蛋氨酸治疗先前存在的AAA病变)。这个 成功完成拟议的研究不仅将揭示一种内在的保护机制 SMC变性和AAA的发病机制，也可能通过GCN2的激活提供了新的范式 有效预防和干预AAA的饮食限制。

Project Summary: Abdominal aortic aneurysm (AAA) is a life-threatening disease that afflicts ~1.5 million Americans, particularly in the elderly populations. Despite its high mortality (80-90%) upon rupture, there is a lack of effective drug therapies for clinical management of AAA. Surgical repairs remain the only effective options; however, not only are they considered traumatic and risky, but also not indicated for the majority of newly diagnosed AAA patients. Therefore, there is a pressing unmet need to develop non-surgical strategies to contain AAA progression. Dietary restrictions of amino acids emerge as promising avenues to combat cardiovascular diseases. For the first time, our study demonstrated the potential of dietary methionine or leucine restrictions in inhibiting the development of AAA in a rat model. It is well established that such dietary restrictions trigger the amino acid starvation response, a potent protective mechanism driven by the metabolic stress kinase general control nondepressible 2 (GCN2). Indeed, in our preliminary study, silencing GCN2 in rat abdominal aorta nullified the benefits of methionine restriction against AAA, suggesting a protective role of GCN2 in reinstating aortic homeostasis. Activating GCN2 through methionine restriction protected smooth muscle cells (SMCs) from undergoing degeneration, which is one of the key determinants of AAA pathogenesis; conversely, reduced GCN2 activity was robustly observed in clinical specimens of AAA, and GCN2 silencing effectively compromised the protection against SMC degeneration. Finally, we serendipitously identified GCN2 to be citrullinated by peptidyl arginine deiminase 3 (PADI3) at its 1475 arginine (R1475) residue in the starvation-sensing domain. This post-translational modification (PTM) of GCN2 was increased in AAA and correlated with repressed GCN2 activity. Collectively, these preliminary results lead to our central hypothesis: GCN2 plays a pivotal role in protecting against SMC degeneration and AAA formation, and its activity is negatively modulated by PADI3-mediated citrullination; GCN2-activating strategies offer a new paradigm for effective prevention and intervention of AAA. In Aim 1, we will dissect the role of GCN2 in safeguarding SMC homeostasis as well as its downstream signaling using human and murine SMCs. In Aim 2, we will characterize a new PTM regulation that negatively modulates GCN2 activity and delineate the biological consequences of GCN2 citrullination in SMC. In Aim 3, we will determine the mechanistic and therapeutic implications of GCN2 activation in AAA, utilizing both transgenic (SMC-specific GCN2 knockout mice) and dietary intervention approaches (methionine restriction for treatment of pre-existing AAA lesions). The successful completion of the proposed studies will not only uncover an intrinsic protective mechanism against SMC degeneration and AAA pathogenesis, but also may provide a new paradigm through GCN2-activating dietary restrictions for effective prevention and intervention of AAA.