Cellular Nucleotide Metabolism in HIV Restriction

描述(申请人提供)：我们的长期目标是了解宿主因子如何在维持核苷酸动态平衡和启动病毒的界面上在人类细胞中发挥作用 防御机制。像HIV这样的病毒病原体和灵长类免疫系统之间的斗争已经把核酸代谢放在了中心位置。例如，限制因子SAMHD1和APOBEC3D/F/G/H主要干扰HIV复制，并分别被病毒VPX和Vif蛋白抵消。SAMHD1基因的突变导致自身免疫性疾病Aicardi-Goutieres综合征(AGS)，这是一种狼疮样神经退行性疾病，临床上模仿先天性病毒感染。对干扰素介导的对核酸的先天免疫反应的关键见解已经从AGS的遗传学中收集到。AGS是由核酸代谢酶SAMHD1、TREX1、三亚单位RNaseH2复合体和ADAR1的变异引起的。我们对SAMHD1的生化和结构的研究揭示了SAMHD1的脱氧核苷酸三磷酸水解酶活性，并提出了该酶可能在核酸代谢和干扰素介导的抗病毒反应之间发挥作用的机制，正常调节细胞dNTP水平，并在干扰素对饥饿的HIV进行逆转录所需的dNTPs的反应中发挥作用。然而，SAMHD1在人类细胞中的作用机制以及在HIV免疫激活过程中的致病机制还不是很清楚。特别是，这种酶的调节机制以及SAMHD1的功能障碍变体如何触发核酸介导的先天性免疫反应和自身免疫性疾病还没有定义。在这个项目中，我们将进行生化、遗传和结构研究，以全面了解SAMHD1及其在核酸代谢、抗病毒防御和自身免疫中的作用。对这些机制的洞察将发现在抗病毒反应、自身免疫和炎症方面的治疗靶向的新机会。

DESCRIPTION (provided by applicant): Our long-term goal is to understand how host factors function in human cells at the interface of maintaining nucleotide homeostasis and initiating viral defense mechanisms. The battle between viral pathogens like HIV and the primate immune system has placed nucleic acid metabolism center stage. For example, the restriction factors SAMHD1 and APOBEC3D/F/G/H dominantly interfere with HIV replication and are counteracted by viral Vpx and Vif proteins, respectively. Mutations in the SAMHD1 gene cause the autoimmune disease Aicardi-Goutieres syndrome (AGS), a lupus-like neurodegenerative disorder that clinically mimics congenital viral infection. Key insights into the interferon-mediatd innate immune response to nucleic acids have been gleaned from the genetics of AGS. AGS is caused by variations in the nucleic acid metabolizing enzymes SAMHD1, TREX1, the three-subunit RNase H2 complex, and ADAR1. Our work on the biochemistry and structure of SAMHD1 revealed the deoxynucleotide triphosphohydrolase activity and suggested a mechanism by which this enzyme might function at the interface of nucleic acid metabolism and the interferon-mediated antiviral response, serving normally to regulate cellular dNTP levels and during an interferon response to starve HIV of dNTPs required for reverse transcription. However, the details of the mechanism of SAMHD1 action in human cells and in HIV pathogenesis during immune activation are not well understood. In particular, the mechanisms by which this enzyme is regulated and how dysfunctional variants of SAMHD1 trigger nucleic acid-mediated innate immune responses and autoimmune disease have not been defined. In this project we will perform biochemical, genetic, and structural studies to generate a comprehensive understanding of SAMHD1 and its roles in nucleic acid metabolism, antiviral defense, and autoimmunity. Insights into these mechanisms will uncover new opportunities for therapeutic targeting in the antiviral response, autoimmunity, and inflammation.