SAMHD1 mediated dNTP regulation and HIV in myeloid cells

项目摘要 包括HIV-1在内的慢病毒感染活化/分裂的CD 4 + T细胞和终末- 分化的/不分裂的骨髓细胞（例如，巨噬细胞和小胶质细胞）在其过程中， 发病机制慢病毒的逆转录消耗由感染的病毒提供的dNTP底物。 宿主细胞然而，据预测，非分裂细胞如巨噬细胞应含有有限的dNTP 池.事实上，我们以前报道过，人原代单核细胞衍生的巨噬细胞具有极强的 与活化的CD 4 + T细胞（1-5 µM）相比，有限的dNTP水平（20-40 nM）， 巨噬细胞限制HIV-1复制。我们还报告说，主机SAM域和HD域 含有蛋白1（SAMHD 1），其水解dNTPs并且在巨噬细胞中丰富，负责 低dNTP水平和限制HIV-1在巨噬细胞中的复制。最近，我们发现了两个新的 SAMHD 1介导的dNTP代谢的调节回路可在非分裂髓样细胞中起作用 用于dNTP耗尽和HIV-1限制。在这个建议中，我们建议阐明病毒学，分子和 非分裂髓系中SAMHD 1介导的dNTP耗竭的这些调节回路的结构性质 细胞在目的1中，我们将探讨我们的假设，即SAMHD 1不仅水解dNTPs，而且直接水解dNTPs。 通过与巨噬细胞中的RNR结合来抑制RNR介导的dNTP生物合成。我们的假设 预测Vpx可以通过以下方式快速升高SAMHD 1降解后巨噬细胞中的dNTP水平： 同时去除RNR介导的dNTP生物合成的抑制性调节剂。事实上，我们最近 观察到SAMHD 1与RNR R1亚基的直接结合，支持这一假设。在这里，我们将 研究这种由SAMHD 1-RNR相互作用介导的负性dNTP代谢调节回路， 非分裂髓系细胞中的dNTP耗竭和HIV-1限制。在目标2中，我们假设细胞PP 2A- B55 β磷酸酶是非分裂髓系细胞中SAMHD 1的关键正调节因子，可保持SAMHD 1 未磷酸化且对dNTP消耗和HIV-1限制具有酶活性。我曾观察到， SAMHD 1与非分裂髓系细胞中PP 2A的B55 β调节亚基的相互作用，支持了这一点。 假说.在此，我们将研究SAMHD 1-PP 2A相互作用在dNTP负调控中的作用 代谢和HIV-1限制。在目标3中，我们建议研究结构和 SAMHD 1与RNR和PP 2A相互作用的分子性质有助于dNTP耗尽和HIV-1。 1限制在非分裂骨髓细胞采用冷冻电镜和X射线晶体学。总的来说，我们将 探索非分裂髓系细胞中独特的SAMHD 1介导的dNTP代谢调节回路， 是由两个不同的监管机构设计的，这项提案旨在发现新的和更好的抗病毒概念， 特异性靶向导致HIV-1持续存在的长寿命骨髓储库中的HIV-1。

Project Summary Lentiviruses including HIV-1 infect both activated/dividing CD4+ T cells and terminally- differentiated/nondividing myeloid cells (e.g., macrophages and microglia) during the course of their pathogenesis. The reverse transcription of lentiviruses consumes dNTP substrates provided from the infected host cells. However, it was predicted that nondividing cells such as macrophages should contain limited dNTP pools. Indeed, we previously reported that human primary monocyte derived macrophages harbor extremely limited dNTP levels (20-40 nM), compared to activated CD4+ T cells (1-5 µM), and this limited dNTP level in macrophages restricts HIV-1 replication. We also reported that the host SAM domain and HD domain containing protein 1 (SAMHD1), which hydrolyzes dNTPs and is abundant in macrophages, is responsible for the low dNTP levels and the restricted HIV-1 replication in macrophages. Recently, we discovered two novel regulatory circuits of SAMHD1 mediated dNTP metabolism that can operate in nondividing myeloid cells for dNTP depletion and HIV-1 restriction. In this proposal, we propose to elucidate virological, molecular and structural natures of these regulatory circuits of SAMHD1-mediated dNTP depletion in nondividing myeloid cells. In Aim 1, we will explore our hypothesis that SAMHD1 not only hydrolyzes dNTPs but also directly suppresses the RNR-mediated dNTP biosynthesis by binding to RNR in macrophages. Our hypothesis predicts that Vpx can rapidly elevate dNTP levels in macrophages following SAMHD1 degradation by simultaneously removing a suppressive regulator of RNR mediated dNTP biosynthesis. Indeed, we recently observed the direct binding of SAMHD1 to RNR R1 subunit, supporting this hypothesis. Here, we will investigate this negative dNTP metabolic regulatory circuit mediated by the SAMHD1-RNR interaction for dNTP depletion and HIV-1 restriction in nondividing myeloid cells. In Aim 2, we hypothesize that cellular PP2A- B55 phosphatase is a key positive regulator of SAMHD1 in nondividing myeloid cells that can keep SAMHD1 un-phosphorylated and enzymatically active for dNTP depletion and HIV-1 restriction. Indeed, we observed the interaction of SAMHD1 with B55 regulatory subunit of PP2A in nondividing myeloid cells, supporting this hypothesis. Here, we will investigate the roles of SAMHD1-PP2A interaction in the negative regulation of dNTP metabolism and HIV-1 restriction in macrophages. In Aim 3, we propose to investigate the structural and molecular natures of the SAMHD1 interactions with RNR and PP2A that contribute to dNTP depletion and HIV- 1 restriction in nondividing myeloid cells by employing cryo-EM and X-ray crystallography. Overall, we will explore the unique SAMHD1-mediated dNTP metabolic regulatory circuits in nondividing myeloid cells, which are engineered by two distinct regulators, and this proposal aims to discover new and better antiviral concepts specifically targeting HIV-1 in long-living myeloid reservoirs that contribute to HIV-1 persistence.