Regulation of SAMHD1 antiviral activity

产品说明：最近发现的人限制因子SAMHD 1的表达负责通过原代巨噬细胞、树突细胞和静息CD 4 + T细胞对慢病毒如HIV-1、HIV-2和SIVmac施加的感染阻断。SAMHD 1通过阻止逆转录的发生来阻断慢病毒感染。SIVmac和HIV-2颗粒中含有的病毒辅助蛋白Vpx通过诱导SAMHD 1降解克服SAMHD 1逆转录阻断。SAMHD 1是一种dGTP调节的脱氧核苷酸三磷酸水解酶，可降低三磷酸脱氧核苷酸（dNTP）的细胞水平。巨噬细胞、树突状细胞和CD 4+静息T细胞中dNTP水平的急剧下降与慢病毒无法进行逆转录相关;因此，SAMHD 1通过耗尽dNTP水平来防止慢病毒逆转录。有趣的是，循环和非循环细胞表达SAMHD 1;然而，SAMHD 1的抗病毒活性仅在非循环细胞中观察到。我们的初步发现与观察到的慢病毒限制性表型相关 这些结果有力地表明，磷酸化调节SAMHD 1的抗病毒活性;因此，该提议将测试 假设SAMHD 1的磷酸化诱导构象变化，该构象变化关闭SAMHD 1结构域的活性位点，导致酶促和抗病毒失活的SAMHD 1蛋白。以下具体目标将用于解决这一假设。Aim 1将探索SAMHD 1磷酸化在逆转录病毒限制中的作用。为此，我们将研究SAMHD 1蛋白的限制，其中磷酸化残基被磷酸化模拟物或非磷酸化残基取代。这一目标也将探索参与SAMHD 1磷酸化的激酶的性质。目的2探讨Vpx在SAMHD 1降解前调节SAMHD 1抗病毒和酶活性的能力。目的3探讨SAMHD 1的抗病毒活性和酶活性的调控。具体来说，这一目标将测试SAMHD 1是由球链机制调节的概念。总的来说，这项提议将建立磷酸化作为一个新的框架，了解SAMHD 1的抗病毒特性。了解SAMHD 1的调节对于开发新的抗HIV-1疫苗策略是有用的，因为克服SAMHD 1增加了树突状细胞和巨噬细胞感染期间的适应性免疫应答。此外，巨噬细胞是最具弹性的HIV-1储库之一，因此了解SAMHD 1抗病毒特性的调节可以为消除HIV-1储库提供新的内部。

DESCRIPTION: Expression of the recently discovered human restriction factor SAMHD1 is responsible for the infection block imposed to lentiviruses such as HIV-1, HIV-2 and SIVmac by primary macrophages, dendritic cells and resting CD4+ T-cells. SAMHD1 blocks lentiviral infection by preventing the occurrence of reverse transcription. The viral accessory protein Vpx, contained in SIVmac and HIV-2 particles, overcomes the SAMHD1 reverse transcription block by inducing SAMHD1 degradation. SAMHD1 is a dGTP-regulated deoxynucleotide triphosphohydrolase that decreases the cellular levels of triphosphodeoxynucleotides (dNTPs). The dramatic decrease in dNTP levels in macrophages, dendritic cells and CD4+ resting T cells correlates with the inability of lentiviruses to undergo reverse transcription; therefore, SAMHD1 prevents lentiviral reverse transcription by depletion of dNTP levels. Interestingly, cycling and non-cycling cells express SAMHD1; however, SAMHD1's antiviral activity is only observed in non-cycling cells. Our preliminary findings correlate the lentiviral restriction phenotype observed in non-cycling cells with the phosphorylation state of SAMHD1.These results strongly suggested that phosphorylation regulates the antiviral activity of SAMHD1; therefore, this proposal will test the hypothesis that phosphorylation of SAMHD1 induces a conformational change that closes the active site of SAMHD1 domain resulting in an enzymatically and antivirally inactive SAMHD1 protein. The following specific aims will be used to address this hypothesis. Aim1 will explore the role of SAMHD1 phosphorylation in retroviral restriction. For this purpose, we will study restriction of SAMHD1 proteins where the phosphorylatable residues are replaced by either a phosphomimetic or non-phosphorylatable residue. This aim will also explore the nature of the kinase involved in the phosphorylation of SAMHD1. Aim 2 will explore the ability of Vpx to modulate SAMHD1 antiviral and enzymatic activities before SAMHD1 degradation. Aim 3 will explore the regulation of the antiviral and enzymatic activity of SAMHD1. Specifically, this aim will test the notion that SAMHD1 is regulated by a ball-and-chain mechanism. Overall, this proposal will establish phosphorylation as a new framework for understanding the antiviral properties of SAMHD1. Understanding the regulation of SAMHD1 is instrumental for the development of novel anti-HIV-1 vaccine strategies since overcoming SAMHD1 increases the adaptive immune response during infection of dendritic cells and macrophages. In addition, macrophages represent one of the most resilient HIV-1 reservoirs, so understanding the regulation of SAMHD1 antiviral properties could provide novel insides for the elimination of HIV-1 reservoirs.