Restriction of HIV infection by SAMHD1 protein

描述（由申请人提供）：巨噬细胞和树突状细胞在病毒感染中起关键作用，提供经常抵抗抗病毒治疗的病毒库，并将先天病毒检测与抗病毒适应性免疫反应联系起来。人类免疫缺陷病毒1 （HIV-1）不能转导树突状细胞，并且转导巨噬细胞的能力降低，这是由于病毒进入后早期有效的限制阻止了病毒cDNA的积累。这种限制在很大程度上是由细胞SAMHD1蛋白介导的，其突变导致Aicardi Goutieres综合征（AGS），这是一种自身免疫性疾病，与被认为由内源性核酸引起的先天免疫反应激活有关。重要的是，SAMHD1是HIV-2/SIVsm病毒Vpx蛋白降解的靶标，这与其在抑制灵长类慢病毒感染中的关键作用一致。这些发现表明，SAMHD1介导对HIV感染的免疫反应的关键细胞类型的有效和相关限制，因此可以决定抗病毒治疗的长期结果。我们建议阐明控制和介导SAMHD1限制HIV感染的细胞和分子机制。目的1的实验将在病毒和细胞检测的背景下定义SAMHD1蛋白的功能组织，并评估SAMHD1的病毒学和细胞功能之间的关系。目的2的实验将评估SAMHD1如何干扰HIV-1 cDNA合成。我们的数据表明，SAMHD1脱氧核苷三磷酸三磷酸水解酶（dNTPase）的催化活性在细胞中受到调节，与其他细胞酶的情况一样，其本身不足以限制HIV感染。因此，SAMHD1在限制性和非限制性条件下的催化活性将为

DESCRIPTION (provided by applicant): Macrophages and dendritic cells have key roles in viral infections, providing virus reservoirs that frequently resist anti-viral therapies and linkin innate virus detection to anti-viral adaptive immune responses. Human immunodeficiency virus 1 (HIV-1) fails to transduce dendritic cells and has a reduced ability to transduce macrophages, due to a potent early post-entry restriction preventing accumulation of viral cDNA. The restriction is to a large extent mediated by cellular SAMHD1 protein, mutations in which lead to Aicardi Goutieres Syndrome (AGS), an autoimmune disease associated with activation of the innate immune response thought to be provoked by endogenous nucleic acids. Importantly, SAMHD1 is targeted for degradation by the Vpx protein of HIV-2/SIVsm viruses, consistent with its key role in inhibiting primate lentivirus infection. These findings indicate that SAMHD1 mediates potent and relevant restriction in key cell types that orchestrate the immune response to HIV infection, and hence could determine long-term outcomes of antiviral therapies. We propose to elucidate the cellular and molecular mechanisms that control and mediate the restriction of HIV infection by SAMHD1. Experiments in aim 1 will define the functional organization of the SAMHD1 protein in the context of viral and cell-based assays, and assess the relationship between virologic and cellular functions of SAMHD1. Experiments in aim 2 will assess how SAMHD1 interferes with HIV-1 cDNA synthesis. Our data suggest that SAMHD1 deoxynucleoside triphosphate triphosphohydrolase (dNTPase) catalytic activity is regulated in cels, as is the case with other cellular enzymes, and per se is not sufficient to restrict HIV infection. Hence, SAMHD1 catalytic activity under restrictive vs non-restrictive conditions will be characterized and the possible importance of SAMHD1 proximity to the RTC for the restriction to occur will be assessed. In aim 3, a combination of biochemical/proteomic/reverse genetic approaches will be used to identify cellular proteins and post-translational modifications that control SAMHD1 function. Experiments in aim 4 wil characterize developmental profiles of SAMHD1-mediated inhibition of HIV-1 infection in myeloid cells during their in vitro differentiation from CD34+ progenitor cells, and the possible involvement of SAMHD1 in early post-entry blocks of HIV-1 infection in non-myeloid cells. The relative importance of SAMHD1 co-factors, identified in aim 3, in primary myeloid cels wil also be assessed. The knowledge gained from our studies could lead to the conception of new strategies to improve the immune response to HIV and/or prevent formation of long-lived HIV reservoirs in tissue macrophages, by manipulating the SAMHD1 pathway.