Department of Microbiology and Molecular Cell Biology.
Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, Virginia.
AIDS. 2018 May 15;32(8):965-974. doi: 10.1097/QAD.0000000000001793.
HIV-1 infection of the brain and related cognitive impairment remain prevalent in HIV-1-infected individuals despite combination antiretroviral therapy. Sterile alpha motif and histidine-aspartate domain-containing protein 1 (SAMHD1) is a newly identified host restriction factor that blocks the replication of HIV-1 and other retroviruses in myeloid cells. Cell cycle-regulated phosphorylation at residue Thr592 and viral protein X (Vpx)-mediated degradation of SAMHD1 have been shown to bypass SAMHD1 restriction in vitro. Herein, we investigated expression and phosphorylation of SAMHD1 in vivo in relation to macrophage infection and proliferation during the neuropathogenesis of HIV-1 and simian immunodeficiency virus (SIV) encephalitis.
Using brain and other tissues from uninfected and SIV-infected macaques with or without encephalitis, we performed immunohistochemistry, multilabel fluorescence microscopy and western blot to examine the expression, localization and phosphorylation of SAMHD1.
The number of SAMHD1 nuclei increased in encephalitic brains despite the presence of Vpx. Many of these cells were perivascular macrophages, although subsets of SAMHD1 microglia and endothelial cells were also observed. The SAMHD1 macrophages were shown to be both infected and proliferating. Moreover, the presence of cycling SAMHD1 brain macrophages was confirmed in the tissue of HIV-1-infected patients with encephalitis. Finally, western blot analysis of brain-protein extracts from SIV-infected macaques showed that SAMHD1 protein exists in the brain mainly as an inactive Thr592-phosphorylated form.
The ability of SAMHD1 to act as a restriction factor for SIV/HIV in the brain is likely bypassed in proliferating brain macrophages through the phosphorylation-mediated inactivation, not Vpx-mediated degradation of SAMHD1.
尽管采用了联合抗逆转录病毒疗法，HIV-1 对大脑的感染和相关认知障碍在 HIV-1 感染者中仍然普遍存在。Sterile alpha motif and histidine-aspartate domain-containing protein 1（SAMHD1）是一种新发现的宿主限制因子，可阻止 HIV-1 和其他逆转录病毒在髓样细胞中的复制。已证实残基 Thr592 的细胞周期调节磷酸化和病毒蛋白 X（Vpx）介导的 SAMHD1 降解可在体外绕过 SAMHD1 限制。在此，我们研究了 SAMHD1 在 HIV-1 和猴免疫缺陷病毒（SIV）脑炎的神经发病机制过程中与巨噬细胞感染和增殖相关的体内表达和磷酸化。
使用未感染和 SIV 感染的猕猴的脑和其他组织，进行免疫组织化学、多标记荧光显微镜和 Western blot 检测，以检查 SAMHD1 的表达、定位和磷酸化。
尽管存在 Vpx，但在脑炎大脑中 SAMHD1 核的数量增加。这些细胞中的许多是血管周巨噬细胞，但也观察到 SAMHD1 小胶质细胞和内皮细胞的亚群。证明 SAMHD1 巨噬细胞既被感染又在增殖。此外，在 HIV-1 感染伴脑炎的患者的组织中也证实了存在处于细胞周期的 SAMHD1 脑巨噬细胞。最后，对 SIV 感染猕猴的脑蛋白提取物进行 Western blot 分析显示，SAMHD1 蛋白主要以无活性的 Thr592 磷酸化形式存在于大脑中。
SAMHD1 在大脑中作为 SIV/HIV 的限制因子的能力可能通过磷酸化介导的失活而不是 Vpx 介导的 SAMHD1 降解而在增殖的脑巨噬细胞中被绕过。
