Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, USA.
J Biol Chem. 2013 Jul 12;288(28):20683-91. doi: 10.1074/jbc.M113.472159. Epub 2013 Jun 5.
Newly identified anti-HIV host factor, SAMHD1, restricts replication of lentiviruses such as HIV-1, HIV-2, and simian immunodeficiency virus in macrophages by enzymatically hydrolyzing and depleting cellular dNTPs, which are the substrates of viral DNA polymerases. HIV-2 and some simian immunodeficiency viruses express viral protein X (VPX), which counteracts SAMHD1 and elevates cellular dNTPs, enhancing viral replication in macrophages. Because nucleoside reverse transcriptase inhibitors (NRTIs), the most commonly used anti-HIV drugs, compete against cellular dNTPs for incorporation into proviral DNA, we tested whether SAMHD1 directly affects the efficacy of NRTIs in inhibiting HIV-1. We found that reduction of SAMHD1 levels with the use of virus-like particles expressing Vpx- and SAMHD1-specific shRNA subsequently elevates cellular dNTPs and significantly decreases HIV-1 sensitivity to various NRTIs in macrophages. However, virus-like particles +Vpx treatment of activated CD4(+) T cells only minimally reduced NRTI efficacy. Furthermore, with the use of HPLC, we could not detect SAMHD1-mediated hydrolysis of NRTI-triphosphates, verifying that the reduced sensitivity of HIV-1 to NRTIs upon SAMHD1 degradation is most likely caused by the elevation in cellular dNTPs.
新鉴定的抗 HIV 宿主因子 SAMHD1 通过酶解和耗尽细胞 dNTPs（病毒 DNA 聚合酶的底物）来限制慢病毒（如 HIV-1、HIV-2 和猴免疫缺陷病毒）在巨噬细胞中的复制。HIV-2 和一些猴免疫缺陷病毒表达病毒蛋白 X（VPX），它拮抗 SAMHD1 并升高细胞 dNTPs，从而增强巨噬细胞中的病毒复制。由于核苷逆转录酶抑制剂（NRTIs）是最常用的抗 HIV 药物，它们与细胞 dNTP 竞争掺入前病毒 DNA，我们测试了 SAMHD1 是否直接影响 NRTIs 抑制 HIV-1 的效果。我们发现，使用表达 Vpx 和 SAMHD1 特异性 shRNA 的病毒样颗粒降低 SAMHD1 水平会随后升高细胞 dNTPs，并显著降低巨噬细胞中 HIV-1 对各种 NRTIs 的敏感性。然而，Vpx 病毒样颗粒处理激活的 CD4(+) T 细胞仅轻微降低 NRTI 功效。此外，我们使用 HPLC 无法检测到 SAMHD1 介导的 NRTI-三磷酸水解，这验证了 SAMHD1 降解导致 HIV-1 对 NRTIs 敏感性降低很可能是由于细胞 dNTPs 的升高引起的。
