Sodium taurocholate cotransporting polypeptide is a functional receptor for human hepatitis B and D virus.
Sodium taurocholate cotransporting polypeptide is a functional receptor for human hepatitis B and D virus.
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作者：
Yan H;Zhong G;Xu G;He W;Jing Z;Gao Z;Huang Y;Qi Y;Peng B;Wang H;Fu L;Song M;Chen P;Gao W;Ren B;Sun Y;Cai T;Feng X;Sui J;Li W
人类乙型肝炎病毒（HBV）感染和乙型肝炎相关疾病仍然是一个主要的公共卫生问题。合并丁型肝炎卫星病毒 (HDV) 感染的个体病情更为严重。两种病毒进入细胞都是由乙型肝炎病毒包膜蛋白介导的。大包膜蛋白的前 S1 结构域是受体结合的关键决定因素。然而，受体的身份尚不清楚。在这里，通过使用近零距离光交联和串联亲和纯化，我们发现前S1的受体结合区与牛磺胆酸钠共转运多肽（NTCP）特异性相互作用，NTCP是一种主要在肝脏中表达的多重跨膜转运蛋白。沉默 NTCP 可抑制 HBV 和 HDV 感染，而外源性 NTCP 表达使不敏感的肝癌细胞对这些病毒感染敏感。此外，用人类对应物替换无功能的猴子 NTCP 的氨基酸 157-165 赋予其支持两种病毒感染的能力。我们的结果表明 NTCP 是 HBV 和 HDV 的功能性受体。 DOI：http://dx.doi.org/10.7554/eLife.00049.001 与人类乙型肝炎病毒 (HBV) 相关的肝病每年导致约 100 万人死亡，全世界有超过 3.5 亿人感染该病毒。其中约 1500 万人还感染丁型肝炎病毒 (HDV)，这是乙型肝炎病毒的卫星病毒，这使他们面临更高的肝病（包括癌症）风险。已知病毒在被吞噬之前通过与肝细胞表面的受体结合而进入肝细胞。 HBV 和 HDV 的外层均由三种包膜蛋白组成，其中一种包膜蛋白中名为前 S1 结构域的区域已知在病毒与受体之间的相互作用中发挥核心作用，因此在感染细胞中发挥着核心作用。然而，乙型肝炎病毒受体的身份仍然是个谜。现在严等人。已经鉴定出该受体是牛磺胆酸钠共转运多肽。这种蛋白质简称为 NTCP，通常参与体内胆汁酸的循环。除人类外，已知只有两个物种易受人类乙型肝炎病毒和丁型肝炎病毒感染：黑猩猩和一种名为树鼩的小型哺乳动物。严等人。首先从树鼩中分离原代肝细胞，然后结合先进的纯化和质谱分析表明细胞表面的 NTCP 与 HBV 中的 pre-S1 结构域相互作用。随后，作者对人类和树鼩来源的肝细胞进行了一系列基因敲除实验：当编码 NTCP 的基因被沉默时，乙型肝炎病毒感染大大减少。此外，他们能够用来自人类和树鼩的 NTCP 转染 HepG2 细胞（广泛用于肝病研究，但不易受到 HBV 和 HDV 感染），使它们变得易感。同样，虽然猴子不易感染 HBV，但仅用人类对应物替换猴子 NTCP 中的 5 个氨基酸就足以使猴子 NTCP 成为病毒的功能受体。过去，由于缺乏合适的体外感染系统和动物模型，乙型肝炎的基础研究和抗病毒治疗的发展都受到阻碍。现在，Yan 等人的工作。这意味着将有可能使用 NTCP 补充的 HepG2 细胞来应对各种挑战，例如基本病毒进入/复制机制的基础研究和大规模药物筛选。 HBV 和 HDV 感染也有可能干扰 NTCP 执行的一些重要生理功能，因此研究与这些感染相关的其他疾病的医学科学家也可能会对这项最新工作感兴趣。 DOI：http://dx.doi.org/10.7554/eLife.00049.002
Human hepatitis B virus (HBV) infection and HBV-related diseases remain a major public health problem. Individuals coinfected with its satellite hepatitis D virus (HDV) have more severe disease. Cellular entry of both viruses is mediated by HBV envelope proteins. The pre-S1 domain of the large envelope protein is a key determinant for receptor(s) binding. However, the identity of the receptor(s) is unknown. Here, by using near zero distance photo-cross-linking and tandem affinity purification, we revealed that the receptor-binding region of pre-S1 specifically interacts with sodium taurocholate cotransporting polypeptide (NTCP), a multiple transmembrane transporter predominantly expressed in the liver. Silencing NTCP inhibited HBV and HDV infection, while exogenous NTCP expression rendered nonsusceptible hepatocarcinoma cells susceptible to these viral infections. Moreover, replacing amino acids 157–165 of nonfunctional monkey NTCP with the human counterpart conferred its ability in supporting both viral infections. Our results demonstrate that NTCP is a functional receptor for HBV and HDV. DOI: http://dx.doi.org/10.7554/eLife.00049.001 Liver diseases related to the human hepatitis B virus (HBV) kill about 1 million people every year, and more than 350 million people around the world are infected with the virus. Some 15 million of these people are also infected with the hepatitis D virus (HDV), which is a satellite virus of HBV, and this places them at an even higher risk of liver diseases, including cancer. The viruses are known to enter liver cells by binding to receptors on their surface before being engulfed. Both HBV and HDV have outer coats that consist of three kinds of envelope proteins, and a region called the pre-S1 domain in one of them is known to have a central role in the interaction between the viruses and the receptors and, therefore, in infecting the cells. However, the identity of the HBV receptor has remained a mystery. Now Yan et al. have identified this receptor to be sodium taurocholate cotransporting polypeptide. This protein, known as NTCP for short, is normally involved in the circulation of bile acids in the body. In addition to humans, only two species are known to be susceptible to infection by human HBV and HDV—chimpanzees and a small mammal known as the treeshrew. Yan et al. started by isolating primary liver cells from treeshrews, and then used a combination of advanced purification and mass spectrometry analysis to show that the NTCP on the surface of the cells interacts with the pre-S1 domain in HBV. The authors then performed a series of gene knockdown experiments on liver cells of both human and treeshrew origin: when the gene that codes for NTCP was silenced, HBV infection was greatly reduced. Moreover, they were able to transfect HepG2 cells—which are widely used in research into liver disease, but are not susceptible to HBV and HDV infection—with NTCP from humans and treeshrews to make them susceptible. Similarly, although monkeys are not susceptible to HBV, replacing just five amino acids in monkey NTCP with their human counterparts was enough to make the monkey NTCP a functional receptor for the viruses. In the past, basic research into HBV and the development of antiviral therapeutics have both been hindered by the lack of suitable in vitro infection systems and animal models. Now, the work of Yan et al. means that it will be possible to use NTCP-complemented HepG2 cells for challenges as diverse as fundamental studies of basic viral entry/replication mechanisms and large-scale drug screening. It is also possible that HBV and HDV infection might interfere with some of the important physiological functions carried out by NTCP, so the latest work could also be of interest to medical scientists working on other diseases related to these infections. DOI: http://dx.doi.org/10.7554/eLife.00049.002