Hepatitis C Virus Infection Induces Hepatic Expression of NF-κB-Inducing Kinase and Lipogenesis by Downregulating miR-122.
Hepatitis C Virus Infection Induces Hepatic Expression of NF-κB-Inducing Kinase and Lipogenesis by Downregulating miR-122.
复制标题
丙型肝炎病毒感染通过下调 miR-122 诱导 NF-κB 诱导激酶和脂肪生成的肝脏表达。
作者：
Lowey,Brianna;Hertz,Laura;Chiu,Stephan;Valdez,Kristin;Li,Qisheng;Liang,TJake
丙型肝炎病毒（HCV）利用宿主依赖性感染人肝细胞。我们之前发现了IκB激酶α (IKK-α)在调节细胞脂肪生成和HCV组装中的关键作用。在本研究中，我们将NF-κ b诱导激酶（NIK）定义为IKK-α上游丝氨酸/苏氨酸激酶，参与IKK-α介导的前病毒效应，以及HCV利用这一先天途径发挥优势的机制。我们通过功能丧失和功能获得的方法控制了Huh7.5.1细胞中的NIK表达，并研究了对IKK-α激活、细胞脂质代谢和病毒组装的影响。我们证明NIK与IKK-α相互作用形成与应激颗粒相关的激酶复合物，其中IKK-α在HCV感染时被磷酸化。NIK的耗竭显著降低了细胞质脂滴含量，并损害了HCV颗粒的产生。NIK过表达增强了HCV的组装，而在IKK-α缺失的细胞中，这一过程被取消，这表明NIK作用于IKK-α的上游。在hcv感染的肝细胞、移植人肝细胞的malb - upa /Scidmice肝组织和慢性丙型肝炎患者中，NIK丰度增加。NIK mRNA在3 '非翻译区（UTR）含有一个miR-122种子序列结合位点。miR-122模拟物和发夹抑制剂直接影响NIK水平。在我们的肝脏模型中，miR-122水平因HCV感染而显著降低。我们证明了HNF4A，一种已知的pri-miR-122的转录调节因子，在HCV感染时下调。NIK是miR-122的真正靶点，HCV通过降低HNF4A表达下调miR-122的转录。这种效应，加上HCV复制对miR-122的隔离，导致NIK表达的“抑制”，从而解除对脂质代谢的调节。慢性丙型肝炎病毒（HCV）感染是一个主要的全球公共卫生问题。感染常常导致严重的肝损伤，并可能发展为肝硬化、肝细胞癌和死亡。HCV利用细胞机制进行繁殖，并在肝脏中引发病理过程。我们之前确定了IKK-α在调节细胞脂质代谢和HCV组装中的关键作用。在这项研究中，我们鉴定了NIK作用于IKK-α的上游，并鉴定了HCV如何利用这一先天途径发挥其优势。通过广泛的机制研究，我们证明NIK是miR-122的直接靶点，miR-122在转录水平上受肝细胞特异性转录因子HNF4A的调控。我们发现，在HCV感染中，NIK表达增加，而HNF4A和miR-122水平均降低。NIK是一种重要的宿主依赖性，与HCV组装、肝脏脂肪生成和miRNA生物学有关。
Hepatitis C virus (HCV) harnesses host dependencies to infect human hepatocytes. We previously identified a pivotal role of IκB kinase α (IKK-α) in regulating cellular lipogenesis and HCV assembly. In this study, we defined and characterized NF-κB-inducing kinase (NIK) as an IKK-α upstream serine/threonine kinase in IKK-α-mediated proviral effects and the mechanism whereby HCV exploits this innate pathway to its advantage. We manipulated NIK expression in Huh7.5.1 cells through loss- and gain-of-function approaches and examined the effects on IKK-α activation, cellular lipid metabolism, and viral assembly. We demonstrated that NIK interacts with IKK-α to form a kinase complex in association with the stress granules, in which IKK-α is phosphorylated upon HCV infection. Depletion of NIK significantly diminished cytosolic lipid droplet content and impaired HCV particle production. NIK overexpression enhanced HCV assembly, and this process was abrogated in cells deprived of IKK-α, suggesting that NIK acts upstream of IKK-α. NIK abundance was increased in HCV-infected hepatocytes, liver tissues fromAlb-uPA/Scidmice engrafted with human hepatocytes, and chronic hepatitis C patients. NIK mRNA contains an miR-122 seed sequence binding site in the 3′ untranslated region (UTR). miR-122 mimic and hairpin inhibitor directly affected NIK levels. In our hepatic models, miR-122 levels were significantly reduced by HCV infection. We demonstrated that HNF4A, a known transcriptional regulator of pri-miR-122, was downregulated by HCV infection. NIK represents a bona fide target of miR-122 whose transcription is downregulated by HCV through reduced HNF4A expression. This effect, together with the sequestering of miR-122 by HCV replication, results in “derepression” of NIK expression to deregulate lipid metabolism.IMPORTANCEChronic hepatitis C virus (HCV) infection is a major global public health problem. Infection often leads to severe liver injury that may progress to cirrhosis, hepatocellular carcinoma, and death. HCV coopts cellular machineries for propagation and triggers pathological processes in the liver. We previously identified a pivotal role of IKK-α in regulating cellular lipid metabolism and HCV assembly. In this study, we characterized NIK as acting upstream of IKK-α and characterized how HCV exploits this innate pathway to its advantage. Through extensive mechanistic studies, we demonstrated that NIK is a direct target of miR-122, which is regulated at the transcription level by HNF4A, a hepatocyte-specific transcription factor. We show in HCV infection that NIK expression is increased while both HNF4A and miR-122 levels are decreased. NIK represents an important host dependency that links HCV assembly, hepatic lipogenesis, and miRNA biology.