Sirtuin 2 Isoform 1通过AKT / GSK-3β/β-Catenin信号通路增强乙型肝

StephenW

Sirtuin 2 Isoform 1 Enhances Hepatitis B Virus RNA Transcription and DNA Synthesis through the AKT/GSK-3β/β-Catenin Signaling Pathway
Zahra Zahid Piracha, Hyeonjoong Kwon, Umar Saeed, Jumi Kim, Jaesung Jung, Yong-Joon Chwae, Sun Park, Ho-Joon Shin, Kyongmin Kim
J.-H. James Ou, Editor
DOI: 10.1128/JVI.00955-18

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ABSTRACT

Sirtuin 2 (Sirt2), a NAD+-dependent protein deacetylase, is overexpressed in many hepatocellular carcinomas (HCCs) and can deacetylate many proteins, including tubulins and AKT, prior to AKT activation. Here, we found that endogenous Sirt2 was upregulated in wild-type hepatitis B virus (HBV WT)-replicating cells, leading to tubulin deacetylation; however, this was not the case in HBV replication-deficient-mutant-transfected cells and 1.3-mer HBV WT-transfected and reverse transcriptase inhibitor (entecavir or lamivudine)-treated cells, but all HBV proteins were expressed. In HBV WT-replicating cells, upregulation of Sirt2 induced AKT activation, which consequently downregulated glycogen synthase kinase 3β (GSK-3β) and increased β-catenin levels; however, downregulation of Sirt2 in HBV-nonreplicating cells impaired AKT/GSK-3β/β-catenin signaling. Overexpression of Sirt2 isoform 1 stimulated HBV transcription and consequently HBV DNA synthesis, which in turn activated AKT and consequently increased β-catenin levels, possibly through physical interactions with Sirt2 and AKT. Knockdown of Sirt2 by short hairpin RNAs (shRNAs), inhibition by 2-cyano-3-[5-(2,5-dichlorophenyl)-2-furanyl]-N-5-quinolinyl-2-propenamide (AGK2), or dominant negative mutant expression inhibited HBV replication, reduced AKT activation, and decreased β-catenin levels. Through HBV infection, we demonstrated that Sirt2 knockdown inhibited HBV replication from transcription. Although HBx itself activates AKT and upregulates β-catenin, Sirt2-mediated signaling and upregulated HBV replication were HBx independent. Since constitutively active AKT inhibits HBV replication, the results suggest that upregulated Sirt2 and activated AKT may balance HBV replication to prolong viral replication, eventually leading to the development of HCC. Also, the results indicate that Sirt2 inhibition may be a new therapeutic option for controlling HBV infection and preventing HCC.

IMPORTANCE Even though Sirt2, a NAD+-dependent protein deacetylase, is overexpressed in many HCCs, and overexpressed Sirt2 promotes hepatic fibrosis and associates positively with vascular invasion by primary HCCs through AKT/GSK-3β/β-catenin signaling, the relationship between Sirt2, HBV, HBx, and/or HBV-associated hepatocarcinogenesis is unclear. Here, we show that HBV DNA replication, not HBV expression, correlates positively with Sirt2 upregulation and AKT activation. We demonstrate that overexpression of Sirt2 further increases HBV replication, increases AKT activation, downregulates GSK-3β, and increases β-catenin levels. Conversely, inhibiting Sirt2 decreases HBV replication, reduces AKT activation, and decreases β-catenin levels. Although HBx activates AKT to upregulate β-catenin, Sirt2-mediated effects were not dependent on HBx. The results also indicate that a Sirt2 inhibitor may control HBV infection and prevent the development of hepatic fibrosis and HCC.

StephenW

Sirtuin 2 Isoform 1通过AKT / GSK-3β/β-Catenin信号通路增强乙型肝炎病毒RNA转录和DNA合成
Zahra Zahid Piracha，Hyeonjoong Kwon，Umar Saeed，Jumi Kim，Jaesung Jung，Yong-Joon Chwae，Sun Park，Ho-Joon Shin，Kyongmin Kim
J.-H. James Ou，编辑
DOI：10.1128 / JVI.00955-18

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抽象

Sirtuin 2（Sirt2），一种NAD +依赖性蛋白质脱乙酰基酶，在许多肝细胞癌（HCC）中过表达，并且在AKT活化之前可以使许多蛋白质去乙酰化，包括微管蛋白和AKT。在这里，我们发现内源性Sirt2在野生型乙型肝炎病毒（HBV WT）复制细胞中上调，导致微管蛋白去乙酰化;然而，在HBV复制缺陷型突变体转染的细胞和1.3-mer HBV WT转染的和逆转录酶抑制剂（恩替卡韦或拉米夫定）处理的细胞中并非如此，但所有HBV蛋白均表达。在HBV WT复制细胞中，Sirt2的上调诱导AKT活化，从而下调糖原合成酶激酶3β（GSK-3β）和增加β-连环蛋白水平;然而，HBV非复制细胞中Sirt2的下调损害了AKT / GSK-3β/β-连环蛋白信号传导。 Sirt2同种型1的过表达刺激HBV转录并因此刺激HBV DNA合成，其反过来通过与Sirt2和AKT的物理相互作用激活AKT并因此增加β-连环蛋白水平。通过短发夹RNAs（shRNAs）敲低Sirt2，通过2-氰基-3- [5-（2,5-二氯苯基）-2-呋喃基] -N-5-喹啉基-2-丙烯酰胺（AGK2）抑制或占优势阴性突变体表达抑制HBV复制，降低AKT活化，降低β-连环蛋白水平。通过HBV感染，我们证明Sirt2敲低抑制HBV从转录复制。尽管HBx本身激活AKT并上调β-连环蛋白，但Sirt2介导的信号传导和上调的HBV复制是HBx独立的。由于组成型活性AKT抑制HBV复制，结果表明上调的Sirt2和活化的AKT可平衡HBV复制以延长病毒复制，最终导致HCC的发展。此外，结果表明Sirt2抑制可能是控制HBV感染和预防HCC的新治疗选择。

重要性尽管Sirt2是一种NAD +依赖性蛋白去乙酰化酶，在许多HCC中过表达，并且过表达的Sirt2通过AKT / GSK-3β/β-连环蛋白信号通过原发性HCC促进肝纤维化并与血管侵袭呈正相关，Sirt2与HBV，HBx和/或HBV相关的肝癌发生尚不清楚。在这里，我们显示HBV DNA复制，而不是HBV表达，与Sirt2上调和AKT激活正相关。我们证明Sirt2的过表达进一步增加HBV复制，增加AKT活化，下调GSK-3β，并增加β-连环蛋白水平。相反，抑制Sirt2可降低HBV复制，减少AKT活化，并降低β-连环蛋白水平。尽管HBx激活AKT以上调β-catenin，但Sirt2介导的作用不依赖于HBx。结果还表明，Sirt2抑制剂可以控制HBV感染并防止肝纤维化和HCC的发展。