HMG-CoA还原酶调节网络在猪圆环病毒2型感染过程中的功能研究

HMG CoA reductase (HMGCR) is a transmembrane protein that is the rate-controlling enzyme of the mevalonate pathway. The intermediates of the mevalonate biosynthetic pathway play important roles in the post-translational modification of a number of proteins. In addition to its direct role in cholesterol synthesis, several studies have shown links between virus infection, interferon (IFN) response to virus infection and lipid biosynthetic pathways. In our previous research, we have examined the role of HMGCR during Porcine circovirus type 2 (PCV2) infection. The results demonstrated that the level of phosphorylated HMGCR, as an inactivated form of HMGCR, was increased in PCV2-infected cells. HMGCR was negatively associated with PCV2 infection and PCV2-induced apoptotic cell death. Atovastatin, inhibitors of HMGCR, significantly stimulated PCV2 replication and enhances PCV2-induced illness in vivo. Therefore, HMGCR might play an important direct role, such as participating in viral replicase complexes as an essential cofactor, or an indirect role in PCV2 replication. .In this project, inhibition mechanism of HMG-CoA reductase on PCV2 infection and PCV2-induced apoptotic cell death will be studied. Furthermore, the potential interactions between HMGCR and viral proteins will be evaluated. The data obtained in this project will provide new insights into the knowledge of host-pathogen interaction and pathogenic mechanisms of PCV2 infection, and will also give new ideas for blocking viral replication.

HMG-CoA还原酶（HMGCR）是胆固醇合成限速酶，且参与多种病毒的感染过程。我们发现，HMGCR通过调控JNK1/2信号通路抑制猪圆环病毒2型（PCV2）感染过程的早期阶段；抑制HMGCR可促进PCV2的感染及致病过程，也显著增强PCV2诱导的免疫反应；HMGCR对PCV2诱导的细胞凋亡过程有抑制作用。因此，推测HMGCR在PCV2感染过程中发挥调节作用，但其机制尚不明晰。本项目在前期研究基础上，以HMGCR为主要突破口，系统地分析HMGCR对PCV2复制以及PCV2诱导的细胞凋亡的调控机制，以期揭示“HMGCR调节网络在PCV2感染过程中的功能”这一重要科学问题。研究成果将为深入了解PCV2的感染及致病机制奠定基础，为探寻有效的防治方法提供理论依据，同时也将为病毒与宿主互作机制的研究提供更多的创新性观点。

猪圆环病毒2型（Porcine circovirus type 2，PCV2）引起猪圆环病毒病（Porcine circovirus diseases，PCVDs）或猪圆环病毒相关疾病（Porcine circovirus-associated diseases，PCVADs），严重危害全球养猪业。PCV2吸附在细胞表面的糖胺聚糖上，经胞吞入胞，并在胞内蛋白酶作用下将核酸释放进细胞质，之后，核酸在宿主因子的作用下转移至细胞核中进行复制，并依赖宿主元件进行组装，最后利用宿主因子释放出病毒粒子。因此，研究宿主因子在病毒感染过程中的作用有望解析PCV2的致病机制。.本研究分析PCV2感染PK-15细胞的转录组测序（RNA-Seq）结果，通过生物信息学分析筛选PCV2感染相关的宿主因子。发现PCV2感染过程中AMPK表达上调；PCV2感染早期促进HMGCR磷酸化水平，从而促进PCV2增殖；PCV2感染促进AMPK、PP2A的活性而抑制HMGCR的活性；PCV2感染早期，AMPK对HMGCR活性起主要调控作用，PP2A对HMGCR活性影响较小；另外，HMGCR与PCV2的Cap和Rep蛋白相互作用。.同时，RNA-seq分析筛选发现有10种猪源TRIMs表达差异显著。其中，TRIM21在PCV2感染的PK-15细胞中显著表达。进一步研究发现，TRIM21过表达可促进PCV2的增殖，而TRIM21敲除后产生相反结果。TRIM21在PCV2感染后促进IFNβ和IFNγ以及促炎因子IL-6和TNFα的表达。.骨髓细胞核分化抗原样蛋白（MNDAL）是干扰素诱导蛋白IFI200家族成员的一员。我们发现，MNDAL可能参与PCV2感染诱导的细胞凋亡。PCV2感染PK-15细胞后，TRIM21通过促进MNDAL和BCL-2的表达、抑制P53的产生，进而抑制PCV2感染诱导的细胞凋亡，最终促进PCV2的增殖。TRIM21与PCV2的Rep蛋白存在相互作用，且主要分布在细胞核周。.综上所述，PCV2通过平衡细胞凋亡、控制细胞周期、失活抗病毒蛋白、及活化干扰素反应等实现持续性感染，其中HMGCR及其调节网络在PCV2感染过程中的发挥重要作用。