PreS1与受体NTCP相互作用在HBV脱包膜过程中的功能与机制研究

HBV大外膜蛋白preS1结构域的N端是识别受体的关键区域，我们曾利用这一区域的多肽发现了NTCP是HBV与HDV的功能性受体。此后，我们以及国内外其它团队在NTCP介导的病毒入侵机制方面取得了诸多进展。但是到目前为止，HBV脱包膜的机制还不清楚，preS1与NTCP是否在这一过程中发挥功能尚待研究。在原有工作基础上，我们分析发现紧邻受体结合位点的preS1中段含有一段疑似融合肽的区域，其疏水性对病毒感染性非常关键。结合以往研究，我们提出假说：preS1前段与NTCP结合后引起构象变化，激活preS1中段融合肽并引发HBV脱包膜的过程。我们将利用病毒反向遗传学、多肽功能鉴定、非天然氨基酸光交联、脂质体多肽展示等手段，深入探索preS1与NTCP介导HBV脱包膜的分子机制。阐明HBV脱包膜机制是全面理解HBV早期入侵过程的关键，对寻找新的药物靶点、开发新型抗HBV药物有重要意义。

The amino-terminal (N-terminal) region of preS1 domain on hepatitis B virus (HBV) large surface protein (L protein) is the key determinant for receptor binding. By using a photoactivatable preS1 lipopeptide, we identified sodium taurocholate cotransporting polypeptide (NTCP) as a functional receptor for both HBV and hepatitis δ virus (HDV). Later, we and others made significant progresses in studying the critical roles of NTCP in HBV entry. Yet, it remains enigmatic how HBV fusion was achieved and whether the preS1 domain and NTCP contribute to this process. Based on our extensive sequence analysis of the L protein and other preliminary data, we found that the preS1 middle sub-domain carries a conserved motif that resembles a viral fusion peptide, and its hydrophobicity is required for the viral infectivity. Here we hypothesize that: the N-terminal region of preS1 in the L protein interacts with NTCP and leads to a conformational change of preS1 to expose the potential fusion peptide in the preS1 middle sub-domain, which subsequently triggers the downstream membrane fusion and endosomal escape events. To test this hypothesis, we will employ viral reverse-genetics, peptide function analysis, unnatural amino acid based photo-crosslinking, and lipid-nanoparticle based peptide display to investigate the molecular mechanisms of HBV fusion. Understanding how HBV fuse with the endosomal membrane will provide a key piece of puzzle for the framework of HBV entry, and help identifying new drug targets and developing novel therapeutics.