The First Transmembrane Domain of the Hepatitis B Virus Large Envelope Protein Is Crucial for Infectivity
The First Transmembrane Domain of the Hepatitis B Virus Large Envelope Protein Is Crucial for Infectivity
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DOI：
10.1128/jvi.01026-09
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发表时间：
2009-11-15
影响因子：
5.4
通讯作者：
Gripon, Philippe
中科院分区：
文献类型：
--
作者：
Lepere-Douard, Charlotte;Trotard, Maud;Gripon, Philippe
乙型肝炎病毒 (HBV) 生命周期的早期阶段仍知之甚少。事实上，细胞表面的病毒受体和核衣壳被递送到受感染细胞的胞质溶胶的机制都尚未被确定。对前 S1、前 S2 和大部分包膜蛋白 S 结构域的广泛诱变研究揭示了 HBV 感染性所必需的两个区域的存在：前 S1 结构域的第 77 个残基和 S 结构域抗原环中的构象基序。此外，在 S 结构域的 N 末端，鉴定出了一个推定的融合肽，该肽与第一跨膜 (TM1) 结构域部分重叠，并且前面有可能包含多个蛋白水解切割位点的 PEST 序列。由于没有对可能与融合过程有关的这两个基序进行突变分析，我们决定研究在推定的融合肽和 PEST 序列中带有连续缺失或取代的病毒感染 HepaRG 细胞的能力。通过在 L 和 M 蛋白或 S 蛋白中引入突变，我们证明了以下内容：（i）在 L 蛋白的 TM1 结构域中，三个由四个残基组成的疏水簇对于感染性是必需的； (ii) 相同的簇对于 S 蛋白表达至关重要；最后，(iii) PEST 序列对于组装和感染过程都是可有可无的。
The early steps of the hepatitis B virus (HBV) life cycle are still poorly understood. Indeed, neither the virus receptor at the cell surface nor the mechanism by which nucleocapsids are delivered to the cytosol of infected cells has been identified. Extensive mutagenesis studies in pre-S1, pre-S2, and most of the S domain of envelope proteins revealed the presence of two regions essential for HBV infectivity: the 77 first residues of the pre-S1 domain and a conformational motif in the antigenic loop of the S domain. In addition, at the N-terminal extremity of the S domain, a putative fusion peptide, partially overlapping the first transmembrane (TM1) domain and preceded by a PEST sequence likely containing several proteolytic cleavage sites, was identified. Since no mutational analysis of these two motifs potentially implicated in the fusion process was performed, we decided to investigate the ability of viruses bearing contiguous deletions or substitutions in the putative fusion peptide and PEST sequence to infect HepaRG cells. By introducing the mutations either in the L and M proteins or in the S protein, we demonstrated the following: (i) that in the TM1 domain of the L protein, three hydrophobic clusters of four residues were necessary for infectivity; (ii) that the same clusters were critical for S protein expression; and, finally, (iii) that the PEST sequence was dispensable for both assembly and infection processes.