Intramembrane proteolysis and endoplasmic reticulum retention of hepatitis C virus core protein
Intramembrane proteolysis and endoplasmic reticulum retention of hepatitis C virus core protein
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DOI：
10.1128/jvi.78.12.6370-6380.2004
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发表时间：
2004-06-01
影响因子：
5.4
通讯作者：
Matsuura, Y
中科院分区：
文献类型：
--
作者：
Okamoto, K;Moriishi, K;Matsuura, Y
丙型肝炎病毒（HCV）核心蛋白C端疏水区定位于内质网（ER），C端疏水区作为核心蛋白的膜锚和El蛋白的信号序列。核心蛋白的信号序列由信号肽肽酶（SPP）进一步加工。我们研究了核心蛋白负责ER保留和加工的SPP区域。HCV核心蛋白缺失突变体的细胞内定位分析表明，不仅C-末端的信号锚序列，而且从氨基酸128至151的上游疏水区是必需的ER保留的核心蛋白。精确的突变分析表明，用Ala取代核心蛋白的Leu（139）、瓦尔（140）和Lett（144）抑制SPP的加工，但核心-E1连接处的信号肽酶切割得以维持。此外，加工的El蛋白被易位到ER中并用高甘露糖寡糖糖基化。尽管存在未加工的C-末端信号锚定序列，但来自突变体的核心蛋白被易位到细胞核中。虽然没有观察到核心蛋白与野生型SPP的直接关联，但功能丧失的SPP突变体的表达抑制了SPP对信号序列的切割以及与未加工的核心蛋白的免疫共沉淀。139 140 144这些结果表明，Leu（139），瓦尔（140）和Leu（144）在HCV核心蛋白的ER滞留和SPP切割中起关键作用。
Hepatitis C virus (HCV) core protein is suggested to localize to the endoplasmic reticulum (ER) through a C-terminal hydrophobic region that acts as a membrane anchor for core protein and as a signal sequence for El protein. The signal sequence of core protein is further processed by signal peptide peptidase (SPP). We examined the regions of core protein responsible for ER retention and processing by SPP. Analysis of the intracellular localization of deletion mutants of HCV core protein revealed that not only the C-terminal signal-anchor sequence but also an upstream hydrophobic region from amino acid 128 to 151 is required for ER retention of core protein. Precise mutation analyses indicated that replacement of Leu(139), Val(140), and Lett(144) of core protein by Ala inhibited processing by SPP, but cleavage at the core-E1 junction by signal peptidase was maintained. Additionally, the processed El protein was translocated into the ER and glycosylated with high-mannose oligosaccharides. Core protein derived from the mutants was translocated into the nucleus in spite of the presence of the unprocessed C-terminal signal-anchor sequence. Although the direct association of core protein with a wild-type SPP was not observed, expression of a loss-of-function SPP mutant inhibited cleavage of the signal sequence by SPP and coimmunoprecipitation with unprocessed core protein. 139 140 144 These results indicate that Leu(139), Val(140), and Leu(144) in core protein play crucial roles in the ER retention and SPP cleavage of HCV core protein.