Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520-8011, USA.
Proc Natl Acad Sci U S A. 2009 Dec 1;106(48):20452-7. doi: 10.1073/pnas.0911679106. Epub 2009 Nov 17.
Lipid droplets are intracellular lipid-storage organelles that are thought to be derived from the endoplasmic reticulum (ER). Several pathogens, notably hepatitis C virus, use lipid droplets for replication. Numerous questions remain about how lipid droplets are generated and used by viruses. Here we show that the IFN-induced antiviral protein viperin, which localizes to the cytosolic face of the ER and inhibits HCV, localizes to lipid droplets. We show that the N-terminal amphipathic alpha-helix of viperin that is responsible for ER localization is also necessary and sufficient to localize both viperin and the fluorescent protein dsRed to lipid droplets. Point mutations in the alpha-helix that prevent ER association also disrupt lipid droplet association, and sequential deletion mutants indicate that the same number of helical turns are necessary for ER and lipid droplet association. Finally, we show that the N-terminal amphipathic alpha-helix of the hepatitis C viral protein NS5A can localize dsRed and viperin to lipid droplets. These findings indicate that the amphipathic alpha-helices of viperin and NS5A are lipid droplet-targeting domains and suggest that viperin inhibits HCV by localizing to lipid droplets using a domain and mechanism similar to that used by HCV itself.
脂滴是细胞内的脂质储存细胞器，被认为来源于内质网（ER）。一些病原体，特别是丙型肝炎病毒，利用脂滴进行复制。关于病毒如何产生和利用脂滴，仍有许多问题尚未解决。在这里，我们发现干扰素诱导的抗病毒蛋白 viperin 定位于 ER 的细胞质面并抑制 HCV，它也定位于脂滴。我们表明，viperin 负责 ER 定位的 N 端两亲性α-螺旋对于将 viperin 和荧光蛋白 dsRed 定位到脂滴也是必需且充分的。阻止 ER 结合的α-螺旋中的点突变也破坏了脂滴的结合，连续缺失突变表明 ER 和脂滴结合所需的螺旋数相同。最后，我们表明丙型肝炎病毒蛋白 NS5A 的 N 端两亲性α-螺旋可以将 dsRed 和 viperin 定位到脂滴。这些发现表明，viperin 和 NS5A 的两亲性α-螺旋是脂滴靶向结构域，并表明 viperin 通过使用与 HCV 自身相似的结构域和机制定位于脂滴来抑制 HCV。
