A Basic Patch on α-Adaptin Is Required for Binding of Human Immunodeficiency Virus Type 1 Nef and Cooperative Assembly of a CD4-Nef-AP-2 Complex
A Basic Patch on α-Adaptin Is Required for Binding of Human Immunodeficiency Virus Type 1 Nef and Cooperative Assembly of a CD4-Nef-AP-2 Complex
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DOI：
10.1128/jvi.02227-08
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发表时间：
2009-03-15
影响因子：
5.4
通讯作者：
Bonifacino, Juan S.
中科院分区：
文献类型：
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作者：
Chaudhuri, Rittik;Mattera, Rafael;Bonifacino, Juan S.
人类免疫缺陷病毒1型Nef蛋白的一个关键功能是从感染细胞表面下调CD4。Nef被认为是通过将CD4的胞质尾部与内吞机制连接起来，从而增加CD4内化的速度。为了支持这一模型，已经报道了CD4、Nef和内吞接头复合物AP-2之间的弱二元相互作用。特别是，Nef c端柔性环中的二亮氨酸和双酸基序已被证明可以介导AP-2的α和西格玛2亚基的结合。在这里，我们报道了在α -适应蛋白上鉴定了Nef二酸基序的潜在结合位点。该位点由两个基本残基组成，赖氨酸-297和精氨酸-340，位于α -适应蛋白主干区域。这些残基的突变特异性地抑制了Nef结合AP-2和下调CD4的能力。我们也提供了证据表明，Nef上的二酸基序和α -适应蛋白上的基本贴片都是CD4-Nef-AP-2复合物协同组装所必需的。这种协同性解释了Nef如何能够有效地下调CD4，尽管三方复合体的组分之间存在微弱的二元相互作用。
A critical function of the human immunodeficiency virus type 1 Nef protein is the downregulation of CD4 from the surfaces of infected cells. Nef is believed to act by linking the cytosolic tail of CD4 to the endocytic machinery, thereby increasing the rate of CD4 internalization. In support of this model, weak binary interactions between CD4, Nef, and the endocytic adaptor complex, AP-2, have been reported. In particular, dileucine and diacidic motifs in the C-terminal flexible loop of Nef have been shown to mediate binding to a combination of the alpha and sigma 2 subunits of AP-2. Here, we report the identification of a potential binding site for the Nef diacidic motif on alpha-adaptin. This site comprises two basic residues, lysine-297 and arginine-340, on the alpha-adaptin trunk domain. The mutation of these residues specifically inhibits the ability of Nef to bind AP-2 and downregulate CD4. We also present evidence that the diacidic motif on Nef and the basic patch on alpha-adaptin are both required for the cooperative assembly of a CD4-Nef-AP-2 complex. This cooperativity explains how Nef is able to efficiently downregulate CD4 despite weak binary interactions between components of the tripartite complex.