DISSOCIATION OF THE CD4 DOWN-REGULATION AND VIRAL INFECTIVITY ENHANCEMENT FUNCTIONS OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 NEF
DISSOCIATION OF THE CD4 DOWN-REGULATION AND VIRAL INFECTIVITY ENHANCEMENT FUNCTIONS OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 NEF
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DOI：
10.1128/jvi.69.7.4112-4121.1995
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发表时间：
1995-07-01
影响因子：
5.4
通讯作者：
GREENE, WC
中科院分区：
文献类型：
--
作者：
GOLDSMITH, MA;WARMERDAM, MT;GREENE, WC
最近的证据表明，在细胞培养和体内模型中，人类免疫缺陷病毒1型的nef基因增强而不是抑制病毒复制。此外，nef改变了各种正常的细胞过程，包括CD4在细胞表面的显示。然而，目前尚不清楚传染性的增强和CD4的下调是否代表该单一蛋白的相关或独立的生物学特性。在目前的研究中，进行了突变分析，以确定介导这些作用的Nef蛋白的结构-功能关系。为了评估这些突变的功能后果，研究人员开发了敏感可靠的检测方法来量化Nef的病毒感染性增强和CD4下调功能。结果表明，Nef的N端膜靶向序列对Nef的两种功能都很重要，而其他一些保守区域对Nef的两种功能都是不可缺少的。保守的脯氨酸- x - x重复片段位于该蛋白的中心核心，类似于sh3结合域，对增强感染功能至关重要，但对CD4下调是必不可少的。然而，Nef对CD4的下调似乎涉及一个两步过程，需要从CD4初始解离p56(lck)，以允许CD4参与内吞装置。总之，这些发现表明，人类免疫缺陷病毒1型Nef的传染性增强和CD4下调活性是可以分离的。因此，这些过程在病毒复制周期中可能是相互独立的。
Recent evidence indicates that the nef gene of human immunodeficiency virus type 1 augments rather than inhibits viral replication in both cell culture and in vivo models. In addition, nef alters various normal cellular processes, including the display of CD4 on the cell surface. However, it remains unknown whether the enhancement of infectivity and the downregulation of CD4 represent linked or independent biologic properties of this single protein. In the present studies, mutational analyses were performed to define structure-function relationships within the Nef protein that mediate these effects. To assess the functional consequences of these mutations, sensitive and reliable assays were developed to quantitate the viral infectivity enhancement and CD4 downregulation functions of Nef. The results indicate that membrane-targeting sequences at the N terminus of Nef are important for both functions of Nef, while certain other conserved regions are dispensable for both functions. A conserved proline-X-X repeat segment in the central core of the protein, which is reminiscent of an SH3-binding domain, is critical for the enhancement of infectivity function but is dispensable for CD4 downregulation. However, the downregulation of CD4 by Nef appears to involve a two-step process requiring the initial dissociation of p56(lck) from CD4 to permit engagement of the endocytic apparatus by CD4. Together, these findings demonstrate that the infectivity enhancement and CD4 dowregulation activities of human immunodeficiency virus type 1 Nef can be dissociated. Thus, these processes may be independent of one another in the viral replication cycle.