Suphaphiphat Pirada, Essex Max, Lee Tun-Hou
Department of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Avenue, Boston, MA 02115, USA.
Virology. 2007 Mar 30;360(1):182-90. doi: 10.1016/j.virol.2006.10.019. Epub 2006 Nov 13.
The current model for HIV-1 envelope-coreceptor interaction depicts the V3 stem and bridging sheet binding to the CCR5 N-terminus while the V3 crown interacts with the second extracellular loop, which is the coreceptor domain that appears to be relatively more important for fusion and infection. Our prediction based on this model is that mutations in the V3 crown might consequently have more effects on cell-cell fusion and virus entry than mutations introduced in the V3 stem and C4 region. We performed alanine-scanning of the V3 loop and selected C4 residues in the JRFL envelope and tested the capacity of the resulting mutants for CCR5 binding, cell-cell fusion, and virus infection. Our cross comparison analysis revealed that residues in C4 and in both the V3 stem and crown were important for CCR5 binding of gp120 subunits. Contrary to our prediction, mutations in the V3 crown had less effect on membrane fusion than mutations in the V3 stem. The V3 stem thus appears to be the most important region for CCR5 utilization since it affected both coreceptor binding and subsequent fusion and viral entry. Our data raises the possibility that some residues in the V3 crown and in C4 may play distinct roles in the binding and fusion steps of envelope-coreceptor interaction.
目前的HIV-1包膜与共受体相互作用模型显示，V3茎和桥接片与CCR5的N端结合，而V3冠与第二个细胞外环相互作用，该细胞外环是共受体结构域，似乎对融合和感染相对更为重要。基于该模型，我们预测V3冠中的突变可能因此对细胞间融合和病毒进入的影响比V3茎和C4区域中引入的突变更大。我们对JRFL包膜中的V3环和选定的C4残基进行了丙氨酸扫描，并测试了所得突变体的CCR5结合、细胞间融合和病毒感染能力。我们的交叉比较分析表明，C4以及V3茎和冠中的残基对gp120亚基的CCR5结合很重要。与我们的预测相反，V3冠中的突变对膜融合的影响小于V3茎中的突变。因此，V3茎似乎是利用CCR5的最重要区域，因为它既影响共受体结合，又影响随后的融合和病毒进入。我们的数据增加了一种可能性，即V3冠和C4中的一些残基可能在包膜与共受体相互作用的结合和融合步骤中发挥不同作用。
