HIV-1 coreceptor activity of CCR5 and its inhibition by chemokines: Independence from G protein signaling and importance of coreceptor downmodulation
HIV-1 coreceptor activity of CCR5 and its inhibition by chemokines: Independence from G protein signaling and importance of coreceptor downmodulation
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DOI：
10.1006/viro.1997.8673
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发表时间：
1997-08-04
期刊：
影响因子：
3.7
通讯作者：
Berger, EA
中科院分区：
文献类型：
--
作者：
Alkhatib, G;Locati, M;Berger, EA
HIV-1感染需要CD 4+靶细胞上存在特异性趋化因子受体，以使病毒进入所涉及的融合反应成为可能。CCR 5是嗜巨噬细胞HIV-1分离株的主要融合共受体。HIV-1的进入和融合是由病毒包膜糖蛋白（Env）介导的，并被CCR 5配体抑制，但其机制尚不清楚。在这里，我们通过两种不同的方法测试G蛋白信号传导和CCR 5表面下调的作用;通过诱变直接灭活CCR 5信号传导和用百日咳毒素灭活G（i）型G蛋白。产生缺乏胞质C末端的最后45个氨基酸的CCR 5突变体（CCR 5（306）），其在转染细胞上以与表达CCR 5的细胞相当的水平表达，并显示正常的趋化因子结合亲和力，CCR 5配体在表达CCR 5的细胞中诱导钙通量和受体下调，但在表达CCR 5的细胞中不诱导（306）。然而，当与CD 4共表达时，CCR 5或CCR 5（306）支持相当的HIV-1 Env介导的细胞融合。与此一致，用百日咳毒素处理CCR 5表达细胞完全阻断配体诱导的瞬时钙流，但不影响Env介导的细胞融合或HIV-1感染。此外，百日咳毒素没有阻断Env介导的细胞融合或HIV-1感染的趋化因子抑制。然而，趋化因子对CCR 5（306）的Env介导的细胞融合的抑制效率低于CCR 5。我们的结论是，CCR 5的C-末端结构域是G蛋白信号传导和受体从表面下调的关键，但这两种功能都不是CCR 5融合辅助受体活性所必需的。CCR 5和CCR 5（306）的对比表型表明辅助受体下调和Env相互作用位点的直接阻断都有助于HIV-1感染的趋化因子抑制。(C)北京：科学出版社.
HIV-1 infection requires the presence of specific chemokine receptors on CD4+ target cells to enable the fusion reactions involved in virus entry. CCR5 is a major fusion coreceptor for macrophage-tropic HIV-1 isolates. HIV-1 entry and fusion are mediated by the viral envelope glycoprotein (Env) and are inhibited by CCR5 ligands, but the mechanisms are unknown. Here, we test the role of G protein signaling and CCR5 surface downmodulation by two separate approaches; direct inactivation of CCR5 signaling by mutagenesis and inactivation of G(i)-type G proteins with pertussis toxin. A CCR5 mutant lacking the last 45 amino acids of the cytoplasmic C-terminus (CCR5(306)) was created that was expressed on transfected cells at levels comparable to cells expressing CCR5 and displayed normal chemokine binding affinity, CCR5 ligands induced calcium flux and receptor downmodulation in cells expressing CCR5, but not in cells expressing CCR5(306). Nevertheless, CCR5 or CCR5(306), when coexpressed with CD4, supported comparable HIV-l Env-mediated cell fusion. Consistent with this, treatment of CCR5-expressing cells with pertussis toxin completely blocked ligand-induced transient calcium flux, but did not affect Env-mediated cell fusion or HIV-1 infection. Also, pertussis toxin did not block chemokine inhibition of Env-mediated cell fusion or HIV-1 infection. However, chemokines inhibited Env-mediated cell fusion less efficiently for CCR5(306) than for CCR5. We conclude that the C-terminal domain of CCR5 is critical for G protein signaling and receptor downmodulation from the surface, but that neither function is required for CCR5 fusion coreceptor activity. The contrasting phenotypes of CCR5 and CCR5(306) suggest that coreceptor downmodulation and direct blockage of Env interaction sites both contribute to chemokine inhibition of HIV-1 infection. (C) 1997 Academic Press.