Fox James M, Kasprowicz Richard, Hartley Oliver, Signoret Nathalie
*Department of Biology and Hull York Medical School, Center for Immunology and Infection, University of York, York, United Kingdom; and Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland.
*Department of Biology and Hull York Medical School, Center for Immunology and Infection, University of York, York, United Kingdom; and Department of Pathology and Immunology, University of Geneva, Geneva, Switzerland
J Leukoc Biol. 2015 Jul;98(1):59-71. doi: 10.1189/jlb.2A0414-193RR. Epub 2015 May 8.
CCR5 is a chemokine receptor expressed on leukocytes and a coreceptor used by HIV-1 to enter CD4(+) T lymphocytes and macrophages. Stimulation of CCR5 by chemokines triggers internalization of chemokine-bound CCR5 molecules in a process called down-modulation, which contributes to the anti-HIV activity of chemokines. Recent studies have shown that CCR5 conformational heterogeneity influences chemokine-CCR5 interactions and HIV-1 entry in transfected cells or activated CD4(+) T lymphocytes. However, the effect of CCR5 conformations on other cell types and on the process of down-modulation remains unclear. We used mAbs, some already shown to detect distinct CCR5 conformations, to compare the behavior of CCR5 on in vitro generated human T cell blasts, monocytes and MDMs and CHO-CCR5 transfectants. All human cells express distinct antigenic forms of CCR5 not detected on CHO-CCR5 cells. The recognizable populations of CCR5 receptors exhibit different patterns of down-modulation on T lymphocytes compared with myeloid cells. On T cell blasts, CCR5 is recognized by all antibodies and undergoes rapid chemokine-mediated internalization, whereas on monocytes and MDMs, a pool of CCR5 molecules is recognized by a subset of antibodies and is not removed from the cell surface. We demonstrate that this cell surface-retained form of CCR5 responds to prolonged treatment with more-potent chemokine analogs and acts as an HIV-1 coreceptor. Our findings indicate that the regulation of CCR5 is highly specific to cell type and provide a potential explanation for the observation that native chemokines are less-effective HIV-entry inhibitors on macrophages compared with T lymphocytes.
CCR5是一种在白细胞上表达的趋化因子受体，是HIV-1进入CD4(+) T淋巴细胞和巨噬细胞所使用的共受体。趋化因子对CCR5的刺激会触发趋化因子结合的CCR5分子的内化，这一过程称为下调，它有助于趋化因子的抗HIV活性。最近的研究表明，CCR5构象异质性会影响趋化因子与CCR5的相互作用以及HIV-1进入转染细胞或活化的CD4(+) T淋巴细胞。然而，CCR5构象对其他细胞类型以及下调过程的影响仍不清楚。我们使用单克隆抗体（其中一些已被证明可检测不同的CCR5构象）来比较CCR5在体外生成的人T细胞母细胞、单核细胞、巨噬细胞衍生的巨噬细胞（MDM）和CHO-CCR5转染细胞上的行为。所有人类细胞都表达在CHO-CCR5细胞上未检测到的不同抗原形式的CCR5。与髓细胞相比，可识别的CCR5受体群体在T淋巴细胞上表现出不同的下调模式。在T细胞母细胞上，所有抗体都能识别CCR5，并且它会经历趋化因子介导的快速内化，而在单核细胞和MDM上，一部分CCR5分子可被一部分抗体识别，并且不会从细胞表面被清除。我们证明，这种细胞表面保留形式的CCR5对更强效的趋化因子类似物的延长处理有反应，并作为HIV-1共受体起作用。我们的研究结果表明，CCR5的调节对细胞类型具有高度特异性，并为天然趋化因子作为HIV进入抑制剂在巨噬细胞上比在T淋巴细胞上效果更差这一观察结果提供了一个潜在的解释。
