Department of Structural Biology and Bioinformatics, Faculty of Medicine, University of Geneva, 1211 Geneva 4, Switzerland.
J Biol Chem. 2010 Dec 31;285(53):41772-80. doi: 10.1074/jbc.M110.153460. Epub 2010 Nov 1.
CC chemokine receptor 5 (CCR5), the major HIV coreceptor, is a G protein-coupled receptor (GPCR) involved in cell activation and migration in response to chemokines. Blockade of CCR5 is an effective anti-HIV strategy, and potent anti-HIV chemokine analogs such as PSC-RANTES have been developed. These inhibitors act by interfering with receptor trafficking, thereby inducing prolonged intracellular sequestration of CCR5. Like many GPCRs, CCR5 is desensitized following agonist activation. The initial steps in this process are well understood, but later stages, including where CCR5 is sequestered during desensitization, and how anti-HIV chemokine analogs intervene to achieve prolonged sequestration, have yet to be elucidated in detail. In this study we demonstrate that CCR5 cycles to and from the cell surface via the endosome recycling compartment and the trans-Golgi network during desensitization, accumulating in the trans-Golgi network following internalization by both PSC-RANTES and CCL5, the native ligand from which it was derived. In addition, we show that unlike CCR5 sequestered by CCL5, CCR5 sequestered by PSC-RANTES cannot be induced to return to the cell surface by addition of the small molecule CCR5 inhibitor, TAK-779, and that association of PSC-RANTES with CCR5 is more durable than that of native CCL5 during desensitization. Our findings reconcile the previously conflicting descriptions of the location of sequestered CCR5 during desensitization, as well as providing more general insights into potential trafficking routes for endocytosed GPCRs and further elucidation of the unusual inhibitory mechanism of chemokine analogs with potent anti-HIV activity.
CC 趋化因子受体 5（CCR5）是 HIV 的主要核心受体，是一种 G 蛋白偶联受体（GPCR），参与细胞激活和迁移以响应趋化因子。阻断 CCR5 是一种有效的抗 HIV 策略，已经开发出了强效的抗 HIV 趋化因子类似物，如 PSC-RANTES。这些抑制剂通过干扰受体运输起作用，从而诱导 CCR5 的长期细胞内隔离。与许多 GPCR 一样，CCR5 在激动剂激活后脱敏。该过程的初始步骤已被很好地理解，但后期阶段，包括脱敏过程中 CCR5 被隔离的位置以及抗 HIV 趋化因子类似物如何干预以实现长期隔离，尚未详细阐明。在这项研究中，我们证明了 CCR5 在脱敏过程中通过内体再循环区和反式高尔基体网络从细胞表面循环，并且在 PSC-RANTES 和其天然配体 CCL5 内化后积累在反式高尔基体网络中。此外，我们表明，与 CCL5 隔离的 CCR5 不同，PSC-RANTES 隔离的 CCR5 不能通过添加小分子 CCR5 抑制剂 TAK-779 诱导返回细胞表面，并且 PSC-RANTES 与 CCR5 的结合在脱敏过程中比天然 CCL5 更持久。我们的发现调和了先前关于脱敏过程中隔离的 CCR5 位置的描述，同时为内吞 GPCR 的潜在运输途径提供了更普遍的见解，并进一步阐明了具有强效抗 HIV 活性的趋化因子类似物的不寻常抑制机制。
