CXCR4, a member of the family of chemokine-activated G protein-coupled receptors, is widely expressed in immune response cells. It is involved in both cancer development and progression as well as viral infection, notably by HIV-1. A variety of methods, including structural information, have suggested the receptor may exist as a dimer or oligomer. However, the mechanistic details surrounding receptor oligomerization and its potential dynamic regulation remain unclear. Using both biochemical and biophysical means we confirm that CXCR4 can exist as a mixture of monomers, dimers and higher-order oligomers in cell membranes and show that oligomeric structure becomes more complex as receptor expression levels increase. Mutations of CXCR4 residues located at a putative dimerization interface result in monomerization of the receptor. Additionally, binding of the CXCR4 antagonist IT1t— a small, drug-like isothiourea derivative — rapidly destabilizes the oligomeric structure, while AMD3100, another well-characterized CXCR4 antagonist, does not. Although a mutation that regulates constitutive activity of CXCR4 also results in monomerization of the receptor, binding of IT1t to this variant promotes receptor dimerization. These results provide novel insights into the basal organization of CXCR4 and how antagonist ligands of different chemotypes differentially regulate its oligomerization state.

中文翻译：

---

趋化因子受体 CXCR4 寡聚化被拮抗剂配体 IT1t 选择性破坏

CXCR4 是趋化因子激活的 G 蛋白偶联受体家族的成员，广泛表达于免疫应答细胞中。它参与癌症的发生和进展以及病毒感染，尤其是 HIV-1。包括结构信息在内的多种方法表明受体可能以二聚体或寡聚体的形式存在。然而，受体寡聚化的机制细节及其潜在的动态调节仍不清楚。利用生物化学和生物物理手段，我们证实CXCR4可以作为单体、二聚体和高阶寡聚体的混合物存在于细胞膜中，并表明随着受体表达水平的增加，寡聚结构变得更加复杂。位于推定二聚化界面的 CXCR4 残基的突变导致受体单体化。此外，CXCR4 拮抗剂 IT1t（一种小型药物样异硫脲衍生物）的结合会迅速破坏寡聚结构的稳定性，而另一种充分表征的 CXCR4 拮抗剂 AMD3100 则不会。尽管调节 CXCR4 组成型活性的突变也会导致受体单体化，但 IT1t 与该变体的结合会促进受体二聚化。这些结果为 CXCR4 的基础组织以及不同化学型的拮抗剂配体如何差异调节其寡聚状态提供了新的见解。IT1t 与该变体的结合促进受体二聚化。这些结果为 CXCR4 的基础组织以及不同化学型的拮抗剂配体如何差异调节其寡聚状态提供了新的见解。IT1t 与该变体的结合促进受体二聚化。这些结果为 CXCR4 的基础组织以及不同化学型的拮抗剂配体如何差异调节其寡聚状态提供了新的见解。