Fluorescence resonance energy transfer imaging reveals that chemokine-binding modulates heterodimers of CXCR4 and CCR5 receptors.
Fluorescence resonance energy transfer imaging reveals that chemokine-binding modulates heterodimers of CXCR4 and CCR5 receptors.
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DOI：
10.1371/journal.pone.0003424
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发表时间：
2008
期刊：
影响因子：
3.7
通讯作者：
Jin T
中科院分区：
文献类型：
--
作者：
Isik N;Hereld D;Jin T
二聚化已成为趋化因子G蛋白偶联受体的一个重要特征。CXCR4和CCR5调节白细胞的趋化作用，也是HIV进入的共同受体。在T细胞激活过程中，这两种受体都被招募到免疫突触中。然而，目前还不清楚它们是否形成异二聚体，以及配体结合是否调节二聚体的形成。利用灵敏的荧光共振能量转移(FRET)成像方法，我们研究了活细胞质膜上CCR5和CXCR4异源二聚体的形成。我们发现CCR5和CXCR4是以构型杂二聚体的形式存在的，并且CCR5和CXCR4的配体在这些预先存在的杂二聚体中促进了不同的构象变化。与CXCR4的配体相比，CCR5的配体诱导FRET效率明显增加，表明选择性的配体促进和稳定了杂二聚体的不同构象。我们还发现，CCR5 C末端的突变降低了它与CXCR4形成异二聚体的能力。此外，配体诱导了CXCR4和CCR5或CCR5STA和CCR5Δ4异二聚体的不同构象转变。综上所述，我们的数据提出了一个模型，即CXCR4和CCR5自发形成异二聚体，与CXCR4或CCR5的配体结合导致不同的构象变化，影响异二聚化，表明通过配体结合调节这些趋化因子受体的二聚化/功能的复杂性。
Dimerization has emerged as an important feature of chemokine G-protein-coupled receptors. CXCR4 and CCR5 regulate leukocyte chemotaxis and also serve as a co-receptor for HIV entry. Both receptors are recruited to the immunological synapse during T-cell activation. However, it is not clear whether they form heterodimers and whether ligand binding modulates the dimer formation. Using a sensitive Fluorescence Resonance Energy Transfer (FRET) imaging method, we investigated the formation of CCR5 and CXCR4 heterodimers on the plasma membrane of live cells. We found that CCR5 and CXCR4 exist as constitutive heterodimers and ligands of CCR5 and CXCR4 promote different conformational changes within these preexisting heterodimers. Ligands of CCR5, in contrast to a ligand of CXCR4, induced a clear increase in FRET efficiency, indicating that selective ligands promote and stabilize a distinct conformation of the heterodimers. We also found that mutations at C-terminus of CCR5 reduced its ability to form heterodimers with CXCR4. In addition, ligands induce different conformational transitions of heterodimers of CXCR4 and CCR5 or CCR5STA and CCR5Δ4. Taken together, our data suggest a model in which CXCR4 and CCR5 spontaneously form heterodimers and ligand-binding to CXCR4 or CCR5 causes different conformational changes affecting heterodimerization, indicating the complexity of regulation of dimerization/function of these chemokine receptors by ligand binding.
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