Imaging Ligand-Dependent Activation of CXCR7
Imaging Ligand-Dependent Activation of CXCR7
复制标题
DOI：
10.1593/neo.09724
复制
发表时间：
2009-10-01
期刊：
影响因子：
4.8
通讯作者：
Luker, Gary D.
中科院分区：
文献类型：
--
作者：
Luker, Kathryn E.;Gupta, Mudit;Luker, Gary D.
趋化因子CXCL12被认为在20多种不同癌症的原发肿瘤生长以及向转移性疾病进展的多个步骤中起促进作用。此前人们认为CXCL12的功能仅受受体CXCR4控制，但最近CXCR7被确定为该趋化因子的第二个受体。在小鼠模型中，CXCR7会增加肿瘤形成和转移，这表明该受体可能也是阻断CXCL12在癌症中作用的关键靶点。为了对完整细胞和活体小鼠中CXCR7的激活进行成像，我们验证了这样一个假设：趋化因子配体与CXCR7的结合会募集β - 抑制蛋白，这是一类与许多激活的趋化因子及相关七跨膜受体相互作用的胞质衔接蛋白。通过萤火虫荧光素酶蛋白片段互补实验，我们证实趋化因子配体CXCL12和CXCL11显著增加CXCR7与β - 抑制蛋白的结合，且受体优先与β - 抑制蛋白2相互作用。在用配体处理后，CXCR7和β - 抑制蛋白2之间相互作用的强度随时间增加，这与β - 抑制蛋白2和CXCR4的短暂结合形成对比。β - 抑制蛋白2增加了表达CXCR7的细胞对CXCL12的摄取，强调了CXCR7和β - 抑制蛋白2之间相互作用的功能相关性。在人乳腺癌原位异种移植模型中，我们利用生物发光成像来量化CXCR7和β - 抑制蛋白2结合的变化。这些研究表明CXCR7与β - 抑制蛋白2存在配体依赖性相互作用，这种相互作用促进趋化因子的积累，并建立了一种成像检测方法，用于在细胞实验和活体小鼠中检测趋化因子及候选治疗药物对CXCR7的动态调节。
Chemokine CXCL12 is proposed to promote multiple steps in growth of primary tumors and progression to metastatic disease in more than 20 different cancers. Functions of CXCL12 previously were believed to be controlled only by receptor CXCR4, but CXCR7 was recently identified as a second receptor for this chemokine. CXCR7 increases tumor formation and metastasis in mouse models, suggesting that this receptor may also be a key target for blocking effects of CXCL12 in cancer. To image activation of CXCR7 in intact cells and living mice, we tested the hypothesis that binding of chemokine ligands to CXCR7 recruits beta-arrestins, a family of cytosolic adapter proteins that interact with many activated chemokine and related seven-transmembrane receptors. Using firefly luciferase protein fragment complementation, we established that chemokine ligands CXCL12 and CXCL11 significantly increase association of CXCR7 and beta-arrestins with preferential interaction of the receptor with beta-arrestin 2. The magnitude of interactions between CXCR7 and beta-arrestin 2 increased over time after treatment with ligands, contrasting with transient association of beta-arrestin 2 and CXCR4. beta-Arrestin 2 increased uptake of CXCL12 in cells expressing CXCR7, emphasizing the functional relevance of the interaction between CXCR7 and beta-arrestin 2. In an orthotopic xenograft model of human breast cancer, we used bioluminescence imaging to quantify changes in the association of CXCR7 and beta-arrestin 2. These studies demonstrate ligand-dependent interactions of CXCR7 with beta-arrestin 2 that promote accumulation of chemokines and establish an imaging assay for the dynamic regulation of CXCR7 by chemokines and candidate therapeutic agents in cell-based assays and living mice.