Regulation of Melanoma Cell Malignancy by Compartmentalized Chemokine Receptor Signaling

项目摘要 黑色素瘤是最致命的皮肤癌，对晚期转移性皮肤癌患者几乎没有治疗选择 疾病。黑色素瘤细胞的增殖、存活、侵袭和淋巴转移与 趋化因子受体CCR7的表达。CCR7是高度可药物G蛋白偶联的成员 受体(GPCRs)超家族，促进细胞迁移和免疫细胞成熟。传统上，在 激动剂刺激，细胞膜上的GPCRs激活异三聚体G蛋白，导致下游 在整个细胞中发出信号。为了终止G蛋白信号，细胞设计了一种专门的 脱敏机制，包括GPCRK和随后的受体磷酸化 β-arrestins(β受体)在磷酸化受体上的募集。Gpr-βARRS相互作用既阻止了 G蛋白结合部位，促进受体内吞作用。然而，我们最近发现，一些GPCR 同时与G蛋白和βARR相互作用形成GPCRG蛋白-βARR‘Megaplex’，从而允许 受体继续刺激G蛋白信号转导，同时被β受体内化到内吞体内。我们的 初步结果表明，CCR7形成了这样的超级复合体，并继续刺激G蛋白信号转导 在被内化之后。拟议的项目旨在探讨这个内体CCR7的参与 黑色素瘤细胞恶性进展的信号转导。为此，我们开发了一种实验性的方法 将质膜CCR7信号启动的病理生理功能与内体CCR7分离 发信号。这种方法利用了两种天然趋化因子配体CCL19和CCL21，它们主要是 分别激活内体和质膜中的G蛋白。使用这些趋化因子来刺激 CCR7在HEK293细胞中，我们证明了来自不同细胞室的信号促进不同的 转录变化。特别是，我们观察到与胆固醇有关的关键基因上调。 内体CCR7信号反应生物合成，质膜CCR7信号增强 抑制Smads和其他与转化生长因子-β(转化生长因子-β)途径相关的基因的表达。 在黑色素瘤中，这两条途径被报道具有相反的作用，胆固醇的产生加速。 黑色素瘤细胞增殖和抑制Smads限制生长。因此，我们在这里建议测试 假设黑色素瘤中内体CCR7信号通过以下途径特异性地驱动致病细胞增殖 增强胆固醇的生物合成。这个项目的结果不仅将增强我们对如何 趋化因子受体的表达促进黑色素瘤的恶性，但也可能提供一种新的策略 开发有效的黑色素瘤治疗药物，通过将趋化因子受体靶向于内体隔室。

Project Summary Melanoma is the deadliest form of skin cancer with few treatment options to patients with advanced metastatic disease. Melanoma cell proliferation, survival, invasion, and metastasis to lymph nodes correlates with expression of the chemokine receptor CCR7. CCR7 is a member of the highly druggable G protein-coupled receptors (GPCRs) superfamily and promotes cell migration and maturation of immune cells. Classically, upon agonist stimulation, GPCRs at the cell membrane activate heterotrimeric G proteins, causing downstream signaling throughout the cell. In order to terminate G protein signaling, cells have devised a specialized desensitization mechanism that includes receptor phosphorylation by GPCR kinases and subsequent recruitment of β-arrestins (βarrs) to the phosphorylated receptors. The GPCR–βarrs interaction both blocks the G protein-binding site and promotes receptor endocytosis. However, we recently discovered that some GPCRs interact with G proteins and βarrs simultaneously to form GPCR–G protein–βarr `megaplexes', which allows the receptor to continue to stimulate G protein signaling while being internalized into endosomes by βarrs. Our preliminary results suggest that CCR7 forms such megaplexes and continues to stimulate G protein signaling after having been internalized. The proposed project aims to explore the involvement of this endosomal CCR7 signaling in malignant progression of melanoma cells. To this end, we have developed an experimental approach to separate pathophysiological functions initiated by plasma membrane CCR7 signaling from endosomal CCR7 signaling. This approach leverages two natural chemokine ligands, CCL19 and CCL21, which predominately activate G proteins from endosomes or plasma membrane, respectively. Using these chemokines to stimulate CCR7 in HEK293 cells, we demonstrate that signaling from different cellular compartments promote distinct transcriptional changes. In particular, we observed upregulation of key genes involved in the cholesterol biosynthesis in response to endosomal CCR7 signaling whereas plasma membrane CCR7 signaling enhanced the expression of inhibitory SMADs and other genes related to the transforming growth factor-β (TGF-β) pathway. In melanoma, these two pathways are reported to have opposite effects with cholesterol production accelerating melanoma cell proliferation and inhibitory SMADs limiting growth. Therefore, we here propose to test the hypothesis that endosomal CCR7 signaling in melanoma specifically drives pathogenic cell proliferation through enhanced cholesterol biosynthesis. The results from this project will not only enhance our understanding of how chemokine receptor expression promotes melanoma malignancy but might also provide a new strategy to develop effective melanoma therapeutics by targeting chemokine receptors at endosomal compartments.