Regulation of Melanoma Cell Malignancy by Compartmentalized Chemokine Receptor Signaling

项目摘要 黑色素瘤是皮肤癌中最致命的一种，晚期转移性黑色素瘤患者的治疗选择很少。 疾病黑色素瘤细胞增殖、存活、侵袭和淋巴结转移与 趋化因子受体CCR7的表达。CCR7是高度可药用的G蛋白偶联的 受体（GPCR）超家族并促进细胞迁移和免疫细胞成熟。传统上，在 在激动剂刺激下，细胞膜上的GPCR激活异源三聚体G蛋白，引起下游的GPCR反应。 在整个细胞中传递信号。为了终止G蛋白信号，细胞设计了一种专门的 脱敏机制，包括受体磷酸化的GPCR激酶和随后的 β-抑制蛋白（β arrs）向磷酸化受体的募集。GPCR-β arrs相互作用既能阻断 G蛋白结合位点并促进受体内吞作用。然而，我们最近发现， 同时与G蛋白和β arrs相互作用，形成GPCR-G蛋白-β arrs "megaplex"， 受体继续刺激G蛋白信号传导，同时被β arrs内化到内体中。我们 初步结果表明，CCR7形成这样的megaplex并继续刺激G蛋白信号传导 在被内化之后。拟议的项目旨在探索这种内体CCR7参与 黑色素瘤细胞恶性进展中的信号传导。为此，我们开发了一种实验方法， 分离由质膜CCR7信号传导启动的病理生理功能， 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 分别从内体或质膜激活G蛋白。用这些趋化因子来刺激 在HEK293细胞中，我们证明了来自不同细胞区室的信号传导促进了不同的CCR7表达。 转录变化。特别是，我们观察到与胆固醇相关的关键基因的上调， 响应于内体CCR7信号传导，而质膜CCR7信号传导增强了细胞的生物合成。 抑制性SMADs和其他与转化生长因子-β（TGF-β）通路相关的基因的表达。 在黑色素瘤中，据报道这两种途径具有相反的作用，加速胆固醇的产生 黑色素瘤细胞增殖和限制生长的抑制性SMAD。因此，我们在这里建议测试 黑色素瘤中的内体CCR7信号传导通过以下途径特异性驱动致病细胞增殖的假设 增强胆固醇生物合成。该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， 通过靶向内体区室的趋化因子受体开发有效的黑素瘤治疗剂。

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.