Niss Arfelt Kristine, Fares Suzan, Sparre-Ulrich Alexander H, Hjortø Gertrud M, Gasbjerg Lærke S, Mølleskov-Jensen Ann-Sofie, Benned-Jensen Tau, Rosenkilde Mette M
Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Cell Signal. 2017 Jan;30:9-18. doi: 10.1016/j.cellsig.2016.11.009. Epub 2016 Nov 16.
G protein-coupled receptors (GPCRs) constitute a large protein family of seven transmembrane (7TM) spanning proteins that regulate multiple physiological functions. GPR87 is overexpressed in several cancers and plays a role in tumor cell survival. Here, the basal activity of GPR87 was investigated in transiently transfected HEK293 cells, revealing ligand-independent coupling to Gα, Gα and Gα. Furthermore, GPR87 showed a ligand-independent G protein-dependent activation of the downstream transcription factors CREB, NFκB, NFAT and SRE. In tetracycline-induced Flp-In T-Rex-293 cells, GPR87 induced cell clustering presumably through Gα coupling. In a foci formation assay using retrovirally transduced NIH3T3 cells, GPR87 showed a strong in vitro transforming potential, which correlated to the in vivo tumor induction in nude mice. Importantly, we demonstrate that the transforming potential of GPR87 was correlated to the receptor signaling, as the signaling-impaired mutant R139A (Arg in the conserved "DRY"-motif at the bottom of transmembrane helix 3 of GPR87 substituted to Ala) showed a lower in vitro cell transformation potential. Furthermore, R139A lost the ability to induce cell clustering. In summary, we show that GPR87 is active through several signaling pathways and that the signaling activity is linked to the receptor-induced cell transformation and clustering. The robust surface expression of GPR87 and general high druggability of GPCRs make GPR87 an attractive future anticancer target for drugs that - through inhibition of the receptor signaling - will inhibit its transforming properties.
G蛋白偶联受体（GPCRs）构成了一个由七个跨膜（7TM）跨膜蛋白组成的大蛋白家族，可调节多种生理功能。GPR87在多种癌症中过表达，并在肿瘤细胞存活中发挥作用。在此，我们在瞬时转染的HEK293细胞中研究了GPR87的基础活性，发现其与Gα、Gα和Gα存在不依赖配体的偶联。此外，GPR87显示出不依赖配体的G蛋白依赖性激活下游转录因子CREB、NFκB、NFAT和SRE。在四环素诱导的Flp-In T-Rex-293细胞中，GPR87可能通过Gα偶联诱导细胞聚集。在使用逆转录病毒转导的NIH3T3细胞进行的集落形成试验中，GPR87显示出强大的体外转化潜力，这与裸鼠体内肿瘤诱导相关。重要的是，我们证明GPR87的转化潜力与受体信号传导相关，因为信号受损的突变体R139A（GPR87跨膜螺旋3底部保守的“DRY”基序中的精氨酸被替换为丙氨酸）显示出较低的体外细胞转化潜力。此外，R139A失去了诱导细胞聚集的能力。总之，我们表明GPR87通过多种信号通路发挥作用，且信号活性与受体诱导的细胞转化和聚集相关。GPR87强大的表面表达以及GPCRs普遍的高可成药性使得GPR87成为未来一个有吸引力的抗癌靶点，通过抑制受体信号传导的药物将抑制其转化特性。
