M3毒蕈碱乙酰胆碱受体(M3R)是一种G蛋白偶联受体(GPCR),可调节重要的生理过程,包括血管张力,支气管收缩,和胰岛素分泌。它在各种各样的细胞类型上表达,包括胰腺β,平滑肌,神经元,和免疫细胞。激动剂与M3R的结合被认为主要通过异源三聚体G蛋白Gq启动细胞内信号传导事件。然而,有关M3R与Gq以外的其他G蛋白偶联的能力的报道有所不同。使用来自四个主要G蛋白家族的成员(Gq,Gi,Gs,和G13)在放射性配体结合中,GTP周转实验,和细胞信号测定,包括活细胞G蛋白解离和cAMP和肌醇三磷酸的第二信使评估,我们发现其他G蛋白家族,尤其是Gi和Gs,也可以与人类M3R交互。我们进一步表明,通过经典第二信使信号事件的扩增评估,这些相互作用是有效的。我们的发现表明,M3R在G蛋白相互作用方面比以前认识到的更加混杂。意义陈述研究表明,人M3毒蕈碱乙酰胆碱受体(M3R),以其在不同生理过程中的关键作用而闻名,不仅如先前所知通过Gq激活细胞内信号传导,而且在功能上与其他G蛋白家族相互作用,比如Gi和Gs,扩大了我们对其介导细胞反应的多功能性的理解。这些发现表明由M3R控制的更广泛和更复杂的调节网络,并对治疗靶向具有意义。
The M3 muscarinic acetylcholine receptor (M3R) is a G protein-coupled receptor (GPCR) that regulates important physiologic processes, including vascular tone, bronchoconstriction, and insulin secretion. It is expressed on a wide variety of cell types, including pancreatic beta, smooth muscle, neuronal, and immune cells. Agonist binding to the M3R is thought to initiate intracellular signaling events primarily through the heterotrimeric G protein Gq. However, reports differ on the ability of M3R to couple to other G proteins beyond Gq. Using members from the four primary G protein families (Gq, Gi, Gs, and G13) in radioligand binding, GTP turnover experiments, and cellular signaling assays, including live cell G protein dissociation and second messenger assessment of cAMP and inositol trisphosphate, we show that other G protein families, particularly Gi and Gs, can also interact with the human M3R. We further show that these interactions are productive as assessed by amplification of classic second messenger signaling events. Our findings demonstrate that the M3R is more promiscuous with respect to G protein interactions than previously appreciated. SIGNIFICANCE STATEMENT: The study reveals that the human M3 muscarinic acetylcholine receptor (M3R), known for its pivotal roles in diverse physiological processes, not only activates intracellular signaling via Gq as previously known but also functionally interacts with other G protein families such as Gi and Gs, expanding our understanding of its versatility in mediating cellular responses. These findings signify a broader and more complex regulatory network governed by M3R and have implications for therapeutic targeting.