Abstract
As a critical member of G protein-coupled receptors (GPCRs), G protein-coupled receptor 120 (GPR120) is a potential target for many physiological diseases, such as type 2 diabetes mellitus, inflammation, and obesity. Considering that small-molecule fluorescent ligands can combine the advantages of visualization, high sensitivity and selectivity, we initially undertook an effort to develop a series of fluorescent ligands to track GPR120 and establish a method to screen GPR120 agonists. The representative fluorescent ligand N1 possesses suitable optical property, equitable biological activity, and high fluorescence imaging feasibility, therefore, based on compound N1, we subsequently founded a bioluminescence resonance energy transfer (BRET) competition binding assay to screen three series of sulfonamide GPR120 agonists we developed herein. The activity evaluation results revealed that compound D5 was a potent GPR120 agonist with high activity and selectivity. Moreover, compound D5 exhibited a significant glucose-lowering effect in db/db mice, which indicates its potential application in the treatment of type 2 diabetes mellitus in vivo. It is anticipated that our fluorescent ligand-based method is a useful toolbox and will find broad applications in the discovery of small-molecule agonists for GPR120.
Highlights
G protein-coupled receptors (GPCRs) are the most significant type of membrane protein family involved in signal transduction on the cell surface. (Civelli et al, 2013) They can stimulate signals outside the cell membrane into the cell through receptors on the cell membrane concerning the mechanisms of many diseases. (Ichimura et al, 2012; Hauser et al, 2017; Gurevich and Gurevich, 2019) G protein-coupled receptor 120 (GPR120) is one member of the GPCRs family, known as the ω3 fat receptor 1
Like other GPCRs, it contains an extracellular N-terminal domain, an intracellular C-terminal domain, (Shimpukade et al, 2012) and seven transmembrane structures. (Leung and Zhang, 2014) GPR120 is highly expressed in the small intestine of humans and mice, and abundantly in adipocytes and macrophages. (Hirasawa et al, 2005) Its expression level on tissues and cells reveals that GPR120 may be related to the presence of many diseases, such as diabetes, inflammation, and Abbreviations: BRET, bioluminescence resonance energy transfer; Ca2+, calcium ion; FFA4, free fatty acid receptor 4; GPCRs, G protein-coupled receptors; GPR40, G protein-coupled receptor 40; GPR120, G protein-coupled receptor 120; Rluc, Renilla luciferase
Sulfonamide Agonists for GPR120 obesity. (Leung and Zhang, 2014; Hilgendorf et al, 2019; Miyamoto et al, 2019) GPR120 can induce the secretion of GLP-1 under the induction of ω-3 fatty acids, which can inhibit eating and promote insulin synthesis. (Alvarez-Curto et al, 2016) when a ligand activates GPR120, β-arrestin2 can be recruited to the cell membrane and coupled with GPR120, and enter the cytoplasm through endocytosis, thereby inhibiting the binding of TAB1 and TAK1, and achieving the purpose of interfering with proinflammatory signaling. (Yan et al, 2013) GPR120 has become an essential target for diabetes, inflammation, and obesity
Summary
G protein-coupled receptors (GPCRs) are the most significant type of membrane protein family involved in signal transduction on the cell surface. (Civelli et al, 2013) They can stimulate signals outside the cell membrane into the cell through receptors on the cell membrane concerning the mechanisms of many diseases. (Ichimura et al, 2012; Hauser et al, 2017; Gurevich and Gurevich, 2019) G protein-coupled receptor 120 (GPR120) is one member of the GPCRs family, known as the ω3 fat receptor 1. (Hirasawa et al, 2005) Its expression level on tissues and cells reveals that GPR120 may be related to the presence of many diseases, such as diabetes, inflammation, and Abbreviations: BRET, bioluminescence resonance energy transfer; Ca2+, calcium ion; FFA4, free fatty acid receptor 4; GPCRs, G protein-coupled receptors; GPR40, G protein-coupled receptor 40; GPR120, G protein-coupled receptor 120; Rluc, Renilla luciferase. In 2014, Steven et al reported the first small sulfonamide compound, GSK137647A, with high agonistic activity with GPR120. (Liu et al, 2019) Because GSK137647A has high selectivity, we chose it as a recognition group to develop another series of small-molecule fluorescent ligands . Bioluminescence resonance energy transfer (BRET) is a mature method for detecting the interactions between proteinprotein and has been applied to GPCRs signal transduction and drug screening. Agonists with good preliminary BRET screening results are used for subsequent calcium ion (Ca2+) assay, bias test, (Rajagopal et al, 2011) and blood glucose experiment in mice. (McCoull et al, 2017)
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