Construction of GPR18 in silico model: the proposed agonist and antagonist, the mechanism of activation by itself

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Nouroddin Sotoudeh Chafi (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site:
Patricia Reggio

Abstract: GPR18 is an orphan G protein-coupled receptor (GPCR) that has been proposed to be the abnormal cannabidiol (Abn-CBD) receptor, a previously characterized atypical cannabinoid receptor for which the sequence was unknown. Recent studies show that GPR18 exhibits classical cannabinoid receptors (CB1 and CB2) biochemical functions in CB1-/- and CB2-/- knockout mice cells. Prior research has found GPR18 mRNA in a wide range of tissues from spleen, testis, and lymph nodes to peripheral blood leukocytes and phytohaemagglutinin-activated CD4+ T-cells. A variety of diverse therapeutic applications have been reported for the GPR18-ligand signaling system, including cell death via apoptosis, cell migration following central nervous system (CNS) injury or inflammation, regulation of intraocular pressure, sperm physiology, cardiac physiology, immunomodulation, obesity, cancer, pain, and resolution of acute inflammation. Whereas GPR18 is reported to be deorphanized, the lipid N-arachidonoyl glycine (NAGly) has been proposed to be the endogenous ligand of GPR18. However, more recent publications have reported a lack of GPR18 activation by NAGly. These apparent inconsistent findings were claimed to be related to lack of co-localization between NAGly and GPR18 in the body, but our experimental data show that both NAGly and the endogenous lipid mediator, resolvin D2 (RvD2), activate GPR18. Chapter I details an extensive background about the GPR18 discovery, pharmacological importance, related diseases, and the reported agonists and antagonists. Chapter II reports all of the biological tests and obtained experimental data. In this chapter, for the first time, two novel agonist and antagonist are proposed, which are more potent than the earlier reported competitors. These two ligands are CBD-derived compounds that researchers could use as a scaffold for future structure-related activity studies. Chapter III presents a detailed description of the methods employed for the construction of the active and inactive state of GPR18. The significant differences between the GPR18 sequences and the template crystal structure, and the techniques that were used to overcome challenges, are discussed in this chapter. Chapter IV then answers why the mutation of A3.39N reduces the constitutive activity in GPR18. In this chapter, by presenting the results of two series of Molecular Dynamics simulations, for the first time, a detailed mechanism of activation of GPR18 by itself is clarified. Chapter V investigates the quality of static model docking jobs presented in Chapter III. To this end, the researcher employed Molecular Dynamics and then analyzed the results. This chapter also explains why the ligand requires parameterization and how this could occur. The final chapter concerns the conclusions and future works. One crucial part of this project that remains to be done is the mutagenesis study. Chapter VI gives an extensive required mutation to improve the presented model in the future. This chapter also suggests a structure-activity relationship study based upon the discovered scaffold presented in Chapter II to modify the proposed ligands to enhance ligand bindings.

Additional Information

Language: English
Date: 2019
Cell receptors

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