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Nagarajan S, Qian ZY, Marimuthu P, Alkayed NJ, Kaul S, Barnes AP. Mapping the Molecular Architecture Required for Lipid-Binding Pockets Using a Subset of Established and Orphan G-Protein Coupled Receptors. J Chem Inf Model 2021; 61:3442-3452. [PMID: 34242503 DOI: 10.1021/acs.jcim.1c00335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
G-protein coupled receptors (GPCRs) sense a wide variety of stimuli, including lipids, and transduce signals to the intracellular environment to exert various physiological responses. However, the structural features of GPCRs responsible for detecting and triggering responses to distinct lipid ligands have only recently begun to be revealed. 14,15-epoxyeicosatrienoic acid (14,15-EET) is one such lipid mediator that plays an essential role in the vascular system, displaying both vasodilatory and anti-inflammatory properties. We recently reported multiple low-affinity 14,15-EET-binding GPCRs, but the mechanism by which these receptors sense 14,15-EET remains unclear. Here, we have taken a combined computational and experimental approach to identify and confirm critical residues and properties within the lipid-binding pocket. Furthermore, we generated mutants to engineer selected GPCR-predicted binding sites to either confer or abolish 14,15-EET-induced signaling. Our structure-function analyses indicate that hydrophobic and positively charged residues of the receptor-binding pocket are prerequisites for recognizing lipid ligands such as 14,15-EET and possibly other eicosanoids.
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Affiliation(s)
- Shanthi Nagarajan
- The Knight Cardiovascular Institute, Oregon Health Science University Portland, Portland, Oregon 97239, United States.,Medicinal Chemistry Core, Oregon Health Science University Portland, Portland, Oregon 97239, United States
| | - Zu Yuan Qian
- The Knight Cardiovascular Institute, Oregon Health Science University Portland, Portland, Oregon 97239, United States.,Department of Anesthesiology & Perioperative Medicine, Oregon Health Science University Portland, Portland, Oregon 97239, United States
| | - Parthiban Marimuthu
- Pharmaceutical Science Laboratory and Structural Bioinformatics Laboratory, Faculty of Science and Engineering, Åbo Akademi University, FI-20520 Turku, Finland
| | - Nabil J Alkayed
- The Knight Cardiovascular Institute, Oregon Health Science University Portland, Portland, Oregon 97239, United States.,Department of Anesthesiology & Perioperative Medicine, Oregon Health Science University Portland, Portland, Oregon 97239, United States
| | - Sanjiv Kaul
- The Knight Cardiovascular Institute, Oregon Health Science University Portland, Portland, Oregon 97239, United States
| | - Anthony P Barnes
- The Knight Cardiovascular Institute, Oregon Health Science University Portland, Portland, Oregon 97239, United States.,Department of Anesthesiology & Perioperative Medicine, Oregon Health Science University Portland, Portland, Oregon 97239, United States
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Chu KM, Chow KBS, Leung PK, Lau PN, Chan CB, Cheng CHK, Wise H. Over-expression of the truncated ghrelin receptor polypeptide attenuates the constitutive activation of phosphatidylinositol-specific phospholipase C by ghrelin receptors but has no effect on ghrelin-stimulated extracellular signal-regulated kinase 1/2 activity. Int J Biochem Cell Biol 2006; 39:752-64. [PMID: 17169600 DOI: 10.1016/j.biocel.2006.11.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2006] [Revised: 11/04/2006] [Accepted: 11/17/2006] [Indexed: 11/30/2022]
Abstract
In addition to regulating growth hormone release from the pituitary, ghrelin receptors also influence cell proliferation and apoptosis. By studying mitogen-activated protein kinase activity in human embryonic kidney 293 cells over-expressing ghrelin receptors, we aimed to identify the specific cell signalling pathways used by ghrelin receptors, and to determine if the truncated ghrelin receptor polypeptide had any influence on the functional activity of ghrelin receptors. We found that ghrelin activated extracellular signal-regulated kinases 1/2 with an EC50 value of 10 nM, and that this response was inhibited by the ghrelin receptor antagonists D-Lys3-GHRP-6 and [D-Arg1,D-Phe5,D-Trp(7,9),Leu11]-substance P. Ghrelin had little or no effect on the activity of c-Jun N-terminal kinase, p38 kinase or Akt. Ghrelin appeared to activate extracellular signal-regulated kinases 1/2 through a calcium-independent novel protein kinase C isoform which may utilize diacylglycerol derived from hydrolysis of phosphatidylcholine rather than from phosphatidylinositol. Ghrelin-stimulated extracellular signal-regulated kinases 1/2 activity was independent of transactivation of epidermal growth factor receptors, and even when ghrelin receptor internalization was blocked by concanavalin A or a beta-arrestin mutant, there was no decrease in phosphorylated extracellular signal-regulated kinases 1/2, suggesting this is a G protein-dependent process. The truncated ghrelin receptor polypeptide had no effect on ghrelin receptor signalling to extracellular signal-regulated kinases 1/2, but decreased the constitutive activation of phosphatidylinositol-specific phospholipase C by ghrelin receptors. In conclusion, our results suggest that any up-regulation of the truncated ghrelin receptor polypeptide might preferentially attenuate functional activity dependent on the constitutive activation of ghrelin receptors, while leaving ghrelin-dependent signalling unaffected.
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Affiliation(s)
- Kit-Man Chu
- Department of Pharmacology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, SAR, China
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