Identification of residues important for agonist recognition and activation in GPR40.
ABSTRACT GPR40 was formerly an orphan G protein-coupled receptor whose endogenous ligands have recently been identified as free fatty acids (FFAs). The receptor, now named FFA receptor 1, has been implicated in the pathophysiology of type 2 diabetes and is a drug target because of its role in FFA-mediated enhancement of glucose-stimulated insulin release. Guided by molecular modeling, we investigated the molecular determinants contributing to binding of linoleic acid, a C18 polyunsaturated FFA, and GW9508, a synthetic small molecule agonist. Twelve residues within the putative GPR40-binding pocket including hydrophilic/positively charged, aromatic, and hydrophobic residues were identified and were subjected to site-directed mutagenesis. Our results suggest that linoleic acid and GW9508 are anchored on their carboxylate groups by Arg(183), Asn(244), and Arg(258). Moreover, His(86), Tyr(91), and His(137) may contribute to aromatic and/or hydrophobic interactions with GW9508 that are not present, or relatively weak, with linoleic acid. The anchor residues, as well as the residues Tyr(12), Tyr(91), His(137), and Leu(186), appear to be important for receptor activation also. Interestingly, His(137) and particularly His(86) may interact with GW9508 in a manner dependent on its protonation status. The greater number of putative interactions between GPR40 and GW9508 compared with linoleic acid may explain the higher potency of GW9508.
Article: G-protein coupled receptors mediating long chain fatty acid signalling in the pancreatic beta-cell.[show abstract] [hide abstract]
ABSTRACT: It is increasingly clear that some of the effects of both free and derivatised long chain fatty acids in pancreatic beta-cells are mediated by a group of G-protein coupled receptors. Some of these display close structural homology while others are more divergent. This Commentary reviews the expression and functional roles of three such molecules, GPR40, GPR119 and GPR120. GPR40 is the best characterised of this group and appears to mediate the acute stimulatory effects of long chain fatty acids on insulin secretion. GPR40 has also been proposed as a potential mediator of fatty acid toxicity but this is more controversial. GPR119 is also involved in stimulation of insulin secretion and responds primarily to ethanolamide derivatives of long chain fatty acids and also to some lysophospholipids rather than to free fatty acids. It may represent a useful target for the development of new insulin secretagogues aimed to enhance insulin release in patients with type 2 diabetes. GPR120 is the most enigmatic of the lipid-responsive cell-surface receptors and its function remains to be established. It has been proposed to play a cytoprotective role in certain other cell types but it is unclear whether it fulfils a similar function in beta-cells.Biochemical pharmacology 09/2009; 78(12):1419-27. · 4.25 Impact Factor
Article: Molecular docking and molecular dynamics simulation studies of GPR40 receptor-agonist interactions.[show abstract] [hide abstract]
ABSTRACT: In order to explore the agonistic activity of small-molecule agonists to GPR40, AutoDock and GROMACS software were used for docking and molecular dynamics studies. A molecular docking of eight structurally diverse agonists (six carboxylic acids (CAs) agonist, and two non-carboxylic acids (non-CAs) agonist) was performed and the differences in their binding modes were investigated. Moreover, a good linear relationship based on the predicted binding affinities (pK(i)) determined by using AutoDock and experimental activity values (pEC50) was obtained. Then, the 10ns molecular dynamics (MD) simulations of three obtained ligand-receptor complexes embedded into the phospholipid bilayer were carried out. The position fluctuations of the ligands located inside the transmembrane domain were explored, and the stable binding modes of the three studied agonists were determined. Furthermore, the residue-based decomposition of interaction energies in three systems identified several critical residues for ligand binding.Journal of molecular graphics & modelling 02/2010; 28(8):766-74. · 2.17 Impact Factor
Article: ss-TEA: Entropy based identification of receptor specific ligand binding residues from a multiple sequence alignment of class A GPCRs.[show abstract] [hide abstract]
ABSTRACT: G-protein coupled receptors (GPCRs) are involved in many different physiological processes and their function can be modulated by small molecules which bind in the transmembrane (TM) domain. Because of their structural and sequence conservation, the TM domains are often used in bioinformatics approaches to first create a multiple sequence alignment (MSA) and subsequently identify ligand binding positions. So far methods have been developed to predict the common ligand binding residue positions for class A GPCRs. Here we present 1) ss-TEA, a method to identify specific ligand binding residue positions for any receptor, predicated on high quality sequence information. 2) The largest MSA of class A non olfactory GPCRs in the public domain consisting of 13324 sequences covering most of the species homologues of the human set of GPCRs. A set of ligand binding residue positions extracted from literature of 10 different receptors shows that our method has the best ligand binding residue prediction for 9 of these 10 receptors compared to another state-of-the-art method. The combination of the large multi species alignment and the newly introduced residue selection method ss-TEA can be used to rapidly identify subfamily specific ligand binding residues. This approach can aid the design of site directed mutagenesis experiments, explain receptor function and improve modelling. The method is also available online via GPCRDB at http://www.gpcr.org/7tm/.BMC Bioinformatics 08/2011; 12:332. · 2.75 Impact Factor