High-resolution structure of the human GPR40 receptor bound to allosteric agonist TAK-875

Abstract

Human GPR40 receptor (hGPR40), also known as free fatty-acid receptor 1 (FFAR1), is a G-protein-coupled receptor that binds long-chain free fatty acids to enhance glucose-dependent insulin secretion. Novel treatments for type-2 diabetes mellitus are therefore possible by targeting hGPR40 with partial or full agonists. TAK-875, or fasiglifam, is an orally available, potent and selective partial agonist of hGPR40 receptor, which reached phase III clinical trials for the potential treatment of type-2 diabetes mellitus. Data from clinical studies indicate that TAK-875, which is an ago-allosteric modulator of hGPR40 (ref. 3), demonstrates improved glycaemic control and low hypoglycaemic risk in diabetic patients. Here we report the crystal structure of hGPR40 receptor bound to TAK-875 at 2.3 Å resolution. The co-complex structure reveals a unique binding mode of TAK-875 and suggests that entry to the non-canonical binding pocket most probably occurs via the lipid bilayer. The atomic details of the extensive charge network in the ligand binding pocket reveal additional interactions not identified in previous studies and contribute to a clear understanding of TAK-875 binding to the receptor. The hGPR40-TAK-875 structure also provides insights into the plausible binding of multiple ligands to the receptor, which has been observed in radioligand binding and Ca(2+) influx assay studies. Comparison of the transmembrane helix architecture with other G-protein-coupled receptors suggests that the crystallized TAK-875-bound hGPR40 complex is in an inactive-like state.

Application of GPCR Structures for Modelling of Free Fatty Acid Receptors

“…In 2014 a X-ray crystallographic structure of the human FFA1 in complex with the ago-allosteric ligand, TAK-875 provided unprecedented three-dimensional insight into molecular recognition at FFA1 (Srivastava et al 2014). The crystal structure revealed that TAK-875 binds to the site involving transmembrane helices 3-5 and the second extracellular loop (EL2).…”

“…The recent breakthrough in structural biology of GPCRs enabled crystallographic structures for 27 receptors of the rhodopsin family of GPCRs, including the FFA1 receptor. A FFA1 structure is solved in the complex with the ago-allosteric ligand, TAK-875 (Srivastava et al 2014) and provides a crucial point to study ligand recognition at FFA1. However, FFA2, FFA3, GPR120 and GPR84 have not been yet crystallized.…”

Development and Characterization of a Potent Free Fatty Acid Receptor 1 (FFA1) Fluorescent Tracer

“…4b, 18 The crystal structure of FFA1 in complex with 1 provided an explanation for this in showing the mesylpropoxy appendage to be protruding from the ligand binding pocket towards the lipid bilayer. 7 Thus, this seems to be an optimal linkage point for attachment of a spacer-extended fluorophore. In order to gain optimal fluorescent properties of the NBD fluorophore the compound should be attached to a primary aliphatic amine.…”

“…6 The recently published crystal structure of FFA1 in complex with 1 lent further support to the concept of multiple FFA1 binding sites, revealing several potential binding sites in addition to the site of 1. 7 Most importantly from a drug development standpoint, the specific binding site an FFA1 agonist interacts with may influence the ligand's downstream signaling outcomes, 2c and thus may have clear implications for the ultimate therapeutic efficacy of any developed FFA1 agonists. How these structurally similar ligands interact with their distinct binding sites on FFA1 remains poorly understood and, therefore, there is a clear need to develop novel tools to assess ligand binding to this receptor.…”

Free fatty acid receptor 1 (GPR40) agonists containing spirocyclic periphery inspired by LY2881835

“…23 Protein preparation, refinement and docking was performed within Schrödinger's Maestro, version 2016-1. 24 To prepare FFA1 for docking, hydrogens and missing atoms were added, alternate residue positions were defined and the hydrogen bonding network was further optimized by re-orientating hydroxyls, amides and imidazole rings (of histidine residues) using Protein Preparation Wizard.…”