Crystal structure of the incretin-bound extracellular domain of a G protein-coupled receptor

Abstract

Incretins, endogenous polypeptide hormones released in response to food intake, potentiate insulin secretion from pancreatic ␤ cells after oral glucose ingestion (the incretin effect). This response is signaled by the two peptide hormones glucose-dependent insulinotropic polypeptide (GIP) (also known as gastric inhibitory polypeptide) and glucagon-like peptide 1 through binding and activation of their cognate class 2 G protein-coupled receptors (GPCRs). Because the incretin effect is lost or significantly reduced in patients with type 2 diabetes mellitus, glucagon-like peptide 1 and GIP have attracted considerable attention for their potential in antidiabetic therapy. A paucity of structural information precludes a detailed understanding of the processes of hormone binding and receptor activation, hampering efforts to develop novel pharmaceuticals. Here we report the crystal structure of the complex of human GIP receptor extracellular domain (ECD) with its agonist, the incretin GIP 1-42. The hormone binds in an ␣-helical conformation in a surface groove of the ECD largely through hydrophobic interactions. The N-terminal ligand residues would remain free to interact with other parts of the receptor. Thermodynamic data suggest that binding is concomitant with structural organization of the hormone, resulting in a complex mode of receptor-ligand recognition. The presentation of a well structured, ␣-helical ligand by the ECD is expected to be conserved among other hormone receptors of this class.glucose-dependent insulinotropic polypeptide ͉ hormone binding ͉ diabetes mellitus ͉ x-ray

Binding specificity of the ectodomain of the parathyroid hormone receptor

“…This is consistent with the results of an Ala scanning analysis described by Dean et al [31] and of the recently published crystal structure of a PTH (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34) peptide in complex with the PTH1R ectodomain [12]. Here, we extend these investigations by testing the whole PTH ligand for interactions.…”

Molecular recognition of parathyroid hormone by its G protein-coupled receptor

“…However, these efforts have been hampered by technical difficulties in purifying soluble and functional proteins in the large quantities required for structural studies. Very recently, the structures of the receptor ECD-ligand complexes have been reported for the murine CRF receptor 2␤ (CRFR2␤) and the human GIPR (37,38). These structures reveal a similar scaffold of two antiparallel ␤-sheets, resembling a short consensus repeat (SCR) fold found in immunoglobins (37,38).…”

Stapled Vasoactive Intestinal Peptide (VIP) Derivatives Improve VPAC2 Agonism and Glucose-Dependent Insulin Secretion

“…Although a number of structure−activity relationships studies on VIP have been reported, 28,29 our design rationale was based on the hypothesis that VIP binds the VPAC 2 receptor in an α-helical conformation, in an analogous manner to that demonstrated for GIP binding the extracellular domain of its receptor. 30 28 ). With the latter null residues in mind, we felt that functionalization in these positions would retain both the active structure and original potency/selectivity profile, while shielding potentially susceptible protease cleavage sites.…”

“…We then transposed M 17 to I 17 , facilitating synthesis and purification of the native peptide, a well tolerated modification, which has been exploited in half-life extension strategies. 32 Incorporation of a C-terminal extension motif G 29 K 30 provided not only a potential reactive handle, but also acts to neutralize the macrodipole and offers helix-capping hydrogen bonds, based on the structure of receptor-bound GIP (Figure 1). Table 1 shows that the initial modifications made to wildtype VIP did not compromise functional VPAC 2 agonism, and therefore, I 17 -VIP-GK serves as a good reference peptide against which other analogues described here may be compared.…”