TY - JOUR

T1 - Enhanced agonist residence time, internalization rate and signalling of the GIP receptor variant [E354Q] facilitate receptor desensitization and long-term impairment of the GIP system

AU - Gabe, Maria Buur Nordskov

AU - van der Velden, Wijnand J. C.

AU - Gadgaard, Sarina

AU - Smit, Florent Xavier

AU - Hartmann, Bolette

AU - Bräuner-Osborne, Hans

AU - Rosenkilde, Mette Marie

N1 - Special Issue: MiniReviews and Original Articles from the BCPT‐sponsored Focused Nordic Conference “GPCR Pharmacology – The Next Generation”, held in Copenhagen, Denmark, 31 October to 2 November 2018

PY - 2020

Y1 - 2020

N2 - In patients with type 2 diabetes mellitus (T2DM), the insulinotropic action of the GIP system is desensitized, whereas this is not the case for the GLP-1 system. This has raised an interesting discussion of whether GIP agonists or antagonists are most suitable for future treatment of T2DM together with GLP-1-based therapies. Homozygous carriers of the GIP receptor (GIPR) variant, [E354Q], display lower bone mineral density, increased bone fracture risk and slightly increased blood glucose. Here, we present an in-depth molecular pharmacological phenotyping of GIPR-[E354Q]. In silico modelling suggested similar interaction of the endogenous agonist GIP(1-42) to [E354Q] as to GIPR wt. This was supported by homologous competition binding in COS-7 cells revealing GIPR wt-like affinities of GIP(1-42) with K-d values of 2 nmol/L and wt-like agonist association rates (K-on). In contrast, the dissociation rates (K-off) were slower, resulting in 25% higher agonist residence time for GIPR-[E354Q]. Moreover, in G(alpha s) signalling (cAMP production) GIP(1-42) was 2-fold more potent and more efficacious on GIPR-[E354Q] compared to wt with 17.5% higher basal activity. No difference from GIPR wt was found in the recruitment of beta-arrestin 2, whereas the agonist-induced internalization rate was 2.1- to 2.3-fold faster for [E354Q]. Together with the previously described impaired recycling of [E354Q], our findings with enhanced signalling and internalization rate possibly explained by an altered ligand-binding kinetics will lead to receptor desensitization and down-regulation. This could explain the long-term functional impairment of the GIP system in bone metabolism and blood sugar maintenance for [E354Q] carriers and may shed light on the desensitization of the insulinotropic action of GIP in patients with T2DM.

AB - In patients with type 2 diabetes mellitus (T2DM), the insulinotropic action of the GIP system is desensitized, whereas this is not the case for the GLP-1 system. This has raised an interesting discussion of whether GIP agonists or antagonists are most suitable for future treatment of T2DM together with GLP-1-based therapies. Homozygous carriers of the GIP receptor (GIPR) variant, [E354Q], display lower bone mineral density, increased bone fracture risk and slightly increased blood glucose. Here, we present an in-depth molecular pharmacological phenotyping of GIPR-[E354Q]. In silico modelling suggested similar interaction of the endogenous agonist GIP(1-42) to [E354Q] as to GIPR wt. This was supported by homologous competition binding in COS-7 cells revealing GIPR wt-like affinities of GIP(1-42) with K-d values of 2 nmol/L and wt-like agonist association rates (K-on). In contrast, the dissociation rates (K-off) were slower, resulting in 25% higher agonist residence time for GIPR-[E354Q]. Moreover, in G(alpha s) signalling (cAMP production) GIP(1-42) was 2-fold more potent and more efficacious on GIPR-[E354Q] compared to wt with 17.5% higher basal activity. No difference from GIPR wt was found in the recruitment of beta-arrestin 2, whereas the agonist-induced internalization rate was 2.1- to 2.3-fold faster for [E354Q]. Together with the previously described impaired recycling of [E354Q], our findings with enhanced signalling and internalization rate possibly explained by an altered ligand-binding kinetics will lead to receptor desensitization and down-regulation. This could explain the long-term functional impairment of the GIP system in bone metabolism and blood sugar maintenance for [E354Q] carriers and may shed light on the desensitization of the insulinotropic action of GIP in patients with T2DM.

KW - GIP receptor

KW - GIPR-[E354Q]

KW - internalization

KW - signalling

U2 - 10.1111/bcpt.13289

DO - 10.1111/bcpt.13289

M3 - Journal article

C2 - 31299132

VL - 126

SP - 122

EP - 132

JO - Basic and Clinical Pharmacology and Toxicology

JF - Basic and Clinical Pharmacology and Toxicology

SN - 1742-7835

ER -