👤 Adrian Dragan

We report the discovery of a chemical series that enhances ApoE secretion from human astrocytes through mechanisms independent of LXR agonism. Target deconvolution of hits from a phenotypic screen in astrocytoma cells employed chemoproteomics, photoaffinity probes, in vitro KINOMEscan analysis, and targeted siRNA knockdown experiments. Photoaffinity labeling coupled with quantitative chemical proteomics identified aryl hydrocarbon receptor (AhR), a transcription factor not previously associated with ApoE secretion, as the primary target. A diverse panel of AhR agonists and antagonists together with genetic knockdown confirmed that ApoE secretion increases when AhR activity is reduced. Using a luciferase reporter assay, we demonstrated that active series analogs exhibit AhR antagonism while inactive compounds do not. Since deletion of AhR has severe peripheral effects, chronic inhibition of AhR is not an attractive therapeutic approach for Alzheimer's disease; nevertheless, these results position AhR as a modulator of ApoE secretion and a biological pathway worth exploring. Show less

The gut hormone glucose-dependent insulinotropic polypeptide (GIP) signals via the GIP receptor (GIPR), resulting in postprandial potentiation of glucose-stimulated insulin secretion. The translation of results from rodent studies to human studies has been challenged by the unexpected effects of GIPR-targeting compounds. We, therefore, investigated the variation between species, focusing on GIPR desensitization and the role of the receptor C-terminus. The GIPR from humans, mice, rats, pigs, dogs and cats was studied in vitro for cognate ligand affinity, G protein activation (cAMP accumulation), recruitment of beta-arrestin and internalization. Variants of the mouse, rat and human GIPRs with swapped C-terminal tails were studied in parallel. The human GIPR is more prone to internalization than rodent GIPRs. Despite similar agonist affinities and potencies for G Desensitization of the human GIPR is dependent on the C-terminal tail. The species-dependent functionality of the C-terminal tail and the different species-dependent internalization patterns, especially between human and mouse GIPRs, are important factors influencing the preclinical evaluation of GIPR-targeting therapeutic compounds. This article is part of a themed issue Complexity of GPCR Modulation and Signaling (ERNST). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v182.14/issuetoc. Show less