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Monitoring Solution Structures of Peroxisome Proliferator-Activated Receptor ?/? upon Ligand Binding.

ABSTRACT: Peroxisome proliferator-activated receptors (PPARs) have been intensively studied as drug targets to treat type 2 diabetes, lipid disorders, and metabolic syndrome. This study is part of our ongoing efforts to map conformational changes in PPARs in solution by a combination of chemical cross-linking and mass spectrometry (MS). To our best knowledge, we performed the first studies addressing solution structures of full-length PPAR-?/?. We monitored the conformations of the ligand-binding domain (LBD) as well as full-length PPAR-?/? upon binding of two agonists. (Photo-) cross-linking relied on (i) a variety of externally introduced amine- and carboxyl-reactive linkers and (ii) the incorporation of the photo-reactive amino acid p-benzoylphenylalanine (Bpa) into PPAR-?/? by genetic engineering. The distances derived from cross-linking experiments allowed us to monitor conformational changes in PPAR-?/? upon ligand binding. The cross-linking/MS approach proved highly advantageous to study nuclear receptors, such as PPARs, and revealed the interplay between DBD (DNA-binding domain) and LDB in PPAR-?/?. Our results indicate the stabilization of a specific conformation through ligand binding in PPAR-?/? LBD as well as full-length PPAR-?/?. Moreover, our results suggest a close distance between the N- and C-terminal regions of full-length PPAR-?/? in the presence of GW1516. Chemical cross-linking/MS allowed us gaining detailed insights into conformational changes that are induced in PPARs when activating ligands are present. Thus, cross-linking/MS should be added to the arsenal of structural methods available for studying nuclear receptors.

SUBMITTER: Schwarz R

PROVIDER: S-EPMC4798536 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Monitoring Solution Structures of Peroxisome Proliferator-Activated Receptor β/δ upon Ligand Binding.

Schwarz Rico R Tänzler Dirk D Ihling Christian H CH Sinz Andrea A

PloS one 20160318 3

Peroxisome proliferator-activated receptors (PPARs) have been intensively studied as drug targets to treat type 2 diabetes, lipid disorders, and metabolic syndrome. This study is part of our ongoing efforts to map conformational changes in PPARs in solution by a combination of chemical cross-linking and mass spectrometry (MS). To our best knowledge, we performed the first studies addressing solution structures of full-length PPAR-β/δ. We monitored the conformations of the ligand-binding domain ( ...[more]

PMID: 26992147

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Project description:BackgroundHumans are exposed to a complex mixture of environmental chemicals that impact bone and metabolic health, and traditional exposure assessments struggle to capture these exposure scenarios. Peroxisome proliferator activated receptor-gamma (PPARγ) is an essential regulator of metabolic and bone homeostasis, and its inappropriate activation by environmental chemicals can set the stage for adverse health effects. Here, we present the development of the Serum PPARγ Activity Assay (SPAA), a simple and cost-effective method to measure total ligand activity in small volumes of serum.MethodsFirst, we determined essential components of the bioassay. Cos-7 cells were transfected with combinations of expression vectors for human PPARγ and RXRα, the obligate DNA-binding partner of PPARγ, along with PPRE (DR1)-driven luciferase and control eGFP reporter constructs. Transfected cells were treated with rosiglitazone, a synthetic PPARγ ligand and/or LG100268, a synthetic RXR ligand, to characterize the dose response and determine the simplest and most efficacious format. Following optimization of the bioassay, we assessed the cumulative activation of PPARγ by ligands in serum from mice treated with a PPARγ ligand and commercial human serum samples.ResultsCos-7 cells endogenously express sufficient RXR to support efficacious activation of transfected PPARγ. Co-transfection of an RXR expression vector with the PPARγ expression vector did not increase PPRE transcriptional activity induced by rosiglitazone. Treatment with an RXR ligand marginally increased PPRE transcriptional activity in the presence of transfected PPARγ, and co-treatment with an RXR ligand reduced rosiglitazone-induced PPRE transcriptional activity. Therefore, the final bioassay protocol consists of transfecting Cos-7 cells with a PPARγ expression vector along with the reporter vectors, applying rosiglitazone standards and/or 10 μL of serum, and measuring luminescence and fluorescence after a 24 h incubation. Sera from mice dosed with rosiglitazone induced PPRE transcriptional activity in the SPAA in a dose-dependent and PPARγ-dependent manner. Additionally, human serum from commercial sources induced a range of PPRE transcriptional activities in a PPARγ-dependent manner, demonstrating the ability of the bioassay to detect potentially low levels of ligands.ConclusionsThe SPAA can reliably measure total PPRE transcriptional activity in small volumes of serum. This system provides a sensitive, straightforward assay that can be reproduced in any cell culture laboratory.

Dataset Information

Monitoring Solution Structures of Peroxisome Proliferator-Activated Receptor ?/? upon Ligand Binding.

Publications

Monitoring Solution Structures of Peroxisome Proliferator-Activated Receptor β/δ upon Ligand Binding.

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