G protein-coupled receptors (GPCRs) are versatile membrane proteins involved in the regulation of many physiological processes and pathological conditions, making them interesting pharmacological targets. In order to study their structure and function, GPCRs are traditionally extracted from membranes using detergents. However, due to their hydrophobic nature, intrinsic instability in aqueous solutions, and their denaturing effects, the isolation of properly folded and functional GPCRs is not trivial. Therefore, it is of crucial importance to solubilize receptors under mild conditions and control the sample quality subsequently. Here we describe widely used methods for small-scale GPCR solubilization, followed by quality control based on fluorescence size-exclusion chromatography, SDS-PAGE, temperature-induced protein unfolding (CPM dye binding) and fluorescent ligand binding assay. These methods can easily be used to assess the thermostability and functionality of a GPCR sample exposed to different conditions, such as the use of various detergents, addition of lipids and ligands, making them valuable for obtaining an optimal sample quality for structural and functional studies.
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http://dx.doi.org/10.1007/978-1-0716-0373-4_8 | DOI Listing |
Arthritis Rheumatol
December 2024
Department of Rheumatology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands.
Objective: Systemic sclerosis (SSc) is a rare but severe autoimmune disease characterized by immune dysregulation, fibrosis, and vasculopathy. While previous studies have highlighted the presence of functional autoantibodies targeting the angiotensin II type 1 receptor (ATR) and endothelin-1 type A receptor (ETR), leading to autoantibody-mediated receptor stimulation and subsequent activation of endothelial cells (ECs), a comprehensive understanding of the direct interaction between these autoantibodies and their receptors is currently lacking. Moreover, existing data confirming the presence of these autoantibodies in SSc often rely on similar methodologies and assays.
View Article and Find Full Text PDFCells
November 2023
Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire (IRIBHM), Université Libre de Bruxelles (ULB), 1070 Brussels, Belgium.
The Super-Conserved Receptors Expressed in the Brain (SREBs) form a subfamily of orphan G protein-coupled receptors, highly conserved in evolution and characterized by a predominant expression in the brain. The signaling pathways activated by these receptors (if any) are presently unclear. Given the strong conservation of their intracellular loops, we used a BioID2 proximity-labeling assay to identify protein partners of SREBs that would interact with these conserved domains.
View Article and Find Full Text PDFChembiochem
January 2024
Centre of Membrane Proteins and Receptors (COMPARE), University of Birmingham and University of Nottingham, Midlands, UK.
Measurements of membrane protein thermostability reflect ligand binding. Current thermostability assays often require protein purification or rely on pre-existing radiolabelled or fluorescent ligands, limiting their application to established targets. Alternative methods, such as fluorescence-detection size exclusion chromatography thermal shift, detect protein aggregation but are not amenable to high-throughput screening.
View Article and Find Full Text PDFSci Adv
May 2023
Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, 171 65 Solna, Sweden.
J Vis Exp
January 2023
Peak Proteins Ltd.;
During membrane protein structural elucidation and biophysical characterization, it is common to trial numerous protein constructs containing different tags, truncations, deletions, fusion partner insertions, and stabilizing mutations to find one that is not aggregated after extraction from the membrane. Furthermore, buffer screening to determine the detergent, additive, ligand, or polymer that provides the most stabilizing condition for the membrane protein is an important practice. The early characterization of membrane protein quality by fluorescent size exclusion chromatography provides a powerful tool to assess and rank different constructs or conditions without the requirement for protein purification, and this tool also minimizes the sample requirement.
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