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Updated: Jun 2, 2026

Enrichment of Mammalian Tissues and Xenopus Oocytes with Cholesterol
Published on: March 25, 2020
Cholesterol-induced conformational changes in the oxytocin receptor
Sabine Muth1, Anja Fries, Gerald Gimpl
1Department of Biochemistry, Institute of Pharmacy and Biochemistry, Gutenberg-University Mainz, Johann-Joachim Becherweg 30, D-55128 Mainz, Germany.
Abstract:
Recent studies suggest that cholesterol binding is widespread among GPCRs (G-protein-coupled receptors). In the present study, we analysed putative cholesterol-induced changes in the OTR [OT (oxytocin) receptor], a prototype of cholesterol-interacting GPCRs. For this purpose, we have created recombinant OTRs that are able to bind two small-sized fluorescence-labelled ligands simultaneously. An OTR antagonist was chosen as one of the ligands. To create a second ligand-binding site, a small-sized α-BTB (bungarotoxin binding) site was inserted at the N-terminus or within the third extracellular loop of the OTR. All receptor constructs were functionally active and bound both ligands with high affinity in the nanomolar range. Measurements of the quenching behaviour, fluorescence anisotropy and energy transfer of both receptor-bound ligands were performed to monitor receptor states at various cholesterol concentrations. The quenching studies suggested no major changes in the molecular environment of the fluorophores in response to cholesterol. The fluorescence anisotropy data indicated that cholesterol affects the dynamics or orientation of the antagonist. The energy transfer efficiency between both ligands clearly increased with increasing cholesterol. Overall, cholesterol induced both a changed orientation and a decreased distance of the receptor-bound ligands, suggesting a more compact receptor state in association with cholesterol.
Insights
Cholesterol binding affects G-protein-coupled receptors (GPCRs). This study shows cholesterol alters oxytocin receptor (OTR) dynamics, leading to a more compact receptor state by changing ligand orientation and distance.
Area of Science:
- Biochemistry
- Molecular Biology
- Pharmacology
Background:
- Cholesterol interactions are increasingly recognized for G-protein-coupled receptors (GPCRs).
- The oxytocin receptor (OTR) is a key GPCR known to interact with cholesterol.
Purpose of the Study:
- To investigate cholesterol-induced conformational changes in the OTR.
- To characterize how cholesterol affects OTR function and ligand binding dynamics.
Main Methods:
- Construction of recombinant OTRs with dual fluorescence-labeled ligand binding sites (antagonist and α-BTB).
- Utilized fluorescence spectroscopy techniques including quenching, anisotropy, and energy transfer.
- Monitored receptor states under varying cholesterol concentrations.
Main Results:
- Cholesterol did not significantly alter the molecular environment of the fluorophores.
- Cholesterol influenced the dynamics and orientation of the OTR antagonist ligand.
- Increased cholesterol concentration enhanced energy transfer efficiency between ligands, indicating decreased distance.
Conclusions:
- Cholesterol binding induces a more compact state in the oxytocin receptor.
- These findings suggest cholesterol plays a role in modulating GPCR conformation and dynamics.
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