Interaction of lipids with the neurotensin receptor 1

Abstract

Information about lipid-protein interactions for G protein-coupled receptors (GPCRs) is scarce. Here, we use electron spin resonance (ESR) and spin-labelled lipids to study lipid interactions with the rat neurotensin receptor 1 (NTS1). A fusion protein containing rat NTS1 fully able to bind its ligand neurotensin was reconstituted into phosphatidylcholine (PC) bilayers at specific lipid:protein molar ratios. The fraction of motionally restricted lipids in the range of 40:1 to 80:1 lipids per receptor suggested an oligomeric state of the protein, and the result was unaffected by increasing the hydrophobic thickness of the lipid bilayer from C-18 to C-20 or C-22 chain length PC membranes. Comparison of the ESR spectra of different spin-labelled lipids allowed direct measurement of lipid binding constants relative to PC (Kr), with spin-labelled phosphatidylethanolamine (PESL), phosphatidylserine (PSSL), stearic acid (SASL), and a spin labelled cholesterol analogue (CSL) Kr values of 1.05±0.05, 1.92±0.08, 5.20±0.51 and 0.91±0.19, respectively. The results contrast with those from rhodopsin, the only other GPCR studied this way, which has no selectivity for the lipids analysed here. Molecular dynamics simulations of NTS1 in bilayers are in agreement with the ESR data, and point to sites in the receptor where PS could interact with higher affinity. Lipid selectivity could be necessary for regulation of ligand binding, oligomerisation and/or G protein activation processes. Our results provide insight into the potential modulatory mechanisms that lipids can exert on GPCRs.

Ligand activation induces different conformational changes in CXCR3 receptor isoforms as evidenced by plasmon waveguide resonance (PWR)

“…This could arise from the different partitioning of receptors in lipid domains (ordered/disordered) at the level of the plasma membrane 48 . The lipid environment could have an impact on receptor activation and signaling as it has been demonstrated for other receptor systems by PWR and other approaches 29 , 49 . It is possible that the N-terminal sequence in CXCR3-B will influence the interaction of the receptor with the surrounding lipids differently to CXCR3-A.…”

Closely related, yet unique: Distinct homo- and heterodimerization patterns of G protein coupled chemokine receptors and their fine-tuning by cholesterol

“…Since structural detail of GPCR dimer complexes is rather limited due to experimental restrictions, we employed extensive molecular dynamics simulations to investigate the dimerization process and gain first molecular insight into homo- and heterodimer structures of chemokine receptors in lipid bilayers. POPC lipid bilayers serve as a robust membrane mimetic to study the interactions between membrane components in a controlled environment [ 20 ]. Based on the observation that cholesterol plays an important role in regulating chemokine receptor function and dimerization [ 53 , 55 – 63 ], the effect of cholesterol on the protein association was additionally studied.…”

Nile Red-Based GPCR Ligands as Ultrasensitive Probes of the Local Lipid Microenvironment of the Receptor

“…18,19 Local alterations of the lipid microenvironment, such as the presence of highly organized lipid nanodomains, known as lipid rafts, can affect the conformation equilibrium of the transmembrane receptor, its affinity to ligands and its protein-protein interactions. [20][21][22][23][24][25] Therefore, studying the lipid microenvironment of receptors is of fundamental importance for understanding and modulating GPCR signaling. 26 However, the progress has been hampered by the lack of reliable experimental methods and by the multiple controversies related to the lipid raft hypothesis.…”