Activation of adenosine A _2A receptor by lipids from docosahexaenoic acid revealed by NMR

Abstract

The lipid composition of the plasma membrane is a key parameter in controlling signal transduction through G protein–coupled receptors (GPCRs). Adenosine A2A receptor (A2AAR) is located in the lipid bilayers of cells, containing acyl chains derived from docosahexaenoic acid (DHA). For the NMR studies, we prepared A2AAR in lipid bilayers of nanodiscs, containing DHA chains and other acyl chains. The DHA chains in nanodiscs enhanced the activation of G proteins by A2AAR. Our NMR studies revealed that the DHA chains redistribute the multiple conformations of A2AAR toward those preferable for G protein binding. In these conformations, the rotational angle of transmembrane helix 6 is similar to that in the A2AAR–G protein complex, suggesting that the population shift of the equilibrium causes the enhanced activation of G protein by A2AAR. These findings provide insights into the control of neurotransmissions by A2AAR and the effects of lipids on various GPCR functions.

Structure and Dynamics of GPCRs in Lipid Membranes: Physical Principles and Experimental Approaches

“…A recent NMR study of A 2A AR embedded in lipid nanodiscs showed that DHA chains increased G protein activation [ 166 ]. A 2A AR bound to the full agonist was found in an equilibrium involving multiple active conformations of TM7.…”

“…Smaller discs also increase the risk of spurious interactions between the extramembranous regions of the embedded protein and the scaffold protein [ 273 ]. Commonly used variants in solution-state NMR studies of GPCRs are MSP1D1 and MSP1D1E3, which give disc sizes of ~9.6 and ~12 nm, respectively, requiring deuteration of the receptor for sufficient spectral quality [ 166 , 196 ].…”

“…MSPs have also facilitated studies looking at the relevance of specific varieties of alkyl tails on receptor activity. It has been demonstrated that the presence of DHA within the nanodisc stimulated G protein activation significantly, possibly by stabilising receptor conformations that couple more favourably to Gα, as observed by NMR [ 166 ].…”

Sub-millisecond conformational dynamics of the A2A adenosine receptor revealed by single-molecule FRET

“…On the picosecond-to-nanosecond timescale, some A 2A AR amino acids increase side-chain dynamics, while others become stabilized 18 . Sub-millisecond conformational variability was shown for both apo-form 19 and agonist-bound A 2A AR 16,17,20 .…”

“…The current information about A 2A AR conformational dynamics is based mostly on several reported NMR experiments [16][17][18][19][20][21][22] . In response to ligand binding, different A 2A AR amino acids either alter their sole stable conformations or vary relative probabilities of coexisting stable conformations 16,17 .…”