Mechanistic insights into allosteric regulation of the A2A adenosine G protein-coupled receptor by physiological cations

Libin Ye,Oliver P Ernst,Régis Pomès,Nobuyuki Tsuchimura,Chris Neale,Dmitry Pichugin,Angel E García,Brent Lyda,Adnan Sljoka,R Scott Prosser,Sacha T Larda,Roger K Sunahara

doi:10.1038/s41467-018-03314-9

Abstract

Cations play key roles in regulating G-protein-coupled receptors (GPCRs), although their mechanisms are poorly understood. Here, 19F NMR is used to delineate the effects of cations on functional states of the adenosine A2A GPCR. While Na+ reinforces an inactive ensemble and a partial-agonist stabilized state, Ca2+ and Mg2+ shift the equilibrium toward active states. Positive allosteric effects of divalent cations are more pronounced with agonist and a G-protein-derived peptide. In cell membranes, divalent cations enhance both the affinity and fraction of the high affinity agonist-bound state. Molecular dynamics simulations suggest high concentrations of divalent cations bridge specific extracellular acidic residues, bringing TM5 and TM6 together at the extracellular surface and allosterically driving open the G-protein-binding cleft as shown by rigidity-transmission allostery theory. An understanding of cation allostery should enable the design of allosteric agents and enhance our understanding of GPCR regulation in the cellular milieu.

Highlights

Title Mechanistic insights into allosteric regulation of the A2A adenosine G protein-coupled receptor by physiological cations
19F NMR is used to delineate the effects of cations on functional states of the adenosine A2A G-protein-coupled receptors (GPCRs)
Humans have over 800 G-protein-coupled receptors (GPCRs), whose capacities to accomplish signaling through interaction with intracellular partners are regulated by extracellular ligands

Summary

Introduction

Title Mechanistic insights into allosteric regulation of the A2A adenosine G protein-coupled receptor by physiological cations. Positive allosteric effects of divalent cations are more pronounced with agonist and a G-protein-derived peptide. Divalent cations enhance both the affinity and fraction of the high affinity agonist-bound state. Humans have over 800 G-protein-coupled receptors (GPCRs), whose capacities to accomplish signaling through interaction with intracellular partners are regulated by extracellular ligands. Divalent Mg2+, Ca2+, and Mn2+ enhanced binding of μ-, δ-, and κ-opioid receptor agonists in brain homogenates[8,9]. Allosteric effects of Mg2+, Ca2+, and Na+ have been observed kwnitohwAn2tAoRa1l0lo–1s2tearincdalltyheremguulsactaerminaicnyMfa2mreiclyepCtoGr1P3C, wRsh1i4le–1C6.aM2+osist recently, high-resolution crystallographic studies of A2AR, the δ-opioid receptor, PAR1 protease activated receptor, and the β1-adrenergic receptor show that stabilizing a functionally inactive. The charged groups lining this pocket interface with an almost contiguous network of water molecules spanning the transmembrane domain and linking transmembrane helices (TM) 1, 2, 3, 6, and 7 in the inactive state

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Conclusion