Daugvilaite, Viktorija, Madsen, Christian Medom, Lückmann, Michael, Echeverria, Clara Castello, Sailer, Andreas, Frimurer, Thomas Michael, Rosenkilde, Mette Marie and Benned-Jensen, Tau (2017) Biased signaling and allosteric modulation of G protein-coupled receptor 183 - a 7TM receptor also known as Epstein-Barr virus -induced gene 2. British journal of pharmacology. ISSN 1476-5381; 0007-1188

Abstract

Abstract
Background and Purpose
The G protein-coupled receptor Epstein Barr virus-induced gene 2 (EBI2, also known as GPR183) is activated by oxysterols and plays a pivotal role for proper B cell migration during immune responses. While the molecular basis of agonist binding has been addressed in several studies, the concept of biased signaling of EBI2 has not been explored.
Experimental Approach
We investigated the effects of the EBI2 endogenous agonist 7α,25-OHC on G protein-dependent and -independent pathways as well as sodium ion allosterism using site-directed mutagenesis and functional studies. Moreover, we generated a homology model of EBI2 to investigate the structural basis of the allosteric modulation by sodium.
Key Results
We show that residue N114, located in the middle of TM-III at position III:11/3.35, functions as an efficacy switch. Thus, substituting N114 with an alanine (N114A) completely abolishes Gαi activation by 7α,25-OHC even though the specific binding of the [3H]-7,25-OHC radioligand increases. In contrast, the N114A mutant is still able to recruit β-arrestin and even with enhanced the potency (16-fold) compared to EBI2 wt. Underscoring the key role of N114, we also show that sodium has an negative allosteric effect on oxysterol binding and that this is mediated via N114. This is further supported by molecular modelling of the ion binding site based on a EBI2 homology model.
Conclusions and Implications
Collectively, our data points to N114 as a key residue for EBI2 signaling controlling the balance between G protein-dependent and -independent pathways and facilitating sodium binding.

Item Type:	Article
Keywords:	EBI2; GPR183; oxysterol; GPCR; G protein-coupled receptor, allosteric modulation
Date Deposited:	13 Jun 2017 00:45
Last Modified:	13 Jun 2017 00:45
URI:	https://oak.novartis.com/id/eprint/29722