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Gating function of isoleucine‐116 in TM ‐3 (position III :16/3.40) for the activity state of the CC ‐chemokine receptor 5 ( CCR 5)
Author(s) -
Steen A,
SparreUlrich A H,
Thiele S,
Guo D,
Frimurer T M,
Rosenkilde M M
Publication year - 2014
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.12553
Subject(s) - g protein coupled receptor , amino acid , receptor , agonist , g protein , stereochemistry , transmembrane domain , chemistry , leucine , biology , biochemistry
Background and Purpose A conserved amino acid within a protein family indicates a significance of the residue. In the centre of transmembrane helix ( TM )‐5, position V :13/5.47, an aromatic amino acid is conserved among class A 7 TM receptors. However, in 37% of chemokine receptors – a subgroup of 7 TM receptors – it is a leucine indicating an altered function. Here, we describe the significance of this position and its possible interaction with TM ‐3 for CCR 5 activity. Experimental Approach The effects of [ L 203 F ]‐ CCR 5 in TM ‐5 (position V :13/5.47), [ I 116 A ]‐ CCR 5 in TM ‐3 ( III :16/3.40) and [ L 203 F ; G 286 F ]‐ CCR 5 ( V :13/5.47; VII :09/7.42) were determined in G ‐protein‐ and β‐arrestin‐coupled signalling. Computational modelling monitored changes in amino acid conformation. Key Results [ L 203 F ]‐ CCR 5 increased the basal level of G ‐protein coupling (20–70% of E max ) and β‐arrestin recruitment (50% of E max ) with a threefold increase in agonist potency. In silico , [ I 116 A ]‐ CCR 5 switched χ1‐angle in [ L 203 F ]‐ CCR 5. Furthermore, [ I 116 A ]‐ CCR 5 was constitutively active to a similar degree as [ L 203 F ]‐ CCR 5. Tyr 244 in TM ‐6 ( VI :09/6.44) moved towards TM ‐5 in silico , consistent with its previously shown function for CCR 5 activation. On [ L 203 F ; G 286 F ]‐ CCR 5 the antagonist aplaviroc was converted to a superagonist. Conclusions and Implications The results imply that an aromatic amino acid in the centre of TM ‐5 controls the level of receptor activity. Furthermore, I le 116 acts as a gate for the movement of T yr 244 towards TM ‐5 in the active state, a mechanism proposed previously for the β 2 ‐adrenoceptor. The results provide an understanding of chemokine receptor function and thereby information for the development of biased and non‐biased antagonists and inverse agonists.