Gating function of isoleucine‐116 in TM‐3 (position III:16/3.40) for the activity state of the CC‐chemokine receptor 5 (CCR5). (March 2014)

• Record Type: Journal Article
• Authors: Steen, A; Sparre‐Ulrich, A H; Thiele, S; Guo, D; Frimurer, T M; Rosenkilde, M M
• Is Part Of: British journal of pharmacology. Volume 171:Number 6(2014:Mar.)
• Page Start: 1566
• Page End: 1579
• Publication Date: 2014-03
• Subjects: Pharmacology -- Periodicals; Chemotherapy -- Periodicals; Drug Therapy -- Periodicals; Pharmacology -- Periodicals; 615.1
• DOI: 10.1111/bph.12553
• Languages: English
• ISSNs: 0007-1188

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="bph12553-sec-0001" sec-type="section"> <title>Background and Purpose</title> <p>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 7TM receptors. However, in 37% of chemokine receptors – a subgroup of 7TM 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 CCR5 activity.</p> </sec> <sec id="bph12553-sec-0002" sec-type="section"> <title>Experimental Approach</title> <p>The effects of [L203F]‐CCR5 in TM‐5 (position V:13/5.47), [I116A]‐CCR5 in TM‐3 (III:16/3.40) and [L203F;G286F]‐CCR5 (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.</p> </sec> <sec id="bph12553-sec-0003" sec-type="section"> <title>Key Results</title> <p>[L203F]‐CCR5 increased the basal level of G‐protein coupling (20–70% of E<sub>max</sub>) and β‐arrestin recruitment (50% of E<sub>max</sub>) with a threefold increase in agonist potency. <italic>In silico</italic>, [I116A]‐CCR5 switched χ1‐angle in [L203F]‐CCR5. Furthermore, [I116A]‐CCR5 was constitutively active to a similar degree as [L203F]‐CCR5. Tyr<sup>244</sup> in TM‐6 (VI:09/6.44) moved towards TM‐5 <italic>in silico</italic>, consistent with its previously shown function for CCR5 activation. On [L203F;G286F]‐CCR5 the antagonist aplaviroc was converted to a superagonist.</p> </sec> <sec id="bph12553-sec-0004" sec-type="section"> <title>Conclusions and Implications</title> <p>The results imply that an aromatic amino acid in the centre of TM‐5 controls the level of receptor activity. Furthermore, Ile<sup>116</sup> acts as a gate for the movement of Tyr<sup>244</sup> towards TM‐5 in the active state, a mechanism proposed previously for the β<sub>2</sub>‐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.</p> </sec> </abstract>