Reversed binding of a small molecule ligand in homologous chemokine receptors - differential role of extracellular loop 2

TY - JOUR

T1 - Reversed binding of a small molecule ligand in homologous chemokine receptors - differential role of extracellular loop 2

AU - Jensen, P C

AU - Thiele, S

AU - Steen, A

AU - Elder, A

AU - Kolbeck, R

AU - Ghosh, Sudip

AU - Frimurer, T M

AU - Rosenkilde, Mette Marie

N1 - © 2011 The Authors. British Journal of Pharmacology © 2011 The British Pharmacological Society.

PY - 2012/5

Y1 - 2012/5

N2 - Background and Purpose The majority of small molecule compounds targeting chemokine receptors share a similar pharmacophore with a centrally located aliphatic positive charge and flanking aromatic moieties. Here we describe a novel piperidine-based compound with structural similarity to previously described CCR8-specific agonists, but containing a unique phenyl-tetrazol moiety which, in addition to activity at CCR8 was also active at CCR1. Experimental Approach Single point mutations were introduced in CCR1 and CCR8, and their effect on small molecule ligand-induced receptor activation was examined through inositol trisphosphate (IP 3) accumulation. The molecular interaction profile of the agonist was verified by molecular modeling. Key Results The chemokine receptor conserved glutamic acid in TM-VII served as a common anchor for the positively charged amine in the piperidine ring. However, whereas the phenyl-tetrazol group interacted with TyrIV:24 (Tyr 172) and TyrIII:09 (Tyr 114) in the major binding pocket (delimited by TM-III to VII) of CCR8, it also interacted with TrpII:20 (Trp 90) and LysII:24 (Lys 94) in the minor counterpart (delimited TM-I to III, plus TM-VII) in CCR1. A straightening of TM-II by Ala-substitution of ProII:18 confirmed its unique role in CCR1. The extracellular loop 2 (ECL-2) contributed directly to the small molecule binding site in CCR1, whereas it contributed to efficacy, but not potency in CCR8. Conclusion and Implications Despite high ligand potency and efficacy and receptor similarity, this dual-active and bitopic compound binds oppositely in CCR1 and CCR8 with different roles of ECL-2, thereby expanding and diversifying the influence of extracellular receptor regions in drug action.

AB - Background and Purpose The majority of small molecule compounds targeting chemokine receptors share a similar pharmacophore with a centrally located aliphatic positive charge and flanking aromatic moieties. Here we describe a novel piperidine-based compound with structural similarity to previously described CCR8-specific agonists, but containing a unique phenyl-tetrazol moiety which, in addition to activity at CCR8 was also active at CCR1. Experimental Approach Single point mutations were introduced in CCR1 and CCR8, and their effect on small molecule ligand-induced receptor activation was examined through inositol trisphosphate (IP 3) accumulation. The molecular interaction profile of the agonist was verified by molecular modeling. Key Results The chemokine receptor conserved glutamic acid in TM-VII served as a common anchor for the positively charged amine in the piperidine ring. However, whereas the phenyl-tetrazol group interacted with TyrIV:24 (Tyr 172) and TyrIII:09 (Tyr 114) in the major binding pocket (delimited by TM-III to VII) of CCR8, it also interacted with TrpII:20 (Trp 90) and LysII:24 (Lys 94) in the minor counterpart (delimited TM-I to III, plus TM-VII) in CCR1. A straightening of TM-II by Ala-substitution of ProII:18 confirmed its unique role in CCR1. The extracellular loop 2 (ECL-2) contributed directly to the small molecule binding site in CCR1, whereas it contributed to efficacy, but not potency in CCR8. Conclusion and Implications Despite high ligand potency and efficacy and receptor similarity, this dual-active and bitopic compound binds oppositely in CCR1 and CCR8 with different roles of ECL-2, thereby expanding and diversifying the influence of extracellular receptor regions in drug action.

KW - Animals

KW - Binding Sites

KW - COS Cells

KW - Cercopithecus aethiops

KW - Glutamic Acid

KW - Humans

KW - Inositol 1,4,5-Trisphosphate

KW - Ligands

KW - Models, Molecular

KW - Piperidines

KW - Point Mutation

KW - Receptors, CCR1

KW - Receptors, CCR8

KW - Tetrazoles

U2 - 10.1111/j.1476-5381.2011.01771.x

DO - 10.1111/j.1476-5381.2011.01771.x

M3 - Journal article

C2 - 22050085

SN - 0007-1188

VL - 166

SP - 258

EP - 275

JO - British Journal of Pharmacology

JF - British Journal of Pharmacology

IS - 1

ER -