Faculty Collaboration Database

Species differences and mechanism of action of A₃ adenosine receptor allosteric modulators. Purinergic Signal 2018 Mar;14(1):59-71

Date

11/25/2017

Pubmed ID

29170977

Pubmed Central ID

PMC5842153

DOI

10.1007/s11302-017-9592-1

Scopus ID

2-s2.0-85034734757 (requires institutional sign-in at Scopus site)   21 Citations

Abstract

Activity of the A₃ adenosine receptor (AR) allosteric modulators LUF6000 (2-cyclohexyl-N-(3,4-dichlorophenyl)-1H-imidazo [4,5-c]quinolin-4-amine) and LUF6096 (N-{2-[(3,4-dichlorophenyl)amino]quinolin-4-yl}cyclohexanecarbox-amide) was compared at four A₃AR species homologs used in preclinical drug development. In guanosine 5'-[γ-[³⁵S]thio]triphosphate ([³⁵S]GTPγS) binding assays with cell membranes isolated from human embryonic kidney cells stably expressing recombinant A₃ARs, both modulators substantially enhanced agonist efficacy at human, dog, and rabbit A₃ARs but provided only weak activity at mouse A₃ARs. For human, dog, and rabbit, both modulators increased the maximal efficacy of the A₃AR agonist 2-chloro-N ⁶-(3-iodobenzyl)adenosine-5'-N-methylcarboxamide as well as adenosine > 2-fold, while slightly reducing potency in human and dog. Based on results from N ⁶-(4-amino-3-[¹²⁵I]iodobenzyl)adenosine-5'-N-methylcarboxamide ([¹²⁵I]I-AB-MECA) binding assays, we hypothesize that potency reduction is explained by an allosterically induced slowing in orthosteric ligand binding kinetics that reduces the rate of formation of ligand-receptor complexes. Mutation of four amino acid residues of the human A₃AR to the murine sequence identified the extracellular loop 1 (EL1) region as being important in selectively controlling the allosteric actions of LUF6096 on [¹²⁵I]I-AB-MECA binding kinetics. Homology modeling suggested interaction between species-variable EL1 and agonist-contacting EL2. These results indicate that A₃AR allostery is species-dependent and provide mechanistic insights into this therapeutically promising class of agents.

Author List

Du L, Gao ZG, Paoletta S, Wan TC, Gizewski ET, Barbour S, van Veldhoven JPD, IJzerman AP, Jacobson KA, Auchampach JA

Authors

John A. Auchampach PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin
Tina C. Wan PhD Research Scientist II in the Pediatrics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adenosine A3 Receptor Agonists
Aminoquinolines
Animals
Dogs
Humans
Imidazoles
Mice
Molecular Docking Simulation
Rabbits
Receptor, Adenosine A3
Species Specificity