title: Functionally biased modulation of A(3) adenosine receptor agonist efficacy and potency by imidazoquinolinamine allosteric enhancers.
abstract: Allosteric modulators for the G(i)-coupled A(3) adenosine receptor (AR) are of considerable interest as therapeutic agents and as pharmacological tools to probe various signaling pathways. In this study, we initially characterized the effects of several imidazoquinolinamine allosteric modulators (LUF5999, LUF6000 and LUF6001) on the human A(3) AR stably expressed in CHO cells using a cyclic AMP functional assay. These modulators were found to affect efficacy and potency of the agonist Cl-IB-MECA differently. LUF5999 (2-cyclobutyl derivative) enhanced efficacy but decreased potency. LUF6000 (2-cyclohexyl derivative) enhanced efficacy without affecting potency. LUF6001 (2-H derivative) decreased both efficacy and potency. We further compared the agonist enhancing effects of LUF6000 in several other A(3) AR-mediated events. It was shown that although LUF6000 behaved somewhat differently in various signaling pathways, it was more effective in enhancing the effects of low-efficacy than of high-efficacy agonists. In an assay of cyclic AMP accumulation, LUF6000 enhanced the efficacy of all agonists examined, but in the membrane hyperpolarization assay, it only enhanced the efficacy of partial agonists. In calcium mobilization, LUF6000 did not affect the efficacy of the full agonist NECA but was able to switch the nucleoside antagonist MRS542 into a partial agonist. In translocation of β-arrestin2, the agonist-enhancing effect LUF6000 was not pronounced. In an assay of ERK1/2 phosphorylation LUF6000 did not show any effect on the efficacy of Cl-IB-MECA. The differential effects of LUF6000 on the efficacy and potency of the agonist Cl-IB-MECA in various signaling pathway were interpreted quantitatively using a mathematical model.
authors: Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0810, USA. zg21o@nih.gov
authors: Zhan-Guo
authors: ZG
authors: Gao
authors: Dennis
authors: D
authors: Verzijl
authors: Annelien
authors: A
authors: Zweemer
authors: Kai
authors: K
authors: Ye
authors: Anikó
authors: A
authors: Göblyös
authors: Adriaan P
authors: AP
authors: Ijzerman
authors: Kenneth A
authors: KA
authors: Jacobson
mesh_terms: D058909:Adenosine A3 Receptor Agonists / Q000737:chemistry / Q000494:pharmacology*; D000494:Allosteric Regulation / Q000187:drug effects; D000634:Aminoquinolines / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D019390:Arrestins / Q000378:metabolism; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D003198:Computer Simulation; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000378:metabolism; D003627:Data Interpretation, Statistical; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007093:Imidazoles / Q000737:chemistry / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D015394:Molecular Structure; D043684:Receptor, Adenosine A3 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D000071557:beta-Arrestins
chemical_list: D058909:Adenosine A3 Receptor Agonists; D000634:Aminoquinolines; D019390:Arrestins; D007093:Imidazoles; D043684:Receptor, Adenosine A3; D000071557:beta-Arrestins; D000242:Cyclic AMP; D002118:Calcium