@article{APS6720,
author = {Yun Cheng and Yi-min Tao and Jian-feng Sun and Yu-hua Wang and Xue-jun Xu and Jie Chen and Zhi-qiang Chi and Jing-gen Liu},
title = {Adenosine A1 receptor agonist N6-cyclohexyl-adenosine induced phosphorylation of delta opioid receptor and desensitization of its signaling},
journal = {Acta Pharmacologica Sinica},
volume = {31},
number = {7},
year = {2016},
keywords = {},
abstract = {Aim: To define the effect of adenosine A1 receptor (A1R) on delta opioid receptor (DOR)-mediated signal transduction.
Methods: CHO cells stably expressing HA-tagged A1R and DOR-CFP fusion protein were used. The localization of receptors was observed using confocal microscope. DOR-mediated inhibition of adenylyl cyclase was measured using cyclic AMP assay. Western blots were employed to detect the phosphorylation of Akt and the DOR. The effect of A1R agonist N6-cyclohexyladenosine (CHA) on DOR down-regulation was assessed using radioligand binding assay.
Results: CHA 1 μmol/L time-dependently attenuated DOR agonist [D-Pen2,5]enkephalin (DPDPE)-induced inhibition of intracellular cAMP accumulation with a t1/2=2.56 (2.09–3.31) h. Pretreatment with 1 μmol/L CHA for 24 h caused a right shift of the dose-response curve of DPDPE-mediated inhibition of cAMP accumulation, with a significant increase in EC50 but no change in Emax. Pretreatment with 1 μmol/L CHA for 1 h also induced a significant attenuation of DPDPE-stimulated phosphorylation of Akt. Moreover, CHA time-dependently phosphorylated DOR (Ser363), and this effect was inhibited by A1R antagonist 1,3-Dipropyl-8-cyclopentylxanthine (DPCPX) but not by DOR antagonist naloxone. However, CHA failed to produce the down-regulation of DOR, as neither receptor affinity (Kd) nor receptor density (Bmax) of DOR showed significant change after chronic CHA exposure.
Conclusion: Activation of A1R by its agonist caused heterologous desensitization of DOR-mediated inhibition of intracellular cAMP accumulation and phosphorylation of Akt. Activation of A1R by its agonist also induced heterologous phosphorylation but not down-regulation of DOR.},
issn = {1745-7254}, url = {http://www.chinaphar.com/article/view/6720}
}