SELECTIVE INTERFERENCE OF BETA-ARRESTIN-1 WITH KAPPA AND DELTA BUT NOT MU-OPIOID RECEPTOR G-PROTEIN COUPLING

The role of beta-arrestin 1 (beta-arr1) in regulation of responsivenes s of kappa, delta, and mu opioid receptors has been investigated in hu man embryonic kidney 293 cells cotransfected with opioid receptor and beta-arr1. Expression of human beta-arr1 attenuated kappa and delta op ioid receptor subtype-mediated inhibition of cAMP production and resul ted in a 100-fold increase of EC50 values for kappa-agonist U69593 and delta-agonist [D-Pen(2),D-Pen(5)]enkephalin and 30-40% reduction of t heir maximal responses. In contrast, coexpression of beta-arr1 with mu opioid receptor did not affect the concentration-effect relationship of mu-agonist [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]enkephalin. In parallel, kappa and delta receptor-mediated G protein activation was also remar kably attenuated by overexpression of beta-arr1, while the mu-agonist- stimulated response remained intact. These results indicate that beta- arr1 interferes receptor/G protein coupling and differentially regulat es the responsiveness of opioid receptors, Truncation of kappa and del ta opioid receptors at carboxyl termini abolished inhibition of beta-a rr1 on the responsiveness of both receptors. Furthermore, mu opioid re ceptor became sensitive to beta-arr1 regulation following replacement of its carboxyl terminus with the corresponding portion of the delta r eceptor, Removal of potential phosphorylation sites on the carboxyl te rminus of kappa opioid receptor led to reduced effect of beta-arr1 on the receptor-mediated response, These results suggest that receptor ca rboxyl terminus and its phosphorylation play an important role in the interaction of beta-arr1 and opioid receptors.