Arrestin-dependent but G-protein coupled receptor kinase-independent uncoupling of D2-dopamine receptors

摘要

We reconstituted D2 like dopamine receptor (D2R) and the delta opioid receptor (DOR) coupling to G-protein gated inwardly rectifying potassium channels (Kir3) and directly compared the effects of co-expression of G-protein coupled receptor kinase (GRK) and arrestin on agonist-dependent desensitization of the receptor response. We found, as described previously, that co-expression of a GRK and an arrestin synergistically increased the rate of agonist-dependent desensitization of DOR. In contrast, only arrestin expression was required to produce desensitization of D2R responses. Furthermore, arrestin-dependent GRK-independent desensitization of D2R-K ir3 coupling could be transferred to DOR by substituting the third cytoplasmic loop of DOR with that of D2R. The arrestin-dependent GRK-independent desensitization of D2R desensitization was inhibited by staurosporine treatment, and blocked by alanine substitution of putative protein kinase C phosphorylation sites in the third cytoplasmic loop of D2R. Finally, the D2R construct in which putative protein kinase C phosphorylation sites were mutated did not undergo significant agonist-dependent desensitization even after GRK co-expression, suggesting that GRK phosphorylation of D2R does not play an important role in uncoupling of the receptor. The classical model for the uncoupling and desensitization of G-protein coupled receptors (GPCRs) involves the phosphorylation of the agonist-bound receptor by G protein coupled receptor kinases (GRK), followed by the binding of arrestin to the GRK phosphorylated agonist-activated receptor. We reconstituted D2-dopamine receptor (D2R) signaling in Xenopus oocytes to show that arrestin-mediated uncoupling of D2R from associated G proteins (Gαβγ) occurs independently of GRKs. The classical model for the uncoupling and desensitization of G-protein coupled receptors (GPCRs) involves the phosphorylation of the agonist-bound receptor by G protein coupled receptor kinases (GRK), followed by the binding of arrestin to the GRK phosphorylated agonist-activated receptor. We reconstituted D2-dopamine receptor (D2R) signaling in Xenopus oocytes to show that arrestin-mediated uncoupling of D2R from associated G proteins (Gαβγ) occurs independently of GRKs.