Abstract
We reported previously that the selective agonist U50,488H promoted phosphorylation of the mouse κ opioid receptor (KOPR) at residues S356, T357, T363, and S369. Here, we found that agonist (U50,488H)-dependent KOPR phosphorylation at all the residues was mediated by Gi/oα proteins and multiple protein kinases [GRK2, GRK3, GRK5, GRK6 and protein kinase C (PKC)]. In addition, PKC activation by phorbol ester induced agonist-independent KOPR phosphorylation. Compared with U50,488H, PKC activation promoted much higher S356/T357 phosphorylation, much lower T363 phosphorylation, and similar levels of S369 phosphorylation. After U50,488H treatment, GRKs, but not PKC, were involved in agonist-induced KOPR internalization. In contrast, PKC activation caused a lower level of agonist-independent KOPR internalization, compared with U50,488H. U50,488H-induced activation of extracellular signal-regulated kinase 1/2 (ERK1/2) was G protein-, but not β-arrestin-, dependent. After U50,488H treatment, GRK-mediated, but not PKC-mediated, KOPR phosphorylation followed by β-arrestin recruitment desensitized U50,488H-induced ERK1/2 response. Therefore, agonist-dependent (GRK- and PKC-mediated) and agonist-independent (PKC-promoted) KOPR phosphorylations show distinct phosphorylation patterns, leading to diverse cellular outcomes.
Footnotes
- Received February 9, 2017.
- Accepted August 10, 2017.
This research was supported by the National Institutes of Health [DA036802, AT006899, and DA013429]. No potential conflicts of interest relevant to this article are reported.
An earlier version of this paper appears in bioRχiv under the doi https://doi.org/10.1101/137570.
↵This article has supplemental material available at molpharm.aspetjournals.org.
- Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics
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