PT  - JOURNAL ARTICLE
AU  - Bo Feng
AU  - Zhihua Li
AU  - Jia Bei Wang
TI  - Protein Kinase C-Mediated Phosphorylation of the μ-Opioid Receptor and Its Effects on Receptor Signaling
AID  - 10.1124/mol.110.069096
DP  - 2011 Apr 01
TA  - Molecular Pharmacology
PG  - 768--775
VI  - 79
IP  - 4
4099  - http://molpharm.aspetjournals.org/content/79/4/768.short
4100  - http://molpharm.aspetjournals.org/content/79/4/768.full
SO  - Mol Pharmacol2011 Apr 01; 79
AB  - Phosphorylation of the μ opioid receptor (MOPr), mediated by several protein kinases, is a critical process in the regulation of MOPr signaling. Although G protein-coupled receptor kinases are known to play an essential role in the agonist-induced phosphorylation and desensitization of MOPr, evidence suggests that other protein kinases, especially protein kinase C (PKC), also participate in the regulation of MOPr signaling. In this study, we investigated the biochemical nature and downstream effects of PKC-mediated MOPr phosphorylation. We observed in vitro phosphorylation of the MOPr C terminus by purified PKC. Protein mass spectrometry and site-directed mutagenesis implicated Ser363 of MOPr as the primary substrate for PKC, and this was confirmed in Chinese hamster ovary cells stably expressing full-length MOPr using an antibody that specifically recognizes phosphorylated Ser363. Alanine mutation of Ser363 did not affect the affinity of MOPr-ligand binding and the efficiency of receptor G-protein coupling. However, the S363A mutation attenuated the desensitization of receptor G-protein coupling induced by phorbol 12-myristate. Our research thus has identified a specific PKC phosphorylation site in MOPr and demonstrated that PKC-mediated phosphorylation of MOPr induces receptor desensitization at the G protein coupling level.