title: Role for the C-terminus in agonist-induced mu opioid receptor phosphorylation and desensitization.
abstract: Determining which domains and amino acid residues of the mu opioid receptor are phosphorylated is critical for understanding the mechanism of mu opioid receptor phosphorylation. The role of the C-terminus of the receptor was investigated by examining the C-terminally truncated or point-mutated mu opioid receptors in receptor phosphorylation and desensitization. Both wild-type and mutated receptors were stably expressed in Chinese hamster ovary (CHO) cells. The receptor expression was confirmed by receptor radioligand binding and immunoblottting. After exposure to 5 microM of DAMGO, phosphorylation of the C-terminally truncated receptor and the mutant receptor T394A was reduced to 40 and 10% of that of the wild-type receptor, respectively. Mutation effects on agonist-induced desensitization were studied using adenylyl cyclase inhibition assays. The C-terminally truncated receptor and mutant receptor T394A both showed complete loss of DAMGO-induced desensitization, while the mutant T/S-7A receptor only lost part of its ability to desensitize. Taken together, these results suggest that the C-terminus of the mu opioid receptor participates in receptor phosphorylation and desensitization with threonine 394, a crucial residue for both features. DAMGO-induced mu opioid receptor phosphorylation and desensitization are associated and appear to involve both the mu opioid receptor C-terminus and other domains of the receptor.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201, USA.
authors.forename: H B
authors.initials: HB
authors.lastname: Deng
authors.forename: Y
authors.initials: Y
authors.lastname: Yu
authors.forename: Y
authors.initials: Y
authors.lastname: Pak
authors.forename: B F
authors.initials: BF
authors.lastname: O'Dowd
authors.forename: S R
authors.initials: SR
authors.lastname: George
authors.forename: C K
authors.initials: CK
authors.lastname: Surratt
authors.forename: G R
authors.initials: GR
authors.lastname: Uhl
authors.forename: J B
authors.initials: JB
authors.lastname: Wang
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D011485:Protein Binding / Q000235:genetics; D017450:Receptors, Opioid, mu / Q000737:chemistry / Q000235:genetics*; D014162:Transfection
chemical_list: D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D005576:Colforsin; D000262:Adenylyl Cyclases