Determination of sites of U50,488H-promoted phosphorylation of the mouse κ opioid receptor (KOPR): disconnect between KOPR phosphorylation and internalization.
Biochem J
; 473(4): 497-508, 2016 Feb 15.
Article
em En
| MEDLINE
| ID: mdl-26635353
ABSTRACT
Phosphorylation sites of KOPR (κ opioid receptor) following treatment with the selective agonist U50,488H {(-)(trans)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidiny)cyclo-hexyl]benzeneacetamide} were identified after affinity purification, SDS/PAGE, in-gel digestion with Glu-C and HPLC-MS/MS. Single- and double-phosphorylated peptides were identified containing phosphorylated Ser(356), Thr(357), Thr(363) and Ser(369) in the C-terminal domain. Antibodies were generated against three phosphopeptides containing pSer(356)/pThr(357), pThr(363) and pSer(369) respectively, and affinity-purified antibodies were found to be highly specific for phospho-KOPR. U50,488H markedly enhanced staining of the KOPR by pThr(363)-, pSer(369)- and pSer(356)/pThr(357)-specific antibodies in immunoblotting, which was blocked by the selective KOPR antagonist norbinaltorphimine. Ser(369) phosphorylation affected Thr(363) phosphorylation and vice versa, and Thr(363) or Ser(369) phosphorylation was important for Ser(356)/Thr(357) phosphorylation, revealing a phosphorylation hierarchy. U50,488H, but not etorphine, promoted robust KOPR internalization, although both were full agonists. U50,488H induced higher degrees of phosphorylation than etorphine at Ser(356)/Thr(357), Thr(363) and Ser(369) as determined by immunoblotting. Using SILAC (stable isotope labelling by amino acids in cell culture) and HPLC-MS/MS, we found that, compared with control (C), U50,488H (U) and etorphine (E) KOPR promoted single phosphorylation primarily at Thr(363) and Ser(369) with U/E ratios of 2.5 and 2 respectively. Both induced double phosphorylation at Thr(363)+Ser(369) and Thr(357)+Ser(369) with U/E ratios of 3.3 and 3.4 respectively. Only U50,488H induced triple phosphorylation at Ser(356)+Thr(357)+Ser(369). An unphosphorylated KOPR-(354-372) fragment containing all of the phosphorylation sites was detected with a C/E/U ratio of 1/0.7/0.4, indicating that â¼60% and â¼30% of the mouse KOPR are phosphorylated following U50,488H and etorphine respectively. Thus KOPR internalization requires receptor phosphorylation above a certain threshold, and higher-order KOPR phosphorylation may be disproportionally important.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Receptores Opioides kappa
/
Analgésicos não Narcóticos
/
(trans)-Isômero de 3,4-dicloro-N-metil-N-(2-(1-pirrolidinil)-ciclo-hexil)-benzenoacetamida
/
Endocitose
Limite:
Animals
Idioma:
En
Ano de publicação:
2016
Tipo de documento:
Article