title: Differential use of an in-frame translation initiation codon regulates human mu opioid receptor (OPRM1).
abstract: The pharmacological effects of morphine and morphine-like drugs are mediated primarily through the micro opioid receptor. Here we show that differential use of an in-frame translational start codon in the 5'-untranslated region of the OPRM1 generates different translational products in vivo and in vitro. The 5'-end of the OPRM1 gene is necessary for initiating the alternate form and for subsequent degradation of the protein. Initiation of OPRM1 at the upstream site decreases the initiation at the main AUG site. However, alternative initiation of the long form of OPRM1 produces a protein with a short half-life, resulting from degradation mediated by the ubiquitin-proteasome pathway. Reporter and degradation assays showed that mutations of this long form at the second and third lysines reduce ubiquitin-dependent proteasome degradation, stabilizing the protein. The data suggest that MOP expression is controlled in part by initiation of the long form of MOP at the alternate site.
authors.affiliation: Department of Pharmacology, University of Minnesota Medical School, Minneapolis, MN 55455, USA. songx047@umn.edu
authors.forename: Kyu Young
authors.initials: KY
authors.lastname: Song
authors.forename: Hack Sun
authors.initials: HS
authors.lastname: Choi
authors.forename: Cheol Kyu
authors.initials: CK
authors.lastname: Hwang
authors.forename: Chun Sung
authors.initials: CS
authors.lastname: Kim
authors.forename: Ping-Yee
authors.initials: PY
authors.lastname: Law
authors.forename: Li-Na
authors.initials: LN
authors.lastname: Wei
authors.forename: Horace H
authors.initials: HH
authors.lastname: Loh
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D018387:Codon, Initiator; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010442:Peptide Chain Initiation, Translational / Q000235:genetics*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D014176:Protein Biosynthesis; D020033:Protein Isoforms / Q000235:genetics* / Q000378:metabolism; D012315:RNA Caps / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000235:genetics* / Q000378:metabolism
chemical_list: D020121:5' Untranslated Regions; D018387:Codon, Initiator; C485764:OPRM1 protein, human; D020033:Protein Isoforms; D012315:RNA Caps; D012333:RNA, Messenger; D017450:Receptors, Opioid, mu; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease