title: Morphine regulates expression of μ-opioid receptor MOR-1A, an intron-retention carboxyl terminal splice variant of the μ-opioid receptor (OPRM1) gene via miR-103/miR-107.
abstract: The μ-opioid receptor (MOR-1) gene OPRM1 undergoes extensive alternative splicing, generating an array of splice variants. Of these variants, MOR-1A, an intron-retention carboxyl terminal splice variant identical to MOR-1 except for the terminal intracellular tail encoded by exon 3b, is quite abundant and conserved from rodent to humans. Increasing evidence indicates that miroRNAs (miRNAs) regulate MOR-1 expression and that μ agonists such as morphine modulate miRNA expression. However, little is known about miRNA regulation of the OPRM1 splice variants. Using 3'-rapid amplification cDNA end and Northern blot analyses, we identified the complete 3'-untranslated region (3'-UTR) for both mouse and human MOR-1A and their conserved polyadenylation site, and defined the role the 3'-UTR in mRNA stability using a luciferase reporter assay. Computer models predicted a conserved miR-103/107 targeting site in the 3'-UTR of both mouse and human MOR-1A. The functional relevance of miR-103/107 in regulating expression of MOR-1A protein through the consensus miR-103/107 binding sites in the 3'-UTR was established by using mutagenesis and a miR-107 inhibitor in transfected human embryonic kidney 293 cells and Be(2)C cells that endogenously express human MOR-1A. Chronic morphine treatment significantly upregulated miR-103 and miR-107 levels, leading to downregulation of polyribosome-associated MOR-1A in both Be(2)C cells and the striatum of a morphine-tolerant mouse, providing a new perspective on understanding the roles of miRNAs and OPRM1 splice variants in modulating the complex actions of morphine in animals and humans.
authors.affiliation: Department of Neurology and the Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, New York.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Lu
authors.forename: Jin
authors.initials: J
authors.lastname: Xu
authors.forename: Mingming
authors.initials: M
authors.lastname: Xu
authors.forename: Gavril W
authors.initials: GW
authors.lastname: Pasternak
authors.forename: Ying-Xian
authors.initials: YX
authors.lastname: Pan
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D003342:Corpus Striatum / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D057809:HEK293 Cells; D006801:Humans; D007438:Introns; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000502:physiology*; D009020:Morphine / Q000494:pharmacology*; D017450:Receptors, Opioid, mu / Q000235:genetics*
chemical_list: D020413:3' Untranslated Regions; C544749:MIRN103 microRNA, human; C555364:MIRN103 microRNA, mouse; C549045:MIRN107 microRNA, human; C555365:MIRN107 microRNA, mouse; D035683:MicroRNAs; C485764:OPRM1 protein, human; C404943:Oprm protein, mouse; D017450:Receptors, Opioid, mu; D009020:Morphine