Identification of three new alternatively spliced variants of the rat mu opioid receptor gene: Dissociation of affinity and efficacy Journal Article


Authors: Pasternak, D. A.; Pan, L.; Xu, J.; Yu, R.; Xu, M. M.; Pasternak, G. W.; Pan, Y. X.
Article Title: Identification of three new alternatively spliced variants of the rat mu opioid receptor gene: Dissociation of affinity and efficacy
Abstract: Mu opioid receptors mediate the pharmacological actions of morphine and morphine-like drugs, such as heroin. The mouse and human Oprm genes undergo splicing. In these present studies, we have identified and characterized three new MOR-1 splice variants from the rat Oprm gene. Using an RT-PCR approach, we isolated the new exons 7, 8 and 9 downstream of exon 3. The rat exons 7 and 9 were homologous to the mouse exons 7 and 9 while the rat exon 8 was not. Northern blot analysis with the new exon probes showed distinctive and abundant transcripts of the variants in the rat brain. Full-length cDNA clones containing the new exons, rMOR-1C1, rMOR-1C2 and rMOR-1D were obtained using an RT-PCR approach. Each contained the same exons 1, 2 and 3 as the original rMOR-1, followed by different combinations of the new exons in place of exon 4. In addition, we also isolated another new variant, rMOR-1A, which contains only exons 1, 2 and 3, and is homologous to the human variant MOR-1A previously identified. All the variants were highly mu-selective in binding studies with little difference in affinities for the mu ligands among the variants. However, functional evaluation of assessments of the variants using agonist stimulated [35S]GTPγS binding assays revealed marked differences among the variants, both in terms of potency and efficacy of the drugs. The relative efficacy of a series of mu opioids to each other varied depending upon the variant studied. Efficacy in the [35S]GTPγS assay did not correlate with either receptor binding affinity or with potency. Thus, selectivity of opioid action might be achieved by designing compounds with varying efficacies at different MOR-1 variants.
Keywords: exon; exons; drug efficacy; nonhuman; animal cell; animals; animal tissue; reverse transcription polymerase chain reaction; drug potency; animalia; molecular cloning; cloning, molecular; brain; reverse transcriptase polymerase chain reaction; nucleotide sequence; substrate specificity; rat; alternative splicing; alternative rna splicing; rats; receptor affinity; morphine; sequence homology; blotting, northern; protein variant; mu opiate receptor; receptor gene; receptors, opioid, mu; receptor binding; complementary dna; northern blotting; gene transfer techniques; opioid receptor; cho cells; cricetinae; binding, competitive; guanosine 5'-o-(3-thiotriphosphate); binding assay; mor-1; narcotics; guanosine 5' o (3 thiotriphosphate); mop; priority journal; article; gtpgammas
Journal Title: Journal of Neurochemistry
Volume: 91
Issue: 4
ISSN: 0022-3042
Publisher: Wiley Blackwell  
Date Published: 2004-11-01
Start Page: 881
End Page: 890
Language: English
DOI: 10.1111/j.1471-4159.2004.02767.x
PROVIDER: scopus
PUBMED: 15525342
DOI/URL:
Notes: J. Neurochem. -- Cited By (since 1996):44 -- Export Date: 16 June 2014 -- CODEN: JONRA -- Molecular Sequence Numbers: GENBANK: AY225402, AY225403, AY309000, AY309002; -- Source: Scopus
Altmetric
Citation Impact
BMJ Impact Analytics
MSK Authors
  1. Yingxian Pan
    132 Pan
  2. Gavril W Pasternak
    414 Pasternak
  3. Ming Ming Xu
    34 Xu
  4. Rui Yu
    2 Yu
  5. Ling   Pan
    5 Pan
  6. Jin   Xu
    60 Xu