title: Tetrapeptide Endomorphin Analogs Require Both Full Length and Truncated Splice Variants of the Mu Opioid Receptor Gene Oprm1 for Analgesia.
abstract: The mu opioid receptor gene undergoes extensive alternative splicing. Mu opioids can be divided into three classes based on the role of different groups of splice variants. Morphine and methadone require only full length seven transmembrane (7TM) variants for analgesia, whereas IBNtxA (3'-iodobenzyol-6β-naltrexamide) needs only truncated 6TM variants. A set of endomorphin analogs fall into a third group that requires both 6TM and 7TM splice variants. Unlike morphine, endomorphin 1 and 2, DAPP (Dmt,d-Ala-Phe-Phe-NH2), and IDAPP (3'-iodo-Dmt-d-Ala-Phe-Phe-NH2) analgesia was lost in an exon 11 knockout mouse lacking 6TM variants. Restoring 6TM variant expression in a knockout mouse lacking both 6TM and 7TM variants failed to rescue DAPP or IDAPP analgesia. However, re-establishing 6TM expression in an exon 11 knockout mouse that still expressed 7TM variants did rescue the response, consistent with the need for both 6TM and 7TM variants. In receptor binding assays,125I-IDAPP labeled more sites (Bmax) than3H-DAMGO ([d-Ala2,N-MePhe4,Gly(ol)5]-enkephalin) in wild-type mice. In exon 11 knockout mice,125I-IDAPP binding was lowered to levels similar to3H-DAMGO, which remained relatively unchanged compared to wild-type mice.125I-IDAPP binding was totally lost in an exon 1/exon 11 knockout model lacking all Oprm1 variant expression, confirming that the drug was not cross labeling non-mu opioid receptors. These findings suggested that125I-IDAPP labeled two populations of mu binding sites in wild-type mice, one corresponding to 7TM variants and the second dependent upon 6TM variants. Together, these data indicate that endomorphin analogs represent a unique, genetically defined, and distinct class of mu opioid analgesic.
authors.affiliation: Department of Neurology and Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.|Neuroscience and Pharmacology Graduate Program, Weill Cornell Graduate School of Medical Sciences , New York, New York 10065, United States.
authors.forename: Gina F
authors.initials: GF
authors.lastname: Marrone
authors.affiliation: Department of Neurology and Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Lu
authors.affiliation: Long Island University , Post Campus, Brookville, New York 11548, United States.
authors.forename: Grace
authors.initials: G
authors.lastname: Rossi
authors.affiliation: Department of Neurology and Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.|Neuroscience and Pharmacology Graduate Program, Weill Cornell Graduate School of Medical Sciences , New York, New York 10065, United States.
authors.forename: Ankita
authors.initials: A
authors.lastname: Narayan
authors.affiliation: Department of Neurology and Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.
authors.forename: Amanda
authors.initials: A
authors.lastname: Hunkele
authors.affiliation: Department of Neurology and Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.
authors.forename: Sarah
authors.initials: S
authors.lastname: Marx
authors.affiliation: Department of Neurology and Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.
authors.forename: Jin
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Neuroscience and Cell Biology, UMDNJ-Robert Wood Johnson Medical School , Piscataway, New Jersey 08854, United States.
authors.forename: John
authors.initials: J
authors.lastname: Pintar
authors.affiliation: Department of Neurology and Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.
authors.forename: Susruta
authors.initials: S
authors.lastname: Majumdar
authors.affiliation: Department of Neurology and Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.
authors.forename: Ying-Xian
authors.initials: YX
authors.lastname: Pan
authors.affiliation: Department of Neurology and Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center , New York, New York 10065, United States.|Neuroscience and Pharmacology Graduate Program, Weill Cornell Graduate School of Medical Sciences , New York, New York 10065, United States.
authors.forename: Gavril W
authors.initials: GW
authors.lastname: Pasternak
mesh_terms: D017398:Alternative Splicing; D000698:Analgesia; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002460:Cell Line; D005091:Exons; D005822:Genetic Vectors; D006358:Hot Temperature; D016086:Lentivirus; D008297:Male; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009842:Oligopeptides / Q000494:pharmacology*; D010146:Pain / Q000188:drug therapy / Q000378:metabolism; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism*; D000071560:beta-Arrestin 2 / Q000378:metabolism
chemical_list: D000701:Analgesics, Opioid; C000605258:Arrb2 protein, mouse; D009842:Oligopeptides; C404943:Oprm protein, mouse; D020033:Protein Isoforms; D012333:RNA, Messenger; D017450:Receptors, Opioid, mu; D000071560:beta-Arrestin 2
keywords: G-Protein coupled receptor; Mu opioid receptor; alternative splicing; analgesia; endorphin; morphine