title: Big dynorphin as a putative endogenous ligand for the kappa-opioid receptor.
abstract: The diversity of peptide ligands for a particular receptor may provide a greater dynamic range of functional responses, while maintaining selectivity in receptor activation. Dynorphin A (Dyn A), and dynorphin B (Dyn B) are endogenous opioid peptides that activate the kappa-opioid receptor (KOR). Here, we characterized interactions of big dynorphin (Big Dyn), a 32-amino acid prodynorphin-derived peptide consisting of Dyn A and Dyn B, with human KOR, mu- (hMOR) and delta- (hDOR) opioid receptors and opioid receptor-like receptor 1 (hORL1) expressed in cells transfected with respective cDNA. Big Dyn and Dyn A demonstrated roughly similar affinity for binding to hKOR that was higher than that of Dyn B. Dyn A was more selective for hKOR over hMOR, hDOR and hORL1 than Big Dyn, while Dyn B demonstrated low selectivity. In contrast, Big Dyn activated G proteins through KOR with much greater potency, efficacy and selectivity than other dynorphins. There was no correlation between the rank order of the potency for the KOR-mediated activation of G proteins and the binding affinity of dynorphins for KOR. The rank of the selectivity for the activation of G proteins through hKOR and of the binding to this receptor also differed. Immunoreactive Big Dyn was detected using the combination of radioimmunoassay (RIA) and HPLC in the human nucleus accumbens, caudate nucleus, hippocampus and cerebrospinal fluid (CSF) with the ratio of Big Dyn and Dyn B being approximately 1:3. The presence in the brain implies that Big Dyn, along with other dynorphins, is processed from prodynorphin and secreted from neurons. Collectively, the high potency and efficacy and the relative abundance suggest that Big Dyn may play a role in the KOR-mediated activation of G proteins.
authors.affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, Illkirch, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Merg
authors.forename: Dominique
authors.initials: D
authors.lastname: Filliol
authors.forename: Ivan
authors.initials: I
authors.lastname: Usynin
authors.forename: Igor
authors.initials: I
authors.lastname: Bazov
authors.forename: Niklas
authors.initials: N
authors.lastname: Bark
authors.forename: Yasmin L
authors.initials: YL
authors.lastname: Hurd
authors.forename: Tatjana
authors.initials: T
authors.lastname: Yakovleva
authors.forename: Brigitte L
authors.initials: BL
authors.lastname: Kieffer
authors.forename: Georgy
authors.initials: G
authors.lastname: Bakalkin
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects / Q000502:physiology*; D002490:Central Nervous System / Q000187:drug effects / Q000378:metabolism*; D002555:Cerebrospinal Fluid / Q000378:metabolism; D004399:Dynorphins / Q000134:cerebrospinal fluid* / Q000737:chemistry / Q000235:genetics; D004723:Endorphins / Q000134:cerebrospinal fluid / Q000737:chemistry / Q000235:genetics; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D008024:Ligands; D051379:Mice; D018345:Mice, Knockout; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010146:Pain / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D011863:Radioimmunoassay; D011869:Radioligand Assay; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism; D017465:Receptors, Opioid, delta / Q000187:drug effects / Q000378:metabolism; D017473:Receptors, Opioid, kappa / Q000187:drug effects / Q000378:metabolism*; D017450:Receptors, Opioid, mu / Q000187:drug effects / Q000378:metabolism; D000094942:Nociceptin Receptor
chemical_list: D004723:Endorphins; D008024:Ligands; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D004399:Dynorphins; C036200:rimorphin; D000094942:Nociceptin Receptor