%0 Journal Article
%T Functional modulation of human delta opioid receptor by neuropeptide FF
%A Minna-Liisa £¿nk£¿
%A Pertti Panula
%J BMC Neuroscience
%D 2005
%I BioMed Central
%R 10.1186/1471-2202-6-21
%X We used a stable Chinese hamster ovary cell line expressing c-MYC-tagged human delta opioid receptor to study the interactions at the molecular level. Our results imply that NPFF can directly modulate the activation of delta opioid receptor in the absence of NPFF receptors. The modulatory effect, though only moderate, was consistently detected with several methods. The agonist-induced receptor trafficking was changed in the presence of (1DMe)NPYF, a stable NPFF-analogue. (1DMe)NPYF enhanced the receptor activation and recovery; opioid antagonists inhibited the effects, indicating that they were delta opioid receptor-mediated. The binding experiments with a novel ligand, Terbium-labeled deltorphin I, showed that (1DMe)NPYF modulated the binding of delta opioid receptor ligands. The levels of phosphorylated mitogen-activated protein kinase and intracellular cAMP were studied to clarify the effects of NPFF on the opioid signaling mechanisms. Application of (1DMe)NPYF together with a delta opioid receptor agonist enhanced the signaling via both pathways studied. Concomitantly to the receptor trafficking, the time-course of the activation of the signaling was altered.In addition to working via indirect mechanisms on the opioid systems, NPFF may exert a direct modulatory effect on the delta opioid receptor. NPFF may be a multi-functional neuropeptide that regulates several neuronal systems depending on the site of action.Neuropeptide FF (NPFF) belongs to a family of RFamide peptides and was originally isolated from bovine brain [1-3]. It has a wide range of functions, including effects on pain mechanisms [1,4], opioid tolerance [5], cardiovascular regulation [6] and neuroendocrinological function [7].At the physiological level NPFF seems to have both a direct analgesic effect and a modulatory effect on the opioid system. Some of the effects may be mediated via the NPFF receptors as two such receptors, NPFF1R and NPFF2R, have been identified [17-19]. Both NPFF1R and NPFF2R
%U http://www.biomedcentral.com/1471-2202/6/21