title: Interaction of the mu-opioid receptor with synaptophysin influences receptor trafficking and signaling.
abstract: There is increasing evidence that the signal transduction of opioid receptors is modulated by receptor-associated proteins. In the search for proteins regulating mu-opioid receptor (MOPr) endocytosis, synaptophysin was found to bind to the rat micro-opioid receptor in yeast two-hybrid assay. Coimmunoprecipitation experiments and bioluminescence resonance energy transfer assays confirmed that the micro-opioid receptor constitutively interacts with synaptophysin in human embryonic kidney 293 cells overexpressing MOPr and synaptophysin. In this study, we show that overexpression of synaptophysin enhances the micro-opioid receptor endocytosis. One explanation for the observed effects is that synaptophysin recruits dynamin to the plasma membrane, facilitating fission of clathrin-coated vesicles. This suggestion is supported by our finding that overexpression of a synaptophysin truncation mutant, which breaks the interaction between synaptophysin and dynamin, prevents agonist-mediated micro-opioid receptor endocytosis. In addition, the synaptophysin-augmented micro-opioid receptor trafficking leads to attenuated agonist-induced receptor desensitization and faster receptor resensitization. Taken together, our findings strongly suggest that synaptophysin plays an important role in the regulation of micro-opioid receptor trafficking and signaling.
authors.affiliation: Department of Pharmacology and Toxicology, Otto-von-Guericke University, Leipziger Str. 44, 39120 Magdeburg, Germany.
authors.forename: Ying-Jian
authors.initials: YJ
authors.lastname: Liang
authors.forename: Dai-Fei
authors.initials: DF
authors.lastname: Wu
authors.forename: Li-Quan
authors.initials: LQ
authors.lastname: Yang
authors.forename: Volker
authors.initials: V
authors.lastname: Höllt
authors.forename: Thomas
authors.initials: T
authors.lastname: Koch
mesh_terms: D001483:Base Sequence; D002460:Cell Line; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D017931:DNA Primers; D015536:Down-Regulation; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D006801:Humans; D007668:Kidney; D007700:Kinetics; D008969:Molecular Sequence Data; D021381:Protein Transport; D011869:Radioligand Assay; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping; D015398:Signal Transduction; D016708:Synaptophysin / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D017450:Receptors, Opioid, mu; D011994:Recombinant Proteins; D016708:Synaptophysin; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-