title: ADP-ribosylation factor 6 regulates mu-opioid receptor trafficking and signaling via activation of phospholipase D2.
abstract: Endocytosis of the mu-opioid receptor (MOPr) has been shown to play a protective role against the development of tolerance to opioid drugs by facilitating receptor reactivation and recycling. It has been further demonstrated, that the opioid-mediated and ADP-ribosylation factor (ARF)-dependent activation of phospholipase D2 (PLD2) is a prerequisite for MOPr endocytosis. In this study, we investigated which particular ARF protein is involved in opioid-mediated PLD2 activation and what are the mechanisms of ARF function in MOPr trafficking and signaling. By coexpressing the MOPr and dominant negative or constitutively active ARF mutants in human embryonic kidney (HEK) 293 cells and primary cultured cortical neurons as well as by using siRNA technology, we identified the ARF6 protein to be involved in the regulation of MOPr endocytosis. We also found that expression of an effector domain mutant of ARF6, which is incapable of activating PLD, blocked agonist-induced endocytosis suggesting that ARF6 function in MOPr trafficking is PLD2-mediated. Analogously, opioid-mediated activation of PLD2 is blocked in the presence of dominant negative ARF6 mutants. Finally, we also showed that ARF6 protein influences the recycling/reactivation of internalized MOPr and thus modulates agonist-induced MOPr desensitization. Together, these results provide evidence that ARF6 protein regulates MOPr trafficking and signaling via PLD2 activation and hence affects the development of opioid receptor desensitization and tolerance.
authors: Department of Pharmacology and Toxicology, Otto-von-Guericke University, Leipziger Strasse 44, 39120 Magdeburg, Germany.
authors: Marija
authors: M
authors: Rankovic
authors: Lea
authors: L
authors: Jacob
authors: Vladan
authors: V
authors: Rankovic
authors: Lars-Ove
authors: LO
authors: Brandenburg
authors: Helmut
authors: H
authors: Schröder
authors: Volker
authors: V
authors: Höllt
authors: Thomas
authors: T
authors: Koch
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D004705:Endocytosis / Q000187:drug effects; D005786:Gene Expression Regulation; D006801:Humans; D009020:Morphine / Q000494:pharmacology; D009154:Mutation; D009294:Narcotics / Q000494:pharmacology; D009474:Neurons / Q000166:cytology; D010739:Phospholipase D / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D000089982:ADP-Ribosylation Factor 6; D009294:Narcotics; C485765:Oprm1 protein, rat; D017450:Receptors, Opioid, mu; D009020:Morphine; C105606:phospholipase D2; D010739:Phospholipase D; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715349:Arf6 protein, rat