title: In vivo visualization of delta opioid receptors upon physiological activation uncovers a distinct internalization profile.
abstract: G-protein-coupled receptors (GPCRs) mediate numerous physiological functions and represent prime therapeutic targets. Receptor trafficking upon agonist stimulation is critical for GPCR function, but examining this process in vivo remains a true challenge. Using knock-in mice expressing functional fluorescent delta opioid receptors under the control of the endogenous promoter, we visualized in vivo internalization of this native GPCR upon physiological stimulation. We developed a paradigm in which animals were made dependent on morphine in a drug-paired context. When re-exposed to this context in a drug-free state, mice showed context-dependent withdrawal signs and activation of the hippocampus. Receptor internalization was transiently detected in a subset of CA1 neurons, uncovering regionally restricted opioid peptide release. Importantly, a pool of surface receptors always remained, which contrasts with the in vivo profile previously established for exogenous drug-induced internalization. Therefore, a distinct response is observed at the receptor level upon a physiological or pharmacological stimulation. Altogether, direct in vivo GPCR visualization enables mapping receptor stimulation promoted by a behavioral challenge and represents a powerful approach to study endogenous GPCR physiology.
authors.affiliation: Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire, F-67404 Illkirch, Cedex France.
authors.forename: Lauren
authors.initials: L
authors.lastname: Faget
authors.forename: Eric
authors.initials: E
authors.lastname: Erbs
authors.forename: Julie
authors.initials: J
authors.lastname: Le Merrer
authors.forename: Gregory
authors.initials: G
authors.lastname: Scherrer
authors.forename: Audrey
authors.initials: A
authors.lastname: Matifas
authors.forename: Nadia
authors.initials: N
authors.lastname: Benturquia
authors.forename: Florence
authors.initials: F
authors.lastname: Noble
authors.forename: Marion
authors.initials: M
authors.lastname: Decossas
authors.forename: Marc
authors.initials: M
authors.lastname: Koch
authors.forename: Pascal
authors.initials: P
authors.lastname: Kessler
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Vonesch
authors.forename: Yannick
authors.initials: Y
authors.lastname: Schwab
authors.forename: Brigitte L
authors.initials: BL
authors.lastname: Kieffer
authors.forename: Dominique
authors.initials: D
authors.lastname: Massotte
mesh_terms: D000818:Animals; D004744:Enkephalin, Methionine / Q000378:metabolism; D005260:Female; D055879:Gene Knock-In Techniques; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D057054:Molecular Imaging; D009020:Morphine / Q000494:pharmacology; D021381:Protein Transport; D017465:Receptors, Opioid, delta / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D013375:Substance Withdrawal Syndrome / Q000378:metabolism
chemical_list: D017465:Receptors, Opioid, delta; D004744:Enkephalin, Methionine; D009020:Morphine