title: Regulation of CB1 cannabinoid receptor trafficking by the adaptor protein AP-3.
abstract: Cannabinoid receptor 1 (CB(1)) is an abundant G protein-coupled receptor, involved in a number of physiological processes. This receptor is localized at the plasma membrane, as well as in intracellular vesicles. The trafficking events leading to this intracellular localization remain controversial. In this study, we examine the differential trafficking of CB(1) receptors and its implication on signaling. We find that the transfected tagged receptors are predominantly at the plasma membrane, whereas endogenous receptors exhibit an intracellular localization. We also find that intracellular endogenous CB(1) receptors do not have an endocytic origin. Instead, these receptors associate with the adaptor protein AP-3 and traffic to the lysosomes. siRNA-mediated AP-3delta knockdown leads to enhanced cell surface localization of CB(1) receptors. Finally, we show that CB(1) receptors in the late endosomal/lysosomal compartment are associated with heterotrimeric G proteins and mediate signal transduction. These results suggest that intracellular CB(1) receptors are functional and that their spatial segregation is likely to significantly affect receptor function.
authors.affiliation: Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA.
authors.forename: Raphael
authors.initials: R
authors.lastname: Rozenfeld
authors.forename: Lakshmi A
authors.initials: LA
authors.lastname: Devi
mesh_terms: D033963:Adaptor Protein Complex 3; D000818:Animals; D019921:Biotinylation; D018929:Cell Culture Techniques; D002460:Cell Line; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000502:physiology; D004268:DNA-Binding Proteins / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000502:physiology; D006706:Homeostasis; D006801:Humans; D007668:Kidney; D051379:Mice; D018613:Microscopy, Confocal; D009474:Neurons / Q000166:cytology / Q000502:physiology; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000235:genetics; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism*; D014157:Transcription Factors / Q000502:physiology*; D014162:Transfection
chemical_list: D033963:Adaptor Protein Complex 3; D004268:DNA-Binding Proteins; D034741:RNA, Small Interfering; D043884:Receptor, Cannabinoid, CB1; D014157:Transcription Factors