title: Protein phosphatase 2A mediates resensitization of the neurokinin 1 receptor.
abstract: Activated G protein-coupled receptors (GPCRs) are phosphorylated and interact with β-arrestins, which mediate desensitization and endocytosis. Endothelin-converting enzyme-1 (ECE-1) degrades neuropeptides in endosomes and can promote recycling. Although endocytosis, dephosphorylation, and recycling are accepted mechanisms of receptor resensitization, a large proportion of desensitized receptors can remain at the cell surface. We investigated whether reactivation of noninternalized, desensitized (phosphorylated) receptors mediates resensitization of the substance P (SP) neurokinin 1 receptor (NK(1)R). Herein, we report a novel mechanism of resensitization by which protein phosphatase 2A (PP2A) is recruited to dephosphorylate noninternalized NK(1)R. A desensitizing concentration of SP reduced cell-surface SP binding sites by only 25%, and SP-induced Ca(2+) signals were fully resensitized before cell-surface binding sites started to recover, suggesting resensitization of cell-surface-retained NK(1)R. SP induced association of β-arrestin1 and PP2A with noninternalized NK(1)R. β-Arrestin1 small interfering RNA knockdown prevented SP-induced association of cell-surface NK(1)R with PP2A, indicating that β-arrestin1 mediates this interaction. ECE-1 inhibition, by trapping β-arrestin1 in endosomes, also impeded SP-induced association of cell-surface NK(1)R with PP2A. Resensitization of NK(1)R signaling required both PP2A and ECE-1 activity. Thus, after stimulation with SP, PP2A interacts with noninternalized NK(1)R and mediates resensitization. PP2A interaction with NK(1)R requires β-arrestin1. ECE-1 promotes this process by releasing β-arrestin1 from NK(1)R in endosomes. These findings represent a novel mechanism of PP2A- and ECE-1-dependent resensitization of GPCRs.
authors.affiliation: Department of Surgery, University of California, San Francisco, 94143-0660, USA.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Murphy
authors.forename: Dirk
authors.initials: D
authors.lastname: Roosterman
authors.forename: Graeme S
authors.initials: GS
authors.lastname: Cottrell
authors.forename: Benjamin E
authors.initials: BE
authors.lastname: Padilla
authors.forename: Micha
authors.initials: M
authors.lastname: Feld
authors.forename: Eva
authors.initials: E
authors.lastname: Brand
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Cedron
authors.forename: Nigel W
authors.initials: NW
authors.lastname: Bunnett
authors.forename: Martin
authors.initials: M
authors.lastname: Steinhoff
mesh_terms: D001430:Bacteriocins; D002462:Cell Membrane / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D010455:Peptides; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled; D018040:Receptors, Neurokinin-1 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D001430:Bacteriocins; D007211:Indoles; D008301:Maleimides; D010455:Peptides; D020033:Protein Isoforms; D043562:Receptors, G-Protein-Coupled; D018040:Receptors, Neurokinin-1; C110490:mutacin II prepeptide, bacteria; D011493:Protein Kinase C; D054648:Protein Phosphatase 2; C070515:bisindolylmaleimide I