title: Beta-arrestin-dependent parathyroid hormone-stimulated extracellular signal-regulated kinase activation and parathyroid hormone type 1 receptor internalization.
abstract: PTH regulates renal calcium homeostasis by actions on the distal nephron. PTH-induced calcium transport in mouse distal convoluted tubule (DCT) cells requires activation of ERK1/2. ERK activation by beta-adrenergic receptors occurs in a biphasic manner and involves receptor internalization. An early rapid phase is beta-arrestin (betaAr) independent, whereas prolonged activation is betaAr dependent. We characterized PTH-stimulated ERK activation and the involvement of receptor internalization and betaAr dependence. In DCT cells, PTH transiently activated ERK maximally at 5 min and then returned to baseline. betaAr dependence of PTH receptor (PTH1R)-mediated ERK stimulation was assessed using mouse embryonic fibroblasts (MEFs) from betaAr1- and -2-null mice. In wild-type MEFs, PTH(1-34)-stimulated ERK activation peaked after 5 min, was 50% maximal after 15 min, and then recovered to 80% of maximal stimulation by 30 min. In MEFs null for betaAr1 and -2, PTH-stimulated ERK activation peaked by 5 min and returned to baseline. The effect was identical in betaAr2-null MEFs. In betaAr1-null MEFs, ERK exhibited delayed activation and remained elevated. PTH-stimulated ERK activation and receptor endocytosis were not inhibited by the clathrin-binding domain of betaAr1 [Ar(319-418)]. Coexpression of the sodium proton exchanger regulatory factor 1 (NHERF1) with Ar(319-418) blocked PTH1R internalization. We conclude that PTH-stimulated ERK activation in DCT cells proceeds with a rapid but transient phase that may involve betaAr1. Furthermore, the betaAr-dependent late phase of ERK activation by PTH requires the participation of betaAr2 and PTH1R internalization.
authors.affiliation: Department of Pharmacology, Renal Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: W Bruce
authors.initials: WB
authors.lastname: Sneddon
authors.forename: Peter A
authors.initials: PA
authors.lastname: Friedman
mesh_terms: D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004705:Endocytosis / Q000502:physiology*; D005347:Fibroblasts / Q000166:cytology; D007686:Kidney Tubules, Distal / Q000166:cytology; D051379:Mice; D008817:Mice, Mutant Strains; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010281:Parathyroid Hormone / Q000378:metabolism*; D010766:Phosphorylation; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D010281:Parathyroid Hormone; D044168:Receptor, Parathyroid Hormone, Type 1; D000071557:beta-Arrestins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium