title: Regulation of the cellular localization and signaling properties of the alpha(1B)- and alpha(1D)-adrenoceptors by agonists and inverse agonists.
abstract: The regulation of the cellular distribution and intracellular signaling properties of the alpha(1B)- and alpha(1D)- adrenoceptor (alpha(1)-AR) subtypes was examined in stably transfected Rat 1 fibroblasts. In unstimulated cells, alpha(1B)-AR expression was noted primarily on the cell surface. Treatment with phenylephrine induced internalization of the alpha(1B)-AR and promoted association with arrestin 2. The internalized alpha(1B)-AR colocalized with the transferrin receptor, an endosomal marker. In unstimulated fibroblasts, the alpha(1D)-AR was detected in a perinuclear orientation and was colocalized with arrestin 2 in a compartment also containing the transferrin receptor. After treatment with prazosin, which exhibits inverse agonist properties, the alpha(1D)-AR was redistributed from intracellular sites to the cellular periphery and was no longer associated with the transferrin receptor or arrestin 2. alpha(1D)-AR-expressing cells exhibited a high degree of basal activity for both inositol phosphate formation and extracellular signal regulated kinase (ERK), which was reduced by treatment with prazosin. In these cells, phenylephrine induced a dose-dependent increase in inositol phosphate formation but had no effect on ERK activity. In alpha(1B) -AR-expressing cells, phenylephrine stimulated both inositol phosphate formation and ERK activity. These data show that: 1) there are differences in the cellular localization of the alpha(1)-AR subtypes; 2) the alpha(1B)-AR exhibits expected G protein-coupled receptor activity regarding cellular localization, agonist-mediated internalization, and coupling to second messengers; and 3) the alpha(1D)-AR is constitutively active and, as a result, is localized to intracellular compartments involved in receptor recycling.
authors.affiliation: The Department of Pharmacology, The Division of Pharmaceutical Sciences, The University of Kentucky College of Pharmacy, Lexington, Kentucky 40536-0084, USA.
authors.forename: D F
authors.initials: DF
authors.lastname: McCune
authors.forename: S E
authors.initials: SE
authors.lastname: Edelmann
authors.forename: J R
authors.initials: JR
authors.lastname: Olges
authors.forename: G R
authors.initials: GR
authors.lastname: Post
authors.forename: B A
authors.initials: BA
authors.lastname: Waldrop
authors.forename: D J
authors.initials: DJ
authors.lastname: Waugh
authors.forename: D M
authors.initials: DM
authors.lastname: Perez
authors.forename: M T
authors.initials: MT
authors.lastname: Piascik
mesh_terms: D000322:Adrenergic Agonists / Q000494:pharmacology*; D018674:Adrenergic Antagonists / Q000494:pharmacology; D058646:Adrenergic alpha-1 Receptor Agonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D000818:Animals; D002478:Cells, Cultured; D006801:Humans; D007150:Immunohistochemistry; D007295:Inositol Phosphates; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D051381:Rats; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection
chemical_list: C547716:ADRA1B protein, human; C547719:ADRA1D protein, human; C547718:Adra1b protein, rat; C547721:Adra1d protein, rat; D000322:Adrenergic Agonists; D018674:Adrenergic Antagonists; D058646:Adrenergic alpha-1 Receptor Agonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D007295:Inositol Phosphates; D018340:Receptors, Adrenergic, alpha-1; D011956:Receptors, Cell Surface; D020928:Mitogen-Activated Protein Kinases