Differences in the cellular localization and agonist-mediated internalization properties of the α1-adrenoceptor subtypes

Dan Chalothorn, Dan F. McCune, Stephanie E. Edelmann, Mary L. García-Cazarín, Gozoh Tsujimoto, Michael T. Piascik

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123 Scopus citations


The cellular localization, agonist-mediated internalization, and desensitization properties of the α1adrenoceptor (α1-AR) sub-types conjugated with green fluorescent protein (α1-AR/GFP) were assessed using real-time imaging of living, transiently transfected human embryonic kidney (HEK) 293 cells. The α1B-AR/GFP fluorescence was detected predominantly on the cell surface. Stimulation of the α1B-AR with phenylephrine led to an increase in extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and promoted rapid α1B-AR/GFP internalization. Long-term exposure (15 h) to phenylephrine resulted in desensitization of the α1B-AR-mediated activation of ERK1/2 phosphorylation. α1A-AR/GFP fluorescence was detected not only on the cell surface but also intracellularly. The rate of internalization of the cell surface population α1A-AR/GFPs was slower than that seen for the α1B-AR. Agonist exposure also resulted in desensitization of the α1A-AR-mediated increase in ERK1/2 phosphorylation. The α1D-AR/GFP fluorescence was detected mainly intracellularly, and this localization was unaffected by exposure to phenylephrine. Phenylephrine treatment of α1D-AR/GFP expressing cells increased ERK1/2 phosphorylation. However, this increase was not significant. Cotransfection with β-arrestin 1 did not increase the rate or extent of agonist-stimulated α1A- or α1B-AR/GFP internalization. However, a dominant-negative form of the β-arrestin 1, β-arrestin 1 (319-418), blocked agonist-mediated internalization of both the α1A- and α1B-ARs. These data show that transfected α1-AR/GFP fusion proteins are functional, that there are differences in the cellular distribution and agonist-mediated internalization between the α1-ARs, and that agonist-mediated α1-AR internalization is dependent on arrestins and can be desensitized by long-term exposure to an agonist. These differences could contribute to the diversity in physiologic responses regulated by the α1-ARs.

Original languageEnglish
Pages (from-to)1008-1016
Number of pages9
JournalMolecular Pharmacology
Issue number5
StatePublished - 2002

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology


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