Noradrenaline, oxymetazoline and phorbol myristate acetate induce distinct functional actions and phosphorylation patterns of α 1A-adrenergic receptors

Biochim Biophys Acta Mol Cell Res. 2017 Dec;1864(12):2378-2388. doi: 10.1016/j.bbamcr.2017.09.002. Epub 2017 Sep 6.


In LNCaP cells that stably express α1A-adrenergic receptors, oxymetazoline increased intracellular calcium and receptor phosphorylation, however, this agonist was a weak partial agonist, as compared to noradrenaline, for calcium signaling. Interestingly, oxymetazoline-induced receptor internalization and desensitization displayed greater effects than those induced by noradrenaline. Phorbol myristate acetate induced modest receptor internalization and minimal desensitization. α1A-Adrenergic receptor interaction with β-arrestins (colocalization/coimmunoprecipitation) was induced by noradrenaline and oxymetazoline and, to a lesser extent, by phorbol myristate acetate. Oxymetazoline was more potent and effective than noradrenaline in inducing ERK 1/2 phosphorylation. Mass spectrometric analysis of immunopurified α1A-adrenergic receptors from cells treated with adrenergic agonists and the phorbol ester clearly showed that phosphorylated residues were present both at the third intracellular loop and at the carboxyl tail. Distinct phosphorylation patterns were observed under the different conditions. The phosphorylated residues were: a) Baseline and all treatments: T233; b) noradrenaline: S220, S227, S229, S246, S250, S389; c) oxymetazoline: S227, S246, S381, T384, S389; and d) phorbol myristate acetate: S246, S250, S258, S351, S352, S401, S402, S407, T411, S413, T451. Our novel data, describing the α1A-AR phosphorylation sites, suggest that the observed different phosphorylation patterns may participate in defining adrenoceptor localization and action, under the different conditions examined.

Keywords: Biased agonism; Desensitization; Mass spectrometry; Oxymetazoline; Phosphorylation sites; α(1A)-Adrenergic receptors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium Signaling / drug effects*
  • Cell Line, Tumor
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • MAP Kinase Signaling System / drug effects
  • Mass Spectrometry
  • Norepinephrine / pharmacology
  • Oxymetazoline / pharmacology
  • Phosphorylation / genetics
  • Protein Kinase C / genetics
  • Proteolysis*
  • Receptors, Adrenergic, alpha-1 / genetics*
  • Receptors, Adrenergic, alpha-1 / metabolism
  • Tetradecanoylphorbol Acetate / pharmacology


  • Receptors, Adrenergic, alpha-1
  • Oxymetazoline
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate
  • Norepinephrine