Nuclear alpha1-adrenergic receptors signal activated ERK localization to caveolae in adult cardiac myocytes

Circ Res. 2008 Oct 24;103(9):992-1000. doi: 10.1161/CIRCRESAHA.108.176024. Epub 2008 Sep 18.

Abstract

We previously identified an alpha1-AR-ERK (alpha1A-adrenergic receptor-extracellular signal-regulated kinase) survival signaling pathway in adult cardiac myocytes. Here, we investigated localization of alpha1-AR subtypes (alpha1A and alpha1B) and how their localization influences alpha1-AR signaling in cardiac myocytes. Using binding assays on myocyte subcellular fractions or a fluorescent alpha1-AR antagonist, we localized endogenous alpha1-ARs to the nucleus in wild-type adult cardiac myocytes. To clarify alpha1 subtype localization, we reconstituted alpha1 signaling in cultured alpha1A- and alpha1B-AR double knockout cardiac myocytes using alpha1-AR-green fluorescent protein (GFP) fusion proteins. Similar to endogenous alpha1-ARs and alpha1A- and alpha1B-GFP colocalized with LAP2 at the nuclear membrane. alpha1-AR nuclear localization was confirmed in vivo using alpha1-AR-GFP transgenic mice. The alpha1-signaling partners Galphaq and phospholipase Cbeta1 also colocalized with alpha1-ARs only at the nuclear membrane. Furthermore, we observed rapid catecholamine uptake mediated by norepinephrine-uptake-2 and found that alpha1-mediated activation of ERK was not inhibited by a membrane impermeant alpha1-blocker, suggesting alpha1 signaling is initiated at the nucleus. Contrary to prior studies, we did not observe alpha1-AR localization to caveolae, but we found that alpha1-AR signaling initiated at the nucleus led to activated ERK localized to caveolae. In summary, our results show that nuclear alpha1-ARs transduce signals to caveolae at the plasma membrane in cardiac myocytes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic alpha-1 Receptor Antagonists
  • Adrenergic alpha-Antagonists / pharmacology
  • Animals
  • Catecholamines / metabolism
  • Caveolae / drug effects
  • Caveolae / enzymology*
  • Cell Fractionation
  • Cell Nucleus / drug effects
  • Cell Nucleus / enzymology*
  • Cells, Cultured
  • DNA-Binding Proteins / metabolism
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • GTP-Binding Protein alpha Subunits, Gq-G11 / metabolism
  • Green Fluorescent Proteins / metabolism
  • Membrane Proteins / metabolism
  • Mice
  • Mice, Knockout
  • Microscopy, Confocal
  • Myocytes, Cardiac / drug effects
  • Myocytes, Cardiac / enzymology*
  • Organic Cation Transport Proteins / metabolism
  • Phospholipase C beta / metabolism
  • Phosphorylation
  • Prazosin / pharmacology
  • Receptors, Adrenergic, alpha-1 / genetics
  • Receptors, Adrenergic, alpha-1 / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction* / drug effects
  • Time Factors

Substances

  • Adra1a protein, mouse
  • Adra1b protein, mouse
  • Adrenergic alpha-1 Receptor Antagonists
  • Adrenergic alpha-Antagonists
  • Catecholamines
  • DNA-Binding Proteins
  • Membrane Proteins
  • Organic Cation Transport Proteins
  • Receptors, Adrenergic, alpha-1
  • Recombinant Fusion Proteins
  • lamina-associated polypeptide 2
  • solute carrier family 22 (organic cation transporter), member 3
  • Green Fluorescent Proteins
  • Extracellular Signal-Regulated MAP Kinases
  • Phospholipase C beta
  • Plcb1 protein, mouse
  • GTP-Binding Protein alpha Subunits, Gq-G11
  • Prazosin