cAMP enhances estrogen-related receptor alpha (ERRalpha) transcriptional activity at the SP-A promoter by increasing its interaction with protein kinase A and steroid receptor coactivator 2 (SRC-2)

Mol Endocrinol. 2009 Jun;23(6):772-83. doi: 10.1210/me.2008-0282. Epub 2009 Mar 5.

Abstract

Estrogen-related receptor (ERRalpha) plays a critical role in basal and cAMP-induced expression of the human surfactant protein-A (SP-A) gene in lung type II cells through direct binding to an ERR response element (ERRE, 5'-TGACCTTA-3') within its 5'-flanking region. Furthermore, protein kinase A (PKA) up-regulates ERRalpha activation of the hSP-A promoter. In the present study, using cultured human fetal lung type II cells, we observed that cAMP enhanced ERRalpha phosphorylation and nuclear expression levels. cAMP/PKA stimulation of ERRalpha activation of the SP-A promoter was blocked by the PKA inhibitor, H89, whereas the MAPK P38 inhibitor, SB203580, and the MAPK kinase inhibitor, PD98059, had negligible to modest effects. This suggests that cAMP acts selectively through PKA to increase ERRalpha transcriptional activity. Of several coactivators tested, steroid receptor coactivator 2 (SRC-2) had the most pronounced effect to increase ERRalpha transcriptional activity at the SP-A promoter; this was enhanced by cotransfection with PKA catalytic subunit (PKAcat). Interestingly, SRC-2, ERRalpha, and PKAcat in type II cell nuclear extracts interacted at the ERRE; this was enhanced by cAMP and inhibited by H89. cAMP increased in vivo binding of PKAcat and SRC-2 to the ERRE genomic region in lung type II cells. In mutagenesis studies, three serines (S87, S114, and S277) were found to be critical for PKA and SRC-2 induction of ERRalpha transcriptional activity. Collectively, these findings indicate that cAMP/PKA signaling enhances ERRalpha phosphorylation and nuclear localization, recruitment to the SP-A promoter, and interaction with PKAcat and SRC-2, resulting in the up-regulation of SP-A gene transcription.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • Cyclic AMP / pharmacology*
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • ERRalpha Estrogen-Related Receptor
  • Enzyme Activation / drug effects
  • Fetus / cytology
  • Genome, Human / genetics
  • Humans
  • Isoquinolines / pharmacology
  • Lung / cytology
  • Mice
  • Nuclear Receptor Coactivator 2 / metabolism*
  • Phosphorylation / drug effects
  • Promoter Regions, Genetic / genetics*
  • Protein Binding / drug effects
  • Protein Transport / drug effects
  • Pulmonary Surfactant-Associated Protein A / genetics*
  • Pulmonary Surfactant-Associated Protein A / metabolism
  • Receptors, Estrogen / genetics*
  • Receptors, Estrogen / metabolism
  • Response Elements / genetics
  • Serine / metabolism
  • Sulfonamides / pharmacology
  • Threonine / metabolism
  • Transcription, Genetic / drug effects*

Substances

  • Isoquinolines
  • Nuclear Receptor Coactivator 2
  • Pulmonary Surfactant-Associated Protein A
  • Receptors, Estrogen
  • Sulfonamides
  • Threonine
  • Serine
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases
  • N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide