Transcriptional activation of HIF-1 by RORalpha and its role in hypoxia signaling.
OBJECTIVE
Hypoxia-inducible factor 1alpha (HIF-1alpha) is primarily involved in the adapting of cells to changes in oxygen levels, which is essential for normal vascular function. Recently, physiological roles for retinoic acid-related orphan receptor alpha (RORalpha) have been implicated in cardiovascular diseases such as atherosclerosis. In this study, we have investigated the potential roles of RORalpha in the hypoxia signaling pathway in connection with activation of HIF-1alpha.


RESULTS
Under hypoxic conditions, expression of RORalpha was induced. When RORalpha was introduced exogenously, protein level as well as transcriptional activity of HIF-1alpha was enhanced. Putative ligands of RORalpha, such as melatonin and cholesterol sulfate, induced transcriptional activity for HIF-1alpha, which was abolished by RNA interference against RORalpha. RORalpha was physically associated with HIF-1alpha through DNA binding domain, which was required to the RORalpha-induced stabilization and transcriptional activation of HIF-1alpha. Finally, either infection with adenovirus encoding RORalpha or treatment with ROR ligands enhanced the formation of capillary tubes by human umbilical vascular endothelial cells.


CONCLUSIONS
Our results provide a new insight for the function of RORalpha in amplification of hypoxia signaling and suggest a potential application of RORalpha ligands for the therapy of hypoxia-associated vascular diseases.
Kim
Eun-Jin
EJ
College of Pharmacy and Bio-MAX Institute, Seoul National University, Seoul, Korea.
Yoo
Young-Gun
YG
Yang
Woo-Kyeom
WK
Lim
Young-Soun
YS
Na
Tae-Young
TY
Lee
In-Kyu
IK
Lee
Mi-Ock
MO
D000818:Animals; D001665:Binding Sites; D015687:Cell Hypoxia / Q000235:genetics; D002788:Cholesterol Esters / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D008550:Melatonin / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D018919:Neovascularization, Physiologic; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D002788:Cholesterol Esters; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008024:Ligands; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D034741:RNA, Small Interfering; C539738:RORA protein, human; D018160:Receptors, Cytoplasmic and Nuclear; D015534:Trans-Activators; D008550:Melatonin; C007045:cholesteryl sulfate