Angiopoietin-1 modulates endothelial cell function and gene expression via the transcription factor FKHR (FOXO1).
Despite genetic evidence establishing angiopoietin-1 (Ang-1) as an essential regulator of vascular development, the molecular mechanisms underlying Ang-1 function are almost completely uncharacterized. In this report, we demonstrate that Ang-1, via Akt activation, is a potent inhibitor of the forkhead transcription factor FKHR (FOXO1), identifying for the first time a nuclear signaling pathway through which Ang-1 modulates gene expression. We use microarray analysis to show that FKHR, whose function in endothelial cells has not previously been elucidated, regulates many genes associated with vascular destabilization and remodeling (including angiopoietin-2, an Ang-1 antagonist) and endothelial cell apoptosis (e.g., survivin, TRAIL). Ang-1 inhibits FKHR-mediated changes in gene expression and FKHR-induced apoptosis. Analysis of gene expression changes induced by an activated version of Akt confirms that FKHR is a major target through which Akt regulates transcription in endothelial cells. We use RNA interference to demonstrate that FKHR is required for the expression of genes (including Ang-2) that have important vascular functions. Our data suggest a novel, tissue-specific role for the Akt/FKHR pathway in the vasculature and suggest a mechanistic basis for the previously described actions of Ang-1 as a regulator of endothelial cell survival and blood vessel stability.
Daly
Christopher
C
Regeneron Pharmaceuticals, Inc., Tarrytown, NY 10591, USA. christopher.daly@regeneron.com
Wong
Vivian
V
Burova
Elena
E
Wei
Yi
Y
Zabski
Stephanie
S
Griffiths
Jennifer
J
Lai
Ka-Man
KM
Lin
Hsin Chieh
HC
Ioffe
Ella
E
Yancopoulos
George D
GD
Rudge
John S
JS
D042683:Angiopoietin-1 / Q000494:pharmacology* / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D002417:Cattle; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D006801:Humans; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
D042683:Angiopoietin-1; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt