Smad2 Mediates Transforming Growth Factor-β Induction of Endothelial Nitric Oxide Synthase Expression

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Abstract
Transforming growth factor-β (TGF-β) increases expression of endothelial nitric oxide synthase (eNOS), although the precise mechanism by which it does so is unclear. We report that Smad2, a transcription factor activated by TGF-β, mediates TGF-β induction of eNOS in endothelial cells. TGF-β induces Smad2 translocation from cytoplasm to nucleus, where it directly interacts with a specific region of the eNOS promoter. Overexpression of Smad2 increases basal levels of eNOS, and further increases TGF-β stimulation of eNOS expression. Ectopic expression of Smurf, an antagonizer of Smad2, decreases Smad2 expression and blocks TGF-β induction of eNOS. Because Smad2 can interact with a variety of transcription factors, coactivators, and corepressors, Smad2 may thus act as an integrator of multiple signals in the regulation of eNOS expression.