GATA6 Promotes Angiogenic Function and Survival in Endothelial Cells by Suppression of Autocrine Transforming Growth Factor β/Activin Receptor-like Kinase 5 Signaling

Understanding the transcriptional regulation of angiogenesis could lead to the identification of novel therapeutic targets. We showed here that the transcription factor GATA6 is expressed in different human primary endothelial cells as well as in vascular endothelial cells of mice in vivo. Activation of endothelial cells was associated with GATA6 nuclear translocation, chromatin binding, and enhanced GATA6-dependent transcriptional activation. siRNA-mediated down-regulation of GATA6 after growth factor stimulation led to a dramatically reduced capacity of macro-and microvascular endothelial cells to proliferate, migrate, or form capillary-like structures on Matrigel. Adenoviral overexpression of GATA6 in turn enhanced angiogenic function, especially in cardiac endothelial microvascular cells. Furthermore, GATA6 protected endothelial cells from undergoing apoptosis during growth factor deprivation. Mechanistically, down-regulation of GATA6 in endothelial cells led to increased expression of transforming growth factor (TGF) beta 1 and TGF beta 2, whereas enhanced GATA6 expression, accordingly, suppressed Tgfb1 promoter activity. High TGF beta 1/beta 2 expression in GATA6-depleted endothelial cells increased the activation of the activin receptor-like kinase 5 (ALK5) and SMAD2, and suppression of this signaling axis by TGF beta neutralizing antibody or ALK5 inhibition restored angiogenic function and survival in endothelial cells with reduced GATA6 expression. Together, these findings indicate that GATA6 plays a crucial role for endothelial cell function and survival, at least in part, by suppressing autocrine TGF beta expression and ALK5-dependent signaling.