Krüppel-like factor 15 regulates BMPER in endothelial cells.

AIMS: Bone morphogenetic proteins (BMPs) are involved in embryonic and adult blood vessel formation in health and disease. Previous studies have shown that BMP endothelial cell precursor-derived regulator (BMPER) plays an important role in endothelial cell function and blood vessel formation. BMPER is a key regulator of BMP4 activity and a prerequisite for BMP pathway activation by BMP4 in endothelial cells. Here, we characterize the BMPER promoter and elucidate mechanisms of BMPER regulation. METHODS AND
RESULTS: To investigate transcriptional mechanisms of BMPER expression, the murine BMPER promoter was cloned and characterized. A series of 5' deletions of the BMPER promoter revealed that the proximal promoter contains activating cis-elements. By overexpression or siRNA-based knockdown, we demonstrate that BMPER expression is activated by Krüppel-like factor (KLF) 15. As determined by gelshift analyses, KLF15 binds directly to a predicted KLF-binding element at -284 bp within the BMPER promoter. Co-expression experiments show that Sp1 acts as an antagonist for KLF15-induced promoter activation. Endothelin-1 was identified as a potent inhibitor of KLF15 and BMPER expression in endothelial cells, suggesting that KLF15 is a transducer of endothelin-1 activity on BMPER expression. The selective ET(B) endothelin receptor antagonist BQ788 abolished the downregulation of BMPER expression by endothelin-1.
CONCLUSION: Mechanistically, we found that KLF15 is a strong and direct activator of the BMPER expression. BMPER is downregulated by endothelin-1 in a dose-dependent fashion and in parallel to KLF15. As KLF15 deficiency is accompanied by a vascular phenotype and BMPER is necessary for proper blood vessel formation, we suggest a chain of events in which the effects of endothelin-1 on BMPER are mediated by KLF15.