Abstract
After endothelial injury, the transcription factor Krüppel-like factor 6 (KLF6) translocates into the cell nucleus to regulate a variety of target genes involved in angiogenesis, vascular repair and remodeling, including components of the membrane transforming growth factor beta (TGF-β) receptor complex such as endoglin and activin receptor-like kinase 1. The membrane metalloproteinase 14 (MMP14 or MT1-MMP) targets endoglin to release soluble endoglin and is involved in vascular inflammation and endothelial tubulogenesis. However, little is known about the regulation of MMP14 expression during vascular wounding. In vitro denudation of monolayers of human endothelial cell monolayers leads to an increase in the KLF6 gene transcriptional rate, followed by an upregulation of MMP14 and release of soluble endoglin. Concomitant with this process, MMP14 co-localizes with endoglin in the sprouting endothelial cells surrounding the wound border. MMP14 expression at mRNA and protein levels is increased by ectopic KLF6 and downregulated by KLF6 suppression in cultured endothelial cells. Moreover, after wire-induced endothelial denudation, Klf6+/− mice show lower levels of MMP14 in their vasculature compared with their wild-type siblings. Ectopic cellular expression of KLF6 results in an increased transcription rate of MMP14, and chromatin immunoprecipitation assays show that KLF6 interacts with MMP14 promoter in ECs, this interaction being enhanced during wound healing. Furthermore, KLF6 markedly increases the transcriptional activity of different reporter constructs of MMP14 gene promoter. These results suggest that KLF6 regulates MMP14 transcription and is a critical player of the gene expression network triggered during endothelial repair.Electronic supplementary materialThe online version of this article (doi:10.1007/s10456-016-9495-8) contains supplementary material, which is available to authorized users.
Highlights
The endothelium plays a crucial role in regulating pathophysiological processes like vascular injury, angiogenesis, vascular remodeling, tumor growth, vasoconstriction, vasodilatation, inflammation or blood vessel permeability
Our results demonstrate that on vascular injury, Kruppel-like factor 6 (KLF6) transcriptionally upregulates the expression of MMP14 that is associated with increased MMP14 proteolytic activity leading to the release of soluble endoglin from endothelial cells (ECs)
Levels of soluble endoglin released to the medium from human umbilical vein-derived endothelial cells (HUVEC) subjected to endothelial denudation for 6 h were measured by ELISA (i). j KLF6 suppression was carried out in HUVECs by nucleofection with siRNA specific for KLF6, using Scrambled siRNA as a control
Summary
The endothelium plays a crucial role in regulating pathophysiological processes like vascular injury, angiogenesis, vascular remodeling, tumor growth, vasoconstriction, vasodilatation, inflammation or blood vessel permeability During all these processes, proliferation, migration and invasion of endothelial cells (ECs) are essential and the study of the regulatory mechanisms involved in endothelial gene expression is a necessary step in the search of therapeutic targets. KLF6 expression increases and translocates into the nucleus to enhance the transcriptional activity of endoglin and activin receptor-like kinase 1 (ALK1) [34, 35]; two key TGF-b receptors involved in vascular remodeling and angiogenesis [36]. Our results demonstrate that on vascular injury, KLF6 transcriptionally upregulates the expression of MMP14 that is associated with increased MMP14 proteolytic activity leading to the release of soluble endoglin from ECs
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