Transcriptional and post-translation regulation of the Tie1 receptor by fluid shear stress changes in vascular endothelial cells

The interaction between the vascular endothelium and hemodynamic forces (and more specifically, fluid shear stress), induced by the flow of blood, plays a major role in vascular remodeling and in new blood vessels formation via a process termed arteriogenesis. Tiel is an orphan tyrosine kinase receptor expressed almost exclusively in endothelial cells and is required for normal vascular development and maintenance. The present study demonstrates that Tiel expression is rapidly down-regulated in endothelial cells exposed to shear stress, and more so to shear stress changes. This down-regulation is accompanied by a rapid cleavage of Tiel and binding of the cleaved Tiel 45 kDa endodomain to Tie2. The rapid cleavage of Tiel is followed by a transcriptional down-regulation in response to shear stress. The activity of the Tiel promoter is suppressed by shear stress and by tumor necrosis factor a,. Shear stress-induced transcriptional suppression of Tiel is mediated by a negative shear stress response element, localized in a region of 250 by within the promoter. The rapid down-regulation of Tiel by shear stress changes and its rapid binding to Tie2 may be required for destabilization of endothelial cells in order to initiate the process of vascular restructuring.