PB0809 - Transcriptional coactivators YAP and TAZ contribute differently to the transcriptional regulation of VWF in venous and arterial endothelial cells

Background: Upstream signals regulating VWF transcription are poorly understood. These factors may explain the different levels of VWF synthesis in various vascular beds. Transcriptional coactivators YAP/TAZ regulate gene expression responses to extracellular stimuli such as mechanical shear stress through transcription factors including TEAD.

Aims: Investigate the role of YAP/TAZ in the transcriptional regulation of VWF in venous and arterial endothelial cells.

Methods: YAP/TAZ genes were silenced (siRNA) in human umbilical vein endothelial cells (HUVEC) and human aortic endothelial cells (HAEC). VWF was quantified in cell lysates and serum-free media 96h post-transfection. VWF promoter constructs were nucleofected into HUVEC and HAEC. Test and control luciferase activity was measured 72h post-nucleofection. JASPAR CORE 2022 was used to identify putative TEAD-binding sites in the VWF promoter sequence.

Results: In HUVEC, siYAP/TAZ reduced VWF levels by 66% in the media (p < 0.0001) and 46% in the lysate (p=0.033). siTAZ reduced VWF by 55% (p < 0.0001) and 40% (p=0.5834) in the media and lysate, respectively. VWF mRNA decreased by 46% with siYAP/TAZ (p=0.152) and by 22% with siTAZ (p=0.735). VWF mRNA and protein in the media and lysate was unchanged by siYAP (p>0.05). Contrastingly, in HAEC, siYAP/TAZ and siTAZ did not change VWF levels in the media or lysate (p>0.05). Rather, VWF increased by 80% with siYAP in the lysate (p < 0.05) and by 70% in the media (p=0.064). VWF mRNA increased by 237% with siYAP (p < 0.05) and by 150% with siTAZ (p=0.497) and siYAP/TAZ (p=0.477). Deletion of the TEAD-binding site (TEADdel) from our normal VWF promoter construct reduced luciferase expression in HUVEC by 73% (p < 0.05) and HAEC by 55% (p=0.057).

Conclusion(s): YAP/TAZ contribute to the transcriptional regulation of VWF, with different roles in venous and arterial endothelial cells. Reduced VWF promoter activity by TEADdel suggests involvement of this site in the transcriptional regulation of VWF by YAP/TAZ.