Coactivators YAP and TAZ Contribute Differently to the Transcriptional Regulation of VWF in Endothelial Cells

Background Upstream signals and associated signalling axes that contribute to the differential VWF expression observed across various vascular beds remain unclear. Transcriptional coactivators YAP and TAZ, through transcription factors including TEAD, may contribute distinctly to this heterogeneity in response to external mechanical stimuli.Objectives Investigate the role of YAP/TAZ in the transcriptional regulation of VWF in endothelial cells (ECs).Methods Human umbilical vein ECs (HUVECs) and human aortic ECs (HAECs) were assessed for levels of VWF mRNA and VWF:Ag following YAP/TAZ gene silencing by siRNA. VWF promoter activity was measured in HUVECs using luciferase reporter constructs, both before and after inactivating the promoter's single TEAD site. Changes in VWF mRNA and VWF:Ag were measured in ECs exposed to shear stress (5-30 dynes/cm2), and immunofluorescent microscopy was used to visualise and quantify intracellular TAZ localisation.Results YAP and TAZ assumed different roles between EC subtypes. In HUVECs, we observed a TAZ-dominant contribution to VWF expression across siRNA and shear stress experiments. In HAECs, our results are consistent with a negative regulatory role of YAP on TAZ. Modifications to the TEAD sequence reduced VWF expression in HUVECs, indicating mechanistic convergence of YAP/TAZ on this site, further supported by chromatin immunoprecipitation (ChIP) and in silico ChIP-seq analysis. Immunocytochemistry displayed cytoplasmic TAZ localisation under high laminar flow, implicating shear stress as a negative regulator of VWF expression.Conclusion YAP and TAZ are novel contributors to the transcriptional regulation of VWF in ECs through a TEAD-dependent mechanism, acting independently and distinctly in various EC subtypes.