Rab3D and annexin A2 play a role in regulated secretion of vWF, but not tPA, from endothelial cells

Knop M, Aareskjold E, Bode G and Gerke V
Source: EMBO J
Publication Date: (2004)
Issue: 23(15): 2982-2992
Research Area:
Cells used in publication:
Endothelial, umbilical vein, human (HUVEC)
Species: human
Tissue Origin: vein
Human umbilical vein endothelial cells (HUVECs) were transfected with different variants of YFP-Rab3D having effects on WPb morphology and vWF secretion, but not on tPA secretion. Similar effects on secretion were seen when knocking down annexin A2/S100A10 complex by transfecting HUVECs with siRNA.
von-Willebrand factor (vWF) and tissue-type plasminogen activator (tPA) are products of endothelial cells acutely released into the vasculature following cell activation. Both factors are secreted after intraendothelial Ca(2+) mobilization, but exhibit opposing physiological effects with vWF inducing coagulation and tPA triggering fibrinolysis. To identify components that could regulate differentially the release of pro- and antithrombogenic factors, we analyzed the contribution of Rab3D and the annexin A2/S100A10 complex, proteins implicated in exocytotic events in other systems. We show that mutant Rab3D proteins interfere with the formation of bona fide Weibel-Palade bodies (WPbs), the principal storage granules of multimeric vWF, and consequently the acute, histamine-induced release of vWF. In contrast, neither appearance nor exocytosis of tPA storage granules is affected. siRNA-mediated downregulation of annexin A2/S100A10 and disruption of the complex by microinjection of peptide competitors result in a marked reduction in vWF but not tPA secretion, without affecting the appearance of WPbs. This indicates that distinct mechanisms underlie the acute secretion of vWF and tPA, enabling endothelial cells to fine-regulate the release of thrombogenic and fibrinolytic factors.