Synaptotagmin 5 regulates Ca2+-dependent Weibel–Palade body exocytosis in human endothelial cells

Camille Lenzi, Jennifer Stevens, Daniel Osborn, Matthew Hannah, Ruben Bierings, Tom Carter*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Elevations of intracellular free Ca2+ concentration ([Ca2+]i) are a potent trigger for Weibel–Palade body (WPB) exocytosis and secretion of von Willebrand factor (VWF) from endothelial cells; however, the identity of WPB-associated Ca2+-sensors involved in transducing acute increases in [Ca2+]i into granule exocytosis remains unknown. Here, we show that synaptotagmin 5 (SYT5) is expressed in human umbilical vein endothelial cells (HUVECs) and is recruited to WPBs to regulate Ca2+-driven WPB exocytosis. Western blot analysis of HUVECs identified SYT5 protein, and exogenously expressed SYT5–mEGFP localised almost exclusively to WPBs. shRNA-mediated knockdown of endogenous SYT5 (shSYT5) reduced the rate and extent of histamine-evoked WPB exocytosis and reduced secretion of the WPB cargo VWF-propeptide (VWFpp). The shSYT5-mediated reduction in histamine-evoked WPB exocytosis was prevented by expression of shRNA-resistant SYT5–mCherry. Overexpression of SYT5–EGFP increased the rate and extent of histamine-evoked WPB exocytosis, and increased secretion of VWFpp. Expression of a Ca2+-binding defective SYT5 mutant (SYT5-Asp197Ser–EGFP) mimicked depletion of endogenous SYT5. We identify SYT5 as a WPB-associated Ca2+ sensor regulating Ca2+-dependent secretion of stored mediators from vascular endothelial cells.

Original languageEnglish
Article numberjcs221952
JournalJournal of Cell Science
Issue number5
Publication statusPublished - 1 Mar 2019

Bibliographical note

Funding Information:
studentship. R.B. was supported by a European Hematology Association Research Fellowship and by a grant from the Landsteiner Foundation for Blood Transfusion Research (LSBR-1707).

Funding Information:
T.C. was supported by an UK Medical Research Council (MRC) (grant MC_PC_13053). C.L. was supported by an St George’s University London PhD

Publisher Copyright:
© 2019 Published by The Company of Biologists Ltd.


  • Ca2+
  • Endothelial
  • Exocytosis
  • Secretion
  • Synaptotagmin
  • Weibel–Palade body


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