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J Cell Sci. 2019 Feb 15;132(5). pii: jcs221952. doi: 10.1242/jcs.221952.

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

Author information

1
Molecular and Clinical Sciences Research Institute, St George's, University of London, London SW18 ORE, UK.
2
MRC National Institute for Medical Research, London NW7 1AA, UK.
3
Microbiology Services Colindale, Public Health England, London, NW9 5EQ, UK.
4
Plasma Proteins, Sanquin Research and Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, 1006 AD Amsterdam, PO Box 9190, The Netherlands.
5
Molecular and Clinical Sciences Research Institute, St George's, University of London, London SW18 ORE, UK tcarter@sgul.ac.uk.

Abstract

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.

KEYWORDS:

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

PMID:
30659119
DOI:
10.1242/jcs.221952

Conflict of interest statement

Competing interestsThe authors declare no competing or financial interests.

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