Journal
JOURNAL OF CELL SCIENCE
Volume 132, Issue 5, Pages -Publisher
COMPANY BIOLOGISTS LTD
DOI: 10.1242/jcs.221952
Keywords
Endothelial; Synaptotagmin; Weibel-Palade body; Exocytosis; Ca2+; Secretion
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Funding
- UK Medical Research Council (MRC) [MC_PC_13053]
- St George's University London PhD studentship
- European Hematology Association Research Fellowship
- Landsteiner Foundation for Blood Transfusion Research [LSBR-1707]
- MRC [MC_PC_13053] Funding Source: UKRI
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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.
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