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J Cell Sci. 2013 Dec 1;126(Pt 23):5490-9. doi: 10.1242/jcs.138438. Epub 2013 Oct 14.

Characterisation of Weibel-Palade body fusion by amperometry in endothelial cells reveals fusion pore dynamics and the effect of cholesterol on exocytosis.

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MRC National Institute for Medical Research, Mill Hill, London, NW7 1AA, UK.


Regulated secretion from endothelial cells is mediated by Weibel-Palade body (WPB) exocytosis. Plasma membrane cholesterol is implicated in regulating secretory granule exocytosis and fusion pore dynamics; however, its role in modulating WPB exocytosis is not clear. To address this we combined high-resolution electrochemical analysis of WPB fusion pore dynamics, by amperometry, with high-speed optical imaging of WPB exocytosis following cholesterol depletion or supplementation in human umbilical vein endothelial cells. We identified serotonin (5-HT) immunoreactivity in WPBs, and VMAT1 expression allowing detection of secreted 5-HT as discrete current spikes during exocytosis. A high proportion of spikes (∼75%) had pre-spike foot signals, indicating that WPB fusion proceeds via an initial narrow pore. Cholesterol depletion significantly reduced pre-spike foot signal duration and increased the rate of fusion pore expansion, whereas cholesterol supplementation had broadly the reverse effect. Cholesterol depletion slowed the onset of hormone-evoked WPB exocytosis, whereas its supplementation increased the rate of WPB exocytosis and hormone-evoked proregion secretion. Our results provide the first analysis of WPB fusion pore dynamics and highlight an important role for cholesterol in the regulation of WPB exocytosis.


Amperometry; Endothelial cell; Exocytosis; Serotonin; VMAT1; Weibel–Palade bodies

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