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

Cookson, Emma A and Conte, Ianina L and Dempster, John and Hannah, Matthew J and Carter, Tom (2013) Characterisation of Weibel-Palade body fusion by amperometry in endothelial cells reveals fusion pore dynamics and the effect of cholesterol on exocytosis. Journal of Cell Science, 126 (Pt 23). pp. 5490-5499. ISSN 0021-9533

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Abstract

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.