Kiss-and-run exocytosis and fusion pores of secretory vesicles in human β-cells
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Exocytosis of secretory vesicles results in the release of insulin from pancreatic β-cells, although little is known about this process in humans. We examined the exocytosis of single secretory vesicles and their associated fusion pores in human β-cells by cell-attached capacitance and conductance measurement. Unitary capacitance steps were observed, consistent with the exocytosis of single secretory vesicles. These were often coincident with increases in patch conductance representing the presence of a stable fusion pore. In some events, the fusion pore closed, mediating kiss-and-run, which contributed 20% of the exocytotic events. The cAMP-raising agent forskolin (5 μM) doubled the relative contribution of kiss-and-run. This effect was confirmed visually in MIN6 cells expressing a fluorescent granule probe. Thus, we demonstrate the unitary capacitance steps and fusion pores during single vesicle exocytosis in human β-cells. Furthermore, these secretory vesicles can undergo rapid recycling by kiss-and-run, and this process is up-regulated by cAMP.
KeywordsExocytosis Pancreatic β-cell Capacitance Insulin release cAMP
We thank Mrs. Nancy Smith for technical assistance. This work was supported by grants to PEM from the Canadian Institutes of Health Research (MOP 81350), the Canada Foundation for Innovation, and the Alberta Heritage Foundation for Medical Research (AHFMR). Work in Oxford was supported by the Wellcome Trust UK. PEM is an AHFMR and Canadian Diabetes Association Scholar and holds the Canada Research Chair in Islet Biology.
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