Properties of the fusion pore that forms during exocytosis of a mast cell secretory vesicle

Secretion machinery at the cell plasma membrane

“…During cell secretion, the fusion pore either irreversibly expands or closes [24,[29][30][31]. The latter process, where the fusion pore opens allowing secretory vesicles to fuse momentarily and subsequently close, has been referred to as 'transient fusion' [24,26,30,31]. Experimental data from these and other studies, and from theoretical considerations, gave rise to a hypothetical working model of the exocytotic fusion pore [29,32] in cells.…”

“…Electrophysiological measurements of mast cells [23][24][25][26][27] as well as adrenal chromaffin cells [28], suggested the presence of fusion pores at the cell plasma membrane as "dynamic entities", originating following a secretory stimulus [29]. Results from earlier studies on cell capacitance and conductance measurements, suggested that following stimulation of secretion, the "exocytotic fusion pore" abruptly appears as a 1-2 nm in diameter pore at the cell plasma membrane, with conductance similar to a large ion channel [29].…”

In search of the fusion pore of exocytosis

“…For a larger fusion pore of about the size seen with a dense-core vesicle, 1 nm, the concentration just barely reaches the critical 1 mM level, and for a 2 nm fusion pore, which is a size only seen after quite a bit of expansion [37,38], the concentration surpasses that estimated from experiment. With a fusion pore this large the transmitter decay time constant works out to ~0.5 ms, so the steady-state approximation starts to break down.…”

Local electrostatic interactions determine the diameter of fusion pores

“…G p was used to estimate the fusion-pore radius by using the equation G p D (pr 2 )/(rl), where r denotes the fusion-pore radius, r is the estimated resistivity of the saline (100 Vcm) and l is the estimated length of a gap junction channel (15 nm). 46 SigmaPlot was used for the statistical analyses. Values are presented as mean § SEM.…”