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. 2006 Sep 13;399(Pt 1):111–119. doi: 10.1042/BJ20060654

Figure 5. Activation or inhibition of conventional PKC shifts the mode of granule fusion.

Figure 5

Cells were stimulated at 0.5 Hz or 15 Hz in 2.8 mM Ca2+ under conditions in which PKC activity was pharmacologically blocked or activated. Top panel: analysis of evoked rates of catecholamine release (initial spike slope) are provided for all conditions. Pretreatment of cells with PMA increased the rate of catecholamine release measured under 0.5 Hz stimulation to that measured under 15 Hz stimulation, while inhibition of PKC with Gö 6983 and Ro-31-8220 (pooled together as ‘PKC Inh.’) acted to decrease the 15 Hz-evoked rate of catecholamine release to that measured under 0.5 Hz. Sample numbers from left to right (number of spikes/number of cells): 1301/15, 821/13, 209/4, 2819/14, 3940/20. Middle panel: endocytic uptake of fluorescent 40 kDa dextran was measured and normalized to the number of amperometric spikes for each condition. Dye uptake was blocked by inhibition of PKC. In all other conditions, dye was internalized equally efficiently on an ‘all-or-none’ basis when normalized to the number of release events. Sample numbers from left to right (n=cells) 18, 10, 9, 13, 18. Bottom panel: capacitance variance measured under control, PKC-blocked and PKC-activated conditions. As in Figure 3, dotted lines represent variance values from smooth (σ2cell) and Ω-figure-decorated (σ2cell+Ω) membranes. Cell variance was higher under 0.5 Hz than 15 Hz stimulation. A block of PKC under 0.5 Hz stimulation had no effect on variance. A block of PKC under 15 Hz stimulation raised cell variance to the level of 0.5 Hz control conditions. Pre-treatment of cells with PMA and stimulation at 0.5 Hz resulted in decreased variance matching the 15 Hz control condition. Sample numbers for these data were from left to right (n=cells) 19, 36, 15, 13, 58. Control data are re-plotted from previously shown Figures. Summary cartoon: taken together, all three techniques predict that granule fusion occurs through a ‘kiss and run’ mechanism under modest Ca2+ influx, or when PKC is inactive.