Fig. 3 presents the average amperometric spikes and statistical analysis for different experimental conditions. As expected, in the empty vector-expressing cells, PMA increased the speed of pore expansion as evidenced by the steeper amperometric rising phase. In contrast, such PMA-induced acceleration was absent from the
SCH 527123 expressing dn-PKCα; i.e., dn-PKCα, just like BIS, is able to abolish this PMA effect. This observation suggests the minor involvement of other PMA targets and the importance of PKCα activation in this phenomenon. Also similar to the BIS effect demonstrated in Fig. 1, over-expression of dn-PKCα without PMA did not affect the slope of the rising phase. Therefore, basal PKCα activities are probably not critically involved in normal fusion pore opening. The observations that over-expression of wt-PKCα gave a sharper rise in the amperometric signal, and that PMA could not further strengthen
endochondral ossification effect in wt-PKCα over-expressing cells, suggest that the abundance of PKCα, but not that of DAG, is the limiting factor in activating the acceleration mechanism for fusion.
