Blockage of K+ efflux Suppresses Staurosporine Induced Apoptosis by Preventing the Formation of the Apaf-1 Apoptosome and the Downstream Pathways

다국어 초록 (Multilingual Abstract)

Upon apoptotic insult cell loses intracelluar K+ and blockage of the efflux by K+ channel blockers or the high concentration of extracelluar K+ suppresses the apoptosis. The suppression of staurosporine induced apoptosis by the blockage was not relieved by inhibitors of protein kinase C, phosphatidylinositol 3-kinase and others. Furthermore, the release of cytochrome C from the mitochondria was neither significantly changed with the blockage of the efflux. Whereas processing of procaspase-9, -3, -8 and other death related proteins completely disappeared with the blockage. Importantly, the blockage of K+ efflux prevented the formation of the apoptosome, a multiprotein complex consisting of cytochrome C, Apaf-1, dATP and caspase-9. Consistently, the formation of the apoptosome induced by dATP and cytochrome C in the cell free system was also significantly inhibited by 150 mM KCl, the normal physiological K+ level. The same concentration of KCl inhibited in different extents processing of procaspase-3 by caspase-8 or 9, nucleosomal DNA fragmentation by purified DFF40/CAD and nuclear fragmentation. Taken together, these results strongly suggest that the protective effect of K+ on the staurosporine-induced apoptosis occurs mainly at a site of the apoptosome formation and this effect seems to be augmented by the inhibition of downstream apoptotic pathways.