Calcium-Stimulated Mitogen-Activated Protein Kinase Activation Elicits Bcl-xL Downregulation and Bak Upregulation in Notexin-Treated Human Neuroblastoma SK-N-SH Cells

Notechis scutatus scutatus notexin induced apoptotic death of SK-N-SH cells accompanied with downregulation of Bcl-xL, upregulation of Bak, mitochondrial depolarization, and ROS generation. Upon exposure to notexin, Ca2+-mediated JNK and p38 MAPK activation were observed in SK-N-SH cells. Production of ROS was a downstream event followed by Ca2+-mediated mitochondrial alteration. Notexin-induced cell death, mitochondrial depolarization, and ROS generation were suppressed by SB202190 (p38 MAPK inhibitor) and SP600125 (JNK inhibitor). Moreover, phospho-p38 MAPK and phospho-JNK were proved to be involved in Bcl-xL degradation, and overexpression of Bcl-xL attenuated the cytotoxic effect of notexin. Bak upregulation was elicited by p38 MAPK-mediated ATF-2 activation and JNK-mediated c-Jun activation. Suppression of Bak upregulation by ATF-2 siRNA or c-Jun siRNA attenuated notexin-evoked mitochondrial depolarization and rescued viability of notexin-treated cells. Taken together, our data indicate that notexin-induced apoptotic death of SK-N-SH cells is mediated through mitochondrial alteration triggering by Ca2+-evoked p38 MAPK/ATF-2 and JNK/c-Jun signaling pathways. J. Cell. Physiol. 222: 177-186, 2010. (C) 2009 Wiley-Liss, Inc.