Taiwan cobra phospholipase A2-elicited JNK activation is responsible for autocrine fas-mediated cell death and modulating Bcl-2 and Bax protein expression in human leukemia K562 cells.
Phospholipase A(2) (PLA(2)) from Naja naja atra venom induced apoptotic death of human leukemia K562 cells. Degradation of procaspases, production of tBid, loss of mitochondrial membrane potential, Bcl-2 degradation, mitochondrial translocation of Bax, and cytochrome c release were observed in PLA(2)-treated cells. Moreover, PLA(2) treatment increased Fas and FasL protein expression. Upon exposure to PLA(2), activation of p38 MAPK (mitogen-activated protein kinase) and JNK (c-Jun NH(2)-terminal kinase) was found in K562 cells. SB202190 (p38 MAPK inhibitor) pretreatment enhanced cytotoxic effect of PLA(2) and led to prolonged JNK activation, but failed to affect PLA(2)-induced upregulation of Fas and FasL protein expression. Sustained JNK activation aggravated caspase8/mitochondria-dependent death pathway, downregulated Bcl-2 expression and increased mitochondrial translocation of Bax. SP600125 (JNK inhibitor) abolished the cytotoxic effect of PLA(2) and PLA(2)-induced autocrine Fas death pathway. Transfection ASK1 siRNA and overexpression of dominant negative p38alpha MAPK proved that ASK1 pathway was responsible for PLA(2)-induced p38 MAPK and JNK activation and p38alpha MAPK activation suppressed dynamically persistent JNK activation. Downregulation of FADD abolished PLA(2)-induced procaspase-8 degradation and rescued viability of PLA(2)-treated cells. Taken together, our results indicate that JNK-mediated autocrine Fas/FasL apoptotic mechanism and modulation of Bcl-2 family proteins are involved in PLA(2)-induced death of K562 cells.
Chen
Ku-Chung
KC
Institute of Biomedical Sciences, National Sun Yat-Sen University-Kaohsiung Medical University Joint Research Center, National Sun Yat-Sen University, Kaohsiung 804, Taiwan.
Liu
Wen-Hsin
WH
Chang
Long-Sen
LS
D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D002469:Cell Separation; D002470:Cell Survival / Q000187:drug effects; D004546:Elapid Venoms / Q000201:enzymology / Q000494:pharmacology; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053222:Fas Ligand Protein / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D020014:K562 Cells; D007938:Leukemia / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D054467:Phospholipases A2 / Q000378:metabolism* / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D051028:bcl-2-Associated X Protein / Q000096:biosynthesis*; D019014:fas Receptor / Q000378:metabolism
D004546:Elapid Venoms; D004791:Enzyme Inhibitors; D053222:Fas Ligand Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D019014:fas Receptor; D048670:MAP Kinase Kinase 4; D054467:Phospholipases A2