Exp Mol Med.  2006 Aug;38(4):435-444.

Up-regulation of Bax and endonuclease G, and down-modulation of Bcl-X(L) involved in cardiotoxin III-induced apoptosis in K562 cells

• Yang SH
• Chien CM
• Lu MC
• Lin YH
• Hu XW
• Lin SR

Abstract

Cardiotoxin III (CTX III), a basic polypeptide with 60 amino acid residues isolated from Naja naja atra venom, has been reported to have anticancer activity. CTX III-induced K562 cell apoptosis was confirmed by DNA fragmentation (DNA ladder, sub-G1 formation) and phosphatidylserine (PS) externalization with an IC50 value of 1.7 mug/ml at 48 h. A mechanistic analysis demonstrated that CTX III-induced apoptotic cell death was accompanied by up-regulation of both Bax and endonuclease G (Endo G), and downregulation of Bcl-X(L). CTX III had no effect on the levels of Bcl-2, Bid, XIAP survivin, and AIF proteins. CTX III treatment caused loss of the mitochondrial membrane potential (delta psi m), release of mitochondrial cytochrome c to the cytosol, and activation of both caspase-9 and -3. CTX III-induced apoptosis was significantly blocked by the broad-spectrum caspase inhibitor Z-VAD-FMK. However, CTX III did not generate reactive oxygen species (ROS) and antioxidants, including N-acetylcysteine and catalase, did not block CTX III-induced apoptosis in K562 cells. Modulation of Bax, Bcl-X(L), and the Endo G proteins, release of mitochondrial cytochome c, and activation of caspase-3 and -9 all are involved in the CTX III-triggered apoptotic process in human leukemia K562 cells.

Keyword

apoptosis; bcl-2-associated X protein; cardiotoxin III, Naja naja atra; caspase; endonuclease G; K562 cells

MeSH Terms

bcl-X Protein/*metabolism
bcl-2-Associated X Protein/*metabolism
Up-Regulation/drug effects
Reactive Oxygen Species/metabolism
Mitochondrial Proteins/metabolism
Mitochondrial Membranes/drug effects
Membrane Potentials/drug effects
K562 Cells
Inhibitor of Apoptosis Proteins/metabolism
Humans
Endodeoxyribonucleases/*metabolism
Down-Regulation/drug effects
Direct Lytic Factors/*pharmacology
Cytochromes c/metabolism
Cell Proliferation/drug effects
Caspases/metabolism
Apoptosis/*drug effects