p38 MAPK activation and mitochondrial depolarization mediate the cytotoxicity of Taiwan cobra phospholipase A2 on human neuroblastoma SK-N-SH cells.
Modification of catalytic residue His-47 with p-bromophenacyl bromide (BPB) abolished the enzymatic activity of Naja naja atra phospholipase A2 (PLA2). Additionally, alterations in the global structure and the spatial positions of Trp residues were noted in His-modified PLA2. The cell viability of human neuroblastoma SK-N-SH cells was decreased by approximately 40% and 20% after treatment with 10 microM PLA2 and BPB-PLA2, respectively. Native and His-modified PLA2 induced a necrotic cell death accompanied with an activation of p38 MAPK, the loss of mitochondrial membrane potential (DeltaPsim) and cytochrome c release. Pretreatment with SB202190 (p38 MAPK inhibitor) and cyclosporine A (inhibitor of mitochondria permeability transition pore) rescued cell viability, DeltaPsim and cytochrome c release of PLA2-treated cells. Taken together, our data indicate that PLA2 activity does not play an indispensable role on the cytotoxicity of N. naja atra PLA2, and suggest a novel function of secretory PLA2 in inducing cell death of neuroblastoma. Moreover, the reduced cytotoxicity noted with BPB-PLA2 may be partly attributed to conformational distortion after modification of His-47.
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.
Kao
Pei-Hsiu
PH
Lin
Shinne-Ren
SR
Chang
Long-Sen
LS
D000818:Animals; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D004546:Elapid Venoms / Q000737:chemistry / Q000633:toxicity*; D017815:Elapidae; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D009336:Necrosis / Q000139:chemically induced; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D064801:Phospholipase A2 Inhibitors; D054467:Phospholipases A2 / Q000737:chemistry / Q000633:toxicity*; D011725:Pyridines / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000096:biosynthesis*
D004546:Elapid Venoms; D004791:Enzyme Inhibitors; D007093:Imidazoles; D064801:Phospholipase A2 Inhibitors; D011725:Pyridines; D045304:Cytochromes c; D048051:p38 Mitogen-Activated Protein Kinases; D054467:Phospholipases A2; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole