PLA2 activity is required for nuclear shrinkage in caspase-independent cell death.
Apoptosis is defined on the basis of morphological changes like nuclear fragmentation and chromatin condensation, which are dependent on caspases. Many forms of caspase-independent cell death have been reported, but the mechanisms are still poorly understood. We found that hypoxic cell death was independent of caspases and was associated with significant nuclear shrinkage. Neither Bcl-2 nor Apaf-1 deficiency prevented hypoxic nuclear shrinkage. To understand the molecular mechanism of the nuclear shrinkage, we developed an in vitro system using permeabilized cells, which allowed us to purify a novel member of the phospholipase A2 (PLA2) family that induced nuclear shrinkage. Purified PLA2 induced nuclear shrinkage in our permeabilized cell system. PLA2 inhibitors prevented hypoxic nuclear shrinkage in cells and cell death. Hypoxia caused elevation of PLA2 activity and translocation of intracellular PLA2s to the nucleus. Knockdown of the Ca2+-independent PLA2 delayed nuclear shrinkage and cell death. These results indicate that Ca2+-independent PLA2 is crucial for a caspase-independent cell death signaling pathway leading to nuclear shrinkage.
Shinzawa
Koei
K
Laboratory of Molecular Genetics, Department of Post-Genomics and Diseases, Osaka University Medical School, Yamadaoka, Suita, Osaka 565-0871, Japan.
Tsujimoto
Yoshihide
Y
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D053477:Apoptotic Protease-Activating Factor 1; D020013:Calcium Signaling / Q000502:physiology; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology*; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D054522:Group VI Phospholipases A2; D006367:HeLa Cells; D006801:Humans; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016716:PC12 Cells; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D054467:Phospholipases A2; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015854:Up-Regulation / Q000502:physiology
C506592:APAF1 protein, human; C506594:Apaf1 protein, rat; D053477:Apoptotic Protease-Activating Factor 1; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D010741:Phospholipases A; D054522:Group VI Phospholipases A2; C516475:PLA2G6 protein, human; D054467:Phospholipases A2; D020169:Caspases