Mechanism of mitochondrial 7A6 antigen exposure triggered by distinct apoptotic pathways: involvement of caspases.
BACKGROUND
During the early stages of apoptosis, 7A6 antigen is exposed on mitochondria. 7A6 antigen is observed in various cells and is thought to be a specific marker of apoptosis determination. However, the exposure mechanism of 7A6 during apoptosis is poorly understood.


METHODS
In this study, we used two major distinct (mitochondria-mediated and receptor-mediated) apoptotic pathways to elucidate the 7A6 exposure pathway. Jurkat cells were incubated with either a mitochondrial permeability transition pore open reagent FTY720, or anti-Fas antibody. 7A6 exposure was detected with a specific antibody, Apo2.7. Other apoptosis phenomena, including DNA fragmentation, caspase activation, and mitochondrial membrane potential decreases, were also observed to explore the correlation with 7A6 exposure.


RESULTS
Both FTY720 and anti-Fas antibody were found to activate caspase-3 and exposed 7A6, to subsequently fragment DNA. Mitochondrial membrane potential decrease did not correlate to 7A6 exposure. When mitochondrial dysfunction was inhibited by the overexpression of Bcl-2, FTY720-induced 7A6 exposure was blocked, whereas 7A6 was still exposed in anti-Fas antibody treatment. Caspase inhibitor attenuated 7A6 exposure in both apoptotic pathways, suggesting that 7A6 exposure on mitochondria is a downstream effect of caspase activation.


CONCLUSIONS
7A6 antigen is exposed in a caspase-dependent manner. 7A6 exposure does not require mitochondrial perturbation.
Nagahara
Yukitoshi
Y
Department of Biotechnology, College of Science and Engineering, Tokyo Denki University, Hatoyama, Hiki-gun, Saitama 350-0394, Japan. yunagahara@b.dendai.ac.jp
Tanaka
Masato
M
Shinomiya
Takahisa
T
D017209:Apoptosis; D020169:Caspases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism; D053938:DNA Fragmentation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000068876:Fingolimod Hydrochloride; D005434:Flow Cytometry; D006801:Humans; D019169:Jurkat Cells; D008024:Ligands; D053078:Membrane Potential, Mitochondrial; D008565:Membrane Proteins / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D011409:Propylene Glycols / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection
D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D008024:Ligands; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011409:Propylene Glycols; D019253:Proto-Oncogene Proteins c-bcl-2; C102086:antigen 7A6; D020169:Caspases; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine