Bcl-2 prevents loss of mitochondria in CCCP-induced apoptosis.
Bcl-2 family proteins regulate apoptosis at the level of mitochondria. To examine the mechanism of Bcl-2 function, we investigated the effects of the protonophore carbonyl cyanide m-chlorophenyl hydrazone (CCCP) on two hematopoietic cell lines and Bcl-2 overexpressing transfectants. CCCP directly interferes with mitochondrial function and induces apoptosis. We show that Bcl-2 inhibits apoptosis and that the antiapoptotic effect of Bcl-2 takes place upstream of caspase activation and nuclear changes associated with apoptosis, since these were markedly inhibited in cells overexpressing Bcl-2. Bcl-2 does not prevent the decrease in mitochondrial membrane potential nor the alterations in cellular ATP content induced by CCCP in FL5.12 and Jurkat cells. A higher number of mitochondria was observed in untreated Bcl-2 transfected cells compared to parental cells, as shown by electron microscopy. Exposure to CCCP induced a dramatic decrease in the number of mitochondria and severely disrupted mitochondrial ultrastructure, with apparent swelling and loss of cristae in parental cells. Bcl-2 clearly diminished the disruption of mitochondrial structure and preserved a higher number of mitochondria. These data suggest that CCCP induces apoptosis by structural disruption of mitochondria and that Bcl-2 prevents apoptosis and mitochondrial degeneration by preserving mitochondrial integrity.
de Graaf
Aniek O
AO
Central Hematology Laboratory, Department of Hematology, University Medical Center Nijmegen, Nijmegen 6500 HB, The Netherlands.
van den Heuvel
Lambert P
LP
Dijkman
Henry B P M
HB
de Abreu
Ronney A
RA
Birkenkamp
Kim U
KU
de Witte
Theo
T
van der Reijden
Bert A
BA
Smeitink
Jan A M
JA
Jansen
Joop H
JH
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology*; D020169:Caspases / Q000378:metabolism; D002467:Cell Nucleus; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D019169:Jurkat Cells; D016393:Lymphoma, B-Cell / Q000378:metabolism / Q000473:pathology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
D019253:Proto-Oncogene Proteins c-bcl-2; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000255:Adenosine Triphosphate; D020169:Caspases