Overexpression of bcl-2 results in reduction of cytochrome c content and inhibition of complex I activity.
Bcl-2 has been shown to exert its antiapoptotic activity predominantly at the level of mitochondria by preventing cytochrome c release. Whether Bcl-2 is involved in the regulation of mitochondrial function prior to an apoptotic stimulus remains elusive. Using functional and spectrophotometric measurements in an inducible PC12-Tet-on-bcl-2 cell line we demonstrate that induction of Bcl-2 overexpression rapidly reduced cytochrome b and c levels as well as complex I activity. To confirm that these changes were specific for Bcl-2 we generated a bcl-2 antisense construct under the control of the tetracycline responsive promotor. Transient transfection with this antisense plasmid prevented both the decrease of cytochrome b and c levels and the loss of complex I activity. The decrease of cytochrome b levels was paralleled by a decrease of cytochrome b mRNA levels while Northern blot analysis of cytochrome c mRNA expression did not reveal any overt changes in Bcl-2 cells. We propose that the antiapoptotic properties of Bcl-2 are related to the reduction of mitochondrial complex I activity and lowered mitochondrial cytochrome b and c levels.
Schwarz
C S
CS
Department of Neurology, Department of Epileptology, University of Bonn, Sigmund-Freud-Str. 25, Bonn, D-53105, Germany.
Evert
B O
BO
Seyfried
J
J
Schaupp
M
M
Kunz
W S
WS
Vielhaber
S
S
Klockgether
T
T
Wüllner
U
U
D000818:Animals; D017209:Apoptosis; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D002950:Citrate (si)-Synthase / Q000378:metabolism; D003573:Cytochrome b Group / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D042967:Electron Transport Complex I; D009245:NADH Dehydrogenase / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D016716:PC12 Cells; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D013053:Spectrophotometry; D013347:Subcellular Fractions / Q000378:metabolism; D013752:Tetracycline / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
D003573:Cytochrome b Group; D003574:Cytochrome c Group; D016376:Oligonucleotides, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D009247:NADH, NADPH Oxidoreductases; D009245:NADH Dehydrogenase; D002950:Citrate (si)-Synthase; D042967:Electron Transport Complex I; D013752:Tetracycline