Bcl-2 prevents CD95 (Fas/APO-1)-induced degradation of lamin B and poly(ADP-ribose) polymerase and restores the NF-kappaB signaling pathway.
In the study presented here, we investigated the possible interactions between CD95 (Fas/APO-1) and Bcl-2 by studying the effects of Bcl-2 on the modulation of cellular pathways activated by CD95 using HeLa cells as a model system. We report that stable expression of Bcl-2 in HeLa cells is associated with multiple phenotypic changes. Treatment of HeLa cells with anti-CD95 monoclonal antibody (mAb) resulted in preferential degradation of lamin B compared with lamins A and C. Significant lamin B degradation was detected as early as 1 h after anti-CD95 mAb treatment. In contrast, lamins A and C as well as actin remained unchanged until 4 h after treatment with anti-CD95 mAb, a time point that correlated with the period of DNA fragmentation. These results indicate that selective degradation of lamin B is an early cellular event in response to activation of the CD95 pathway and that it precedes DNA fragmentation. Overexpression of Bcl-2 resulted in prevention of lamin B degradation and DNA fragmentation into oligonucleosome fragments in response to the apoptotic signal by anti-CD95 mAb. In addition, in Bcl-2-overexpressing cells that were protected against apoptosis, anti-CD95 mAb-induced cleavage of poly(ADP-ribose) polymerase was completely blocked. Overexpression of Bcl-2 also resulted in restoration of the CD95-mediated signaling pathway involving activation of the transcription factor NF-kappaB (p50/RelA). These findings suggest that Bcl-2 prevents apoptosis in part by preventing the degradation of major nuclear polypeptides such as lamin B and poly(ADP-ribose) polymerase. In addition, our results demonstrate that CD95-mediated signaling involves activation of NF-kappaB (p50/RelA).
Mandal
M
M
Department of Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Maggirwar
S B
SB
Sharma
N
N
Kaufmann
S H
SH
Sun
S C
SC
Kumar
R
R
D017209:Apoptosis; D002467:Cell Nucleus / Q000378:metabolism; D053938:DNA Fragmentation; D006367:HeLa Cells; D006801:Humans; D034921:Lamin Type B; D034882:Lamins; D016328:NF-kappa B / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D015398:Signal Transduction; D051841:Transcription Factor RelB; D014157:Transcription Factors; D019014:fas Receptor / Q000502:physiology*
D034921:Lamin Type B; D034882:Lamins; D016328:NF-kappa B; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C497593:RELB protein, human; D014157:Transcription Factors; D019014:fas Receptor; D051841:Transcription Factor RelB; D011065:Poly(ADP-ribose) Polymerases