Role of caspases and possible involvement of retinoblastoma protein during TGFbeta-mediated apoptosis of human B lymphocytes.
In this study, we investigated the involvement of caspases in TGFbeta-induced apoptosis in human B cells. Our results show that TGFbeta-mediated nuclear fragmentation, observed in the Epstein-Barr virus-negative Burkitt's Lymphoma cell line BL41, was abolished in the presence of the tripeptide caspase inhibitor zVAD-fmk or the specific caspase-3 inhibitor DEVD-fmk. Other apoptotic manifestations such as cell shrinkage, surface phosphatidylserine expression and chromatin condensation were strongly inhibited by zVAD-fmk but only partially by DEVD-fmk. This suggests that other caspases in addition to caspase-3 control these apoptotis-associated features. Specific activation of caspase-3 during TGFbeta-induced apoptosis was demonstrated by the DEVD-fmk-sensitive expression of the active p17 subunit of caspase-3 and by in vivo cleavage of PARP. In addition, TGFbeta treatment of BL41 promoted the expression of both dephosphorylated and truncated forms of the retinoblastoma protein. Inhibition of caspase-3 activity abolished both nuclear fragmentation and expression of the truncated retinoblastoma protein, without modifying the G1 cell cycle arrest induced by TGFbeta. Our data thus demonstrate that TGFbeta-induced apoptosis of lymphoma B lymphocytes is dependent on caspase activation and involves caspase-dependent cleavage of the retinoblastoma protein.
Schrantz
N
N
INSERM U.131-IPSC, Clamart, France.
Blanchard
D A
DA
Auffredou
M T
MT
Sharma
S
S
Leca
G
G
Vazquez
A
A
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001402:B-Lymphocytes / Q000502:physiology*; D002051:Burkitt Lymphoma / Q000473:pathology / Q000503:physiopathology; D053143:Caspase 2; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053938:DNA Fragmentation; D004789:Enzyme Activation; D006801:Humans; D009842:Oligopeptides / Q000494:pharmacology; D011506:Proteins; D016160:Retinoblastoma Protein / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000502:physiology*; D014407:Tumor Cells, Cultured
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; D011506:Proteins; D016160:Retinoblastoma Protein; D016212:Transforming Growth Factor beta; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C505407:CASP3 protein, human; D053143:Caspase 2; D053148:Caspase 3; D020169:Caspases