Smac/DIABLO is required for effector caspase activation during apoptosis in human cells.
Mitochondria play a pivotal role during stress-induced apoptosis as several proapoptotic proteins are released to the cytosol to activate caspases. Smac/DIABLO is one of the proapoptotic proteins released from the mitochondria and has been shown to inactivate IAPs. However, gene knockout studies in mice revealed a redundant role for Smac during development and cell death. By applying RNA interference-mediated loss of function approach, we demonstrate that Smac/DIABLO is required for the activation of effector but not initiator caspases during stress and receptor-mediated cell death in HeLa cells. Cells with reduced Smac resist apoptosis and retained clonogenicity. Our results suggest an obligatory role for Smac/DIABLO in these tumor cells during several pathways of apoptosis induction.
Rajalingam
Krishnaraj
K
Department of Molecular Biology, Max Planck Institute for Infection Biology, Charitéplatz 1, 10117, Berlin, Germany.
Oswald
Monique
M
Gottschalk
Kathleen
K
Rudel
Thomas
T
D017209:Apoptosis / Q000235:genetics; D051017:Apoptosis Regulatory Proteins; D020126:Brefeldin A / Q000494:pharmacology; D053470:Caspases, Effector / Q000378:metabolism*; D004789:Enzyme Activation / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000502:physiology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D014162:Transfection
D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D011500:Protein Synthesis Inhibitors; D020126:Brefeldin A; D053470:Caspases, Effector