Molecular determinants of the caspase-promoting activity of Smac/DIABLO and its role in the death receptor pathway.
Smac/DIABLO is a mitochondrial protein that is released along with cytochrome c during apoptosis and promotes cytochrome c-dependent caspase activation by neutralizing inhibitor of apoptosis proteins (IAPs). We provide evidence that Smac/DIABLO functions at the levels of both the Apaf-1-caspase-9 apoptosome and effector caspases. The N terminus of Smac/DIABLO is absolutely required for its ability to interact with the baculovirus IAP repeat (BIR3) of XIAP and to promote cytochrome c-dependent caspase activation. However, it is less critical for its ability to interact with BIR1/BIR2 of XIAP and to promote the activity of the effector caspases. Consistent with the ability of Smac/DIABLO to function at the level of the effector caspases, expression of a cytosolic Smac/DIABLO in Type II cells allowed TRAIL to bypass Bcl-xL inhibition of death receptor-induced apoptosis. Combined, these data suggest that Smac/DIABLO plays a critical role in neutralizing IAP inhibition of the effector caspases in the death receptor pathway of Type II cells.
Srinivasula
S M
SM
Center for Apoptosis Research and the Department of Microbiology and Immunology, Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Datta
P
P
Fan
X J
XJ
Fernandes-Alnemri
T
T
Huang
Z
Z
Alnemri
E S
ES
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002454:Cell Differentiation; D003600:Cytosol / Q000737:chemistry; D004789:Enzyme Activation; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D019476:Insect Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D053221:TNF-Related Apoptosis-Inducing Ligand; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D051636:X-Linked Inhibitor of Apoptosis Protein; D051020:bcl-X Protein
D051017:Apoptosis Regulatory Proteins; C494811:BCL2L1 protein, human; D001426:Bacterial Proteins; D002352:Carrier Proteins; D061945:Caspase Inhibitors; C412403:DIABLO protein, human; D051034:Inhibitor of Apoptosis Proteins; D019476:Insect Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D051020:bcl-X Protein; D020169:Caspases