Role of Smac in cephalostatin-induced cell death.
Cephalostatin 1 is a natural compound isolated from a marine worm that induces apoptosis in tumor cells via an apoptosome-independent but caspase-9-dependent pathway and through an endoplasmic reticulum stress response that is accompanied by caspase-4 activation. Here, we show that cephalostatin evokes mitochondrial Smac (second mitochondria-derived activator of caspases) but not cytochrome c release in various carcinoma cell lines. We also show that Smac is critically involved in caspase-9 activation as evidenced by gene silencing experiments. Remarkably, caspase-2 appears to be a major target for cephalostatin-induced cytosolic Smac. Using biochemical and genetic inhibition experiments, we demonstrate that caspase-2 participates in the apoptotic machinery induced by cephalostatin. Cephalostatin-activated caspase-2 appears to act as initiator caspase and is not involved in the activation of caspase-9. Importantly, experiments immunoprecipitating PIDD (p53-induced protein with a DD), RAIDD (RIP-associated ICH-1/CED-3-homologous protein with DD) and caspase-2 identify cephalostatin as an experimental drug that induces the formation of the PIDDosome. The bis-steroid cephalostatin proves to be both a helpful tool to investigate apoptotic signaling and a promising chemotherapeutic agent.
Rudy
A
A
Department of Pharmacy, Center for Drug Research, University of Munich, Munich, Germany.
López-Antón
N
N
Barth
N
N
Pettit
G R
GR
Dirsch
V M
VM
Schulze-Osthoff
K
K
Rehm
M
M
Prehn
J H M
JH
Vogler
M
M
Fulda
S
S
Vollmar
A M
AM
D051017:Apoptosis Regulatory Proteins; D002154:Calpain / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D053143:Caspase 2 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D053418:Death Domain Receptor Signaling Adaptor Proteins; D004789:Enzyme Activation / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D019169:Jurkat Cells; D024101:Mitochondrial Proteins / Q000378:metabolism*; D010619:Phenazines / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013141:Spiro Compounds / Q000494:pharmacology*; D013256:Steroids / Q000494:pharmacology*
D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; C412403:DIABLO protein, human; D053418:Death Domain Receptor Signaling Adaptor Proteins; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; C485896:PIDD1 protein, human; D010619:Phenazines; D019253:Proto-Oncogene Proteins c-bcl-2; D013141:Spiro Compounds; D013256:Steroids; C454806:cephalostatin I; D045304:Cytochromes c; D048031:JNK Mitogen-Activated Protein Kinases; D002154:Calpain; D053143:Caspase 2; D053453:Caspase 9