Cephalostatin 1 selectively triggers the release of Smac/DIABLO and subsequent apoptosis that is characterized by an increased density of the mitochondrial matrix.

Abstract

Cephalostatin 1 is a bis-steroidal marine natural product with a unique cytotoxicity profile in the in vitro screen system of the National Cancer Institute, suggesting that it may affect novel molecular target(s). Here we show that cephalostatin 1 induces a novel pathway of receptor-independent apoptosis that selectively uses Smac/DIABLO (second mitochondria-derived activator of caspases/direct inhibitor of apoptosis-binding protein with a low isoelectric point) as a mitochondrial signaling molecule. At nanomolar concentrations, cephalostatin 1 triggers dose- and time-dependent DNA fragmentation in leukemia Jurkat T cells. Apoptosis was found to be dependent on caspase activity because the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone blocks cephalostatin 1-mediated DNA fragmentation. The CD95 death receptor as well as other caspase-8-requiring death receptors were not involved because Jurkat T cells lacking the CD95 receptor or caspase-8 and control cells responded equally to cephalostatin 1. Although cephalostatin 1 affects mitochondria by dissipating the mitochondrial membrane potential, neither cytochrome c nor apoptosis-inducing factor is released, as shown by Western blot analysis. Interestingly, cephalostatin 1 selectively triggers the mitochondrial release of the inhibitor of apoptosis antagonist Smac/DIABLO. Overexpression of the antiapoptotic protein Bcl-x(L) delayed both Smac/DIABLO release and onset of apoptosis, suggesting that Smac/DIABLO is required for cephalostatin 1-induced apoptosis. This new mitochondrial pathway is accompanied by marked structural changes of mitochondria as shown by transmission electron microscopy.

• Authors: Verena M Dirsch, Irina M Müller, Sören T Eichhorst, George R Pettit, Yoshiaki Kamano, Masuo Inoue, Jun-Ping Xu, Yoshitatsu Ichihara, Gerhard Wanner, Angelika M Vollmar
• Journal: Cancer research (Cancer Res) Vol. 63 Issue 24 Pg. 8869-76 (Dec 15 2003) ISSN: 0008-5472 [Print] United States
• PMID: 14695204 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• APAF1 protein, human
• Apoptosis Regulatory Proteins
• Apoptotic Protease-Activating Factor 1
• BCL2L1 protein, human
• Carrier Proteins
• DIABLO protein, human
• Intracellular Signaling Peptides and Proteins
• Mitochondrial Proteins
• Phenazines
• Proteins
• Proto-Oncogene Proteins c-bcl-2
• Spiro Compounds
• Steroids
• X-Linked Inhibitor of Apoptosis Protein
• XIAP protein, human
• bcl-X Protein
• cephalostatin I
• CASP8 protein, human
• CASP9 protein, human
• Caspase 8
• Caspase 9
• Caspases

Topics

• Apoptosis (drug effects, physiology)
• Apoptosis Regulatory Proteins
• Apoptotic Protease-Activating Factor 1
• Carrier Proteins (metabolism, physiology)
• Caspase 8
• Caspase 9
• Caspases (metabolism)
• Cell Membrane Permeability (drug effects)
• Humans
• Intracellular Membranes (drug effects, metabolism)
• Intracellular Signaling Peptides and Proteins
• Jurkat Cells
• Leukemia, T-Cell (drug therapy, enzymology, pathology)
• Mitochondria (drug effects, metabolism)
• Mitochondrial Proteins (metabolism, physiology)
• Phenazines (pharmacology)
• Proteins (metabolism)
• Proto-Oncogene Proteins c-bcl-2 (biosynthesis)
• Spiro Compounds (pharmacology)
• Steroids
• X-Linked Inhibitor of Apoptosis Protein
• bcl-X Protein