Cullin3-based polyubiquitination and p62-dependent aggregation of caspase-8 mediate extrinsic apoptosis signaling.
Cell-surface death receptors such as DR4 and DR5 trigger apoptosis through a death-inducing signaling complex (DISC) that recruits the apical protease caspase-8. Apoptosis commitment requires efficient activation and autocatalytic release of caspase-8 into the cytoplasm to engage executioner caspases. While DISC recruitment initiates caspase-8 stimulation, full activation of the protease depends on further molecular aggregation events that are not fully understood. Here, we show that death receptor ligation induces polyubiquitination of caspase-8, through a previously unknown interaction of the DISC with a cullin3 (CUL3)-based E3 ligase. CUL3-mediated caspase-8 polyubiquitination required the RING box protein RBX1, whereas the deubiquitinase A20 reversed this modification. The ubiquitin-binding protein p62/sequestosome-1 promoted aggregation of CUL3-modified caspase-8 within p62-dependent foci, leading to full activation and processing of the enzyme and driving commitment to cell death. These results identify a mechanism that positively controls apoptosis signaling by polyubiquitination and aggregation of a key initiator caspase.
Department of Molecular Oncology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
Zhaoyu
Z
Jin
Yun
Y
Li
Robert
R
Pitti
David
D
Lawrence
Victoria C
VC
Pham
Jennie R
JR
Lill
Avi
A
Ashkenazi
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D017209:Apoptosis; D002352:Carrier Proteins / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism*; D045744:Cell Line, Tumor; D044842:Cullin Proteins / Q000378:metabolism*; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006801:Humans; D021381:Protein Transport; D000071456:Sequestosome-1 Protein; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination
D048868:Adaptor Proteins, Signal Transducing; C503645:CUL3 protein, human; D002352:Carrier Proteins; D044842:Cullin Proteins; D053418:Death Domain Receptor Signaling Adaptor Proteins; C479529:RBX1 protein, human; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D025801:Ubiquitin; D053181:Caspase 8