Interdimer processing mechanism of procaspase-8 activation.
The execution of apoptosis depends on the hierarchical activation of caspases. The initiator procaspases become autoproteolytically activated through a less understood process that is triggered by oligomerization. Procaspase-8, an initiator caspase recruited to death receptors, is activated through two cleavage events that proceed in a defined order to generate the large and small subunits of the mature protease. Here we show that dimerization of procaspase-8 produces enzymatically competent precursors through the stable homophilic interaction of the procaspase-8 protease domain. These dimers are also more susceptible to processing than individual procaspase-8 molecules, which leads to their cross-cleavage. The order of the two interdimer cleavage events is maintained by a sequential accessibility mechanism: the separation of the large and small subunits renders the region between the large subunit and prodomain susceptible to further cleavage. In addition, the activation process involves an alteration in the enzymatic properties of caspase-8; while procaspase-8 molecules specifically process one another, mature caspases only cleave effector caspases. These results reveal the key steps leading to the activation of procaspase-8 by oligomerization.
Chang
David W
DW
Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Xing
Zheng
Z
Capacio
Vanessa L
VL
Peter
Marcus E
ME
Yang
Xiaolu
X
D017209:Apoptosis; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002460:Cell Line; D019281:Dimerization; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D008954:Models, Biological; D008958:Models, Molecular; D017354:Point Mutation; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
D004792:Enzyme Precursors; D011993:Recombinant Fusion Proteins; D019014:fas Receptor; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases