Molecular architecture of the DED chains at the DISC: regulation of procaspase-8 activation by short DED proteins c-FLIP and procaspase-8 prodomain.
The CD95/Fas/APO-1 death-inducing signaling complex (DISC), comprising CD95, FADD, procaspase-8, procaspase-10, and c-FLIP, has a key role in apoptosis induction. Recently, it was demonstrated that procaspase-8 activation is driven by death effector domain (DED) chains at the DISC. Here, we analyzed the molecular architecture of the chains and the role of the short DED proteins in regulating procaspase-8 activation in the chain model. We demonstrate that the DED chains are largely composed of procaspase-8 cleavage products and, in particular, of its prodomain. The DED chain also comprises c-FLIP and procaspase-10 that are present in 10 times lower amounts compared with procaspase-8. We show that short c-FLIP isoforms can inhibit CD95-induced cell death upon overexpression, likely by forming inactive heterodimers with procaspase-8. Furthermore, we have addressed mechanisms of the termination of chain elongation using experimental and mathematical modeling approaches. We show that neither c-FLIP nor procaspase-8 prodomain terminates the DED chain, but rather the dissociation/association rates of procaspase-8 define the stability of the chain and thereby its length. In addition, we provide evidence that procaspase-8 prodomain generated at the DISC constitutes a negative feedback loop in procaspase-8 activation. Overall, these findings provide new insights into caspase-8 activation in DED chains and apoptosis initiation.
Division of Immunogenetics, German Cancer Research Center (DKFZ), Heidelberg, Germany.
K
K
Schleich
Department of Translational Inflammation Research, Institute of Experimental Internal Medicine, Otto von Guericke University, Magdeburg, Germany.
J H
JH
Buchbinder
Department of Translational Inflammation Research, Institute of Experimental Internal Medicine, Otto von Guericke University, Magdeburg, Germany.
S
S
Pietkiewicz
Institute of Experimental Internal Medicine, Otto von Guericke University, Magdeburg, Germany.
T
T
Kähne
Functional Proteome Analysis, German Cancer Research Center (DKFZ), Heidelberg, Germany.
U
U
Warnken
Division of Immunogenetics, German Cancer Research Center (DKFZ), Heidelberg, Germany.
S
S
Öztürk
Functional Proteome Analysis, German Cancer Research Center (DKFZ), Heidelberg, Germany.
M
M
Schnölzer
Institute of Experimental Internal Medicine, Otto von Guericke University, Magdeburg, Germany.
M
M
Naumann
Division of Immunogenetics, German Cancer Research Center (DKFZ), Heidelberg, Germany.
P H
PH
Krammer
Department of Translational Inflammation Research, Institute of Experimental Internal Medicine, Otto von Guericke University, Magdeburg, Germany.|Novosibirsk Institute of Cytology and Genetics, Novosibirsk, Russia.
I N
IN
Lavrik
D017209:Apoptosis; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics / Q000378:metabolism*; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation / Q000235:genetics; D006801:Humans; D000072417:Protein Domains; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; C491901:FAS protein, human; D019014:fas Receptor; D053181:Caspase 8