The three-dimensional structure of caspase-8: an initiator enzyme in apoptosis

• Published in: Structure (London) Vol. 7; no. 9; pp. 1125 - 1133
• Main Authors: Blanchard, Helen, Kodandapani, Lalitha, Mittl, Peer RE, Marco, Stefania Di, Krebs, Joseph F, Wu, Joe C, Tomaselli, Kevin J, Grütter, Markus G
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.09.1999
• Subjects: Amino Acid Sequence; Apoptosis - physiology; Binding Sites; Caspase 8; Caspase 9; Caspase Inhibitors; caspases; Caspases - chemistry; Caspases - metabolism; Crystallography, X-Ray; Dimerization; drug design; inhibitor binding; Models, Molecular; Molecular Sequence Data; Oligopeptides - chemistry; Oligopeptides - metabolism; Protease Inhibitors - chemistry; Protease Inhibitors - metabolism; Protein Conformation; Protein Structure, Quaternary; structure comparison; Substrate Specificity; X-ray structure; inhibitor binding; drug design; structure comparison; caspases; X-ray structure
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/S0969-2126(99)80179-8

Background: In the initial stages of Fas-mediated apoptosis the cysteine protease caspase-8 is recruited to the cell receptor as a zymogen (procaspase-8) and is incorporated into the death-signalling complex. Procaspase-8 is subsequently activated leading to a cascade of proteolytic events, one of them being the activation of caspase-3, and ultimately resulting in cell destruction. Variations in the substrate specificity of different caspases have been reported. Results: We report here the crystal structure of a complex of the activated human caspase-8 (proteolytic domain) with the irreversible peptidic inhibitor Z-Glu-Val-Asp-dichloromethylketone at 2.8 Å resolution. This is the first structure of a representative of the long prodomain initiator caspases and of the group III substrate specificity class. The overall protein architecture resembles the caspase-1 and caspase-3 folds, but shows distinct structural differences in regions forming the active site. In particular, differences observed in subsites S 3, S 4 and the loops involved in inhibitor interactions explain the preference of caspase-8 for substrates with the sequence (Leu/Val)-Glu-X-Asp. Conclusions: The structural differences could be correlated with the observed substrate specificities of caspase-1, caspase-3 and caspase-8, as determined from kinetic experiments. This information will help us to understand the role of the various caspases in the propagation of the apoptotic signal. The information gained from this investigation should be useful for the design of specific inhibitors.