title: Insights into the regulatory mechanism for caspase-8 activation.
abstract: In the death receptor induced apoptotic pathway, caspase-8 autocatalytically cleaves itself at specific cleavage sites. To better understand the regulatory mechanisms behind caspase-8 activation, we compared active wild-type caspase-8 (wtC8) and an uncleavable form of procaspase-8 (uncleavable C8). We demonstrate that wtC8 predominantly exists as a monomer and dimerizes in a concentration and inhibitor binding-dependent fashion. The K(D) for dimeric wtC8 is approximately 50 micro M and decreases when inhibitor bound. Uncleavable C8 is mainly monomeric, but a small amount that dimerizes is as active as wtC8. Inhibitor binding does not favor dimerization but induces active site rearrangements in uncleavable C8. Our findings suggest that dimerization is the crucial factor for caspase-8 activation.
authors.affiliation: Biochemistry Institute, University of Zürich, 8057-, Zürich, Switzerland.
authors.forename: Mrudula
authors.initials: M
authors.lastname: Donepudi
authors.forename: Aengus
authors.initials: A
authors.lastname: Mac Sweeney
authors.forename: Christophe
authors.initials: C
authors.lastname: Briand
authors.forename: Markus G
authors.initials: MG
authors.lastname: Grütter
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000378:metabolism; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism; D019281:Dimerization; D004789:Enzyme Activation; D066298:In Vitro Techniques; D007700:Kinetics; D008954:Models, Biological; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; D011994:Recombinant Proteins; C430228:acetyl-aspartyl-glutamyl-valyl-lysine chloromethyl ketone; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases