title: Molecular determinants of caspase-9 activation by the Apaf-1 apoptosome.
abstract: Autocatalytic activation of an initiator caspase triggers the onset of apoptosis. In dying cells, caspase-9 activation is mediated by a multimeric adaptor complex known as the Apaf-1 apoptosome. The molecular mechanism by which caspase-9 is activated by the Apaf-1 apoptosome remains largely unknown. Here we demonstrate that the previously reported 1:1 interaction between Apaf-1 caspase recruitment domain (CARD) and caspase-9 CARD is insufficient for the activation of caspase-9. Rather, formation of a multimeric CARD:CARD assembly between Apaf-1 and caspase-9, which requires three types of distinct interfaces, underlies caspase-9 activation. Importantly, an additional surface area on the multimeric CARD assembly is essential for caspase-9 activation. Together, these findings reveal mechanistic insights into the activation of caspase-9 by the Apaf-1 apoptosome and support the induced conformation model for initiator caspase activation by adaptor complexes.
authors.affiliation: Ministry of Education Protein Science Laboratory, Center for Structural Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China; and.
authors.forename: Qi
authors.initials: Q
authors.lastname: Hu
authors.affiliation: Ministry of Education Protein Science Laboratory, Center for Structural Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China; and.
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.affiliation: Ministry of Education Protein Science Laboratory, Center for Structural Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China; and.
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
authors.affiliation: Ministry of Education Protein Science Laboratory, Center for Structural Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China; and.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yan
authors.affiliation: Ministry of Education Protein Science Laboratory, Center for Structural Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China; and.
authors.forename: Chuangye
authors.initials: C
authors.lastname: Yan
authors.affiliation: Department of Chemistry, Tsinghua University, Beijing 100084, China.
authors.forename: Tianxi
authors.initials: T
authors.lastname: He
authors.affiliation: Department of Chemistry, Tsinghua University, Beijing 100084, China.
authors.forename: Qionglin
authors.initials: Q
authors.lastname: Liang
authors.affiliation: Ministry of Education Protein Science Laboratory, Center for Structural Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China; and shi-lab@tsinghua.edu.cn.
authors.forename: Yigong
authors.initials: Y
authors.lastname: Shi
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D053478:Apoptosomes / Q000378:metabolism*; D053453:Caspase 9 / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D004789:Enzyme Activation; D006801:Humans; D006860:Hydrogen Bonding; D066298:In Vitro Techniques; D008239:Lysine / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: C573917:APIP protein, human; D051017:Apoptosis Regulatory Proteins; D053478:Apoptosomes; D011993:Recombinant Fusion Proteins; C506433:CASP9 protein, human; D053453:Caspase 9; D008239:Lysine
keywords: CARD; apoptosis; caspase activation; induced proximity; mechanism