title: Inhibition of CED-3 zymogen activation and apoptosis in Caenorhabditis elegans by caspase homolog CSP-3.
abstract: Inhibitor of apoptosis (IAP) proteins have a crucial role in apoptosis, through negative regulation of caspases in species from fruitflies to mammals. In Caenorhabditis elegans, however, no IAP homolog or caspase inhibitor has been identified, calling into question how the cell-killing caspase CED-3 can be negatively regulated. Here we show that inactivation of the C. elegans csp-3 gene, which encodes a protein similar to the small subunit of the CED-3 caspase, causes cells that normally live to undergo apoptosis in a CED-3-dependent manner. Biochemical analysis reveals that CSP-3 associates with the large subunit of the CED-3 zymogen and inhibits zymogen autoactivation. However, CSP-3 does not block CED-3 activation induced by CED-4, nor does it inhibit the activity of the activated CED-3 protease. Therefore CSP-3 uses a previously unreported mechanism to protect cells from apoptosis.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Campus Box 347, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Geng
authors.forename: Yong
authors.initials: Y
authors.lastname: Shi
authors.forename: Akihisa
authors.initials: A
authors.lastname: Nakagawa
authors.forename: Sawako
authors.initials: S
authors.lastname: Yoshina
authors.forename: Shohei
authors.initials: S
authors.lastname: Mitani
authors.forename: Yigong
authors.initials: Y
authors.lastname: Shi
authors.forename: Ding
authors.initials: D
authors.lastname: Xue
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D017173:Caenorhabditis elegans / Q000166:cytology* / Q000196:embryology / Q000201:enzymology* / Q000254:growth & development; D029742:Caenorhabditis elegans Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D061945:Caspase Inhibitors; D020169:Caspases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D004789:Enzyme Activation; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D029742:Caenorhabditis elegans Proteins; D061945:Caspase Inhibitors; D021122:Protein Subunits; D020169:Caspases; C089223:ced-3 protein, C elegans; C116783:csp-3 protein, C elegans
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