A novel enhancer of the Apaf1 apoptosome involved in cytochrome c-dependent caspase activation and apoptosis

J Biol Chem. 2001 Mar 23;276(12):9239-45. doi: 10.1074/jbc.M006309200. Epub 2000 Dec 11.

Abstract

Apaf1/CED4 family members play central roles in apoptosis regulation as activators of caspase family cell death proteases. These proteins contain a nucleotide-binding (NB) self-oligomerization domain and a caspase recruitment domain (CARD). A novel human protein was identified, NAC, that contains an NB domain and CARD. The CARD of NAC interacts selectively with the CARD domain of Apaf1, a caspase-activating protein that couples mitochondria-released cytochrome c (cyt-c) to activation of cytosolic caspases. Cyt-c-mediated activation of caspases in cytosolic extracts and in cells is enhanced by overexpressing NAC and inhibited by reducing NAC using antisense/DNAzymes. Furthermore, association of NAC with Apaf1 is cyt c-inducible, resulting in a mega-complex (>1 MDa) containing both NAC and Apaf1 and correlating with enhanced recruitment and proteolytic processing of pro-caspase-9. NAC also collaborates with Apaf1 in inducing caspase activation and apoptosis in intact cells, whereas fragments of NAC representing only the CARD or NB domain suppress Apaf1-dependent apoptosis induction. NAC expression in vivo is associated with terminal differentiation of short lived cells in epithelia and some other tissues. The ability of NAC to enhance Apaf1-apoptosome function reveals a novel paradigm for apoptosis regulation.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Apoptosis*
  • Apoptotic Protease-Activating Factor 1
  • Base Sequence
  • Caspases / metabolism*
  • Cell Line
  • Cytochrome c Group / metabolism*
  • DNA Primers
  • Enhancer Elements, Genetic*
  • Enzyme Activation
  • Humans
  • Immunohistochemistry
  • Molecular Sequence Data
  • Proteins / genetics*
  • Sequence Homology, Amino Acid

Substances

  • APAF1 protein, human
  • Apoptotic Protease-Activating Factor 1
  • Cytochrome c Group
  • DNA Primers
  • Proteins
  • Caspases