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Large transient assemblies of Apaf1 constitute the apoptosome in cells

Alicia C Borgeaud1,2, Iva Ganeva1,2, Calvin Klein1,3

  • 1Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.

Nature Communications
|October 24, 2025
PubMed

Insights

Apaf1 foci form the apoptosome complex during apoptosis. Their dynamic assembly and disassembly regulate cell death progression, offering new insights into mitochondrial apoptosis.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The apoptosome complex, formed by Apaf1 and cytochrome c, is essential for initiating mitochondrial apoptosis by activating caspases.
  • The in vivo assembly process and structural characteristics of the apoptosome remain poorly understood.

Purpose of the Study:

  • To elucidate the in vivo assembly mechanism and visual characteristics of the apoptosome.
  • To investigate the role of Apaf1 foci in the context of apoptosis.

Main Methods:

  • Cellular imaging to observe Apaf1 localization and foci formation.
  • Biochemical assays to analyze the composition and interactions within Apaf1 foci.
  • Genetic manipulation to assess the dependence on procaspase-9.

Main Results:

  • Apaf1 molecules accumulate into distinct foci within cells upon apoptotic signaling.
  • These Apaf1 foci are organelle-sized, cloud-like structures that interact with cytochrome c and contain caspase-9.
  • The formation of these foci is dependent on procaspase-9 expression, and their disassembly correlates with cell survival.

Conclusions:

  • Apaf1 foci represent the in vivo form of the apoptosome.
  • The transient nature and ultrastructure of Apaf1 foci suggest that dynamic spatiotemporal organization of apoptotic components regulates apoptosis progression.

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