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Oligomerization and activation of caspase-9, induced by Apaf-1 CARD

Eric N Shiozaki1, Jijie Chai, Yigong Shi

  • 1Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ 08544, USA.

Proceedings of the National Academy of Sciences of the United States of America
|March 21, 2002
PubMed

Insights

Apoptotic protease activating factor 1 (Apaf-1) enhances caspase-9 activity by forming a complex. This Apaf-1 caspase recruitment domain (CARD) interaction allosterically up-regulates caspase-9, crucial for apoptosis regulation.

Area of Science:

  • Molecular biology
  • Cellular apoptosis
  • Protein-protein interactions

Background:

  • Apoptotic protease activating factor 1 (Apaf-1) is known to facilitate procaspase-9 activation and maintain its hyperactive state.
  • The precise molecular mechanisms governing Apaf-1's role in caspase-9 regulation are not fully understood.

Purpose of the Study:

  • To elucidate the molecular mechanisms by which Apaf-1 regulates caspase-9 activity.
  • To investigate the structural basis for the interaction between Apaf-1 and caspase-9.

Main Methods:

  • Formation and characterization of a hetero-oligomeric complex between the isolated Apaf-1 caspase recruitment domain (CARD) and active caspase-9.
  • Assessment of caspase-9 catalytic activity within the Apaf-1 CARD-caspase-9 complex.
  • Utilized point mutations to disrupt Apaf-1 CARD and caspase-9 prodomain interactions.

Main Results:

  • The Apaf-1 CARD forms a large hetero-oligomer with active caspase-9.
  • Caspase-9 catalytic activity is significantly enhanced within this complex, indicating allosteric up-regulation by Apaf-1 CARD.
  • Disruption of Apaf-1 CARD and caspase-9 prodomain interactions abolished complex formation.

Conclusions:

  • The Apaf-1 CARD allosterically up-regulates caspase-9 activity through direct interaction.
  • This Apaf-1 CARD-caspase-9 complex formation is critical for Apaf-1's function in apoptosis.
  • Findings provide mechanistic insight into Apaf-1's role in initiating the apoptotic cascade.

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