Oxidized or Reduced Cytochrome c and Axial Ligand Variants All Form the Apoptosome in Vitro

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Cytochrome c (cyt c) is crucial for both mitochondrial electron transport and initiating apoptosis.
• During apoptosis, cyt c translocates to the cytosol to form the apoptosome with Apaf-1.
• The redox state of cyt c required for apoptosome formation has been debated.

Purpose of the Study:

• To investigate the role of cytochrome c redox state in apoptosome formation and apoptosis.
• To determine if oxidized (ferri) or reduced (ferro) cyt c is necessary for initiating cell death signaling.

Main Methods:

• Utilized a recombinant system for synthesizing human cyt c variants.
• Employed a panel of cyt c axial ligand variants with diverse redox potentials.
• Assessed the binding of different cyt c redox states to Apaf-1 and apoptosome assembly.

Main Results:

• Wild-type cyt c, reduced cyt c (H19M), and oxidized cyt c variants (M81A, M81H) all successfully bind to Apaf-1.
• All tested cyt c variants, regardless of redox state, induce the formation of the apoptosome.

Conclusions:

• The redox state of cytochrome c does not prevent its interaction with Apaf-1 or apoptosome formation.
• Both oxidized and reduced forms of cyt c can participate in initiating the intrinsic apoptosis pathway.