Cytochrome c as a distinct modulator of amyloid-beta amyloidogenesis in a peroxide-dependent manner

Cytochrome c (Cyt c) is an important, multifunctional protein for controlling cell fate. Emerging evidence suggests a potential role of Cyt c in the amyloid pathology associated with Alzheimer’s disease (AD); however, the interaction between Cyt c and Abeta with the consequent impact on the aggregation and toxicity of Abeta is not known. Here we report the discovery that Cyt c can directly bind to Abeta and alter the aggregation and toxicity profiles of Abeta in a peroxide-dependent manner. Cyt c redirects Abeta peptides into less toxic, off-pathway amorphous aggregates in the presence of hydrogen peroxide (H2O2), whereas it accelerates Abeta fibrillization without H2O2. Such effects can be achieved by three possible mechanisms, including the complexation between Cyt c and Abeta, the oxidation of Abeta by Cyt c and H2O2, and the H2O2-mediated modification of Cyt c. Our studies demonstrate a new function of Cyt c as a modulator against Abeta amyloidogenesis.