Alpha-synuclein mitochondrial interaction leads to irreversible translocation and complex I impairment

alpha-synuclein is involved in both familial and sporadic Parkinson's disease. Although its interaction with mitochondria has been well documented, several aspects remains unknown or under debate such as the specific sub-mitochondrial localization or the dynamics of the interaction. It has been suggested that alpha-synuclein could only interact with ER-associated mitochondria. The vast use of model systems and experimental conditions makes difficult to compare results and extract definitive conclusions. Here we tackle this by analyzing, in a simplified system, the interaction between purified alpha-synuclein and isolated rat brain mitochondria. This work shows that wild type alpha-synuclein interacts with isolated mitochondria and translocates into the mitochondrial matrix. This interaction and the irreversibility of alpha-synuclein translocation depend on incubation time and alpha-synuclein concentration. FRET experiments show that alpha-synuclein localizes close to components of the TOM complex suggesting a passive transport of alpha-synuclein through the outer membrane. In addition, alpha-synuclein binding alters mitochondrial function at the level of Complex I leading to a decrease in ATP synthesis and an increase of ROS production.