Alpha-synuclein ferrireductase activity is detectible in vivo, is altered in Parkinson's disease and increases the neurotoxicity of DOPAL

The normal cellular role of alpha-synuclein is of potential importance in understanding diseases in which an aggregated form of the protein has been implicated. A potential loss or change in the normal function of alpha-synuclein could play a role in the aetiology of diseases such as Parkinson's disease. Recently, it has been suggested that alpha-synuclein could cause the enzymatic reduction of iron and a cellular increase in Fe(II) levels. Experiments were carried out to determine if such activity could be measured in vivo. Experiments with rats overexpressing human alpha-synuclein in nigral dopaminergic neurons demonstrated a correlation between alpha-synuclein expression and ferrireductase activity. Furthermore, studies on tissue from Parkinson's disease patient brains showed a significant decrease in ferrireductase activity, possibly due to deposition of large amounts of inactive protein. Cellular studies suggest that increase ferrireductase activity results in increased levels of dopamine metabolites and increased sensitivity to the toxicity of DOPAL. These findings demonstrate that alpha-synuclein ferrireductase activity is present in vivo and its alteration may play a role in neuron loss in disease.