In Friedreich ataxia iron-sulfur clusters are not formed, due to deficiencies in frataxin which results in iron accumulation in mitochondria. The relevant point is that problems in iron-sulfur cluster formation can be associated with iron accumulation in mitochondria and iron toxicity. The point I have been making is that there are difficulties in synthesizing iron-sulfur clusters in many neurological illnesses due to dysregulation of the transsulfuration pathway which synthesizes L-cysteine. L-cysteine supplies sulfur for iron-sulfur cluster formation.
Iron chelators are now being investigated as treatments for Alzheimer’s disease and Parkinson’s disease. If iron is being accumulated in cells in Alzheimer’s disease and Parkinson’s disease due to difficulties in iron-sulfur cluster formation then iron chelators would not be appropriate treatments. Iron-sulfur cluster formation is increased by supplemental iron. Iron chelators by decreasing iron would decrease iron–sulfur cluster formation leading to iron accumulation in mitochondria and iron toxicity.