Increased IRP1 activity in Friedreich ataxia.

In low-iron conditions, the cytosolic iron-regulatory protein IRP1 binds to iron-responsive elements (IREs) in mRNAs encoding iron-regulated proteins. In high-iron conditions, IRP1 incorporates an iron-sulfur cluster (ISC), which interferes with IRE binding and prevents intracellular iron accumulation. Here we demonstrate an incomplete shift of IRP1 to its ISC form in Friedreich ataxia (FRDA) fibroblasts, associated with decreased activities of ISC respiratory complexes. Our data suggest an impaired adaptive response to iron accumulation in FRDA cells.