FIGURE 6.

Impaired synthesis of ISCU protein renders patient myoblasts and fibroblasts more sensitive to oxidative stress. A, control and patient myoblasts were pulsed with H₂O₂ for 1 h followed by a chase in normal culture medium for 4 or 8 h. ISCU protein levels, mitochondrial aconitase (mACO) and cytosolic aconitase (cACO) activity levels, and IRP-IRE binding activity were measured. B, control and patient myoblasts were also tested for their ability to recover from a 1-h pulse with 1 mm DEA/NO. C, preincubation of primary patient myoblasts with sodium ascorbate (vitamin C) prevented H₂O₂-mediated depletion of ISCU protein. Preincubation with reduced glutathione (GSH) had no effect on ISCU depletion. D, control and patient primary fibroblasts were tested for their ability to recover aconitase activity and IRP-IRE binding activity in a 5% O₂ atmosphere following a 16-h challenge in a 95% O₂/5% CO₂ atmosphere. E, control (Ctl) and patient (Pat) myoblasts expressing either mitochondrial or cytosolic ISCU were grown in a 95% O₂ atmosphere for 16 h followed by recovery at 6% O₂ for 24 h.