Figure 4.

Frataxin overexpression or knockdown has no effect on GRP75 protein levels. HEK293 cells transfected with frataxin plasmid DNA or siRNA were lysed and subjected to western blotting with the indicated antibodies. The amount of immunoreactivity in the lysates was quantified as a percentage of vector or siRNA control. No change in GRP75 was found in cells transfected with frataxin-HA in comparison with vector control (A and B) (n = 6; P > 0.05). While frataxin knockdown resulted in 40% and 22% residual frataxin at 3 and 5 days, respectively, no decrease in GRP75 was observed at either condition (C and D) (n = 8, P > 0.05 for 3 days and n = 4, P > 0.05 for 5 days). Similar results were noted in human skin fibroblasts with frataxin siRNA leading to 56% and 11% residual frataxin at 3 and 5 days, respectively (E and F) (n = 4, P > 0.05 for both 3 and 5 days) ^**P < 0.01. Data were shown as mean ± SE.