Figure 6

Differential regulation of frataxin in neurons and astrocytes. A large difference was appreciated between neurons and astrocytes in levels of frataxin mRNA (A) and protein (B). C, Inhibition of protein synthesis with cycloheximide (1 μg/ml) for 48 hours, unveils a longer half life of frataxin in astrocytes than in neurons (time effect by ANOVA: F=5.32). D, Addition of IGF-I (100 nM, 10 hours) to proteasome-inhibited cells (10μM of MG-132) resulted in an increase in frataxin levels in neurons but not in astrocytes. Representative blot are shown for B,C and D; the upper blots correspond to frataxin and the lower blots to β-actin (n=3-4, independent experiments). *p<0.05; **p<0.01.