FECH is destabilized by oxygen and mitochondrial oxidative stress. (A) Cells were maintained in normal (21%) or reduced (6%) O2 atmosphere, followed by differentiation by DMSO treatment. FECH activity (B) and protein levels (C) were increased in differentiating MEL cells maintained at 6% O2 relative to 21% O2 cultures. However, FECH mRNA levels (D) in 6% O2 cultures were not greater than those in 21% O2 cultures. (E) ALAS2 protein expression was also elevated in cells cultured in 6% O2 relative to 21% O2 cultures. (F) Hemoglobinization was accelerated in differentiating cells cultured in 6% O2 (20 μg of total protein was loaded). (G) Menadione-induced mitochondrial oxidative stress caused rapid and specific depletion of total cellular FECH protein levels, whereas PPOX, mACO, and SOD2 protein levels were not appreciably altered. Error bars in panel B represent the range of 2 experimental replicates.
