(a) Wild-type (Mfn2+/+) and Mfn2 knockout (Mfn2-/-) MEFs stably expressing mCherry-Parkin were incubated in the absence or presence of CCCP (30 μM) for 4 h, fixed, permeabilized and subjected to immunofluorescence analysis with antibodies to FKBP38 and to cytochrome c. The fluorescence of mCherry-Parkin was also monitored directly. 