Fig. 7. Knockdown of Drp1 affects MTP18-induced mitochondrial fission. (A) HeLa cells were co-transfected with an shRNA-Drp1 expression plasmid for RNAi and with an MTP18-myc expression vector. The resulting knockdown of Drp1 together with overexpression of MTP18-mycis was shown by western blotting. No changes in protein levels were detected for hFis1 and Mfn1. Cells were treated with nocodazole and stained with anti-MTP18 (green) to show recombinant MTP18-myc overexpressing cells (arrows indicate representative examples) and anti-cytochrome c (red) to show mitochondrial morphology. Mitochondria show highly fused morphology (merged picture and high magnification, two panels on right) due to RNAi-induced reduction of Drp1 in cells with endogenous levels of MTP18 (double-arrow; not detectable with anti-MTP18) as well as in cells with high levels of MTP18-myc (arrow).