FIGURE 5: COX4-1 overexpression promotes SC assembly in radiosensitive GBM cells. (A) Representative Western blot showing COX4-1 expression in U251 and D456 cells stably transfected with vector only or vector expressing COX4-1. Citrate synthase (CS) served as the loading control. (B) Quantification of CcO activity in vector control- and COX4-1-transfected U251 and D456 cells. Data are presented as the mean ± SEM (n=4). (C) Digitonin-solubilized mitochondria from the indicated cell lines were subjected to BN-PAGE followed by in-gel complex I and IV activity assays and complex III Western blot analysis. Representative images from 3 separate experiments. p < 0.0001 (****), calculated by Student t-test.