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Functional Import of Exogenous Mature Cytochrome c into Mitochondria of Deficient Cells
Author(s) -
Levy Richard J,
Huang Zhishan,
Edwards John G,
Gao Qun,
Wolin Michael S
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1017.6
Subject(s) - cytochrome c , mitochondrion , apoptosis , tunel assay , oxidative phosphorylation , cytochrome , microbiology and biotechnology , biology , null cell , apoptosome , respiration , biochemistry , chemistry , programmed cell death , caspase , enzyme , anatomy , gene
Cytochrome c (cyt c), the electron carrier between Complexes III and IV, is required for oxidative phosphorylation. It is believed that only the immature form of the protein is imported into mitochondria. Here we test the hypothesis that exogenous mature cyt c can be functionally imported. Cyt c null cells (cyt c −/−) and control fibroblasts (NIH/3T3) were exposed to cyt c, acetylated cyt c, or buffer for 2 hours. Immunoblot analysis demonstrated markedly increased cyt c levels in mitochondria of cyt c exposed null and 3T3 cells. Following exposure to FITC‐conjugated cyt c, green punctate fluorescence was readily visualized in both cell types and co‐localized with MitoTracker Red. Using electron microscopy, gold particles were clearly seen within mitochondria and endosomes of null and 3T3 cells following exposure to either gold‐conjugated cyt c or acetylated cyt c. Cyt c‐dependent respiration was significantly decreased in null cells exposed to buffer or acetylated cyt c and increased following exposure to exogenous cyt c approaching 3T3 rates. The percentage of TUNEL positive nuclei was similar between groups. Exogenous cyt c readily entered the intact cell via endocytosis and was imported into mitochondria without initiating apoptosis. This import increased null cell cyt c‐dependent respiration. This may have important implications for the treatment of acquired and inherited mitochondrial disorders.