Wang 2010 J Biol Chem
| Wang Y, Mohsen AW, Mihalik SJ, Goetzman ES, Vockley J (2010) Evidence for physical association of mitochondrial fatty acid oxidation and oxidative phosphorylation complexes. J Biol Chem 285:29834-41. https://doi.org/10.1074/jbc.M110.139493 |
Wang Y, Mohsen AW, Mihalik SJ, Goetzman ES, Vockley J (2010) J Biol Chem
Abstract: Fatty acid β-oxidation (FAO) and oxidative phosphorylation (OXPHOS) are key pathways involved in cellular energetics. Reducing equivalents from FAO enter OXPHOS at the level of complexes I and III. Genetic disorders of FAO and OXPHOS are among the most frequent inborn errors of metabolism. Patients with deficiencies of either FAO or OXPHOS often show clinical and/or biochemical findings indicative of a disorder of the other pathway. In this study, the physical and functional interactions between these pathways were examined. Extracts of isolated rat liver mitochondria were subjected to blue native polyacrylamide gel electrophoresis (BNGE) to separate OXPHOS complexes and supercomplexes followed by Western blotting using antisera to various FAO enzymes. Extracts were also subjected to sucrose density centrifugation and fractions analyzed by BNGE or enzymatic assays. Several FAO enzymes co-migrated with OXPHOS supercomplexes in different patterns in the gels. When palmitoyl-CoA was added to the sucrose gradient fractions containing OXPHOS supercomplexes in the presence of potassium cyanide, cytochrome c was reduced. Cytochrome c reduction was completely blocked by myxothiazol (a complex III inhibitor) and 3-mercaptopropionate (an inhibitor of the first step of FAO), but was only partially inhibited by rotenone (a complex I inhibitor). Although palmitoyl-CoA and octanoyl-CoA provided reducing equivalents to OXPHOS-containing supercomplex fractions, no accumulation of their intermediates was detected. In contrast, short branched acyl-CoA substrates were not metabolized by OXPHOS-containing supercomplex fractions. These data provide evidence of a multifunctional FAO complex within mitochondria that is physically associated with OXPHOS supercomplexes and promotes metabolic channeling.
• Bioblast editor: Gnaiger E
Selected quotes and comments
Gnaiger E 223-09-10
- Reducing equivalents from FAO enter OXPHOS at the level of complexes I and III.
- Comment: The definition of 'OXPHOS' requires consideration. Appreciating ETF dehydrogenase as an ETS Complex (CETFDH), the correct phrase would be 'Reducing equivalents from FAO enter the membrane-bound ETS at the level of CI and CETFDH'.
- Enoyl-CoA hydratase, l-3-hydroxyacyl-CoA dehydrogenase, and 3-ketoacyl-CoA thiolase have been shown to bind to the inner mitochondrial membrane.
- ETF and ETF dehydrogenase have been shown to form a stable complex, and long chain 3-hydroxyacyl-CoA dehydrogenase has been shown to interact directly with ETC complex I at the inner mitochondria membrane (14,–16).
- ∼25% of fibroblast cultures from patients with complex I deficiency show a concomitant decrease in the ability to oxidize palmitate (36).
- The results confirm that multiple ACADs, their electron acceptor ETF, ETF dehydrogenase, and trifunctional protein all associate with ETC supercomplexes.
- The exception was ETF, which we detected in supercomplex fractions by Western blotting, but was not present in sufficient quantity to drive the bridging assay. With the addition of exogenous ETF, electron flow from palmitoyl-CoA through FAO and the ETC to cytochrome c was very efficient, displaying a Km in the low μm range.
- CPT-2, very long chain ACAD, ACAD9, and trifunctional protein, are membrane-bound proteins (39). In contrast, medium chain ACAD, long chain ACAD, and short chain ACAD are all considered as “soluble” matrix proteins.
Labels:
Organism: Rat
Tissue;cell: Liver
Preparation: Isolated mitochondria
Enzyme: Supercomplex
Regulation: Cyt c, Inhibitor
Pathway: F
