Nuclear respiratory factor 1 (NRF-1) is a transcriptional activator of nuclear genes that encode a range of mitochondrial proteins including cytochrome c, various other respiratory chain subunits, and d-aminolevulinate synthase. Activation of NRF-1 in fibroblasts has been shown to induce increases in cytochrome c expression and mitochondrial respiratory capacity. To further evaluate the role of NRF-1 in the regulation of mitochondrial biogenesis and respiratory capacity, we generated transgenic mice overexpressing NRF-1 in skeletal muscle. Cytochrome c expression was increased ~twofold and d-aminolevulinate synthase was increased ~50% in NRF-1 transgenic muscle. The levels of some mitochondrial proteins were increased 50–60%, while others were unchanged. Muscle respiratory capacity was not increased in the NRF-1 transgenic mice. A finding that provides new insight regarding the role of NRF-1 was that expression of MEF2A and GLUT4 was increased in NRF-1 transgenic muscle. The increase in GLUT4 was associated with a proportional increase in insulin-stimulated glucose transport. These results show that an isolated increase in NRF-1 is not sufficient to bring about a coordinated increase in expression of all of the proteins necessary for assembly of functional mitochondria. They also provide the new information that NRF-1 overexpression results in increased expression of GLUT4.—Baar, K., Song, Z., Semenkovich, C. F., Jones, T. E,. Han, D.-H., Nolte, L. A., Ojuka, E. O., Chen, M., Holloszy, J. O. Skeletal muscle overexpression of nuclear respiratory factor 1 increases glucose transport capacity.
- Respiratory enzymes
- Cytochrome c
- Protein synthesis
Baar, K., Song, Z., Semenkovich, C. F., Jones, T. E., Han, D-H., Nolte, L. A., Ojuka, E. O., Chen, M., & Holloszy, J. O. (2003). Skeletal muscle overexpression of nuclear respiratory factor 1 increases glucose transport capacity. FASEB Journal, 17(12), 1666-1673. https://doi.org/10.1096/fj.03-0049com