Bigenomic regulation of cytochrome c oxidase in neurons and the tight coupling between neuronal activity and energy metabolism.
Cytochrome c oxidase is the terminal enzyme of the mitochondrial electron transport chain, without which oxidative metabolism cannot be carried to completion. It is one of only four unique, bigenomic proteins in mammalian cells. The holoenzyme is made up of three mitochondrial-encoded and ten nuclear-encoded subunits in a 1:1 stoichiometry. The ten nuclear subunit genes are located in nine different chromosomes. The coordinated regulation of such a multisubunit, multichromosomal, bigenomic enzyme poses a challenge. It is especially so for neurons, whose mitochondria are widely distributed in extensive dendritic and axonal processes, resulting in the separation of the mitochondrial from the nuclear genome by great distances. Neuronal activity dictates COX activity that reflects protein amount, which, in turn, is regulated at the transcriptional level. All 13 COX transcripts are up- and downregulated by neuronal activity. The ten nuclear COX transcripts and those for Tfam and Tfbms important for mitochondrial COX transcripts are transcribed in the same transcription factory. Bigenomic regulation of all 13 transcripts is mediated by nuclear respiratory factors 1 and 2 (NRF-1 and NRF-2). NRF-1, in addition, also regulates critical neurochemicals of glutamatergic synaptic transmission, thereby ensuring the tight coupling of energy metabolism and neuronal activity at the molecular level in neurons.
Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA. mwr@mcw.edu
Margaret T T
MT
Wong-Riley
D000818:Animals; D003576:Electron Transport Complex IV / Q000502:physiology*; D004734:Energy Metabolism; D051268:GA-Binding Protein Transcription Factor / Q000502:physiology; D018698:Glutamic Acid / Q000502:physiology; D006801:Humans; D009474:Neurons / Q000201:enzymology / Q000502:physiology*; D051266:Nuclear Respiratory Factor 1 / Q000502:physiology; D014158:Transcription, Genetic
D051268:GA-Binding Protein Transcription Factor; D051266:Nuclear Respiratory Factor 1; D018698:Glutamic Acid; D003576:Electron Transport Complex IV