Fig. 1
From: Mitochondrial heterogeneity: subpopulations with distinct metabolic activities
Mitochondrial fusion and fission enable formation of mitochondrial subcompartments. Middle panel: Under conditions of high oxidative phosphorylation (OXPHOS) distinct populations of mitochondria are formed dependent on mitochondrial fusion and fission. One mitochondrial subpopulation contains cristae and the F1FO-ATP synthase, whereas a second population lacks cristae and contains filaments of the enzyme delta-1-pyrroline-5 carboxylate synthase (P5CS) required for proline and ornithine synthesis. The presence of two distinct mitochondrial subpopulations allows conversion of glutamate to an intermediate of the tricarboxylic acid (TCA) cycle to power ATP production via OXPHOS and the metabolization of glutamate via P5CS for reductive biosynthesis of proline and ornithine in the same cell. Left panel: Impaired mitochondrial fission results in network expansion and prevents separation of F1FO-ATP synthase and P5CS into distinct mitochondrial populations. As a consequence, increased oxidative utilization of glutamate impairs the metabolization of glutamate for biosynthesis of proline and ornithine. Right panel: Impaired fusion prevents the exchange of mitochondrial content, resulting in fragmented mitochondria containing reduced levels of the F1FO-ATP synthase. In these mitochondria, OXPHOS activity is reduced, while biosynthesis of proline and ornithine is unaffected
