Oscillatory behavior is known to occur in many different biological settings. Some examples are the circadian rhythms, the mitotic oscillator, oscillations in cyclic AMP in Dictyostelium cells, and oscillations in free calcium in numerous types of cells (1). In addition, many metabolic processes are known to oscillate (2–7). The best-known metabolic oscillator is probably glycolysis in the yeast strain Saccharomyces cerevisiae, but oscillating glycolysis is also found in other cells, e.g., muscle cells and pancreatic b–cells (3). Mitochondria are best known for their role in energy metabolism. However, it has recently becomeclear that mitochondria serve many other functions in the cell. In some cells, e.g., neutrophils, the mitochondria are responsible only for a minor part of theATPproduction. Instead, it appears that these organelles participate in calcium homeostasis and in apoptosis (8–10). In pancreatic b-cells, the mitochondria serve an important role in the regulation of insulin production, in addition to providing the cells with ATP. Glycolytic oscillations in b-cells are in part regulated by the mitochondria. The resulting oscillations in ATP in turn regulate ion channels in the plasma membrane, generating an oscillating membrane potential, which again controls oscillations in cytoplasmic free calcium and the release of insulin (11). Recently, we reported a similar coupling between an oscillating glycolysis in S. cerevisiae and mitochondrial membrane potential (Dcm) (12,13). It is not yet known whether it is the same coupling that is responsible for other oscillations involving mitochondria, e.g., the synchronized oscillations observed in respiration of S. cerevisiae in continuous culture (14–16). Under those circumstances, mitochondrial function seems to regulate a number of cellular processes, because it was shown that the majority of metabolites in the cells show oscillatory dynamics with 70% of the identified metabolites peaking in conjunction with nicotinamide adenine dinucleotide (NAD(P)H) (17).
Updated on July 22, 2020