The role of proline uptake in yeast mitochondria and the feast-famine regime

Research over the last decade has extended the prevailing view of cell mitochondrial function well beyond its bioenergetic role in supplying ATP, recognizing that the mitochondria play a critical role in the responses of cells to metabolic transition and physiological stresses. Although proline is the least-preferred nitrogen source for many laboratory yeast strains and its utilisation results in the slowest growth rates, yeast cells have evolved a regulatory circuit that enables them to use the proline in the environment when preferred nitrogen sources are no longer available. Preliminary studies on wild-type Saccharomyces cerevisiae ATCC 18790 and two strains found in grape must show the capability of yeast mitochondria to take up and oxidise L-proline externally added them. Proline causes mitochondrial membrane potential (ΔΨ) generation with a rate proved to depend on the transport across the mitochondrial membrane as is shown by means of inhibitors N-ethylmaleimide and bathophenanthroline. The dependence of the rate of generation of ΔΨ on the increasing proline concentrations exhibits hyperbolic kinetics. Differently from mammalians and plants, as a results of proline addition, the appearance of glutamate was not found outside yeast mitochondria as measured by HPLC experiments and by GDH detecting system. Proline mitochondrial metabolism in the response to metabolic transition respect to environmental “ feast” and “famine” conditions will be, also, debated. PDF created