A role for cell polarity in lifespan and mitochondrial quality control in the budding yeast Saccharomyces cerevisiae

Babies are born young, largely independent of the age of their mothers. Mother-daughter age asymmetry in yeast is achieved, in part, by inheritance of higher-functioning mitochondria by daughter cells and retention of some high-functioning mitochondria in mother cells. The mitochondrial F-box protein, Mfb1p, tethers mitochondria at both poles in a cell cycle-regulated manner: it localizes to and anchors mitochondria to the mother cell tip throughout the cell cycle, and to the bud tip prior to cytokinesis. Here, we report that cell polarity and polarized localization of Mfb1p decline with age in S. cerevisiae. Moreover, deletion of BUD1/RSR1, a Ras protein required for cytoskeletal polarization during asymmetric yeast cell division, results in depolarized Mfb1p localization, defects in mitochondrial distribution and quality control, and reduced replicative lifespan. Our results demonstrate a role for the polarity machinery in lifespan through modulating Mfb1 function in asymmetric inheritance of mitochondria during yeast cell division.