Organisms acquire damage as they age1, 2. Common traits that are associated in aged cells are the accumulation of protein aggregates, nucleolar abnormalities and dysfunctional organelles2, 3,5. However, it remains difficult to distinguish which traits directly promote cellular aging, versus those that arise as a consequence of aging. Generating a model system that addresses this issue will allow us to develop better therapeutic strategies to combat aging and improve health span. Similar to metazoans, budding yeast accumulates protein aggregates, nucleolar abnormalities and dysfunctional organelles during aging. Surprisingly, as aged yeast cells undergo gametogenesis, the resulting gametes no longer contain the age-associated traits6. Furthermore, the longevity of the gametes is restored by this process, suggesting that elimination of age-associated traits causes cellular rejuvenation6.
I aim to dissect the molecular mechanisms that counteract age-induced damage during gametogenesis and test their impact on lifespan. The experiments in Aim 1 will determine which genes in budding yeast cause gametes to avoid the inheritance of age-associated traits. Analyses so far indicate that cellular contents subject to age-induced damage, including nuclear pore complexes, protein aggregates and the nucleoli, localize to a subcompartment of the nuclear envelope during gametogenesis. This compartment is not inherited by the gametes as they regenerate contents de novo 8, 12. These observations suggest that age-induced traits are associated with the nuclear envelope subcompartment via specific adaptors, which cause their exclusion from the gametes. If true, disruption of each candidate adaptor should lead to retention of a distinct type of age-induced damage. In parallel, an unbiased genetic approach will be taken to screen for mutants that pass on age-induced traits to their gametes30. Further assessment of each mutant by microfluidic pedigree analyses will reveal which traits are limiting for lifespan39. The experiments in Aim 2 will determine how long-lived proteins that accumulate in aged cells are destroyed during budding yeast and C.elegans gametogenesis. Budding yeast gametes do not inherit the vacuole of the progenitor cell, which is ultimately destroyed. When the vacuole lyses, it releases proteases that normally degrade long-lived proteins7, 13, 14. Therefore, inhibiting vacuolar proteases, as well as other factors associated with protein quality control may cause long-lived proteins found in aged cells to persist during gametogenesis. Similar phenomena have been recently reported in the C.elegans germline, which will additionally be explored17, 18. The results will be verified by yeast genetics, worm genetics and fluorescence live-cell imaging. Identifying the genes required to eliminate long-lived proteins will facilitate the generation of new strategies to remove proteotoxic damage.
The proposed research will model how old cellular material is partitioned and destroyed during meiotic differentiation. Determining which genes are necessary to exclude aging markers from budding yeast gametes will distinguish factors that directly cause aging from those that arise as a consequence of aging. Identifying how long-lived proteins are destroyed during gamete maturation in budding yeast and C. elegans could potentially lead to developing therapeutic strategies to reduce proteotoxicity normally associated in age-related diseases.
