Abstract Loss of proteostasis and unresolved senescence are two drivers of aging, however, little is known about their possible interplay in aging. Although senescent cells are of transient nature, abnormal tissue accumulation of senescent cells occurs with age and contributes to functional loss and increased vulnerability to disease in old organisms. Research on the relation between senescence and proteostasis is still limited and lacks systematic studies on the impact of proteostasis loss in the different steps of senescence. This proposal focuses on chaperone-mediated autophagy (CMA), a component of the cellular proteostasis network that facilitates selective removal of proteins. Both, senescence and CMA are part of the cellular responses to damage and malfunction with age, but the contribution of reduced CMA activity in aging to unresolved senescence has not been explored before. Engagement and resolution of senescence require major proteome changes to modulate translation attenuation, energetic switches, and changes in protein secretion, all of them functions that CMA modulates in other cellular conditions. Therefore, we propose that 1) CMA may contribute to part of the proteome remodeling required for transient senescence and that 2) the decline in CMA with age impairs senescence clearance and leads to persistence of unresolved senescence and its long-term detrimental effects. We aim to understand 1) if CMA activity changes upon induction of senescence, 2) if CMA modulates senescence’s kinetics of and if so, by which mechanism(s), 3) if CMA is required for senescent cells immunoclearance and 4) if restoring CMA activity in aged mice reduces their organ senescent cell overload. We will use novel photoswitchable reporters to track CMA after different pro-senescence stimuli, and will genetically downregulate CMA to mimic its change in aging. Using targeted proteomics, we will study the impact of reduced CMA on senescence-triggered translational attenuation and in the senescence-associated secretory phenotype (SASP). We have generated mice defective in CMA in immune cells to explore the role of CMA in immunoclearance of senescence cells. Lastly, we will undertake both genetic and pharmacological approaches to enhance CMA in old mice and analyze the impact on the senescence cell overload of different organs. During this training period, I will be co-mentored by Drs. Ana Maria Cuervo, Susmita Kaushik and the collaborators in this project. This excellent mentoring team will allow me to 1) expand my technical abilities; 2) acquire a strong background on proteostasis, biology of aging and pharmacological interventions; 3) formulate and test scientific hypothesis; 4) improve my oral presentation and scientific writing skills; 5) consolidate a network of collaborators in biology of aging and 6) prepare me for a postdoctoral position as the next stage of my career in aging research. Significance: Our studies will advance understanding of the mechanism ...