Abstract Protein homeostasis (proteostasis) is crucial for organism fitness, and its disturbance during aging underlies age-associated neurodegenerative diseases. It is well known that the pathology of Alzheimer’s disease (AD) is associated with disruption of proteostasis, leading to aggregation of ß-amyloid (Aß) and hyperphosphorylated Tau. However, it remains unclear the cellular and molecular mechanism by which proteostasis is disrupted by AD during the aging process. Lysosomes and endoplasmic reticulum (ER) are two groups of organelles that play crucial roles in regulating cellular homeostasis and organismal health. Lysosomes are highly metabolic active and contain various enzymes dedicated to the hydrolysis of specific substrates. At the same time, others’ and our studies also reveal the signaling role of lysosomes, which is tightly linked with the metabolic status of the lysosome. On the other hand, ER is essential for protein synthesis and utilizes quality control mechanisms to maintain proteostasis. To date, it remains poorly understood how mechanistically lysosomal metabolism and signaling regulate ER proteostasis. In our studies using Caenorhabditis elegans, we have discovered a novel lysosome-to-nucleus retrograde signaling pathway that links lysosomal NADPH metabolism and ER proteostasis, and also revealed the crucial role of this lysosomal signaling in AD prevention during aging. Strikingly, this lysosomal signaling pathway carries molecular, cellular and biochemical conservation in human. In this proposal, we aim to systemically decipher lysosomal and nuclear components of this signaling pathway in C. elegans, and to elucidate how this pathway controls ER proteostasis and contributes to AD pathogenesis in the mammalian nervous system. The proposed studies, although designed in animal models (C. elegans and mice), will set a stage for understanding the role of lysosomal metabolism and lysosomal signaling in human health and diseases. The successful accomplishment of this project will advance our current knowledge regarding lysosomal function and signaling in aging and AD, open a new avenue for understanding AD pathogenesis during aging, and shed light on the prevention and treatment of AD patients in our current society and future generations.