Project Summary/Abstract Inter-organelle communication plays an essential role in maintaining cellular homeostasis and animal aging. Mitochondria, as a highly dynamic organelle and the metabolic hub of the cell, frequently interact with other cellular organelles to coordinate metabolic processes and maintain cellular homeostasis. Although it is well known that mitochondrial dynamics are often altered during animal aging, it remains largely unanswered whether and how inter-organelle communication plays a crucial role in age-dependent alternations of mitochondrial dynamics. Like mitochondria, peroxisomes play an important role in redox and lipid metabolism (e.g., ether phospholipid biosynthesis). However, peroxisome aging research is an understudied area. In this proposal, we will combine CRISPR genome editing, organelle proteomics, metabolomics, and cutting-edge imaging tools to investigate the important role of peroxisome-mitochondrion communication in animal aging. The proposal is based on our previous exciting findings showing that activation of peroxisomal receptor protein Pex5 not only rescued age-dependent decline of peroxisomal import, but also preserved mitochondrial structure and function. We further show that peroxisomal ether phospholipid biosynthesis is involved in the regulation of mitochondrial dynamics. Furthermore, we uncovered a novel positive feedback loop that regulates the ether phospholipid synthesis pathway under oxidative stress. In this proposal, we will address two outstanding questions: 1) Why and how does peroxisomal import decline with age? 2) How does peroxisomal dysfunction contribute to cellular aging? Could inter-organelle communication be a core mechanism? The proposed work will provide novel insights into the significant role of peroxisome-mitochondrion communication in animal health aging and longevity. Three specific aims are proposed: Specific Aim 1. Determine how peroxisomal import function declines with age. Specific Aim 2. De