Abstract

Peroxisomes are organelles best known for their essential roles in lipid metabolism and hydrogen peroxide detoxification. Peroxisomal biogenesis in the yeast Yarrowia lipolytica is a multi-step process of temporally ordered sequential conversion of five distinct peroxisomal subforms, termed P1 to P5, into a mature peroxisomal subform P6 carrying the complete set of matrix and membrane proteins. In the first part of my thesis, I investigate the effect of lateral heterogeneity of the peroxisomal membrane bilayer on the efficiency of the fusion between P1 and P2 in the yeast Y. lipolytica. My findings provide a unique view of the multistep remodeling of the protein repertoire of ergosterol- and ceramide-rich (ECR) domains found in the peroxisomal membrane during fusion of P1 and P2, and define the hierarchy of individual steps during the spatial and temporal reorganization of the peroxisome fusion machinery that only transiently associates with ECR domains. In the second part of my thesis, I described the use of mass spectrometry-based proteomics for examining the contribution of peroxisomal proteins to longevity regulation in the yeast Saccharomyces cerevisiae grown under calorie restriction (CR) conditions. My proteomic analysis and experimental results from Dr. Titorenko's laboratory show that CR yeast are able to meet their metabolic requirements by remodeling their carbohydrate and lipid metabolism, which relies on functional lipid metabolic pathways in the peroxisome. These findings suggest that peroxisomal Ý-oxidation of fatty acids significantly affects the rate of chronological aging in CR yeast by defining the rate of ATP production in their mitochondria but not by making ROS. I also present my research findings on longevity regulation in S. cerevisiae by a novel anti-aging molecule "LA" identified recently in Dr. Titorenko's laboratory. Comprehensive analysis of the proteome remodeling in yeast placed on a CR diet and exposed to LA, along with experimental data obtained through various metabolomic and functional studies in Dr. Titorenko's laboratory, demonstrate that LA extends yeast chronological lifespan by maintaining the mitochondrial production of ROS at an optimal level that does not excessively damage cellular macromolecules but triggers a potent cellular stress response