Elucidation of the mechanism of autophagy-mediated RNA degradation by
metabolome analysis
メタボローム解析を用いたオートファジーによるRNA分解機構の解明
Abstract of Thesis
Autophagy is a membrane-dynamic self-degradation system conserved among eukaryotes. Recent studies have revealed its multiple roles in physiology and pathophysiology, including starvation adaptation, cellular protein and organelle clearance, anti-microorganism, etc. Autophagy involves the degradation of various autophagic cargoes including different organelles and macromolecules, which inevitably induces drastic changes in the metabolome. However, due to the limitation of traditional approaches, such information has been extremely limited. To deepen our knowledge on autophagy, this study approached from a brand-new viewpoint by employing metabolome analysis for the investigation of autophagy process and through monitoring the changes induced by autophagy at metabolome level, it shed new light on the mechanism of autophagy-induced RNA degradation under starvation conditions.
This thesis is comprised of 4 chapters. A general introduction of autophagy and metabolomics was presented in Chapter 1. In particular, the potential and necessity of applying metabolome analysis to autophagy study were elaborated. In Chapter 2, overall changes in the metabolome during autophagy were first investigated. The metabolic profiling of yeast S. cerevisiae X2180 (wild-type) and an autophagy-defective mutant (atg2∆) under three commonly studied autophagy-triggering conditions were performed and compared. The results highlighted RNA-related metabolites as a potential point of interest: intriguing changing patterns in nucleosides were observed, which strongly suggested autophagy-induced RNA degradation under starvation conditions. Therefore, in Chapter 3, the research was focused on elucidating the mechanism of autophagy-induced RNA degradation. With a combination of metabolome analysis to monitor the dynamic changes of intra- and extra-cellular metabolites under starvation conditions and molecular genetic approaches tractable in yeast, a comprehensive picture of RNA degradation via autophagy was successfully characterized. In Chapter 4, the important conclusions obtained in this study were summarized and the future perspectives were presented. This thesis represents a successful example of metabolomics in autophagy study from discovering a problem to solving it and demonstrates the power of metabolomics as a useful tool for investigating mechanisms of physiological phenomena.