Graduate School of Frontier Sciences, The University of Tokyo Department of
Integrated Biosciences

Our laboratory uses budding yeast, a unicellular eukaryote, as a model organism for eukaryotic cells to study the dynamics of organelles using bioimaging techniques and cell biological methods. Membrane organelles such as cell nucleus, mitochondria, endoplasmic reticulum, vacuole, and peroxisome exist in budding yeast, and they adapt to their environment by changing their functions and morphology. Recent studies have revealed that each of these membrane organelles, centered on the endoplasmic reticulum, contact each other to form membrane contact sites and exchange substances and signals. Furthermore, the existence of organelles called membraneless organelles, which are not enclosed with membranes, has also become known. Membraneless organelles are considered to be suitable structures for rapid environmental responses because they are not enveloped by membranes. As a membrane organelle, our research focuses on the formation and degradation of autophagosomes, which are formed during autophagy, an intracellular process induced during nutrient starvation. We are also promoting functional analysis of novel membraneless organelles screened from our unique viewpoints.

(1) Functional analysis of contact sites between membrane organelles through autophagy research

We are studying autophagy using budding yeast as a model system for eukaryotic cells. Autophagy is an interesting phenomenon because the process of autophagosome formation proceeds with a very characteristic and dynamic membrane phenomenon. During autophagosome formation, researchers believe that phospholipids are supplied via membrane contact sites with the endoplasmic reticulum. To elucidate these questions, we are conducting research using live imaging and in vitro reconstitution techniques.

(2) Mechanism of membrane organelle disintegration through autophagy studies

As autophagy progresses, a double membrane organelle called an autophagosome is formed. The outer membrane of the autophagosome fuses with the vacuole, and the autophagic body consisting of the inner membrane is released into the vacuole. In order to degrade the contents of the autophagic body, the cytoplasmic components, the autophagic body membrane must first be degraded. We are currently analyzing the substrate recognition mechanism of an enzyme that degrades the autophagic body membrane.

(3) Functional analysis of membraneless organelles obtained by comprehensive screening

Our laboratory has identified many candidates of membraneless organelles by our original screening using budding yeast libraries. We have high expectations that further analysis of these candidates will open up new areas of research on membraneless organelles.