Speaker: Dr. Riko Hatakeyama, Lecturer at University of Aberdeen, Scotland, UK

Title: TORC1-containing signaling endosomes: Discovery and characterization of a cellular signaling centre.

Abstract:

Eukaryotic cells are compartmentalized by membrane structures, or organelles, that perform specialized functions. Understanding the architecture, functions, and biogenesis of organelles is fundamental to cell biology. My lab studies yeast signaling endosomes (SEs), a novel organelle we reported in 2019. Our observations indicate that SEs act as a cellular signaling centre, connecting cell growth and metabolism to membrane trafficking.

SEs accommodate on their surface the Target of Rapamycin Complex 1 (TORC1) kinase complex, an evolutionarily conserved master regulator of cell growth and metabolism. The TORC1 pool residing at SEs is functionally distinct from the canonical, vacuolar TORC1 pool. This division of labor between spatially distinct pools of TORC1 explains, at least in part, why TORC1 can regulate diverse biological processes operating at different subcellular locations. In this talk, I will first summarize the specific functions of the SE-TORC1 pool we have identified to date.

I will then introduce our recent findings on the biogenesis of SEs. To understand how SEs are generated, we developed a system to induce and observe their biogenesis in real time. Using this system, we found that SEs originate from the vacuolar membrane. This work unveiled the first mechanistic principle and molecular participants of SE biogenesis.

Having established the signaling function and biogenesis mechanism of SEs, we still largely lack basic knowledge of this organelle. We know little about the composition, dynamics, regulation, and evolutionary conservation of SEs. I will discuss our ongoing approaches to advance SE biology, aimed at a better understanding of cellular responses to metabolic and environmental changes.