Role of the Rab GTPase Ypt7 in vacuole membrane contacts and signaling

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Cells require continuous supply of nutrients such as amino acids, lipids and ions. A central recycling organelle is the yeast lysosome-like vacuole, which also hosts a major regulator of cell growth, the TOR kinase complex 1 (TORC1) and its activating complex, the EGO/LamTOR complex. Apart from continuous fusion with endosomes and other vesicles, vacuoles form contact sites with other organelles, whose function is still poorly understood. Within the frame of this grant, my group would like to concentrate on the role of yeast Rab7-like GTPase Ypt7 in signaling processes and contact sites on the vacuole membrane. We recently identified on a novel vacuole-mitochondrial contacts site, called vCLAMP, which is formed by the HOPS subunit Vps39 and Ypt7. Furthermore, we characterized the IBAR protein Ivy1 as a novel Ypt7 effector on vacuoles that localizes to vacuolar membrane domains and affects vacuole biogenesis. We hypothesize that Ypt7 function on the vacuole is controlled during different growth phases on changes in metabolic activity and is involved domain formation on the vacuole. These aspects will be addressed in two defined, parallel projects on the cellular function of vCLAMPs (project 1) and the function of the Ivy1 in controlling vacuole membrane homeostasis (project 2).