Organelles on the move: insights from yeast vacuole inheritance

Organelle inheritance is one of several processes that occur during cell division and is an intrinsic part of the cell cycle. Recent studies on vacuole inheritance in the yeast Saccharomyces cerevisiae have indicated rules that probably apply to most organelle-inheritance pathways.These rules include the fact that organelle inheritance is spatially controlled — organelles are targeted to the correct location in daughter cells — and that organelle inheritance is precisely coordinated with the cell cycle.The S. cerevisiae vacuole moves using a myosin-V motor, Myo2, which is found in almost all eukaryotes. Including the vacuole, Myo2 can move at least six distinct cargoes, and it is linked to its cargoes through cargo-specific receptors.Myo2 attaches to the vacuole through interactions with Vac17, which, in turn, interacts with the vacuole membrane protein Vac8. Together, these proteins link Myo2 to the vacuole, and they also have regulatory roles in vacuole inheritance.The regulation of Vac17 turnover has a role in placing the vacuole in the correct cellular location. In addition, the regulation of VAC17 transcription probably coordinates vacuole inheritance with the cell cycle. Vac8 has several vacuole-related functions, so it might coordinate vacuole inheritance with other vacuole processes.Genetic studies have shown that the signalling lipid phosphatidylinositol-3,5-bisphosphate is required for vacuole inheritance. It seems to function in the fission of the vacuole segregation structure, which terminates vacuole inheritance. It might also function in the initiation of vacuole inheritance through a role in the formation of the tubules that make up the vacuole segregation structure.