Studies myosin V based transport, and phosphoinositide lipid signaling in yeast and in neurons. Intracellular membrane movement and signalling Our laboratory studies how the yeast lysosome (vacuole) is partitioned between mother and daughter cells during cell division. Yeast have been instrumental in determining the molecular basis of many biological processes in higher eukaryotes. These include events that are unique to complex, multi-cellular organisms. For example several advances in understanding the molecular basis of synaptic transmission came from studies in yeast. Studies of vacuole inheritance in yeast are likely to provide general insight into organelle movement, cell polarization/differentiation and cellular signaling. Vacuole inheritance is a highly dynamic, regulated process. In order to identify the molecules required, we developed screens for yeast vac mutants. Studies of these mutants led to our discovery of a vacuole-specific transport complex. This complex is very similar to a complex that moves melanosomes in melanocytes, and synaptic vesicles in neurons. We have recently found that the regulated synthesis and turnover of this complex deposits the vacuole at the correct place at the proper time. We have also discovered a set of mutants that are defective in the phosphatidylinositol 3,5 bis-phosphate signaling pathway. Molecules required for this pathway include Fab1, Vac7, Vac14 and Fig4. Interestingly, while these proteins were first identified in yeast, higher eukaryotes also have genes encoding Fab1, Vac14 and Fig4. We are studying the functions of these human genes. Preliminary data suggests that these genes are essential. Our studies of vacuole inheritance in yeast has provided important clues to: * The mechanism that allows myosin to associate with its cargo. * The existence of a higher order regulation of diverse events that happen at a single membrane. * The importance of phosphatidylinositol 3,5 bis-phosphate (PI3,5P 2) in cell signaling. * The roles for PI(3,5)P 2 in response to cellular stress.