Mechanisms of de novo membrane assembly

7. PROJECT SUMMARY/ABSTRACT The ability to rearrange vesicular traffic to create new membrane compartments de novo is a fundamental cell biological process important for many aspects of cellular physiology and differentiation. Two common examples of this phenomenon are the creation of autophagosomes and the generation of the ciliary sheath. In both cases, vesicles coalesce on a protein substrate to create a small double membrane that subsequently expands into a distinct organelle. Defects in these processes are associated with a variety of diseases, highlighting the importance of this aspect of cellular physiology to human health. Prospore membrane formation during the process of sporulation in budding yeast is another example of a de novo membrane formation event. Prospore membrane formation occurs on the microtubule organizing center of the cells, analogous to the ciliary sheath in higher cells, and the prospore membrane expands to encapsulate cytoplasmic components, analogous to an autophagosome. These similarities are due to parallels at the molecular level that make yeast sporulation a powerful model system to identify the underlying molecular mechanisms of membrane assembly. The experiments in this proposal are focused on two aspects of this process: 1) how the MOP promotes coalescence of vesicles to create the prospore membrane, and 2) how the Vps13 lipid transfer protein promotes membrane expansion.