The project will address fundamental questions about the evolution of the relationship between structure and function in cells. All cells share a set of activities, many of which involve interactions with their environment. The subject of this proposal is the pathways that allow cells to take up particles from their environment, which can be carried to a compartment where they are digested. Alternatively, such ingested particles can be transported to other compartments and integrated into cellular metabolism. The research will determine if different cells are relying on the same mechanisms, or whether, over time, have evolved diverse mechanisms to achieve similar tasks. The research will also address how cells control the transport of ingested particles by implementing experiments which test the hypothesis that the various possible outcomes are in competition with one another, and that a cell can precisely regulate the “flow†down different pathways.
The project will be pursued in the ciliate Tetrahymena thermophila and will focus on pathways in the ‘endolysosomal’ network. Tetrahymena ingests bacteria by a phagocytosis-dependent pathway, and then digests those bacteria in phagolysosomes whose activity depends on delivery of hydrolytic enzymes. The research will define the pathways involved in delivery of proteins to phagolysosomes and ask whether they are the same or different as the pathways used in mammalian cells. In Tetrahymena, hydrolytic enzymes are also delivered to generate a specific secretory compartment. Experiments in the project will test the hypothesis that competition between molecular tethering complexes in the CORVET family determines the relative flux of key hydrolytic enzymes to secretory organelles vs phagolysosomes, depending on cellular conditions. The experiments will be based on natural and induced fluctuations in the abundance of specific CORVET subunits. The experiments will also take advantage of the fact that CORVET tethers are recruited by Rab GTPases, so that manipulation of Rab activities can be used to indirectly influence CORVET function. The project will provide an environment to introduce undergraduates to research, and for the training of one PhD student and one postdoctoral fellow.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
