Project Summary/Abstract Members of the ARF family of regulatory GTPases function as nodes in cell signaling to coordinate essential cell processes; including membrane traffic, energy metabolism, ciliogenesis, and the cytoskeleton. I have studied first ARF and later ARF-like (ARL) proteins for over 30 years, using a combination of biochemical, cell and molecular biological, and phylogenetic approaches and propose to continue these studies with a focus on their actions at specific sites; including mitochondria, cytosol, cilia, and centrosomes. We will both study mechanisms by which one GTPase acts in multiple sites in the same cells, to explore the potential for cross-talk or higher level ordering of cell signaling, but also explore novel, single actions for atypical GTPases as a means of determining shared or unique mechanisms within the family. A better understanding of these systems will reveal novel insights into fundamental aspects of cell biology as well as providing potential targets for intervention to alter the course of human diseases; including but not limited to cancer, heart disease, neurodegeneration, ciliopathies, retinal degeneration, and deafness.