Spatial and temporal organization of cellular functions at membrane contact sites

PROJECT SUMMARY Membrane contact sites (MCSs) play critical roles in spatially organizing cells and facilitating the transfer of biological materials between organelles. MCSs are defined as sites of close apposition between membranes that are physically tethered by protein-protein or protein-lipid interactions and perform specific biological functions. These sites of contact are a ubiquitous mechanism used by cells to facilitate communication between organelles and are associated with a wide array of cellular functions. Given their importance in maintaining cellular homeostasis, it is not surprising that MCSs have been implicated in a wide range of diseases, including neurological diseases, cancer, and pathogen-induced diseases. Our plan for the next five years is to build on the successes we have had studying mitochondrial MCSs and address fundamental unanswered questions that are widely applicable to MCS biology. Our work will be primarily grounded in the yeast system. The simple organelle architecture of budding yeast has proven to be an excellent model for studying MCS form, function, and regulation in mechanistic detail. Our studies in yeast over the past five years have opened avenues of scientific exploration that have broadened the scope of our research program beyond a limited view of a single MCS. Our research program will follow three independent yet complementary directions, each of which will address a critical unanswered question in MCS biology. We will continue our studies on a tripartite membrane contact site between the mitochondria, endoplasmic reticulum, and plasma membrane to elucidate how and why three distinct membranes are brought into functional close contact. We will explore the fundamental mechanisms by which MCSs are coordinately regulated at two different length scales— within a shared space and across the MCS network. We will also examine the role of lipids as critical structural, functional, and regulatory components of MCSs. Our prior accomplishments and plans for the next five years will place us in a strong position to initiate studies in mammalian systems, in which we will examine how the fundamental principles of MCS formation, function, and regulation we uncover in yeast are utilized in more complex cellular settings. Our goal is to uncover fundamental mechanisms used by cells to form and regulate interorganelle contacts and deepen our understanding of MCS physiology. In doing so, we anticipate this work will provide insight into novel therapeutic strategies for a range of human disease conditions in which the manipulation of MCSs can be used to positively influence cellular health and homeostasis.