Molecular mechanisms of mitochondrial membrane transport systems in cellular energetics

PROJECT SUMMARY Membrane transport systems are critical for controlling the central pathway of cellular energetics, from glucose transport across the membrane to regulating energy production in mitochondria. These systems mediate the movement of metabolites and ions between cellular compartments, which is fundamental to normal physiology. Their dysregulation is both a hallmark and driver of many pathologies. Elucidating the molecular basis of how mitochondrial transport systems work is a particularly rich vein: Insights into their transport mechanisms and regulations provide essential information for understanding their functions and roles in mitochondrial physiology. Defects in mitochondrial transport proteins have been implicated in diseases ranging from metabolic disorders to cardiovascular and neurodegenerative diseases, so mechanistic understanding can shed light on disease processes. Here, we propose to decipher the molecular mechanisms and regulation of three key mitochondrial membrane transport systems: 1) the mitochondria calcium uniporter, which constitutes the major calcium portal on mitochondria and mediates rapid calcium uptake, regulating ATP production and cellular calcium signaling; 2) the active calcium transporter NCLX, which plays important roles in various aspects of physiology; and 3) the mitochondrial pyruvate carrier (MPC), which transports pyruvate from cytosol into the mitochondrial matrix, controlling a key metabolic branch point. We take a multi-disciplinary approach to determine the mechanisms of these dynamic membrane protein machines. Our goal is to answer central questions in the field, including substrate selectivity, conformational transitions, small molecule modulations, and transport activity regulation. Successful completion of the proposed work will offer invaluable insights into these essential mitochondrial transport systems. This will deliver new and deeper understanding of mitochondrial physiology and provide novel insights into general principles of membrane transport processes. Furthermore, given that these membrane transport systems are promising drug targets, we expect our mechanistic insights will inform rational design for novel inhibitors and modulators, potentially leading to new therapies for patients.