CAREER: A Toolkit to Modulate the Mitochondrial Calcium Uptake Machinery

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Mitochondria are critical components of a cell because they produce most of the chemical energy the cell needs and influence the cell survival and death pathways. Calcium ion entry in, and exit from, mitochondria is crucial for the function of these cellular components; conversely, deregulation of mitochondrial calcium levels was implicated in several human diseases. The understanding of how the calcium ions influence the function of the mitochondria depends on having appropriate tools to selectively decrease the uptake of calcium by mitochondria. With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Professor Justin Wilson from Cornell University to develop such tools based on small-molecule regulators of mitochondrial calcium uptake. These tools are valuable to the larger research community that studies the important roles of calcium in biology and in human health and disease. The graduate students who conduct research in Professor Wilson's lab gain knowledge of bioinorganic chemistry and acquire skills in synthetic chemistry and cell biology that prepare them to become members of the next generation of scientists. Professor Wilson also works on enhancing STEM education in rural communities by organizing outreach activities and workshops for K-12 STEM teachers. This research project develops inhibitors of the mitochondrial calcium uniporter (MCU), which is the only known calcium transporter protein in mitochondria. The MCU was conclusively identified in 2011. Its precise role in modulating the biological effects of mitochondrial calcium levels remains uncertain. Efforts to elucidate the roles of the MCU in mediating cellular processes would be strengthened by a toolkit of selective MCU modulators that operate in a range of biological conditions and settings. The only known selective inhibitor for the MCU is the dinuclear oxo-bridged ruthenium complex Ru360. However, the experimental use of this compound is limited by several factors. The complex is useful only for studying isolated mitochondria or permeabilized cells because it cannot penetrate into cells; isolated mitochondria or permeabilized cells are too simple to afford the extrapolation of results and conclusions to in vivo systems. Furthermore, the mechanism of action of Ru360 is unknown, which prevents the design of improved analogues. Professor Wilson develops MCU inhibitors based on Ru360. The development of these inhibitors is first based on gaining mechanistic insight with respect to how Ru360 functions. The interactions of this compound with biomolecules relevant to its MCU-inhibitory activity is studied by NMR and EPR spectroscopy. The insight gained from the mechanistic studies is applied in the design of new ruthenium-based MCU inhibitors with enhanced cell permeability and aqueous stability. These new inhibitors are evaluated in living mammalian cells to verify that their MCU-inhibitory activity is retained in complex biological systems. The new tools may be used to elucidate the role and importance of the MCU in mediating physiological and pathophysiological cellular processes, thereby leading to deeper insight into the fundamental cell biology of calcium and its importance in human health.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.