The Effects of S-glutathionylation on the Structure and Function of the Mitochondrial Calcium Uniporter (MCU)
Abstract
Most calcium (Ca2+) entry into the mitochondrial matrix is regulated by the mitochondrial calcium uniporter (MCU). The amino (N)-terminal domain (NTD) of MCU is a regulatory component of the channel. S-Glutathionylation of Cys97 on the MCU-NTD leads to robust MCU activation and increased matrix Ca2+. Here, I characterized the biophysical and structural changes induced by Cys97 S-glutathionylation by applying optical spectroscopy, light scattering, solution nuclear magnetic resonance (NMR) and live cell functional experiments. S-Glutathionylation increased solvent exposed hydrophobicity, destabilized and caused large structural perturbations in the MCU-NTD. An S-glutathiomimetic mutation was able to closely recapitulate these biophysical and structural effects, but in the absence of oxidative stress. Indeed, HeLa cells expressing MCU with the S-glutathiomimetic mutation, showed increased mitochondrial Ca2+ uptake compared to wild-type MCU expressing cells. Thus, my research revealed new insights into the impact of S-glutathionylation on MCU-NTD and identified the S-glutathiomimetic mutation as a valuable research tool.