Yeast homologs of human MCUR1 regulate mitochondrial proline metabolism

Mitochondria house evolutionarily conserved pathways of carbon and nitrogen metabolism that drive cellular energy production. Mitochondrial bioenergetics is regulated by calcium uptake through the mitochondrial calcium uniporter (MCU), a multi-protein complex whose assembly in the inner mitochondrial membrane is facilitated by the scaffold factor MCUR1. Intriguingly, many fungi that lack MCU contain MCUR1 homologs, suggesting alternate functions. Herein, we characterize Saccharomyces cerevisiae homologs Put6 and Put7 of MCUR1 as regulators of mitochondrial proline metabolism. Put6 and Put7 are tethered to the inner mitochondrial membrane in a large hetero-oligomeric complex, whose abundance is regulated by proline. Loss of this complex perturbs mitochondrial proline homeostasis and cellular redox balance. Yeast cells lacking either Put6 or Put7 exhibit a pronounced defect in proline utilization, which can be corrected by the heterologous expression of human MCUR1. Our work uncovers an unexpected role of MCUR1 homologs in mitochondrial proline metabolism. Although some fungal mitochondria lack the calcium uniporter, many intriguingly encode homologs of the uniporter assembly factor MCUR1. Here, the authors show that in budding yeast, the MCUR1 homologs Put6 and Put7 regulate mitochondrial proline metabolism, a function also conserved in human MCUR1

Elesclomol restores mitochondrial function in genetic models of copper deficiency

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 115 (2018): 8161-8166, doi:10.1073/pnas.1806296115.Copper is an essential cofactor of cytochrome c oxidase (CcO), the terminal enzyme of the mitochondrial respiratory chain. Inherited loss-of-function mutations in several genes encoding proteins required for copper delivery to CcO result in diminished CcO activity and severe pathologic conditions in affected infants. Copper supplementation restores CcO function in patient cells with mutations in two of these genes, COA6 and SCO2, suggesting a potential therapeutic approach. However, direct copper supplementation has not been therapeutically effective in human patients, underscoring the need to identify highly efficient copper transporting pharmacological agents. By using a candidate-based approach, we identified an investigational anticancer drug, elesclomol (ES), that rescues respiratory defects of COA6-deficient yeast cells by increasing mitochondrial copper content and restoring CcO activity. ES also rescues respiratory defects in other yeast mutants of copper metabolism, suggesting a broader applicability. Low nanomolar concentrations of ES reinstate copper-containing subunits of CcO in a zebrafish model of copper deficiency and in a series of copper-deficient mammalian cells, including those derived from a patient with SCO2 mutations. These findings reveal that ES can restore intracellular copper homeostasis by mimicking the function of missing transporters and chaperones of copper, and may have potential in treating human disorders of copper metabolism.This work was supported by National Institutes of Health Awards R01GM111672 (to V.M.G.), R01 DK110195 (to B.-E.K.), and DK 44464 (to J.D.G.); Welch Foundation Grant A-1810 (to V.M.G.); and Canadian Institutes of Health Research Operating Grant MOP 133562 (to S.C.L.)

MCUR1 Is a Scaffold Factor for the MCU Complex Function and Promotes Mitochondrial Bioenergetics

Mitochondrial Ca2+ Uniporter (MCU)-dependent mitochondrial Ca2+ uptake is the primary mechanism for increasing matrix Ca2+ in most cell types. However, a limited understanding of the MCU complex assembly impedes the comprehension of the precise mechanisms underlying MCU activity. Here, we report that mouse cardiomyocytes and endothelial cells lacking MCU regulator 1 (MCUR1) have severely impaired [Ca2+]m uptake and IMCU current. MCUR1 binds to MCU and EMRE and function as a scaffold factor. Our protein binding analyses identified the minimal, highly conserved regions of coiled-coil domain of both MCU and MCUR1 that are necessary for heterooligomeric complex formation. Loss of MCUR1 perturbed MCU heterooligomeric complex and functions as a scaffold factor for the assembly of MCU complex. Vascular endothelial deletion of MCU and MCUR1 impaired mitochondrial bioenergetics, cell proliferation, and migration but elicited autophagy. These studies establish the existence of a MCU complex that assembles at the mitochondrial integral membrane and regulates Ca2+-dependent mitochondrial metabolism

MCUR1 Is a Scaffold Factor for the MCU Complex Function and Promotes Mitochondrial Bioenergetics

Publisher's PDFMitochondrial Ca2+ Uniporter (MCU)-dependent mitochondrial Ca2+ uptake is the primary mechanism for increasing matrix Ca2+ in most cell types. However, a limited understanding of the MCU complex assembly impedes the comprehension of the precise mechanisms underlying MCU activity. Here, we report that mouse cardiomyocytes and endothelial cells lacking MCU regulator 1 (MCUR1) have severely impaired [Ca2+](m) uptake and I-MCU current. MCUR1 binds to MCU and EMRE and function as a scaffold factor. Our protein binding analyses identified the minimal, highly conserved regions of coiled-coil domain of both MCU and MCUR1 that are necessary for heterooligomeric complex formation. Loss of MCUR1 perturbed MCU heterooligomeric complex and functions as a scaffold factor for the assembly of MCU complex. Vascular endothelial deletion of MCU and MCUR1 impaired mitochondrial bioenergetics, cell proliferation, and migration but elicited autophagy. These studies establish the existence of a MCU complex that assembles at the mitochondrial integral membrane and regulates Ca2+-dependent mitochondrial metabolism.University of Delaware, Delaware Biotechnology Institute, Department of Biological Science