Quantitative analysis of mitochondrial calcium uniporter (MCU) and essential MCU regulator (EMRE) in mitochondria from mouse tissues and HeLa cells. Issue 4 (23rd February 2022)

• Record Type: Journal Article
• Authors: Watanabe, Akira; Maeda, Kousuke; Nara, Atsushi; Hashida, Mei; Ozono, Mizune; Nakao, Ayaka; Yamada, Akiko; Shinohara, Yasuo; Yamamoto, Takenori
• Other Names: Martinez‐Fabregas Jonathan guestEditor.
• Is Part Of: FEBS open bio. Volume 12:Issue 4(2022)
• Page Start: 811
• Page End: 826
• Publication Date: 2022-02-23
• Subjects: calcium uniporter -- EMRE -- ion channel -- MCU -- mitochondria -- stoichiometry; Molecular biology -- Periodicals; Cytology -- Periodicals; Life sciences -- Periodicals; Biological Science Disciplines -- Periodicals; Molecular Biology -- Periodicals; Cell Biology -- Periodicals; Cytology; Life sciences; Molecular biology; Periodicals; 572.805
• DOI: 10.1002/2211-5463.13371
• Languages: English
• ISSNs: 2211-5463

Abstract

Abstract : Mitochondrial calcium homeostasis plays critical roles in cell survival and aerobic metabolism in eukaryotes. The calcium uniporter is a highly selective calcium ion channel consisting of several subunits. Mitochondrial calcium uniporter (MCU) and essential MCU regulator (EMRE) are core subunits of the calcium uniporter required for calcium uptake activity in the mitochondria. Recent 3D structure analysis of the MCU‐EMRE complex reconstituted in nanodiscs revealed that the human MCU exists as a tetramer forming a channel pore, with EMRE bound to each MCU at a 1 : 1 ratio. However, the stoichiometry of MCU and EMRE in the mitochondria has not yet been investigated. We here quantitatively examined the protein levels of MCU and EMRE in the mitochondria from mouse tissues by using characterized antibodies and standard proteins. Unexpectedly, the number of EMRE molecules was lower than that of MCU; moreover, the ratios between MCU and EMRE were significantly different among tissues. Statistical calculations based on our findings suggest that a MCU tetramer binding to 4 EMREs may exist, but at low levels in the mitochondrial inner membrane. In brain mitochondria, the majority of MCU tetramers bind to 2 EMREs; in mitochondria in liver, kidney, and heart, MCU tetramers bind to 1 EMRE; and in kidney and heart, almost half of MCU tetramers bound to no EMRE. We propose here a novel stoichiometric model of the MCU‐EMRE complex in mitochondria. Abstract : The calcium uniporter in the mitochondria is a highly selective calcium ion channel consisting of several subunits. In this study, we quantitatively examined the protein levels of core subunits of the calcium uniporter (MCU and EMRE). Unexpectedly, there were fewer EMRE molecules than MCU molecules; moreover, the MCU and EMRE ratios were significantly different among tissues.