title: MNRR1 (formerly CHCHD2) is a bi-organellar regulator of mitochondrial metabolism.
abstract: Our understanding of stress-associated regulatory mechanisms for mitochondria remains incomplete. We now report a new regulator of mitochondrial metabolism, the coiled-coil-helix-coiled-coil-helix domain-containing protein 2 (CHCHD2) which, based on the functionality described here, is renamed MNRR1 (Mitochondria Nuclear Retrograde Regulator 1). It functions in a novel way by acting in two cellular compartments, mitochondria and nucleus. In normally growing cells most MNRR1 is located in mitochondria; during stress most MNRR1 is now located in the nucleus. MNRR1 is imported to the mitochondrial intermembrane space by a Mia40-mediated pathway, where it binds to cytochrome c oxidase (COX). This association is required for full COX activity. Decreased MNRR1 levels produce widespread dysfunction including reduced COX activity, membrane potential, and growth rate, and increased reactive oxygen species and mitochondrial fragmentation. In the nucleus, MNRR1 acts as a transcription factor, one of whose targets is the COX subunit 4 isoform, COX4I2, which is transcriptionally stimulated by hypoxia. This MNRR1-mediated stress response may provide an important survival mechanism for cells under conditions of oxidative or hypoxic stress, both in the acute phase by altering mitochondrial oxygen utilization and in the chronic phase by promoting COX remodeling.
authors.affiliation: Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48201 USA.
authors.forename: Siddhesh
authors.initials: S
authors.lastname: Aras
authors.affiliation: Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48201 USA.
authors.forename: Minbo
authors.initials: M
authors.lastname: Bai
authors.affiliation: Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48201 USA; College of Medicine, Dankook University, Cheonan-si, Chungcheongnam-do 330-714, Republic of Korea.
authors.forename: Icksoo
authors.initials: I
authors.lastname: Lee
authors.affiliation: Medical Research Council Mitochondrial Biology Unit, Wellcome Trust, MRC Building, Hills Road, Cambridge CB2 0XY, UK.
authors.forename: Roger
authors.initials: R
authors.lastname: Springett
authors.affiliation: Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48201 USA; Cardiovascular Research Institute, Wayne State University, Detroit, MI 48201, USA.
authors.forename: Maik
authors.initials: M
authors.lastname: Hüttemann
authors.affiliation: Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48201 USA; Cardiovascular Research Institute, Wayne State University, Detroit, MI 48201, USA. Electronic address: lgrossman@wayne.edu.
authors.forename: Lawrence I
authors.initials: LI
authors.lastname: Grossman
mesh_terms: D002467:Cell Nucleus / Q000737:chemistry*; D004268:DNA-Binding Proteins; D003576:Electron Transport Complex IV / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D008928:Mitochondria / Q000737:chemistry*; D024101:Mitochondrial Proteins / Q000032:analysis*; D011485:Protein Binding; D013312:Stress, Physiological; D014157:Transcription Factors / Q000032:analysis*
chemical_list: C580880:CHCHD2 protein, human; D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; D014157:Transcription Factors; D003576:Electron Transport Complex IV
keywords: COX4I2; Hypoxia; Mitochondria; Stress