Caenorhabditis elegans ATAD-3 modulates mitochondrial iron and heme homeostasis Daniela van den Ecker a, 1 , Michael Hoffmann a, 1 , Gesine Müting a, 2 , Silvia Maglioni b , Diran Herebian a , Ertan Mayatepek a , Natascia Ventura b , Felix Distelmaier a, * a Department of General Pediatrics, Neonatology and Pediatric Cardiology, University Children's Hospital, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany b Institute of Clinical Chemistry and Laboratory Diagnostic, Medical Faculty, Heinrich-Heine-University and the IUF- Leibniz Research Institute for Environmental Medicine, Auf'm Hennekamp 50, 40225 Düsseldorf, Germany article info Article history: Received 23 September 2015 Accepted 26 September 2015 Available online 30 September 2015 Keywords: Iron Heme Mitochondria Oxidative phosphorylation Metabolism abstract ATAD3 (ATPase family AAA domain-containing protein 3) is a mitochondrial protein, which is essential for cell viability and organismal development. ATAD3 has been implicated in several important cellular processes such as apoptosis regulation, respiratory chain function and steroid hormone biosynthesis. Moreover, altered expression of ATAD3 has been associated with several types of cancer. However, the exact mechanisms underlying ATAD3 effects on cellular metabolism remain largely unclear. Here, we demonstrate that Caenorhabditis elegans ATAD-3 is involved in mitochondrial iron and heme homeo- stasis. Knockdown of atad-3 caused mitochondrial iron- and heme accumulation. This was paralleled by changes in the expression levels of several iron- and heme-regulatory genes as well as an increased heme uptake. In conclusion, our data indicate a regulatory role of C. elegans ATAD-3 in mitochondrial iron and heme metabolism. © 2015 Elsevier Inc. All rights reserved. 1. Introduction ATAD3 (ATPase family AAA domain-containing protein 3) is a member of the AAA-ATPase family and is present in all multicel- lular eukaryotes. Since its first description in 2003, numerous research studies have tried to address the physiological role of ATAD3. To date, several aspects are known about ATAD3 function: ATAD3 protein is overexpressed in different cancer types and modulates cell growth and apoptosis [1e3]. ATAD3 is a protein of the inner mitochondrial membrane [4,5]. Its C-terminal half locates inside the mitochondrial matrix whereas the N-terminal half pro- trudes into the intermembrane space [6]. Based on this topology, it was speculated that ATAD3 participates in metabolic communica- tions between cytoplasm and mitochondrial matrix [7]. Moreover, ATAD3 might be involved in the biochemical interaction between endoplasmic reticulum and mitochondria [8]. Furthermore, ATAD3 is required for mitochondrial protein synthesis in human cultured cells and binds to the mitochondrial ribosome [9]. ATAD3 also in- teracts with S100B, a calcium sensor protein, which is important for the subcellular localization of ATAD3A [10]. In that respect, ATAD3A seems to be essential for the import and fusion of transport vesicles into the mitochondria [11]. In addition, ATAD3 is crucial for early embryogenesis of Caenorhabditis elegans and Mus musculus [12,13]. Furthermore, ATAD3 plays a role in steroid hormone biosynthesis [8] and it is important for adipogenesis and lipogenesis [14]. Despite this information, the exact function of ATAD3 and the underlying cause for overexpression of the protein in different types of cancer remains unclear. Of note, mitochondria play a crucial role in heme and iron homeostasis and their (dys-)regula- tion are important pathophysiological aspects in tumors, as heme detoxification systems and iron storage proteins are altered [15,16]. Based on this information, we here investigated the influence of C. elegans ATAD-3 on iron and heme homeostasis. Abbreviations: ATAD3, ATPase family AAA domain-containing protein 3; C. elegans, Caenorhabditis elegans; RNAi, RNA-mediated interference; FAC, ferric ammonium citrate; ZnMp, zinc mesoporphyrin. * Corresponding author. Department of General Pediatrics, Heinrich-Heine- University, Moorenstr. 5, D-40225 Düsseldorf, Germany. E-mail address: felix.distelmaier@med.uni-duesseldorf.de (F. Distelmaier). 1 Equal contribution. 2 Present address: Institute for Occupational Medicine and Social Medicine, Heinrich-Heine-University Düsseldorf, Universit€atsstraße 1, 40225 Düsseldorf, Germany. Contents lists available at ScienceDirect Biochemical and Biophysical Research Communications journal homepage: www.elsevier.com/locate/ybbrc http://dx.doi.org/10.1016/j.bbrc.2015.09.143 0006-291X/© 2015 Elsevier Inc. All rights reserved. Biochemical and Biophysical Research Communications 467 (2015) 389e394