SLIRP Regulates the Rate of Mitochondrial Protein Synthesis and Protects LRPPRC from Degradation

Marie Lagouge; Arnaud Mourier; Hyun Ju Lee; Henrik Spåhr; Timothy Wai; Christian Kukat; Eduardo Silva Ramos; Elisa Motori; Jakob D Busch; Stefan Siira; German Mouse Clinic Consortium; Elisabeth Kremmer; Aleksandra Filipovska; Nils-Göran Larsson

doi:10.1371/journal.pgen.1005423

SLIRP Regulates the Rate of Mitochondrial Protein Synthesis and Protects LRPPRC from Degradation

PLoS Genet. 2015 Aug 6;11(8):e1005423. doi: 10.1371/journal.pgen.1005423. eCollection 2015 Aug.

Affiliations

¹ Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, Cologne, Germany.
² CECAD Research Center, University of Cologne, Cologne, Germany.
³ FACS and Imaging facility, Max Planck Institute for Biology of Ageing, Cologne, Germany.
⁴ Harry Perkins Institute of Medical Research, Centre for Medical Research and School of Chemistry and Biochemistry, The University of Western Australia, Perth, Australia.
⁵ Helmholtz Zentrum München, Institute of Molecular Immunology, Munich, Germany.
⁶ Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, Cologne, Germany; Department of Laboratory Medicine, Karolinska Institute, Stockholm, Sweden.

Abstract

We have studied the in vivo role of SLIRP in regulation of mitochondrial DNA (mtDNA) gene expression and show here that it stabilizes its interacting partner protein LRPPRC by protecting it from degradation. Although SLIRP is completely dependent on LRPPRC for its stability, reduced levels of LRPPRC persist in the absence of SLIRP in vivo. Surprisingly, Slirp knockout mice are apparently healthy and only display a minor weight loss, despite a 50-70% reduction in the steady-state levels of mtDNA-encoded mRNAs. In contrast to LRPPRC, SLIRP is dispensable for polyadenylation of mtDNA-encoded mRNAs. Instead, deep RNA sequencing (RNAseq) of mitochondrial ribosomal fractions and additional molecular analyses show that SLIRP is required for proper association of mRNAs to the mitochondrial ribosome and efficient translation. Our findings thus establish distinct functions for SLIRP and LRPPRC within the LRPPRC-SLIRP complex, with a novel role for SLIRP in mitochondrial translation. Very surprisingly, our results also demonstrate that mammalian mitochondria have a great excess of transcripts under basal physiological conditions in vivo.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Cells, Cultured
Female
Gene Expression Regulation
Male
Mice, Inbred C57BL
Mice, Knockout
Mitochondrial Proteins / biosynthesis*
Neoplasm Proteins / metabolism*
Polyadenylation
Protein Biosynthesis
Proteolysis
RNA Stability
RNA, Messenger / genetics
RNA, Messenger / metabolism
RNA-Binding Proteins / physiology*
Ribosomes / metabolism

Substances

Lrpprc protein, mouse
Mitochondrial Proteins
Neoplasm Proteins
RNA, Messenger
RNA-Binding Proteins
SLIRP protein, mouse

Grants and funding

The study was supported by a post-doctoral grant from the AXA Research Fund (ARF) to ML, by a European Research Council advanced investigator grant (268897) and by grants from the Deutsche Forschungsgemeinschaft (SFB829) and the Swedish Research Council (2013–2859) to NGL. AF is a National Health and Medical Research Council Senior Research Fellow (APP 1058442) and supported by an Alexander von Humboldt Fellowship for experienced researchers. Members of the GMC were funded by the German Federal Ministry of Education and Research (Infrafrontier grant 01KX1012). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.