Mitoregulin: A lncRNA-Encoded Microprotein that Supports Mitochondrial Supercomplexes and Respiratory Efficiency

Publication date: 26 June 2018
Source:Cell Reports, Volume 23, Issue 13
Author(s): Colleen S. Stein, Pooja Jadiya, Xiaoming Zhang, Jared M. McLendon, Gabrielle M. Abouassaly, Nathan H. Witmer, Ethan J. Anderson, John W. Elrod, Ryan L. Boudreau
Mitochondria are composed of many small proteins that control protein synthesis, complex assembly, metabolism, and ion and reactive oxygen species (ROS) handling. We show that a skeletal muscle- and heart-enriched long non-coding RNA, LINC00116, encodes a highly conserved 56-amino-acid microprotein that we named mitoregulin (Mtln). Mtln localizes to the inner mitochondrial membrane, where it binds cardiolipin and influences protein complex assembly. In cultured cells, Mtln overexpression increases mitochondrial membrane potential, respiration rates, and Ca²⁺ retention capacity while decreasing mitochondrial ROS and matrix-free Ca²⁺. Mtln-knockout mice display perturbations in mitochondrial respiratory (super)complex formation and activity, fatty acid oxidation, tricarboxylic acid (TCA) cycle enzymes, and Ca²⁺ retention capacity. Blue-native gel electrophoresis revealed that Mtln co-migrates alongside several complexes, including the complex I assembly module, complex V, and supercomplexes. Under denaturing conditions, Mtln remains in high-molecular-weight complexes, supporting its role as a sticky molecular tether that enhances respiratory efficiency by bolstering protein complex assembly and/or stability.

Graphical abstract

Teaser

Stein et al. show that the long non-coding RNA LINC00116 encodes a highly conserved single-pass transmembrane protein named mitoregulin (Mtln). Studies in cells and mice demonstrate that Mtln localizes to inner mitochondrial membranes, where it interacts with several complexes to influence mitochondrial membrane potential, respiration, Ca²⁺ retention capacity, ROS, and supercomplex levels.


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