bims-mitpro 2025-03-23 papers

Issue of 2025–03–23
five papers selected by
Andreas Kohler, Umeå University

J Cell Sci. 2025 Mar 19. pii: jcs.263576. [Epub ahead of print]

Definition of the human mitochondrial TOM interactome reveals TRABD as new interacting protein.

Metin Özdemir, Silke Oeljeklaus, Schendzielorz Alexander, Marcel Morgenstern, Anusha Valpadashi, Roya Yousefi, Bettina Warscheid, Sven Dennerlein.

The mitochondrial proteome arises from dual genetic origin. Nuclear-encoded proteins need to be transported across or inserted into two distinguished membranes, and the TOM complex represents the main translocase in the outer mitochondrial membrane. Its composition and regulations have been extensively investigated within yeast cells. However, we have little knowledge of the TOM complex composition within human cells. Here, we have defined the TOM interactome in a comprehensive manner using biochemical approaches to isolate the TOM complex in combination with quantitative mass spectrometry analyses. Within these studies, we defined the pleiotropic nature of the human TOM complex, including new interactors, such as TRABD. Our studies provide a framework to understand the various biogenesis pathways that merge at the TOM complex within human cells.

Keywords: Mitochondria; Mitochondrial Biogenesis; Mitochondrial protein import; Mitochondrial quality control; Protein transport; TOM complex

DOI: https://doi.org/10.1242/jcs.263576

Nat Rev Cardiol. 2025 Mar 20.

Mitochondrial quality control in cardiomyocytes: safeguarding the heart against disease and ageing.

Rishith Ravindran, Åsa B Gustafsson.

Mitochondria are multifunctional organelles that are important for many different cellular processes, including energy production and biosynthesis of fatty acids, haem and iron-sulfur clusters. Mitochondrial dysfunction leads to a disruption in these processes, the generation of excessive reactive oxygen species, and the activation of inflammatory and cell death pathways. The consequences of mitochondrial dysfunction are particularly harmful in energy-demanding organs such as the heart. Loss of terminally differentiated cardiomyocytes leads to cardiac remodelling and a reduced ability to sustain contraction. Therefore, cardiomyocytes rely on multilayered mitochondrial quality control mechanisms to maintain a healthy population of mitochondria. Mitochondrial chaperones protect against protein misfolding and aggregation, and resident proteases eliminate damaged proteins through proteolysis. Irreparably damaged mitochondria can also be degraded through mitochondrial autophagy (mitophagy) or ejected from cells inside vesicles. The accumulation of dysfunctional mitochondria in cardiomyocytes is a hallmark of ageing and cardiovascular disease. This accumulation is driven by impaired mitochondrial quality control mechanisms and contributes to the development of heart failure. Therefore, there is a strong interest in developing therapies that directly target mitochondrial quality control in cardiomyocytes. In this Review, we discuss the current knowledge of the mechanisms involved in regulating mitochondrial quality in cardiomyocytes, how these pathways are altered with age and in disease, and the therapeutic potential of targeting mitochondrial quality control pathways in cardiovascular disease.

DOI: https://doi.org/10.1038/s41569-025-01142-1

Curr Opin Cell Biol. 2025 Mar 20. pii: S0955-0674(25)00031-6. [Epub ahead of print]94 102493

Advances in mitophagy initiation mechanisms.

Catharina Küng, Michael Lazarou, Thanh Ngoc Nguyen.

Mitophagy is an important lysosomal degradative pathway that removes damaged or unwanted mitochondria to maintain cellular and organismal homeostasis. The mechanisms behind how mitophagy is initiated to form autophagosomes around mitochondria have gained a lot of interest since they can be potentially targeted by mitophagy-inducing therapeutics. Mitophagy initiation can be driven by various autophagy receptors or adaptors that respond to different cellular and mitochondrial stimuli, ranging from mitochondrial damage to metabolic rewiring. This review will cover recent advances in our understanding of how mitophagy is initiated, and by doing so reveal the mechanistic plasticity of how autophagosome formation can begin.

DOI: https://doi.org/10.1016/j.ceb.2025.102493

J Cell Biol. 2025 May 05. pii: e202408050. [Epub ahead of print]224(5):

TMBIM-2 orchestrates systemic mitochondrial stress response via facilitating Ca2+ oscillations.

Jiasheng Li, Jimeng Cui, Xinyu Li, Di Zhu, Zhenhua Chen, Xiahe Huang, Yingchun Wang, Qingfeng Wu, Ye Tian.

Neuronal mitochondrial function is critical for orchestrating inter-tissue communication essential for overall fitness. Despite its significance, the molecular mechanism underlying the impact of prolonged mitochondrial stresses on neuronal activity and how they orchestrate metabolism and aging remains elusive. Here, we identified the evolutionarily conserved transmembrane protein XBX-6/TMBIM-2 as a key mediator in the neuronal-to-intestinal mitochondrial unfolded protein response (UPRmt). Our investigations reveal that intrinsic neuronal mitochondrial stress triggers spatiotemporal Ca2+ oscillations in a TMBIM-2-dependent manner through the Ca2+ efflux pump MCA-3. Notably, persistent Ca2+ oscillations at synapses of ADF neurons are critical for facilitating serotonin release and the subsequent activation of the neuronal-to-intestinal UPRmt. TMBIM2 expression diminishes with age; however, its overexpression counteracts the age-related decline in aversive learning behavior and extends the lifespan of Caenorhabditis elegans. These findings underscore the intricate integration of chronic neuronal mitochondrial stress into neurotransmission processes via TMBIM-2-dependent Ca2+ equilibrium, driving metabolic adaptation and behavioral changes for the regulation of aging.

DOI: https://doi.org/10.1083/jcb.202408050

J Cell Sci. 2025 Mar 17. pii: jcs.263661. [Epub ahead of print]

The Mia40 substrate Mix17 exposes its N-terminus to the cytosolic side of the mitochondrial outer membrane.

Moritz Resch, Johanna S Frickel, Korbinian Dischinger, Rachel Choo Shen Wen, Kai Hell, Max E Harner.

Mitochondrial architecture and the contacts between the outer and the inner mitochondrial membrane depend on the mitochondrial contact site and cristae organizing system (MICOS) that is highly conserved from yeast to human. Mutations in the mammalian MICOS subunit Mic14/CHCHD10 have been linked to amyotrophic lateral sclerosis and frontotemporal dementia, indicating the importance of this protein. Mic14/CHCHD10 has a yeast ortholog, Mix17, a protein of unknown function, which has not been shown to interact with MICOS so far. As a first step to elucidate the function of Mix17 and its orthologs, we analyzed its interactions, biogenesis and mitochondrial sublocation. We report that Mix17 is no stable MICOS subunit in yeast. Our data suggest that Mix17 is the first Mia40 substrate in the mitochondrial outer membrane. Unlike all other Mia40 substrates, Mix17 spans the outer membrane and exposes its N-terminus to the cytosol. The insertion of Mix17 is likely to be mediated by its interaction with Tom40, the pore of the TOM complex. Moreover, we show that the exposure of Mix17 to the cytosolic side of the membrane depends on its N-terminus.

Keywords: CHCHD10; Mia40; Mic14; Mix17; Protein import; Tom40

DOI: https://doi.org/10.1242/jcs.263661