bims-smemid Biomed News
on Stress metabolism in mitochondrial dysfunction
Issue of 2025–06–01
two papers selected by
Deepti Mudartha, The International Institute of Molecular Mechanisms and Machines
  1. The mitochondrial intermembrane space - a permanently proteostasis-challenged compartment.
  2. In vivo structure profiling reveals human cytosolic and mitochondrial tRNA structurome and interactome in response to stress.
  1. Biol Chem. 2025 May 27.
    The mitochondrial intermembrane space - a permanently proteostasis-challenged compartment.
    Matthias Weith, Konstantin Weiss, Dylan Stobbe, Jan Riemer.
      The mitochondrial intermembrane space (IMS) houses proteins essential for redox regulation, protein import, signaling, and energy metabolism. Protein import into the IMS is mediated by dedicated pathways, including the disulfide relay pathway for oxidative folding. In addition, various IMS-traversing import pathways potentially expose unfolded proteins, representing threats to proteostasis. This trafficking of precursors coincides with unique biophysical challenges in the IMS, including a confined volume, elevated temperature, variable pH and high levels of reactive oxygen species. Ultrastructural properties and import supercomplex formation ameliorate these challenges. Nonetheless, IMS proteostasis requires constant maintenance by chaperones, folding catalysts, and proteases to counteract misfolding and aggregation. The IMS plays a key role in stress signaling, where proteostasis disruptions trigger responses including the integrated stress response (ISR) activated by mitochondrial stress (ISRmt) and responses to cytosolic accumulation of mitochondrial protein precursors. This review explores the biology and mechanisms governing IMS proteostasis, presents models, which have been employed to decipher IMS-specific stress responses, and discusses open questions.
    Keywords:  IMS; mitochondria; protein import; proteostasis; stress responses
    DOI:  https://doi.org/10.1515/hsz-2025-0108
  2. Nat Commun. 2025 May 30. 16(1): 5041
    In vivo structure profiling reveals human cytosolic and mitochondrial tRNA structurome and interactome in response to stress.
    Noah Peña, Yichen Hou, Christopher P Watkins, Sihao Huang, Wen Zhang, Christopher D Katanski, Tao Pan.
      Transfer RNA (tRNA) is the most abundant cellular RNA family in terms of copy numbers. It not only folds into defined structures but also has complex cellular interaction networks involving aminoacyl-tRNA synthetases, translation factors, and ribosomes. The human tRNAome is comprised of chromosomal-encoded tRNAs with a large sequence diversity and mitochondrial-encoded tRNAs with A/U-rich sequences and noncanonical tertiary interactions. How tRNA folding and interactions in a eukaryotic cell respond to stress is poorly understood. Here, we develop DM-DMS-MaPseq, which utilizes in vivo dimethyl-sulfate (DMS) chemical probing and mutational profiling (MaP) coupled with demethylase (DM) treatment in transcriptome-wide tRNA sequencing to profile structures and the cellular interactions of human chromosomal and mitochondrial-encoded tRNAs. We found that tRNAs maintain stable structures in vivo, but the in vivo DMS profiles are vastly different from those in vitro, which can be explained by their interactions with cellular proteins and the ribosome. We also identify cytosolic and mitochondrial tRNA structure and interaction changes upon arsenite treatment, a type of oxidative stress that induces translational reprogramming, which is consistent with global translation repression in both compartments. Our results reveal variations of tRNA structurome and dynamic interactome that have functional consequences in translational regulation.
    DOI:  https://doi.org/10.1038/s41467-025-59435-5
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