bims-cytox1 2025-06-22 papers

Mol Biochem Parasitol. 2025 Jun 18. pii: S0166-6851(25)00023-4. [Epub ahead of print] 111687

Identification and initial characterisation of Trypanosoma Cox17 copper metallochaperone.

Murtala Bindawa Isah, Mwenya Chitembusha Kwangu, J P Dean Goldring, Theresa H T Coetzer.

Copper plays an essential role in organisms as a catalytic co-factor for key enzymes like cytochrome c oxidase. Copper importation, distribution and secretion is carried out by copper transport and copper-binding proteins known as copper chaperones. Cox17 is a chaperone that conveys copper to Cox11 and Sco1 for metalation of the CuB and CuA of Cox1 and Cox2 respectively in eukaryotes. Cox17 from Trypanosoma brucei brucei and T. congolense were recombinantly expressed and affinity purified as MBP-fusion proteins. An ascorbic acid oxidation assay, a BCA-release assay and an in vivo growth inhibition assay confirmed the presence of copper bound to the proteins. Trypanosomal Cox17 and other copper-binding proteins are expressed at higher levels in the insect procyclic stage where cytochrome c oxidase is active, compared to the bovine bloodstream forms. In silico docking models suggests possible interaction partners for Cox17.

Keywords: Animal African Trypanosomiasis; Copper-binding; Cox17; Trypanosoma

DOI: https://doi.org/10.1016/j.molbiopara.2025.111687

EMBO J. 2025 Jun 16.

Dysfunctional mitochondria trap proteins in the intermembrane space.

Tamara Flohr, Markus Räschle, Johannes M Herrmann.

The accumulation of mitochondrial precursor proteins in the cytosol due to mitochondrial dysfunction compromises cellular proteostasis and is a hallmark of diseases. Why non-imported precursors are toxic and how eukaryotic cells prevent their accumulation in the cytosol is still poorly understood. Using a proximity labeling-based assay to globally monitor the intramitochondrial location of proteins, we show that, upon mitochondrial dysfunction, many mitochondrial matrix proteins are sequestered in the intermembrane space (IMS); something we refer to as "mitochondrial triage of precursor proteins" (MitoTraP). MitoTraP is not simply the result of a general translocation block at the level of the inner membrane, but specifically directs a subgroup of matrix proteins into the IMS, many of which are constituents of the mitochondrial ribosome. Using the mitoribosomal protein Mrp17 (bS6m) as a model, we found that IMS sequestration prevents its mistargeting to the nucleus, potentially averting interference with assembly of cytosolic ribosomes. Thus, MitoTraP represents a novel, so far unknown mechanism of the eukaryotic quality control system that protects the cellular proteome against the toxic effects of non-imported mitochondrial precursor proteins.

Keywords: Intermembrane Space; Mitochondria; Nucleolus; Protein Targeting; Ribosome

DOI: https://doi.org/10.1038/s44318-025-00486-1

Life Sci Alliance. 2025 Sep;pii: e202403082. [Epub ahead of print]8(9):

Transcription arrest induces formation of RNA granules in mitochondria.

Katja G Hansen, Autum Baxter-Koenigs, Caroline Am Weiss, Erik McShane, L Stirling Churchman.

Mitochondrial gene expression regulation is required for the biogenesis of oxidative phosphorylation (OXPHOS) complexes, yet the spatial organization of mitochondrial RNAs (mt-RNAs) remains unknown. Here, we investigated the spatial distribution of mt-RNAs during various cellular stresses using single-molecule RNA-FISH. We discovered that transcription inhibition leads to the formation of distinct RNA granules within mitochondria, which we term inhibition granules. These structures differ from canonical mitochondrial RNA granules and form in response to multiple transcription arrest conditions, including ethidium bromide treatment, specific inhibition or stalling of the mitochondrial RNA polymerase, and depletion of the SUV3 helicase. Inhibition granules appear to stabilize certain mt-mRNAs during prolonged transcription inhibition. This phenomenon coincides with an imbalance in OXPHOS complex expression, where mitochondrial-encoded transcripts decrease while nuclear-encoded subunits remain stable. We found that cells recover from transcription inhibition via resolving the granules, restarting transcription, and repopulating the mitochondrial network with mt-mRNAs within hours. We suggest that inhibition granules may act as a reservoir to help overcome OXPHOS imbalance during recovery from transcription arrest.

DOI: https://doi.org/10.26508/lsa.202403082