bims-miptne 2025-06-15 papers

Trends Pharmacol Sci. 2025 Jun 10. pii: S0165-6147(25)00100-2. [Epub ahead of print]

At last: the mitochondrial pyruvate carrier structure revealed!

Brian N Finck, Christy M Hadfield, Kyle S McCommis.

Mitochondrial pyruvate carrier (MPC) inhibitors have shown promise as therapeutics for treating several chronic diseases. However, the structure of MPC and the molecular mechanisms by which it interacts with inhibitors have remained unclear, impeding rational drug design. Multiple groups have now independently resolved the structure of the MPC heterodimer.

Keywords: MPC; cryoEM; mitochondria; pyruvate

DOI: https://doi.org/10.1016/j.tips.2025.05.010

Front Synaptic Neurosci. 2025 ;17 1562065

Differential Ca2+ handling by isolated synaptic and non-synaptic mitochondria: roles of Ca2+ buffering and efflux.

Jyotsna Mishra, Kyle Bevers, Keguo Li, Armaan Zare, James S Heisner, Ailing Tong, Wai-Meng Kwok, David F Stowe, Amadou K S Camara.

Mitochondria regulate intracellular calcium ion (Ca2+) signaling by a fine-tuned process of mitochondrial matrix (m) Ca2+ influx, mCa2+ buffering (sequestration) and mCa2+ release (Ca2+ efflux). This process is critically important in the neurosynaptic terminal, where there is a simultaneous high demand for ATP utilization, cytosolic (c) Ca2+ regulation, and maintenance of ionic gradients across the cell membrane. Brain synaptic and non-synaptic mitochondria display marked differences in Ca2+ retention capacity. We hypothesized that mitochondrial Ca2+ handling in these two mitochondrial populations is determined by the net effects of Ca2+ uptake, buffering or efflux with increasing CaCl2 boluses. We found first that synaptic mitochondria have a more coupled respiration than non-synaptic mitochondria; this may correlate with the higher local energy demand in synapses to support neurotransmission. When both mitochondrial fractions were exposed to increasing mCa2+ loads we observed decreased mCa2+ sequestration in synaptic mitochondria as assessed by a significant increase in the steady-state free extra matrix Ca2+ (ss[Ca2+]e) compared to non-synaptic mitochondria. Since, non-synaptic mitochondria displayed a significantly reduced ss[Ca2+]e, this suggested a larger mCa2+ buffering capacity to maintain [Ca2+]m with increasing mCa2+ loads. There were no differences in the magnitude of the transient depolarizations and repolarizations of the membrane potential (ΔΨm) and both fractions exhibited similar gradual depolarization of the baseline ΔΨm during additional CaCl2 boluses. Adding the mitochondrial Na+/Ca2+ exchanger (mNCE) inhibitor CGP37157 to the mitochondrial suspensions unmasked the mCa2+ sequestration and concomitantly lowered ss[Ca2+]e in synaptic vs. non-synaptic mitochondria. Adding complex V inhibitor oligomycin plus ADP (OMN + ADP) bolstered the matrix Ca2+ buffering capacity in synaptic mitochondria, as did Cyclosporin A (CsA), in non-synaptic. Our results display distinct differences in regulation of the free [Ca2+]m to prevent collapse of ΔΨm during mCa2+ overload in the two populations of mitochondria. Synaptic mitochondria appear to rely mainly on mCa2+ efflux via mNCE, while non-synaptic mitochondria rely mainly on Pi-dependent mCa2+ sequestration. The functional implications of differential mCa2+ handling at neuronal synapses may be adaptations to cope with the higher metabolic activity and larger mCa2+ transients at synaptosomes, reflecting a distinct role they play in brain function.

Keywords: Ca2+ buffering; Ca2+ efflux; bioenergetics; non-synaptic mitochondria; synaptic mitochondria

DOI: https://doi.org/10.3389/fnsyn.2025.1562065

Cell Death Discov. 2025 Jun 10. 11(1): 273

CYPD limits HR+ mammary carcinogenesis in mice.

Aitziber Buqué, Manuel Beltrán-Visiedo, Ai Sato, Claudia Galassi, Giulia Petroni, Lorenzo Galluzzi.

Mitochondrial permeability transition (MPT)-driven necrosis and necroptosis are regulated variants of cell death that can drive inflammation or even promote antigen-specific immune responses. In oncological settings, indolent inflammatory reactions have been consistently associated with accelerated disease progression and resistance to treatment. Conversely, adaptive immune responses specific for tumor-associated antigens are generally restraining tumor development and contribute to treatment sensitivity. Here, we harnessed female C57BL/6J mice lacking key regulators of MPT-driven necrosis and necroptosis to investigate whether whole-body defects in these pathways would influence mammary carcinogenesis as driven by subcutaneous slow-release medroxyprogesterone acetate (MPA, M) pellets plus orally administered 7,12-dimethylbenz[a]anthracene (DMBA, D), an in vivo model that recapitulates multiple facets of the biology and immunology of human hormone receptor positive (HR+) breast cancer. Our data demonstrate that female mice bearing a whole-body, homozygous deletion in peptidylprolyl isomerase F (Ppif), which encodes a key regulator of MPT-driven necrosis commonly known as CYPD, but not female mice with systemic defects in necroptosis as imposed by the whole body-deletion homozygous of receptor-interacting serine-threonine kinase 3 (Ripk3) or mixed lineage kinase domain like pseudokinase (Mlkl), are more susceptible to M/D-driven carcinogenesis than their wild-type counterparts. These findings point to CYPD as to an oncosuppressive protein that restrains HR+ mammary carcinogenesis in mice, at least potentially via MPT-driven necrosis.

DOI: https://doi.org/10.1038/s41420-025-02555-0

Biochim Biophys Acta Mol Cell Res. 2025 Jun 06. pii: S0167-4889(25)00103-X. [Epub ahead of print] 119998

Impact of PARL-mediated mitochondrial protease activity on calcium regulation.

Donato D'Angelo, Aya Al Saidi, Giorgia Ghirardo, Denis Vecellio Reane, Nicola Gasparini, Rosario Rizzuto, Anna Raffaello.

The presenilin-associated rhomboid-like protein (PARL) is a mitochondrial inner membrane serine protease that is a key regulator of several cellular processes, including apoptosis, metabolism, inflammation and stress responses. While recent studies suggest that PARL may play a role in mitochondrial calcium homeostasis, the underlying mechanisms remain poorly understood. In this study, we investigated the effects of PARL modulation on mitochondrial and cytosolic calcium dynamics, as well as mitochondrial membrane potential. Our results show that altering PARL protein levels, through both overexpression and silencing, significantly affects mitochondrial calcium uptake, without influencing cytosolic calcium transients or mitochondrial membrane potential. Despite the observed changes in mitochondrial calcium dynamics, PARL does not interact with the mitochondrial calcium uniporter complex (mtCU) regulators MICU1 and MICU2, which are critical for regulating mitochondrial calcium influx. However, we observed alterations in the protein levels of MICU1 and MICU2, either in their monomeric or dimeric forms, suggesting that PARL may influence these mtCU components indirectly. Interestingly, the pore-forming subunit MCU, and the structural subunit EMRE, essential for the assembly of the mtCU, were unaffected by PARL modulation. These findings suggest that the role of PARL in modulating mitochondrial calcium homeostasis may involve indirect mechanisms, potentially involving other regulatory pathways. Overall, our study provides novel insights into the functional role of PARL in mitochondrial calcium regulation, offering potential avenues for further investigation into its broader cellular functions.

Keywords: Calcium signaling; Mitochondria; Mitochondrial calcium uniporter; Mitochondrial intermembrane proteolysis; PARL; Rhomboid protease

DOI: https://doi.org/10.1016/j.bbamcr.2025.119998

Nature. 2025 Jun 11.

Glycosaminoglycan-driven lipoprotein uptake protects tumours from ferroptosis.

Lipids are essential components of cancer cells due to their structural and signalling roles1. To meet metabolic demands, many cancers take up extracellular lipids2-5; however, how these lipids contribute to cancer growth and progression remains poorly understood. Here, using functional genetic screens, we identify uptake of lipoproteins-the primary mechanism for lipid transport in circulation-as a key determinant of ferroptosis sensitivity in cancer. Lipoprotein supplementation robustly inhibits ferroptosis across diverse cancer types, primarily through the delivery of α-tocopherol (α-toc), the most abundant form of vitamin E in human lipoproteins. Mechanistically, cancer cells take up lipoproteins through a pathway dependent on sulfated glycosaminoglycans (GAGs) linked to cell-surface proteoglycans. Disrupting GAG biosynthesis or acutely degrading surface GAGs reduces lipoprotein uptake, sensitizes cancer cells to ferroptosis and impairs tumour growth in mice. Notably, human clear cell renal cell carcinomas-a lipid-rich malignancy-exhibit elevated levels of chondroitin sulfate and increased lipoprotein-derived α-toc compared with normal kidney tissue. Together, our study establishes lipoprotein uptake as a critical anti-ferroptotic mechanism in cancer and implicates GAG biosynthesis as a therapeutic target.

DOI: https://doi.org/10.1038/s41586-025-09162-0

Nature. 2025 Jun 11.

Mitochondrial molecule has unexpected role in tissue healing.

Ram P Chakrabarty, Navdeep S Chandel.

Keywords: Biochemistry; Cell biology; Metabolism; Stem cells

DOI: https://doi.org/10.1038/d41586-025-01583-1