bims-mitper Biomed News
on Mitochondrial Permeabilization
Issue of 2023–03–12
seven papers selected by
Bradley Irizarry, Thomas Jefferson University
  1. A protein bridge to death between the ER and mitochondria.
  2. SARS-COV-2 viroporins activate the NLRP3-inflammasome by the mitochondrial permeability transition pore.
  3. Fumarate induces vesicular release of mtDNA to drive innate immunity.
  4. Requirement for ER-mitochondria Ca2+ transfer, ROS production and mPTP formation in L-asparaginase-induced apoptosis of acute lymphoblastic leukemia cells.
  5. Study of the Bcl-2 Interactome by BiFC Reveals Differences in the Activation Mechanism of Bax and Bak.
  6. Plasma cell derived mtDAMPs activate macrophage STING pathway which promotes myeloma progression.
  7. Parkinson's Disease, Parkinsonisms, and Mitochondria: the Role of Nuclear and Mitochondrial DNA.
  1. J Biol Chem. 2023 Mar 03. pii: S0021-9258(23)00223-5. [Epub ahead of print] 104581
    A protein bridge to death between the ER and mitochondria.
    Jialing Lin.
      Commitment to apoptotic cell death occurs at the mitochondria, and is regulated by BCL-2 family proteins localized to this organelle. However, BIK, a resident protein of the endoplasmic reticulum inhibits mitochondrial BCL-2 proteins to promote apoptosis. In a recent paper in the JBC, Osterlund et al. investigated this conundrum. Surprisingly, they discovered that these endoplasmic reticulum and mitochondrial proteins moved toward each other and met at the contact site between the two organelles, thereby forming a 'bridge to death'.
    DOI:  https://doi.org/10.1016/j.jbc.2023.104581
  2. Front Immunol. 2023 ;14 1064293
    SARS-COV-2 viroporins activate the NLRP3-inflammasome by the mitochondrial permeability transition pore.
    Joseph W Guarnieri, Alessia Angelin, Deborah G Murdock, Patrick Schaefer, Prasanth Portluri, Timothy Lie, Jessica Huang, Douglas C Wallace.
       Background: Compared to healthy controls, severe COVID19 patients display increased levels of activated NLRP3-inflammasome (NLRP3-I) and interleukin (IL)-1β. SARS-CoV-2 encodes viroporin proteins E and Orf3a(2-E+2-3a) with homologs to SARS-CoV-1, 1-E+1-3a, which elevate NLRP3-I activation; by an unknown mechanism. Thus, we investigated how 2-E+2-3a activates the NLRP3-I to better understand the pathophysiology of severe COVID-19.
    Methods: We generated a polycistronic expression-vector co-expressing 2-E+2-3a from a single transcript. To elucidate how 2-E+2-3a activates the NLRP3-I, we reconstituted the NLRP3-I in 293T cells and used THP1-derived macrophages to monitor the secretion of mature IL-1β. Mitochondrial physiology was assessed using fluorescent microscopy and plate reader assays, and the release of mitochondrial DNA (mtDNA) was detected from cytosolic-enriched fractions using Real-Time PCR.
    Results: Expression of 2-E+2-3a in 293T cells increased cytosolic Ca++ and elevated mitochondrial Ca++, taken up through the MCUi11-sensitive mitochondrial calcium uniporter. Increased mitochondrial Ca++ stimulated NADH, mitochondrial reactive oxygen species (mROS) production and the release of mtDNA into the cytosol. Expression of 2-E+2-3a in NLRP3-I reconstituted 293T cells and THP1-derived macrophages displayed increased secretion of IL-1β. Increasing mitochondrial antioxidant defenses via treatment with MnTBAP or genetic expression of mCAT abolished 2-E+2-3a elevation of mROS, cytosolic mtDNA levels, and secretion of NLRP3-activated-IL-1β. The 2-E+2-3a-induced release of mtDNA and the secretion of NLRP3-activated-IL-1β were absent in cells lacking mtDNA and blocked in cells treated with the mitochondrial-permeability-pore(mtPTP)-specific inhibitor NIM811.
    Conclusion: Our findings revealed that mROS activates the release of mitochondrial DNA via the NIM811-sensitive mitochondrial-permeability-pore(mtPTP), activating the inflammasome. Hence, interventions targeting mROS and the mtPTP may mitigate the severity of COVID-19 cytokine storms.
    Keywords:  COVID-19; NLRP3-inflammasome; mitochondria in innate immune responses; mitochondrial permeability transition pore; viroporin
    DOI:  https://doi.org/10.3389/fimmu.2023.1064293
  3. Nature. 2023 Mar 08.
    Fumarate induces vesicular release of mtDNA to drive innate immunity.
    Vincent Zecchini, Vincent Paupe, Irene Herranz-Montoya, Joëlle Janssen, Inge M N Wortel, Jordan L Morris, Ashley Ferguson, Suvagata Roy Chowdury, Marc Segarra-Mondejar, Ana S H Costa, Gonçalo C Pereira, Laura Tronci, Timothy Young, Efterpi Nikitopoulou, Ming Yang, Dóra Bihary, Federico Caicci, Shun Nagashima, Alyson Speed, Kalliopi Bokea, Zara Baig, Shamith Samarajiwa, Maxine Tran, Thomas Mitchell, Mark Johnson, Julien Prudent, Christian Frezza.
      Mutations in fumarate hydratase (FH) cause hereditary leiomyomatosis and renal cell carcinoma1. Loss of FH in the kidney elicits several oncogenic signalling cascades through the accumulation of the oncometabolite fumarate2. However, although the long-term consequences of FH loss have been described, the acute response has not so far been investigated. Here we generated an inducible mouse model to study the chronology of FH loss in the kidney. We show that loss of FH leads to early alterations of mitochondrial morphology and the release of mitochondrial DNA (mtDNA) into the cytosol, where it triggers the activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING)-TANK-binding kinase 1 (TBK1) pathway and stimulates an inflammatory response that is also partially dependent on retinoic-acid-inducible gene I (RIG-I). Mechanistically, we show that this phenotype is mediated by fumarate and occurs selectively through mitochondrial-derived vesicles in a manner that depends on sorting nexin 9 (SNX9). These results reveal that increased levels of intracellular fumarate induce a remodelling of the mitochondrial network and the generation of mitochondrial-derived vesicles, which allows the release of mtDNAin the cytosol and subsequent activation of the innate immune response.
    DOI:  https://doi.org/10.1038/s41586-023-05770-w
  4. Front Cell Dev Biol. 2023 ;11 1124164
    Requirement for ER-mitochondria Ca2+ transfer, ROS production and mPTP formation in L-asparaginase-induced apoptosis of acute lymphoblastic leukemia cells.
    Jung Kwon Lee, Jesusa L Rosales, Ki-Young Lee.
      Acute lymphoblastic leukemia (aLL) is a malignant cancer in the blood and bone marrow characterized by rapid expansion of lymphoblasts. It is a common pediatric cancer and the principal basis of cancer death in children. Previously, we reported that L-asparaginase, a key component of acute lymphoblastic leukemia chemotherapy, causes IP3R-mediated ER Ca2+ release, which contributes to a fatal rise in [Ca2+]cyt, eliciting aLL cell apoptosis via upregulation of the Ca2+-regulated caspase pathway (Blood, 133, 2222-2232). However, the cellular events leading to the rise in [Ca2+]cyt following L-asparaginase-induced ER Ca2+ release remain obscure. Here, we show that in acute lymphoblastic leukemia cells, L-asparaginase causes mitochondrial permeability transition pore (mPTP) formation that is dependent on IP3R-mediated ER Ca2+ release. This is substantiated by the lack of L-asparaginase-induced ER Ca2+ release and loss of mitochondrial permeability transition pore formation in cells depleted of HAP1, a key component of the functional IP3R/HAP1/Htt ER Ca2+ channel. L-asparaginase induces ER Ca2+ transfer into mitochondria, which evokes an increase in reactive oxygen species (ROS) level. L-asparaginase-induced rise in mitochondrial Ca2+ and reactive oxygen species production cause mitochondrial permeability transition pore formation that then leads to an increase in [Ca2+]cyt. Such rise in [Ca2+]cyt is inhibited by Ruthenium red (RuR), an inhibitor of the mitochondrial calcium uniporter (MCU) that is required for mitochondrial Ca2+ uptake, and cyclosporine A (CsA), an mitochondrial permeability transition pore inhibitor. Blocking ER-mitochondria Ca2+ transfer, mitochondrial ROS production, and/or mitochondrial permeability transition pore formation inhibit L-asparaginase-induced apoptosis. Taken together, these findings fill in the gaps in our understanding of the Ca2+-mediated mechanisms behind L-asparaginase-induced apoptosis in acute lymphoblastic leukemia cells.
    Keywords:  L-asparaginase; acute lymphoblastic leukemia; blood-related disorders; chemotherapy; leukemia
    DOI:  https://doi.org/10.3389/fcell.2023.1124164
  5. Cells. 2023 Mar 03. pii: 800. [Epub ahead of print]12(5):
    Study of the Bcl-2 Interactome by BiFC Reveals Differences in the Activation Mechanism of Bax and Bak.
    Óscar Gonzalo, Andrea Benedi, Laura Vela, Alberto Anel, Javier Naval, Isabel Marzo.
      Evasion of apoptosis is one of the hallmarks of cancer cells. Proteins of the Bcl-2 family are key regulators of the intrinsic pathway of apoptosis, and alterations in some of these proteins are frequently found in cancer cells. Permeabilization of the outer mitochondrial membrane, regulated by pro- and antiapoptotic members of the Bcl-2 family of proteins, is essential for the release of apoptogenic factors leading to caspase activation, cell dismantlement, and death. Mitochondrial permeabilization depends on the formation of oligomers of the effector proteins Bax and Bak after an activation event mediated by BH3-only proteins and regulated by antiapoptotic members of the Bcl-2 family. In the present work, we have studied interactions between different members of the Bcl-2 family in living cells via the BiFC technique. Despite the limitations of this technique, present data suggest that native proteins of the Bcl-2 family acting inside living cells establish a complex network of interactions, which would fit nicely into "mixed" models recently proposed by others. Furthermore, our results point to differences in the regulation of Bax and Bak activation by proteins of the antiapoptotic and BH3-only subfamilies. We have also applied the BiFC technique to explore the different molecular models proposed for Bax and Bak oligomerization. Bax and Bak's mutants lacking the BH3 domain were still able to associate and give BiFC signals, suggesting the existence of alternative surfaces of interaction between two Bax or Bak molecules. These results agree with the widely accepted symmetric model for the dimerization of these proteins and also suggest that other regions, different from the α6 helix, could be involved in the oligomerization of BH3-in groove dimers.
    Keywords:  BH3-mimetics; Bcl-2 family; Bimolecular Fluorescence Complementation; apoptosis; protein–protein interactions
    DOI:  https://doi.org/10.3390/cells12050800
  6. Blood. 2023 Mar 08. pii: blood.2022018711. [Epub ahead of print]
    Plasma cell derived mtDAMPs activate macrophage STING pathway which promotes myeloma progression.
    Aisha Jibril, Charlotte Hellmich, Edyta Wojtowicz, Katherine Hampton, Rebecca S Maynard, Ravindu De Silva, Dominic J Fowler-Shorten, Jayna J Mistry, Jamie A Moore, Kristian M Bowles, Stuart A Rushworth.
      Mitochondrial damage-associated molecular patterns (mtDAMPs) include proteins, lipids, metabolites and DNA and have various context specific immunoregulatory functions. Cell-free mitochondrial DNA (mtDNA) is recognised via pattern recognition receptors and is a potent activator of the innate immune system. Cell-free mtDNA is elevated in the circulation of trauma and cancer patients, however the functional consequences of elevated mtDNA are largely undefined. Multiple myeloma (MM) relies upon cellular interactions within the bone marrow (BM) microenvironment for survival and progression. Here, using in-vivo models, we describe the role of MM cell derived mtDAMPs in the pro-tumoral BM microenvironment, and the mechanism and functional consequence of mtDAMPs in myeloma disease progression. Initially, we identified elevated levels of mtDNA in the peripheral blood serum of MM patients compared to healthy controls. Using the MM1S cells engrafted into NSG mice we established that elevated mtDNA was derived from MM cells. We further show that BM macrophages sense and respond to mtDAMPs through the STING pathway and inhibition of this pathway reduces MM tumor-burden in the KaLwRij-5TGM1 mouse model. Moreover, we found that MM derived mtDAMPs induced upregulation of chemokine signatures in BM macrophages and inhibition of this signature resulted in egress of MM cells from the BM. Here, we demonstrate that malignant plasma cells release mtDNA, a form of mtDAMPs, into the myeloma BM microenvironment, which in turn activates macrophages via STING signalling. We establish the functional role of these mtDAMP-activated macrophages in promoting disease progression and retaining MM cells in the pro-tumoral BM microenvironment.
    DOI:  https://doi.org/10.1182/blood.2022018711
  7. Curr Neurol Neurosci Rep. 2023 Mar 07.
    Parkinson's Disease, Parkinsonisms, and Mitochondria: the Role of Nuclear and Mitochondrial DNA.
    A Legati, D Ghezzi.
       PURPOSE OF REVIEW: Overwhelming evidence indicates that mitochondrial dysfunction is a central factor in Parkinson's disease (PD) pathophysiology. This paper aims to review the latest literature published, focusing on genetic defects and expression alterations affecting mitochondria-associated genes, in support of their key role in PD pathogenesis.
    RECENT FINDINGS: Thanks to the use of new omics approaches, a growing number of studies are discovering alterations affecting genes with mitochondrial functions in patients with PD and parkinsonisms. These genetic alterations include pathogenic single-nucleotide variants, polymorphisms acting as risk factors, and transcriptome modifications, affecting both nuclear and mitochondrial genes. We will focus on alterations of mitochondria-associated genes described by studies conducted on patients or on animal/cellular models of PD or parkinsonisms. We will comment how these findings can be taken into consideration for improving the diagnostic procedures or for deepening our knowledge on the role of mitochondrial dysfunctions in PD.
    Keywords:  Mitochondria; Mitochondrial DNA; Nuclear DNA; Omics; Parkinsonism; Parkinson’s disease
    DOI:  https://doi.org/10.1007/s11910-023-01260-8
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