bims-mikwok 2023-04-02 papers

Issue of 2023–04–02
five papers selected by
Avinash N. Mukkala, University of Toronto

Acta Pharm Sin B. 2023 Mar;13(3): 1028-1035

Mitochondrial transplantation as a promising therapy for mitochondrial diseases.

Mitochondrial diseases are a group of inherited or acquired metabolic disorders caused by mitochondrial dysfunction which may affect almost all the organs in the body and present at any age. However, no satisfactory therapeutic strategies have been available for mitochondrial diseases so far. Mitochondrial transplantation is a burgeoning approach for treatment of mitochondrial diseases by recovery of dysfunctional mitochondria in defective cells using isolated functional mitochondria. Many models of mitochondrial transplantation in cells, animals, and patients have proved effective via various routes of mitochondrial delivery. This review presents different techniques used in mitochondrial isolation and delivery, mechanisms of mitochondrial internalization and consequences of mitochondrial transplantation, along with challenges for clinical application. Despite some unknowns and challenges, mitochondrial transplantation would provide an innovative approach for mitochondrial medicine.

Keywords: Ethical issue; Mitochondria; Mitochondrial delivery; Mitochondrial disease; Mitochondrial isolation; Mitochondrial storage; Mitochondrial transplantation; Mitochondrial transplantation rejection

DOI: https://doi.org/10.1016/j.apsb.2022.10.008

Cell Rep. 2023 Mar 31. pii: S2211-1247(23)00343-1. [Epub ahead of print]42(4): 112332

The mitochondrial protease OMA1 acts as a metabolic safeguard upon nuclear DNA damage.

Pablo Rivera-Mejías, Álvaro Jesús Narbona-Pérez, Lidwina Hasberg, Lara Kroczek, Amir Bahat, Steffen Lawo, Kat Folz-Donahue, Anna-Lena Schumacher, Sofia Ahola, Fiona Carola Mayer, Patrick Giavalisco, Hendrik Nolte, Sergio Lavandero, Thomas Langer.

The metabolic plasticity of mitochondria ensures cell development, differentiation, and survival. The peptidase OMA1 regulates mitochondrial morphology via OPA1 and stress signaling via DELE1 and orchestrates tumorigenesis and cell survival in a cell- and tissue-specific manner. Here, we use unbiased systems-based approaches to show that OMA1-dependent cell survival depends on metabolic cues. A metabolism-focused CRISPR screen combined with an integrated analysis of human gene expression data found that OMA1 protects against DNA damage. Nucleotide deficiencies induced by chemotherapeutic agents promote p53-dependent apoptosis of cells lacking OMA1. The protective effect of OMA1 does not depend on OMA1 activation or OMA1-mediated OPA1 and DELE1 processing. OMA1-deficient cells show reduced glycolysis and accumulate oxidative phosphorylation (OXPHOS) proteins upon DNA damage. OXPHOS inhibition restores glycolysis and confers resistance against DNA damage. Thus, OMA1 dictates the balance between cell death and survival through the control of glucose metabolism, shedding light on its role in cancerogenesis.

Keywords: CP: Metabolism; DNA damage; OMA1; OXPHOS; glucose metabolism; mitochondria; nucleotides; p53

DOI: https://doi.org/10.1016/j.celrep.2023.112332

Annu Rev Biochem. 2023 Mar 31.

Mitochondrial DNA Release in Innate Immune Signaling.

Laura E Newman, Gerald S Shadel.

According to the endosymbiotic theory, most of the DNA of the original bacterial endosymbiont has been lost or transferred to the nucleus, leaving a much smaller (∼16 kb in mammals), circular molecule that is the present-day mitochondrial DNA (mtDNA). The ability of mtDNA to escape mitochondria and integrate into the nuclear genome was discovered in budding yeast, along with genes that regulate this process. Mitochondria have emerged as key regulators of innate immunity, and it is now recognized that mtDNA released into the cytoplasm, outside of the cell, or into circulation activates multiple innate immune signaling pathways. Here, we first review the mechanisms through which mtDNA is released into the cytoplasm, including several inducible mitochondrial pores and defective mitophagy or autophagy. Next, we cover how the different forms of released mtDNA activate specific innate immune nucleic acid sensors and inflammasomes. Finally, we discuss how intracellular and extracellular mtDNA release, including circulating cell-free mtDNA that promotes systemic inflammation, are implicated in human diseases, bacterial and viral infections, and senescence and aging. Expected final online publication date for the Annual Review of Biochemistry, Volume 92 is June 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

DOI: https://doi.org/10.1146/annurev-biochem-032620-104401

Biomedicines. 2023 Mar 20. pii: 948. [Epub ahead of print]11(3):

Preservation of Mitochondrial Health in Liver Ischemia/Reperfusion Injury.

Ivo F Machado, Carlos M Palmeira, Anabela P Rolo.

Liver ischemia-reperfusion injury (LIRI) is a major cause of the development of complications in different clinical settings such as liver resection and liver transplantation. Damage arising from LIRI is a major risk factor for early graft rejection and is associated with higher morbidity and mortality after surgery. Although the mechanisms leading to the injury of parenchymal and non-parenchymal liver cells are not yet fully understood, mitochondrial dysfunction is recognized as a hallmark of LIRI that exacerbates cellular injury. Mitochondria play a major role in glucose metabolism, energy production, reactive oxygen species (ROS) signaling, calcium homeostasis and cell death. The diverse roles of mitochondria make it essential to preserve mitochondrial health in order to maintain cellular activity and liver integrity during liver ischemia/reperfusion (I/R). A growing body of studies suggest that protecting mitochondria by regulating mitochondrial biogenesis, fission/fusion and mitophagy during liver I/R ameliorates LIRI. Targeting mitochondria in conditions that exacerbate mitochondrial dysfunction, such as steatosis and aging, has been successful in decreasing their susceptibility to LIRI. Studying mitochondrial dysfunction will help understand the underlying mechanisms of cellular damage during LIRI which is important for the development of new therapeutic strategies aimed at improving patient outcomes. In this review, we highlight the progress made in recent years regarding the role of mitochondria in liver I/R and discuss the impact of liver conditions on LIRI.

Keywords: aging; ischemia-reperfusion; liver; mitochondria; steatosis

DOI: https://doi.org/10.3390/biomedicines11030948

Nat Chem Biol. 2023 Mar 27.

Cytosolic and mitochondrial NADPH fluxes are independently regulated.

Xiangfeng Niu, Ethan Stancliffe, Susan J Gelman, Lingjue Wang, Michaela Schwaiger-Haber, Joe L Rowles, Leah P Shriver, Gary J Patti.

Although nicotinamide adenine dinucleotide phosphate (NADPH) is produced and consumed in both the cytosol and mitochondria, the relationship between NADPH fluxes in each compartment has been difficult to assess due to technological limitations. Here we introduce an approach to resolve cytosolic and mitochondrial NADPH fluxes that relies on tracing deuterium from glucose to metabolites of proline biosynthesis localized to either the cytosol or mitochondria. We introduced NADPH challenges in either the cytosol or mitochondria of cells by using isocitrate dehydrogenase mutations, administering chemotherapeutics or with genetically encoded NADPH oxidase. We found that cytosolic challenges influenced NADPH fluxes in the cytosol but not NADPH fluxes in mitochondria, and vice versa. This work highlights the value of using proline labeling as a reporter system to study compartmentalized metabolism and reveals that NADPH homeostasis in the cytosolic and mitochondrial locations of a cell are independently regulated, with no evidence for NADPH shuttle activity.

DOI: https://doi.org/10.1038/s41589-023-01283-9