bims-smemid 2024-02-25 papers

on Stress metabolism in mitochondrial dysfunction

Issue of 2024–02–25
six papers selected by
Deepti Mudartha, The International Institute of Molecular Mechanisms and Machines

Using cryo-EM to understand the assembly pathway of respiratory complex I.
Serine mistranslation induces the integrated stress response without accumulation of uncharged tRNAs.
Pathological Interplay between Inflammation and Mitochondria Aggravates Glutamate Toxicity.
High-Fat Diet-Induced Obesity Increases Brain Mitochondrial Complex I and Lipoxidation-Derived Protein Damage.
Insertion of YFP at P5CS1 and AFL1 shows the potential, and potential complications, of gene tagging for functional analyses of stress-related proteins.
ATF4 in cellular stress, ferroptosis, and cancer.

Acta Crystallogr D Struct Biol. 2024 Mar 01.

Using cryo-EM to understand the assembly pathway of respiratory complex I.

Eike Laube, Jonathan Schiller, Volker Zickermann, Janet Vonck.

  Complex I (proton-pumping NADH:ubiquinone oxidoreductase) is the first component of the mitochondrial respiratory chain. In recent years, high-resolution cryo-EM studies of complex I from various species have greatly enhanced the understanding of the structure and function of this important membrane-protein complex. Less well studied is the structural basis of complex I biogenesis. The assembly of this complex of more than 40 subunits, encoded by nuclear or mitochondrial DNA, is an intricate process that requires at least 20 different assembly factors in humans. These are proteins that are transiently associated with building blocks of the complex and are involved in the assembly process, but are not part of mature complex I. Although the assembly pathways have been studied extensively, there is limited information on the structure and molecular function of the assembly factors. Here, the insights that have been gained into the assembly process using cryo-EM are reviewed.

Keywords:  assembly factors; complex I assembly; proton-pumping NADH ubiquinone oxidoreductase; respiratory complex I; single-particle cryo-EM

DOI:  https://doi.org/10.1107/S205979832400086X
bioRxiv. 2024 Feb 08. pii: 2024.02.04.578812. [Epub ahead of print]

Serine mistranslation induces the integrated stress response without accumulation of uncharged tRNAs.

Hong Zhang, Jiqiang Ling.

Aminoacyl-tRNA synthetases (aaRSs) are essential enzymes that support robust and accurate protein synthesis. A rapidly expanding number of studies show that mutations in aaRSs lead to multiple human diseases, including neurological disorders and cancer. Much remains unknown about how aaRS mutations impact human health. In particular, how aminoacylation errors affect stress responses and fitness in eukaryotic cells remains poorly understood. The integrated stress response (ISR) is an adaptive mechanism in response to multiple stresses. However, chronic activation of the ISR contributes to the development of multiple diseases (e.g., neuropathies). Here we show that Ser misincorporation into Ala and Thr codons, resulting from aaRS editing defects or mutations in tRNAs, constitutively active the ISR. Such activation does not appear to depend on the accumulation of uncharged tRNAs, implicating that Ser mistranslation may lead to ribosome stalling and collision.

DOI: https://doi.org/10.1101/2024.02.04.578812
Int J Mol Sci. 2024 Feb 14. pii: 2276. [Epub ahead of print]25(4):

Pathological Interplay between Inflammation and Mitochondria Aggravates Glutamate Toxicity.

Annette Vaglio-Garro, Andrey V Kozlov, Yuliya D Smirnova, Adelheid Weidinger.

  Mitochondrial dysfunction and glutamate toxicity are associated with neural disorders, including brain trauma. A review of the literature suggests that toxic and transmission actions of neuronal glutamate are spatially and functionally separated. The transmission pathway utilizes synaptic GluN2A receptors, rapidly released pool of glutamate, evoked release of glutamate mediated by Synaptotagmin 1 and the amount of extracellular glutamate regulated by astrocytes. The toxic pathway utilizes extrasynaptic GluN2B receptors and a cytoplasmic pool of glutamate, which results from the spontaneous release of glutamate mediated by Synaptotagmin 7 and the neuronal 2-oxoglutarate dehydrogenase complex (OGDHC), a tricarboxylic acid (TCA) cycle enzyme. Additionally, the inhibition of OGDHC observed upon neuro-inflammation is due to an excessive release of reactive oxygen/nitrogen species by immune cells. The loss of OGDHC inhibits uptake of glutamate by mitochondria, thus facilitating its extracellular accumulation and stimulating toxic glutamate pathway without affecting transmission. High levels of extracellular glutamate lead to dysregulation of intracellular redox homeostasis and cause ferroptosis, excitotoxicity, and mitochondrial dysfunction. The latter affects the transmission pathway demanding high-energy supply and leading to cell death. Mitochondria aggravate glutamate toxicity due to impairments in the TCA cycle and become a victim of glutamate toxicity, which disrupts oxidative phosphorylation. Thus, therapies targeting the TCA cycle in neurological disorders may be more efficient than attempting to preserve mitochondrial oxidative phosphorylation.

Keywords:  TCA cycle; ferroptosis; glutamate; mitochondrial dysfunction; neuronal death

DOI:  https://doi.org/10.3390/ijms25042276
Antioxidants (Basel). 2024 Jan 26. pii: 161. [Epub ahead of print]13(2):

High-Fat Diet-Induced Obesity Increases Brain Mitochondrial Complex I and Lipoxidation-Derived Protein Damage.

Rebeca Berdún, Èlia Obis, Natàlia Mota-Martorell, Anna Bassols, Daniel Valent, José C E Serrano, Meritxell Martín-Garí, María Rodríguez-Palmero, José Antonio Moreno-Muñoz, Joan Tibau, Raquel Quintanilla, Reinald Pamplona, Manuel Portero-Otín, Mariona Jové.

  Obesity is a risk factor for highly prevalent age-related neurodegenerative diseases, the pathogenesis of whichinvolves mitochondrial dysfunction and protein oxidative damage. Lipoxidation, driven by high levels of peroxidizable unsaturated fatty acids and low antioxidant protection of the brain, stands out as a significant risk factor. To gain information on the relationship between obesity and brain molecular damage, in a porcine model of obesity we evaluated (1) the level of mitochondrial respiratory chain complexes, as the main source of free radical generation, by Western blot; (2) the fatty acid profile by gas chromatography; and (3) the oxidative modification of proteins by mass spectrometry. The results demonstrate a selectively higher amount of the lipoxidation-derived biomarker malondialdehyde-lysine (MDAL) (34% increase) in the frontal cortex, and positive correlations between MDAL and LDL levels and body weight. No changes were observed in brain fatty acid profile by the high-fat diet, and the increased lipid peroxidative modification was associated with increased levels of mitochondrial complex I (NDUFS3 and NDUFA9 subunits) and complex II (flavoprotein). Interestingly, introducing n3 fatty acids and a probiotic in the high-fat diet prevented the observed changes, suggesting that dietary components can modulate protein oxidative modification at the cerebral level and opening new possibilities in neurodegenerative diseases' prevention.

Keywords:  age-related neurodegenerative diseases; lipoxidation; mitochondrial complexes; n3 PUFA; obesity; probiotics

DOI:  https://doi.org/10.3390/antiox13020161
Plant Cell Environ. 2024 Feb 23.

Insertion of YFP at P5CS1 and AFL1 shows the potential, and potential complications, of gene tagging for functional analyses of stress-related proteins.

Toshisangba Longkumer, Louis Grillet, Hao-Yi Chang, Tài Chiến Lường, Chih-Yun Chen, Hadi Putra, Wolfgang Schmidt, Paul E Verslues.

  Crispr/CAS9-enabled homologous recombination to insert a tag in frame with an endogenous gene can circumvent difficulties such as context-dependent promoter activity that complicate analysis of gene expression and protein accumulation patterns. However, there have been few reports examining whether such gene targeting/gene tagging (GT) can alter expression of the target gene. The enzyme encoded by Δ1 -pyrroline-5-carboxylate synthetase 1 (P5CS1) is key for stress-induced proline synthesis and drought resistance, yet its expression pattern and protein localisation have been difficult to assay. We used GT to insert YFP in frame with the 5' or 3' ends of the endogenous P5CS1 and At14a-Like 1 (AFL1) coding regions. Insertion at the 3' end of either gene generated homozygous lines with expression of the gene-YFP fusion indistinguishable from the wild type allele. However, for P5CS1 this occurred only after selfing and advancement to the T5 generation allowed initial homozygous lethality of the insertion to be overcome. Once this was done, the GT-generated P5CS1-YFP plants revealed new information about P5CS1 localisation and tissue-specific expression. In contrast, insertion of YFP at the 5' end of either gene blocked expression. The results demonstrate that GT can be useful for functional analyses of genes that are problematic to properly express by other means but also show that, in some cases, GT can disrupt expression of the target gene.

Keywords:  AFL1; Egg Cell1.1 (EC1.1) promoter; HypaCAS9; P5CS1; drought stress; gene tagging; gene targeting; proline; subcellular localisation

DOI:  https://doi.org/10.1111/pce.14861
Arch Toxicol. 2024 Feb 21.

ATF4 in cellular stress, ferroptosis, and cancer.

Hu Tang, Rui Kang, Jiao Liu, Daolin Tang.

  Activating transcription factor 4 (ATF4), a member of the ATF/cAMP response element-binding (CREB) family, plays a critical role as a stress-induced transcription factor. It orchestrates cellular responses, particularly in the management of endoplasmic reticulum stress, amino acid deprivation, and oxidative challenges. ATF4's primary function lies in regulating gene expression to ensure cell survival during stressful conditions. However, when considering its involvement in ferroptosis, characterized by severe lipid peroxidation and pronounced endoplasmic reticulum stress, the ATF4 pathway can either inhibit or promote ferroptosis. This intricate relationship underscores the complexity of cellular responses to varying stress levels. Understanding the connections between ATF4, ferroptosis, and endoplasmic reticulum stress holds promise for innovative cancer therapies, especially in addressing apoptosis-resistant cells. In this review, we provide an overview of ATF4, including its structure, modifications, and functions, and delve into its dual role in both ferroptosis and cancer.

Keywords:  ATF4; Cancer; Cellular stress; Ferroptosis

DOI:  https://doi.org/10.1007/s00204-024-03681-x