bims-mitran 2023-11-26 papers

bims-mitran

Biomed News

on Mitochondrial Translation

Issue of 2023–11–26
seven papers selected by
Andreas Kohler, Umeå University

Assessing the Role of Post-Translational Modifications of Mitochondrial RNA Polymerase.
Ribosome-targeting antibiotic control NLRP3-mediated inflammation by inhibiting mitochondrial DNA synthesis.
Exploring the Role of Mitochondrial Hydrogen Sulfide in Maintaining Polarity and mtDNA Integrity with a Multichannel Fluorescent Probe.
Enhanced C-To-T and A-To-G Base Editing in Mitochondrial DNA with Engineered DdCBE and TALED.
Mitochondrial DNA and Inflammation in Alzheimer's Disease.
Mitochondrial DNA Mutation Pathogenicity Score and Neurocognitive Performance in Persons with HIV.
Repurposing nucleoside reverse transcriptase inhibitors (NRTIs) to slow aging.

Int J Mol Sci. 2023 Nov 07. pii: 16050. [Epub ahead of print]24(22):

Assessing the Role of Post-Translational Modifications of Mitochondrial RNA Polymerase.

Karlie R Platz, Emma J Rudisel, Katelynn V Paluch, Taylor R Laurin, Kristin E Dittenhafer-Reed.

  The mitochondrial proteome is subject to abundant post-translational modifications, including lysine acetylation and phosphorylation of serine, threonine, and tyrosine. The biological function of the majority of these protein modifications is unknown. Proteins required for the transcription and translation of mitochondrial DNA (mtDNA) are subject to modification. This suggests that reversible post-translational modifications may serve as a regulatory mechanism for mitochondrial gene transcription, akin to mechanisms controlling nuclear gene expression. We set out to determine whether acetylation or phosphorylation controls the function of mitochondrial RNA polymerase (POLRMT). Mass spectrometry was used to identify post-translational modifications on POLRMT. We analyzed three POLRMT modification sites (lysine 402, threonine 315, threonine 993) found in distinct structural regions. Amino acid point mutants that mimic the modified and unmodified forms of POLRMT were employed to measure the effect of acetylation or phosphorylation on the promoter binding ability of POLRMT in vitro. We found a slight decrease in binding affinity for the phosphomimic at threonine 315. We did not identify large changes in viability, mtDNA content, or mitochondrial transcript level upon overexpression of POLRMT modification mimics in HeLa cells. Our results suggest minimal biological impact of the POLRMT post-translational modifications studied in our system.

Keywords:  acetylation; mitochondrial DNA; mitochondrial genome; mitochondrial proteins; phosphorylation; post-translational protein modification; transcription

DOI:  https://doi.org/10.3390/ijms242216050
Free Radic Biol Med. 2023 Nov 20. pii: S0891-5849(23)01115-2. [Epub ahead of print]210 75-84

Ribosome-targeting antibiotic control NLRP3-mediated inflammation by inhibiting mitochondrial DNA synthesis.

Suyuan Liu, Meiling Tan, Jiangxue Cai, Chenxuan Li, Miaoxin Yang, Xiaoxiao Sun, Bin He.

  While antibiotics are designed to target bacteria specifically, most are known to affect host cell physiology. Certain classes of antibiotics have been reported to have immunosuppressive effects, but the underlying mechanisms remain elusive. Here, we show that doxycycline, a ribosomal-targeting antibiotic, effectively inhibited both mitochondrial translation and nucleotide-binding domain and leucine-rich repeat-containing protein 3 (NLRP3) inflammasome-mediated caspase-1 activation and interleukin-1β (IL-1β) production in bone-marrow-derived macrophages (BMDMs). In addition, knockdown of mitochondrial methionyl-tRNA formyltransferase (Mtfmt), which is rate limiting for mitochondrial translation, also resulted in the inhibition of NLRP3 inflammasome-mediated caspase-1 activation and IL-1β secretion. Furthermore, both doxycycline treatment and Mtfmt knockdown blocked the synthesis of mitochondrial DNA (mtDNA) and the generation of oxidized mtDNA (Ox-mtDNA), which serves as a ligand for NLRP3 inflammasome activation. In addition, in vivo results indicated that doxycycline mitigated NLRP3 inflammasome-dependent inflammation, including lipopolysaccharide-induced systemic inflammation and endometritis. Taken together, the results unveil the antibiotics targeting the mitoribosome have the ability to mitigate NLRP3 inflammasome activation by inhibiting mitochondrial translation and mtDNA synthesis thus opening up new possibilities for the treatment of NLRP3-related diseases.

Keywords:  Doxycycline; Mitochondrial translation; NLRP3 inflammasome; mtDNA

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.11.014
Anal Chem. 2023 Nov 21.

Exploring the Role of Mitochondrial Hydrogen Sulfide in Maintaining Polarity and mtDNA Integrity with a Multichannel Fluorescent Probe.

Shuai Mu, Taihe Han, Xiaoyun Zhang, Jia Liu, Huipeng Sun, Jinlong Zhang, Xiaoyan Liu, Haixia Zhang.

Abnormal mitochondrial state has been implicated in the pathogenesis of various diseases including neurodegenerative disorders, myopathies, cardiovascular diseases, and cancers. Assessing mitochondrial functionality can be achieved by monitoring alterations in mitochondrial polarity and mitochondrial DNA (mtDNA) integrity, which serve as valuable biomarkers. Hydrogen sulfide (H2S), a gaseous signaling molecule, plays a regulatory role in mitochondrial respiratory chain activity, ATP synthesis, and calcium ion balance, thereby influencing cellular metabolism and signal transduction. Investigating the interplay between mitochondrial H2S, polarity, and mtDNA can enhance our understanding of the underlying regulatory mechanisms involved in H2S-mediated mitochondrial functions. To address this, we designed a mitochondria-targeted multichannel fluorescent probe, HNA, capable of cascaded detection of H2S and polarity, as well as parallel detection of mtDNA. The probe exhibited a significant turn-on response to H2S, emitting at approximately 604 nm, while the product HNAP demonstrated high sensitivity to polarity within the wavelength range of 526-591 nm. Additionally, the probe was able to bind to DNA, resulting in an enhanced long-wave emission at 668 nm. Facilitated by HNA, our study provides novel insights into the role of mitochondrial H2S in maintaining mitochondrial polarity and validates its protective effect on mtDNA through antioxidative mechanisms. Overall, this work proposes a potential therapeutic strategy for modulating the inflammatory process in mitochondrial-related diseases.

DOI: https://doi.org/10.1021/acs.analchem.3c03663
Adv Sci (Weinh). 2023 Nov 20. e2304113

Enhanced C-To-T and A-To-G Base Editing in Mitochondrial DNA with Engineered DdCBE and TALED.

Yinghui Wei, Ming Jin, Shuhong Huang, Fangyao Yao, Ningxin Ren, Kun Xu, Shangpu Li, Pengfei Gao, Yingsi Zhou, Yulin Chen, Hui Yang, Wen Li, Chunlong Xu, Meiling Zhang, Xiaolong Wang.

  Mitochondrial base editing with DddA-derived cytosine base editor (DdCBE) is limited in the accessible target sequences and modest activity. Here, the optimized DdCBE tools is presented with improved editing activity and expanded C-to-T targeting scope by fusing DddA11 variant with different cytosine deaminases with single-strand DNA activity. Compared to previous DdCBE based on DddA11 variant alone, fusion of the activation-induced cytidine deaminase (AID) from Xenopus laevis not only permits cytosine editing of 5'-GC-3' sequence, but also elevates editing efficiency at 5'-TC-3', 5'-CC-3', and 5'-GC-3' targets by up to 25-, 10-, and 6-fold, respectively. Furthermore, the A-to-G editing efficiency is significantly improved by fusing the evolved DddA6 variant with TALE-linked deoxyadenosine deaminase (TALED). Notably, the authors introduce the reported high-fidelity mutations in DddA and add nuclear export signal (NES) sequences in DdCBE and TALED to reduce off-target editing in the nuclear and mitochondrial genome while improving on-target editing efficiency in mitochondrial DNA (mtDNA). Finally, these engineered mitochondrial base editors are shown to be efficient in installing mtDNA mutations in human cells or mouse embryos for disease modeling. Collectively, the study shows broad implications for the basic study and therapeutic applications of optimized DdCBE and TALED.

Keywords:  DdCBE; TALED; disease modeling; mitochondrial base editing

DOI:  https://doi.org/10.1002/advs.202304113
Curr Issues Mol Biol. 2023 Oct 25. 45(11): 8586-8606

Mitochondrial DNA and Inflammation in Alzheimer's Disease.

Giacoma Galizzi, Marta Di Carlo.

  Mitochondrial dysfunction and neuroinflammation are implicated in the pathogenesis of most neurodegenerative diseases, such as Alzheimer's disease (AD). In fact, although a growing number of studies show crosstalk between these two processes, there remain numerous gaps in our knowledge of the mechanisms involved, which requires further clarification. On the one hand, mitochondrial dysfunction may lead to the release of mitochondrial damage-associated molecular patterns (mtDAMPs) which are recognized by microglial immune receptors and contribute to neuroinflammation progression. On the other hand, inflammatory molecules released by glial cells can influence and regulate mitochondrial function. A deeper understanding of these mechanisms may help identify biomarkers and molecular targets useful for the treatment of neurodegenerative diseases. This review of works published in recent years is focused on the description of the mitochondrial contribution to neuroinflammation and neurodegeneration, with particular attention to mitochondrial DNA (mtDNA) and AD.

Keywords:  Alzheimer’s disease; DAMPs; glia; microglia; mitochondria; mitochondrial dysfunction; mtDNA; neurodegeneration; neuroinflammation

DOI:  https://doi.org/10.3390/cimb45110540
Mitochondrion. 2023 Nov 19. pii: S1567-7249(23)00091-0. [Epub ahead of print]

Mitochondrial DNA Mutation Pathogenicity Score and Neurocognitive Performance in Persons with HIV.

Karen E Volpe, David C Samuels, Joanna L Elson, Jannetta S Steyn, Tebeb Gebretsadik, Ronald J Ellis, Robert K Heaton, Asha R Kallianpur, Scott Letendre, Todd Hulgan.

   BACKGROUND: Mitochondrial DNA (mtDNA) genetic variation is associated with neurocognitive (NC) impairment (NCI) in people with HIV (PWH). Other approaches use sequence conservation and protein structure to predict the impact of mtDNA variants on protein function. We examined predicted mtDNA variant pathogenicity in the CHARTER study using MutPred scores, hypothesizing that persons with higher scores (greater predicted pathogenicity) have more NCI.
METHODS: CHARTER included NC testing in PWH from 2003-2007. MutPred scores were assigned to CHARTER participants with mtDNA sequence; any score >0.5 was considered potentially deleterious. Outcomes at cohort entry were NCI, defined by global and seven NC domain deficit scores, and by mean global and domain NC performance T-scores. Univariate and multivariable regression analyses assessed associations between having a deleterious variant and NCI. Additional models included estimated peripheral blood cell mtDNA copy number.
RESULTS: Data were available for 744 PWH (357 African ancestry; 317 European; 70 Hispanic). In the overall cohort, PWH having any potentially deleterious variant were less likely to have motor impairment (16 vs. 25%, p=0.001). In multivariable analysis, having a deleterious variant remained associated with lower likelihood of motor impairment (adjusted odds ratio 0.59 [95% CI 0.41-0.88]; p=0.009), and better motor performance by T-score (β 1.71 [0.31-3.10], p=0.02). Associations persisted after adjustment for estimated mtDNA quantity.
CONCLUSIONS: In these PWH, having a potentially deleterious mtDNA variant was associated with less motor impairment. These unexpected findings suggest that potentially deleterious mtDNA variations may confer protection against impaired motor function by as yet unknown mechanisms.

Keywords:  DNA; HIV; Mitochondrial; deficits; neurologic

DOI:  https://doi.org/10.1016/j.mito.2023.11.003
Ageing Res Rev. 2023 Nov 19. pii: S1568-1637(23)00291-X. [Epub ahead of print]92 102132

Repurposing nucleoside reverse transcriptase inhibitors (NRTIs) to slow aging.

Thomas Brochard, Rebecca L McIntyre, Riekelt H Houtkooper, Andrei Seluanov, Vera Gorbunova, Georges E Janssens.

  Repurposing drugs already approved in the clinic to be used off-label as geroprotectors, compounds that combat mechanisms of aging, are a promising way to rapidly reduce age-related disease incidence in society. Several recent studies have found that a class of drugs-nucleoside reverse transcriptase inhibitors (NRTIs)-originally developed as treatments for cancers and human immunodeficiency virus (HIV) infection, could be repurposed to slow the aging process. Interestingly, these studies propose complementary mechanisms that target multiple hallmarks of aging. At the molecular level, NRTIs repress LINE-1 elements, reducing DNA damage, benefiting the hallmark of aging of 'Genomic Instability'. At the organellar level, NRTIs inhibit mitochondrial translation, activate ATF-4, suppress cytosolic translation, and extend lifespan in worms in a manner related to the 'Loss of Proteostasis' hallmark of aging. Meanwhile, at the cellular level, NRTIs inhibit the P2X7-mediated activation of the inflammasome, reducing inflammation and improving the hallmark of aging of 'Altered Intercellular Communication'. Future development of NRTIs for human aging health will need to balance out toxic side effects with the beneficial effects, which may occur in part through hormesis.

Keywords:  Aging; Geroprotectors; Intervention; Mitohormesis; NRTIs

DOI:  https://doi.org/10.1016/j.arr.2023.102132