bims-mikwok 2023-12-17 papers

bims-mikwok

Biomed News

on Mitochondrial quality control

Issue of 2023–12–17
seventeen papers selected by
Gavin McStay, Liverpool John Moores University

GRAF1 integrates PINK1-Parkin signaling and actin dynamics to mediate cardiac mitochondrial homeostasis.
CMT2A-linked MFN2 mutation, T206I promotes mitochondrial hyperfusion and predisposes cells towards mitophagy.
Parkin-mediated mitophagy is a potential treatment for oxaliplatin-induced peripheral neuropathy.
A mitochondrial quality control mechanism reverses the phagosome maturation arrest caused by Mycobacterium tuberculosis.
Obesity worsens mitochondrial quality control and does not protect against skeletal muscle wasting in murine cancer cachexia.
ROS production by mitochondria: function or dysfunction?
Caveolin-1 promotes mitochondrial health and limits mitochondrial ROS through ROCK/AMPK regulation of basal mitophagic flux.
The critical roles of STING in mitochondrial homeostasis.
Butyrate reduces adherent-invasive E. coli-evoked disruption of epithelial mitochondrial morphology and barrier function: involvement of free fatty acid receptor 3.
Intraneuronal β-amyloid impaired mitochondrial proteostasis through the impact on LONP1.
"ATAD3C regulates ATAD3A assembly and function in the mitochondrial membrane".
Tom70-regulated mitochondrial biogenesis via TFAM improves hypoxia-induced dysfunction of pulmonary vascular endothelial cells and alleviates hypoxic pulmonary hypertension.
Mitochondrial temperature homeostasis resists external metabolic stresses.
Multiomics Reveals Induction of Neuroblastoma SK-N-BE(2)C Cell Death by Mitochondrial Division Inhibitor 1 through Multiple Effects.
Glycyrrhizin protects submandibular gland against radiation damage by enhancing antioxidant defense and preserving mitochondrial homeostasis.
Deep Proteomics reveals incorporation of unedited proteins into mitochondrial protein complexes in Arabidopsis.
Dihydroartemisinin suppresses glioma growth by repressing ERRα-mediated mitochondrial biogenesis.

Nat Commun. 2023 Dec 11. 14(1): 8187

GRAF1 integrates PINK1-Parkin signaling and actin dynamics to mediate cardiac mitochondrial homeostasis.

Qiang Zhu, Matthew E Combs, Juan Liu, Xue Bai, Wenbo B Wang, Laura E Herring, Jiandong Liu, Jason W Locasale, Dawn E Bowles, Ryan T Gross, Michelle Mendiola Pla, Christopher P Mack, Joan M Taylor.

The serine/threonine kinase, PINK1, and the E3 ubiquitin ligase, Parkin, are known to facilitate LC3-dependent autophagosomal encasement and lysosomal clearance of dysfunctional mitochondria, and defects in this process contribute to a variety of cardiometabolic and neurological diseases. Although recent evidence indicates that dynamic actin remodeling plays an important role in PINK1/Parkin-mediated mitochondrial autophagy (mitophagy), the underlying signaling mechanisms remain unknown. Here, we identify the RhoGAP GRAF1 (Arhgap26) as a PINK1 substrate that regulates mitophagy. GRAF1 promotes the release of damaged mitochondria from F-actin anchors, regulates mitochondrial-associated Arp2/3-mediated actin remodeling and facilitates Parkin-LC3 interactions to enhance mitochondria capture by autophagosomes. Graf1 phosphorylation on PINK1-dependent sites is dysregulated in human heart failure, and cardiomyocyte-restricted Graf1 depletion in mice blunts mitochondrial clearance and attenuates compensatory metabolic adaptations to stress. Overall, we identify GRAF1 as an enzyme that coordinates cytoskeletal and metabolic remodeling to promote cardioprotection.

DOI: https://doi.org/10.1038/s41467-023-43889-6
Mitochondrion. 2023 Dec 11. pii: S1567-7249(23)00105-8. [Epub ahead of print] 101825

CMT2A-linked MFN2 mutation, T206I promotes mitochondrial hyperfusion and predisposes cells towards mitophagy.

Rajdeep Das, Sebabrata Maity, Palamou Das, Izaz Monir Kamal, Saikat Chakrabarti, Oishee Chakrabarti.

Mutations in Mitofusin2 (MFN2) associated with the pathology of the debilitating neuropathy Charcot-Marie-Tooth type 2A (CMT2A) are known to alter mitochondrial morphology. Previously, such mutations have been shown to elicit two diametrically opposite phenotypes - while some mutations have been causally linked to enhanced mitochondrial fragmentation, others have been shown to induce hyperfusion. Our study identifies one such MFN2 mutant, T206I that causes mitochondrial hyperfusion. Cells expressing this MFN2 mutant have elongated and interconnected mitochondria. T206I-MFN2 mutation in the GTPase domain increases MFN2 stability and renders cells susceptible to stress. We show that cells expressing T206I-MFN2 have a higher predisposition towards mitophagy under conditions of serum starvation. We also detect increased DRP1 recruitment onto the outer mitochondrial membrane, though the total DRP1 protein level remains unchanged. Here we have characterized a lesser studied CMT2A-linked MFN2 mutant to show that its presence affects mitochondrial morphology and homeostasis.

DOI: https://doi.org/10.1016/j.mito.2023.101825
Am J Physiol Cell Physiol. 2023 Dec 11.

Parkin-mediated mitophagy is a potential treatment for oxaliplatin-induced peripheral neuropathy.

Guoqing Zhao, Te Zhang, Jiannan Li, Longyun Li, Peng Chen, Chunlu Zhang, Kai Li, Cancan Cui.

  Oxaliplatin-induced peripheral nerve pain (OIPNP) is a common chemotherapy-related complication, but the mechanism is complex. Mitochondria are vital for cellular homeostasis and regulating oxidative stress. Parkin-mediated mitophagy is a cellular process that removes damaged mitochondria, exhibiting a protective effect in various diseases; however, its role in OIPNP remains unclear. In this study, we found that Parkin-mediated mitophagy was decreased, and reactive oxygen species (ROS) was upregulated in OIPNP rat dorsal root ganglion (DRG) in vivo and in PC12 cells stimulated with oxaliplatin (OXA) in vitro. Overexpression of Parkin indicated that OXA might cause mitochondrial and cell damage by inhibiting mitophagy. We also showed that salidroside (SAL) upregulated Parkin-mediated mitophagy to eliminate damaged mitochondria and promote PC12 cell survival. Knockdown of Parkin indicated that mitophagy is crucial for apoptosis and mitochondrial homeostasis in PC12 cells. In vivo study also demonstrated that SAL enhances Parkin-mediated mitophagy in the DRG and alleviates peripheral nerve injury and pain. These results suggest that Parkin-mediated mitophagy is involved in the pathogenesis of OIPNP and may be a potential therapeutic target for OIPNP.

Keywords:  Parkin; mitophagy; oxaliplatin; peripheral nerve pain; salidroside

DOI:  https://doi.org/10.1152/ajpcell.00276.2023
bioRxiv. 2023 Dec 01. pii: 2023.12.01.569475. [Epub ahead of print]

A mitochondrial quality control mechanism reverses the phagosome maturation arrest caused by Mycobacterium tuberculosis.

Surbhi Verma, Mrinmoy Das, Raman D Sharma, Vikas Yadav, Shweta Thakur, Priya Sharma, Mardiana Marzuki, Shihui Foo, Giulia M Piperno, Mehak Z Khan, Babu Mathew, Meenu Bajpai, Jaswinder Singh Maras, Shanshan Howland, Sovan Sarkar, Federica Benvenuti, Amit Singh, Vinay Nandicoori, Amit Singhal, Dhiraj Kumar.

Phagosome maturation arrest (PMA) imposed by Mycobacterium tuberculosis ( Mtb ) is a classic tool that helps Mtb evade macrophage anti-bacterial responses. The exclusion of RAB7, a small GTPase, from Mtb -phagosomes underscores PMA. Here we report an unexpected mechanism that triggers crosstalk between the mitochondrial quality control (MQC) and the phagosome maturation pathways that reverses the PMA. CRISPR-mediated p62/SQSTM1 depletion ( p62 KD ) blocks mitophagy flux without impacting mitochondrial quality. In p62 KD cells, Mtb growth and survival are diminished, mainly through witnessing an increasingly oxidative environment and increased lysosomal targeting. The lysosomal targeting of Mtb is facilitated by enhanced TOM20 + mitochondria-derived vesicles (MDVs) biogenesis, a key MQC mechanism. In p62 KD cells, TOM20 + -MDVs biogenesis is MIRO1/MIRO2-dependent and delivered to lysosomes for degradation in a RAB7-dependent manner. Upon infection in p62 KD cells, TOM20 + -MDVs get extensively targeted to Mtb -phagosomes, inadvertently facilitating RAB7 recruitment, PMA reversal and lysosomal targeting of Mtb . Triggering MQC collapse in p62 KD cells further diminishes Mtb survival signifying cooperation between redox- and lysosome-mediated mechanisms. The MQC-anti-bacterial pathway crosstalk could be exploited for host-directed anti-tuberculosis therapies.

DOI: https://doi.org/10.1101/2023.12.01.569475
J Cachexia Sarcopenia Muscle. 2023 Dec 07.

Obesity worsens mitochondrial quality control and does not protect against skeletal muscle wasting in murine cancer cachexia.

Thomas D Cardaci, Brandon N VanderVeen, Brooke M Bullard, Sierra J McDonald, Christian A Unger, Reilly T Enos, Daping Fan, Kandy T Velázquez, Norma Frizzell, Espen E Spangenburg, E Angela Murphy.

   BACKGROUND: More than 650 million people are obese (BMI > 30) worldwide, which increases their risk for several metabolic diseases and cancer. While cachexia and obesity are at opposite ends of the weight spectrum, leading many to suggest a protective effect of obesity against cachexia, mechanistic support for obesity's benefit is lacking. Given that obesity and cachexia are both accompanied by metabolic dysregulation, we sought to investigate the impact of obesity on skeletal muscle mass loss and mitochondrial dysfunction in murine cancer cachexia.
METHODS: Male C57BL/6 mice were given a purified high fat or standard diet for 16 weeks before being implanted with 106 Lewis lung carcinoma (LLC) cells. Mice were monitored for 25 days, and hindlimb muscles were collected for cachexia indices and mitochondrial assessment via western blotting, high-resolution respirometry and transmission electron microscopy (TEM).
RESULTS: Obese LLC mice experienced significant tumour-free body weight loss similar to lean (-12.8% vs. -11.8%, P = 0.0001) but had reduced survival (33.3% vs. 6.67%, χ2 = 10.04, P = 0.0182). Obese LLC mice had reduced muscle weights (-24%, P < 0.0354) and mCSA (-16%, P = 0.0004) with similar activation of muscle p65 (P = 0.0337), and p38 (P = 0.0008). ADP-dependent coupled respiration was reduced in both Obese and Obese LLC muscle (-30%, P = 0.0072) consistent with reductions in volitional cage activity (-39%, P < 0.0001) and grip strength (-41%, P < 0.0001). TEM revealed stepwise reductions in intermyofibrillar and subsarcolemmal mitochondrial size with Obese (IMF: -37%, P = 0.0009; SS: -21%, P = 0.0101) and LLC (IMF: -40%, P = 0.0019; SS: -27%, P = 0.0383) mice. Obese LLC mice had increased pAMPK (T172; P = 0.0103) and reduced FIS1 (P = 0.0029) and DRP1 (P < 0.0001) mitochondrial fission proteins, which were each unchanged in Lean LLC. Further, mitochondrial TEM analysis revealed that Obese LLC mice had an accumulation of damaged and dysfunctional mitochondria (IMF: 357%, P = 0.0395; SS: 138%, P = 0.0174) in concert with an accumulation of p62 (P = 0.0328) suggesting impaired autophagy and clearance of damaged mitochondria. Moreover, we observed increases in electron lucent vacuoles only in Obese LLC muscle (IMF: 421%, P = 0.0260; SS: 392%, P = 0.0192), further supporting an accumulation of damaged materials that cannot be properly cleared in the obese cachectic muscle.
CONCLUSIONS: Taken together, these results demonstrate that obesity is not protective against cachexia and suggest exacerbated impairments to mitochondrial function and quality control with a particular disruption in the removal of damaged mitochondria. Our findings highlight the need for consideration of the severity of obesity and pre-existing metabolic conditions when determining the impact of weight status on cancer-induced cachexia and functional mitochondrial deficits.

Keywords:  Autophagy; High fat diet; Lewis lung carcinoma; Mitochondrial dysfunction; Mitophagy; Muscle atrophy

DOI:  https://doi.org/10.1002/jcsm.13391
Oncogene. 2023 Dec 11.

ROS production by mitochondria: function or dysfunction?

Flavio R Palma, Benjamin N Gantner, Marcelo J Sakiyama, Cezar Kayzuka, Sanjeev Shukla, Riccardo Lacchini, Brian Cunniff, Marcelo G Bonini.

In eukaryotic cells, ATP generation is generally viewed as the primary function of mitochondria under normoxic conditions. Reactive oxygen species (ROS), in contrast, are regarded as the by-products of respiration, and are widely associated with dysfunction and disease. Important signaling functions have been demonstrated for mitochondrial ROS in recent years. Still, their chemical reactivity and capacity to elicit oxidative damage have reinforced the idea that ROS are the products of dysfunctional mitochondria that accumulate during disease. Several studies support a different model, however, by showing that: (1) limited oxygen availability results in mitochondria prioritizing ROS production over ATP, (2) ROS is an essential adaptive mitochondrial signal triggered by various important stressors, and (3) while mitochondria-independent ATP production can be easily engaged by most cells, there is no known replacement for ROS-driven redox signaling. Based on these observations and other evidence reviewed here, we highlight the role of ROS production as a major mitochondrial function involved in cellular adaptation and stress resistance. As such, we propose a rekindled view of ROS production as a primary mitochondrial function as essential to life as ATP production itself.

DOI: https://doi.org/10.1038/s41388-023-02907-z
FASEB J. 2024 Jan;38(1): e23343

Caveolin-1 promotes mitochondrial health and limits mitochondrial ROS through ROCK/AMPK regulation of basal mitophagic flux.

Logan R Timmins, Milene Ortiz-Silva, Bharat Joshi, Y Lydia Li, Fiona H Dickson, Timothy H Wong, Kurt R Vandevoorde, Ivan R Nabi.

  Caveolin-1 (CAV1), the main structural component of caveolae, is phosphorylated at tyrosine-14 (pCAV1), regulates signal transduction, mechanotransduction, and mitochondrial function, and plays contrasting roles in cancer progression. We report that CRISPR/Cas9 knockout (KO) of CAV1 increases mitochondrial oxidative phosphorylation, increases mitochondrial potential, and reduces ROS in MDA-MB-231 triple-negative breast cancer cells. Supporting a role for pCAV1, these effects are reversed upon expression of CAV1 phosphomimetic CAV1 Y14D but not non-phosphorylatable CAV1 Y14F. pCAV1 is a known effector of Rho-associated kinase (ROCK) signaling and ROCK1/2 signaling mediates CAV1 promotion of increased mitochondrial potential and decreased ROS production in MDA-MB-231 cells. CAV1/ROCK control of mitochondrial potential and ROS is caveolae-independent as similar results were observed in PC3 prostate cancer cells lacking caveolae. Increased mitochondrial health and reduced ROS in CAV1 KO MDA-MB-231 cells were reversed by knockdown of the autophagy protein ATG5, mitophagy regulator PINK1 or the mitochondrial fission protein Drp1 and therefore due to mitophagy. Use of the mitoKeima mitophagy probe confirmed that CAV1 signaling through ROCK inhibited basal mitophagic flux. Activation of AMPK, a major mitochondrial homeostasis protein inhibited by ROCK, is inhibited by CAV1-ROCK signaling and mediates the increased mitochondrial potential, decreased ROS, and decreased basal mitophagy flux observed in wild-type MDA-MB-231 cells. CAV1 regulation of mitochondrial health and ROS in cancer cells therefore occurs via ROCK-dependent inhibition of AMPK. This study therefore links pCAV1 signaling activity at the plasma membrane with its regulation of mitochondrial activity and cancer cell metabolism through control of mitophagy.

Keywords:  AMPK; caveolin-1; mitochondria; mitophagy; reactive oxygen species; rho kinase

DOI:  https://doi.org/10.1096/fj.202201872RR
Biochem Pharmacol. 2023 Dec 10. pii: S0006-2952(23)00531-2. [Epub ahead of print] 115938

The critical roles of STING in mitochondrial homeostasis.

Shishi Zou, Bo Wang, Ke Yi, Dandan Su, Yukai Chen, Ning Li, Qing Geng.

  The stimulator of interferon genes (STING) is a crucial signaling hub in the immune system's antiviral and antimicrobial defense by detecting exogenous and endogenous DNA. The multifaceted functions of STING have been uncovered gradually during past decades, including homeostasis maintenance and overfull immunity or inflammation induction. However, the subcellular regulation of STING and mitochondria is poorly understood. The main functions of STING are outlined in this review. Moreover, we discuss how mitochondria and STING interact through multiple mechanisms, including the release of mitochondrial DNA (mtDNA), modulation of mitochondria-associated membrane (MAM) and mitochondrial dynamics, alterations in mitochondrial metabolism, regulation of reactive oxygen species (ROS) production, and mitochondria-related cell death. Finally, we discuss how STING is crucial to disease development, providing a novel perspective on its role in cellular physiology and pathology.

Keywords:  Cell death; Innate immunity; Mitochondrial dynamics; Mitochondrial metabolism; MtDNA; STING

DOI:  https://doi.org/10.1016/j.bcp.2023.115938
Gut Microbes. 2023 Dec;15(2): 2281011

Butyrate reduces adherent-invasive E. coli-evoked disruption of epithelial mitochondrial morphology and barrier function: involvement of free fatty acid receptor 3.

Samira A Hamed, Armaan Mohan, Saranya Navaneetha Krishnan, Arthur Wang, Marija Drikic, Nicole L Prince, Ian A Lewis, Jane Shearer, Åsa V Keita, Johan D Söderholm, Timothy E Shutt, Derek M McKay.

  Gut bacteria provide benefits to the host and have been implicated in inflammatory bowel disease (IBD), where adherent-invasive E. coli (AIEC) pathobionts (e.g., strain LF82) are associated with Crohn's disease. E. coli-LF82 causes fragmentation of the epithelial mitochondrial network, leading to increased epithelial permeability. We hypothesized that butyrate would limit the epithelial mitochondrial disruption caused by E. coli-LF82. Human colonic organoids and the T84 epithelial cell line infected with E. coli-LF82 (MOI = 100, 4 h) showed a significant increase in mitochondrial network fission that was reduced by butyrate (10 mM) co-treatment. Butyrate reduced the loss of mitochondrial membrane potential caused by E. coli-LF82 and increased expression of PGC-1α mRNA, the master regulator of mitochondrial biogenesis. Metabolomics revealed that butyrate significantly altered E. coli-LF82 central carbon metabolism leading to diminished glucose uptake and increased succinate secretion. Correlating with preservation of mitochondrial network form/function, butyrate reduced E. coli-LF82 transcytosis across T84-cell monolayers. The use of the G-protein inhibitor, pertussis toxin, implicated GPCR signaling as critical to the effect of butyrate, and the free fatty acid receptor three (FFAR3, GPR41) agonist, AR420626, reproduced butyrate's effect in terms of ameliorating the loss of barrier function and reducing the mitochondrial fragmentation observed in E. coli-LF82 infected T84-cells and organoids. These data indicate that butyrate helps maintain epithelial mitochondrial form/function when challenged by E. coli-LF82 and that this occurs, at least in part, via FFAR3. Thus, loss of butyrate-producing bacteria in IBD in the context of pathobionts would contribute to loss of epithelial mitochondrial and barrier functions that could evoke disease and/or exaggerate a low-grade inflammation.

Keywords:  Pathobiont; T84 cells; gut epithelium; mitochondrial dynamics; organoid; permeability

DOI:  https://doi.org/10.1080/19490976.2023.2281011
Proc Natl Acad Sci U S A. 2023 Dec 19. 120(51): e2316823120

Intraneuronal β-amyloid impaired mitochondrial proteostasis through the impact on LONP1.

Wenzhang Wang, Xiaopin Ma, Sabina Bhatta, Changjuan Shao, Fanpeng Zhao, Hisashi Fujioka, Sandy Torres, Fengqin Wu, Xiongwei Zhu.

  Mitochondrial dysfunction plays a critical role in the pathogenesis of Alzheimer's disease (AD). Mitochondrial proteostasis regulated by chaperones and proteases in each compartment of mitochondria is critical for mitochondrial function, and it is suspected that mitochondrial proteostasis deficits may be involved in mitochondrial dysfunction in AD. In this study, we identified LONP1, an ATP-dependent protease in the matrix, as a top Aβ42 interacting mitochondrial protein through an unbiased screening and found significantly decreased LONP1 expression and extensive mitochondrial proteostasis deficits in AD experimental models both in vitro and in vivo, as well as in the brain of AD patients. Impaired METTL3-m6A signaling contributed at least in part to Aβ42-induced LONP1 reduction. Moreover, Aβ42 interaction with LONP1 impaired the assembly and protease activity of LONP1 both in vitro and in vivo. Importantly, LONP1 knockdown caused mitochondrial proteostasis deficits and dysfunction in neurons, while restored expression of LONP1 in neurons expressing intracellular Aβ and in the brain of CRND8 APP transgenic mice rescued Aβ-induced mitochondrial deficits and cognitive deficits. These results demonstrated a critical role of LONP1 in disturbed mitochondrial proteostasis and mitochondrial dysfunction in AD and revealed a mechanism underlying intracellular Aβ42-induced mitochondrial toxicity through its impact on LONP1 and mitochondrial proteostasis.

Keywords:  Alzheimer’s disease; Aβ42; LONP1; mitochondrial dysfunction; protein aggregate

DOI:  https://doi.org/10.1073/pnas.2316823120
Free Radic Biol Med. 2023 Dec 11. pii: S0891-5849(23)01151-6. [Epub ahead of print]

"ATAD3C regulates ATAD3A assembly and function in the mitochondrial membrane".

Paula Gaudó, Elena de Tomás-Mateo, Nuria Garrido-Pérez, Alfredo Santana, Eduardo Ruiz-Pesini, Julio Montoya, Pilar Bayona-Bafaluy.

  Mitochondrial ATAD3A is an ATPase Associated with diverse cellular Activities (AAA) domain containing enzyme, involved in the structural organization of the inner mitochondrial membrane and of increasing importance in childhood disease. In humans, two ATAD3A paralogs arose by gene duplication during evolution: ATAD3B and ATAD3C. Here we investigate the cellular activities of the ATAD3C paralog that has been considered a pseudogene. We detected unique ATAD3C peptides in HEK 293T cells, with expression similar to that in human tissues, and showed that it is an integral membrane protein that exposes its carboxy-terminus to the intermembrane space. Overexpression of ATAD3C, but not of ATAD3A, in fibroblasts caused a decrease in cell proliferation and oxygen consumption rate, and an increase of cellular ROS. This was due to the incorporation of ATAD3C monomers in ATAD3A complex in the mitochondrial membrane reducing its size. Consistent with a negative regulation of ATAD3A function in mitochondrial membrane organization, ATAD3C expression led to increased accumulation of respiratory chain dimeric CIII in the inner membrane, to the detriment to that assembled in respiratory supercomplexes. Our results demonstrate a negative dominant role of the ATAD3C paralog with implications for mitochondrial OXPHOS function and suggest that its expression regulates ATAD3A in the cell.

Keywords:  ATAD3A; ATAD3B; ATAD3C; Mitochondria; OXPHOS; Respiratory complexes; Respiratory supercomplexes

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.12.006
Respir Res. 2023 Dec 13. 24(1): 310

Tom70-regulated mitochondrial biogenesis via TFAM improves hypoxia-induced dysfunction of pulmonary vascular endothelial cells and alleviates hypoxic pulmonary hypertension.

Lei Ma, Yanxia Wang, Xiaoqian Li, Zefang Wang, Bo Zhang, Ying Luo, Yousheng Wu, Zhichao Li, Wen Niu.

   BACKGROUND: Hypoxic pulmonary hypertension (HPH) is a common type of pulmonary hypertension and characterized by pulmonary vascular remodeling and constriction. A large number of studies have shown that pulmonary vascular endothelial cells (PVECs) dysfunction plays an important role in the initiation and development stages of HPH, but the mechanism of PVECs dysfunction after hypoxia remains unclear. In this study, we explored the exact mechanism of PVECs dysfunction after hypoxia.
METHODS: In vitro, we used primary cultured PVECs hypoxia model to mimic HPH injury. We detected the expressions of mitochondrial biogenesis markers, mitochondrial transcription factor A (TFAM) level inside mitochondria, mitochondrial quantity and function, and the components expressions of translocase of outer mitochondrial membrane (TOM) at 24 h after hypoxia. To explore the effects of Tom70 on mitochondrial biogenesis and functions of PVECs after hypoxia, Tom70 overexpression adenovirus was constructed, and the expressions of mitochondrial biogenesis markers, TFAM level inside mitochondria, mitochondrial quantity and function, and the functions of PVECs were detected. And in vivo, we used cre-dependent overexpression adenovirus of Tom70 in the Cdh5-CreERT2 mouse model of HPH to verify the role of upregulating PVECs Tom70 in improving HPH.
RESULTS: Hypoxia obviously increased the expressions of mitochondrial biogenesis markers for PGC-1α, NRF-1 and TFAM, but reduced the content of TFAM in mitochondria and the quantity and functions of mitochondria. In addition, only Tom70 expression among the TOM components was significantly decreased after hypoxia, and up-regulation of Tom70 significantly increased the content of TFAM in mitochondria of PVECs by transporting TFAM into mitochondria after hypoxia, enhanced the quantity and functions of mitochondria, improved the functions of PVECs, and ultimately alleviated HPH.
CONCLUSION: The findings of present study demonstrated that hypoxia induced the decreased expression of Tom70 in PVECs, reduced the mitochondrial biogenesis-associated TFAM protein transporting into mitochondria, inhibited mitochondrial biogenesis, caused PVECs injury, and prompted the formation of HPH. However, up-regulation of Tom70 abolished the hypoxia-induced injurious effects on PVECs and alleviated HPH.

Keywords:  Hypoxic pulmonary hypertension; Mitochondrial biogenesis; Pulmonary vascular endothelial cells; Translocase of outer mitochondrial membrane

DOI:  https://doi.org/10.1186/s12931-023-02631-y
Elife. 2023 Dec 11. pii: RP89232. [Epub ahead of print]12

Mitochondrial temperature homeostasis resists external metabolic stresses.

Mügen Terzioglu, Kristo Veeroja, Toni Montonen, Teemu O Ihalainen, Tiina S Salminen, Paule Bénit, Pierre Rustin, Young-Tae Chang, Takeharu Nagai, Howard T Jacobs.

  Based on studies with a fluorescent reporter dye, Mito Thermo Yellow (MTY), and the genetically encoded gTEMP ratiometric fluorescent temperature indicator targeted to mitochondria, the temperature of active mitochondria in four mammalian and one insect cell line was estimated to be up to 15°C above that of the external environment to which the cells were exposed. High mitochondrial temperature was maintained in the face of a variety of metabolic stresses, including substrate starvation or modification, decreased ATP demand due to inhibition of cytosolic protein synthesis, inhibition of the mitochondrial adenine nucleotide transporter and, if an auxiliary pathway for electron transfer was available via the alternative oxidase, even respiratory poisons acting downstream of oxidative phosphorylation (OXPHOS) complex I. We propose that the high temperature of active mitochondria is an inescapable consequence of the biochemistry of OXPHOS and is homeostatically maintained as a primary feature of mitochondrial metabolism.

Keywords:  D. melanogaster; OXPHOS; biochemistry; bioenergetics; cell biology; chemical biology; human; mitochondria; mouse; organelle; temperature; thermogenesis

DOI:  https://doi.org/10.7554/eLife.89232
J Proteome Res. 2023 Dec 08.

Multiomics Reveals Induction of Neuroblastoma SK-N-BE(2)C Cell Death by Mitochondrial Division Inhibitor 1 through Multiple Effects.

Wei-Hsuan Wang, Yi-Chun Kao, Chiao-Hui Hsieh, Shin-Yu Tsai, Chantal Hoi Yin Cheung, Hsuan-Cheng Huang, Hsueh-Fen Juan.

  Mitochondrial division inhibitor 1 (Mdivi-1) is a well-known synthetic compound aimed at inhibiting dynamin-related protein 1 (Drp1) to suppress mitochondrial fission, making it a valuable tool for studying mitochondrial dynamics. However, its specific effects beyond Drp1 inhibition remain to be confirmed. In this study, we employed integrative proteomics and phosphoproteomics to delve into the molecular responses induced by Mdivi-1 in SK-N-BE(2)C cells. A total of 3070 proteins and 1945 phosphorylation sites were identified, with 880 of them represented as phosphoproteins. Among these, 266 proteins and 97 phosphorylation sites were found to be sensitive to the Mdivi-1 treatment. Functional enrichment analysis unveiled their involvement in serine biosynthesis and extrinsic apoptotic signaling pathways. Through targeted metabolomics, we observed that Mdivi-1 enhanced intracellular serine biosynthesis while reducing the production of C24:1-ceramide. Within these regulated phosphoproteins, dynamic dephosphorylation of proteasome subunit alpha type 3 serine 250 (PSMA3-S250) occurred after Mdivi-1 treatment. Further site-directed mutagenesis experiments revealed that the dephosphorylation-deficient mutant PSMA3-S250A exhibited a decreased cell survival. This research confirms that Mdivi-1's inhibition of mitochondrial division leads to various side effects, ultimately influencing cell survival, rather than solely targeting Drp1 inhibition.

Keywords:  Mdivi-1; multiomics; neuroblastoma; phosphoproteome; proteome; targeted metabolome

DOI:  https://doi.org/10.1021/acs.jproteome.3c00566
Antioxid Redox Signal. 2023 Dec 09.

Glycyrrhizin protects submandibular gland against radiation damage by enhancing antioxidant defense and preserving mitochondrial homeostasis.

Xin Ru Zhou, Xin Yue Wang, Yue Mei Sun, Chong Zhang, Ke Jian Liu, Fu Yin Zhang, Bin Xiang.

AIMS: Radiotherapy inevitably causes radiation damage to the salivary glands (SGs) in patients with head and neck cancers (HNCs). Excessive reactive oxygen species (ROS) levels and imbalanced mitochondrial homeostasis are serious consequences of ionizing radiation in SGs; however, there are few mitochondria-targeting therapeutic approaches. Glycyrrhizin is the main extract of licorice root and exhibits antioxidant activity to relieve mitochondrial damage in certain oxidative stress conditions. Herein, the effects of glycyrrhizin on irradiated submandibular glands (SMGs) and the related mechanisms were investigated.
RESULTS: Glycyrrhizin reduced radiation damage in rat SMGs at both the cell and tissue levels and promoted saliva secretion in irradiated SMGs. Glycyrrhizin significantly downregulated high mobility group box-1 protein (HMGB1) and Toll-like receptor 5 (TLR5). Moreover, glycyrrhizin significantly suppressed the increases in malondialdehyde and glutathione disulfide (GSSG) levels; elevated the activity of some critical antioxidants, including superoxide dismutase, catalase, glutathione peroxidase and glutathione (GSH); and increased the GSH/GSSG ratio in irradiated cells. Importantly, glycyrrhizin effectively enhanced thioredoxin-2 levels and scavenged mitochondrial ROS, inhibited the decline in mitochondrial membrane potential, improved ATP synthesis, preserved the mitochondrial ultrastructure, activated the PGC-1α/NRF1/2/TFAM signaling pathway, and inhibited mitochondria-related apoptosis in irradiated SMG cells and tissues.
INNOVATION: Radiotherapy causes radiation sialadenitis in HNC patients. Our data suggest that glycyrrhizin could be a mitochondria-targeted antioxidant for the prevention of radiation damage in SGs.
CONCLUSIONS: These findings demonstrate that glycyrrhizin protects SMGs from radiation damage by downregulating HMGB1/TLR5 signaling, maintaining intracellular redox balance, eliminating mitochondrial ROS, preserving mitochondrial homeostasis, and inhibiting apoptosis.

DOI: https://doi.org/10.1089/ars.2022.0183
Plant Physiol. 2023 Dec 07. pii: kiad655. [Epub ahead of print]

Deep Proteomics reveals incorporation of unedited proteins into mitochondrial protein complexes in Arabidopsis.

Nils Rugen, Michael Senkler, Hans-Peter Braun.

  The mitochondrial proteome consists of numerous types of proteins which either are encoded and synthesized in the mitochondria, or encoded in the cell nucleus, synthesized in the cytoplasm and imported into the mitochondria. Their synthesis in the mitochondria, but not in the nucleus, relies on the editing of the primary transcripts of their genes at defined sites. Here, we present an in-depth investigation of the mitochondrial proteome of Arabidopsis (Arabidopsis thaliana) and a public online platform for the exploration of the data. For the analysis of our shotgun proteomic data, an Arabidopsis sequence database was created comprising all available protein sequences from the TAIR10 and Araport11 databases, supplemented with sequences of proteins translated from edited and non-edited transcripts of mitochondria. Amino acid sequences derived from partially edited transcripts were also added to analyze proteins encoded by the mitochondrial genome. Proteins were digested in parallel with six different endoproteases to obtain maximum proteome coverage. The resulting peptide fractions were finally analyzed using liquid chromatography (LC) coupled to ion mobility spectrometry (IMS) and tandem mass spectrometry (MS/MS). We generated a 'deep mitochondrial proteome' of 4,692 proteins. 1,339 proteins assigned to mitochondria by the SUBA5 database (https://suba.live) accounted for >80% of the total protein mass of our fractions. The coverage of proteins by identified peptides was particularly high compared to single-protease digests, allowing the exploration of differential splicing and RNA editing events at the protein level. We show that proteins translated from non-edited transcripts can be incorporated into native mitoribosomes and the ATP synthase complex. We present a portal for the use of our data, based on 'proteomaps' with directly linked protein data. The portal is available at www.proteomeexplorer.de.

Keywords:   Arabidopsis thaliana ; Proteome Explorer; RNA editing; alternative splicing; deep mitochondrial proteome; multi-protease

DOI:  https://doi.org/10.1093/plphys/kiad655
Mol Cell Biochem. 2023 Dec 11.

Dihydroartemisinin suppresses glioma growth by repressing ERRα-mediated mitochondrial biogenesis.

Wenxin Zhang, Yan Wang, Lu Chen, Haifei Chen, Huijie Qi, Yong Zheng, Yongli Du, Liudi Zhang, Tianxiao Wang, Qunyi Li.

  Malignant gliomas are an exceptionally lethal form of cancer with limited treatment options. Dihydroartemisinin (DHA), a sesquiterpene lactone antimalarial compound, has demonstrated therapeutic effects in various solid tumors. In our study, we aimed to investigate the mechanisms underlying the anticancer effects of DHA in gliomas. To explore the therapeutic and molecular mechanisms of DHA, we employed various assays, including cell viability, flow cytometry, mitochondrial membrane potential, glucose uptake and glioma xenograft models. Our data demonstrated that DHA significantly inhibited glioma cell proliferation in both temozolomide-resistant cells and glioma stem-like cells. We found that DHA-induced apoptosis occurred via the mitochondria-mediated pathway by initiating mitochondrial dysfunction before promoting apoptosis. Moreover, we discovered that DHA treatment substantially reduced the expression of the mitochondrial biogenesis-related gene, ERRα, in glioma cells. And the ERRα pathway is a critical target in treating glioma with DHA. Our results also demonstrated that the combination of DHA and temozolomide synergistically inhibited the proliferation of glioma cells. In vivo, DHA treatment remarkably extended survival time in mice bearing orthotopic glioblastoma xenografts. Thus, our findings suggest that DHA has a novel role in modulating cancer cell metabolism and suppressing glioma progression by activating the ERRα-regulated mitochondrial apoptosis pathway.

Keywords:  Dihydroartemisinin; Estrogen-related receptor alpha; Glioma; Mitochondrial apoptosis; Temozolomide resistant

DOI:  https://doi.org/10.1007/s11010-023-04892-z