bims-midtic 2023-11-19 papers

bims-midtic

Biomed News

on Mitochondrial dynamics and trafficking in cells

Issue of 2023‒11‒19
twenty-one papers selected by
Omkar Joshi, Turku Bioscience

Regulation of Drp1 and enhancement of mitochondrial fission by the deubiquitinating enzyme PSMD14 facilitates the proliferation of bladder cancer cells.
Aberrant mitochondrial dynamics contributes to diaphragmatic weakness induced by mechanical ventilation.
Mitochondria-associated membrane collapse impairs TBK1-mediated proteostatic stress response in ALS.
Cristae dynamics is modulated in bioenergetically compromised mitochondria.
Integration of FUNDC1-associated mitochondrial protein import and mitochondrial quality control contributes to TDP-43 degradation.
GTPBP8 is required for mitoribosomal biogenesis and mitochondrial translation.
Myeloid Drp1 Deficiency Limits Revascularization in Ischemic Muscles via Inflammatory Macrophage Polarization and Metabolic Reprograming.
Targeting mitochondrial shape: at the heart of cardioprotection.
Mitochondrial entry gate as regulatory hub.
PIM1 attenuates cisplatin-induced AKI by inhibiting Drp1 activation.
Endoplasmic Reticulum Stress Disrupts Mitochondrial Bioenergetics, Dynamics and Causes Corneal Endothelial Cell Apoptosis.
Role of mitophagy in ocular neurodegeneration.
Keep in touch: a perspective on the mitochondrial social network and its implication in health and disease.
3D reconstruction of murine mitochondria reveals changes in structure during aging linked to the MICOS complex.
Astrocyte and L-lactate in the anterior cingulate cortex modulate schema memory and neuronal mitochondrial biogenesis.
Mitigating aberrant Cdk5 activation alleviates mitochondrial defects and motor neuron disease symptoms in spinal muscular atrophy.
Inflammatory macrophages reprogram to immunosuppression by reducing mitochondrial translation.
Activation of mitophagy improves cognitive dysfunction in diabetic mice with recurrent non-severe hypoglycemia.
MitoTracker: A useful tool in need of better alternatives.
FUNDC1-mediated mitophagy triggered by mitochondrial ROS is partially involved in 1-nitropyrene-evoked placental progesterone synthesis inhibition and intrauterine growth retardation in mice.
Inorganic polyphosphate and the regulation of mitochondrial physiology.

Oncol Rep. 2024 Jan;pii: 6. [Epub ahead of print]51(1):

Regulation of Drp1 and enhancement of mitochondrial fission by the deubiquitinating enzyme PSMD14 facilitates the proliferation of bladder cancer cells.

Wei Song, Zhuo Li, Ming Xia, Wei Xiao.

  The protein Dynein‑related protein 1 (Drp1) plays a crucial role in regulating the process of mitochondrial fission, which is known to be associated with the onset and progression of various human diseases. However, the specific impact of Drp1 on bladder cancer has yet to be fully understood. In previous studies, evidence to support the theory that the deubiquitinating enzyme proteasome non‑ATPase regulatory subunit 14 (PSMD14) is responsible for stabilizing and promoting the activity of Drp1, ultimately resulting in increased mitochondrial fission, has been presented. The levels of PSMD14 in both bladder cancer tissues and cells were elevated, as confirmed through immunohistochemical and immunofluorescent staining. Co‑immunoprecipitation and reciprocal co‑IP tests demonstrated that PSMD14 and Drp1 interacted with each other. Upon knockdown of PSMD14, there was a corresponding decrease in Drp1 expression and subsequent inhibition of mitochondrial fission. However, when the Drp1 agonist Mdivi‑1 was applied to cells where PSMD14 expression had been knocked down, a significant increase in cell growth was observed, partially restoring the cancer‑promoting effects of PSMD14 on cell proliferation. In conclusion, these findings suggest that PSMD14 may stimulate bladder cancer cell proliferation by promoting mitochondrial fission through the stabilization of Drp1.

Keywords:  bladder cancer; deubiquitinating; dynein‑related protein 1; mitochondrial fission; proteasome non‑ATPase regulatory subunit 14

DOI:  https://doi.org/10.3892/or.2023.8665
PNAS Nexus. 2023 Nov;2(11): pgad336

Aberrant mitochondrial dynamics contributes to diaphragmatic weakness induced by mechanical ventilation.

Haikel Dridi, Marc Yehya, Robert Barsotti, Yang Liu, Steven Reiken, Lan Azria, Qi Yuan, Laith Bahlouli, Rajesh Kumar Soni, Andrew R Marks, Alain Lacampagne, Stefan Matecki.

  In critical care patients, the ""temporary inactivity of the diaphragm caused by mechanical ventilation (MV) triggers a series of events leading to diaphragmatic dysfunction and atrophy, commonly known as ventilator-induced diaphragm dysfunction (VIDD). While mitochondrial dysfunction related to oxidative stress is recognized as a crucial factor in VIDD, the exact molecular mechanism remains poorly understood. In this study, we observe that 6 h of MV triggers aberrant mitochondrial dynamics, resulting in a reduction in mitochondrial size and interaction, associated with increased expression of dynamin-related protein 1 (DRP1). This effect can be prevented by P110, a molecule that inhibits the recruitment of DRP1 to the mitochondrial membrane. Furthermore, isolated mitochondria from the diaphragms of ventilated patients exhibited increased production of reactive oxygen species (ROS). These mitochondrial changes were associated with the rapid oxidation of type 1 ryanodine receptor (RyR1) and a decrease in the stabilizing subunit calstabin 1. Subsequently, we observed that the sarcoplasmic reticulum (SR) in the ventilated diaphragms showed increased calcium leakage and reduced contractile function. Importantly, the mitochondrial fission inhibitor P110 effectively prevented all of these alterations. Taken together, the results of our study illustrate that MV leads, in the diaphragm, to both mitochondrial fragmentation and dysfunction, linked to the up-/down-regulation of 320 proteins, as assessed through global comprehensive quantitative proteomics analysis, primarily associated with mitochondrial function. These outcomes underscore the significance of developing compounds aimed at modulating the balance between mitochondrial fission and fusion as potential interventions to mitigate VIDD in human patients.

Keywords:  FIS1 inhibitor; calcium homeostasis; dynamin-related protein 1; mitochondrial fission

DOI:  https://doi.org/10.1093/pnasnexus/pgad336
Proc Natl Acad Sci U S A. 2023 Nov 21. 120(47): e2315347120

Mitochondria-associated membrane collapse impairs TBK1-mediated proteostatic stress response in ALS.

Seiji Watanabe, Yuri Murata, Yasuyoshi Oka, Kotaro Oiwa, Mai Horiuchi, Yohei Iguchi, Okiru Komine, Akira Sobue, Masahisa Katsuno, Tomoo Ogi, Koji Yamanaka.

  The organelle contact site of the endoplasmic reticulum and mitochondria, known as the mitochondria-associated membrane (MAM), is a multifunctional microdomain in cellular homeostasis. We previously reported that MAM disruption is a common pathological feature in amyotrophic lateral sclerosis (ALS); however, the precise role of MAM in ALS was uncovered. Here, we show that the MAM is essential for TANK-binding kinase 1 (TBK1) activation under proteostatic stress conditions. A MAM-specific E3 ubiquitin ligase, autocrine motility factor receptor, ubiquitinated nascent proteins to activate TBK1 at the MAM, which results in ribosomal protein degradation. MAM or TBK1 deficiency under proteostatic stress conditions resulted in increased cellular vulnerability in vitro and motor impairment in vivo. Thus, MAM disruption exacerbates proteostatic stress via TBK1 inactivation in ALS. Our study has revealed a proteostatic mechanism mediated by the MAM-TBK1 axis, highlighting the physiological importance of the organelle contact sites.

Keywords:  TANK-binding kinase 1; amyotrophic lateral sclerosis; mitochondria-associated membrane; sigma-1 receptor; stress granules

DOI:  https://doi.org/10.1073/pnas.2315347120
Life Sci Alliance. 2024 Feb;pii: e202302386. [Epub ahead of print]7(2):

Cristae dynamics is modulated in bioenergetically compromised mitochondria.

Mathias Golombek, Thanos Tsigaras, Yulia Schaumkessel, Sebastian Hänsch, Stefanie Weidtkamp-Peters, Ruchika Anand, Andreas S Reichert, Arun Kumar Kondadi.

Cristae membranes have been recently shown to undergo intramitochondrial merging and splitting events. Yet, the metabolic and bioenergetic factors regulating them are unclear. Here, we investigated whether and how cristae morphology and dynamics are dependent on oxidative phosphorylation (OXPHOS) complexes, the mitochondrial membrane potential (ΔΨm), and the ADP/ATP nucleotide translocator. Advanced live-cell STED nanoscopy combined with in-depth quantification were employed to analyse cristae morphology and dynamics after treatment of mammalian cells with rotenone, antimycin A, oligomycin A, and CCCP. This led to formation of enlarged mitochondria along with reduced cristae density but did not impair cristae dynamics. CCCP treatment leading to ΔΨm abrogation even enhanced cristae dynamics showing its ΔΨm-independent nature. Inhibition of OXPHOS complexes was accompanied by reduced ATP levels but did not affect cristae dynamics. However, inhibition of ADP/ATP exchange led to aberrant cristae morphology and impaired cristae dynamics in a mitochondrial subset. In sum, we provide quantitative data of cristae membrane remodelling under different conditions supporting an important interplay between OXPHOS, metabolite exchange, and cristae membrane dynamics.

DOI: https://doi.org/10.26508/lsa.202302386
Cell Death Dis. 2023 11 11. 14(11): 735

Integration of FUNDC1-associated mitochondrial protein import and mitochondrial quality control contributes to TDP-43 degradation.

Jinfa Ma, Lei Liu, Lu Song, Jianghong Liu, Lingyao Yang, Quan Chen, Jane Y Wu, Li Zhu.

Though TDP-43 protein can be translocated into mitochondria and causes mitochondrial damage in TDP-43 proteinopathy, little is known about how TDP-43 is imported into mitochondria. In addition, whether mitochondrial damage is caused by mitochondrial mislocalization of TDP-43 or a side effect of mitochondria-mediated TDP-43 degradation remains to be investigated. Here, our bioinformatical analyses reveal that mitophagy receptor gene FUNDC1 is co-expressed with TDP-43, and both TDP-43 and FUNDC1 expression is correlated with genes associated with mitochondrial protein import pathway in brain samples of patients diagnosed with TDP-43 proteinopathy. FUNDC1 promotes mitochondrial translocation of TDP-43 possibly by promoting TDP-43-TOM70 and DNAJA2-TOM70 interactions, which is independent of the LC3 interacting region of FUNDC1 in cellular experiments. In the transgenic fly model of TDP-43 proteinopathy, overexpressing FUNDC1 enhances TDP-43 induced mitochondrial damage, whereas down-regulating FUNDC1 reverses TDP-43 induced mitochondrial damage. FUNDC1 regulates mitochondria-mediated TDP-43 degradation not only by regulating mitochondrial TDP-43 import, but also by increasing LONP1 level and by activating mitophagy, which plays important roles in cytosolic TDP-43 clearance. Together, this study not only uncovers the mechanism of mitochondrial TDP-43 import, but also unravels the active role played by mitochondria in regulating TDP-43 homeostasis.

DOI: https://doi.org/10.1038/s41419-023-06261-6
Cell Mol Life Sci. 2023 Nov 16. 80(12): 361

GTPBP8 is required for mitoribosomal biogenesis and mitochondrial translation.

Liang Wang, Taru Hilander, Xiaonan Liu, Hoi Ying Tsang, Ove Eriksson, Christopher B Jackson, Markku Varjosalo, Hongxia Zhao.

  Mitochondrial translation occurs on the mitochondrial ribosome, also known as the mitoribosome. The assembly of mitoribosomes is a highly coordinated process. During mitoribosome biogenesis, various assembly factors transiently associate with the nascent ribosome, facilitating the accurate and efficient construction of the mitoribosome. However, the specific factors involved in the assembly process, the precise mechanisms, and the cellular compartments involved in this vital process are not yet fully understood. In this study, we discovered a crucial role for GTP-binding protein 8 (GTPBP8) in the assembly of the mitoribosomal large subunit (mt-LSU) and mitochondrial translation. GTPBP8 is identified as a novel GTPase located in the matrix and peripherally bound to the inner mitochondrial membrane. Importantly, GTPBP8 is specifically associated with the mt-LSU during its assembly. Depletion of GTPBP8 leads to an abnormal accumulation of mt-LSU, indicating that GTPBP8 is critical for proper mt-LSU assembly. Furthermore, the absence of GTPBP8 results in reduced levels of fully assembled 55S monosomes. This impaired assembly leads to compromised mitochondrial translation and, consequently, impaired mitochondrial function. The identification of GTPBP8 as an important player in these processes provides new insights into the molecular mechanisms underlying mitochondrial protein synthesis and its regulation.

Keywords:  GTP binding protein; Mitochondria; Mitochondrial translation; Mitoribosomal protein; Mitoribosome; Mitoribosome assembly; Mitoribosome large subunit

DOI:  https://doi.org/10.1007/s00018-023-05014-0
bioRxiv. 2023 Nov 05. pii: 2023.11.04.565656. [Epub ahead of print]

Myeloid Drp1 Deficiency Limits Revascularization in Ischemic Muscles via Inflammatory Macrophage Polarization and Metabolic Reprograming.

Shikha Yadav, Vijay Ganta, Varadarajan Sudhahar, Dipankar Ash, Sheela Nagarkoti, Archita Das, Margorzata McMenamin, Stephanie Kelley, Tohru Fukai, Masuko Ushio-Fukai.

In the preclinical model of peripheral arterial disease (PAD), M2-like anti-inflammatory macrophage polarization and angiogenesis are required for revascularization. The regulation of cell metabolism and inflammation in macrophages is tightly linked to mitochondrial dynamics. Drp1, a mitochondrial fission protein, has shown context-dependent macrophage phenotypes with both pro- and anti-inflammatory characteristics. However, the role of macrophage Drp1 in reparative neovascularization remains unexplored. Here we show that Drp1 expression was significantly increased in F4/80+ macrophages within ischemic muscle at day 3 following hindlimb ischemia (HLI), an animal model of PAD. Myeloid-specific Drp1 -/- mice exhibited reduced limb perfusion recovery, angiogenesis and muscle regeneration after HLI. These effects were concomitant with enhancement of pro-inflammatory M1-like macrophages, p-NFkB, and TNFα levels, while showing reduction in anti-inflammatory M2-like macrophages and p-AMPK in ischemic muscle of myeloid Drp1 -/- mice. In vitro, Drp1 -/- macrophages under hypoxia serum starvation (HSS), an in vitro PAD model, demonstrated enhanced glycolysis via reducing p-AMPK as well as mitochondrial dysfunction and excessive mitochondrial ROS, resulting in increased M1-gene and reduced M2-gene expression. Conditioned media from HSS-treated Drp1 -/- macrophages exhibited increased secretion of pro-inflammatory cytokines and suppressed angiogenic responses in cultured endothelial cells. Thus, Drp1 deficiency in macrophages under ischemia drives inflammatory metabolic reprogramming and macrophage polarization, thereby limiting revascularization in experimental PAD.

DOI: https://doi.org/10.1101/2023.11.04.565656
Basic Res Cardiol. 2023 Nov 13. 118(1): 49

Targeting mitochondrial shape: at the heart of cardioprotection.

Sauri Hernandez-Resendiz, Aishwarya Prakash, Sze Jie Loo, Martina Semenzato, Kroekkiat Chinda, Gustavo E Crespo-Avilan, Linh Chi Dam, Shengjie Lu, Luca Scorrano, Derek J Hausenloy.

  There remains an unmet need to identify novel therapeutic strategies capable of protecting the myocardium against the detrimental effects of acute ischemia-reperfusion injury (IRI), to reduce myocardial infarct (MI) size and prevent the onset of heart failure (HF) following acute myocardial infarction (AMI). In this regard, perturbations in mitochondrial morphology with an imbalance in mitochondrial fusion and fission can disrupt mitochondrial metabolism, calcium homeostasis, and reactive oxygen species production, factors which are all known to be critical determinants of cardiomyocyte death following acute myocardial IRI. As such, therapeutic approaches directed at preserving the morphology and functionality of mitochondria may provide an important strategy for cardioprotection. In this article, we provide an overview of the alterations in mitochondrial morphology which occur in response to acute myocardial IRI, and highlight the emerging therapeutic strategies for targeting mitochondrial shape to preserve mitochondrial function which have the future therapeutic potential to improve health outcomes in patients presenting with AMI.

Keywords:  Acute myocardial infarction; Acute myocardial ischemia–reperfusion injury; Cardioprotection; Cardiovascular diseases; Heart failure; Mitochondrial morphology

DOI:  https://doi.org/10.1007/s00395-023-01019-9
Biochim Biophys Acta Mol Cell Res. 2023 Jul 04. pii: S0167-4889(23)00101-5. [Epub ahead of print] 119529

Mitochondrial entry gate as regulatory hub.

Fabian den Brave, Nikolaus Pfanner, Thomas Becker.

  Mitochondria import 1000-1300 different precursor proteins from the cytosol. The main mitochondrial entry gate is formed by the translocase of the outer membrane (TOM complex). Molecular coupling and modification of TOM subunits control and modulate protein import in response to cellular signaling. The TOM complex functions as regulatory hub to integrate mitochondrial protein biogenesis and quality control into the cellular proteostasis network.

Keywords:  Mitochondria; Protein sorting; Proteostasis; Quality control; Stress response; TOM complex

DOI:  https://doi.org/10.1016/j.bbamcr.2023.119529
Cell Signal. 2023 Nov 13. pii: S0898-6568(23)00384-4. [Epub ahead of print] 110969

PIM1 attenuates cisplatin-induced AKI by inhibiting Drp1 activation.

Yuzhen Li, Lang Shi, Fan Zhao, Yanwen Luo, Mingjiao Zhang, Xiongfei Wu, Jiefu Zhu.

  Cisplatin, an effective anti-cancer drug, always causes acute kidney injury (AKI) by inducing mitochondrial damage. PIM1 is a serine/threonine kinase, which has been shown to regulate mitochondrial function. However, the role and mechanisms of PIM1 in cisplatin-induced AKI remain unexplored. This study aimed to investigate the effects of PIM1 in cisplatin-induced AKI and its underlying mechanisms. To established Cisplatin-induced AKI model, mice were given a single intraperitoneal injection(20 mg/kg) and BUMPT cells were treated with cisplatin(20 μM/L). PIM1 inhibitor AZD1208 was used to inhibit PIM1 and PIM1-experssing adenovirus was used to overexpress PIM1. Drp1 inhibitor P110 and pcDNA3-Drp1K38A were used to inhibit the activation of Drp1 and mitochondrial fission. The indicators of renal function, renal morphology, apoptosis and mitochondrial dysfunction were assessed to evaluate cisplatin-induced nephrotoxicity. We observed that PIM1 was activated in cisplatin-induced AKI in vivo and cisplatin-induced tubular cells injury in vitro. PIM1 inhibition aggravated cisplatin-induced AKI in vivo, while PIM1 overexpression attenuated cisplatin-induced kidney injury in vivo and in vitro. Moreover, inhibiting PIM1 exacerbated mitochondrial damage in mice, but overexpressing PIM1 relieved mitochondrial damage in mice and BUMPT cells. In mice and BUMPT cells, inhibiting PIM1 deregulated the expression of p-Drp1S637, overexpressing PIM1 upregulated the ex-pression of p-Drp1S637. And inhibiting Drp1 activity alleviated cell damage in BUMPT cells with PIM1 knockdown or inhibition. This study demonstrated the protective effect of PIM1 in cisplatin-induced AKI, and regulation of Drp1 activation might be the underlying mechanism. Altogether, PIM1 may be a potential therapeutic target for cisplatin-induced AKI.

Keywords:  Acute kidney injury; Cisplatin; Drp1; Mitochondrial damage; PIM1

DOI:  https://doi.org/10.1016/j.cellsig.2023.110969
Invest Ophthalmol Vis Sci. 2023 Nov 01. 64(14): 18

Endoplasmic Reticulum Stress Disrupts Mitochondrial Bioenergetics, Dynamics and Causes Corneal Endothelial Cell Apoptosis.

Saba Qureshi, Stephanie Lee, William Steidl, Lukas Ritzer, Michael Parise, Ananya Chaubal, Varun Kumar.

Purpose: Endoplasmic reticulum (ER) and mitochondrial stress are independently associated with corneal endothelial cell (CEnC) loss in many corneal diseases, including Fuchs' endothelial corneal dystrophy (FECD). However, the role of ER stress in mitochondrial dysfunction contributing to CEnC apoptosis is unknown. The purpose of this study is to explore the crosstalk between ER and mitochondrial stress in CEnC.Methods: Human corneal endothelial cell line (HCEnC-21T) and human corneal endothelial tissues were treated with ER stressor tunicamycin. ER stress-reducing chemical 4-phenyl butyric acid (4-PBA) was used in HCEnC-21T after tunicamycin. Fuchs' corneal endothelial cell line (F35T) was used to determine differential activation of ER stress with respect to HCEnC-21T at the baseline. ER stress, mitochondrial-mediated intrinsic apoptotic, mitochondrial fission, and fusion proteins were determined using immunoblotting and immunohistochemistry. Mitochondrial bioenergetics were assessed by mitochondrial membrane potential (MMP) loss and ATP production at 48 hours after tunicamycin. Mitochondria dynamics (shape, area, perimeter) were also analyzed at 24 hours using transmission electron microscopy.
Results: Treatment of HCEnC-21T cell line with tunicamycin activated three ER stress pathways (PERK-eIF2α-CHOP, IRE1α-XBP1, and ATF6), reduced cell viability, upregulated mitochondrial-mediated intrinsic apoptotic molecules (cleaved caspase 9, caspase 3, PARP, Bax, cytochrome C), downregulated anti-apoptotic Bcl-2 protein, initiated mitochondrial dysfunction by loss of MMP and lowering of ATP production, and caused mitochondrial swelling and fragmentation with increased expression of mitochondrial fission proteins (Fis1 and p-Drp1). Fuchs' CEnC (F35T) cell line also showed activation of the ER stress-related proteins (p-eIF2α, GRP78, CHOP, XBP1) compared to HCEnC-21T at the baseline. The 4-PBA ameliorated cell loss and reduced cleaved caspase 3 and 9, thereby rescuing tunicamycin-induced cell death but not mitochondrial bioenergetics in HCEnC-21T cell line.
Conclusions: Tunicamycin-induced ER stress disrupts mitochondrial bioenegetics, dynamics and contributes to the loss of CEnC viability. This novel study highlights the importance of ER-mitochondria crosstalk and its contribution to CEnCs apoptosis, seen in many corneal diseases, including FECD.

DOI: https://doi.org/10.1167/iovs.64.14.18
Front Neurosci. 2023 ;17 1299552

Role of mitophagy in ocular neurodegeneration.

Calvin D Brooks, Bindu Kodati, Dorota L Stankowska, Raghu R Krishnamoorthy.

  Neurons in the central nervous system are among the most metabolically active cells in the body, characterized by high oxygen consumption utilizing glucose both aerobically and anaerobically. Neurons have an abundance of mitochondria which generate adequate ATP to keep up with the high metabolic demand. One consequence of the oxidative phosphorylation mechanism of ATP synthesis, is the generation of reactive oxygen species which produces cellular injury as well as damage to mitochondria. Mitochondria respond to injury by fusion which serves to ameliorate the damage through genetic complementation. Mitochondria also undergo fission to meet an increased energy demand. Loss of mitochondria is also compensated by increased biogenesis to generate new mitochondria. Damaged mitochondria are removed by mitophagy, an autophagic process, in which damaged mitochondria are surrounded by a membrane to form an autophagosome which ultimately fuses with the lysosome resulting in degradation of faulty mitochondria. Dysregulation of mitophagy has been reported in several central nervous system disorders, including, Alzheimer's disease and Parkinson's disease. Recent studies point to aberrant mitophagy in ocular neurodegenerative disorders which could be an important contributor to the disease etiology/pathology. This review article highlights some of the recent findings that point to dysregulation of mitophagy and it's underlying mechanisms in ocular neurodegenerative diseases, including, glaucoma, age-related macular degeneration and diabetic retinopathy.

Keywords:  age-related macular degeneration; diabetic retinopathy; glaucoma; mitochondria; mitophagy; neurodegeneration

DOI:  https://doi.org/10.3389/fnins.2023.1299552
Cell Death Discov. 2023 Nov 16. 9(1): 417

Keep in touch: a perspective on the mitochondrial social network and its implication in health and disease.

Silvia Barabino, Silvia Lombardi, Mara Zilocchi.

Mitochondria have been the focus of extensive research for decades since their dysfunction is linked to more than 150 distinct human disorders. Despite considerable efforts, researchers have only been able to skim the surface of the mitochondrial social complexity and the impact of inter-organelle and inter-organ communication alterations on human health. While some progress has been made in deciphering connections among mitochondria and other cytoplasmic organelles through direct (i.e., contact sites) or indirect (i.e., inter-organelle trafficking) crosstalk, most of these efforts have been restricted to a limited number of proteins involved in specific physiological pathways or disease states. This research bottleneck is further narrowed by our incomplete understanding of the cellular alteration timeline in a specific pathology, which prevents the distinction between a primary organelle dysfunction and the defects occurring due to the disruption of the organelle's interconnectivity. In this perspective, we will (i) summarize the current knowledge on the mitochondrial crosstalk within cell(s) or tissue(s) in health and disease, with a particular focus on neurodegenerative disorders, (ii) discuss how different large-scale and targeted approaches could be used to characterize the different levels of mitochondrial social complexity, and (iii) consider how investigating the different expression patterns of mitochondrial proteins in different cell types/tissues could represent an important step forward in depicting the distinctive architecture of inter-organelle communication.

DOI: https://doi.org/10.1038/s41420-023-01710-9
Aging Cell. 2023 Nov 13. e14009

3D reconstruction of murine mitochondria reveals changes in structure during aging linked to the MICOS complex.

Zer Vue, Edgar Garza-Lopez, Kit Neikirk, Prasanna Katti, Larry Vang, Heather Beasley, Jianqiang Shao, Andrea G Marshall, Amber Crabtree, Alexandria C Murphy, Brenita C Jenkins, Praveena Prasad, Chantell Evans, Brittany Taylor, Margaret Mungai, Mason Killion, Dominique Stephens, Trace A Christensen, Jacob Lam, Benjamin Rodriguez, Mark A Phillips, Nastaran Daneshgar, Ho-Jin Koh, Alice Koh, Jamaine Davis, Nina Devine, Saleem Muhammod, Estevão Scudese, Kenneth Ryan Arnold, Valeria Vanessa Chavarin, Ryan Daniel Robinson, Moumita Chakraborty, Jennifer A Gaddy, Mariya T Sweetwyne, Genesis Wilson, Elma Zaganjor, James Kezos, Cristiana Dondi, Anilkumar K Reddy, Brian Glancy, Annet Kirabo, Anita M Quintana, Dao-Fu Dai, Karen Ocorr, Sandra A Murray, Steven M Damo, Vernat Exil, Blake Riggs, Bret C Mobley, Jose A Gomez, Melanie R McReynolds, Antentor Hinton.

  During aging, muscle gradually undergoes sarcopenia, the loss of function associated with loss of mass, strength, endurance, and oxidative capacity. However, the 3D structural alterations of mitochondria associated with aging in skeletal muscle and cardiac tissues are not well described. Although mitochondrial aging is associated with decreased mitochondrial capacity, the genes responsible for the morphological changes in mitochondria during aging are poorly characterized. We measured changes in mitochondrial morphology in aged murine gastrocnemius, soleus, and cardiac tissues using serial block-face scanning electron microscopy and 3D reconstructions. We also used reverse transcriptase-quantitative PCR, transmission electron microscopy quantification, Seahorse analysis, and metabolomics and lipidomics to measure changes in mitochondrial morphology and function after loss of mitochondria contact site and cristae organizing system (MICOS) complex genes, Chchd3, Chchd6, and Mitofilin. We identified significant changes in mitochondrial size in aged murine gastrocnemius, soleus, and cardiac tissues. We found that both age-related loss of the MICOS complex and knockouts of MICOS genes in mice altered mitochondrial morphology. Given the critical role of mitochondria in maintaining cellular metabolism, we characterized the metabolomes and lipidomes of young and aged mouse tissues, which showed profound alterations consistent with changes in membrane integrity, supporting our observations of age-related changes in muscle tissues. We found a relationship between changes in the MICOS complex and aging. Thus, it is important to understand the mechanisms that underlie the tissue-dependent 3D mitochondrial phenotypic changes that occur in aging and the evolutionary conservation of these mechanisms between Drosophila and mammals.

Keywords:   Drosophila ; 3D morphometry; MICOS; aging; mitochondria; mitochondrial disease; mitochondrion; reconstruction; reticulum; serial block-face SEM; skeletal muscle

DOI:  https://doi.org/10.1111/acel.14009
Elife. 2023 11 14. pii: e85751. [Epub ahead of print]12

Astrocyte and L-lactate in the anterior cingulate cortex modulate schema memory and neuronal mitochondrial biogenesis.

Mastura Akter, Mahadi Hasan, Aruna Surendran Ramkrishnan, Zafar Iqbal, Xianlin Zheng, Zhongqi Fu, Zhuogui Lei, Anwarul Karim, Ying Li.

  Astrocyte-derived L-lactate was shown to confer beneficial effects on synaptic plasticity and cognitive functions. However, how astrocytic Gi signaling in the anterior cingulate cortex (ACC) modulates L-lactate levels and schema memory is not clear. Here, using chemogenetic approach and well-established behavioral paradigm, we demonstrate that astrocytic Gi pathway activation in the ACC causes significant impairments in flavor-place paired associates (PAs) learning, schema formation, and PA memory retrieval in rats. It also impairs new PA learning even if a prior associative schema exists. These impairments are mediated by decreased L-lactate in the ACC due to astrocytic Gi activation. Concurrent exogenous L-lactate administration bilaterally into the ACC rescues these impairments. Furthermore, we show that the impaired schema memory formation is associated with a decreased neuronal mitochondrial biogenesis caused by decreased L-lactate level in the ACC upon astrocytic Gi activation. Our study also reveals that L-lactate-mediated mitochondrial biogenesis is dependent on monocarboxylate transporter 2 (MCT2) and NMDA receptor activity - discovering a previously unrecognized signaling role of L-lactate. These findings expand our understanding of the role of astrocytes and L-lactate in the brain functions.

Keywords:  DREADD; anterior cingulate cortex; astrocyte; lactate; mitochondrial biogenesis; neuroscience; rat; schema

DOI:  https://doi.org/10.7554/eLife.85751
Proc Natl Acad Sci U S A. 2023 Nov 21. 120(47): e2300308120

Mitigating aberrant Cdk5 activation alleviates mitochondrial defects and motor neuron disease symptoms in spinal muscular atrophy.

Nimrod Miller, Zhaofa Xu, Katharina A Quinlan, Amy Ji, Jered V McGivern, Zhihua Feng, Han Shi, Chien-Ping Ko, Li-Huei Tsai, Charles J Heckman, Allison D Ebert, Yongchao C Ma.

  Spinal muscular atrophy (SMA), the top genetic cause of infant mortality, is characterized by motor neuron degeneration. Mechanisms underlying SMA pathogenesis remain largely unknown. Here, we report that the activity of cyclin-dependent kinase 5 (Cdk5) and the conversion of its activating subunit p35 to the more potent activator p25 are significantly up-regulated in mouse models and human induced pluripotent stem cell (iPSC) models of SMA. The increase of Cdk5 activity occurs before the onset of SMA phenotypes, suggesting that it may be an initiator of the disease. Importantly, aberrant Cdk5 activation causes mitochondrial defects and motor neuron degeneration, as the genetic knockout of p35 in an SMA mouse model rescues mitochondrial transport and fragmentation defects, and alleviates SMA phenotypes including motor neuron hyperexcitability, loss of excitatory synapses, neuromuscular junction denervation, and motor neuron degeneration. Inhibition of the Cdk5 signaling pathway reduces the degeneration of motor neurons derived from SMA mice and human SMA iPSCs. Altogether, our studies reveal a critical role for the aberrant activation of Cdk5 in SMA pathogenesis and suggest a potential target for therapeutic intervention.

Keywords:  Cdk5; mitochondria; motor neuron; neurodegeneration; spinal muscular atrophy

DOI:  https://doi.org/10.1073/pnas.2300308120
Nat Commun. 2023 Nov 17. 14(1): 7471

Inflammatory macrophages reprogram to immunosuppression by reducing mitochondrial translation.

Marlies Cortés, Agnese Brischetto, M C Martinez-Campanario, Chiara Ninfali, Verónica Domínguez, Sara Fernández, Raquel Celis, Anna Esteve-Codina, Juan J Lozano, Julia Sidorova, Gloria Garrabou, Anna-Maria Siegert, Carlos Enrich, Belén Pintado, Manuel Morales-Ruiz, Pedro Castro, Juan D Cañete, Antonio Postigo.

Acute inflammation can either resolve through immunosuppression or persist, leading to chronic inflammation. These transitions are driven by distinct molecular and metabolic reprogramming of immune cells. The anti-diabetic drug Metformin inhibits acute and chronic inflammation through mechanisms still not fully understood. Here, we report that the anti-inflammatory and reactive-oxygen-species-inhibiting effects of Metformin depend on the expression of the plasticity factor ZEB1 in macrophages. Using mice lacking Zeb1 in their myeloid cells and human patient samples, we show that ZEB1 plays a dual role, being essential in both initiating and resolving inflammation by inducing macrophages to transition into an immunosuppressed state. ZEB1 mediates these diverging effects in inflammation and immunosuppression by modulating mitochondrial content through activation of autophagy and inhibition of mitochondrial protein translation. During the transition from inflammation to immunosuppression, Metformin mimics the metabolic reprogramming of myeloid cells induced by ZEB1. Mechanistically, in immunosuppression, ZEB1 inhibits amino acid uptake, leading to downregulation of mTORC1 signalling and a decrease in mitochondrial translation in macrophages. These results identify ZEB1 as a driver of myeloid cell metabolic plasticity, suggesting that targeting its expression and function could serve as a strategy to modulate dysregulated inflammation and immunosuppression.

DOI: https://doi.org/10.1038/s41467-023-42277-4
Mol Cell Endocrinol. 2023 Nov 11. pii: S0303-7207(23)00260-5. [Epub ahead of print] 112109

Activation of mitophagy improves cognitive dysfunction in diabetic mice with recurrent non-severe hypoglycemia.

Kejun Wu, Cuihua Huang, Wenrong Zheng, Yubin Wu, Qintao Huang, Menghua Lin, Ruonan Gao, Liqin Qi, Guanlian He, Xiaoying Liu, Xiaohong Liu, Linxi Wang, Zhou Chen, Libin Liu.

  Recurrent non-severe hypoglycemia (RH) in patients with diabetes might be associated with cognitive impairment. Previously, we found that mitochondrial dysfunction plays an important role in this pathological process; however, the mechanism remains unclear. The objective of this study was to determine the molecular mechanisms of mitochondrial damage associated with RH in diabetes mellitus (DM). We found that RH is associated with reduced hippocampal mitophagy in diabetic mice, mainly manifested by reduced autophagosome formation and impaired recognition of impaired mitochondria, mediated by the PINK1/Parkin pathway. The same impaired mitophagy initiation was observed in an in vitro high-glucose cultured astrocyte model with recurrent low-glucose interventions. Promoting autophagosome formation and activating PINK1/Parkin-mediated mitophagy protected mitochondrial function and cognitive function in mice. The results showed that impaired mitophagy is involved in the occurrence of mitochondrial dysfunction, mediating the neurological impairment associated with recurrent low glucose under high glucose conditions.

Keywords:  Astrocyte; Cognitive impairment; Diabetes; Mitophagy; Recurrent non-severe hypoglycemia

DOI:  https://doi.org/10.1016/j.mce.2023.112109
Eur J Cell Biol. 2023 Oct 31. pii: S0171-9335(23)00086-9. [Epub ahead of print]102(4): 151371

MitoTracker: A useful tool in need of better alternatives.

Kit Neikirk, Andrea G Marshall, Bartosz Kula, Nathan Smith, Sharonda LeBlanc, Antentor Hinton.

  The fluorescence viewing of mitochondria is commonly performed by MitoTracker, a lipophilic cationic dye that is taken up by the mitochondria. In this forum, we highlight several issues that may occur with MitoTracker, including staining of other organelles. Our aim is to offer alternative dyes and discuss their advantages and disadvantages. We also offer options for software with alternatives to MitoTracker to expedite future experimental design.

Keywords:  Fluorescent probes; Membrane potential; MitoTracker; Mitochondria

DOI:  https://doi.org/10.1016/j.ejcb.2023.151371
Sci Total Environ. 2023 Nov 10. pii: S0048-9697(23)07011-0. [Epub ahead of print]908 168383

FUNDC1-mediated mitophagy triggered by mitochondrial ROS is partially involved in 1-nitropyrene-evoked placental progesterone synthesis inhibition and intrauterine growth retardation in mice.

Jian Li, Xin Dong, Jia-Yu Liu, Lan Gao, Wei-Wei Zhang, Yi-Chao Huang, Yan Wang, Hua Wang, Wei Wei, De-Xiang Xu.

  Intrauterine growth retardation (IUGR) is a major cause of perinatal morbidity and mortality. Previous studies showed that 1-nitropyrene (1-NP), an atmospheric pollutant, induces placental dysfunction and IUGR, but the exact mechanisms remain uncertain. In this research, we aimed to explore the role of mitophagy on 1-NP-evoked placental progesterone (P4) synthesis inhibition and IUGR in a mouse model. As expected, P4 levels were decreased in 1-NP-exposed mouse placentas and maternal sera. Progesterone synthases, CYP11A1 and 3βHSD1, were correspondingly declined in 1-NP-exposed mouse placentas and JEG-3 cells. Mitophagy, as determined by LC3B-II elevation and TOM20 reduction, was evoked in 1-NP-exposed JEG-3 cells. Mdivi-1, a specific mitophagy inhibitor, relieved 1-NP-evoked downregulation of progesterone synthases in JEG-3 cells. Additional experiments showed that ULK1/FUNDC1 signaling was activated in 1-NP-exposed JEG-3 cells. ULK1 inhibitor or FUNDC1-targeted siRNA blocked 1-NP-induced mitophagy and progesterone synthase downregulation in JEG-3 cells. Further analysis found that mitochondrial reactive oxygen species (ROS) were increased and GCN2 was activated in 1-NP-exposed JEG-3 cells. GCN2iB, a selective GCN2 inhibitor, and MitoQ, a mitochondria-targeted antioxidant, attenuated GCN2 activation, FUNDC1-mediated mitophagy, and downregulation of progesterone synthases in JEG-3 cells. In vivo, gestational MitoQ supplement alleviated 1-NP-evoked reduction of placental P4 synthesis and IUGR. These results suggest that FUNDC1-mediated mitophagy triggered by mitochondrial ROS may contribute partially to 1-NP-induced placental P4 synthesis inhibition and IUGR.

Keywords:  1-Nitropyrene; FUNDC1-mediated mitophagy; GCN2 activation; Intrauterine growth retardation; Progesterone synthesis; Reactive oxygen species

DOI:  https://doi.org/10.1016/j.scitotenv.2023.168383
Biochem Soc Trans. 2023 Nov 13. pii: BST20230735. [Epub ahead of print]

Inorganic polyphosphate and the regulation of mitochondrial physiology.

Renata T Da Costa, Lindsey M Riggs, Maria E Solesio.

  Inorganic polyphosphate (polyP) is an ancient polymer that is well-conserved throughout evolution. It is formed by multiple subunits of orthophosphates linked together by phosphoanhydride bonds. The presence of these bonds, which are structurally similar to those found in ATP, and the high abundance of polyP in mammalian mitochondria, suggest that polyP could be involved in the regulation of the physiology of the organelle, especially in the energy metabolism. In fact, the scientific literature shows an unequivocal role for polyP not only in directly regulating oxidative a phosphorylation; but also in the regulation of reactive oxygen species metabolism, mitochondrial free calcium homeostasis, and the formation and opening of mitochondrial permeability transitions pore. All these processes are closely interconnected with the status of mitochondrial bioenergetics and therefore play a crucial role in maintaining mitochondrial and cell physiology. In this invited review, we discuss the main scientific literature regarding the regulatory role of polyP in mammalian mitochondrial physiology, placing a particular emphasis on its impact on energy metabolism. Although the effects of polyP on the physiology of the organelle are evident; numerous aspects, particularly within mammalian cells, remain unclear and require further investigation. These aspects encompass, for example, advancing the development of more precise analytical methods, unraveling the mechanism responsible for sensing polyP levels, and understanding the exact molecular mechanism that underlies the effects of polyP on mitochondrial physiology. By increasing our understanding of the biology of this ancient and understudied polymer, we could unravel new pharmacological targets in diseases where mitochondrial dysfunction, including energy metabolism dysregulation, has been broadly described.

Keywords:  cell biology; energy metabolism; inorganic polyphosphate; mitochondria; mitochondrial physiology; polyP

DOI:  https://doi.org/10.1042/BST20230735