bims-midtic 2023-11-12 papers

bims-midtic

Biomed News

on Mitochondrial dynamics and trafficking in cells

Issue of 2023–11–12
25 papers selected by
Omkar Joshi, Turku Bioscience

ER-mitochondria contact sites in mitochondrial DNA dynamics, maintenance, and distribution.
ESYT1 tethers the ER to mitochondria and is required for mitochondrial lipid and calcium homeostasis.
Visualization and Quantification of Endogenous Intra-Organelle Protein Interactions at ER-Mitochondria Contact Sites by Proximity Ligation Assays.
A review for the correlation between optic atrophy 1-dependent mitochondrial fusion and cardiovascular disorders.
Nicotine Affects Mitochondrial Structure and Function in Human Airway Smooth Muscle Cells.
Interaction between the mitochondrial adaptor MIRO and the motor adaptor TRAK.
Enterovirus 71 leads to abnormal mitochondrial dynamics in human neuroblastoma SK-N-SH cells.
Transfer of massive mitochondria from astrocytes reduce propofol neurotoxicity.
SIRT1 inhibits mitochondrial hyperfusion associated mito-bulb formation to sensitize oral cancer cells for apoptosis in a mtROS-dependent signalling pathway.
The power and potential of mitochondria transfer.
Regulation of mitochondrial structure by the actin cytoskeleton.
Mitopherogenesis, a form of mitochondria-specific ectocytosis, regulates sperm mitochondrial quantity and fertility.
Aggregation of alpha-synuclein disrupts mitochondrial metabolism and induce mitophagy via cardiolipin externalization.
RICH2 decreases the mitochondrial number and affects mitochondrial localization in diffuse low-grade glioma-related epilepsy.
FUNDC1 collaborates with PINK1 in regulating mitochondrial Fission and compensating for PINK1 deficiency.
Burst of hopping trafficking correlated reversible dynamic interactions between lipid droplets and mitochondria under starvation.
Membrane contact site detection (MCS-DETECT) reveals dual control of rough mitochondria-ER contacts.
NDP52 SUMOylation contributes to low-dose X-rays-induced cardiac hypertrophy through PINK1/Parkin-mediated mitophagy via MUL1/SUMO2 signalling.
Mitohormesis.
Ola1p trafficking indicates an interaction network between mitochondria, Lipid droplets and stress granules in times of stress.
Adaptive Nanoparticle-Mediated Modulation of Mitochondrial Homeostasis and Inflammation to Enhance Infected Bone Defect Healing.
Tubular TMEM16A promotes tubulointerstitial fibrosis by suppressing PGC-1α-mediated mitochondrial homeostasis in diabetic kidney disease.
Probing the dynamic crosstalk of lysosomes and mitochondria with structured illumination microscopy.
Non-steroidal mineralocorticoid receptor antagonist finerenone ameliorates mitochondrial dysfunction via PI3K/Akt/eNOS signaling pathway in diabetic tubulopathy.
Mitochondrial regulation in human pluripotent stem cells during reprogramming and β cell differentiation.

Int J Biochem Cell Biol. 2023 Nov 04. pii: S1357-2725(23)00131-0. [Epub ahead of print] 106492

ER-mitochondria contact sites in mitochondrial DNA dynamics, maintenance, and distribution.

Hema Saranya Ilamathi, Marc Germain.

  Mitochondria are central cellular metabolic hubs. Their function requires proteins encoded by nuclear DNA, but also mitochondrial DNA (mtDNA) whose maintenance is essential for the proper function of the organelle. Defective mtDNA maintenance and distribution are associated with mitochondrial diseases. mtDNA is organized into nucleo-protein complexes called nucleoids that dynamically move along the mitochondrial network and interact with each other. mtDNA replication and nucleoid distribution is an active process regulated by the complex interplay of mitochondrial dynamics, endoplasmic reticulum (ER)-mitochondria contact sites, and cytoskeletal networks. For example, defects in mitochondrial fusion and fission or ER-mitochondria contact sites affect nucleoid maintenance and distribution. In this review, we discuss the process of nucleoid dynamics and the factors regulating nucleoid maintenance and distribution.

Keywords:  ER sheets; ERMCS; mitochondria; mtDNA-nucleoid

DOI:  https://doi.org/10.1016/j.biocel.2023.106492
Life Sci Alliance. 2024 Jan;pii: e202302335. [Epub ahead of print]7(1):

ESYT1 tethers the ER to mitochondria and is required for mitochondrial lipid and calcium homeostasis.

Alexandre Janer, Jordan L Morris, Michiel Krols, Hana Antonicka, Mari J Aaltonen, Zhen-Yuan Lin, Hanish Anand, Anne-Claude Gingras, Julien Prudent, Eric A Shoubridge.

Mitochondria interact with the ER at structurally and functionally specialized membrane contact sites known as mitochondria-ER contact sites (MERCs). Combining proximity labelling (BioID), co-immunoprecipitation, confocal microscopy and subcellular fractionation, we found that the ER resident SMP-domain protein ESYT1 was enriched at MERCs, where it forms a complex with the outer mitochondrial membrane protein SYNJ2BP. BioID analyses using ER-targeted, outer mitochondrial membrane-targeted, and MERC-targeted baits, confirmed the presence of this complex at MERCs and the specificity of the interaction. Deletion of ESYT1 or SYNJ2BP reduced the number and length of MERCs. Loss of the ESYT1-SYNJ2BP complex impaired ER to mitochondria calcium flux and provoked a significant alteration of the mitochondrial lipidome, most prominently a reduction of cardiolipins and phosphatidylethanolamines. Both phenotypes were rescued by reexpression of WT ESYT1 and an artificial mitochondria-ER tether. Together, these results reveal a novel function for ESYT1 in mitochondrial and cellular homeostasis through its role in the regulation of MERCs.

DOI: https://doi.org/10.26508/lsa.202302335
J Vis Exp. 2023 Oct 20.

Visualization and Quantification of Endogenous Intra-Organelle Protein Interactions at ER-Mitochondria Contact Sites by Proximity Ligation Assays.

Vera Filipa Monteiro-Cardoso, Romain Le Bars, Francesca Giordano.

Membrane contact sites (MCSs) are areas of close membrane proximity that allow and regulate the dynamic exchange of diverse biomolecules (i.e., calcium and lipids) between the juxtaposed organelles without involving membrane fusion. MCSs are essential for cellular homeostasis, and their functions are ensured by the resident components, which often exist as multimeric protein complexes. MCSs often involve the endoplasmic reticulum (ER), a major site of lipid synthesis and cellular calcium storage, and are particularly important for organelles, such as the mitochondria, which are excluded from the classical vesicular transport pathways. In the last years, MCSs between the ER and mitochondria have been extensively studied, as their functions strongly impact cellular metabolism/bioenergetics. Several proteins have started to be identified at these contact sites, including membrane tethers, calcium channels, and lipid transfer proteins, thus raising the need for new methodologies and technical approaches to study these MCS components. Here, we describe a protocol consisting of combined technical approaches, that include proximity ligation assay (PLA), mitochondria staining, and 3D imaging segmentation, that allows the detection of proteins that are physically close (>40 nm) to each other and that reside on the same membrane at ER-mitochondria MCSs. For instance, we used two ER-anchored lipid transfer proteins, ORP5 and ORP8, which have previously been shown to interact and localize at ER-mitochondria and ER-plasma membrane MCSs. By associating the ORP5-ORP8 PLA with cell imaging software analysis, it was possible to estimate the distance of the ORP5-ORP8 complex from the mitochondrial surface and determine that about 50% of ORP5-ORP8 PLA interaction occurs at ER subdomains in close proximity to mitochondria.

DOI: https://doi.org/10.3791/64750
Int J Biol Macromol. 2023 Nov 06. pii: S0141-8130(23)04809-2. [Epub ahead of print]254(Pt 2): 127910

A review for the correlation between optic atrophy 1-dependent mitochondrial fusion and cardiovascular disorders.

Bi-Feng Yao, Xiu-Ju Luo, Jun Peng.

  Mitochondrial dynamics homeostasis is sustained by continuous and balanced fission and fusion, which are determinants of morphology, abundance, biogenesis and mitophagy of mitochondria. Optic atrophy 1 (OPA1), as the only inner mitochondrial membrane fusion protein, plays a key role in stabilizing mitochondrial dynamics. The disturbance of mitochondrial dynamics contributes to the pathophysiological progress of cardiovascular disorders, which are the main cause of death worldwide in recent decades and result in tremendous social burden. In this review, we describe the latest findings regarding OPA1 and its role in mitochondrial fusion. We summarize the post-translational modifications (PTMs) for OPA1 and its regulatory role in mitochondrial dynamics. Then the diverse cell fates caused by OPA1 expression during cardiovascular disorders are discussed. Moreover, cardiovascular disorders (such as heart failure, myocardial ischemia/reperfusion injury, cardiomyopathy and cardiac hypertrophy) relevant to OPA1-dependent mitochondrial dynamics imbalance have been detailed. Finally, we highlight the potential that targeting OPA1 to impact mitochondrial fusion may be used as a novel strategy against cardiovascular disorders.

Keywords:  Cardiovascular disorders; Cell death; Mitochondrial dynamics; Optic atrophy 1; Post-translation modification

DOI:  https://doi.org/10.1016/j.ijbiomac.2023.127910
Am J Physiol Lung Cell Mol Physiol. 2023 Nov 07.

Nicotine Affects Mitochondrial Structure and Function in Human Airway Smooth Muscle Cells.

Niyati A Borkar, Michael A Thompson, Colleen M Bartman, Venkatachalem Sathish, Y S Prakash, Christina M Pabelick.

  Exposure to cigarette smoke and e-cigarettes, with nicotine as the active constituent, contributes to increased health risks associated with asthma. Nicotine exerts its functional activity via nicotinic acetylcholine receptors (nAChRs) and the alpha7 subtype (α7nAChR) has recently been shown to adversely affect airway dynamics. The mechanisms of α7nAChR action in airways, particularly in the context of airway smooth muscle (ASM), a key cell type in asthma, are still under investigation. Mitochondria have garnered increasing interest for their role in regulating airway tone and adaptations to cellular stress. Here mitochondrial dynamics such as fusion vs. fission, and mitochondrial Ca2+ ([Ca2+]m), play an important role in mitochondrial homeostasis. There is currently no information on effects and mechanisms by which nicotine regulates mitochondrial structure and function in ASM in the context of asthma. We hypothesized that nicotine disrupts mitochondrial morphology, fission-fusion balance, and mitochondrial Ca2+ regulation, with altered mitochondrial respiration and bioenergetics in the context of asthmatic ASM. Using human ASM (hASM) cells from non-asthmatics, asthmatics and smokers, we examined effects of nicotine on mitochondrial dynamics and [Ca2+]m. Fluorescence [Ca2+]m imaging of hASM cells with rhod-2 showed robust responses to 10 μM nicotine, particularly in asthmatics and smokers. Nicotine increased expression of fission proteins while decreasing fusion proteins, again in asthmatics and smokers. Seahorse analysis showed blunted oxidative phosphorylation parameters in response to nicotine in these groups. α7nAChR siRNA blunted nicotine effects, rescuing [Ca2+]m, changes in mitochondrial structural proteins and mitochondrial dysfunction. These data highlight mitochondria as a target of nicotine effects on ASM, where mitochondrial disruption and impaired buffering could permit downstream effects of nicotine in the context of asthma.

Keywords:  asthma; calcium; lung; mitochondria; nicotinic cholinergic receptor

DOI:  https://doi.org/10.1152/ajplung.00158.2023
J Biol Chem. 2023 Nov 08. pii: S0021-9258(23)02469-9. [Epub ahead of print] 105441

Interaction between the mitochondrial adaptor MIRO and the motor adaptor TRAK.

Elana E Baltrusaitis, Erika E Ravitch, Adam R Fenton, Tania Perez, Erika L F Holzbaur, Roberto Dominguez.

  MIRO (mitochondrial Rho GTPase) consists of two GTPase domains flanking two Ca2+-binding EF-hand domains. A C-terminal transmembrane helix anchors MIRO to the outer mitochondrial membrane, where it functions as a general adaptor for the recruitment of cytoskeletal proteins that control mitochondrial dynamics. One protein recruited by MIRO is TRAK (trafficking kinesin-binding protein), which in turn recruits the microtubule-based motors kinesin-1 and dynein-dynactin. The mechanism by which MIRO interacts with TRAK on the mitochondrial membrane is not well understood. Here, we map and quantitatively characterize the interaction of human MIRO1 and TRAK1 and test its potential regulation by Ca2+ and/or GTP binding to MIRO1. TRAK1 binds MIRO1 with low micromolar affinity. The interaction was mapped to a fragment comprising MIRO1's EF-hands and C-terminal GTPase domain and to a conserved sequence motif within TRAK1 residues 394-431, immediately C-terminal to the Spindly motif. This sequence is sufficient for MIRO1 binding in vitro and is necessary for MIRO1-dependent localization of TRAK1 to mitochondria in cells. MIRO1's EF-hands bind Ca2+ with dissociation constants (KD) of 3.9 μM and 300 nM. This suggests that under cellular conditions one EF-hand may be constitutively bound to Ca2+ whereas the other EF-hand binds Ca2+ in a regulated manner, depending on its local concentration. Yet, the MIRO1-TRAK1 interaction is independent of Ca2+ binding to the EF-hands and of the nucleotide state (GDP or GTP) of the C-terminal GTPase. The interaction is also independent of TRAK1 dimerization, such that a TRAK1 dimer can be expected to bind two MIRO1 molecules on the mitochondrial surface.

Keywords:  EF-hand; GTPase; Mitochondrial dynamics; calcium; isothermal titration calorimetry (ITC); motor adaptor; mutagenesis

DOI:  https://doi.org/10.1016/j.jbc.2023.105441
Virus Res. 2023 Nov 08. pii: S0168-1702(23)00229-0. [Epub ahead of print] 199267

Enterovirus 71 leads to abnormal mitochondrial dynamics in human neuroblastoma SK-N-SH cells.

Wanling Zhang, Haiyan Yang, Zhengyun Liu, Shengyu Wang, Tianyang Chen, Hong Song, Yunbin Xu, Fajin Li, Guo Luo, Huan Wang.

  EV71, a significant pathogen causing hand-foot-mouth disease, is associated with severe neurological complications such as brain stem encephalitis, aseptic meningitis, and acute flaccid paralysis. While the role of mitochondrial dynamics in regulating the replication of numerous viruses is recognized, its specific involvement in EV71 remains unclear. This study aimed to elucidate the role of mitochondrial dynamics in human neuroblastoma SK-N-SH cells during EV71 infection. Utilizing laser confocal microscopy and transmission electron microscopy, we observed that EV71 infection induced mitochondrial elongation and damage to cristae structures, concurrently accelerating mitochondrial movement. Furthermore, we identified the reduction in the expression of dynamin-related protein 1 (Drp1) and optic atrophy protein 1 (Opa1) and the increased expression of Mitofusion 2 (Mfn2) upon EV71 infection. Notably, EV71 directly stimulated the generation of mitochondrial reactive oxygen species (ROS), leading to a decline in mitochondrial membrane potential and ATP levels. Remarkably, the application of melatonin, a potent mitochondrial protector, inhibited EV71 replication by restoring Drp1 expression. These findings collectively indicate that EV71 induces alterations in mitochondrial morphology and dynamics within SK-N-SH cells, potentially impairing mitochondrial function and contributing to nervous system dysfunction. The restoration of proper mitochondrial dynamics may hold promise as a prospective approach to counteract EV71 infection.

Keywords:  Enterovirus 71; Melatonin; Mitochondrial dynamics; Nervous system

DOI:  https://doi.org/10.1016/j.virusres.2023.199267
Neurosci Lett. 2023 Nov 04. pii: S0304-3940(23)00501-3. [Epub ahead of print]818 137542

Transfer of massive mitochondria from astrocytes reduce propofol neurotoxicity.

Zhan Zhou, Weixin Dai, Tianxiao Liu, Min Shi, Yi Wei, Lifei Chen, Yubo Xie.

  Studies have shown that propofol-induced neurotoxicity is mediated by disruption of mitochondrial fission and fusion, leading to an imbalance in energy supply for developing neurons. Healthy mitochondria released from astrocytes migrate to compromised neurons to mitigate propofol-induced neurotoxicity, yet the precise mechanisms involved require further clarification. In our investigation, primary neurons were incubated with propofol, which decreased ATP synthesis and mitochondrial membrane potential, increased ROS generation and neuronal apoptosis. Notably, astrocytes did not respond to the deleterious effects of propofol. The culture medium of neurons or astrocytes incubated with propofol was collected. It was found that mitochondrial ratio was decreased and mitochondrial function was impaired. Non-contact co-culture of neuro-astrocytes facilitated transcellular mitochondrial transfer in both physiological and propofol interventions, but failed to reverse propofol-induced neurotoxicity. The more pronounced damage to neuronal mitochondria induced by propofol compared to that in astrocytes alludes to secondary injury. Damaged neurons incubated with large, functional extracellular mitochondria derived from astrocytes demonstrates transfer of mitochondria to neurons, effectively reversing propofol-induced neurotoxicity. This discovery presents a novel mitochondrial transfer of neuro-astrocytes crosstalk that contributes to neuroprotection and neurological recovery in neurotoxicity.

Keywords:  Astrocytes; Mitochondria; Neuron; Neurotoxicity; Propofol

DOI:  https://doi.org/10.1016/j.neulet.2023.137542
Cell Death Dis. 2023 Nov 10. 14(11): 732

SIRT1 inhibits mitochondrial hyperfusion associated mito-bulb formation to sensitize oral cancer cells for apoptosis in a mtROS-dependent signalling pathway.

Srimanta Patra, Amruta Singh, Prakash P Praharaj, Nitish K Mohanta, Mrutyunjay Jena, Birija S Patro, Ali Abusharha, Shankargouda Patil, Sujit K Bhutia.

SIRT1 (NAD-dependent protein deacetylase sirtuin-1), a class III histone deacetylase acting as a tumor suppressor gene, is downregulated in oral cancer cells. Non-apoptotic doses of cisplatin (CDDP) downregulate SIRT1 expression advocating the mechanism of drug resistance. SIRT1 downregulation orchestrates inhibition of DNM1L-mediated mitochondrial fission, subsequently leading to the formation of hyperfused mitochondrial networks. The hyperfused mitochondrial networks preserve the release of cytochrome C (CYCS) by stabilizing the mitochondrial inner membrane cristae (formation of mitochondrial nucleoid clustering mimicking mito-bulb like structures) and reducing the generation of mitochondrial superoxide to inhibit apoptosis. Overexpression of SIRT1 reverses the mitochondrial hyperfusion by initiating DNM1L-regulated mitochondrial fission. In the overexpressed cells, inhibition of mitochondrial hyperfusion and nucleoid clustering (mito-bulbs) facilitates the cytoplasmic release of CYCS along with an enhanced generation of mitochondrial superoxide for the subsequent induction of apoptosis. Further, low-dose priming with gallic acid (GA), a bio-active SIRT1 activator, nullifies CDDP-mediated apoptosis inhibition by suppressing mitochondrial hyperfusion. In this setting, SIRT1 knockdown hinders apoptosis activation in GA-primed oral cancer cells. Similarly, SIRT1 overexpression in the CDDP resistance oral cancer-derived polyploid giant cancer cells (PGCCs) re-sensitizes the cells to apoptosis. Interestingly, synergistically treated with CDDP, GA induces apoptosis in the PGCCs by inhibiting mitochondrial hyperfusion.

DOI: https://doi.org/10.1038/s41419-023-06232-x
Nature. 2023 Nov;623(7986): 283-291

The power and potential of mitochondria transfer.

Nicholas Borcherding, Jonathan R Brestoff.

Mitochondria are believed to have originated through an ancient endosymbiotic process in which proteobacteria were captured and co-opted for energy production and cellular metabolism. Mitochondria segregate during cell division and differentiation, with vertical inheritance of mitochondria and the mitochondrial DNA genome from parent to daughter cells. However, an emerging body of literature indicates that some cell types export their mitochondria for delivery to developmentally unrelated cell types, a process called intercellular mitochondria transfer. In this Review, we describe the mechanisms by which mitochondria are transferred between cells and discuss how intercellular mitochondria transfer regulates the physiology and function of various organ systems in health and disease. In particular, we discuss the role of mitochondria transfer in regulating cellular metabolism, cancer, the immune system, maintenance of tissue homeostasis, mitochondrial quality control, wound healing and adipose tissue function. We also highlight the potential of targeting intercellular mitochondria transfer as a therapeutic strategy to treat human diseases and augment cellular therapies.

DOI: https://doi.org/10.1038/s41586-023-06537-z
Cytoskeleton (Hoboken). 2023 Nov 06.

Regulation of mitochondrial structure by the actin cytoskeleton.

Yihe Wu, Xiaoyu Ren, Peng Shi, Congying Wu.

  Mitochondria are the powerhouse of the cell and play important roles in multiple cellular processes including cell metabolism, proliferation, and programmed cell death. Mitochondria are double-membrane organelles with the inner membrane folding inward to form cristae. Mitochondria networks undergo dynamic fission and fusion. Deregulation of mitochondrial structure has been linked to perturbed mitochondrial membrane potential and disrupted metabolism, as evidenced in tumorigenesis, neurodegenerative diseases, etc. Actin and its motors-myosins have long been known to generate mechanical forces and participate in short-distance cargo transport. Accumulating knowledge from biochemistry and live cell/electron microscope imaging has demonstrated the role of actin filaments in pre-constricting the mitochondria during fission. Recent studies have suggested the involvement of myosins in cristae maintenance and mitochondria quality control. Here, we review current findings and discuss future directions in the emerging fields of cytoskeletal regulation in cristae formation, mitochondrial dynamics, intracellular transport, and mitocytosis, with focus on the actin cytoskeleton and its motor proteins.

Keywords:  actin; cristae structure; mechanical force; mitochondria; myosin

DOI:  https://doi.org/10.1002/cm.21804
Nat Cell Biol. 2023 Nov;25(11): 1625-1636

Mitopherogenesis, a form of mitochondria-specific ectocytosis, regulates sperm mitochondrial quantity and fertility.

Peng Liu, Jing Shi, Danli Sheng, Wenqing Lu, Jie Guo, Lei Gao, Xiaoqing Wang, Shaofeng Wu, Yanwen Feng, Dashan Dong, Xiaoshuai Huang, Hongyun Tang.

Mitochondrial export into the extracellular space is emerging as a fundamental cellular process implicated in diverse physiological activities. Although a few studies have shed light on the process of discarding damaged mitochondria, how mitochondria are exported and the functions of mitochondrial release remain largely unclear. Here we describe mitopherogenesis, a formerly unknown process that specifically secretes mitochondria through a unique extracellular vesicle termed a 'mitopher'. We observed that during sperm development in male Caenorhabditis elegans, healthy mitochondria are exported out of the spermatids through mitopherogenesis and each of the generated mitophers harbours only one mitochondrion. In mitopherogenesis, the plasma membrane first forms mitochondrion-embedding outward buds, which then promptly bud off and thereby result in the generation of mitophers. Mechanistically, extracellular protease signalling in the testis triggers mitopher formation from spermatids, which is partially mediated by the tyrosine kinase SPE-8. Moreover, mitopherogenesis requires normal microfilament dynamics, whereas myosin VI antagonizes mitopher generation. Strikingly, our three-dimensional electron microscopy analyses indicate that mitochondrial quantity requires precise modulation during sperm development, which is critically mediated by mitopherogenesis. Inhibition of mitopherogenesis causes accumulation of mitochondria in sperm, which may lead to sperm motility and fertility defects. Our findings identify mitopherogenesis as a previously undescribed process for mitochondria-specific ectocytosis, which may represent a fundamental branch of mechanisms underlying mitochondrial quantity control to regulate cell functions during development.

DOI: https://doi.org/10.1038/s41556-023-01264-z
Cell Death Dis. 2023 Nov 10. 14(11): 729

Aggregation of alpha-synuclein disrupts mitochondrial metabolism and induce mitophagy via cardiolipin externalization.

Olivier Lurette, Rebeca Martín-Jiménez, Mehtab Khan, Razan Sheta, Stéphanie Jean, Mia Schofield, Maxime Teixeira, Raquel Rodriguez-Aller, Isabelle Perron, Abid Oueslati, Etienne Hebert-Chatelain.

Accumulation of α-synuclein aggregates in the substantia nigra pars compacta is central in the pathophysiology of Parkinson's disease, leading to the degeneration of dopaminergic neurons and the manifestation of motor symptoms. Although several PD models mimic the pathological accumulation of α-synuclein after overexpression, they do not allow for controlling and monitoring its aggregation. We recently generated a new optogenetic tool by which we can spatiotemporally control the aggregation of α-synuclein using a light-induced protein aggregation system. Using this innovative tool, we aimed to characterize the impact of α-synuclein clustering on mitochondria, whose activity is crucial to maintain neuronal survival. We observed that aggregates of α-synuclein transiently and dynamically interact with mitochondria, leading to mitochondrial depolarization, lower ATP production, mitochondrial fragmentation and degradation via cardiolipin externalization-dependent mitophagy. Aggregation of α-synuclein also leads to lower mitochondrial content in human dopaminergic neurons and in mouse midbrain. Interestingly, overexpression of α-synuclein alone did not induce mitochondrial degradation. This work is among the first to clearly discriminate between the impact of α-synuclein overexpression and aggregation on mitochondria. This study thus represents a new framework to characterize the role of mitochondria in PD.

DOI: https://doi.org/10.1038/s41419-023-06251-8
Neurobiol Dis. 2023 Nov 04. pii: S0969-9961(23)00360-1. [Epub ahead of print]188 106344

RICH2 decreases the mitochondrial number and affects mitochondrial localization in diffuse low-grade glioma-related epilepsy.

Jiarui Zhang, Li Gong, Huayu Zhu, Wei Sun, Jing Tian, Yan Zhang, Qiao Liu, Xiaolan Li, Fuqin Zhang, Shumei Wang, Shaojun Zhu, Dongjing Ding, Wei Zhang, Chen Yang.

  Epilepsy, a common complication of diffuse low-grade gliomas (DLGGs; diffuse oligodendroglioma and astrocytoma collectively), severely compromises the quality of life of patients. DLGG epileptogenicity may primarily be generated by interactions between the tumor and the neocortex. Neuronal uptake of dysfunctional mitochondria from the extracellular environment can lead to abnormal neuronal discharge. Mitochondrial dysfunction is frequently observed in gliomas that can transmigrate across the plasma membranes. Here, we examined the role of the Rho GTPase-activating protein 44 (RICH2) in mitochondrial dynamics and DLGG-related epilepsy. We investigated the association between mitochondrial and RICH2 expression in human DLGG tissues using immunohistochemistry. We examined the association between RICH2 and epilepsy in nude mouse glioma models by electrophysiology. The effect of RICH2 on mitochondrial morphology and calcium motility were assessed by single cell fluorescence microscopy. Quantitative RT-PCR (qRT-PCR) and Western blot analysis were performed to characterize RICH2 induced expression changes in the genes related to mitochondrial dynamics, mitogenesis and mitochondrial function. We found that RICH2 expression was higher in oligodendroglioma than in astrocytoma and was correlated with better prognosis and higher epilepsy rate in patients. The expression of mitochondria may be associated with clinical DLGG-related epilepsy and reduced by RICH2 overexpression. And RICH2 could promote DLGG-related epilepsy in tumorigenic nude mice. RICH2 overexpression decreased calcium flow and the mitochondria released from glioma cells (SW1088 and U251) into the extracellular environment, potentially via downregulation of MFN-1/MFN-2 levels which suggests reduced mitochondrial fusion. In addition, we observed decreased mitochondrial trafficking into neurons (released from glioma cells and trafficked into neurons), which could explain the higher incidence of DLGG-related epilepsy due to reduced neuroprotection. Furthermore, RICH2 downregulated MAPK/ERK/HIF-1 pathway. In conclusion, these results suggest that RICH2 could promote epilepsy by (i) inhibiting mitochondrial fusion via MFN downregulation and Drp-1 upregulation; (ii) altering the MAPK/ERK/Hif-1 signaling axis. RICH2 may be a potential target in the treatment of DLGG-related epilepsy.

Keywords:  Diffuse low-grade gliomas (DLGGs); Epilepsy; Hypoxia-inducible factor-1α (HIF-1α); Mitochondrial; Rho GTPase-activating protein 44 (RICH2)

DOI:  https://doi.org/10.1016/j.nbd.2023.106344
Biochem Biophys Res Commun. 2023 Nov 01. pii: S0006-291X(23)01304-9. [Epub ahead of print]687 149210

FUNDC1 collaborates with PINK1 in regulating mitochondrial Fission and compensating for PINK1 deficiency.

Jing Xu, Zhouyang Deng, Shuai Shang, Caifang Wang, Hailong Han.

  Parkinson's disease is presently thought to have its molecular roots in the alteration of PINK1-mediated mitophagy and mitochondrial dynamics. Finding new suppressors of the pathway is essential for developing cutting-edge treatment approaches. Our study shows that FUNDC1 suppressed PINK1 mutant phenotypes in Drosophila. The restoration of PINK1-deficient phenotypes through FUNDC1 is not reliant on its LC3-binding motif Y (18)L (21) or autophagy-related pathway. Moreover, the absence of Drp1 affects the phenotypic restoration of PINK1 mediated by FUNDC1 in flies. In summary, our findings have unveiled a fresh mechanism through which FUNDC1 compensates for the loss of PINK1, operating independently of autophagy but exerting its influence via interaction with Drp1.

Keywords:  Autophagy receptor; Drp1; Mitochondrial dynamics; PD; Ubiquitin-independent mitophagy

DOI:  https://doi.org/10.1016/j.bbrc.2023.149210
Exploration (Beijing). 2023 Oct;3(5): 20230002

Burst of hopping trafficking correlated reversible dynamic interactions between lipid droplets and mitochondria under starvation.

Zhongju Ye, Chengyuan Hu, Junli Wang, Hua Liu, Luping Li, Jie Yuan, Ji Won Ha, Zhaohui Li, Lehui Xiao.

  Dynamic membrane contacts between lipid droplets (LDs) and mitochondria play key roles in lipid metabolism and energy homeostasis. Understanding the dynamics of LDs under energy stimulation is thereby crucial to disclosing the metabolic mechanism. Here, the reversible interactions between LDs and mitochondria are tracked in real-time using a robust LDs-specific fluorescent probe (LDs-Tags). Through tracking the dynamics of LDs at the single-particle level, spatiotemporal heterogeneity is revealed. LDs in starved cells communicate and integrate their activities (i.e., lipid exchange) through a membrane contact site-mediated mechanism. Thus the diffusion is intermittently alternated between active and confined states. Statistical analysis shows that the translocation of LDs in response to starvation stress is non-Gaussian, and obeys nonergodic-like behavior. These results provide deep understanding of the anomalous diffusion of LDs in living cells, and also afford guidance for rationally designing efficient transporter.

Keywords:  dynamic contact; fluorescence imaging; lipid droplet; mitochondrion; single‐particle tracking

DOI:  https://doi.org/10.1002/EXP.20230002
J Cell Biol. 2024 Jan 01. pii: e202206109. [Epub ahead of print]223(1):

Membrane contact site detection (MCS-DETECT) reveals dual control of rough mitochondria-ER contacts.

Ben Cardoen, Kurt R Vandevoorde, Guang Gao, Milene Ortiz-Silva, Parsa Alan, William Liu, Ellie Tiliakou, A Wayne Vogl, Ghassan Hamarneh, Ivan R Nabi.

Identification and morphological analysis of mitochondria-ER contacts (MERCs) by fluorescent microscopy is limited by subpixel resolution interorganelle distances. Here, the membrane contact site (MCS) detection algorithm, MCS-DETECT, reconstructs subpixel resolution MERCs from 3D super-resolution image volumes. MCS-DETECT shows that elongated ribosome-studded riboMERCs, present in HT-1080 but not COS-7 cells, are morphologically distinct from smaller smooth contacts and larger contacts induced by mitochondria-ER linker expression in COS-7 cells. RiboMERC formation is associated with increased mitochondrial potential, reduced in Gp78 knockout HT-1080 cells and induced by Gp78 ubiquitin ligase activity in COS-7 and HeLa cells. Knockdown of riboMERC tether RRBP1 eliminates riboMERCs in both wild-type and Gp78 knockout HT-1080 cells. By MCS-DETECT, Gp78-dependent riboMERCs present complex tubular shapes that intercalate between and contact multiple mitochondria. MCS-DETECT of 3D whole-cell super-resolution image volumes, therefore, identifies novel dual control of tubular riboMERCs, whose formation is dependent on RRBP1 and size modulated by Gp78 E3 ubiquitin ligase activity.

DOI: https://doi.org/10.1083/jcb.202206109
J Cell Physiol. 2023 Nov 09.

NDP52 SUMOylation contributes to low-dose X-rays-induced cardiac hypertrophy through PINK1/Parkin-mediated mitophagy via MUL1/SUMO2 signalling.

Anbo Gao, Mengjie Wang, Xing Tang, Gangqing Shi, Kai Hou, Jinren Fang, Linlin Zhou, Hong Zhou, Weimin Jiang, Yukun Li, Fan Ouyang.

  Radiation-induced heart damage caused by low-dose X-rays has a significant impact on tumour patients' prognosis, with cardiac hypertrophy being the most severe noncarcinogenic adverse effect. Our previous study demonstrated that mitophagy activation promoted cardiac hypertrophy, but the underlying mechanisms remained unclear. In the present study, PARL-IN-1 enhanced excessive hypertrophy of cardiomyocytes and exacerbated mitochondrial damage. Isobaric tags for relative and absolute quantification-based quantitative proteomics identified NDP52 as a crucial target mediating cardiac hypertrophy induced by low-dose X-rays. SUMOylation proteomics revealed that the SUMO E3 ligase MUL1 facilitated NDP52 SUMOylation through SUMO2. Co-IP coupled with LC-MS/MS identified a critical lysine residue at position 262 of NDP52 as the key site for SUMO2-mediated SUMOylation of NDP52. The point mutation plasmid NDP52K262R inhibited mitophagy under MUL1 overexpression, as evidenced by inhibition of LC3 interaction with NDP52, PINK1 and LAMP2A. A mitochondrial dissociation study revealed that NDP52K262R inhibited PINK1 targeting to endosomes early endosomal marker (EEA1), late/lysosome endosomal marker (LAMP2A) and recycling endosomal marker (RAB11), and laser confocal microscopy confirmed that NDP52K262R impaired the recruitment of mitochondria to the autophagic pathway through EEA1/RAB11 and ATG3, ATG5, ATG16L1 and STX17, but did not affect mitochondrial delivery to lysosomes via LAMP2A for degradation. In conclusion, our findings suggest that MUL1-mediated SUMOylation of NDP52 plays a crucial role in regulating mitophagy in the context of low-dose X-ray-induced cardiac hypertrophy. Two hundred sixty-second lysine of NDP52 is identified as a key SUMOylation site for low-dose X-ray promoting mitophagy activation and cardiac hypertrophy. Collectively, this study provides novel implications for the development of therapeutic strategies aimed at preventing the progression of cardiac hypertrophy induced by low-dose X-rays.

Keywords:  MUL1; NDP52; PINK1/Parkin; SUMOylation; mitophagy; radiation-induced heart damage

DOI:  https://doi.org/10.1002/jcp.31145
Cell Metab. 2023 Nov 07. pii: S1550-4131(23)00380-7. [Epub ahead of print]35(11): 1872-1886

Mitohormesis.

Yu-Wei Cheng, Jie Liu, Toren Finkel.

Perturbation of mitochondrial function can trigger a host of cellular responses that seek to restore cellular metabolism, cytosolic proteostasis, and redox homeostasis. In some cases, these responses persist even after the stress is relieved, leaving the cell or tissue in a less vulnerable state. This process-termed mitohormesis-is increasingly viewed as an important aspect of normal physiology and a critical modulator of various disease processes. Here, we review aspects of mitochondrial stress signaling that, among other things, can rewire the cell's metabolism, activate the integrated stress response, and alter cytosolic quality-control pathways. We also discuss how these pathways are implicated in various disease states from pathogen challenge to chemotherapeutic resistance and how their therapeutic manipulation can lead to new strategies for a host of chronic conditions including aging itself.

DOI: https://doi.org/10.1016/j.cmet.2023.10.011
J Lipid Res. 2023 Nov 08. pii: S0022-2275(23)00146-3. [Epub ahead of print] 100473

Ola1p trafficking indicates an interaction network between mitochondria, Lipid droplets and stress granules in times of stress.

Melanie Kovacs, Florian Geltinger, Lukas Schartel, Simon Pöschl, Peter Briza, Manuel Paschinger, Kitti Boros, Thomas Klaus Felder, Herbert Wimmer, Jutta Duschl, Mark Rinnerthaler.

  Protein aggregates arise naturally under normal physiological conditions, but their formation is accelerated by age or stress-induced protein misfolding. When the stressful event dissolves, these aggregates are removed by mechanisms such as aggrephagy, chaperone-mediated autophagy, refolding attempts, or the proteasome. It was recently shown that mitochondria in yeast cells may support these primarily cytosolic processes. Protein aggregates attach to mitochondria and misfolded proteins are transported into the matrix and degraded by mitochondria-specific proteases. Using a proximity labelling method and colocalization with an established stress granule marker, we were able to show that these mitochondria localized aggregates that harbor the "super aggregator" Ola1p are, in fact, stress granules (SGs). Our in vivo and in vitro studies have revealed that Ola1p can be transferred from mitochondria to lipid droplets (LDs). This "mitochondria to LD" aggregate transfer dampens proteotoxic effects. The LD-based protein aggregate removal system gains importance when other proteolytic systems fail. Furthermore, we were able to show that the distribution of SGs is drastically altered in LD-deficient yeast cells, demonstrating that LDs play a role in the SG life cycle.

Keywords:  Lipids/oxidation; Triacylglycerol; apoptosis; mitochondria; protein aggregation; protein detoxification; protein shuttling; stress response: Lipid droplets

DOI:  https://doi.org/10.1016/j.jlr.2023.100473
ACS Nano. 2023 Nov 06.

Adaptive Nanoparticle-Mediated Modulation of Mitochondrial Homeostasis and Inflammation to Enhance Infected Bone Defect Healing.

Xu Chen, Qingqing He, Qiming Zhai, Han Tang, Dize Li, Xingyu Zhu, Xinhui Zheng, Guangyu Jian, Richard D Cannon, Li Mei, Shan Wang, Ping Ji, Jinlin Song, Tao Chen.

  Infected bone defects (IBDs) exhibit impaired healing due to excessive inflammation triggered by pathogen-associated molecular patterns (PAMPs) from bacteria. As a vital factor in orchestrating immune responses, mitochondrial homeostasis maintenance is central to inflammation blockade. This research developed a chameleon-like nanoplatform by covering hydroxyapatite nanoparticles with a cerium ion coordinated tannic acid supramolecular network (HA@Ce-TA), which adaptively functions to regulate mitochondrial homeostasis based on intra- and extracellular environments. Extracellularly, acidic conditions activate HA@Ce-TA's peroxidase/oxidase-mimicking activity to produce reactive oxygen species (ROS), and external near-infrared (NIR) irradiation excites nanoscale Ce-TA to produce hyperthermia, which is found and explained by chemical computation. ROS production with photothermal therapy can eliminate bacteria effectively and reduce mitochondrial stress. Intracellularly, HA@Ce-TA remodels mitochondrial dynamics by upregulating mitochondrial fusion genes and eliminates excessive ROS by mimicking superoxidase/catalase. Consequently, this comprehensive modulation of mitochondrial homeostasis inhibits inflammasome overactivation. In vitro and in vivo studies showed HA@Ce-TA can modulate the mitochondria-centered inflammatory cascade to enhance IBD treatment, highlighting the potential of engineering nanotherapeutics to recalibrate mitochondrial homeostasis as an infected disease-modifying intervention.

Keywords:  PAMPs clerance; adaptive nanoparticles; immunomodulation; infected bone defects; mitochondrial homeostasis

DOI:  https://doi.org/10.1021/acsnano.3c08165
Cell Mol Life Sci. 2023 Nov 06. 80(12): 347

Tubular TMEM16A promotes tubulointerstitial fibrosis by suppressing PGC-1α-mediated mitochondrial homeostasis in diabetic kidney disease.

Jia-Ling Ji, Jun-Ying Li, Jian-Xiang Liang, Yan Zhou, Cong-Cong Liu, Yao Zhang, Ai-Qing Zhang, Hong Liu, Rui-Xia Ma, Zuo-Lin Li.

  Tubulointerstitial fibrosis (TIF) plays a crucial role in the progression of diabetic kidney disease (DKD). However, the underlying molecular mechanisms remain obscure. The present study aimed to examine whether transmembrane member 16A (TMEM16A), a Ca2+-activated chloride channel, contributes to the development of TIF in DKD. Interestingly, we found that TMEM16A expression was significantly up-regulated in tubule of murine model of DKD, which was associated with development of TIF. In vivo inhibition of TMEM16A channel activity with specific inhibitors Ani9 effectively protects against TIF. Then, we found that TMEM16A activation induces tubular mitochondrial dysfunction in in vivo and in vitro models, with the evidence of the TMEM16A inhibition with specific inhibitor. Mechanically, TMEM16A mediated tubular mitochondrial dysfunction through inhibiting PGC-1α, whereas overexpression of PGC-1α could rescue the changes. In addition, TMEM16A-induced fibrogenesis was dependent on increased intracellular Cl-, and reducing intracellular Cl- significantly blunted high glucose-induced PGC-1α and profibrotic factors expression. Taken together, our studies demonstrated that tubular TMEM16A promotes TIF by suppressing PGC-1α-mediated mitochondrial homeostasis in DKD. Blockade of TMEM16A may serve as a novel therapeutic approach to ameliorate TIF.

Keywords:  Intracellular Cl−; Mitochondrial dysfunction; PGC-1α; TMEM16A; Tubulointerstitial fibrosis

DOI:  https://doi.org/10.1007/s00018-023-05000-6
Trends Analyt Chem. 2023 Dec;pii: 117370. [Epub ahead of print]169

Probing the dynamic crosstalk of lysosomes and mitochondria with structured illumination microscopy.

Xiuqiong Xu, Kangqiang Qiu, Zhiqi Tian, Chinta Aryal, Fiona Rowan, Rui Chen, Yujie Sun, Jiajie Diao.

  Structured illumination microscopy (SIM) is a super-resolution technology for imaging living cells and has been used for studying the dynamics of lysosomes and mitochondria. Recently, new probes and analyzing methods have been developed for SIM imaging, enabling the quantitative analysis of these subcellular structures and their interactions. This review provides an overview of the working principle and advances of SIM, as well as the organelle-targeting principles and types of fluorescence probes, including small molecules, metal complexes, nanoparticles, and fluorescent proteins. Additionally, quantitative methods based on organelle morphology and distribution are outlined. Finally, the review provides an outlook on the current challenges and future directions for improving the combination of SIM imaging and image analysis to further advance the study of organelles. We hope that this review will be useful for researchers working in the field of organelle research and help to facilitate the development of SIM imaging and analysis techniques.

Keywords:  Fluorescence imaging; Lysosomal clusters; Mitochondrial morphology; Nanoprobes; Quantitative analysis

DOI:  https://doi.org/10.1016/j.trac.2023.117370
Redox Biol. 2023 Oct 24. pii: S2213-2317(23)00347-6. [Epub ahead of print]68 102946

Non-steroidal mineralocorticoid receptor antagonist finerenone ameliorates mitochondrial dysfunction via PI3K/Akt/eNOS signaling pathway in diabetic tubulopathy.

Lan Yao, Xianhui Liang, Yamin Liu, Bingyu Li, Mei Hong, Xin Wang, Bohan Chen, Zhangsuo Liu, Pei Wang.

  Diabetic tubulopathy (DT) is a recently recognized key pathology of diabetic kidney disease (DKD). The mitochondria-centric view of DT is emerging as a vital pathological factor in different types of metabolic diseases, such as DKD. Finerenone (FIN), a novel non-steroidal mineralocorticoid receptor antagonist, attenuates kidney inflammation and fibrosis in DKD, but the precise pathomechanisms remain unclear. The role of mineralocorticoid receptor (MR) in perturbing mitochondrial function via the PI3K/Akt/eNOS signaling pathway, including mitochondrial dynamics and mitophagy, was investigated under a diabetic state and high glucose (HG) ambiance. To elucidate how the activation of MR provokes mitochondrial dysfunction in DT, human kidney proximal tubular epithelial (HK-2) cells were exposed to HG, and then mitochondrial dynamics, mitophagy, mitochondrial ROS (mitoROS), signaling molecules PI3K, Akt, Akt phosphorylation and eNOS were probed. The above molecules or proteins were also explored in the kidneys of diabetic and FIN-treated mice. FIN treatment reduced oxidative stress, mitochondrial fragmentation, and apoptosis while restoring the mitophagy via PI3K/Akt/eNOS signaling pathway in HK-2 cells exposed to HG ambiance and tubular cells of DM mice. These findings linked MR activation to mitochondrial dysfunction via PI3K/Akt/eNOS signaling pathway in DT and highlight a pivotal but previously undiscovered role of FIN in alleviating renal tubule injury for the treatment of DKD.

Keywords:  Diabetic kidney disease; Diabetic tubulopathy; Finerenone; Nonsteroidal mineralocorticoid receptor antagonist; PI3K/Akt/eNOS signaling pathway

DOI:  https://doi.org/10.1016/j.redox.2023.102946
Front Endocrinol (Lausanne). 2023 ;14 1236472

Mitochondrial regulation in human pluripotent stem cells during reprogramming and β cell differentiation.

Ila Tewari Jasra, Nerea Cuesta-Gomez, Kevin Verhoeff, Braulio A Marfil-Garza, Nidheesh Dadheech, A M James Shapiro.

  Mitochondria are the powerhouse of the cell and dynamically control fundamental biological processes including cell reprogramming, pluripotency, and lineage specification. Although remarkable progress in induced pluripotent stem cell (iPSC)-derived cell therapies has been made, very little is known about the role of mitochondria and the mechanisms involved in somatic cell reprogramming into iPSC and directed reprogramming of iPSCs in terminally differentiated cells. Reprogramming requires changes in cellular characteristics, genomic and epigenetic regulation, as well as major mitochondrial metabolic changes to sustain iPSC self-renewal, pluripotency, and proliferation. Differentiation of autologous iPSC into terminally differentiated β-like cells requires further metabolic adaptation. Many studies have characterized these alterations in signaling pathways required for the generation and differentiation of iPSC; however, very little is known regarding the metabolic shifts that govern pluripotency transition to tissue-specific lineage differentiation. Understanding such metabolic transitions and how to modulate them is essential for the optimization of differentiation processes to ensure safe iPSC-derived cell therapies. In this review, we summarize the current understanding of mitochondrial metabolism during somatic cell reprogramming to iPSCs and the metabolic shift that occurs during directed differentiation into pancreatic β-like cells.

Keywords:  Diabetes Mellitus; beta cells (β Cells); induced pluripotent stem (iPS) cells; islet transplantation; stem cells

DOI:  https://doi.org/10.3389/fendo.2023.1236472