bims-midtic 2023-06-04 papers

bims-midtic

Biomed News

on Mitochondrial dynamics and trafficking in cells

Issue of 2023–06–04
thirteen papers selected by
Omkar Joshi, Turku Bioscience

Mitochondria as central hubs in synaptic modulation.
Methods for Monitoring Mitochondrial Biogenesis and Turnover in Cultured Hepatocytes and Mouse Liver Using MitoTimer Reporter Assay.
Pseudolaric acid B triggers cell apoptosis by activating AMPK/JNK/DRP1/mitochondrial fission pathway in hepatocellular carcinoma.
Mitochondria-associated endoplasmic reticulum membranes (MAMs) and their role in glaucomatous retinal ganglion cell degeneration-a mini review.
Fluorescence-Based Quantification of Mitochondrial Membrane Potential and Superoxide Levels using Live Imaging in HeLa Cells.
Structural basis of purine nucleotide inhibition of human uncoupling protein 1.
Role of UPRmt and mitochondrial dynamics in host immunity: it takes two to tango.
Is Drp1 a link between mitochondrial dysfunction and inflammation in Alzheimer's disease?
Cytochrome c oxidase biogenesis - from translation to early assembly of the core subunit COX1.
HDAC3 deficiency protects against acute lung injury by maintaining epithelial barrier integrity through preserving mitochondrial quality control.
Assessment of Metabolic Pathways and Parameters in Extracellular Matrix-Detached Cells.
The E3 ubiquitin ligase FBXL6 controls the quality of newly synthesized mitochondrial ribosomal proteins.
Side effects of antibiotics and perturbations of mitochondria functions.

Cell Mol Life Sci. 2023 Jun 02. 80(6): 173

Mitochondria as central hubs in synaptic modulation.

Filipe V Duarte, Daniele Ciampi, Carlos B Duarte.

  Mitochondria are present in the pre- and post-synaptic regions, providing the energy required for the activity of these very specialized neuronal compartments. Biogenesis of synaptic mitochondria takes place in the cell body, and these organelles are then transported to the synapse by motor proteins that carry their cargo along microtubule tracks. The transport of mitochondria along neurites is a highly regulated process, being modulated by the pattern of neuronal activity and by extracellular cues that interact with surface receptors. These signals act by controlling the distribution of mitochondria and by regulating their activity. Therefore, mitochondria activity at the synapse allows the integration of different signals and the organelles are important players in the response to synaptic stimulation. Herein we review the available evidence regarding the regulation of mitochondrial dynamics by neuronal activity and by neuromodulators, and how these changes in the activity of mitochondria affect synaptic communication.

Keywords:  Cannabinoid receptors; Intracellular signalling; Intracellular trafficking; Mitochondria; Neurotrophins; Synaptic regulation

DOI:  https://doi.org/10.1007/s00018-023-04814-8
Methods Mol Biol. 2023 ;2675 97-107

Methods for Monitoring Mitochondrial Biogenesis and Turnover in Cultured Hepatocytes and Mouse Liver Using MitoTimer Reporter Assay.

Xiaowen Ma, Wen-Xing Ding.

  Mitochondrial biogenesis and turnover rate are critical to maintain homeostasis of the intracellular mitochondrial pool. Altered mitochondrial biogenesis and mitophagy are closely related to many chronic diseases, highlighting the importance of mitochondrial stasis in various pathological conditions including liver diseases. We describe a detailed protocol for monitoring mitochondrial lifecycle in primary cultured mouse hepatocytes and mouse liver using the dual color fluorescence-based imaging of MitoTimer. Three types of mitochondria were visualized in mouse hepatocytes: green-only mitochondria (newly synthesized mitochondria), red-only mitochondria (old/aging mitochondria), as well as the majority of yellow mitochondria (representing an intermediate stage of mitochondria). The ratio of red/green fluorescence in each cell will be used to track mitochondrial aging. Super-resolution microscopy analysis revealed that majority of mitochondria were spatially heterogeneous with proteins from simultaneous new synthesis, maturation, and turnover in hepatocytes. MitoTimer reporter assay can specifically target to mitochondria and be used to monitor mitochondrial biogenesis and maturation as well as turnover in vitro and in vivo.

Keywords:  Hepatocytes; Liver; MitoTimer; Mitophagy; Quality control

DOI:  https://doi.org/10.1007/978-1-0716-3247-5_8
Toxicology. 2023 May 25. pii: S0300-483X(23)00142-7. [Epub ahead of print]493 153556

Pseudolaric acid B triggers cell apoptosis by activating AMPK/JNK/DRP1/mitochondrial fission pathway in hepatocellular carcinoma.

Zhanxu Liu, Nanya Wang, Zhaoli Meng, Shiying Lu, Gong Peng.

  Pseudolaric acid B (PAB), a natural product isolated from the root bark of Pseudolarix kaempferi, has been reported to exert inhibitory effects in various cancers. However, the underlying mechanisms remain largely unclear. In the present study, we investigated the mechanism through which PAB exert its anticancer effects in hepatocellular carcinoma (HCC). PAB inhibited the viability of and induced apoptosis in Hepa1-6 cells in a dose-dependent manner. It disrupted mitochondrial membrane potential (MMP) and impaired ATP production. Furthermore, PAB induced phosphorylation of DRP1 at Ser616 and mitochondrial fission. Blocking DRP1 phosphorylation by Mdivi-1 inhibited mitochondrial fission and PAB-induced apoptosis. Moreover, c-Jun N-terminal kinase (JNK) was activated by PAB, and blocking JNK activity using SP600125 inhibited PAB-induced mitochondrial fission and cell apoptosis. Furthermore, PAB activated AMP-activated protein kinase (AMPK), and inhibiting AMPK by compound C attenuated PAB-stimulated JNK activation and blocked DRP1-dependent mitochondrial fission and apoptosis. Our in vivo data confirmed that PAB inhibited tumor growth and induced apoptosis in an HCC syngeneic mouse model by inducing the AMPK/JNK/DRP1/mitochondrial fission signaling pathway. Furthermore, a combination of PAB and sorafenib showed a synergistic effect in inhibiting tumor growth in vivo. Taken together, our findings highlight a potential therapeutic strategy for HCC.

Keywords:  Apoptosis; Dynamin-related protein 1; Hepatocellular carcinoma; Mitochondrial fission; Pseudolaric acid B

DOI:  https://doi.org/10.1016/j.tox.2023.153556
Front Neurosci. 2023 ;17 1198343

Mitochondria-associated endoplasmic reticulum membranes (MAMs) and their role in glaucomatous retinal ganglion cell degeneration-a mini review.

Jennifer H Pham, Dorota L Stankowska.

  Glaucoma is a leading cause of blindness worldwide, commonly associated with elevated intraocular pressure (IOP), leading to degeneration of the optic nerve and death of retinal ganglion cells, the output neurons in the eye. In recent years, many studies have implicated mitochondrial dysfunction as a crucial player in glaucomatous neurodegeneration. Mitochondrial function has been an increasingly researched topic in glaucoma, given its vital role in bioenergetics and propagation of action potentials. One of the most metabolically active tissues in the body characterized by high oxygen consumption is the retina, particularly the retinal ganglion cells (RGCs). RGCs, which have long axons that extend from the eyes to the brain, rely heavily on the energy generated by oxidative phosphorylation for signal transduction, rendering them more vulnerable to oxidative damage. In various glaucoma models, mitochondrial dysfunction and stress from protein aggregates in the endoplasmic reticulum (ER) have been observed in the RGCs. However, it has been shown that the two organelles are connected through a network called mitochondria-associated ER membranes (MAMs); hence this crosstalk in a pathophysiological condition such as glaucoma should be evaluated. Here, we review the current literature suggestive of mitochondrial and ER stress related to glaucoma, indicating potential cross-signaling and the potential roles of MAMs.

Keywords:  ER stress; MAMs; endoplasmic reticulum; glaucoma; inflammation; mitochondria; oxidative stress; retinal ganglion cells

DOI:  https://doi.org/10.3389/fnins.2023.1198343
J Vis Exp. 2023 05 12.

Fluorescence-Based Quantification of Mitochondrial Membrane Potential and Superoxide Levels using Live Imaging in HeLa Cells.

Mohammad Fazli, Chantell S Evans.

Mitochondria are dynamic organelles critical for metabolic homeostasis by controlling energy production via ATP synthesis. To support cellular metabolism, various mitochondrial quality control mechanisms cooperate to maintain a healthy mitochondrial network. One such pathway is mitophagy, where PTEN-induced kinase 1 (PINK1) and Parkin phospho-ubiquitination of damaged mitochondria facilitate autophagosome sequestration and subsequent removal from the cell via lysosome fusion. Mitophagy is important for cellular homeostasis, and mutations in Parkin are linked to Parkinson's disease (PD). Due to these findings, there has been a significant emphasis on investigating mitochondrial damage and turnover to understand the molecular mechanisms and dynamics of mitochondrial quality control. Here, live-cell imaging was used to visualize the mitochondrial network of HeLa cells, to quantify the mitochondrial membrane potential and superoxide levels following treatment with carbonyl cyanide m-chlorophenyl hydrazone (CCCP), a mitochondrial uncoupling agent. In addition, a PD-linked mutation of Parkin (ParkinT240R) that inhibits Parkin-dependent mitophagy was expressed to determine how mutant expression impacts the mitochondrial network compared to cells expressing wild-type Parkin. The protocol outlined here describes a simple workflow using fluorescence-based approaches to quantify mitochondrial membrane potential and superoxide levels effectively.

DOI: https://doi.org/10.3791/65304
Sci Adv. 2023 Jun 02. 9(22): eadh4251

Structural basis of purine nucleotide inhibition of human uncoupling protein 1.

Scott A Jones, Prerana Gogoi, Jonathan J Ruprecht, Martin S King, Yang Lee, Thomas Zögg, Els Pardon, Deepak Chand, Stefan Steimle, Danielle M Copeman, Camila A Cotrim, Jan Steyaert, Paul G Crichton, Vera Moiseenkova-Bell, Edmund R S Kunji.

Mitochondrial uncoupling protein 1 (UCP1) gives brown adipose tissue of mammals its specialized ability to burn calories as heat for thermoregulation. When activated by fatty acids, UCP1 catalyzes the leak of protons across the mitochondrial inner membrane, short-circuiting the mitochondrion to generate heat, bypassing ATP synthesis. In contrast, purine nucleotides bind and inhibit UCP1, regulating proton leak by a molecular mechanism that is unclear. We present the cryo-electron microscopy structure of the GTP-inhibited state of UCP1, which is consistent with its nonconducting state. The purine nucleotide cross-links the transmembrane helices of UCP1 with an extensive interaction network. Our results provide a structural basis for understanding the specificity and pH dependency of the regulatory mechanism. UCP1 has retained all of the key functional and structural features required for a mitochondrial carrier-like transport mechanism. The analysis shows that inhibitor binding prevents the conformational changes that UCP1 uses to facilitate proton leak.

DOI: https://doi.org/10.1126/sciadv.adh4251
Front Cell Infect Microbiol. 2023 ;13 1135203

Role of UPRmt and mitochondrial dynamics in host immunity: it takes two to tango.

Manmohan Kumar, Shagun Sharma, Shibnath Mazumder.

  The immune system of a host contains a group of heterogeneous cells with the prime aim of restraining pathogenic infection and maintaining homeostasis. Recent reports have proved that the various subtypes of immune cells exploit distinct metabolic programs for their functioning. Mitochondria are central signaling organelles regulating a range of cellular activities including metabolic reprogramming and immune homeostasis which eventually decree the immunological fate of the host under pathogenic stress. Emerging evidence suggests that following bacterial infection, innate immune cells undergo profound metabolic switching to restrain and countervail the bacterial pathogens, promote inflammation and restore tissue homeostasis. On the other hand, bacterial pathogens affect mitochondrial structure and functions to evade host immunity and influence their intracellular survival. Mitochondria employ several mechanisms to overcome bacterial stress of which mitochondrial UPR (UPRmt) and mitochondrial dynamics are critical. This review discusses the latest advances in our understanding of the immune functions of mitochondria against bacterial infection, particularly the mechanisms of mitochondrial UPRmt and mitochondrial dynamics and their involvement in host immunity.

Keywords:  ATFS-1; DRP1; MFN1; MFN2; UPRmt; bacterial infection; mitochondrial dynamics

DOI:  https://doi.org/10.3389/fcimb.2023.1135203
Front Mol Neurosci. 2023 ;16 1166879

Is Drp1 a link between mitochondrial dysfunction and inflammation in Alzheimer's disease?

Oualid Sbai, Veronica Bazzani, Shreya Tapaswi, Joshua McHale, Carlo Vascotto, Lorena Perrone.

  Recent advances highlight that inflammation is critical to Alzheimer Disease (AD) pathogenesis. Indeed, several diseases characterized by inflammation are considered risk factors for AD, such as type 2 diabetes, obesity, hypertension, and traumatic brain injury. Moreover, allelic variations in genes involved in the inflammatory cascade are risk factors for AD. AD is also characterized by mitochondrial dysfunction, which affects the energy homeostasis of the brain. The role of mitochondrial dysfunction has been characterized mostly in neuronal cells. However, recent data are demonstrating that mitochondrial dysfunction occurs also in inflammatory cells, promoting inflammation and the secretion of pro-inflammatory cytokines, which in turn induce neurodegeneration. In this review, we summarize the recent finding supporting the hypothesis of the inflammatory-amyloid cascade in AD. Moreover, we describe the recent data that demonstrate the link between altered mitochondrial dysfunction and the inflammatory cascade. We focus in summarizing the role of Drp1, which is involved in mitochondrial fission, showing that altered Drp1 activation affects the mitochondrial homeostasis and leads to the activation of the NLRP3 inflammasome, promoting the inflammatory cascade, which in turn aggravates Amyloid beta (Ab) deposition and tau-induced neurodegeneration, showing the relevance of this pro-inflammatory pathway as an early event in AD.

Keywords:  Alzheimer inflammation; DRP1; NLRP3; TXNIP; mitochondria

DOI:  https://doi.org/10.3389/fnmol.2023.1166879
FEBS Lett. 2023 May 29.

Cytochrome c oxidase biogenesis - from translation to early assembly of the core subunit COX1.

Sven Dennerlein, Peter Rehling, Ricarda Richter-Dennerlein.

  Mitochondria are the powerhouses of the cell as they produce the majority of ATP with their oxidative phosphorylation (OXPHOS) machinery. The OXPHOS system is composed of the F1 Fo ATP synthase and four mitochondrial respiratory chain complexes, the terminal enzyme of which is the cytochrome c oxidase (complex IV) that transfers electrons to oxygen, generating water. Complex IV comprises of 14 structural subunits of dual genetic origin: while the three core subunits are mitochondrial encoded, the remaining constituents are encoded by the nuclear genome. Hence, the assembly of complex IV requires the coordination of two spatially separated gene expression machinery. Recent efforts elucidated an increasing number of proteins involved in mitochondrial gene expression, which are linked to complex IV assembly. Additionally, several COX1 biogenesis factors have been intensively biochemically investigated and an increasing number of structural snapshots shed light on the organization of macromolecular complexes such as the mitoribosome or the cytochrome c oxidase. Here, we focus on COX1 translation regulation and highlight the advanced understanding of early steps during COX1 assembly and its link to mitochondrial translation regulation.

Keywords:  COX1; OXPHOS; complex IV; cytochrome c oxidase; mitochondria

DOI:  https://doi.org/10.1002/1873-3468.14671
Redox Biol. 2023 May 20. pii: S2213-2317(23)00147-7. [Epub ahead of print]63 102746

HDAC3 deficiency protects against acute lung injury by maintaining epithelial barrier integrity through preserving mitochondrial quality control.

Ning Li, Bohao Liu, Rui Xiong, Guorui Li, Bo Wang, Qing Geng.

  Sepsis is one common cause of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), which is closely associated with high mortality in intensive care units (ICU). Histone deacetylase 3 (HDAC3) serves as an important epigenetic modifying enzyme which could affect chromatin structure and transcriptional regulation. Here, we explored the effects of HDAC3 in type II alveolar epithelial cells (AT2) on lipopolysaccharide (LPS)-induced ALI and shed light on potential molecular mechanisms. We generated ALI mouse model with HDAC3 conditional knockout mice (Sftpc-cre; Hdac3f/f) in AT2 and the roles of HDAC3 in ALI and epithelial barrier integrity were investigated in LPS-treated AT2. The levels of HDAC3 were significantly upregulated in lung tissues from mice with sepsis and in LPS-treated AT2. HDAC3 deficiency in AT2 not only decreased inflammation, apoptosis, and oxidative stress, but also maintained epithelial barrier integrity. Meanwhile, HDAC3 deficiency in LPS-treated AT2 preserved mitochondrial quality control (MQC), evidenced by the shift of mitochondria from fission into fusion, decreased mitophagy, and improved fatty acid oxidation (FAO). Mechanically, HDAC3 promoted the transcription of Rho-associated protein kinase 1 (ROCK1) in AT2. In the context of LPS stimulation, the upregulated ROCK1 elicited by HDAC3 could be phosphorylated by Rho-associated (RhoA), thus disturbing MQC and triggering ALI. Furthermore, we found that forkhead box O1 (FOXO1) was one of transcription factors of ROCK1. HDAC3 directly decreased the acetylation of FOXO1 and promoted its nuclear translocation in LPS-treated AT2. Finally, HDAC3 inhibitor RGFP966 alleviated epithelial damage and improved MQC in LPS-treated AT2. Altogether, HDAC3 deficiency in AT2 alleviated sepsis-induced ALI by preserving mitochondrial quality control via FOXO1-ROCK1 axis, which provided a potential strategy for the treatment of sepsis and ALI.

Keywords:  Acute lung injury; Epithelial barrier; Forkhead box O1; Histone deacetylase 3; Mitochondrial quality control

DOI:  https://doi.org/10.1016/j.redox.2023.102746
Methods Mol Biol. 2023 ;2675 309-315

Assessment of Metabolic Pathways and Parameters in Extracellular Matrix-Detached Cells.

Lisa M Hom, Zachary T Schafer.

Changes in metabolism can alter a variety of distinct cellular parameters in a number of physiological and pathological contexts. Relatedly, the loss of integrin-mediated attachment to extracellular matrix (ECM) is now appreciated to alter metabolism in a variety of distinct fashions. As such, assays to quantify and assess metabolism during ECM detachment are critical to better understanding the cellular and molecular changes that impact the behavior and survival of ECM-detached cells. Here, we discuss assays and approaches commonly used to study metabolism during ECM detachment.

DOI: https://doi.org/10.1007/978-1-0716-3247-5_23
Cell Rep. 2023 May 31. pii: S2211-1247(23)00590-9. [Epub ahead of print]42(6): 112579

The E3 ubiquitin ligase FBXL6 controls the quality of newly synthesized mitochondrial ribosomal proteins.

Julie Lavie, Claude Lalou, Walid Mahfouf, Jean-William Dupuy, Aurélie Lacaule, Agata Ars Cywinska, Didier Lacombe, Anne-Marie Duchêne, Anne-Aurélie Raymond, Hamid Reza Rezvani, Richard Patryk Ngondo, Giovanni Bénard.

  In mammals, about 99% of mitochondrial proteins are synthesized in the cytosol as precursors that are subsequently imported into the organelle. The mitochondrial health and functions rely on an accurate quality control of these imported proteins. Here, we show that the E3 ubiquitin ligase F box/leucine-rich-repeat protein 6 (FBXL6) regulates the quality of cytosolically translated mitochondrial proteins. Indeed, we found that FBXL6 substrates are newly synthesized mitochondrial ribosomal proteins. This E3 binds to chaperones involved in the folding and trafficking of newly synthesized peptide and to ribosomal-associated quality control proteins. Deletion of these interacting partners is sufficient to hamper interactions between FBXL6 and its substrate. Furthermore, we show that cells lacking FBXL6 fail to degrade specifically mistranslated mitochondrial ribosomal proteins. Finally, showing the role of FBXL6-dependent mechanism, FBXL6-knockout (KO) cells display mitochondrial ribosomal protein aggregations, altered mitochondrial metabolism, and inhibited cell cycle in oxidative conditions.

Keywords:  CP: Cell biology; F box leucin-rich repeat E3 ubiquitin ligase; FBXL6; mitochondria; protein quality control; ribosomal proteins

DOI:  https://doi.org/10.1016/j.celrep.2023.112579
Int Rev Cell Mol Biol. 2023 ;pii: S1937-6448(23)00029-1. [Epub ahead of print]377 121-139

Side effects of antibiotics and perturbations of mitochondria functions.

Gloria D'Achille, Gianluca Morroni.

  Antibiotics are one of the greatest discoveries of medicine of the past century. Despite their invaluable contribution to infectious disease, their administration could lead to side effects that in some cases are serious. The toxicity of some antibiotics is in part due to their interaction with mitochondria: these organelles derive from a bacterial ancestor and possess specific translation machinery that shares similarities with the bacterial counterpart. In other cases, the antibiotics could interfere with mitochondrial functions even if their main bacterial targets are not shared with the eukaryotic cells. The purpose of this review is to summarize the effects of antibiotics administration on mitochondrial homeostasis and the opportunity that some of these molecules could represent in cancer treatment. The importance of antimicrobial therapy is unquestionable, but the identification of interaction with eukaryotic cells and in particular with mitochondria is crucial to reduce the toxicity of these drugs and to explore other useful medical applications.

Keywords:  Antibiotic side effects; Antibiotics; Mitochondria; Mitochondrial perturbation

DOI:  https://doi.org/10.1016/bs.ircmb.2023.03.009