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Signal Transduction and Targeted Therapy Aug 2023As key organelles involved in cellular metabolism, mitochondria frequently undergo adaptive changes in morphology, components and functions in response to various... (Review)
Review
As key organelles involved in cellular metabolism, mitochondria frequently undergo adaptive changes in morphology, components and functions in response to various environmental stresses and cellular demands. Previous studies of mitochondria research have gradually evolved, from focusing on morphological change analysis to systematic multiomics, thereby revealing the mitochondrial variation between cells or within the mitochondrial population within a single cell. The phenomenon of mitochondrial variation features is defined as mitochondrial heterogeneity. Moreover, mitochondrial heterogeneity has been reported to influence a variety of physiological processes, including tissue homeostasis, tissue repair, immunoregulation, and tumor progression. Here, we comprehensively review the mitochondrial heterogeneity in different tissues under pathological states, involving variant features of mitochondrial DNA, RNA, protein and lipid components. Then, the mechanisms that contribute to mitochondrial heterogeneity are also summarized, such as the mutation of the mitochondrial genome and the import of mitochondrial proteins that result in the heterogeneity of mitochondrial DNA and protein components. Additionally, multiple perspectives are investigated to better comprehend the mysteries of mitochondrial heterogeneity between cells. Finally, we summarize the prospective mitochondrial heterogeneity-targeting therapies in terms of alleviating mitochondrial oxidative damage, reducing mitochondrial carbon stress and enhancing mitochondrial biogenesis to relieve various pathological conditions. The possibility of recent technological advances in targeted mitochondrial gene editing is also discussed.
Topics: Prospective Studies; Mitochondria; DNA, Mitochondrial; Gene Editing; Mitochondrial Proteins
PubMed: 37607925
DOI: 10.1038/s41392-023-01546-w -
Journal of Advanced Research Jan 2024Liver fibrosis is a life-threatening pathological anomaly which usually evolves into advanced liver cirrhosis and hepatocellular carcinoma although limited therapeutic...
INTRODUCTION
Liver fibrosis is a life-threatening pathological anomaly which usually evolves into advanced liver cirrhosis and hepatocellular carcinoma although limited therapeutic option is readily available. FUN14 domain containing 1 (FUNDC1) is a mitophagy receptor with little information in liver fibrosis.
OBJECTIVE
This study was designed to examine the role for FUNDC1 in carbon tetrachloride (CCl4)-induced liver injury.
METHODS
GEO database analysis and subsequent validation of biological processes including western blot, immunofluorescence, and co-immunoprecipitation were applied to clarify the regulatory role of FUNDC1 on mitophagy and ferroptosis.
RESULTS
Our data revealed elevated FUNDC1 levels in liver tissues of patients with liver fibrotic injury and CCl4-challenged mice. FUNDC1 deletion protected against CCl4-induced hepatic anomalies in mice. Moreover, FUNDC1 deletion ameliorated CCl4-induced ferroptosis in vivo and in vitro. Mechanically, FUNDC1 interacted with glutathione peroxidase (GPx4), a selenoenzyme to neutralize lipid hydroperoxides and ferroptosis, via its 96-133 amino acid domain to facilitate GPx4 recruitment into mitochondria from cytoplasm. GPx4 entered mitochondria through mitochondrial protein import system-the translocase of outer membrane/translocase of inner membrane (TOM/TIM) complex, prior to degradation of GPx4 mainly through mitophagy along with ROS-induced damaged mitochondria, resulting in hepatocyte ferroptosis.
CONCLUSION
Taken together, our data favored that FUNDC1 promoted hepatocyte injury through GPx4 binding to facilitate its mitochondrial translocation through TOM/TIM complex, where GPx4 was degraded by mitophagy to trigger ferroptosis. Targeting FUNDC1 may be a promising therapeutic approach for liver fibrosis.
Topics: Humans; Mice; Animals; Mitophagy; Glutathione Peroxidase; Ferroptosis; Liver Cirrhosis; Liver Neoplasms; Membrane Proteins; Mitochondrial Proteins
PubMed: 36828120
DOI: 10.1016/j.jare.2023.02.012 -
Science (New York, N.Y.) Nov 2023Mitochondria must maintain adequate amounts of metabolites for protective and biosynthetic functions. However, how mitochondria sense the abundance of metabolites and...
Mitochondria must maintain adequate amounts of metabolites for protective and biosynthetic functions. However, how mitochondria sense the abundance of metabolites and regulate metabolic homeostasis is not well understood. In this work, we focused on glutathione (GSH), a critical redox metabolite in mitochondria, and identified a feedback mechanism that controls its abundance through the mitochondrial GSH transporter, SLC25A39. Under physiological conditions, SLC25A39 is rapidly degraded by mitochondrial protease AFG3L2. Depletion of GSH dissociates AFG3L2 from SLC25A39, causing a compensatory increase in mitochondrial GSH uptake. Genetic and proteomic analyses identified a putative iron-sulfur cluster in the matrix-facing loop of SLC25A39 as essential for this regulation, coupling mitochondrial iron homeostasis to GSH import. Altogether, our work revealed a paradigm for the autoregulatory control of metabolic homeostasis in organelles.
Topics: Glutathione; Homeostasis; Iron; Mitochondria; Mitochondrial Membrane Transport Proteins; Proteomics; Feedback, Physiological; Mitochondrial Proteins; Phosphate Transport Proteins; Humans; Iron-Sulfur Proteins; Proteolysis; HEK293 Cells; ATP-Dependent Proteases; ATPases Associated with Diverse Cellular Activities
PubMed: 37917749
DOI: 10.1126/science.adf4154 -
The EMBO Journal Jul 2023Chloroplasts are plant organelles responsible for photosynthesis and environmental sensing. Most chloroplast proteins are imported from the cytosol through the...
Chloroplasts are plant organelles responsible for photosynthesis and environmental sensing. Most chloroplast proteins are imported from the cytosol through the translocon at the outer envelope membrane of chloroplasts (TOC). Previous work has shown that TOC components are regulated by the ubiquitin-proteasome system (UPS) to control the chloroplast proteome, which is crucial for the organelle's function and plant development. Here, we demonstrate that the TOC apparatus is also subject to K63-linked polyubiquitination and regulation by selective autophagy, potentially promoting plant stress tolerance. We identify NBR1 as a selective autophagy adaptor targeting TOC components, and mediating their relocation into vacuoles for autophagic degradation. Such selective autophagy is shown to control TOC protein levels and chloroplast protein import and to influence photosynthetic activity as well as tolerance to UV-B irradiation and heat stress in Arabidopsis plants. These findings uncover the vital role of selective autophagy in the proteolytic regulation of specific chloroplast proteins, and how dynamic control of chloroplast protein import is critically important for plants to cope with challenging environments.
Topics: Chloroplasts; Plants; Organelles; Protein Transport; Chloroplast Proteins; Arabidopsis; Autophagy; Plant Proteins; Arabidopsis Proteins; Carrier Proteins
PubMed: 37248861
DOI: 10.15252/embj.2022112534 -
Nature Genetics Oct 2023Uniparental inheritance of mitochondrial DNA (mtDNA) is an evolutionary trait found in nearly all eukaryotes. In many species, including humans, the sperm mitochondria...
Uniparental inheritance of mitochondrial DNA (mtDNA) is an evolutionary trait found in nearly all eukaryotes. In many species, including humans, the sperm mitochondria are introduced to the oocyte during fertilization. The mechanisms hypothesized to prevent paternal mtDNA transmission include ubiquitination of the sperm mitochondria and mitophagy. However, the causative mechanisms of paternal mtDNA elimination have not been defined. We found that mitochondria in human spermatozoa are devoid of intact mtDNA and lack mitochondrial transcription factor A (TFAM)-the major nucleoid protein required to protect, maintain and transcribe mtDNA. During spermatogenesis, sperm cells express an isoform of TFAM, which retains the mitochondrial presequence, ordinarily removed upon mitochondrial import. Phosphorylation of this presequence prevents mitochondrial import and directs TFAM to the spermatozoon nucleus. TFAM relocalization from the mitochondria of spermatogonia to the spermatozoa nucleus directly correlates with the elimination of mtDNA, thereby explaining maternal inheritance in this species.
Topics: Humans; Male; DNA, Mitochondrial; Maternal Inheritance; Semen; Mitochondria; Spermatozoa; Mitochondrial Proteins
PubMed: 37723262
DOI: 10.1038/s41588-023-01505-9 -
Nature Feb 2024Stress response pathways detect and alleviate adverse conditions to safeguard cell and tissue homeostasis, yet their prolonged activation induces apoptosis and disrupts...
Stress response pathways detect and alleviate adverse conditions to safeguard cell and tissue homeostasis, yet their prolonged activation induces apoptosis and disrupts organismal health. How stress responses are turned off at the right time and place remains poorly understood. Here we report a ubiquitin-dependent mechanism that silences the cellular response to mitochondrial protein import stress. Crucial to this process is the silencing factor of the integrated stress response (SIFI), a large E3 ligase complex mutated in ataxia and in early-onset dementia that degrades both unimported mitochondrial precursors and stress response components. By recognizing bifunctional substrate motifs that equally encode protein localization and stability, the SIFI complex turns off a general stress response after a specific stress event has been resolved. Pharmacological stress response silencing sustains cell survival even if stress resolution failed, which underscores the importance of signal termination and provides a roadmap for treating neurodegenerative diseases caused by mitochondrial import defects.
Topics: Apoptosis; Ataxia; Cell Survival; Dementia; Mitochondria; Mitochondrial Proteins; Multiprotein Complexes; Mutation; Neurodegenerative Diseases; Protein Stability; Protein Transport; Proteolysis; Stress, Physiological; Ubiquitin; Ubiquitin-Protein Ligases; Ubiquitination
PubMed: 38297121
DOI: 10.1038/s41586-023-06985-7 -
Nature Sep 2023Mitochondria import nearly all of their approximately 1,000-2,000 constituent proteins from the cytosol across their double-membrane envelope. Genetic and biochemical...
Mitochondria import nearly all of their approximately 1,000-2,000 constituent proteins from the cytosol across their double-membrane envelope. Genetic and biochemical studies have shown that the conserved protein translocase, termed the TIM23 complex, mediates import of presequence-containing proteins (preproteins) into the mitochondrial matrix and inner membrane. Among about ten different subunits of the TIM23 complex, the essential multipass membrane protein Tim23, together with the evolutionarily related protein Tim17, has long been postulated to form a protein-conducting channel. However, the mechanism by which these subunits form a translocation path in the membrane and enable the import process remains unclear due to a lack of structural information. Here we determined the cryo-electron microscopy structure of the core TIM23 complex (heterotrimeric Tim17-Tim23-Tim44) from Saccharomyces cerevisiae. Contrary to the prevailing model, Tim23 and Tim17 themselves do not form a water-filled channel, but instead have separate, lipid-exposed concave cavities that face in opposite directions. Our structural and biochemical analyses show that the cavity of Tim17, but not Tim23, forms the protein translocation path, whereas Tim23 probably has a structural role. The results further suggest that, during translocation of substrate polypeptides, the nonessential subunit Mgr2 seals the lateral opening of the Tim17 cavity to facilitate the translocation process. We propose a new model for the TIM23-mediated protein import and sorting mechanism, a central pathway in mitochondrial biogenesis.
Topics: Cryoelectron Microscopy; Mitochondrial Precursor Protein Import Complex Proteins; Protein Transport; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Mitochondria
PubMed: 37344598
DOI: 10.1038/s41586-023-06239-6 -
Molecular Cell Oct 2023Mitochondrial DNA double-strand breaks (mtDSBs) lead to the degradation of circular genomes and a reduction in copy number; yet, the cellular response in human cells...
Mitochondrial DNA double-strand breaks (mtDSBs) lead to the degradation of circular genomes and a reduction in copy number; yet, the cellular response in human cells remains elusive. Here, using mitochondrial-targeted restriction enzymes, we show that a subset of cells with mtDSBs exhibited defective mitochondrial protein import, reduced respiratory complexes, and loss of membrane potential. Electron microscopy confirmed the altered mitochondrial membrane and cristae ultrastructure. Intriguingly, mtDSBs triggered the integrated stress response (ISR) via the phosphorylation of eukaryotic translation initiation factor 2α (eIF2α) by DELE1 and heme-regulated eIF2α kinase (HRI). When ISR was inhibited, the cells experienced intensified mitochondrial defects and slower mtDNA recovery post-breakage. Lastly, through proteomics, we identified ATAD3A-a membrane-bound protein interacting with nucleoids-as potentially pivotal in relaying signals from impaired genomes to the inner mitochondrial membrane. In summary, our study delineates the cascade connecting damaged mitochondrial genomes to the cytoplasm and highlights the significance of the ISR in maintaining mitochondrial homeostasis amid genome instability.
Topics: Humans; Mitochondria; eIF-2 Kinase; Cytoplasm; Phosphorylation; DNA, Mitochondrial; Eukaryotic Initiation Factor-2; ATPases Associated with Diverse Cellular Activities; Membrane Proteins; Mitochondrial Proteins
PubMed: 37832546
DOI: 10.1016/j.molcel.2023.09.026 -
Nature Communications Sep 2023Microglia, the innate immune cells of the central nervous system, actively participate in brain development by supporting neuronal maturation and refining synaptic...
Microglia, the innate immune cells of the central nervous system, actively participate in brain development by supporting neuronal maturation and refining synaptic connections. These cells are emerging as highly metabolically flexible, able to oxidize different energetic substrates to meet their energy demand. Lactate is particularly abundant in the brain, but whether microglia use it as a metabolic fuel has been poorly explored. Here we show that microglia can import lactate, and this is coupled with increased lysosomal acidification. In vitro, loss of the monocarboxylate transporter MCT4 in microglia prevents lactate-induced lysosomal modulation and leads to defective cargo degradation. Microglial depletion of MCT4 in vivo leads to impaired synaptic pruning, associated with increased excitation in hippocampal neurons, enhanced AMPA/GABA ratio, vulnerability to seizures and anxiety-like phenotype. Overall, these findings show that selective disruption of the MCT4 transporter in microglia is sufficient to alter synapse refinement and to induce defects in mouse brain development and adult behavior.
Topics: Animals; Mice; Microglia; Anxiety; Central Nervous System; Lactic Acid; Membrane Transport Proteins; Neuronal Plasticity
PubMed: 37717033
DOI: 10.1038/s41467-023-41502-4 -
Nature Aug 2023To replicate inside macrophages and cause tuberculosis, Mycobacterium tuberculosis must scavenge a variety of nutrients from the host. The mammalian cell entry (MCE)...
To replicate inside macrophages and cause tuberculosis, Mycobacterium tuberculosis must scavenge a variety of nutrients from the host. The mammalian cell entry (MCE) proteins are important virulence factors in M. tuberculosis, where they are encoded by large gene clusters and have been implicated in the transport of fatty acids and cholesterol across the impermeable mycobacterial cell envelope. Very little is known about how cargos are transported across this barrier, and it remains unclear how the approximately ten proteins encoded by a mycobacterial mce gene cluster assemble to transport cargo across the cell envelope. Here we report the cryo-electron microscopy (cryo-EM) structure of the endogenous Mce1 lipid-import machine of Mycobacterium smegmatis-a non-pathogenic relative of M. tuberculosis. The structure reveals how the proteins of the Mce1 system assemble to form an elongated ABC transporter complex that is long enough to span the cell envelope. The Mce1 complex is dominated by a curved, needle-like domain that appears to be unrelated to previously described protein structures, and creates a protected hydrophobic pathway for lipid transport across the periplasm. Our structural data revealed the presence of a subunit of the Mce1 complex, which we identified using a combination of cryo-EM and AlphaFold2, and name LucB. Our data lead to a structural model for Mce1-mediated lipid import across the mycobacterial cell envelope.
Topics: Animals; Bacterial Proteins; Cryoelectron Microscopy; Lipids; Membrane Transport Proteins; Mycobacterium tuberculosis; Tuberculosis; Virus Internalization; Virulence Factors; ATP-Binding Cassette Transporters; Periplasm; Protein Domains; Hydrophobic and Hydrophilic Interactions; Multiprotein Complexes
PubMed: 37495693
DOI: 10.1038/s41586-023-06366-0