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Journal of Extracellular Vesicles Dec 2023Macrophages play major roles in the pathophysiology of various neurological disorders, being involved in seemingly opposing processes such as lesion progression and...
Macrophages play major roles in the pathophysiology of various neurological disorders, being involved in seemingly opposing processes such as lesion progression and resolution. Yet, the molecular mechanisms that drive their harmful and benign effector functions remain poorly understood. Here, we demonstrate that extracellular vesicles (EVs) secreted by repair-associated macrophages (RAMs) enhance remyelination ex vivo and in vivo by promoting the differentiation of oligodendrocyte precursor cells (OPCs). Guided by lipidomic analysis and applying cholesterol depletion and enrichment strategies, we find that EVs released by RAMs show markedly elevated cholesterol levels and that cholesterol abundance controls their reparative impact on OPC maturation and remyelination. Mechanistically, EV-associated cholesterol was found to promote OPC differentiation predominantly through direct membrane fusion. Collectively, our findings highlight that EVs are essential for cholesterol trafficking in the brain and that changes in cholesterol abundance support the reparative impact of EVs released by macrophages in the brain, potentially having broad implications for therapeutic strategies aimed at promoting repair in neurodegenerative disorders.
Topics: Extracellular Vesicles; Brain; Macrophages; Cell Differentiation; Cholesterol
PubMed: 38124258
DOI: 10.1002/jev2.12394 -
Autophagy Mar 2024Macroautophagy/autophagy is a highly conserved process that involves the degradation of proteins, damaged organelles, and other cytoplasmic macromolecules....
Macroautophagy/autophagy is a highly conserved process that involves the degradation of proteins, damaged organelles, and other cytoplasmic macromolecules. Autophagosome-lysosome fusion is critical for successful substrate degradation and is mediated by SNARE proteins. The fusion process requires additional vesicle docking and tethering-regulating factors. Our recent work has uncovered a functional model of autophagosome-lysosome fusion. We demonstrated that the six-subunit homotypic fusion and vacuole protein sorting (HOPS) complex can be assembled by two subcomplexes, the VPS39-VPS11 subcomplex (HOPS-2) and the VPS41-VPS16-VPS18-VPS33A subcomplex (HOPS-4). VPS39 binds with RAB2 on the autophagosome and VPS41 binds with RAB39A on the lysosome, which then promotes membrane tethering and autophagic SNARE-mediated membrane fusion. Moreover, we have revealed that ALS- and FTD-related C9orf72 is a guanine exchange factor (GEF) for RAB39A. In this punctum, we discuss how the C9orf72-RAB39A-HOPS axis function regulates autophagosome-lysosome fusion.
Topics: Macroautophagy; C9orf72 Protein; Autophagy; Autophagosomes; Membrane Fusion; SNARE Proteins; Lysosomes
PubMed: 38083843
DOI: 10.1080/15548627.2023.2291938 -
Cell Jun 2024Mitochondrial dynamics play a critical role in cell fate decisions and in controlling mtDNA levels and distribution. However, the molecular mechanisms linking...
Mitochondrial dynamics play a critical role in cell fate decisions and in controlling mtDNA levels and distribution. However, the molecular mechanisms linking mitochondrial membrane remodeling and quality control to mtDNA copy number (CN) regulation remain elusive. Here, we demonstrate that the inner mitochondrial membrane (IMM) protein mitochondrial fission process 1 (MTFP1) negatively regulates IMM fusion. Moreover, manipulation of mitochondrial fusion through the regulation of MTFP1 levels results in mtDNA CN modulation. Mechanistically, we found that MTFP1 inhibits mitochondrial fusion to isolate and exclude damaged IMM subdomains from the rest of the network. Subsequently, peripheral fission ensures their segregation into small MTFP1-enriched mitochondria (SMEM) that are targeted for degradation in an autophagic-dependent manner. Remarkably, MTFP1-dependent IMM quality control is essential for basal nucleoid recycling and therefore to maintain adequate mtDNA levels within the cell.
PubMed: 38851188
DOI: 10.1016/j.cell.2024.05.017 -
International Journal of Molecular... Apr 2024In response to cellular metabolic and signaling cues, the mitochondrial network employs distinct sets of membrane-shaping factors to dynamically modulate organellar... (Review)
Review
In response to cellular metabolic and signaling cues, the mitochondrial network employs distinct sets of membrane-shaping factors to dynamically modulate organellar structures through a balance of fission and fusion. While these organellar dynamics mediate mitochondrial structure/function homeostasis, they also directly impact critical cell-wide signaling pathways such as apoptosis, autophagy, and the integrated stress response (ISR). Mitochondrial fission is driven by the recruitment of the cytosolic dynamin-related protein-1 (DRP1), while fusion is carried out by mitofusins 1 and 2 (in the outer membrane) and optic atrophy-1 (OPA1) in the inner membrane. This dynamic balance is highly sensitive to cellular stress; when the transmembrane potential across the inner membrane (Δψ) is lost, fusion-active OPA1 is cleaved by the overlapping activity with m-AAA protease-1 (OMA1 metalloprotease, disrupting mitochondrial fusion and leaving dynamin-related protein-1 (DRP1)-mediated fission unopposed, thus causing the collapse of the mitochondrial network to a fragmented state. OMA1 is a unique regulator of stress-sensitive homeostatic mitochondrial balance, acting as a key upstream sensor capable of priming the cell for apoptosis, autophagy, or ISR signaling cascades. Recent evidence indicates that higher-order macromolecular associations within the mitochondrial inner membrane allow these specialized domains to mediate crucial organellar functionalities.
Topics: Mitochondrial Dynamics; Humans; Homeostasis; Animals; Mitochondria; Stress, Physiological; Mitochondrial Proteins; Metalloendopeptidases; Signal Transduction; Autophagy; Dynamins; Apoptosis; GTP Phosphohydrolases
PubMed: 38674151
DOI: 10.3390/ijms25084566 -
PLoS Pathogens Dec 2023Interaction between the Ebola virus envelope glycoprotein (GP) and the endosomal membrane is an essential step during virus entry into the cell. Acidic pH and Ca2+ have...
Interaction between the Ebola virus envelope glycoprotein (GP) and the endosomal membrane is an essential step during virus entry into the cell. Acidic pH and Ca2+ have been implicated in mediating the GP-membrane interaction. However, the molecular mechanism by which these environmental factors regulate the conformational changes that enable engagement of GP with the target membrane is unknown. Here, we apply fluorescence correlation spectroscopy (FCS) and single-molecule Förster resonance energy transfer (smFRET) imaging to elucidate how the acidic pH, Ca2+ and anionic phospholipids in the late endosome promote GP-membrane interaction, thereby facilitating virus entry. We find that bis(monoacylglycero)phosphate (BMP), which is specific to the late endosome, is especially critical in determining the Ca2+-dependence of the GP-membrane interaction. Molecular dynamics (MD) simulations suggested residues in GP that sense pH and induce conformational changes that make the fusion loop available for insertion into the membrane. We similarly confirm residues in the fusion loop that mediate GP's interaction with Ca2+, which likely promotes local conformational changes in the fusion loop and mediates electrostatic interactions with the anionic phospholipids. Collectively, our results provide a mechanistic understanding of how the environment of the late endosome regulates the timing and efficiency of virus entry.
Topics: Humans; Hemorrhagic Fever, Ebola; Ebolavirus; Calcium; Viral Envelope Proteins; Endosomes; Protein Conformation; Virus Internalization; Membrane Fusion; Hydrogen-Ion Concentration
PubMed: 38055723
DOI: 10.1371/journal.ppat.1011848 -
The Journal of Cell Biology Nov 2023Exocrine cells utilize large secretory vesicles (LSVs) up to 10 μm in diameter. LSVs fuse with the apical surface, often recruiting actomyosin to extrude their content...
Exocrine cells utilize large secretory vesicles (LSVs) up to 10 μm in diameter. LSVs fuse with the apical surface, often recruiting actomyosin to extrude their content through dynamic fusion pores. The molecular mechanism regulating pore dynamics remains largely uncharacterized. We observe that the fusion pores of LSVs in the Drosophila larval salivary glands expand, stabilize, and constrict. Arp2/3 is essential for pore expansion and stabilization, while myosin II is essential for pore constriction. We identify several Bin-Amphiphysin-Rvs (BAR) homology domain proteins that regulate fusion pore expansion and stabilization. We show that the I-BAR protein Missing-in-Metastasis (MIM) localizes to the fusion site and is essential for pore expansion and stabilization. The MIM I-BAR domain is essential but not sufficient for localization and function. We conclude that MIM acts in concert with actin, myosin II, and additional BAR-domain proteins to control fusion pore dynamics, mediating a distinct mode of exocytosis, which facilitates actomyosin-dependent content release that maintains apical membrane homeostasis during secretion.
Topics: Animals; Actin Cytoskeleton; Actomyosin; Cell Membrane; Cytoskeletal Proteins; Drosophila; Exocytosis; Secretory Vesicles
PubMed: 37707500
DOI: 10.1083/jcb.202302112 -
Nanoscale May 2024Membrane fusion is crucial for infection of enveloped viruses, cellular transport, and drug delivery liposomes. Nanoparticles can serve as fusogenic agents facilitating...
Membrane fusion is crucial for infection of enveloped viruses, cellular transport, and drug delivery liposomes. Nanoparticles can serve as fusogenic agents facilitating such membrane fusion for direct transmembrane transport. However, the underlying mechanisms of nanoparticle-induced fusion and the ideal properties of such nanoparticles remain largely unknown. Here, we used molecular dynamics simulations to investigate the efficacy of spheroidal nanoparticles with different size, prolateness, and ligand interaction strengths to enhance fusion between vesicles. By systematically varying nanoparticle properties, we identified how each parameter affects the fusion process and determined the optimal parameter range that promotes fusion. These findings provide valuable insights for the design and optimization of fusogenic nanoparticles with potential biotechnological and biomedical applications.
Topics: Nanoparticles; Molecular Dynamics Simulation; Membrane Fusion; Liposomes; Lipid Bilayers; Membrane Lipids
PubMed: 38679949
DOI: 10.1039/d4nr00591k -
Autophagy Feb 2024Macroautophagy/autophagy is an essential pro-survival mechanism activated in response to nutrient deficiency. The proper fusion between autophagosomes and lysosomes is a...
Macroautophagy/autophagy is an essential pro-survival mechanism activated in response to nutrient deficiency. The proper fusion between autophagosomes and lysosomes is a critical step for autophagic degradation. We recently reported that RUNDC1 (RUN domain containing 1) inhibits autolysosome formation via clasping the ATG14-STX17-SNAP29 complex to hinder VAMP8 binding. We showed that RUNDC1 colocalizes with LC3 and associates with mature autophagosomes in cell lines and the zebrafish model. We utilized liposome fusion and autophagosome-lysosome fusion assays to demonstrate that RUNDC1 inhibits autolysosome formation. Moreover, we found that RUNDC1 clasps the ATG14-STX17-SNAP29 complex via stimulating ATG14 homo-oligomerization to inhibit ATG14 dissociation, which in turn prevents VAMP8 from binding to STX17-SNAP29. Our results demonstrate that RUNDC1 is a negative regulator of autophagy that restricts autophagosome fusion with lysosomes and is crucial for zebrafish survival in nutrient-deficient conditions. Here, we summarize our findings and discuss their implications for our understanding of autophagy regulation.
Topics: Animals; Autophagosomes; Autophagy; Zebrafish; Transcription Factors; Lysosomes; Membrane Fusion; SNARE Proteins
PubMed: 37876308
DOI: 10.1080/15548627.2023.2274210 -
Nature Nanotechnology Dec 2023Dynamic therapies have potential in cancer treatments but have limitations in efficiency and penetration depth. Here a membrane-integrated liposome (MIL) is created to...
Dynamic therapies have potential in cancer treatments but have limitations in efficiency and penetration depth. Here a membrane-integrated liposome (MIL) is created to coat titanium dioxide (TiO) nanoparticles to enhance electron transfer and increase radical production under low-dose X-ray irradiation. The exoelectrogenic Shewanella oneidensis MR-1 microorganism presents an innate capability for extracellular electron transfer (EET). An EET-mimicking photocatalytic system is created by coating the TiO nanoparticles with the MIL, which significantly enhances superoxide anions generation under low-dose (1 Gy) X-ray activation. The c-type cytochromes-constructed electron channel in the membrane mimics electron transfer to surrounding oxygen. Moreover, the hole transport in the valence band is also observed for water oxidation to produce hydroxyl radicals. The TiO@MIL system is demonstrated against orthotopic liver tumours in vivo.
Topics: Liposomes; Electrons; Membrane Fusion; Electron Transport; Oxidation-Reduction; Shewanella
PubMed: 37537274
DOI: 10.1038/s41565-023-01476-2 -
Phytomedicine : International Journal... Nov 2023Given the magnitude of influenza pandemics as a threat to the global population, it is crucial to have as many prevention and treatment options as possible. Piceatannol...
BACKGROUND
Given the magnitude of influenza pandemics as a threat to the global population, it is crucial to have as many prevention and treatment options as possible. Piceatannol (PIC) is a tetrahydroxylated stilbenoid (trans-3,4,3',5'-tetrahydroxystilbene), also known as 3'- hydroxy resveratrol, which has demonstrated many different biological activities such as anti-inflammatory and antiviral activities.
PURPOSE
In this study, the anti-influenza A virus (IAV) activities and mechanisms of PIC in vitro and in vivo were investigated in order to provide reference for the development of novel plant-derived anti-IAV drugs.
METHODS
The viral plaque assay, RT-PCR and western blot assay were used to evaluate the anti-IAV effects of PIC in vitro. The anti-IAV mechanism of PIC was determined by HA syncytium assay, DARTS assay and Surface Plasmon Resonance assay. The mouse pneumonia model combined with HE staining were used to study the anti-IAV effects of PIC in vivo.
RESULTS
PIC shows inhibition on the multiplication of both H1N1 and H3N2 viruses, and blocks the infection of H5N1 pseudovirus with low toxicity. PIC may directly act on the envelope of IAV to induce the rupture and inactivation of IAV particles. PIC can also block membrane fusion via binding to HA2 rather than HA1 and cleavage site of HA0. PIC may interact with the two residues (HA2-T68 and HA2-I75) of HA2 to block the conformational change of HA so as to inhibit membrane fusion. Importantly, oral therapy of PIC also markedly improved survival and reduced viral titers in IAV-infected mice.
CONCLUSION
PIC possesses significant anti-IAV effects both in vitro and in vivo and may block IAV infection mainly through interaction with HA to block membrane fusion. Thus, PIC has the potential to be developed into a new broad-spectrum anti-influenza drug for the prevention and treatment of influenza.
Topics: Animals; Mice; Humans; Influenza A Virus, H3N2 Subtype; Hemagglutinins; Influenza A Virus, H1N1 Subtype; Influenza A Virus, H5N1 Subtype; Influenza A virus; Influenza, Human; Stilbenes; Disease Models, Animal
PubMed: 37690231
DOI: 10.1016/j.phymed.2023.155058