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MSphere Dec 2023A microbe and its host are in constant communication. An emerging platform for direct communication is the membrane contact sites that form between several pathogens and... (Review)
Review
A microbe and its host are in constant communication. An emerging platform for direct communication is the membrane contact sites that form between several pathogens and host organelles. Here, we review our progress on the molecular mechanisms underlying contact sites between host mitochondria and the human parasite . We discuss open questions regarding their function during infection as well as those formed between the host endoplasmic reticulum and .
Topics: Humans; Vacuoles; Endoplasmic Reticulum; Toxoplasma; Mitochondrial Membranes
PubMed: 37850752
DOI: 10.1128/msphere.00448-23 -
Renal Failure Dec 2023Human umbilical cord mesenchymal stem cells (hucMSCs) have been shown to improve kidney injury. Exosomes have been indicated to be important mediators of renal...
Human umbilical cord mesenchymal stem cells (hucMSCs) have been shown to improve kidney injury. Exosomes have been indicated to be important mediators of renal protection in MSC therapy. In spite of this, the mechanism remains unclear. Our study investigated how exosomes derived from hucMSCs (hucMSC-Ex) improve acute kidney injury (AKI). Exosomes were extracted by using an ultracentrifugation technique and identified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blot. Twenty-four male SD rats were randomly divided into four groups: sham group, sham + hucMSC-Ex group, ischemia-reperfusion injury (IRI) group, and IRI + hucMSC-Ex group. , we treated rat proximal renal tubular epithelial cell line (NRK-52E) with cisplatin to mimic models of AKI. The NRK-52E cells were treated with or without 160 μg/mL hucMSC-Ex, and 1 µg/mL cisplatin was added after 9 h. Cells were harvested after 24 h. In the IRI group, the levels of serum creatinine (Scr) and blood urea nitrogen (BUN) were increased; renal tubules were dilated, epithelial cells were vacuolated, and collagen fibers were deposited in the renal interstitium. After treatment with cisplatin, the NRK-52E cells displayed pyroptotic morphology characterized by pyroptotic bodies. The protein expression levels of fibronectin, α-smooth muscle actin (α-SMA), vimentin, gasdermin D (GSDMD), caspase-1, interleukin-1 (IL-1β) and NLRP3 in IRI tissues and in cisplatin treatment NRK-52E cells were significantly upregulated. However, after the hucMSC-Ex intervention, kidney injury was effectively improved and . The current study shows that pyroptosis is involved in AKI and that hucMSC-Ex improves AKI by inhibiting pyroptosis.
Topics: Rats; Humans; Male; Animals; Exosomes; Pyroptosis; Rats, Sprague-Dawley; Cisplatin; Acute Kidney Injury; Umbilical Cord; Mesenchymal Stem Cells
PubMed: 37293812
DOI: 10.1080/0886022X.2023.2221138 -
BioRxiv : the Preprint Server For... Jul 2023serovar Typhimurium is a facultative intracellular pathogen that utilizes its type III secretion systems (T3SSs) to inject virulence factors into the host cell and...
serovar Typhimurium is a facultative intracellular pathogen that utilizes its type III secretion systems (T3SSs) to inject virulence factors into the host cell and colonize the host. In turn, a subset of cytosolic immune receptors respond to T3SS ligands by forming multimeric signaling complexes called inflammasomes, which activate caspases that induce interleukin-1 (IL-1) family cytokine release and an inflammatory form of cell death called pyroptosis. Human macrophages mount a multifaceted inflammasome response to infection that ultimately restricts intracellular bacterial replication. However, how inflammasomes restrict replication remains unknown. We find that caspase-1 is essential for mediating inflammasome responses to and subsequent restriction of bacterial replication within human macrophages, with caspase-4 contributing as well. We also demonstrate that the downstream pore-forming protein gasdermin D (GSDMD) and ninjurin-1 (NINJ1), a mediator of terminal cell lysis, play a role in controlling replication in human macrophages. Notably, in the absence of inflammasome responses, we observed hyperreplication of within the cytosol of infected cells, and we also observed increased bacterial replication within vacuoles, suggesting that inflammasomes control replication primarily within the cytosol and also within vacuoles. These findings reveal that inflammatory caspases and pyroptotic factors mediate inflammasome responses that restrict the subcellular localization of intracellular replication within human macrophages.
PubMed: 37503120
DOI: 10.1101/2023.07.17.549348 -
The Journal of Cell Biology Jun 2024Organelles of the endomembrane system contain Rab GTPases as identity markers. Their localization is determined by guanine nucleotide exchange factors (GEFs) and GTPase...
Organelles of the endomembrane system contain Rab GTPases as identity markers. Their localization is determined by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). It remains largely unclear how these regulators are specifically targeted to organelles and how their activity is regulated. Here, we focus on the GAP Gyp7, which acts on the Rab7-like Ypt7 protein in yeast, and surprisingly observe the protein exclusively in puncta proximal to the vacuole. Mistargeting of Gyp7 to the vacuole strongly affects vacuole morphology, suggesting that endosomal localization is needed for function. In agreement, efficient endolysosomal transport requires Gyp7. In vitro assays reveal that Gyp7 requires a distinct lipid environment for membrane binding and activity. Overexpression of Gyp7 concentrates Ypt7 in late endosomes and results in resistance to rapamycin, an inhibitor of the target of rapamycin complex 1 (TORC1), suggesting that these late endosomes are signaling endosomes. We postulate that Gyp7 is part of regulatory machinery involved in late endosome function.
Topics: Biological Transport; Endosomes; Saccharomyces cerevisiae; Signal Transduction; Vacuoles; ras GTPase-Activating Proteins; rab GTP-Binding Proteins; Saccharomyces cerevisiae Proteins
PubMed: 38536036
DOI: 10.1083/jcb.202305038 -
Parasites & Vectors Apr 2024To successfully replicate within the host cell, Toxoplasma gondii employs several mechanisms to overcome the host cell defenses and mitigate the harmful effects of the...
BACKGROUND
To successfully replicate within the host cell, Toxoplasma gondii employs several mechanisms to overcome the host cell defenses and mitigate the harmful effects of the free radicals resulting from its own metabolic processes using effectors such as thioredoxin proteins. In this study, we characterize the location and functions of a newly identified thioredoxin in T. gondii, which was named Trx4.
METHODS
We characterized the functional role of Trx4 in T. gondii Type I RH and Type II Pru strains by gene knockout and studied its subcellular localization by endogenous protein HA tagging using CRISPR-Cas9 gene editing. The enzyme-catalyzed proximity labeling technique, the TurboID system, was employed to identify the proteins in proximity to Trx4.
RESULTS
Trx4 was identified as a dense granule protein of T. gondii predominantly expressed in the parasitophorous vacuole (PV) and was partially co-localized with GRA1 and GRA5. Functional analysis showed that deletion of trx4 markedly influenced the parasite lytic cycle, resulting in impaired host cell invasion capacity in both RH and Pru strains. Mutation of Trx domains in Trx4 in RH strain revealed that two Trx domains were important for the parasite invasion. By utilizing the TurboID system to biotinylate proteins in proximity to Trx4, we identified a substantial number of proteins, some of which are novel, and others are previously characterized, predominantly distributed in the dense granules. In addition, we uncovered three novel proteins co-localized with Trx4. Intriguingly, deletion of trx4 did not affect the localization of these three proteins. Finally, a virulence assay demonstrated that knockout of trx4 resulted in a significant attenuation of virulence and a significant reduction in brain cyst loads in mice.
CONCLUSIONS
Trx4 plays an important role in T. gondii invasion and virulence in Type I RH strain and Type II Pru strain. Combining the TurboID system with CRISPR-Cas9 technique revealed many PV-localized proximity proteins associated with Trx4. These findings suggest a versatile role of Trx4 in mediating the processes that occur in this distinctive intracellular membrane-bound vacuolar compartment.
Topics: Animals; Mice; Toxoplasma; Protozoan Proteins; Antigens, Protozoan; Virulence; Immunologic Factors; Thioredoxins
PubMed: 38576040
DOI: 10.1186/s13071-024-06259-9 -
BMC Rheumatology Jul 2023VEXAS is a recently described inflammatory disease caused by mutations in the UBA1 gene. Symptoms are diverse and include fevers, cartilaginous inflammation, lung...
BACKGROUND
VEXAS is a recently described inflammatory disease caused by mutations in the UBA1 gene. Symptoms are diverse and include fevers, cartilaginous inflammation, lung inflammation, vasculitis, neutrophilic dermatoses, and macrocytic anemia. Cytoplasmic inclusions in myeloid and erythroid progenitors in the bone marrow are a hallmark feature. Here we report the first case of VEXAS with non-caseating granulomas in the bone marrow.
CASE PRESENTATION
A 62-year-old Asian male presented with fevers, erythema nodosum, inflammatory arthritis, and periorbital inflammation. Labs were significant for persistently elevated inflammatory markers and macrocytic anemia. Over the years his symptoms and inflammatory markers only improved with glucocorticoids and recurred when prednisone dose was lowered below 15-20 mg daily. He underwent bone marrow biopsy showing non-caseating granulomas and PET scan showing hilar/mediastinal lymphadenopathy. He was initially diagnosed with IgG4-related disease (treated with rituximab) and later sarcoidosis (treated with infliximab). After failing these agents, the possibility of VEXAS was considered and later confirmed by molecular testing.
CONCLUSIONS
To the best of our knowledge, this is the first observation of non-caseating granulomas in VEXAS, a cautionary reminder of its non-specificity since misinterpretation can lead to diagnostic delay. VEXAS should be in the differential in patients with symptoms of chronic inflammation responding positively to steroids (but not to B-cell depletion or TNF inhibition), which is in line with previous literature.
PubMed: 37430338
DOI: 10.1186/s41927-023-00343-w -
BioRxiv : the Preprint Server For... Oct 2023Exposure of adipocytes to 'cool' temperatures often found in the periphery of the body induces expression of Stearoyl-CoA Desaturase-1 (SCD1), an enzyme that converts...
Exposure of adipocytes to 'cool' temperatures often found in the periphery of the body induces expression of Stearoyl-CoA Desaturase-1 (SCD1), an enzyme that converts saturated fatty acids to monounsaturated fatty acids. In this study, we employed knockout cells and mouse models, along with pharmacological SCD1 inhibition, to investigate further the roles of SCD1 in adipocytes. Our study reveals that production of monounsaturated lipids by SCD1 is necessary for fusion of autophagosomes to lysosomes and that with a SCD1-deficiency, autophagosomes accumulate. In addition, SCD1-deficiency impairs lysosomal and autolysosomal acidification resulting in vacuole accumulation and eventual cell death. Blocking autophagosome formation or supplementation with monounsaturated fatty acids maintains vitality of SCD1-deficient adipocytes. Taken together, our results demonstrate that inhibition of SCD1 in adipocytes leads to autophagy-dependent cell death, and depletion leads to loss of bone marrow adipocytes.
PubMed: 37961537
DOI: 10.1101/2023.10.27.564376 -
Autophagy Sep 2023Macroautophagy/autophagy is a process through which the phagophores engulf non-essential or damaged cellular materials, forming double-membrane autophagosomes (APs) and...
Macroautophagy/autophagy is a process through which the phagophores engulf non-essential or damaged cellular materials, forming double-membrane autophagosomes (APs) and fusing with lysosomes/vacuoles, after which the materials are degraded for recycling purposes. Autophagy is associated with increased cell survival under different stress conditions. AP-lysosome/vacuole fusion is a critical step in autophagy. Some mutant cells can accumulate phagophores under autophagy-induction conditions. Autophagy is interrupted when accumulated phagophores cannot fuse with lysosomes/vacuoles, resulting in a significant decrease in cell survivability. However, phagophore-lysosome/vacuole fusion has been reported in related mammalian cells and yeast mutant cells. This observation indicates that it is possible to restore a partial autophagy process after interruption. Furthermore, these findings indicate that phagophore closure is not a prerequisite for its fusion with the lysosome/vacuole in the mutant cells. The phagophore-lysosome/vacuole fusion strategy can significantly rescue defective autophagy due to failed phagophore closure. This commentary discusses the fusion of phagophores and lysosomes/vacuoles and implications of such fusion events.: AB: autophagic body; AL: autolysosome; AP: autophagosome; ATG: autophagy related; EM: electron microscopy; ESCRT: endosomal sorting complex required for transport; ET: electron tomography; FIB: focus ion beam; IM: inner membrane; KO: knockout; LAMP1: lysosomal-associated membrane protein 1; OM; outer membrane; STX17: syntaxin 17; TEM: transmission electron microscopy; TM: transmembrane domain; Vps: vacuolar protein sorting; WT: wild-type.
Topics: Animals; Autophagosomes; Vacuoles; Saccharomyces cerevisiae; Autophagy; Lysosomes; Membrane Fusion; Mammals
PubMed: 37083184
DOI: 10.1080/15548627.2023.2205272 -
Current Biology : CB Aug 2023Controlling intracellular osmolarity is essential to all cellular life. Cells that live in hypo-osmotic environments, such as freshwater, must constantly battle water...
Controlling intracellular osmolarity is essential to all cellular life. Cells that live in hypo-osmotic environments, such as freshwater, must constantly battle water influx to avoid swelling until they burst. Many eukaryotic cells use contractile vacuoles to collect excess water from the cytosol and pump it out of the cell. Although contractile vacuoles are essential to many species, including important pathogens, the mechanisms that control their dynamics remain unclear. To identify the basic principles governing contractile vacuole function, we investigate here the molecular mechanisms of two species with distinct vacuolar morphologies from different eukaryotic lineages: the discoban Naegleria gruberi and the amoebozoan slime mold Dictyostelium discoideum. Using quantitative cell biology, we find that although these species respond differently to osmotic challenges, they both use vacuolar-type proton pumps for filling contractile vacuoles and actin for osmoregulation, but not to power water expulsion. We also use analytical modeling to show that cytoplasmic pressure is sufficient to drive water out of contractile vacuoles in these species, similar to findings from the alveolate Paramecium multimicronucleatum. These analyses show that cytoplasmic pressure is sufficient to drive contractile vacuole emptying for a wide range of cellular pressures and vacuolar geometries. Because vacuolar-type proton-pump-dependent contractile vacuole filling and pressure-dependent emptying have now been validated in three eukaryotic lineages that diverged well over a billion years ago, we propose that this represents an ancient eukaryotic mechanism of osmoregulation.
Topics: Cytosol; Dictyostelium; Osmolar Concentration; Water-Electrolyte Balance; Vacuoles; Eukaryota; Water
PubMed: 37478864
DOI: 10.1016/j.cub.2023.06.061 -
Proceedings of the National Academy of... Oct 2023Cellular systems are known to exhibit some of the fastest movements in biology, but little is known as to how single cells can dissipate this energy rapidly and adapt to...
Cellular systems are known to exhibit some of the fastest movements in biology, but little is known as to how single cells can dissipate this energy rapidly and adapt to such large accelerations without disrupting internal architecture. To address this, we investigate -a giant cell (1-4 mm in length) well-known to exhibit ultrafast contractions (50% of body length) within 5 ms with a peak acceleration of 15[Formula: see text]. Utilizing transmitted electron microscopy and confocal imaging, we identify an association of rough endoplasmic reticulum (RER) and vacuoles throughout the cell-forming a contiguous fenestrated membrane architecture that topologically entangles these two organelles. A nearly uniform interorganelle spacing of 60 nm is observed between RER and vacuoles, closely packing the entire cell. Inspired by the entangled organelle structure, we study the mechanical properties of entangled deformable particles using a vertex-based model, with all simulation parameters matching 10 dimensionless numbers to ensure dynamic similarity. We demonstrate how entangled deformable particles respond to external loads by an increased viscosity against squeezing and help preserve spatial relationships. Because this enhanced damping arises from the entanglement of two networks incurring a strain-induced jamming transition at subcritical volume fractions, which is demonstrated through the spatial correlation of velocity direction, we term this phenomenon "topological damping." Our findings suggest a mechanical role of RER-vacuolar meshwork as a metamaterial capable of damping an ultrafast contraction event.
Topics: Microscopy, Electron; Vacuoles; Giant Cells; Head
PubMed: 37792511
DOI: 10.1073/pnas.2303940120