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Cells Feb 2024proliferates by budding, which includes the formation of a cytoplasmic protrusion called the 'bud', into which DNA, RNA, proteins, organelles, and other materials are... (Review)
Review
proliferates by budding, which includes the formation of a cytoplasmic protrusion called the 'bud', into which DNA, RNA, proteins, organelles, and other materials are transported. The transport of organelles into the growing bud must be strictly regulated for the proper inheritance of organelles by daughter cells. In yeast, the RING-type E3 ubiquitin ligases, Dma1 and Dma2, are involved in the proper inheritance of mitochondria, vacuoles, and presumably peroxisomes. These organelles are transported along actin filaments toward the tip of the growing bud by the myosin motor protein, Myo2. During organelle transport, organelle-specific adaptor proteins, namely Mmr1, Vac17, and Inp2 for mitochondria, vacuoles, and peroxisomes, respectively, bridge the organelles and myosin. After reaching the bud, the adaptor proteins are ubiquitinated by the E3 ubiquitin ligases and degraded by the proteasome. Targeted degradation of the adaptor proteins is necessary to unload vacuoles, mitochondria, and peroxisomes from the actin-myosin machinery. Impairment of the ubiquitination of adaptor proteins results in the failure of organelle release from myosin, which, in turn, leads to abnormal dynamics, morphology, and function of the inherited organelles, indicating the significance of proper organelle unloading from myosin. Herein, we summarize the role and regulation of E3 ubiquitin ligases during organelle inheritance in yeast.
Topics: Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Ubiquitin-Protein Ligases; Peroxisomes; Myosins; Ubiquitins; Cell Cycle Proteins; Mitochondrial Proteins
PubMed: 38391905
DOI: 10.3390/cells13040292 -
Microbiology (Reading, England) Nov 2023is an obligate intracellular pathogenic bacterium that causes heartwater, a fatal disease of ruminants in tropical areas. Some human cases have also been reported. This... (Review)
Review
is an obligate intracellular pathogenic bacterium that causes heartwater, a fatal disease of ruminants in tropical areas. Some human cases have also been reported. This globally important pathogen is primarily transmitted by ticks of the genus and threatens American mainland. replicates within eukaryotic mammal or tick cell is a membrane-bound vacuole, where it undergoes a biphasic developmental growth cycle and differentiates from noninfectious replicative form into infectious elementary bodies. The ability of to hijack host cellular processes and avoid innate immunity is a fundamental, but not yet fully understood, virulence trait of this stealth pathogen in the genomic era.
Topics: Ehrlichia ruminantium
PubMed: 37994906
DOI: 10.1099/mic.0.001415 -
Cells Aug 2023The putative phospholipase Atg15 is required for the intravacuolar lysis of autophagic bodies and MVB vesicles. Intracellular membrane lysis is a highly sophisticated...
The putative phospholipase Atg15 is required for the intravacuolar lysis of autophagic bodies and MVB vesicles. Intracellular membrane lysis is a highly sophisticated mechanism that is not fully understood. The amino-terminal transmembrane domain of Atg15 contains the sorting signal for entry into the MVB pathway. By replacing this domain, we generated chimeras located in the cytosol, the vacuole membrane, and the lumen. The variants at the vacuole membrane and in the lumen were highly active. Together with the absence of Atg15 from the phagophore and autophagic bodies, this suggests that, within the vacuole, Atg15 can lyse vesicles where it is not embedded. In-depth topological analyses showed that Atg15 is a single membrane-spanning protein with the amino-terminus in the cytosol and the rest, including the active site motif, in the ER lumen. Remarkably, only membrane-embedded Atg15 variants affected growth when overexpressed. The growth defects depended on its active site serine 332, showing that it was linked to the enzymatic activity of Atg15. Interestingly, the growth defects were independent of vacuolar proteinase A and vacuolar acidification.
Topics: Saccharomyces cerevisiae; Autophagy; Autophagosomes; Cell Death; Cell Movement; Fungal Proteins; Membrane Proteins
PubMed: 37626866
DOI: 10.3390/cells12162056 -
ELife Mar 2024Membrane contact sites (MCSs) are junctures that perform important roles including coordinating lipid metabolism. Previous studies have indicated that vacuolar...
Membrane contact sites (MCSs) are junctures that perform important roles including coordinating lipid metabolism. Previous studies have indicated that vacuolar fission/fusion processes are coupled with modifications in the membrane lipid composition. However, it has been still unclear whether MCS-mediated lipid metabolism controls the vacuolar morphology. Here, we report that deletion of tricalbins (Tcb1, Tcb2, and Tcb3), tethering proteins at endoplasmic reticulum (ER)-plasma membrane (PM) and ER-Golgi contact sites, alters fusion/fission dynamics and causes vacuolar fragmentation in the yeast . In addition, we show that the sphingolipid precursor phytosphingosine (PHS) accumulates in tricalbin-deleted cells, triggering the vacuolar division. Detachment of the nucleus-vacuole junction (NVJ), an important contact site between the vacuole and the perinuclear ER, restored vacuolar morphology in both cells subjected to high exogenous PHS and Tcb3-deleted cells, supporting that PHS transport across the NVJ induces vacuole division. Thus, our results suggest that vacuolar morphology is maintained by MCSs through the metabolism of sphingolipids.
Topics: Mitochondrial Membranes; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Vacuoles; Sphingolipids; Lipid Metabolism; Cell Membrane
PubMed: 38536872
DOI: 10.7554/eLife.89938 -
Journal of Plant Physiology Aug 2024Vacuoles account for 90% of plant cell volume and play important roles in maintaining osmotic pressure, storing metabolites and lysosomes, compartmentalizing harmful...
Vacuoles account for 90% of plant cell volume and play important roles in maintaining osmotic pressure, storing metabolites and lysosomes, compartmentalizing harmful ions, and storing and reusing minerals. These functions closely relay on the ion channels and transporters located on the tonoplast. The separation of intact vacuoles from plant cells is the key technology utilized in the study of tonoplast-located ion channels and transporters. However, the current vacuole separation methods are available for Arabidopsis and some other dicotyledons but are lacking for monocot crops. In this study, we established a new method for the vacuole separation from wheat mesophyll cells and investigated the transmembrane proton flux of tonoplasts with non-invasive micro-test technology (NMT). Moreover, our study provides a technology for the study of vacuole functions in monocot crops.
Topics: Triticum; Vacuoles; Mesophyll Cells
PubMed: 38761672
DOI: 10.1016/j.jplph.2024.154258 -
Autophagy Jan 2024Macroautophagy/autophagy is a conserved process in eukaryotes responsible for degrading unwanted or damaged macromolecules and organelles through the lysosome or vacuole...
Macroautophagy/autophagy is a conserved process in eukaryotes responsible for degrading unwanted or damaged macromolecules and organelles through the lysosome or vacuole for recycling and reutilization. Our previous studies revealed the degradation of chloroplast proteins through a pathway dependent on the ubiquitin proteasome system, known as CHLORAD. Recently, we demonstrated a role for selective autophagy in regulating chloroplast protein import and enhancing stress tolerance in plants. Specifically, we found that K63-ubiquitination of TOC components at the chloroplast outer envelope membrane is recognized by the selective autophagy adaptor NBR1, leading to the degradation of TOC proteins under UV-B irradiation and heat stresses in Arabidopsis. This process was shown to control chloroplast protein import and influence photosynthetic activity. Based on our results, we have, for the first time, demonstrated that selective autophagy plays a vital role in chloroplast protein degradation, specifically in response to certain abiotic stresses.
Topics: Macroautophagy; Autophagy; Proteins; Chloroplasts; Plants; Arabidopsis; Vacuoles; Carrier Proteins; Arabidopsis Proteins
PubMed: 37635361
DOI: 10.1080/15548627.2023.2251324 -
Trends in Microbiology May 2024In the tug-of-war between host and pathogen, both evolve to combat each other's defence arsenals. Intracellular phagosomal bacteria have developed strategies to modify... (Review)
Review
In the tug-of-war between host and pathogen, both evolve to combat each other's defence arsenals. Intracellular phagosomal bacteria have developed strategies to modify the vacuolar niche to suit their requirements best. Conversely, the host tries to target the pathogen-containing vacuoles towards the degradative pathways. The host cells use a robust system through intracellular trafficking to maintain homeostasis inside the cellular milieu. In parallel, intracellular bacterial pathogens have coevolved with the host to harbour strategies to manipulate cellular pathways, organelles, and cargoes, facilitating the conversion of the phagosome into a modified pathogen-containing vacuole (PCV). Key molecular regulators of intracellular traffic, such as changes in the organelle (phospholipid) composition, recruitment of small GTPases and associated effectors, soluble N-ethylmaleimide-sensitive factor-activating protein receptors (SNAREs), etc., are hijacked to evade lysosomal degradation. Legionella, Salmonella, Coxiella, Chlamydia, Mycobacterium, and Brucella are examples of pathogens which diverge from the endocytic pathway by using effector-mediated mechanisms to overcome the challenges and establish their intracellular niches. These pathogens extensively utilise and modulate the end processes of secretory pathways, particularly SNAREs, in repurposing the PCV into specialised compartments resembling the host organelles within the secretory network; at the same time, they avoid being degraded by the host's cellular mechanisms. Here, we discuss the recent research advances on the host-pathogen interaction/crosstalk that involves host SNAREs, conserved cellular processes, and the ongoing host-pathogen defence mechanisms in the molecular arms race against each other. The current knowledge of SNAREs, and intravacuolar bacterial pathogen interactions, enables us to understand host cellular innate immune pathways, maintenance of homeostasis, and potential therapeutic strategies to combat ever-growing antimicrobial resistance.
Topics: Host-Pathogen Interactions; Vacuoles; Humans; SNARE Proteins; Bacteria; Phagosomes; Animals; Legionella; Homeostasis
PubMed: 38040624
DOI: 10.1016/j.tim.2023.11.002 -
Journal of Plant Physiology Oct 2023Unlike animals, plants and yeasts only have a class III phosphatidylinositol 3-kinase (PI3KC3). Its lipid product, phosphatidylinositol 3-phosphate (PtdIns-3-P, PI3P),...
Unlike animals, plants and yeasts only have a class III phosphatidylinositol 3-kinase (PI3KC3). Its lipid product, phosphatidylinositol 3-phosphate (PtdIns-3-P, PI3P), organizes intracellular trafficking routes such as autophagosome formation, multivesicular body (MVB) formation, retro-transport from trans-Golgi network (TGN) to late Golgi, and the fusion events between autophagosomes and MVBs and the vacuole. The catalytic subunit of plant PI3KC3 is encoded by the essential gene Vacuolar Protein Sorting 34 (VPS34). Despite the importance of VPS34 in cellular homeostasis and plant development, a VPS34 interactome is lacking. Here we employed TurboID, an enzyme-catalyzed proximity labelling (PL) method, to describe a proximal interactome of Arabidopsis VPS34. TurboID catalyzed spatially restricted biotinylation and enabled VPS34-specific enrichment of 273 proteins from affinity purification coupled with mass spectrometry. The interactome confirmed known functions of VPS34 in endo-lysosomal trafficking. Intriguingly, carbohydrate metabolism was the most enriched Gene Ontology (GO) term, including glycolytic enzymes in the triose portion and enzymes functioning in chloroplast triose export and sucrose biosynthesis. The interaction between VPS34 and the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH, GAPC1/2) was validated in planta. Also verified was the interaction between VPS34 and the plasma membrane H-ATPase AHA2, a primary determinant of membrane potential. Our study links PI3KC3 to carbohydrate metabolism and membrane potential, two key processes that maintain cellular homeostasis.
PubMed: 37748420
DOI: 10.1016/j.jplph.2023.154100 -
Current Nutrition Reports Sep 2023Essential or primary hypertension (HT) is a worldwide health problem with no definitive cure. Although the exact pathogenesis of HT is not known, genetic factors,... (Review)
Review
PURPOSE OF REVIEW
Essential or primary hypertension (HT) is a worldwide health problem with no definitive cure. Although the exact pathogenesis of HT is not known, genetic factors, increased renin-angiotensin and sympathetic system activity, endothelial dysfunction, oxidative stress, and inflammation play a role in its development. Environmental factors such as sodium intake are also important for BP regulation, and excess sodium intake in the form of salt (NaCl, sodium chloride) increases blood pressure in salt-sensitive people. Excess salt intake increases extracellular volume, oxidative stress, inflammation, and endothelial dysfunction. Recent evidence suggests that increased salt intake also disturbs mitochondrial function both structurally and functionally which is important as mitochondrial dysfunction is associated with HT. In the current review, we have summarized the experimental and clinical data regarding the impact of salt intake on mitochondrial structure and function.
RECENT FINDINGS
Excess salt intake damage mitochondrial structure (e.g., shorter mitochondria with less cristae, increased mitochondrial fission, increased mitochondrial vacuolization). Functionally, high salt intake impairs mitochondrial oxidative phosphorylation and electron transport chain, ATP production, mitochondrial calcium homeostasis, mitochondrial membrane potential, and mitochondrial uncoupling protein function. Excess salt intake also increases mitochondrial oxidative stress and modifies Krebs cycle protein expressions. Studies have shown that high salt intake impairs mitochondrial structure and function. These maladaptive mitochondrial changes facilitate the development of HT especially in salt-sensitive individuals. High salt intake impairs many functional and structural components of mitochondria. These mitochondrial alterations along with increased salt intake promote the development of hypertension.
Topics: Humans; Sodium Chloride, Dietary; Hypertension; Blood Pressure; Sodium; Inflammation
PubMed: 37386238
DOI: 10.1007/s13668-023-00486-9 -
Cell Reports Aug 2023Xenophagy is an evolutionarily conserved host defensive mechanism to eliminate invading microorganisms through autophagic machinery. The intracellular bacterial pathogen...
Xenophagy is an evolutionarily conserved host defensive mechanism to eliminate invading microorganisms through autophagic machinery. The intracellular bacterial pathogen Legionella pneumophila can avoid clearance by the xenophagy pathway via the actions of multiple Dot/Icm effector proteins. Previous studies have shown that p62, an adaptor protein involved in xenophagy signaling, is excluded from Legionella-containing vacuoles (LCVs). Such defects are attributed to the multifunctional SidE family effectors (SidEs) that exhibit classic deubiquitinase (DUB) and phosphoribosyl ubiquitination (PR-ubiquitination) activities, yet the mechanism remains elusive. In the present study, we demonstrate that the host DUB USP14 is PR-ubiquitinated by SidEs at multiple serine residues, which impairs its DUB activity and its interactions with p62. The exclusion of p62 from the bacterial phagosome requires the ubiquitin ligase but not the DUB activity of SidEs. These results reveal that PR-ubiquitination of USP14 by SidEs contributes to the evasion of xenophagic clearance by L. pneumophila.
Topics: Humans; Legionella; Legionnaires' Disease; Serine; Bacterial Proteins; Ubiquitination; Ubiquitin; Phagosomes; Vacuoles; Ubiquitin Thiolesterase
PubMed: 37471226
DOI: 10.1016/j.celrep.2023.112817