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International Journal of Medical... Jan 2018Septins are a relatively little understood group of GTPases that form large assemblies in cells from all eukaryotes other than plants. Septins were first identified in... (Review)
Review
Septins are a relatively little understood group of GTPases that form large assemblies in cells from all eukaryotes other than plants. Septins were first identified in cell division but have also been implicated in microbial infections. Septins often associate with cytoskeletal proteins - most often described for filamentous (F-) actin - and are considered cytoskeletal components themselves. Septins have increasingly been found to partake in processes that are linked to intracellular membranes, from mitochondria to phagosomes, and evidence is accumulating that septins specifically bind to membranes. Since a number of microorganisms have specialized to live and grow inside membranous vacuoles in the cytosol of mammalian cells, this membrane-association of septins suggests that septins may also be involved in the membranous, vacuolar structures that develop around these microbes. However, data are limited on this issue: septins have been identified by proteome analysis on some microbe-bearing vacuoles, but more extensive experimental data are only available for infections with the obligate intracellular bacterium Chlamydia trachomatis. In this review article I will discuss the available data and speculate about the mechanisms of recruitment and potential functions of septins for vacuole-dwelling microorganisms, which may be peculiar to Chlamydia or may pertain more generally to this class of microbes.
Topics: Actins; Animals; Bacterial Infections; Chlamydia trachomatis; Cytoskeleton; Cytosol; Humans; Intracellular Membranes; Septins; Vacuoles
PubMed: 28784332
DOI: 10.1016/j.ijmm.2017.07.010 -
Journal of Experimental Botany May 2021Plant cells contain two types of vacuoles, the lytic vacuole (LV) and protein storage vacuole (PSV). LVs are present in vegetative cells, whereas PSVs are found in seed... (Review)
Review
Plant cells contain two types of vacuoles, the lytic vacuole (LV) and protein storage vacuole (PSV). LVs are present in vegetative cells, whereas PSVs are found in seed cells. The physiological functions of the two types of vacuole differ. Newly synthesized proteins must be transported to these vacuoles via protein trafficking through the endomembrane system for them to function. Recently, significant advances have been made in elucidating the molecular mechanisms of protein trafficking to these organelles. Despite these advances, the relationship between the trafficking mechanisms to the LV and PSV remains unclear. Some aspects of the trafficking mechanisms are common to both types of vacuole, but certain aspects are specific to trafficking to either the LV or PSV. In this review, we summarize recent findings on the components involved in protein trafficking to both the LV and PSV and compare them to examine the extent of overlap in the trafficking mechanisms. In addition, we discuss the interconnection between the LV and PSV provided by the protein trafficking machinery and the implications for the identity of these organelles.
Topics: Plant Cells; Plant Proteins; Protein Transport; Seeds; Vacuoles
PubMed: 33587748
DOI: 10.1093/jxb/erab067 -
Physical Biology Oct 2020A central question in eukaryotic cell biology asks, during cell division, how is the growth and distribution of organelles regulated to ensure each daughter cell...
A central question in eukaryotic cell biology asks, during cell division, how is the growth and distribution of organelles regulated to ensure each daughter cell receives an appropriate amount. For vacuoles in budding yeast, there are well described organelle-to-cell size scaling trends as well as inheritance mechanisms involving highly coordinated movements. It is unclear whether such mechanisms are necessary in the symmetrically dividing fission yeast, Schizosaccharomyces pombe, in which random partitioning may be utilized to distribute vacuoles to daughter cells. To address the increasing need for high-throughput analysis, we are augmenting existing semi-automated image processing by developing fully automated machine learning methods for locating vacuoles and segmenting fission yeast cells from brightfield and fluorescence micrographs. All strains studied show qualitative correlations in vacuole-to-cell size scaling trends, i.e. vacuole volume, surface area, and number all increase with cell size. Furthermore, increasing vacuole number was found to be a consistent mechanism for the increase in total vacuole size in the cell. Vacuoles are not distributed evenly throughout the cell with respect to available cytoplasm. Rather, vacuoles show distinct peaks in distribution close to the nucleus, and this preferential localization was confirmed in mutants in which nucleus position is perturbed. Disruption of microtubules leads to quantitative changes in both vacuole size scaling trends and distribution patterns, indicating the microtubule cytoskeleton is a key mechanism for maintaining vacuole structure.
Topics: Schizosaccharomyces; Vacuoles
PubMed: 33035200
DOI: 10.1088/1478-3975/aba510 -
Trends in Plant Science Dec 2023Photorespiration is inevitable for oxygenic photosynthesis. It has fascinated researchers over decades because of its multicompartmental organization. Recently, Lin and...
Photorespiration is inevitable for oxygenic photosynthesis. It has fascinated researchers over decades because of its multicompartmental organization. Recently, Lin and Tsay identified a vacuole glycerate transporter contributing to photorespiratory metabolism under short-term nitrogen depletion. This key finding adds a fifth interacting subcellular compartment and extends the photorespiratory metabolic repair module.
Topics: Vacuoles; Photosynthesis; Membrane Transport Proteins; Oxygen; Nitrogen
PubMed: 37635005
DOI: 10.1016/j.tplants.2023.08.008 -
MSphere Aug 2023is an obligate, intracellular parasite. Infection of a cell produces a unique niche for the parasite named the parasitophorous vacuole (PV) initially composed of host...
is an obligate, intracellular parasite. Infection of a cell produces a unique niche for the parasite named the parasitophorous vacuole (PV) initially composed of host plasma membrane invaginated during invasion. The PV and its membrane (parasitophorous vacuole membrane [PVM]) are subsequently decorated with a variety of parasite proteins allowing the parasite to optimally grow in addition to manipulate host processes. Recently, we reported a proximity-labeling screen at the PVM-host interface and identified host endoplasmic reticulum (ER)-resident motile sperm domain-containing protein 2 (MOSPD2) as being enriched at this location. Here we extend these findings in several important respects. First, we show that the extent and pattern of host MOSPD2 association with the PVM differ dramatically in cells infected with different strains of . Second, in cells infected with Type I RH strain, the MOSPD2 staining is mutually exclusive with regions of the PVM that associate with mitochondria. Third, immunoprecipitation and liquid chromatography tandem mass spectrometry (LC-MS/MS) with epitope-tagged MOSPD2-expressing host cells reveal strong enrichment of several PVM-localized parasite proteins, although none appear to play an essential role in MOSPD2 association. Fourth, most MOSPD2 associating with the PVM is newly translated after infection of the cell and requires the major functional domains of MOSPD2, identified as the CRAL/TRIO domain and tail anchor, although these domains were not sufficient for PVM association. Lastly, ablation of MOSPD2 results in, at most, a modest impact on growth . Collectively, these studies provide new insight into the molecular interactions involving MOSPD2 at the dynamic interface between the PVM and the host cytosol. IMPORTANCE is an intracellular pathogen that lives within a membranous vacuole inside of its host cell. This vacuole is decorated by a variety of parasite proteins that allow it to defend against host attack, acquire nutrients, and interact with the host cell. Recent work identified and validated host proteins enriched at this host-pathogen interface. Here, we follow up on one candidate named MOSPD2 shown to be enriched at the vacuolar membrane and describe it as having a dynamic interaction at this location depending on a variety of factors. Some of these include the presence of host mitochondria, intrinsic domains of the host protein, and whether translation is active. Importantly, we show that MOSPD2 enrichment at the vacuole membrane differs between strains indicating active involvement of the parasite with this phenotype. Altogether, these results shed light on the mechanism and role of protein associations in the host-pathogen interaction.
Topics: Male; Animals; Toxoplasma; Vacuoles; Chromatography, Liquid; Protozoan Proteins; Semen; Tandem Mass Spectrometry; Membrane Proteins
PubMed: 37341482
DOI: 10.1128/msphere.00670-22 -
Autophagy 2018Membrane protein recycling is a fundamental process from yeast to humans. The lysosome (or vacuole in yeast) receives membrane proteins from the secretory, endocytic,...
Membrane protein recycling is a fundamental process from yeast to humans. The lysosome (or vacuole in yeast) receives membrane proteins from the secretory, endocytic, and macroautophagy/autophagy pathways. Although some of these membrane proteins appear to be recycled, the molecular mechanisms underlying this retrograde trafficking are poorly understood. Our recent study revealed that the transmembrane autophagy protein Atg27 is recycled from the vacuole membrane using a 2-step recycling process. First, the Snx4 complex recycles Atg27 from the vacuole to the endosome. Then, the retromer complex mediates endosome-to-Golgi retrograde transport. Thus, 2 distinct protein complexes facilitate the sequential retrograde trafficking for Atg27. As far as we know, Atg27 is the first physiological substrate for the vacuole-to-endosome retrograde trafficking pathway.
Topics: Endosomes; Golgi Apparatus; Intracellular Membranes; Lysosomes; Membrane Fusion; Membrane Proteins; Models, Biological; Protein Transport; Vacuoles
PubMed: 29995558
DOI: 10.1080/15548627.2018.1496719 -
Life Science Alliance Sep 2022Membrane contact sites are functional nodes at which organelles reorganize metabolic pathways and adapt to changing cues. In , the nuclear envelope subdomain surrounding...
Membrane contact sites are functional nodes at which organelles reorganize metabolic pathways and adapt to changing cues. In , the nuclear envelope subdomain surrounding the nucleolus, very plastic and prone to expansion, can establish contacts with the vacuole and be remodeled in response to various metabolic stresses. While using genotoxins with unrelated purposes, we serendipitously discovered a fully new remodeling event at this nuclear subdomain: the nuclear envelope partitions into its regular contact with the vacuole and a dramatic internalization within the nucleus. This leads to the nuclear engulfment of a globular, cytoplasmic portion. In spite of how we discovered it, the phenomenon is likely DNA damage-independent. We define lipids supporting negative curvature, such as phosphatidic acid and sterols, as bona fide drivers of this event. Mechanistically, we suggest that the engulfment of the cytoplasm triggers a suction phenomenon that enhances the docking of proton pump-containing vesicles with the vacuolar membrane, which we show matches a boost in autophagy. Thus, our findings unveil an unprecedented remodeling of the nucleolus-surrounding membranes with impact on metabolic adaptation.
Topics: Autophagy; Cytoplasm; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Vacuoles
PubMed: 35568434
DOI: 10.26508/lsa.202101160 -
Current Biology : CB Jan 2016Macroautophagy (hereafter autophagy) is an evolutionarily conserved process in which portions of the cytoplasm are engulfed, degraded, and subsequently recycled. The... (Review)
Review
Macroautophagy (hereafter autophagy) is an evolutionarily conserved process in which portions of the cytoplasm are engulfed, degraded, and subsequently recycled. The Atg17-Atg31-Atg29 complex translocates to the phagophore assembly site (PAS), where an autophagosome forms, at a very early stage of autophagy, playing a vital role in autophagy induction. Here, we identified a novel role of this complex in a late stage of autophagy where it coordinates with Atg11 to regulate autophagy-specific fusion with the vacuole. Atg17 and Atg11 interact with the vacuolar SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) Vam7 independently of each other. Several hydrophobic residues in helix 1 and helix 4 of Atg17 and the SNARE domain of Vam7 mediate the Atg17-Vam7 interaction. An F317D mutation of Atg17, which diminishes its interaction with Vam7 without affecting its interaction with Atg13 or Atg31, leads to a defect in the fusion of autophagosomes with the vacuole and decreased autophagy activity. These results provide the first demonstration that the Atg17-Atg31-Atg29 complex functions in both early and late stages of autophagy and also provide a mechanistic explanation for the coordination of autophagosome completion and fusion with the vacuole.
Topics: Animals; Autophagy; Autophagy-Related Proteins; Humans; Membrane Fusion; Phagosomes; Protein Binding; Saccharomyces cerevisiae Proteins; Vacuoles
PubMed: 26774783
DOI: 10.1016/j.cub.2015.11.054 -
International Journal of Molecular... Jan 2023Vacuolar processing enzymes (VPEs) are plant cysteine proteases that are subjected to autoactivation in an acidic pH. It is presumed that VPEs, by activating other... (Review)
Review
Vacuolar processing enzymes (VPEs) are plant cysteine proteases that are subjected to autoactivation in an acidic pH. It is presumed that VPEs, by activating other vacuolar hydrolases, are in control of tonoplast rupture during programmed cell death (PCD). Involvement of VPEs has been indicated in various types of plant PCD related to development, senescence, and environmental stress responses. Another pathway induced during such processes is autophagy, which leads to the degradation of cellular components and metabolite salvage, and it is presumed that VPEs may be involved in the degradation of autophagic bodies during plant autophagy. As both PCD and autophagy occur under similar conditions, research on the relationship between them is needed, and VPEs, as key vacuolar proteases, seem to be an important factor to consider. They may even constitute a potential point of crosstalk between cell death and autophagy in plant cells. This review describes new insights into the role of VPEs in plant PCD, with an emphasis on evidence and hypotheses on the interconnections between autophagy and cell death, and indicates several new research opportunities.
Topics: Apoptosis; Plants; Vacuoles; Autophagy; Cell Death
PubMed: 36674706
DOI: 10.3390/ijms24021198 -
Parasitology Research Apr 2018Toxoplasma gondii, the etiological agent of toxoplasmosis, infects nucleated cells and then resides and multiplies within a parasitophorous vacuole. For this purpose,...
Toxoplasma gondii, the etiological agent of toxoplasmosis, infects nucleated cells and then resides and multiplies within a parasitophorous vacuole. For this purpose, the parasite secretes many virulence factors for the purpose of invading and subverting the host microbicidal defenses in order to facilitate its survival in the intracellular milieu. Essential metals are structural components of proteins and enzymes or cofactors of enzymatic reactions responsible for these parasitic survival mechanisms. However, an excess of non-essential or essential metals can lead to parasite death. Thus, infected host cells were incubated with 20 μM ZnCl in conjunction with 3 μM CdCl or HgCl for 12 h in order to investigate cellular events and organelle damage related to intracellular parasite death and elimination. In the presence of these metals, the tachyzoites undergo lipid uptake and transport impairment, functional and structural mitochondrial disorders, DNA condensation, and acidification of the parasitophorous vacuole, thus leading to parasite death. Additional research has suggested that lysosome-vacuole fusion was involved in parasite elimination since acid phosphatases were found inside the parasitophorous vacuole, and vacuoles containing parasites were also positive for autophagy. In conclusion, low concentrations of CdCl, HgCl, and ZnCl can cause damage to Toxoplasma gondii organelles, leading to loss of viability, organelle death, and elimination without causing toxic effects to host cells.
Topics: Animals; Autophagy; Biological Transport; Cadmium Chloride; Cell Line; Chlorides; Host-Parasite Interactions; Lysosomes; Macaca mulatta; Mercuric Chloride; Mitochondria; Nucleic Acid Denaturation; Toxoplasma; Vacuoles; Virulence Factors; Zinc Compounds
PubMed: 29455419
DOI: 10.1007/s00436-018-5806-x