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Stefaniak, Szymon, Łukasz Wojtyla, Małgorzata Pietrowska-Borek y Sławomir Borek. "Completing Autophagy: Formation and Degradation of the Autophagic Body and Metabolite Salvage in Plants". International Journal of Molecular Sciences 21, n.º 6 (23 de marzo de 2020): 2205. http://dx.doi.org/10.3390/ijms21062205.
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Autophagy is an evolutionarily conserved process that occurs in yeast, plants, and animals. Despite many years of research, some aspects of autophagy are still not fully explained. This mostly concerns the final stages of autophagy, which have not received as much interest from the scientific community as the initial stages of this process. The final stages of autophagy that we take into consideration in this review include the formation and degradation of the autophagic bodies as well as the efflux of metabolites from the vacuole to the cytoplasm. The autophagic bodies are formed through the fusion of an autophagosome and vacuole during macroautophagy and by vacuolar membrane invagination or protrusion during microautophagy. Then they are rapidly degraded by vacuolar lytic enzymes, and products of the degradation are reused. In this paper, we summarize the available information on the trafficking of the autophagosome towards the vacuole, the fusion of the autophagosome with the vacuole, the formation and decomposition of autophagic bodies inside the vacuole, and the efflux of metabolites to the cytoplasm. Special attention is given to the formation and degradation of autophagic bodies and metabolite salvage in plant cells.
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Hariri, Mehrdad, Ghania Millane, Marie-Pierre Guimond, Ginette Guay, James W. Dennis y Ivan R. Nabi. "Biogenesis of Multilamellar Bodies via Autophagy". Molecular Biology of the Cell 11, n.º 1 (enero de 2000): 255–68. http://dx.doi.org/10.1091/mbc.11.1.255.
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Transfection of Mv1Lu mink lung type II alveolar cells with β1–6-N-acetylglucosaminyl transferase V is associated with the expression of large lysosomal vacuoles, which are immunofluorescently labeled for the lysosomal glycoprotein lysosomal-associated membrane protein-2 and the β1–6-branchedN-glycan-specific lectin phaseolis vulgaris leucoagglutinin. By electron microscopy, the vacuoles present the morphology of multilamellar bodies (MLBs). Treatment of the cells with the lysosomal protease inhibitor leupeptin results in the progressive transformation of the MLBs into electron-dense autophagic vacuoles and eventual disappearance of MLBs after 4 d of treatment. Heterologous structures containing both membrane lamellae and peripheral electron-dense regions appear 15 h after leupeptin addition and are indicative of ongoing lysosome–MLB fusion. Leupeptin washout is associated with the formation after 24 and 48 h of single or multiple foci of lamellae within the autophagic vacuoles, which give rise to MLBs after 72 h. Treatment with 3-methyladenine, an inhibitor of autophagic sequestration, results in the significantly reduced expression of multilamellar bodies and the accumulation of inclusion bodies resembling nascent or immature autophagic vacuoles. Scrape-loaded cytoplasmic FITC-dextran is incorporated into lysosomal-associated membrane protein-2–positive MLBs, and this process is inhibited by 3-methyladenine, demonstrating that active autophagy is involved in MLB formation. Our results indicate that selective resistance to lysosomal degradation within the autophagic vacuole results in the formation of a microenvironment propicious for the formation of membrane lamella.
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Bjørkøy, Geir, Trond Lamark, Andreas Brech, Heidi Outzen, Maria Perander, Aud Øvervatn, Harald Stenmark y Terje Johansen. "p62/SQSTM1 forms protein aggregates degraded by autophagy and has a protective effect on huntingtin-induced cell death". Journal of Cell Biology 171, n.º 4 (14 de noviembre de 2005): 603–14. http://dx.doi.org/10.1083/jcb.200507002.
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Autophagic degradation of ubiquitinated protein aggregates is important for cell survival, but it is not known how the autophagic machinery recognizes such aggregates. In this study, we report that polymerization of the polyubiquitin-binding protein p62/SQSTM1 yields protein bodies that either reside free in the cytosol and nucleus or occur within autophagosomes and lysosomal structures. Inhibition of autophagy led to an increase in the size and number of p62 bodies and p62 protein levels. The autophagic marker light chain 3 (LC3) colocalized with p62 bodies and coimmunoprecipitated with p62, suggesting that these two proteins participate in the same complexes. The depletion of p62 inhibited recruitment of LC3 to autophagosomes under starvation conditions. Strikingly, p62 and LC3 formed a shell surrounding aggregates of mutant huntingtin. Reduction of p62 protein levels or interference with p62 function significantly increased cell death that was induced by the expression of mutant huntingtin. We suggest that p62 may, via LC3, be involved in linking polyubiquitinated protein aggregates to the autophagy machinery.
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Wleklik, Karolina, Szymon Stefaniak, Katarzyna Nuc, Małgorzata Pietrowska-Borek y Sławomir Borek. "Identification and Potential Participation of Lipases in Autophagic Body Degradation in Embryonic Axes of Lupin (Lupinus spp.) Germinating Seeds". International Journal of Molecular Sciences 25, n.º 1 (20 de diciembre de 2023): 90. http://dx.doi.org/10.3390/ijms25010090.
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Autophagy is a fundamental process for plants that plays a crucial role in maintaining cellular homeostasis and promoting survival in response to various environmental stresses. One of the lesser-known stages of plant autophagy is the degradation of autophagic bodies in vacuoles. To this day, no plant vacuolar enzyme has been confirmed to be involved in this process. On the other hand, several enzymes have been described in yeast (Saccharomyces cerevisiae), including Atg15, that possess lipolytic activity. In this preliminary study, which was conducted on isolated embryonic axes of the white lupin (Lupinus albus L.) and Andean lupin (Lupinus mutabilis Sweet), the potential involvement of plant vacuolar lipases in the degradation of autophagic bodies was investigated. We identified in transcriptomes (using next-generation sequencing (NGS)) of white and Andean lupin embryonic axes 38 lipases with predicted vacuolar localization, and for three of them, similarities in amino acid sequences with yeast Atg15 were found. A comparative transcriptome analysis of lupin isolated embryonic axes cultured in vitro under different sucrose and asparagine nutrition, evaluating the relations in the levels of the transcripts of lipase genes, was also carried out. A clear decrease in lipase gene transcript levels caused by asparagine, a key amino acid in lupin seed metabolism which retards the degradation of autophagic bodies during sugar-starvation-induced autophagy in lupin embryonic axes, was detected. Although the question of whether lipases are involved in the degradation of autophagic bodies during plant autophagy is still open, our findings strongly support such a hypothesis.
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Takeshige, K., M. Baba, S. Tsuboi, T. Noda y Y. Ohsumi. "Autophagy in yeast demonstrated with proteinase-deficient mutants and conditions for its induction." Journal of Cell Biology 119, n.º 2 (15 de octubre de 1992): 301–11. http://dx.doi.org/10.1083/jcb.119.2.301.
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For determination of the physiological role and mechanism of vacuolar proteolysis in the yeast Saccharomyces cerevisiae, mutant cells lacking proteinase A, B, and carboxypeptidase Y were transferred from a nutrient medium to a synthetic medium devoid of various nutrients and morphological changes of their vacuoles were investigated. After incubation for 1 h in nutrient-deficient media, a few spherical bodies appeared in the vacuoles and moved actively by Brownian movement. These bodies gradually increased in number and after 3 h they filled the vacuoles almost completely. During their accumulation, the volume of the vacuolar compartment also increased. Electron microscopic examination showed that these bodies were surrounded by a unit membrane which appeared thinner than any other intracellular membrane. The contents of the bodies were morphologically indistinguishable from the cytosol; these bodies contained cytoplasmic ribosomes, RER, mitochondria, lipid granules and glycogen granules, and the density of the cytoplasmic ribosomes in the bodies was almost the same as that of ribosomes in the cytosol. The diameter of the bodies ranged from 400 to 900 nm. Vacuoles that had accumulated these bodies were prepared by a modification of the method of Ohsumi and Anraku (Ohsumi, Y., and Y. Anraku. 1981. J. Biol. Chem. 256:2079-2082). The isolated vacuoles contained ribosomes and showed latent activity of the cytosolic enzyme glucose-6-phosphate dehydrogenase. These results suggest that these bodies sequestered the cytosol in the vacuoles. We named these spherical bodies "autophagic bodies." Accumulation of autophagic bodies in the vacuoles was induced not only by nitrogen starvation, but also by depletion of nutrients such as carbon and single amino acids that caused cessation of the cell cycle. Genetic analysis revealed that the accumulation of autophagic bodies in the vacuoles was the result of lack of the PRB1 product proteinase B, and disruption of the PRB1 gene confirmed this result. In the presence of PMSF, wild-type cells accumulated autophagic bodies in the vacuoles under nutrient-deficient conditions in the same manner as did multiple protease-deficient mutants or cells with a disrupted PRB1 gene. As the autophagic bodies disappeared rapidly after removal of PMSF from cultures of normal cells, they must be an intermediate in the normal autophagic process. This is the first report that nutrient-deficient conditions induce extensive autophagic degradation of cytosolic components in the vacuoles of yeast cells.
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Yang, Zhifen, Ju Huang, Jiefei Geng, Usha Nair y Daniel J. Klionsky. "Atg22 Recycles Amino Acids to Link the Degradative and Recycling Functions of Autophagy". Molecular Biology of the Cell 17, n.º 12 (diciembre de 2006): 5094–104. http://dx.doi.org/10.1091/mbc.e06-06-0479.
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In response to stress conditions (such as nutrient limitation or accumulation of damaged organelles) and certain pathological situations, eukaryotic cells use autophagy as a survival mechanism. During nutrient stress the main purpose of autophagy is to degrade cytoplasmic materials within the lysosome/vacuole lumen and generate an internal nutrient pool that is recycled back to the cytosol. This study elucidates a molecular mechanism for linking the degradative and recycling roles of autophagy. We show that in contrast to published studies, Atg22 is not directly required for the breakdown of autophagic bodies within the lysosome/vacuole. Instead, we demonstrate that Atg22, Avt3, and Avt4 are partially redundant vacuolar effluxers, which mediate the efflux of leucine and other amino acids resulting from autophagic degradation. The release of autophagic amino acids allows the maintenance of protein synthesis and viability during nitrogen starvation. We propose a “recycling” model that includes the efflux of macromolecules from the lysosome/vacuole as the final step of autophagy.
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Baba, M., K. Takeshige, N. Baba y Y. Ohsumi. "Ultrastructural analysis of the autophagic process in yeast: detection of autophagosomes and their characterization". Journal of Cell Biology 124, n.º 6 (15 de marzo de 1994): 903–13. http://dx.doi.org/10.1083/jcb.124.6.903.
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Under nutrient-deficient conditions, the yeast S. cerevisiae sequesters its own cytoplasmic components into vacuoles in the form of "autophagic bodies" (Takeshige, K., M. Baba, S. Tsuboi, T. Noda, and Y. Ohsumi. 1992. J. Cell Biol. 119:301-311). Immunoelectron microscopy showed that two cytosolic marker enzymes, alcohol dehydrogenase and phosphoglycerate kinase, are present in the autophagic bodies at the same densities as in the cytosol, but are not present in vacuolar sap, suggesting that cytosolic enzymes are also taken up into the autophagic bodies. To understand this process, we performed morphological analyses by transmission and immunological electron microscopies using a freeze-substitution fixation method. Spherical structures completely enclosed in a double membrane were found near the vacuoles of protease-deficient mutant cells when the cells were shifted to nutrient-starvation media. Their size, membrane thickness, and contents of double membrane-structures corresponded well with those of autophagic bodies. Sometimes these double membrane structures were found to be in contact with the vacuolar membrane. Furthermore their outer membrane was occasionally seen to be continuous with the vacuolar membrane. Histochemical staining of carbohydrate strongly suggested that the structures with double membranes fused with the vacuoles. These results indicated that these structures are precursors of autophagic bodies, "autophagosomes" in yeast. All the data obtained suggested that the autophagic process in yeast is essentially similar to that of the lysosomal system in mammalian cells.
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Epple, Ulrike D., Ivet Suriapranata, Eeva-Liisa Eskelinen y Michael Thumm. "Aut5/Cvt17p, a Putative Lipase Essential for Disintegration of Autophagic Bodies inside the Vacuole". Journal of Bacteriology 183, n.º 20 (15 de octubre de 2001): 5942–55. http://dx.doi.org/10.1128/jb.183.20.5942-5955.2001.
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ABSTRACT Selective disintegration of membrane-enclosed autophagic bodies is a feature of eukaryotic cells not studied in detail. Using aSaccharomyces cerevisiae mutant defective in autophagic-body breakdown, we identified and characterized Aut5p, a glycosylated integral membrane protein. Site-directed mutagenesis demonstrated the relevance of its putative lipase active-site motif for autophagic-body breakdown. aut5Δ cells show reduced protein turnover during starvation and are defective in maturation of proaminopeptidase I. Most recently, by means of the latter phenotype, Aut5p was independently identified as Cvt17p. In this study we additionally checked for effects on vacuolar acidification and detected mature vacuolar proteases, both of which are prerequisites for autophagic-body lysis. Furthermore, biologically active hemagglutinin-tagged Aut5p (Aut5-Ha) localizes to the endoplasmic reticulum (nuclear envelope) and is targeted to the vacuolar lumen independent of autophagy. In pep4Δ cells immunogold electron microscopy located Aut5-Ha at ∼50-nm-diameter intravacuolar vesicles. Characteristic missorting in vps class E and fab1Δ cells, which affects the multivesicular body (MVB) pathway, suggests vacuolar targeting of Aut5-Ha similar to that of the MVB pathway. In agreement with localization of Aut5-Ha at intravacuolar vesicles inpep4Δ cells and the lack of vacuolar Aut5-Ha in wild-type cells, our pulse-chase experiments clearly indicated that Aut5-Ha degradation with 50 to 70 min of half-life is dependent on vacuolar proteinase A.
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Li, Qingrong, Xiaojuan Deng, Wanying Yang, Zhijun Huang, Gianluca Tettamanti, Yang Cao y Qili Feng. "Autophagy, apoptosis, and ecdysis-related gene expression in the silk gland of the silkworm (Bombyx mori) during metamorphosis". Canadian Journal of Zoology 88, n.º 12 (diciembre de 2010): 1169–78. http://dx.doi.org/10.1139/z10-083.
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Degeneration of larval-specific tissues during insect metamorphosis has been suggested to be the result of apoptosis and autophagy and is triggered by ecdysteroids. However, the relationship between autophagy and apoptosis pathways and the mechanism of regulation by ecdysteroids remain to be elucidated. This study examined the events of autophagy, apoptosis, and the expression of ecdysis-related genes in the silk gland of the silkworm ( Bombyx mori L., 1758) during the larval to pupal transformation. The results indicated that autophagic features appeared in the silk gland at the wandering and spinning stages of the larvae, whereas the apoptotic features such as apoptotic bodies and DNA fragmentation occurred at the prepupal or early-pupal stages. The autophagic granules fused with each other to form large vacuoles where the cytoplasmic material was degraded. Autophagosomes, autolysosomes, and apoptotic bodies were found later in the degenerating silk-gland cells. Expression of the ecdysone receptor gene BmEcR and the transcription factor genes BmE74A and BmBR-C preceded the onset of autophagy and apoptosis, indicating that they may be responsible for triggering these programmed cell death pathways in the silk gland. The results suggest that both autophagy and apoptosis occur in the silk-gland cells during degeneration, but autophagy precedes apoptosis.
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Dernovics, Áron, György Seprényi, Zsolt Rázga, Ferhan Ayaydin, Zoltán Veréb y Klára Megyeri. "Phenol-Soluble Modulin α3 Stimulates Autophagy in HaCaT Keratinocytes". Biomedicines 11, n.º 11 (10 de noviembre de 2023): 3018. http://dx.doi.org/10.3390/biomedicines11113018.
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Background: Phenol-soluble modulins (PSMs) are pore-forming toxins (PFTs) produced by staphylococci. PSMs exert diverse cellular effects, including lytic, pro-apoptotic, pro-inflammatory and antimicrobial actions. Since the effects of PSMs on autophagy have not yet been reported, we evaluated the autophagic activity in HaCaT keratinocytes treated with recombinant PSMα3. Methods: The autophagic flux and levels of autophagic marker proteins were determined using Western blot analysis. Subcellular localization of LC3B and Beclin-1 was investigated using an indirect immunofluorescence assay. The ultrastructural features of control and PSMα3-treated cells were evaluated via transmission electron microscopy. Cytoplasmic acidification was measured via acridine orange staining. Phosphorylation levels of protein kinases, implicated in autophagy regulation, were studied using a phospho-kinase array and Western blot analysis. Results: PSMα3 facilitated the intracellular redistribution of LC3B, increased the average number of autophagosomes per cell, promoted the development of acidic vesicular organelles, elevated the levels of LC3B-II, stimulated autophagic flux and triggered a significant decrease in the net autophagic turnover rate. PSMα3 induced the accumulation of autophagosomes/autolysosomes, amphisomes and multilamellar bodies at the 0.5, 6 and 24 h time points, respectively. The phospho-Akt1/2/3 (T308 and S473), and phospho-mTOR (S2448) levels were decreased, whereas the phospho-Erk1/2 (T202/Y204 and T185/Y187) level was increased in PSMα3-treated cells. Conclusions: In HaCaT keratinocytes, PSMα3 stimulates autophagy. The increased autophagic activity elicited by sub-lytic PSM concentrations might be an integral part of the cellular defense mechanisms protecting skin homeostasis.
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Montiel, Teresa, Luis A. Montes-Ortega, Susana Flores-Yáñez y Lourdes Massieu. "Treatment with the Ketone Body D-β-hydroxybutyrate Attenuates Autophagy Activated by NMDA and Reduces Excitotoxic Neuronal Damage in the Rat Striatum In Vivo". Current Pharmaceutical Design 26, n.º 12 (6 de mayo de 2020): 1377–87. http://dx.doi.org/10.2174/1381612826666200115103646.
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Background: The ketone bodies (KB), β-hydroxybutyrate (BHB) and acetoacetate, have been proposed for the treatment of acute and chronic neurological disorders, however, the molecular mechanisms involved in KB protection are not well understood. KB can substitute for glucose and support mitochondrial metabolism increasing cell survival. We have reported that the D-isomer of BHB (D-BHB) stimulates autophagic degradation during glucose deprivation in cultured neurons increasing cell viability. Autophagy is a lysosomal degradation process of damaged proteins and organelles activated during nutrient deprivation to obtain building blocks and energy. However, impaired or excessive autophagy can contribute to neuronal death. Objective: The aim of the present study was to test whether D-BHB can preserve autophagic function in an in vivo model of excitotoxic damage induced by the administration of the glutamate receptor agonist, N-methyl-Daspartate (NMDA), in the rat striatum. Methods: D-BHB was administered through an intravenous injection followed by either an intraperitoneal injection (i.v+i.p) or a continuous epidural infusion (i.v+pump), or through a continuous infusion of D-BHB alone. Changes in the autophagy proteins ATG7, ATG5, BECLIN 1 (BECN1), LC3, Sequestrosome1/p62 (SQSTM1/ p62) and the lysosomal membrane protein LAMP2, were evaluated by immunoblot. The lesion volume was measured in cresyl violet-stained brain sections. Results: Autophagy is activated early after NMDA injection but autophagic degradation is impaired due to the cleavage of LAMP2. Twenty-four h after NMDA intrastriatal injection, the autophagic flux is re-established, but LAMP2 cleavage is still observed. The administration of D-BHB through the i.v+pump protocol reduced the content of autophagic proteins and the cleavage of LAMP2, suggesting decreased autophagosome formation and lysosomal membrane preservation, improving autophagic degradation. D-BHB also reduced brain injury. The i.v+i.p administration protocol and the infusion of D-BHB alone showed no effect on autophagy activation or degradation.
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Robinson, Carolyn-Ann, Gillian K. Singh, Mariel Kleer, Thalia Katsademas, Elizabeth L. Castle, Bre Q. Boudreau y Jennifer A. Corcoran. "Kaposi’s sarcoma-associated herpesvirus (KSHV) utilizes the NDP52/CALCOCO2 selective autophagy receptor to disassemble processing bodies". PLOS Pathogens 19, n.º 1 (12 de enero de 2023): e1011080. http://dx.doi.org/10.1371/journal.ppat.1011080.
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Kaposi’s sarcoma-associated herpesvirus (KSHV) causes the inflammatory and angiogenic endothelial cell neoplasm, Kaposi’s sarcoma (KS). We previously demonstrated that the KSHV Kaposin B (KapB) protein promotes inflammation via the disassembly of cytoplasmic ribonucleoprotein granules called processing bodies (PBs). PBs modify gene expression by silencing or degrading labile messenger RNAs (mRNAs), including many transcripts that encode inflammatory or angiogenic proteins associated with KS disease. Although our work implicated PB disassembly as one of the causes of inflammation during KSHV infection, the precise mechanism used by KapB to elicit PB disassembly was unclear. Here we reveal a new connection between the degradative process of autophagy and PB disassembly. We show that both latent KSHV infection and KapB expression enhanced autophagic flux via phosphorylation of the autophagy regulatory protein, Beclin. KapB was necessary for this effect, as infection with a recombinant virus that does not express the KapB protein did not induce Beclin phosphorylation or autophagic flux. Moreover, we showed that PB disassembly mediated by KSHV or KapB, depended on autophagy genes and the selective autophagy receptor NDP52/CALCOCO2 and that the PB scaffolding protein, Pat1b, co-immunoprecipitated with NDP52. These studies reveal a new role for autophagy and the selective autophagy receptor NDP52 in promoting PB turnover and the concomitant synthesis of inflammatory molecules during KSHV infection.
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Cebollero, Eduardo y Ramon Gonzalez. "Induction of Autophagy by Second-Fermentation Yeasts during Elaboration of Sparkling Wines". Applied and Environmental Microbiology 72, n.º 6 (junio de 2006): 4121–27. http://dx.doi.org/10.1128/aem.02920-05.
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ABSTRACT Autophagy is a transport system mediated by vesicles, ubiquitous in eukaryotic cells, by which bulk cytoplasm is targeted to a lysosome or vacuole for degradation. In the yeast Saccharomyces cerevisiae, autophagy is triggered by nutritional stress conditions (e.g., carbon- or nitrogen-depleted medium). In this study we showed that there is induction of autophagy in second-fermentation yeasts during sparkling wine making. Two methods were employed to detect autophagy: a biochemical approach based on depletion of the protein acetaldehyde dehydrogenase Ald6p and a morphological strategy consisting of visualization of autophagic bodies and autophagosomes, which are intermediate vesicles in the autophagic process, by transmission electron microscopy. This study provides the first demonstration of autophagy in second-fermentation yeasts under enological conditions. The correlation between autophagy and yeast autolysis during sparkling wine production is discussed, and genetic engineering of autophagy-related genes in order to accelerate the aging steps in wine making is proposed.
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Kim, Hei, Seo-Yeon Park, Seok Moon, Jeong Lee y Sungjoo Kim. "Autophagy in Human Skin Fibroblasts: Impact of Age". International Journal of Molecular Sciences 19, n.º 8 (1 de agosto de 2018): 2254. http://dx.doi.org/10.3390/ijms19082254.
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Autophagy is an intracellular stress response that is enhanced under starvation conditions, and also when the cellular components are damaged. Aging accompanies an increase in intracellular stress and has significant impact on the skin. Since dermal fibroblasts are a powerful indicator of skin aging, we compared the autophagic activity of human skin fibroblasts between the young and old. According to TEM analyses, the number of autophagosomes per 1 μm2 cytoplasmic area was similar between young and aged fibroblasts. The amount of LC3 (microtubule-associated protein 1 light chain 3)-II, a form associated with autophagic vacuolar membranes, was also similar between the groups from Western blot analysis. Although residual bodies were more common in aged dermal fibroblasts, LC3 turnover and p62 assay showed little difference in the rate of lysosomal proteolysis between the young and old. RNA-seq analysis revealed that the major autophagy-modulating genes (BECN1, MAP1LC3B, ATG5, ATG7, ULK1, PIK3C3, mTOR) were not differentially expressed with age. Our results suggest that the basal autophagic flux in aged dermal fibroblasts is largely comparable to that of young fibroblasts. However, with a higher speed and amount of waste production in aged cells, we postulate that such autophagic flux may not be sufficient in keeping the old cells “clean”, resulting in skin aging. Aging is a complex process and, as such, the relationship between autophagy and aging is not straightforward. That is to say, autophagy does not simply decline with age. Regardless of the controversies on autophagic activity with age, autophagy plays a crucial role in counteracting aging, and strategies aimed at its modulation should hold promise for the prevention of skin aging.
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Jankó, Laura, Zsanett Sári, Tünde Kovács, Gréta Kis, Magdolna Szántó, Miklós Antal, Gábor Juhász y Péter Bai. "Silencing of PARP2 Blocks Autophagic Degradation". Cells 9, n.º 2 (7 de febrero de 2020): 380. http://dx.doi.org/10.3390/cells9020380.
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Poly(ADP-Ribose) polymerases (PARPs) are enzymes that metabolize NAD+. PARP1 and PARP10 were previously implicated in the regulation of autophagy. Here we showed that cytosolic electron-dense particles appear in the cytoplasm of C2C12 myoblasts in which PARP2 is silenced by shRNA. The cytosolic electron-dense bodies resemble autophagic vesicles and, in line with that, we observed an increased number of LC3-positive and Lysotracker-stained vesicles. Silencing of PARP2 did not influence the maximal number of LC3-positive vesicles seen upon chloroquine treatment or serum starvation, suggesting that the absence of PARP2 inhibits autophagic breakdown. Silencing of PARP2 inhibited the activity of AMP-activated kinase (AMPK) and the mammalian target of rapamycin complex 2 (mTORC2). Treatment of PARP2-silenced C2C12 cells with AICAR, an AMPK activator, nicotinamide-riboside (an NAD+ precursor), or EX-527 (a SIRT1 inhibitor) decreased the number of LC3-positive vesicles cells to similar levels as in control (scPARP2) cells, suggesting that these pathways inhibit autophagic flux upon PARP2 silencing. We observed a similar increase in the number of LC3 vesicles in primary PARP2 knockout murine embryonic fibroblasts. We provided evidence that the enzymatic activity of PARP2 is important in regulating autophagy. Finally, we showed that the silencing of PARP2 induces myoblast differentiation. Taken together, PARP2 is a positive regulator of autophagic breakdown in mammalian transformed cells and its absence blocks the progression of autophagy.
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Tanida, Isei, Tomohiro Haruta, Mitsuo Suga, Shunsuke Takei, Akira Takebe, Yoko Furuta, Junji Yamaguchi, Juan Alejandro Oliva Trejo, Soichiro Kakuta y Yasuo Uchiyama. "Membranous Structures Directly Come in Contact With p62/SQSTM1 Bodies". Journal of Histochemistry & Cytochemistry 69, n.º 6 (22 de abril de 2021): 407–14. http://dx.doi.org/10.1369/00221554211011423.
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During autophagy, autophagosomes are formed to engulf cytoplasmic contents. p62/SQSTM-1 is an autophagic adaptor protein that forms p62 bodies. A unique feature of p62 bodies is that they seem to directly associate with membranous structures. We first investigated the co-localization of mKate2-p62 bodies with phospholipids using click chemistry with propargyl-choline. Propargyl-choline-labeled phospholipids were detected inside the mKate2-p62 bodies, suggesting that phospholipids were present inside the bodies. To clarify whether or not p62 bodies come in contact with membranous structures directly, we investigated the ultrastructures of p62 bodies using in-resin correlative light and electron microscopy of the Epon-embedded cells expressing mKate2-p62. Fluorescent-positive p62 bodies were detected as uniformly lightly osmificated structures by electron microscopy. Membranous structures were detected on and inside the p62 bodies. In addition, multimembranous structures with rough endoplasmic reticulum–like structures that resembled autophagosomes directly came in contact with amorphous-shaped p62 bodies. These results suggested that p62 bodies are unique structures that can come in contact with membranous structures directly:
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Hirata, Eri, Kyo Shirai, Tatsuya Kawaoka, Kosuke Sato, Fumito Kodama y Kuninori Suzuki. "Atg15 in Saccharomyces cerevisiae consists of two functionally distinct domains". Molecular Biology of the Cell 32, n.º 8 (15 de abril de 2021): 645–63. http://dx.doi.org/10.1091/mbc.e20-07-0500.
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Atg15 is a lipase essential for disintegration of autophagic body membranes. In this study, we found that the N-terminal domain alone can travel to the vacuole via the multivesicular body pathway, and identified residues required for degradation of autophagic bodies in the C-terminal lipase domain.
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Fader, Claudio M., Diego Sánchez, Marcelo Furlán y María I. Colombo. "Induction of Autophagy Promotes Fusion of Multivesicular Bodies with Autophagic Vacuoles in K562 Cells". Traffic 9, n.º 2 (12 de noviembre de 2007): 230–50. http://dx.doi.org/10.1111/j.1600-0854.2007.00677.x.
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Nezis, Ioannis P., Anne Simonsen, Antonia P. Sagona, Kim Finley, Sébastien Gaumer, Didier Contamine, Tor Erik Rusten, Harald Stenmark y Andreas Brech. "Ref(2)P, the Drosophila melanogaster homologue of mammalian p62, is required for the formation of protein aggregates in adult brain". Journal of Cell Biology 180, n.º 6 (17 de marzo de 2008): 1065–71. http://dx.doi.org/10.1083/jcb.200711108.
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p62 has been proposed to mark ubiquitinated protein bodies for autophagic degradation. We report that the Drosophila melanogaster p62 orthologue, Ref(2)P, is a regulator of protein aggregation in the adult brain. We demonstrate that Ref(2)P localizes to age-induced protein aggregates as well as to aggregates caused by reduced autophagic or proteasomal activity. A similar localization to protein aggregates is also observed in D. melanogaster models of human neurodegenerative diseases. Although atg8a autophagy mutant flies show accumulation of ubiquitin- and Ref(2)P-positive protein aggregates, this is abrogated in atg8a/ref(2)P double mutants. Both the multimerization and ubiquitin binding domains of Ref(2)P are required for aggregate formation in vivo. Our findings reveal a major role for Ref(2)P in the formation of ubiquitin-positive protein aggregates both under physiological conditions and when normal protein turnover is inhibited.
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Lee, Jihyun, Ji Hoon Jung, Jisung Hwang, Ji Eon Park, Ju-Ha Kim, Woon Yi Park, Jin Young Suh y Sung-Hoon Kim. "CNOT2 Is Critically Involved in Atorvastatin Induced Apoptotic and Autophagic Cell Death in Non-Small Cell Lung Cancers". Cancers 11, n.º 10 (30 de septiembre de 2019): 1470. http://dx.doi.org/10.3390/cancers11101470.
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Though Atorvastatin has been used as a hypolipidemic agent, its anticancer mechanisms for repurposing are not fully understood so far. Thus, in the current study, its apoptotic and autophagic mechanisms were investigated in non-small cell lung cancers (NSCLCs). Atorvastatin increased cytotoxicity, sub G1 population, the number of apoptotic bodies, cleaved poly (ADP-ribose) polymerase (PARP) and caspase 3 and activated p53 in H1299, H596, and H460 cells. Notably, Atorvastatin inhibited the expression of c-Myc and induced ribosomal protein L5 and L11, but depletion of L5 reduced PARP cleavages induced by Atorvastatin rather than L11 in H1299 cells. Also, Atorvastatin increased autophagy microtubule-associated protein 1A/1B-light chain 3II (LC3 II) conversion, p62/sequestosome 1 (SQSTM1) accumulation with increased number of LC3II puncta in H1299 cells. However, late stage autophagy inhibitor chloroquine (CQ) increased cytotoxicity in Atorvastatin treated H1299 cells compared to early stage autophagy inhibitor 3-methyladenine (3-MA). Furthermore, autophagic flux assay using RFP-GFP-LC3 constructs and Lysotracker Red or acridine orange-staining demonstrated that autophagosome-lysosome fusion is blocked by Atorvastatin treatment in H1299 cells. Conversely, overexpression of CCR4-NOT transcription complex subunit 2(CNOT2) weakly reversed the ability of Atorvastatin to increase cytotoxicity, sub G1 population, cleavages of PARP and caspase 3, LC3II conversion and p62/SQSTM1 accumulation in H1299 cells. In contrast, CNOT2 depletion enhanced cleavages of PARP and caspase 3, LC3 conversion and p62/SQSTM1 accumulation in Atorvastatin treated H1299 cells. Overall, these findings suggest that CNOT2 signaling is critically involved in Atorvastatin induced apoptotic and autophagic cell death in NSCLCs.
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Bestion, Eloïne, Keivan Zandi, Sandrine Belouzard, Julien Andreani, Hubert Lepidi, Marie Novello, Clara Rouquairol et al. "GNS561 Exhibits Potent Antiviral Activity against SARS-CoV-2 through Autophagy Inhibition". Viruses 14, n.º 1 (12 de enero de 2022): 132. http://dx.doi.org/10.3390/v14010132.
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Since December 2019, SARS-CoV-2 has spread quickly worldwide, leading to more than 280 million confirmed cases, including over 5,000,000 deaths. Interestingly, coronaviruses were found to subvert and hijack autophagic process to allow their viral replication. Autophagy-modulating compounds thus rapidly emerged as an attractive strategy to fight SARS-CoV-2 infection, including the well-known chloroquine (CQ). Here, we investigated the antiviral activity and associated mechanism of GNS561/Ezurpimtrostat, a small lysosomotropic molecule inhibitor of late-stage autophagy. Interestingly, GNS561 exhibited antiviral activity of 6–40 nM depending on the viral strain considered, currently positioning it as the most powerful molecule investigated in SARS-CoV-2 infection. We then showed that GNS561 was located in lysosome-associated-membrane-protein-2-positive (LAMP2-positive) lysosomes, together with SARS-CoV-2. Moreover, GNS561 increased LC3-II spot size and caused the accumulation of autophagic vacuoles and the presence of multilamellar bodies, suggesting that GNS561 disrupted the autophagy mechanism. To confirm our findings, we used the K18-hACE2 mouse model and highlighted that GNS561 treatment led to a decline in SARS-CoV-2 virions in the lungs associated with a disruption of the autophagy pathway. Overall, our study highlights GNS561 as a powerful drug in the treatment of SARS-CoV-2 infection and supports the hypothesis that autophagy blockers could be an alternative strategy for COVID-19.
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Ding, Jin-Li, Hao Zhang, Ming-Guang Feng y Sheng-Hua Ying. "Divergent Physiological Functions of Four Atg22-like Proteins in Conidial Germination, Development, and Virulence of the Entomopathogenic Fungus Beauveria bassiana". Journal of Fungi 9, n.º 2 (15 de febrero de 2023): 262. http://dx.doi.org/10.3390/jof9020262.
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In yeast, Atg22 functions as a vacuolar efflux transporter to release the nutrients from the vacuole to the cytosol after the degradation of autophagic bodies. There are more than one Atg22 domain-containing proteins in filamentous fungi, but their physiological roles are largely unknown. In this study, four Atg22-like proteins (BbAtg22A through D) were functionally characterized in the filamentous entomopathogenic fungus Beauveria bassiana. These Atg22-like proteins exhibit different sub-cellular distributions. BbAtg22A localizes in lipid droplets. BbAtg22B and BbAtg22C are completely distributed in the vacuole, and BbAtg22D has an additional association with the cytomembrane. The ablation of Atg22-like proteins did not block autophagy. Four Atg22-like proteins systematically contribute to the fungal response to starvation and virulence in B. bassiana. With the exception of ∆Bbatg22C, the other three proteins contribute to dimorphic transmission. Additionally, BbAtg22A and BbAtg22D are required for cytomembrane integrity. Meanwhile, four Atg22-like proteins contribute to conidiation. Therefore, Atg22-like proteins link distinct sub-cellular structures for the development and virulence in B. bassiana. Our findings provide a novel insight into the non-autophagic roles of autophagy-related genes in filamentous fungi.
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Imam, Sabrina, Sarah Talley, Rachel S. Nelson, Adarsh Dharan, Christopher O'Connor, Thomas J. Hope y Edward M. Campbell. "TRIM5α Degradation via Autophagy Is Not Required for Retroviral Restriction". Journal of Virology 90, n.º 7 (13 de enero de 2016): 3400–3410. http://dx.doi.org/10.1128/jvi.03033-15.
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ABSTRACTTRIM5α is an interferon-inducible retroviral restriction factor that prevents infection by inducing the abortive disassembly of capsid cores recognized by its C-terminal PRY/SPRY domain. The mechanism by which TRIM5α mediates the disassembly of viral cores is poorly understood. Previous studies demonstrated that proteasome inhibitors abrogate the ability of TRIM5α to induce premature core disassembly and prevent reverse transcription; however, viral infection is still inhibited, indicating that the proteasome is partially involved in the restriction process. Alternatively, we and others have observed that TRIM5α associates with proteins involved in autophagic degradation pathways, and one recent study found that autophagic degradation is required for the restriction of retroviruses by TRIM5α. Here, we show that TRIM5α is basally degraded via autophagy in the absence of restriction-sensitive virus. We observe that the autophagy markers LC3b and lysosome-associated membrane protein 2A (LAMP2A) localize to a subset of TRIM5α cytoplasmic bodies, and inhibition of lysosomal degradation with bafilomycin A1 increases this association. To test the requirement for macroautophagy in restriction, we examined the ability of TRIM5α to restrict retroviral infection in cells depleted of the autophagic mediators ATG5, Beclin1, and p62. In all cases, restriction of retroviruses by human TRIM5α, rhesus macaque TRIM5α, and owl monkey TRIM-Cyp remained potent in cells depleted of these autophagic effectors by small interfering RNA (siRNA) knockdown or clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 genome editing. Collectively, these results are consistent with observations that the turnover of TRIM5α proteins is sensitive to autophagy inhibition; however, the data presented here do not support observations that the inhibition of autophagy abrogates retroviral restriction by TRIM5 proteins.IMPORTANCERestriction factors are a class of proteins that inhibit viral replication. Following fusion of a retrovirus with a host cell membrane, the retroviral capsid is released into the cytoplasm of the target cell. TRIM5α inhibits retroviral infection by promoting the abortive disassembly of incoming retroviral capsid cores; as a result, the retroviral genome is unable to traffic to the nucleus, and the viral life cycle is extinguished. In the process of restriction, TRIM5α itself is degraded by the proteasome. However, in the present study, we have shown that in the absence of a restriction-sensitive virus, TRIM5α is degraded by both proteasomal and autophagic degradation pathways. Notably, we observed that restriction of retroviruses by TRIM5α does not require autophagic machinery. These data indicate that the effector functions of TRIM5α can be separated from its degradation and may have further implications for understanding the mechanisms of other TRIM family members.
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Park, Hyungsun, Ju-Hee Kang y Seongju Lee. "Autophagy in Neurodegenerative Diseases: A Hunter for Aggregates". International Journal of Molecular Sciences 21, n.º 9 (10 de mayo de 2020): 3369. http://dx.doi.org/10.3390/ijms21093369.
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Cells have developed elaborate quality-control mechanisms for proteins and organelles to maintain cellular homeostasis. Such quality-control mechanisms are maintained by conformational folding via molecular chaperones and by degradation through the ubiquitin-proteasome or autophagy-lysosome system. Accumulating evidence suggests that impaired autophagy contributes to the accumulation of intracellular inclusion bodies consisting of misfolded proteins, which is a hallmark of most neurodegenerative diseases. In addition, genetic mutations in core autophagy-related genes have been reported to be linked to neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease. Conversely, the pathogenic proteins, such as amyloid β and α-synuclein, are detrimental to the autophagy pathway. Here, we review the recent advances in understanding the relationship between autophagic defects and the pathogenesis of neurodegenerative diseases and suggest autophagy induction as a promising strategy for the treatment of these conditions.
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Yi, Shuanglong, Linfang Wang, Margaret S. Ho y Shiping Zhang. "The autophagy protein Atg9 functions in glia and contributes to parkinsonian symptoms in a Drosophila model of Parkinson’s disease". Neural Regeneration Research 19, n.º 5 (14 de agosto de 2023): 1150–55. http://dx.doi.org/10.4103/1673-5374.382259.
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Abstract JOURNAL/nrgr/04.03/01300535-202405000-00047/inline-graphic1/v/2023-09-28T063346Z/r/image-tiff Parkinson’s disease is a progressive neurodegenerative disease characterized by motor deficits, dopaminergic neuron loss, and brain accumulation of α-synuclein aggregates called Lewy bodies. Dysfunction in protein degradation pathways, such as autophagy, has been demonstrated in neurons as a critical mechanism for eliminating protein aggregates in Parkinson’s disease. However, it is less well understood how protein aggregates are eliminated in glia, the other cell type in the brain. In the present study, we show that autophagy-related gene 9 (Atg9), the only transmembrane protein in the autophagy machinery, is highly expressed in Drosophila glia from adult brain. Results from immunostaining and live cell imaging analysis reveal that a portion of Atg9 localizes to the trans-Golgi network, autophagosomes, and lysosomes in glia. Atg9 is persistently in contact with these organelles. Lacking glial atg9 reduces the number of omegasomes and autophagosomes, and impairs autophagic substrate degradation. This suggests that glial Atg9 participates in the early steps of autophagy, and hence the control of autophagic degradation. Importantly, loss of glial atg9 induces parkinsonian symptoms in Drosophila including progressive loss of dopaminergic neurons, locomotion deficits, and glial activation. Our findings identify a functional role of Atg9 in glial autophagy and establish a potential link between glial autophagy and Parkinson’s disease. These results may provide new insights on the underlying mechanism of Parkinson’s disease.
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Williams, JB. "Ultrastructural Studies on Kronborgia (Platyhelminthes, Fecampiidae) - the Differentiated Vitellocyte of Kronborgia-Isopodicola Blair and Williams". Australian Journal of Zoology 38, n.º 1 (1990): 79. http://dx.doi.org/10.1071/zo9900079.
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In the adult parasitic female form of K. isopodicola, the vitellocyte cytoplasm contains yolk platelets, lipid bodies, glycogen, myelin figures and mitochondria. The platelets consist of an outer granular zone and an opaque core. All platelets are surrounded by several membranes. Many are cloven into segments by fissures containing membranes. Frequently, small peripheral fragments of the granular zone are pared away, and the core undergoes fragmentation by the same process. Spherical dense bodies are found in the cytoplasm. During the cocoon phase, the platelets are often intricately fragmented, and many pieces are paracrystalline. In the newly deposited egg, many platelets comprise only core segments, which are typically paracrystalline, frequently polygonal, and enveloped by multiple membranes. Spherical dense bodies are not encountered at this stage. The platelets are unlike the 'yolk globules' of Digenea, but are similar to vitelline platelets described for polyclads. In morphology and mode of utilisation they bear some resemblance to yolk granules of Amphibia. The membranes are interpreted as isolating membranes of cellular autophagy. Glycogen synthesis is related to autophagic events involved in yolk degradation. The spherical bodies probably represent eggshell granules; complex shell granules, characteristic of other platyhelminths, were not observed in K. isopodicola.
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Syrjä, Pernilla, Tahira Anwar, Tarja Jokinen, Kaisa Kyöstilä, Karin Hultin Jäderlund, Francesca Cozzi, Cecilia Rohdin et al. "Basal Autophagy Is Altered in Lagotto Romagnolo Dogs with an ATG4D Mutation". Veterinary Pathology 54, n.º 6 (6 de junio de 2017): 953–63. http://dx.doi.org/10.1177/0300985817712793.
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A missense variant in the autophagy-related ATG4D-gene has been associated with a progressive degenerative neurological disease in Lagotto Romagnolo (LR) dogs. In addition to neural lesions, affected dogs show an extraneural histopathological phenotype characterized by severe cytoplasmic vacuolization, a finding not previously linked with disturbed autophagy in animals. Here we aimed at testing the hypothesis that autophagy is altered in the affected dogs, at reporting the histopathology of extraneural tissues and at excluding lysosomal storage diseases. Basal and starvation-induced autophagy were monitored by Western blotting and immunofluorescence of microtubule associated protein 1A/B light chain3 (LC3) in fibroblasts from 2 affected dogs. The extraneural findings of 9 euthanized LRs and skin biopsies from 4 living affected LRs were examined by light microscopy, electron microscopy, and immunohistochemistry (IHC), using antibodies against autophagosomal membranes (LC3), autophagic cargo (p62), and lysosomal membranes (LAMP2). Biochemical screening of urine and fibroblasts of 2 affected dogs was performed. Under basal conditions, the affected fibroblasts contained significantly more LC3-II and LC3-positive vesicles than did the controls. Morphologically, several cells, including serous secretory epithelium, endothelial cells, pericytes, plasma cells, and macrophages, contained cytoplasmic vacuoles with an ultrastructure resembling enlarged amphisomes, endosomes, or multivesicular bodies. IHC showed strong membranous LAMP2 positivity only in sweat glands. The results show that basal but not induced autophagy is altered in affected fibroblasts. The ultrastructure of affected cells is compatible with altered autophagic and endo-lysosomal vesicular traffic. The findings in this spontaneous disease provide insight into possible tissue-specific roles of basal autophagy.
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Gao, Hongjuan, Xiulan Qi, William Jackson y Achsah Keegan. "The complex allergen house dust mite (HDM) acts directly on macrophages to stimulate noncanonical autophagy". Journal of Immunology 202, n.º 1_Supplement (1 de mayo de 2019): 119.21. http://dx.doi.org/10.4049/jimmunol.202.supp.119.21.
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Abstract Asthma is a chronic inflammatory disease that results in narrowing of the airways. Inhalation of house dust mites (HDM) is a main cause of allergic asthma. Macrophages (Mf) are abundant in the lung and are one of the first cells exposed to HDM, however little is known about the effects of HDM on Mf. Autophagy has been linked to Mf phenotypes and asthma but the mechanism by which autophagy contributes to these processes is unclear. Autophagy is a homeostatic process involving degradation of intracellular components, including proteins, organelles, and foreign bodies. To determine whether HDM stimulates autophagy, we treated bone marrow-derived Mf (BMM) with HDM and evaluated autophagosome foci formation. HDM induced foci formation that was similar to treatment with the autophagy inducer Torin 1. Further, electron microscopy revealed an increase in double membraned vesicles in response to HDM and Torin 1, which could be due to an increase in autophagosome formation or inhibition of their fusion with lysosomes. To differentiate these hypotheses, we investigated markers of autophagy. During canonical autophagy, LC3-I is converted to membrane-associated LC3-II by lipidation, while the cargo adapter protein SQSTM1/p62 is degraded. Surprisingly, treatment with HDM caused a general increase in LC3-I and LC3-II without a substantial change in the LC3-II to LC3-I ratio. As expected, Torin 1 induced autophagic degradation demonstrated by reduction of SQSTM1/p62. However, SQSTM1/p62 increased dramatically in response to HDM, indicating a block in autophagic degradation. We observed a similar trend in THP-1 and human CD14+ Mf. These results suggest that HDM engages autophagy machinery but does not stimulate degradative autophagy.
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Paula, Jéssica C., Nilma S. Fernandes, Thaysa K. Karam, Paula Baréa, Maria H. Sarragiotto, Tania Ueda-Nakamura, Sueli O. Silva y Celso V. Nakamura. "β-carbolines RCC and C5 induce the death of Leishmania amazonensis intracellular amastigotes". Future Microbiology 17, n.º 2 (enero de 2022): 99–110. http://dx.doi.org/10.2217/fmb-2020-0263.
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Background: Cutaneous leishmaniasis is caused by Leishmania spp., and its treatment is limited. The β-carbolines have shown activity against kinetoplastids. Aim: To evaluate the activity and effects of the β-carbolines, N-{2-[(4,6-bis(isopropylamino)-1,3,5-triazin-2-yl)amino]ethyl}-1-(4-methoxyphenyl)-β-carboline-3-carboxamide (RCC) and N-benzyl-1-(4-methoxy)phenyl-9H-beta-carboline-3-carboxamide (C5), against L. amazonensis intracellular amastigotes and to suggest their mechanism of action. Methods: We analyzed the activity and cytotoxicity of β-carbolines and the morphological alterations by electron microscopy. Mitochondrial membrane potential, production nitric oxide, reactive oxygen species, lipidic bodies, autophagic vacuoles and ATP were also evaluated. Results & conclusion: The results showed that RCC and C5 are active against intracellular amastigotes and were able to induce oxidative stress and ultrastructural alterations such as accumulation of lipid bodies and autophagic vacuoles, leading to parasite death.
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Gardiner, Tom A. y Alan W. Stitt. "Pericyte and Vascular Smooth Muscle Death in Diabetic Retinopathy Involves Autophagy". International Journal of Translational Medicine 2, n.º 1 (19 de enero de 2022): 26–40. http://dx.doi.org/10.3390/ijtm2010003.
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Diabetic retinopathy (DR) is the most common complication of diabetes and a major cause of vision loss worldwide. The premature death of the microvascular mural cells represents both a pathological hallmark of vasodegeneration in DR and a basis for therapeutic intervention to halt progression to the sight-threatening stages. Recent studies suggest that retinal microvascular mural cells, classed as pericytes in the capillaries and vascular smooth muscle cells in the larger vessels (VSMC), may undergo autophagy-dependent cell death during DR. The present investigation was undertaken to assess electron microscopic evidence for involvement of autophagy in mediation of cell death in the mural cells of the retinal vasculature, in eyes from human diabetic donors and diabetic dogs. All specimens examined showed widespread evidence of autophagosomes in processes of viable pericytes and VSMCs, and the membranous remnants of excessive autophagic activity in their “ghost cell” remnants within the vascular walls. Autophagy was termed “excessive” when it occupied the greater part of the cytoplasm in mural cell processes. This was notable in specimens from short-term diabetic donors with no evidence of basement-membrane thickening or mural cell loss, in which regions of mural cell cytoplasm filled with autophagic bodies appeared to be undergoing cytoplasmic cleavage. No equivalent evidence of autophagy was detected in the adjacent endothelial cells of the retinal vessels. We conclude that increased autophagy in the retinal pericytes and VSMCs is linked to the diabetic milieu, and over time may also act as a trigger for mural cell loss and progressive vasodegeneration.
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Gao, Hongjuan, Xiulan Qi, William Jackson y Achsah D. Keegan. "The complex allergen house dust mite (HDM) dramatically increases the abundance of the autophagy cargo adapter SQSTM1/p62 in macrophages and suppresses Torin 1-induced degradative autophagy". Journal of Immunology 204, n.º 1_Supplement (1 de mayo de 2020): 147.11. http://dx.doi.org/10.4049/jimmunol.204.supp.147.11.
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Abstract Autophagy is an essential homeostatic process involving degradation of intracellular components, including soluble proteins, aggregated proteins, organelles, macromolecular complexes and foreign bodies. Several components of the autophagy pathway have been linked to allergic asthma and macrophage phenotypes, however the contribution of autophagy to these processes is unclear. We previously showed that house dust mite (HDM) increased the number of fluorescent foci (autophagosomes) in bone-marrow derived macrophages (BMM) in a manner similar to the autophagy inducer Torin 1. Further, electron microscopy revealed an increase in double membraned vesicles in response to HDM and Torin 1. While Torin induced a specific increase in lipidated LC3, treatment with HDM caused equal increases in both non-lipidated and lipidated LC3. Torin 1 stimulated autophagic degradation as measured by reduction of SQSTM1/p62. In contrast, SQSTM1/p62 levels increased dramatically in response to HDM. The increase was blocked by actinomycin D and cycloheximide indicating that new gene transcription and protein synthesis is required for the HDM-induced effect. HDM-stimulated increase in SQSTM1/p62 was also observed in alveolar macrophages treated in vitro. An increase in SQSTM1/p62 is often interpreted as a block in autophagic degradation. Indeed, we observed that in the presence of HDM, Torin 1 treatment did not lead to the loss of SQSTM1/p62 below baseline; however, the protein did not accumulate to the high level observed in the HDM-alone treatment group. Our results suggest that HDM engages autophagy machinery at multiple points, both inducing expression of SQSTM1/p62 and suppressing its degradation.
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Liu, Xuezhao, Yang Li, Xin Wang, Ruxiao Xing, Kai Liu, Qiwen Gan, Changyong Tang et al. "The BEACH-containing protein WDR81 coordinates p62 and LC3C to promote aggrephagy". Journal of Cell Biology 216, n.º 5 (12 de abril de 2017): 1301–20. http://dx.doi.org/10.1083/jcb.201608039.
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Autophagy-dependent clearance of ubiquitinated and aggregated proteins is critical to protein quality control, but the underlying mechanisms are not well understood. Here, we report the essential role of the BEACH (beige and Chediak–Higashi) and WD40 repeat-containing protein WDR81 in eliminating ubiquitinated proteins through autophagy. WDR81 associates with ubiquitin (Ub)-positive protein foci, and its loss causes accumulation of Ub proteins and the autophagy cargo receptor p62. WDR81 interacts with p62, facilitating recognition of Ub proteins by p62. Furthermore, WDR81 interacts with LC3C through canonical LC3-interacting regions in the BEACH domain, promoting LC3C recruitment to ubiquitinated proteins. Inactivation of LC3C or defective autophagy results in accumulation of Ub protein aggregates enriched for WDR81. In mice, WDR81 inactivation causes accumulation of p62 bodies in cortical and striatal neurons in the brain. These data suggest that WDR81 coordinates p62 and LC3C to facilitate autophagic removal of Ub proteins, and provide important insights into CAMRQ2 syndrome, a WDR81-related developmental disorder.
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Mejlvang, Jakob, Hallvard Olsvik, Steingrim Svenning, Jack-Ansgar Bruun, Yakubu Princely Abudu, Kenneth Bowitz Larsen, Andreas Brech et al. "Starvation induces rapid degradation of selective autophagy receptors by endosomal microautophagy". Journal of Cell Biology 217, n.º 10 (17 de julio de 2018): 3640–55. http://dx.doi.org/10.1083/jcb.201711002.
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It is not clear to what extent starvation-induced autophagy affects the proteome on a global scale and whether it is selective. In this study, we report based on quantitative proteomics that cells during the first 4 h of acute starvation elicit lysosomal degradation of up to 2–3% of the proteome. The most significant changes are caused by an immediate autophagic response elicited by shortage of amino acids but executed independently of mechanistic target of rapamycin and macroautophagy. Intriguingly, the autophagy receptors p62/SQSTM1, NBR1, TAX1BP1, NDP52, and NCOA4 are among the most efficiently degraded substrates. Already 1 h after induction of starvation, they are rapidly degraded by a process that selectively delivers autophagy receptors to vesicles inside late endosomes/multivesicular bodies depending on the endosomal sorting complex required for transport III (ESCRT-III). Our data support a model in which amino acid deprivation elicits endocytosis of specific membrane receptors, induction of macroautophagy, and rapid degradation of autophagy receptors by endosomal microautophagy.
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Lajoie, P. "The lipid composition of autophagic vacuoles regulates expression of multilamellar bodies". Journal of Cell Science 118, n.º 9 (1 de mayo de 2005): 1991–2003. http://dx.doi.org/10.1242/jcs.02324.
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Backues, Steven K., Dachuan Chen, Jishou Ruan, Zhiping Xie y Daniel J. Klionsky. "Estimating the size and number of autophagic bodies by electron microscopy". Autophagy 10, n.º 1 (11 de noviembre de 2013): 155–64. http://dx.doi.org/10.4161/auto.26856.
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Longobardi, Antonio, Marcella Catania, Andrea Geviti, Erika Salvi, Elena Rita Vecchi, Sonia Bellini, Claudia Saraceno et al. "Autophagy Markers Are Altered in Alzheimer’s Disease, Dementia with Lewy Bodies and Frontotemporal Dementia". International Journal of Molecular Sciences 25, n.º 2 (17 de enero de 2024): 1125. http://dx.doi.org/10.3390/ijms25021125.
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The accumulation of protein aggregates defines distinct, yet overlapping pathologies such as Alzheimer’s disease (AD), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD). In this study, we investigated ATG5, UBQLN2, ULK1, and LC3 concentrations in 66 brain specimens and 120 plasma samples from AD, DLB, FTD, and control subjects (CTRL). Protein concentration was measured with ELISA kits in temporal, frontal, and occipital cortex specimens of 32 AD, 10 DLB, 10 FTD, and 14 CTRL, and in plasma samples of 30 AD, 30 DLB, 30 FTD, and 30 CTRL. We found alterations in ATG5, UBQLN2, ULK1, and LC3 levels in patients; ATG5 and UBQLN2 levels were decreased in both brain specimens and plasma samples of patients compared to those of the CTRL, while LC3 levels were increased in the frontal cortex of DLB and FTD patients. In this study, we demonstrate alterations in different steps related to ATG5, UBQLN2, and LC3 autophagy pathways in DLB and FTD patients. Molecular alterations in the autophagic processes could play a role in a shared pathway involved in the pathogenesis of neurodegeneration, supporting the hypothesis of a common molecular mechanism underlying major neurodegenerative dementias and suggesting different potential therapeutic targets in the autophagy pathway for these disorders.
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Schweiger, Linda, Laura A. Lelieveld-Fast, Snježana Mikuličić, Johannes Strunk, Kirsten Freitag, Stefan Tenzer, Albrecht M. Clement y Luise Florin. "HPV16 Induces Formation of Virus-p62-PML Hybrid Bodies to Enable Infection". Viruses 14, n.º 7 (5 de julio de 2022): 1478. http://dx.doi.org/10.3390/v14071478.
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Human papillomaviruses (HPVs) inflict a significant burden on the human population. The clinical manifestations caused by high-risk HPV types are cancers at anogenital sites, including cervical cancer, as well as head and neck cancers. Host cell defense mechanisms such as autophagy are initiated upon HPV entry. At the same time, the virus modulates cellular antiviral processes and structures such as promyelocytic leukemia nuclear bodies (PML NBs) to enable infection. Here, we uncover the autophagy adaptor p62, also known as p62/sequestosome-1, as a novel proviral factor in infections by the high-risk HPV type 16 (HPV16). Proteomics, imaging and interaction studies of HPV16 pseudovirus-treated HeLa cells display that p62 is recruited to virus-filled endosomes, interacts with incoming capsids, and accompanies the virus to PML NBs, the sites of viral transcription and replication. Cellular depletion of p62 significantly decreased the delivery of HPV16 viral DNA to PML NBs and HPV16 infection rate. Moreover, the absence of p62 leads to an increase in the targeting of viral components to autophagic structures and enhanced degradation of the viral capsid protein L2. The proviral role of p62 and formation of virus-p62-PML hybrid bodies have also been observed in human primary keratinocytes, the HPV target cells. Together, these findings suggest the previously unrecognized virus-induced formation of p62-PML hybrid bodies as a viral mechanism to subvert the cellular antiviral defense, thus enabling viral gene expression.
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Fellner, Lisa, Elisa Gabassi, Johannes Haybaeck y Frank Edenhofer. "Autophagy in α-Synucleinopathies—An Overstrained System". Cells 10, n.º 11 (12 de noviembre de 2021): 3143. http://dx.doi.org/10.3390/cells10113143.
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Alpha-synucleinopathies comprise progressive neurodegenerative diseases, including Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). They all exhibit the same pathological hallmark, which is the formation of α-synuclein positive deposits in neuronal or glial cells. The aggregation of α-synuclein in the cell body of neurons, giving rise to the so-called Lewy bodies (LBs), is the major characteristic for PD and DLB, whereas the accumulation of α-synuclein in oligodendroglial cells, so-called glial cytoplasmic inclusions (GCIs), is the hallmark for MSA. The mechanisms involved in the intracytoplasmic inclusion formation in neuronal and oligodendroglial cells are not fully understood to date. A possible mechanism could be an impaired autophagic machinery that cannot cope with the high intracellular amount of α-synuclein. In fact, different studies showed that reduced autophagy is involved in α-synuclein aggregation. Furthermore, altered levels of different autophagy markers were reported in PD, DLB, and MSA brains. To date, the trigger point in disease initiation is not entirely clear; that is, whether autophagy dysfunction alone suffices to increase α-synuclein or whether α-synuclein is the pathogenic driver. In the current review, we discuss the involvement of defective autophagy machinery in the formation of α-synuclein aggregates, propagation of α-synuclein, and the resulting neurodegenerative processes in α-synucleinopathies.
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Rahman, Muhammad Arifur, Ravinder Kumar, Enrique Sanchez y Taras Y. Nazarko. "Lipid Droplets and Their Autophagic Turnover via the Raft-Like Vacuolar Microdomains". International Journal of Molecular Sciences 22, n.º 15 (29 de julio de 2021): 8144. http://dx.doi.org/10.3390/ijms22158144.
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Although once perceived as inert structures that merely serve for lipid storage, lipid droplets (LDs) have proven to be the dynamic organelles that hold many cellular functions. The LDs’ basic structure of a hydrophobic core consisting of neutral lipids and enclosed in a phospholipid monolayer allows for quick lipid accessibility for intracellular energy and membrane production. Whereas formed at the peripheral and perinuclear endoplasmic reticulum, LDs are degraded either in the cytosol by lipolysis or in the vacuoles/lysosomes by autophagy. Autophagy is a regulated breakdown of dysfunctional, damaged, or surplus cellular components. The selective autophagy of LDs is called lipophagy. Here, we review LDs and their degradation by lipophagy in yeast, which proceeds via the micrometer-scale raft-like lipid domains in the vacuolar membrane. These vacuolar microdomains form during nutrient deprivation and facilitate internalization of LDs via the vacuolar membrane invagination and scission. The resultant intra-vacuolar autophagic bodies with LDs inside are broken down by vacuolar lipases and proteases. This type of lipophagy is called microlipophagy as it resembles microautophagy, the type of autophagy when substrates are sequestered right at the surface of a lytic compartment. Yeast microlipophagy via the raft-like vacuolar microdomains is a great model system to study the role of lipid domains in microautophagic pathways.
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Zheng, Liwen, Wanchun Wang, Jiangdong Ni, Xinzhan Mao, Deye Song, Tang Liu, Jianwei Wei y Huaying Zhou. "Role of autophagy in tumor necrosis factor-α-induced apoptosis of osteoblast cells". Journal of Investigative Medicine 65, n.º 6 (20 de junio de 2017): 1014–20. http://dx.doi.org/10.1136/jim-2017-000426.
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The aim of this study is to investigate the role of tumor necrosis factor-α (TNF-α) in apoptosis and autophagy of mouse osteoblast MC3T3-E1 cells, as well as the crosstalk between autophagy and apoptosis. Mouse osteoblast MC3T3-E1 cells were cultured in vitro and treated with 5-fluorouracil (5-FU), rapamycin, 3-methyl adenine (3-MA) and TNF-α either alone or in combination, respectively. MTT assays were used to monitor the cell viability upon different treatments. Annexin-V-FITC/propidium iodide (PI) staining was used to detect the apoptotic rate of osteoblasts. Autophagic structure and apoptotic bodies were visualized by transmission electron microscopy (TEM). Western blot analysis was performed to detect the autophagic marker LC3-II/I, p62 and apoptotic marker cleaved caspase-3. TNF-α inhibits MC3T3-E1 cell viability in a dose-dependent and time-dependent manner. Annexin-V-FITC/PI staining, coupled with TEM, showed that TNF-α induced cell apoptosis and autophagy in MC3T3-E1 cells. The autophagy inducer rapamycin ameliorated TNF-α-induced apoptosis. In contrast, 3-MA, which is an autophagy inhibitor, caused an exaggerated induction of TNF-α-induced apoptosis. TNF-α upregulated autophagy marker LC3-II/I, but downregulated p62 in osteoblasts. Combined treatment of rapamycin and TNF-α further exaggerated this effect, whereas co-treatment of 3-MA and TNF-α decreased LC3-II/I, but increased p62 compared with TNF-α alone. In addition, TNF-α caused an induction of apoptotic marker cleaved caspase-3. TNF-α-mediated induction of cleaved caspase-3 was downregulated by rapamycin, but upregulated by 3-MA, respectively. TNF-α induced both autophagy and apoptosis in osteoblasts, and upregulated autophagy protects the cell by reducing TNF-α-induced apoptosis.
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Filimonenko, Maria, Susanne Stuffers, Camilla Raiborg, Ai Yamamoto, Lene Malerød, Elizabeth M. C. Fisher, Adrian Isaacs, Andreas Brech, Harald Stenmark y Anne Simonsen. "Functional multivesicular bodies are required for autophagic clearance of protein aggregates associated with neurodegenerative disease". Journal of Cell Biology 179, n.º 3 (5 de noviembre de 2007): 485–500. http://dx.doi.org/10.1083/jcb.200702115.
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The endosomal sorting complexes required for transport (ESCRTs) are required to sort integral membrane proteins into intralumenal vesicles of the multivesicular body (MVB). Mutations in the ESCRT-III subunit CHMP2B were recently associated with frontotemporal dementia and amyotrophic lateral sclerosis (ALS), neurodegenerative diseases characterized by abnormal ubiquitin-positive protein deposits in affected neurons. We show here that autophagic degradation is inhibited in cells depleted of ESCRT subunits and in cells expressing CHMP2B mutants, leading to accumulation of protein aggregates containing ubiquitinated proteins, p62 and Alfy. Moreover, we find that functional MVBs are required for clearance of TDP-43 (identified as the major ubiquitinated protein in ALS and frontotemporal lobar degeneration with ubiquitin deposits), and of expanded polyglutamine aggregates associated with Huntington's disease. Together, our data indicate that efficient autophagic degradation requires functional MVBs and provide a possible explanation to the observed neurodegenerative phenotype seen in patients with CHMP2B mutations.
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Wleklik, Karolina y Sławomir Borek. "Vacuolar Processing Enzymes in Plant Programmed Cell Death and Autophagy". International Journal of Molecular Sciences 24, n.º 2 (7 de enero de 2023): 1198. http://dx.doi.org/10.3390/ijms24021198.
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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.
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Marquardt, Lisa, Marco Montino, Yvonne Mühe, Petra Schlotterhose y Michael Thumm. "Topology and Function of the S. cerevisiae Autophagy Protein Atg15". Cells 12, n.º 16 (12 de agosto de 2023): 2056. http://dx.doi.org/10.3390/cells12162056.
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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.
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Macgregor, Stuart R., Hyun Kyung Lee, Hayley Nelles, Daniel C. Johnson, Tong Zhang, Chaozhi Ma y Daphne R. Goring. "Autophagy is required for self-incompatible pollen rejection in two transgenic Arabidopsis thaliana accessions". Plant Physiology 188, n.º 4 (25 de enero de 2022): 2073–84. http://dx.doi.org/10.1093/plphys/kiac026.
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Abstract Successful reproduction in the Brassicaceae is mediated by a complex series of interactions between the pollen and the pistil, and some species have an additional layer of regulation with the self-incompatibility trait. While the initial activation of the self-incompatibility pathway by the pollen S-locus protein 11/S locus cysteine-rich protein and the stigma S Receptor Kinase is well characterized, the downstream mechanisms causing self-pollen rejection are still not fully understood. In previous studies, we detected the presence of autophagic bodies with self-incompatible (SI) pollinations in Arabidopsis lyrata and transgenic Arabidopsis thaliana lines, but whether autophagy was essential for self-pollen rejection was unknown. Here, we investigated the requirement of autophagy in this response by crossing mutations in the essential AUTOPHAGY7 (ATG7) and ATG5 genes into two different transgenic SI A. thaliana lines in the Col-0 and C24 accessions. By using these previously characterized transgenic lines that express A. lyrata and Arabidopsis halleri self-incompatibility genes, we demonstrated that disrupting autophagy weakened their SI responses in the stigma. When the atg7 or atg5 mutations were present, an increased number of SI pollen was found to hydrate and form pollen tubes that successfully fertilized the SI pistils. Additionally, we confirmed the presence of GFP-ATG8a-labeled autophagosomes in the stigmatic papillae following SI pollinations. Together, these findings support the requirement of autophagy in the self-incompatibility response and add to the growing understanding of the intracellular mechanisms employed in the transgenic A. thaliana stigmas to reject self-pollen.
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Sato, Shigeto, Sachiko Noda, Satoru Torii, Taku Amo, Aya Ikeda, Manabu Funayama, Junji Yamaguchi et al. "Homeostatic p62 levels and inclusion body formation in CHCHD2 knockout mice". Human Molecular Genetics 30, n.º 6 (25 de febrero de 2021): 443–53. http://dx.doi.org/10.1093/hmg/ddab057.
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Abstract Inactivation of constitutive autophagy results in the formation of cytoplasmic inclusions in neurones, but the relationship between impaired autophagy and Lewy bodies (LBs) remains unknown. α-Synuclein and p62, components of LBs, are the defining characteristic of Parkinson’s disease (PD). Until now, we have analyzed mice models and demonstrated p62 aggregates derived from an autophagic defect might serve as ‘seeds’ and can potentially be a cause of LB formation. P62 may be the key molecule for aggregate formation. To understand the mechanisms of LBs, we analyzed p62 homeostasis and inclusion formation using PD model mice. In PARK22-linked PD, intrinsically disordered mutant CHCHD2 initiates Lewy pathology. To determine the function of CHCHD2 for inclusions formation, we generated Chchd2-knockout (KO) mice and characterized the age-related pathological and motor phenotypes. Chchd2 KO mice exhibited p62 inclusion formation and dopaminergic neuronal loss in an age-dependent manner. These changes were associated with a reduction in mitochondria complex activity and abrogation of inner mitochondria structure. In particular, the OPA1 proteins, which regulate fusion of mitochondrial inner membranes, were immature in the mitochondria of CHCHD2-deficient mice. CHCHD2 regulates mitochondrial morphology and p62 homeostasis by controlling the level of OPA1. Our findings highlight the unexpected role of the homeostatic level of p62, which is regulated by a non-autophagic system, in controlling intracellular inclusion body formation, and indicate that the pathologic processes associated with the mitochondrial proteolytic system are crucial for loss of DA neurones.
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Liu, Xuezhao, Limin Yin, Tianyou Li, Lingxi Lin, Jie Zhang y Yang Li. "Reduction of WDR81 impairs autophagic clearance of aggregated proteins and cell viability in neurodegenerative phenotypes". PLOS Genetics 17, n.º 3 (17 de marzo de 2021): e1009415. http://dx.doi.org/10.1371/journal.pgen.1009415.
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Neurodegenerative diseases are characterized by neuron loss and accumulation of undegraded protein aggregates. These phenotypes are partially due to defective protein degradation in neuronal cells. Autophagic clearance of aggregated proteins is critical to protein quality control, but the underlying mechanisms are still poorly understood. Here we report the essential role of WDR81 in autophagic clearance of protein aggregates in models of Huntington’s disease (HD), Parkinson’s disease (PD) and Alzheimer’s disease (AD). In hippocampus and cortex of patients with HD, PD and AD, protein level of endogenous WDR81 is decreased but autophagic receptor p62 accumulates significantly. WDR81 facilitates the recruitment of autophagic proteins onto Htt polyQ aggregates and promotes autophagic clearance of Htt polyQ subsequently. The BEACH and MFS domains of WDR81 are sufficient for its recruitment onto Htt polyQ aggregates, and its WD40 repeats are essential for WDR81 interaction with covalent bound ATG5-ATG12. Reduction of WDR81 impairs the viability of mouse primary neurons, while overexpression of WDR81 restores the viability of fibroblasts from HD patients. Notably, in Caenorhabditis elegans, deletion of the WDR81 homolog (SORF-2) causes accumulation of p62 bodies and exacerbates neuron loss induced by overexpressed α-synuclein. As expected, overexpression of SORF-2 or human WDR81 restores neuron viability in worms. These results demonstrate that WDR81 has crucial evolutionarily conserved roles in autophagic clearance of protein aggregates and maintenance of cell viability under pathological conditions, and its reduction provides mechanistic insights into the pathogenesis of HD, PD, AD and brain disorders related to WDR81 mutations.
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Yang, Fan, Haoran Hu, Wenjing Yin, Guangyi Li, Ting Yuan, Xuetao Xie y Changqing Zhang. "Autophagy Is Independent of the Chondroprotection Induced by Platelet-Rich Plasma Releasate". BioMed Research International 2018 (24 de julio de 2018): 1–11. http://dx.doi.org/10.1155/2018/9726703.
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Background. Platelet-rich plasma (PRP) has been shown to be a promising therapeutic agent against osteoarthritis (OA), whereas its chondroprotection mechanism is not fully elucidated. Autophagy is considered an important biological process throughout the development of OA. Therefore, the objective of the present study is to investigate the role of autophagy in the chondroprotection and compare the effects of releasate between L-PRP and P-PRP. Methods. PRP were prepared from rat blood. Rat chondrocytes pretreated in the presence or absence of interleukin-1 beta (IL-1β) were incubated with PRP releasate. The expressions of OA-related genes and autophagy-related genes were determined by RT-PCR and western blot, respectively. Autophagic bodies were assessed by transmission electron microscopy and the autophagy flux was monitored under the confocal microscopy. The effect of PRP on autophagy was further investigated in the milieu of autophagy activator, rapamycin, or autophagy inhibition by downregulation of Atg5. The effect of PRP on cartilage repair and autophagy was also evaluated in an OA rat model. Results. In vitro, PRP releasate increased the expression of the anabolic genes, COL2 and Aggrecan, and decreased the expression of the catabolic genes, whereas the expression of autophage markers, Atg5 and Beclin-1, as well as the ratio of LC3 II/LC3 I, was not significantly altered in normal or IL-1β-treated chondrocytes. Similar expression pattern was found following the activation (rapamycin) or inhibition (Atg5 silencing) of autophagy. In vivo, PRP releasate ameliorated posttraumatic cartilage degeneration while the expression of LC3 was comparable to that in the vehicle treatment group. Conclusions. PRP releasate promoted the anabolic gene expression, relieved inflammatory stress in chondrocytes, and ameliorated cartilage degeneration, but autophagy was independent of these processes.
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Kovács, Attila L. "A Simple Method to Estimate the Number of Autophagic Elements by Electron Microscopic Morphometry in Real Cellular Dimensions". BioMed Research International 2014 (2014): 1–5. http://dx.doi.org/10.1155/2014/578698.
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Autophagic elements typically appear as spherical bodies. During their life they undergo a series of changes (e.g., fusion, degradation of content, and swelling) which influence their size in a way that may be characteristic for cell type, stage of maturation, or various experimentally manipulated parameters. A simple and time efficient method is suggested here to use exactly calculated specific surface values and estimate average diameter and number of autophagic elements in real cellular dimensions. The method is based on the easiest morphometric determination of relative surface (surface density) and volume (volume density) data by electron microscopy. A series of data from real experimental samples of liver and exocrine pancreatic cells are offered to illustrate the potential of these measurements and calculations.
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HALFERTY, L., J. F. O'NEILL, G. P. BRENNAN, J. KEISER y I. FAIRWEATHER. "Electron microscopical study to assess thein vitroeffects of the synthetic trioxolane OZ78 against the liver fluke,Fasciola hepatica". Parasitology 136, n.º 11 (7 de agosto de 2009): 1325–37. http://dx.doi.org/10.1017/s0031182009990643.
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SUMMARYAdultFasciola hepaticawere incubated for 48 hin vitroin the synthetic peroxide, OZ78 at a concentration of 100 μg/ml and then prepared for scanning and transmission electron microscopy. There was limited disruption to the external fluke surface, with only slight swelling and blebbing of the interspinal tegument in the midbody and ventral tail regions. By contrast, significant disruption was observed to the ultrastructure of the tegument and subtegumental tissues. There was severe swelling of the basal infolds in the tegumental syncytium and the flooding spread internally to affect the subtegumental tissues. In the tegumental system, there was swelling of the cisternae of granular endoplasmic reticulum and of the mitochondria, with the latter showing signs of breaking down. Autophagic vacuoles and lipid droplets were present and the synthesis of tegumental secretory bodies was much reduced. The gastrodermal cells were severely affected, with swelling and degeneration of the mitochondria and the presence of autophagic vacuoles and lipid droplets. The granular endoplasmic reticulum was swollen and vesiculated and the cells contained few secretory bodies. Both the vitelline and testis follicles showed evidence of extensive cellular disruption and degeneration. This study confirms previous data indicating the potential flukicidal activity of OZ78.
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Rost-Roszkowska, M. M., J. Vilimová, K. Tajovský, A. Chachulska-Żymełka, A. Sosinka, M. Kszuk-Jendrysik, A. Ostróżka y F. Kaszuba. "Autophagy and Apoptosis in the Midgut Epithelium of Millipedes". Microscopy and Microanalysis 25, n.º 4 (20 de mayo de 2019): 1004–16. http://dx.doi.org/10.1017/s143192761900059x.
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AbstractThe process of autophagy has been detected in the midgut epithelium of four millipede species: Julus scandinavius, Polyxenus lagurus, Archispirostreptus gigas, and Telodeinopus aoutii. It has been examined using transmission electron microscopy (TEM), which enabled differentiation of cells in the midgut epithelium, and some histochemical methods (light microscope and fluorescence microscope). While autophagy appeared in the cytoplasm of digestive, secretory, and regenerative cells in J. scandinavius and A. gigas, in the two other species, T. aoutii and P. lagurus, it was only detected in the digestive cells. Both types of macroautophagy, the selective and nonselective processes, are described using TEM. Phagophore formation appeared as the first step of autophagy. After its blind ends fusion, the autophagosomes were formed. The autophagosomes fused with lysosomes and were transformed into autolysosomes. As the final step of autophagy, the residual bodies were detected. Autophagic structures can be removed from the midgut epithelium via, e.g., atypical exocytosis. Additionally, in P. lagurus and J. scandinavius, it was observed as the neutralization of pathogens such as Rickettsia-like microorganisms. Autophagy and apoptosis ca be analyzed using TEM, while specific histochemical methods may confirm it.