• Title, Summary, Keyword: autophagy

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Electron-Microscope Contributions to Autophagy Research and the Nobel Prize in Physiology or Medicine 2016

  • Rhyu, Im Joo
    • Applied Microscopy
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    • v.47 no.1
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    • pp.1-2
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    • 2017
  • Professor Yoshinori Ohsumi received the 2016 Nobel Prize in Physiology or Medicine for his contribution to autophagy research, which was first studied using electron microscopy. To celebrate and commemorate this historical moment, I describe the role of electron microscopy in autophagy research and suggest a role for next-generation electron microscopy in this research field.

Role of Autophagy in the Control of Cell Death and Inflammation

  • Lee, Myung-Shik
    • IMMUNE NETWORK
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    • v.9 no.1
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    • pp.8-11
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    • 2009
  • There is mounting evidence that autophagy is involved in diverse physiological and pathological processes that have immense relevance in human development, diseases and aging. Immunity and inflammation are not exceptions. Here, the role of autophagy in the control of immune processes particularly that related to cell death and inflammation is discussed.

Rapamycin Influences the Efficiency of In vitro Fertilization and Development in the Mouse: A Role for Autophagic Activation

  • Lee, Geun-Kyung;Shin, Hyejin;Lim, Hyunjung Jade
    • Asian-Australasian Journal of Animal Sciences
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    • v.29 no.8
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    • pp.1102-1110
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    • 2016
  • The mammalian target of rapamycin (mTOR) regulates cellular processes such as cell growth, metabolism, transcription, translation, and autophagy. Rapamycin is a selective inhibitor of mTOR, and induces autophagy in various systems. Autophagy contributes to clearance and recycling of macromolecules and organelles in response to stress. We previously reported that vitrified-warmed mouse oocytes show acute increases in autophagy during warming, and suggested that it is a natural response to cold stress. In this follow-up study, we examined whether the modulation of autophagy influences survival, fertilization, and developmental rates of vitrified-warmed mouse oocytes. We used rapamycin to enhance autophagy in metaphase II (MII) oocytes before and after vitrification. The oocytes were then subjected to in vitro fertilization (IVF). The fertilization and developmental rates of vitrified-warmed oocytes after rapamycin treatment were significantly lower than those for control groups. Modulation of autophagy with rapamycin treatment shows that rapamycin-induced autophagy exerts a negative influence on fertilization and development of vitrified-warmed oocytes.

Emerging Paradigm of Crosstalk between Autophagy and the Ubiquitin-Proteasome System

  • Nam, Taewook;Han, Jong Hyun;Devkota, Sushil;Lee, Han-Woong
    • Molecules and Cells
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    • v.40 no.12
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    • pp.897-905
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    • 2017
  • Cellular protein homeostasis is maintained by two major degradation pathways, namely the ubiquitin-proteasome system (UPS) and autophagy. Until recently, the UPS and autophagy were considered to be largely independent systems targeting proteins for degradation in the proteasome and lysosome, respectively. However, the identification of crucial roles of molecular players such as ubiquitin and p62 in both of these pathways as well as the observation that blocking the UPS affects autophagy flux and vice versa has generated interest in studying crosstalk between these pathways. Here, we critically review the current understanding of how the UPS and autophagy execute coordinated protein degradation at the molecular level, and shed light on our recent findings indicating an important role of an autophagy-associated transmembrane protein EI24 as a bridging molecule between the UPS and autophagy that functions by regulating the degradation of several E3 ligases with Really Interesting New Gene (RING)-domains.

The Roles of the SNARE Protein Sed5 in Autophagy in Saccharomyces cerevisiae

  • Zou, Shenshen;Sun, Dan;Liang, Yongheng
    • Molecules and Cells
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    • v.40 no.9
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    • pp.643-654
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    • 2017
  • Autophagy is a degradation pathway in eukaryotic cells in which aging proteins and organelles are sequestered into double-membrane vesicles, termed autophagosomes, which fuse with vacuoles to hydrolyze cargo. The key step in autophagy is the formation of autophagosomes, which requires different kinds of vesicles, including COPII vesicles and Atg9-containing vesicles, to transport lipid double-membranes to the phagophore assembly site (PAS). In yeast, the cis-Golgi localized t-SNARE protein Sed5 plays a role in endoplasmic reticulum (ER)-Golgi and intra-Golgi vesicular transport. We report that during autophagy, sed5-1 mutant cells could not properly transport Atg8 to the PAS, resulting in multiple Atg8 dots being dispersed into the cytoplasm. Some dots were trapped in the Golgi apparatus. Sed5 regulates the anterograde trafficking of Atg9-containing vesicles to the PAS by participating in the localization of Atg23 and Atg27 to the Golgi apparatus. Furthermore, we found that overexpression of SFT1 or SFT2 (suppressor of sed5 ts) rescued the autophagy defects in sed5-1 mutant cells. Our data suggest that Sed5 plays a novel role in autophagy, by regulating the formation of Atg9-containing vesicles in the Golgi apparatus, and the genetic interaction between Sft1/2 and Sed5 is essential for autophagy.

Proliferation of Toxoplasma gondii Suppresses Host Cell Autophagy

  • Lee, Youn-Jin;Song, Hyun-Ouk;Lee, Young-Ha;Ryu, Jae-Sook;Ahn, Myoung-Hee
    • The Korean Journal of Parasitology
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    • v.51 no.3
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    • pp.279-287
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    • 2013
  • Autophagy is a process of cytoplasmic degradation of endogenous proteins and organelles. Although its primary role is protective, it can also contribute to cell death. Recently, autophagy was found to play a role in the activation of host defense against intracellular pathogens. The aims of our study was to investigate whether host cell autophagy influences Toxoplasma gondii proliferation and whether autophagy inhibitors modulate cell survival. HeLa cells were infected with T. gondii with and without rapamycin treatment to induce autophagy. Lactate dehydrogenase assays showed that cell death was extensive at 36-48 hr after infection in cells treated with T. gondii with or without rapamycin. The autophagic markers, LC3 II and Beclin 1, were strongly expressed at 18-24 hr after exposure as shown by Western blotting and RT-PCR. However, the subsequent T. gondii proliferation suppressed autophagy at 36 hr post-infection. Pre-treatment with the autophagy inhibitor, 3-methyladenine (3-MA), down-regulated LC3 II and Beclin 1. The latter was also down-regulated by calpeptin, a calpain inhibitor. Monodansyl cadaverine (MDC) staining detected numerous autophagic vacuoles (AVs) at 18 hr post-infection. Ultrastructural observations showed T. gondii proliferation in parasitophorous vacuoles (PVs) coinciding with a decline in the numbers of AVs by 18 hr. FACS analysis failed to confirm the presence of cell apoptosis after exposure to T. gondii and rapamycin. We concluded that T. gondii proliferation may inhibit host cell autophagy and has an impact on cell survival.

Activation of Autophagy Pathway Suppresses the Expression of iNOS, IL6 and Cell Death of LPS-Stimulated Microglia Cells

  • Han, Hye-Eun;Kim, Tae-Kyung;Son, Hyung-Jin;Park, Woo Jin;Han, Pyung-Lim
    • Biomolecules & Therapeutics
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    • v.21 no.1
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    • pp.21-28
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    • 2013
  • Microglia play a role in maintaining and resolving brain tissue homeostasis. In pathological conditions, microglia release pro-inflammatory cytokines and cytotoxic factors, which aggravate the progression of neurodegenerative diseases. Autophagy pathway might be involved in the production of pro-inflammatory cytokines and cytotoxic factors in microglia, though details of the mechanism remain largely unknown. In the present study, we examined the role of the autophagy pathway in activated BV2 microglia cells. In BV2 cells, rapamycin treatment activated the formation of anti-LC3-labeled autophagosomes, whereas the ATG5 depletion using siRNA-ATG5 prevented the formation of LC3-labeled autophagosomes, indicating that BV2 cells exhibit an active classical autophagy system. When treated with LPS, BV2 cells expressed an increase of anti-LC3-labeled dots. The levels of LC3-labeled dots were not suppressed, instead tended to be enhanced, by the inhibition of the autophagy pathway with siRNA-ATG5 or wortmannin, suggesting that LPS-induced LC3-labeled dots in nature were distinct from the typical autophagosomes. The levels of LPS-induced expression of iNOS and IL6 were suppressed by treatment with rapamycin, and conversely, their expressions were enhanced by siRNA-ATG5 treatment. Moreover, the activation of the autophagy pathway using rapamycin inhibited cell death of LPS-stimulated microglia. These results suggest that although microglia possess a typical autophagy pathway, the glial cells express a non-typical autophagy pathway in response to LPS, and the activation of the autophagy pathway suppresses the expression of iNOS and IL6, and the cell death of LPS-stimulated microglia.

Chracterization of THP-1 Cell Death Induced by Porphyromonas gingivalis Infection

  • Song, YuRi;Kim, SeYeon;Park, Mee Hee;Na, Hee Sam;Chung, Jin
    • International Journal of Oral Biology
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    • v.42 no.1
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    • pp.17-23
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    • 2017
  • Background: Periodontitis is generally a chronic disorder characterized by the breakdown of tooth-supporting tissues. P. gingivalis, a Gram-negative anaerobic rod, is one of the major pathogens associated with periodontitis. Frequently, P. gingivalis infection leads to cell death. However, the correlation between P. gingivalis-induced cell death and periodontal inflammation remains to be elucidated. Among cell deaths, the death of immune cells appears to play a significant role in inflammatory response. Thus, the aim of this study was to examine P. gingivalis-induced cell death, focusing on autophagy and apoptosis in THP-1 cells. Methods: Human acute monocytic leukemia cell line (THP-1) was used for all experiments. Autophagy induced by P. gingivalis in THP-1 cells was examined by Cyto ID staining. Intracellular autophagic vacuoles were observed by fluorescence microscopy using staining Acridine orange (AO); and 3-methyladenine (3-MA) was used to inhibit autophagy. Total cell death was measured by LDH assay. Cytokine production was measured by an ELISA method. Results: P. gingivalis induced autophagy in an MOI-dependent manner in THP-1 cells, but 3-MA treatment decreased autophagy and increased the apoptotic blebs. P. gingivalis infection did not increase apoptosis compared to the control cells, whereas inhibition of autophagy by 3-MA significantly increased apoptosis in P. gingivalis-infected THP-1 cells. Inhibition of autophagy by 3-MA also increased total cell deaths and inflammatory cytokine production, including $IL-1{\beta}$ and $TNF-{\alpha}$. Conclusion: P. gingivalis induced autophagy in THP-1 cells, but the inhibition of autophagy by 3-MA stimulated apoptosis, leading to increased cell deaths and pro-inflammatory cytokines production. Hence, the modulation of cell deaths may provide a mechanism to fight against invading microorganisms in host cells and could be a promising way to control inflammation.

The Effect of Brunfelsia grandiflora Ethanol Extract on the Induction of Autophagy in Human Lung Fibroblasts (사람 폐 섬유아 세포에서 Brunfelsia grandiflora 에탄올 추출물이 Autophagy에 미치는 영향)

  • Nam, Hyang;Kim, Moon-Moo
    • Journal of Life Science
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    • v.24 no.8
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    • pp.837-842
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    • 2014
  • The purpose of this study was to investigate the effect of Brunfelsia grandiflora ethanol extract (BGEE) on the induction of autophagy via regulation of SIRT1 expression and p53 activation in a human lung fibroblast cell line, IMR 90. BGEE at a concentration of $5{\mu}g/ml$ or more exhibited a cytotoxic effect on IMR 90 cells. For the first time, this study showed that BGEE induces autophagy in normal human lung fibroblasts. BGEE also increased the expression level of beclin-1 at $2.5{\mu}g/ml$ or less and Atg7 at $5{\mu}g/ml$, both of which are known to be involved in the induction of autophagy. In addition, BGEE modulated the expression of other proteins related to autophagy in normal human lung fibroblasts. The expression levels of p53 and p-p53, an active form of p53, were decreased in the presence of BGEE at a noncytotoxic concentration. In contrast, the expression level of SIRT1 was increased in human lung fibroblasts treated with BGEE at a noncytotoxic concentration. Moreover, SA-${\beta}$-Gal staining, an aging marker, was reduced in the normal human lung fibroblasts treated with BGEE. These findings suggest that BGEE promotes the induction of autophagy and antiaging through the modulation of p53 and SIRT1 in human lung fibroblasts.

Dexamethasone Interferes with Autophagy and Affects Cell Survival in Irradiated Malignant Glioma Cells

  • Komakech, Alfred;Im, Ji-Hye;Gwak, Ho-Shin;Lee, Kyue-Yim;Kim, Jong Heon;Yoo, Byong Chul;Cheong, Heesun;Park, Jong Bae;Kwon, Ji Woong;Shin, Sang Hoon;Yoo, Heon
    • Journal of Korean Neurosurgical Society
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    • v.63 no.5
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    • pp.566-578
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    • 2020
  • Objective : Radiation is known to induce autophagy in malignant glioma cells whether it is cytocidal or cytoprotective. Dexamethasone is frequently used to reduce tumor-associated brain edema, especially during radiation therapy. The purpose of the study was to determine whether and how dexamethasone affects autophagy in irradiated malignant glioma cells and to identify possible intervening molecular pathways. Methods : We prepared p53 mutant U373 and LN229 glioma cell lines, which varied by phosphatase and tensin homolog (PTEN) mutational status and were used to make U373 stable transfected cells expressing GFP-LC3 protein. After performing cell survival assay after irradiation, the IC50 radiation dose was determined. Dexamethasone dose (10 μM) was determined from the literature and added to the glioma cells 24 hours before the irradiation. The effect of adding dexamethasone was evaluated by cell survival assay or clonogenic assay and cell cycle analysis. Measurement of autophagy was visualized by western blot of LC3-I/LC3-II and quantified by the GFP-LC3 punctuated pattern under fluorescence microscopy and acridine orange staining for acidic vesicle organelles by flow cytometry. Results : Dexamethasone increased cell survival in both U373 and LN229 cells after irradiation. It interfered with autophagy after irradiation differently depending on the PTEN mutational status : the autophagy decreased in U373 (PTEN-mutated) cells but increased in LN229 (PTEN wild-type) cells. Inhibition of protein kinase B (AKT) phosphorylation after irradiation by LY294002 reversed the dexamethasone-induced decrease of autophagy and cell death in U373 cells but provoked no effect on both autophagy and cell survival in LN229 cells. After ATG5 knockdown, radiation-induced autophagy decreased and the effect of dexamethasone also diminished in both cell lines. The diminished autophagy resulted in a partial reversal of dexamethasone protection from cell death after irradiation in U373 cells; however, no significant change was observed in surviving fraction LN229 cells. Conclusion : Dexamethasone increased cell survival in p53 mutated malignant glioma cells and increased autophagy in PTEN-mutant malignant glioma cell but not in PTEN-wildtype cell. The difference of autophagy response could be mediated though the phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin signaling pathway.