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Wallings R, Connor-Robson N, Wade-Martins R. LRRK2 interacts with the vacuolar-type H+-ATPase pump a1 subunit to regulate lysosomal function. Hum Mol Genet 2020; 28:2696-2710. [PMID: 31039583 PMCID: PMC6687951 DOI: 10.1093/hmg/ddz088] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 02/20/2019] [Accepted: 04/15/2019] [Indexed: 12/11/2022] Open
Abstract
Lysosomal dysfunction lies at the centre of the cellular mechanisms underlying Parkinson’s disease although the precise underlying mechanisms remain unknown. We investigated the role of leucine-rich repeat kinase 2 (LRRK2) on lysosome biology and the autophagy pathway in primary neurons expressing the human LRRK2-G2019S or LRKK2-R1441C mutant or the human wild-type (hWT-LRRK2) genomic locus. The expression of LRRK2-G2019S or hWT-LRRK2 inhibited autophagosome production, whereas LRRK2-R1441C induced a decrease in autophagosome/lysosome fusion and increased lysosomal pH. In vivo data from the cortex and substantia nigra pars compacta of aged LRRK2 transgenic animals revealed alterations in autophagosome puncta number reflecting those phenotypes seen in vitro. Using the two selective and potent LRRK2 kinase inhibitors, MLi-2 and PF-06447475, we demonstrated that the LRRK2-R1441C-mediated decrease in autolysosome maturation is not dependent on LRRK2 kinase activity. We showed that hWT-LRRK2 and LRRK2-G2019S bind to the a1 subunit of vATPase, which is abolished by the LRRK2-R1441C mutation, leading to a decrease in a1 protein and cellular mislocalization. Modulation of lysosomal zinc increased vATPase a1 protein levels and rescued the LRRK2-R1441C-mediated cellular phenotypes. Our work defines a novel interaction between the LRRK2 protein and the vATPase a1 subunit and demonstrates a mode of action by which drugs may rescue lysosomal dysfunction. These results demonstrate the importance of LRRK2 in lysosomal biology, as well as the critical role of the lysosome in PD.
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Affiliation(s)
- Rebecca Wallings
- Oxford Parkinson's Disease Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
| | - Natalie Connor-Robson
- Oxford Parkinson's Disease Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
| | - Richard Wade-Martins
- Oxford Parkinson's Disease Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
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2
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Sánchez-Martín P, Sou YS, Kageyama S, Koike M, Waguri S, Komatsu M. NBR1-mediated p62-liquid droplets enhance the Keap1-Nrf2 system. EMBO Rep 2020; 21:e48902. [PMID: 31916398 DOI: 10.15252/embr.201948902] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 12/09/2019] [Accepted: 12/10/2019] [Indexed: 01/25/2023] Open
Abstract
p62/SQSTM1 is a multivalent protein that has the ability to cause liquid-liquid phase separation and serves as a receptor protein that participates in cargo isolation during selective autophagy. This protein is also involved in the non-canonical activation of the Keap1-Nrf2 system, a major oxidative stress response pathway. Here, we show a role of neighbor of BRCA1 gene 1 (NBR1), an autophagy receptor structurally similar to p62/SQSTM1, in p62-liquid droplet formation and Keap1-Nrf2 pathway activation. Overexpression of NBR1 blocks selective degradation of p62/SQSTM1 through autophagy and promotes the accumulation and phosphorylation of p62/SQSTM1 in liquid-like bodies, which is required for the activation of Nrf2. NBR1 is induced in response to oxidative stress, which triggers p62-mediated Nrf2 activation. Conversely, loss of Nbr1 suppresses not only the formation of p62/SQSTM1-liquid droplets, but also of p62-dependent Nrf2 activation during oxidative stress. Taken together, our results show that NBR1 mediates p62/SQSTM1-liquid droplet formation to activate the Keap1-Nrf2 pathway.
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Affiliation(s)
- Pablo Sánchez-Martín
- Department of Physiology, Juntendo University Graduate School of Medicine, Bunkyo-ku, Japan
| | - Yu-Shin Sou
- Department of Cell Biology and Neuroscience, Juntendo University Graduate School of Medicine, Bunkyo-ku, Japan
| | - Shun Kageyama
- Department of Physiology, Juntendo University Graduate School of Medicine, Bunkyo-ku, Japan
| | - Masato Koike
- Department of Cell Biology and Neuroscience, Juntendo University Graduate School of Medicine, Bunkyo-ku, Japan
| | - Satoshi Waguri
- Department of Anatomy and Histology, Fukushima Medical University School of Medicine, Fukushima, Japan
| | - Masaaki Komatsu
- Department of Physiology, Juntendo University Graduate School of Medicine, Bunkyo-ku, Japan
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3
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Keane H, Ryan BJ, Jackson B, Whitmore A, Wade-Martins R. Protein-protein interaction networks identify targets which rescue the MPP+ cellular model of Parkinson's disease. Sci Rep 2015; 5:17004. [PMID: 26608097 PMCID: PMC4660280 DOI: 10.1038/srep17004] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 10/12/2015] [Indexed: 01/08/2023] Open
Abstract
Neurodegenerative diseases are complex multifactorial disorders characterised by the interplay of many dysregulated physiological processes. As an exemplar, Parkinson’s disease (PD) involves multiple perturbed cellular functions, including mitochondrial dysfunction and autophagic dysregulation in preferentially-sensitive dopamine neurons, a selective pathophysiology recapitulated in vitro using the neurotoxin MPP+. Here we explore a network science approach for the selection of therapeutic protein targets in the cellular MPP+ model. We hypothesised that analysis of protein-protein interaction networks modelling MPP+ toxicity could identify proteins critical for mediating MPP+ toxicity. Analysis of protein-protein interaction networks constructed to model the interplay of mitochondrial dysfunction and autophagic dysregulation (key aspects of MPP+ toxicity) enabled us to identify four proteins predicted to be key for MPP+ toxicity (P62, GABARAP, GBRL1 and GBRL2). Combined, but not individual, knockdown of these proteins increased cellular susceptibility to MPP+ toxicity. Conversely, combined, but not individual, over-expression of the network targets provided rescue of MPP+ toxicity associated with the formation of autophagosome-like structures. We also found that modulation of two distinct proteins in the protein-protein interaction network was necessary and sufficient to mitigate neurotoxicity. Together, these findings validate our network science approach to multi-target identification in complex neurological diseases.
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Affiliation(s)
- Harriet Keane
- Oxford Parkinson's Disease Centre, Anatomy and Genetics, University of Oxford, OX1 3QX.,Department of Physiology, Anatomy and Genetics, University of Oxford, OX1 3QX
| | - Brent J Ryan
- Oxford Parkinson's Disease Centre, Anatomy and Genetics, University of Oxford, OX1 3QX.,Department of Physiology, Anatomy and Genetics, University of Oxford, OX1 3QX
| | | | - Alan Whitmore
- e-Therapeutics plc, Long Hanborough, OX29 8LN.,Oxford Parkinson's Disease Centre and Networks Cluster, Keble College, Oxford, OX1 3PG
| | - Richard Wade-Martins
- Oxford Parkinson's Disease Centre, Anatomy and Genetics, University of Oxford, OX1 3QX.,Department of Physiology, Anatomy and Genetics, University of Oxford, OX1 3QX
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4
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McKnight NC, Zhong Y, Wold MS, Gong S, Phillips GR, Dou Z, Zhao Y, Heintz N, Zong WX, Yue Z. Beclin 1 is required for neuron viability and regulates endosome pathways via the UVRAG-VPS34 complex. PLoS Genet 2014; 10:e1004626. [PMID: 25275521 PMCID: PMC4183436 DOI: 10.1371/journal.pgen.1004626] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Accepted: 07/25/2014] [Indexed: 01/24/2023] Open
Abstract
Deficiency of autophagy protein beclin 1 is implicated in tumorigenesis and neurodegenerative diseases, but the molecular mechanism remains elusive. Previous studies showed that Beclin 1 coordinates the assembly of multiple VPS34 complexes whose distinct phosphatidylinositol 3-kinase III (PI3K-III) lipid kinase activities regulate autophagy at different steps. Recent evidence suggests a function of beclin 1 in regulating multiple VPS34-mediated trafficking pathways beyond autophagy; however, the precise role of beclin 1 in autophagy-independent cellular functions remains poorly understood. Herein we report that beclin 1 regulates endocytosis, in addition to autophagy, and is required for neuron viability in vivo. We find that neuronal beclin 1 associates with endosomes and regulates EEA1/early endosome localization and late endosome formation. Beclin 1 maintains proper cellular phosphatidylinositol 3-phosphate (PI(3)P) distribution and total levels, and loss of beclin 1 causes a disruption of active Rab5 GTPase-associated endosome formation and impairment of endosome maturation, likely due to a failure of Rab5 to recruit VPS34. Furthermore, we find that Beclin 1 deficiency causes complete loss of the UVRAG-VPS34 complex and associated lipid kinase activity. Interestingly, beclin 1 deficiency impairs p40phox-linked endosome formation, which is rescued by overexpressed UVRAG or beclin 1, but not by a coiled-coil domain-truncated beclin 1 (a UVRAG-binding mutant), Atg14L or RUBICON. Thus, our study reveals the essential role for beclin 1 in neuron survival involving multiple membrane trafficking pathways including endocytosis and autophagy, and suggests that the UVRAG-beclin 1 interaction underlies beclin 1's function in endocytosis.
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Affiliation(s)
- Nicole C. McKnight
- Department of Neurology and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Yun Zhong
- Department of Neurology and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Mitchell S. Wold
- Department of Neurology and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Shiaoching Gong
- Laboratory of Molecular Biology, Howard Hughes Medical Institute, Rockefeller University, New York, New York, United States of America
| | - Greg R. Phillips
- Department of Neurology and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Zhixun Dou
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Yanxiang Zhao
- Department of Applied Biology and Chemical Technology, State Key Laboratory of Chirosciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Nathaniel Heintz
- Laboratory of Molecular Biology, Howard Hughes Medical Institute, Rockefeller University, New York, New York, United States of America
| | - Wei-Xing Zong
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Zhenyu Yue
- Department of Neurology and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
- * E-mail:
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5
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Maruyama Y, Sou YS, Kageyama S, Takahashi T, Ueno T, Tanaka K, Komatsu M, Ichimura Y. LC3B is indispensable for selective autophagy of p62 but not basal autophagy. Biochem Biophys Res Commun 2014; 446:309-15. [PMID: 24582747 DOI: 10.1016/j.bbrc.2014.02.093] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Accepted: 02/23/2014] [Indexed: 11/19/2022]
Abstract
Autophagy is a unique intracellular protein degradation system accompanied by autophagosome formation. Besides its important role through bulk degradation in supplying nutrients, this system has an ability to degrade certain proteins, organelles, and invading bacteria selectively to maintain cellular homeostasis. In yeasts, Atg8p plays key roles in both autophagosome formation and selective autophagy based on its membrane fusion property and interaction with autophagy adaptors/specific substrates. In contrast to the single Atg8p in yeast, mammals have 6 homologs of Atg8p comprising LC3 and GABARAP families. However, it is not clear these two families have different or similar functions. The aim of this study was to determine the separate roles of LC3 and GABARAP families in basal/constitutive and/or selective autophagy. While the combined knockdown of LC3 and GABARAP families caused a defect in long-lived protein degradation through lysosomes, knockdown of each had no effect on the degradation. Meanwhile, knockdown of LC3B but not GABARAPs resulted in significant accumulation of p62/Sqstm1, one of the selective substrate for autophagy. Our results suggest that while mammalian Atg8 homologs are functionally redundant with regard to autophagosome formation, selective autophagy is regulated by specific Atg8 homologs.
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Affiliation(s)
- Yoko Maruyama
- Protein Metabolism Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan; Department of Pediatrics, School of Medicine, Keio University, Tokyo 160-8582, Japan
| | - Yu-Shin Sou
- Protein Metabolism Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan
| | - Shun Kageyama
- Protein Metabolism Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan
| | - Takao Takahashi
- Department of Pediatrics, School of Medicine, Keio University, Tokyo 160-8582, Japan
| | - Takashi Ueno
- Division of Proteomics and Biomolecular Science, Center for Biomedical Research Resources, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan
| | - Keiji Tanaka
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan
| | - Masaaki Komatsu
- Protein Metabolism Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan; Department of Biochemistry, School of Medicine, Niigata University, Niigata 951-8510, Japan.
| | - Yoshinobu Ichimura
- Protein Metabolism Project, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan.
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6
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Oxidative stress enhances neurodegeneration markers induced by herpes simplex virus type 1 infection in human neuroblastoma cells. PLoS One 2013; 8:e75842. [PMID: 24124518 PMCID: PMC3790872 DOI: 10.1371/journal.pone.0075842] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 08/21/2013] [Indexed: 01/05/2023] Open
Abstract
Mounting evidence suggests that Herpes simplex virus type 1 (HSV-1) is involved in the pathogenesis of Alzheimer's disease (AD). Previous work from our laboratory has shown HSV-1 infection to induce the most important pathological hallmarks of AD brains. Oxidative damage is one of the earliest events of AD and is thought to play a crucial role in the onset and development of the disease. Indeed, many studies show the biomarkers of oxidative stress to be elevated in AD brains. In the present work the combined effects of HSV-1 infection and oxidative stress on Aβ levels and autophagy (neurodegeneration markers characteristic of AD) were investigated. Oxidative stress significantly potentiated the accumulation of intracellular Aβ mediated by HSV-1 infection, and further inhibited its secretion to the extracellular medium. It also triggered the accumulation of autophagic compartments without increasing the degradation of long-lived proteins, and enhanced the inhibition of the autophagic flux induced by HSV-1. These effects of oxidative stress were not due to enhanced virus replication. Together, these results suggest that HSV-1 infection and oxidative damage interact to promote the neurodegeneration events seen in AD.
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7
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Inami Y, Yamashina S, Izumi K, Ueno T, Tanida I, Ikejima K, Watanabe S. Hepatic steatosis inhibits autophagic proteolysis via impairment of autophagosomal acidification and cathepsin expression. Biochem Biophys Res Commun 2011; 412:618-25. [PMID: 21856284 DOI: 10.1016/j.bbrc.2011.08.012] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 08/04/2011] [Indexed: 12/31/2022]
Abstract
Autophagy, one of protein degradation system, contributes to maintain cellular homeostasis and cell defense. Recently, some evidences indicated that autophagy and lipid metabolism are interrelated. Here, we demonstrate that hepatic steatosis impairs autophagic proteolysis. Though accumulation of autophagosome is observed in hepatocytes from ob/ob mice, expression of p62 was augmented in liver from ob/ob mice more than control mice. Moreover, degradation of the long-lived protein leucine was significantly suppressed in hepatocytes isolated from ob/ob mice. More than 80% of autophagosomes were stained by LysoTracker Red (LTR) in hepatocytes from control mice; however, rate of LTR-stained autophagosomes in hepatocytes were suppressed in ob/ob mice. On the other hand, clearance of autolysosomes loaded with LTR was blunted in hepatocytes from ob/ob mice. Although fusion of isolated autophagosome and lysosome was not disturbed, proteinase activity of cathepsin B and L in autolysosomes and cathepsin B and L expression of liver were suppressed in ob/ob mice. These results indicate that lipid accumulation blunts autophagic proteolysis via impairment of autophagosomal acidification and cathepsin expression.
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Affiliation(s)
- Yoshihiro Inami
- Department of Gastroenterology, Juntendo University School of Medicine, Tokyo, Japan
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8
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Upregulation of human autophagy-initiation kinase ULK1 by tumor suppressor p53 contributes to DNA-damage-induced cell death. Cell Death Differ 2011; 18:1598-607. [PMID: 21475306 PMCID: PMC3172118 DOI: 10.1038/cdd.2011.33] [Citation(s) in RCA: 144] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In yeast, activation of ATG1/ATG13 kinase complex initiates autophagy. This mechanism of autophagy initiation is conserved, as unc-51-like kinase 1 (ULK1) and unc-51-like kinase 2 (ULK2) are two mammalian functional homologues of ATG1 and form similar complex with mammalian ATG13. Here, we report that both ULK1 and ULK2 are transcriptional targets of tumor suppressor p53. In response to DNA damage, ULK1 and ULK2 are upregulated by p53. The upregulation of ULK1 (ULK2)/ATG13 complex by p53 is necessary for the sustained autophagy activity induced by DNA damage. In this context, elevated autophagy contributes to subsequent cell death. These findings suggest that ULK1 and ULK2 may mediate part of tumor suppression activity in mammalian cells and contribute to the efficacy of genotoxic chemotherapeutic drugs.
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9
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Nutrient starvation elicits an acute autophagic response mediated by Ulk1 dephosphorylation and its subsequent dissociation from AMPK. Proc Natl Acad Sci U S A 2011; 108:4788-93. [PMID: 21383122 DOI: 10.1073/pnas.1100844108] [Citation(s) in RCA: 410] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Macroautophagy (herein referred to as autophagy) is an evolutionarily conserved self-digestive process cells adapt to starvation and other stress responses. Upon starvation, autophagy is induced, providing cells with needed nutrient supplies. We report here that Unc-51-like kinase 1 (Ulk1), a key initiator for mammalian autophagy, undergoes dramatic dephosphorylation upon starvation, particularly at serine 638 and serine 758. Phosphorylations of Ulk1 are mediated by mammalian target-of-rapamycin (mTOR) kinase and adenosine monophosphate activated protein kinase (AMPK). AMPK interacts with Ulk1 in a nutrient-dependent manner. Proper phosphorylations on Ulk1 are crucial for Ulk1/AMPK association, as a single serine-to-alanine mutation (S758A) at Ulk1 impairs this interaction. Compared to the wild-type ULK1, this Ulk1-S758A mutant initiates starvation-induced autophagy faster at an early time point, but does not alter the maximum capacity of autophagy when starvation prolongs. This study therefore revealed previously unnoticed acute autophagy response to environmental changes.
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10
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Jiang H, Martin V, Gomez-Manzano C, Johnson DG, Alonso M, White E, Xu J, McDonnell TJ, Shinojima N, Fueyo J. The RB-E2F1 pathway regulates autophagy. Cancer Res 2010; 70:7882-93. [PMID: 20807803 DOI: 10.1158/0008-5472.can-10-1604] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Autophagy is a protective mechanism that renders cells viable in stressful conditions. Emerging evidence suggests that this cellular process is also a tumor suppressor pathway. Previous studies showed that cyclin-dependent kinase inhibitors (CDKI) induce autophagy. Whether retinoblastoma protein (RB), a key tumor suppressor and downstream target of CDKIs, induces autophagy is not clear. Here, we show that RB triggers autophagy and that the RB activators p16INK4a and p27/kip1 induce autophagy in an RB-dependent manner. RB binding to E2 transcription factor (E2F) is required for autophagy induction and E2F1 antagonizes RB-induced autophagy, leading to apoptosis. Downregulation of E2F1 in cells results in high levels of autophagy. Our findings indicate that RB induces autophagy by repressing E2F1 activity. We speculate that this newly discovered aspect of RB function is relevant to cancer development and therapy.
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Affiliation(s)
- Hong Jiang
- Brain Tumor Center, Departments of Carcinogenesis, and Hematopathology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
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11
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Mizui T, Yamashina S, Tanida I, Takei Y, Ueno T, Sakamoto N, Ikejima K, Kitamura T, Enomoto N, Sakai T, Kominami E, Watanabe S. Inhibition of hepatitis C virus replication by chloroquine targeting virus-associated autophagy. J Gastroenterol 2010; 45:195-203. [PMID: 19760134 PMCID: PMC7088329 DOI: 10.1007/s00535-009-0132-9] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2009] [Accepted: 08/22/2009] [Indexed: 02/04/2023]
Abstract
BACKGROUND Autophagy has been reported to play a pivotal role on the replication of various RNA viruses. In this study, we investigated the role of autophagy on hepatitis C virus (HCV) RNA replication and demonstrated anti-HCV effects of an autophagic proteolysis inhibitor, chloroquine. METHODS Induction of autophagy was evaluated following the transfection of HCV replicon to Huh-7 cells. Next, we investigated the replication of HCV subgenomic replicon in response to treatment with lysosomal protease inhibitors or pharmacological autophagy inhibitor. The effect on HCV replication was analyzed after transfection with siRNA of ATG5, ATG7 and light-chain (LC)-3 to replicon cells. The antiviral effect of chloroquine and/or interferon-alpha (IFNalpha) was evaluated. RESULTS The transfection of HCV replicon increased the number of autophagosomes to about twofold over untransfected cells. Pharmacological inhibition of autophagic proteolysis significantly suppressed expression level of HCV replicon. Silencing of autophagy-related genes by siRNA transfection significantly blunted the replication of HCV replicon. Treatment of replicon cells with chloroquine suppressed the replication of the HCV replicon in a dose-dependent manner. Furthermore, combination treatment of chloroquine to IFNalpha enhanced the antiviral effect of IFNalpha and prevented re-propagation of HCV replicon. Protein kinase R was activated in cells treated with IFNalpha but not with chloroquine. Incubation with chloroquine decreased degradation of long-lived protein leucine. CONCLUSION The results of this study suggest that the replication of HCV replicon utilizes machinery involving cellular autophagic proteolysis. The therapy targeted to autophagic proteolysis by using chloroquine may provide a new therapeutic option against chronic hepatitis C.
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Affiliation(s)
- Tomokazu Mizui
- grid.258269.20000000417622738Department of Gastroenterology, Juntendo University, School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421 Japan
| | - Shunhei Yamashina
- grid.258269.20000000417622738Department of Gastroenterology, Juntendo University, School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421 Japan
| | - Isei Tanida
- grid.410795.e0000000122201880Department of Biochemistry and Cell Biology, Laboratory of Biomembranes, National Institute of Infectious Disease, Toyama 1-23-1, Shinjuku-ku, Tokyo, 162-8640 Japan
| | - Yoshiyuki Takei
- grid.260026.0000000040372555XDepartment of Gastroenterology, Mie University, Kurimamachiya-cho 1577, Tsu, Mie 514-8507 Japan
| | - Takashi Ueno
- grid.258269.20000000417622738Department of Biochemistry, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421 Japan
| | - Naoya Sakamoto
- grid.265073.50000000110149130Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo, 113-8510 Japan
| | - Kenichi Ikejima
- grid.258269.20000000417622738Department of Gastroenterology, Juntendo University, School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421 Japan
| | - Tsuneo Kitamura
- grid.258269.20000000417622738Department of Gastroenterology, Juntendo University, School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421 Japan
| | - Nobuyuki Enomoto
- grid.267500.60000000102913581First Department of Internal Medicine, University of Yamanashi, Kakedo 4-3-11, Kofu-shi, Yamanashi, 400-8511 Japan
| | - Tatsuo Sakai
- grid.258269.20000000417622738Department of Anatomy, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421 Japan
| | - Eiki Kominami
- grid.258269.20000000417622738Department of Biochemistry, Juntendo University School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421 Japan
| | - Sumio Watanabe
- grid.258269.20000000417622738Department of Gastroenterology, Juntendo University, School of Medicine, Hongo 2-1-1, Bunkyo-ku, Tokyo, 113-8421 Japan
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12
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Razi M, Chan EYW, Tooze SA. Early endosomes and endosomal coatomer are required for autophagy. ACTA ACUST UNITED AC 2009; 185:305-21. [PMID: 19364919 PMCID: PMC2700373 DOI: 10.1083/jcb.200810098] [Citation(s) in RCA: 226] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Autophagy, an intracellular degradative pathway, maintains cell homeostasis under normal and stress conditions. Nascent double-membrane autophagosomes sequester and enclose cytosolic components and organelles, and subsequently fuse with the endosomal pathway allowing content degradation. Autophagy requires fusion of autophagosomes with late endosomes, but it is not known if fusion with early endosomes is essential. We show that fusion of AVs with functional early endosomes is required for autophagy. Inhibition of early endosome function by loss of COPI subunits (β′, β, or α) results in accumulation of autophagosomes, but not an increased autophagic flux. COPI is required for ER-Golgi transport and early endosome maturation. Although loss of COPI results in the fragmentation of the Golgi, this does not induce the formation of autophagosomes. Loss of COPI causes defects in early endosome function, as both transferrin recycling and EGF internalization and degradation are impaired, and this loss of function causes an inhibition of autophagy, an accumulation of p62/SQSTM-1, and ubiquitinated proteins in autophagosomes.
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Affiliation(s)
- Minoo Razi
- London Research Institute, Cancer Research UK, London WC2A 3PX, England, UK
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13
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Zhong Y, Wang QJ, Li X, Yan Y, Backer JM, Chait BT, Heintz N, Yue Z. Distinct regulation of autophagic activity by Atg14L and Rubicon associated with Beclin 1-phosphatidylinositol-3-kinase complex. Nat Cell Biol 2009; 11:468-76. [PMID: 19270693 DOI: 10.1038/ncb1854] [Citation(s) in RCA: 757] [Impact Index Per Article: 50.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Accepted: 02/03/2009] [Indexed: 12/30/2022]
Abstract
Beclin 1, a mammalian autophagy protein that has been implicated in development, tumour suppression, neurodegeneration and cell death, exists in a complex with Vps34, the class III phosphatidylinositol-3-kinase (PI(3)K) that mediates multiple vesicle-trafficking processes including endocytosis and autophagy. However, the precise role of the Beclin 1-Vps34 complex in autophagy regulation remains to be elucidated. Combining mouse genetics and biochemistry, we have identified a large in vivo Beclin 1 complex containing the known proteins Vps34, p150/Vps15 and UVRAG, as well as two newly identified proteins, Atg14L (yeast Atg14-like) and Rubicon (RUN domain and cysteine-rich domain containing, Beclin 1-interacting protein). Characterization of the new proteins revealed that Atg14L enhances Vps34 lipid kinase activity and upregulates autophagy, whereas Rubicon reduces Vps34 activity and downregulates autophagy. We show that Beclin 1 and Atg14L synergistically promote the formation of double-membraned organelles that are associated with Atg5 and Atg12, whereas forced expression of Rubicon results in aberrant late endosomal/lysosomal structures and impaired autophagosome maturation. We hypothesize that by forming distinct protein complexes, Beclin 1 and its binding proteins orchestrate the precise function of the class III PI(3)K in regulating autophagy at multiple steps.
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14
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Takahashi K, Ueno T, Tanida I, Minematsu-Ikeguchi N, Murata M, Kominami E. Characterization of CAA0225, a Novel Inhibitor Specific for Cathepsin L, as a Probe for Autophagic Proteolysis. Biol Pharm Bull 2009; 32:475-9. [DOI: 10.1248/bpb.32.475] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Katsuyuki Takahashi
- Clinical Laboratory Department, Nihon University School of Medicine
- Department of Biochemistry, Juntendo University School of Medicine
| | - Takashi Ueno
- Department of Biochemistry, Juntendo University School of Medicine
| | - Isei Tanida
- Department of Biochemistry and Cell Biology, National Institute of Infectious Disease
| | | | | | - Eiki Kominami
- Department of Biochemistry, Juntendo University School of Medicine
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15
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Bialik S, Kimchi A. Autophagy and tumor suppression: recent advances in understanding the link between autophagic cell death pathways and tumor development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 615:177-200. [PMID: 18437896 DOI: 10.1007/978-1-4020-6554-5_9] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Autophagy is a process by which the cell recycles its components through self-consumption of cellular organelles and bulk cytoplasm. In times of stress, it serves to generate much needed nutrients. When overactivated, however, the orderly destruction of organelles can lead to cell death. At times, autophagic cell death is used as an alternative to apoptosis to eliminate unwanted, damaged, or transformed cells. Consistent with this, tumorigenesis is associated with a downregulation in autophagy, and genes that mediate the execution of the process have been shown to be tumor suppressors. At the same time, basal autophagy has been harnessed by some tumor cells as a survival mechanism to protect against ischemia and signals that induce apoptosis. Thus, the relationship between autophagy and tumor development is complex. Here, we discuss the basic machinery of mammalian autophagy and its regulators, with specific emphasis on those genes that have been linked to cancer. Research supporting the divergent nature of autophagy in both tumor suppression and tumor progression is presented. We conclude with a survey of recent approaches to treating cancer with strategies that modulate autophagy.
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Affiliation(s)
- Shani Bialik
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
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16
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Roberts EA, Deretic V. Autophagic proteolysis of long-lived proteins in nonliver cells. Methods Mol Biol 2008; 445:111-7. [PMID: 18425445 DOI: 10.1007/978-1-59745-157-4_6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Autophagy is a cellular homeostasis pathway used to sustain cellular anabolic needs during times of nutrient or energy deprivation. Autophagosomes sequester cytoplasmic constituents, including macromolecules such as long-lived proteins. Upon fusion of autophagosomes with lysosomes, the engulfed cargo is degraded. The proteolysis of longlived proteins by macroautophagy is a standard, specific measure of autophagic degradation and represents an end-point assay for the pathway. The assay is based on a pulse-chase approach, whereby cellular proteins are radiolabeled by an isotopically marked amino acid, the short-lived, rapidly turned over, proteins are allowed to be degraded during a long chase period, and then the remaining, stable radiolabeled proteins are subjected to autophagic degradation. The classical application of this method has been in hepatocytes, but the recent growth of interest in autophagy has necessitated adaptation of this method in nonliver cells. Here we describe a protocol to quantify autophagic degradation of longlived proteins in macrophages. This chapter details the method of analyzing autophagic proteolysis in RAW264.7 mouse macrophages.
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Affiliation(s)
- Esteban A Roberts
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, Albuquerque, NM, USA
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17
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Tamai K, Tanaka N, Nara A, Yamamoto A, Nakagawa I, Yoshimori T, Ueno Y, Shimosegawa T, Sugamura K. Role of Hrs in maturation of autophagosomes in mammalian cells. Biochem Biophys Res Commun 2007; 360:721-7. [PMID: 17624298 DOI: 10.1016/j.bbrc.2007.06.105] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Accepted: 06/16/2007] [Indexed: 12/30/2022]
Abstract
Autophagy is an evolutionarily conserved system responsible for the degradation of cellular components and contributes to the increasing of amino acid pool, organelle turnover, and elimination of intracellular bacteria. The molecular process of autophagy is still unclear. Here we demonstrate that Hrs, a master regulator in endosomal protein sorting, plays critical roles for the autophagic degradation of non-specific proteins and Streptococcus pyogenes. We found that Hrs containing FYVE domain is localized to autophagosomes. Hrs depletion resulted in a significant decrease in the number of mature autophagosomes (autophagolysosomes) detected by the co-localization of autophagosome marker LC3 and lysosome marker LAMP-1. In contrast, formation of the primary autophagosome, detected by LC3 immunoblotting and lysosomal degradation of non-specific proteins, were not significantly altered by Hrs depletion. Based on these results, we propose a novel function of Hrs, as a crucial player in the maturation of autophagosomes.
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Affiliation(s)
- Keiichi Tamai
- Department of Microbiology and Immunology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan
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18
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Young ARJ, Chan EYW, Hu XW, Köchl R, Crawshaw SG, High S, Hailey DW, Lippincott-Schwartz J, Tooze SA. Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes. J Cell Sci 2006; 119:3888-900. [PMID: 16940348 DOI: 10.1242/jcs.03172] [Citation(s) in RCA: 607] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Autophagy, fundamentally a lysosomal degradation pathway, functions in cells during normal growth and certain pathological conditions, including starvation, to maintain homeostasis. Autophagosomes are formed through a mechanism that is not well understood, despite the identification of many genes required for autophagy. We have studied the mammalian homologue of Atg9p, a multi-spanning transmembrane protein essential in yeast for autophagy, to gain a better understanding of the function of this ubiquitious protein. We show that both the N- and C-termini of mammalian Atg9 (mAtg9) are cytosolic, and predict that mAtg9 spans the membrane six times. We find that mAtg9 is located in the trans-Golgi network and late endosomes and colocalizes with TGN46, the cation-independent mannose-6-phosphate receptor, Rab7 and Rab9. Amino acid starvation or rapamycin treatment, which upregulates autophagy, causes a redistribution of mAtg9 from the TGN to peripheral, endosomal membranes, which are positive for the autophagosomal marker GFP-LC3. siRNA-mediated depletion of the putative mammalian homologue of Atg1p, ULK1, inhibits this starvation-induced redistribution. The redistribution of mAtg9 also requires PI 3-kinase activity, and is reversed after restoration of amino acids. We speculate that starvation-induced autophagy, which requires mAtg9, may rely on an alteration of the steady-state trafficking of mAtg9, in a Atg1-dependent manner.
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Affiliation(s)
- Andrew R J Young
- Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London, WC2A 3PX, UK
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19
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Köchl R, Hu XW, Chan EYW, Tooze SA. Microtubules facilitate autophagosome formation and fusion of autophagosomes with endosomes. Traffic 2006; 7:129-45. [PMID: 16420522 DOI: 10.1111/j.1600-0854.2005.00368.x] [Citation(s) in RCA: 333] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Nutrient deprivation of eukaryotic cells provokes a variety of stress responses, including autophagy. Autophagy is carried out by autophagosomes which sequester cytosolic components and organelles for degradation after fusion with protease-containing endosomes. To determine the role of microtubules in autophagy, we used nocodazole and vinblastine to disrupt microtubules and independently measured formation and fusion of autophagsosomes in primary rat hepatocytes. By measuring the translocation of GFP-LC3, an autophagosomal marker, to autophagosomes and the lipidation of GFP-LC3, we quantified the rate and magnitude of autophagosome formation. Starvation increased both the rate of autophagosome formation over the basal level and the total number of autophagosomes per cell. Maximal autophagosome formation required an intact microtubule network. Fusion of autophagosomes with endosomes, assayed by acquisition of protease-inhibitor sensitivity as well as overlap with LysoTracker Red-positive endosomes, required intact microtubules. Live-cell imaging demonstrated that autophagosomes were motile structures, and their movement also required microtubules. Interestingly, vinblastine stimulated autophagosome formation more than twofold before any discernable change in the microtubule network was observed. Stimulation of autophagosome formation by vinblastine was independent of nutrients and mTOR activity but was inhibited by depletion of the Autophagy proteins Atg5 and Atg6, known to be required for autophagy.
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Affiliation(s)
- Robert Köchl
- Cancer Research UK, London Research Institute, Secretory Pathways Laboratory, 44 Lincoln's Inn Fields, London, WC2A 3PX, UK
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20
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Komatsu M, Waguri S, Ueno T, Iwata J, Murata S, Tanida I, Ezaki J, Mizushima N, Ohsumi Y, Uchiyama Y, Kominami E, Tanaka K, Chiba T. Impairment of starvation-induced and constitutive autophagy in Atg7-deficient mice. ACTA ACUST UNITED AC 2005; 169:425-34. [PMID: 15866887 PMCID: PMC2171928 DOI: 10.1083/jcb.200412022] [Citation(s) in RCA: 1854] [Impact Index Per Article: 97.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Autophagy is a membrane-trafficking mechanism that delivers cytoplasmic constituents into the lysosome/vacuole for bulk protein degradation. This mechanism is involved in the preservation of nutrients under starvation condition as well as the normal turnover of cytoplasmic component. Aberrant autophagy has been reported in several neurodegenerative disorders, hepatitis, and myopathies. Here, we generated conditional knockout mice of Atg7, an essential gene for autophagy in yeast. Atg7 was essential for ATG conjugation systems and autophagosome formation, amino acid supply in neonates, and starvation-induced bulk degradation of proteins and organelles in mice. Furthermore, Atg7 deficiency led to multiple cellular abnormalities, such as appearance of concentric membranous structure and deformed mitochondria, and accumulation of ubiquitin-positive aggregates. Our results indicate the important role of autophagy in starvation response and the quality control of proteins and organelles in quiescent cells.
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Affiliation(s)
- Masaaki Komatsu
- Department of Molecular Oncology, Tokyo Metropolitan Institute of Medical Science, Bunkyo-ku, Tokyo 113-8613, Japan
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21
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Abstract
Autophagy is characterized by sequestration of bulk cytoplasm and organelles in double or multimembrane autophagic vesicles, and their delivery to and subsequent degradation by the cell's own lysosomal system. Autophagy has multiple physiological functions in multicellular organisms, including protein degradation and organelle turnover. Genes and proteins that constitute the basic machinery of the autophagic process were first identified in the yeast system and some of their mammalian orthologues have been characterized as well. Increasing lines of evidence indicate that these molecular mechanisms may be recruited by an alternative, caspase-independent form of programmed cell death, named autophagic type II cell death. In some settings, autophagy and apoptosis seem to be interconnected positively or negatively, introducing the concept of 'molecular switches' between them. Additionally, mitochondria may be central organelles integrating the two types of cell death. Malignant transformation is frequently associated with suppression of autophagy. The recent implication of tumor suppressors like Beclin 1, DAP-kinase and PTEN in autophagic pathways indicates a causative role for autophagy deficiencies in cancer formation. Autophagic cell death induction by some anticancer agents underlines the potential utility of its induction as a new cancer treatment modality.
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Affiliation(s)
- Devrim Gozuacik
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
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22
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Tsuneoka M, Umata T, Kimura H, Koda Y, Nakajima M, Kosai K, Takahashi T, Takahashi Y, Yamamoto A. c-myc induces autophagy in rat 3Y1 fibroblast cells. Cell Struct Funct 2003; 28:195-204. [PMID: 12951440 DOI: 10.1247/csf.28.195] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The proto-oncogene c-myc is a multifunctional gene that regulates cell division, cell growth, and apoptosis. Here we report a new function of c-myc: induction of autophagy. Autophagy is a bulk degradation system for intracellular proteins. Autophagy proceeds with characteristic morphologies, which begins with the formation of a double-membrane structure called the autophagosome surrounding a portion of the cytoplasm, after which its outer membrane then fuses with the lysosomal membrane to become an autolysosome. Autophagosomes and autolysosomes are generally called autophagic vacuoles. When c-Myc protein was overexpressed in rat 3Y1 fibroblasts or when the chimeric protein c-MycER was activated by estrogen, the number of autophagic vacuoles in cells increased significantly. The formation of autophagic vacuoles induced by c-Myc was completely blocked by a specific inhibitor of autophagosome formation, 3-methyladenine. A c-Myc mutant lacking Myc Box II induced neither apoptosis nor oncogenic transformation, but still stimulated autophagy. An inhibitor of caspases suppressed apoptosis but not autophagy. These results suggest that the autophagy caused by c-myc is not due to the apoptosis or tumorigenesis induced by c-myc. Taken together, our results suggest that the induction of autophagy is a novel function of c-myc.
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Affiliation(s)
- Makoto Tsuneoka
- Division of Human Genetics, Department of Forensic Medicine, Kurume University School of Medicine, Kurume, Japan.
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23
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Tallóczy Z, Jiang W, Virgin HW, Leib DA, Scheuner D, Kaufman RJ, Eskelinen EL, Levine B. Regulation of starvation- and virus-induced autophagy by the eIF2alpha kinase signaling pathway. Proc Natl Acad Sci U S A 2002; 99:190-5. [PMID: 11756670 PMCID: PMC117537 DOI: 10.1073/pnas.012485299] [Citation(s) in RCA: 600] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The eIF2alpha kinases are a family of evolutionarily conserved serine/threonine kinases that regulate stress-induced translational arrest. Here, we demonstrate that the yeast eIF2alpha kinase, GCN2, the target phosphorylation site of Gcn2p, Ser-51 of eIF2alpha, and the eIF2alpha-regulated transcriptional transactivator, GCN4, are essential for another fundamental stress response, starvation-induced autophagy. The mammalian IFN-inducible eIF2alpha kinase, PKR, rescues starvation-induced autophagy in GCN2-disrupted yeast, and pkr null and Ser-51 nonphosphorylatable mutant eIF2alpha murine embryonic fibroblasts are defective in autophagy triggered by herpes simplex virus infection. Furthermore, PKR and eIF2alpha Ser-51-dependent autophagy is antagonized by the herpes simplex virus neurovirulence protein, ICP34.5. Thus, autophagy is a novel evolutionarily conserved function of the eIF2alpha kinase pathway that is targeted by viral virulence gene products.
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Affiliation(s)
- Zsolt Tallóczy
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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24
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Liang XH, Jackson S, Seaman M, Brown K, Kempkes B, Hibshoosh H, Levine B. Induction of autophagy and inhibition of tumorigenesis by beclin 1. Nature 1999; 402:672-6. [PMID: 10604474 DOI: 10.1038/45257] [Citation(s) in RCA: 2596] [Impact Index Per Article: 103.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The process of autophagy, or bulk degradation of cellular proteins through an autophagosomic-lysosomal pathway, is important in normal growth control and may be defective in tumour cells. However, little is known about the genetic mediators of autophagy in mammalian cells or their role in tumour development. The mammalian gene encoding Beclin 1, a novel Bcl-2-interacting, coiled-coil protein, has structural similarity to the yeast autophagy gene, apg6/vps30, and is mono-allelically deleted in 40-75% of sporadic human breast cancers and ovarian cancers. Here we show, using gene-transfer techniques, that beclin 1 promotes autophagy in autophagy-defective yeast with a targeted disruption of agp6/vps30, and in human MCF7 breast carcinoma cells. The autophagy-promoting activity of beclin 1 in MCF7 cells is associated with inhibition of MCF7 cellular proliferation, in vitro clonigenicity and tumorigenesis in nude mice. Furthermore, endogenous Beclin 1 protein expression is frequently low in human breast epithelial carcinoma cell lines and tissue, but is expressed ubiquitously at high levels in normal breast epithelia. Thus, beclin 1 is a mammalian autophagy gene that can inhibit tumorigenesis and is expressed at decreased levels in human breast carcinoma. These findings suggest that decreased expression of autophagy proteins may contribute to the development or progression of breast and other human malignancies.
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Affiliation(s)
- X H Liang
- Department of Medicine, Columbia University College of Physicians & Surgeons, New York, New York 10032, USA
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25
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Réz G, Tóth S, Pálfia Z. Cellular autophagic capacity is highly increased in azaserine-induced premalignant atypical acinar nodule cells. Carcinogenesis 1999; 20:1893-8. [PMID: 10506101 DOI: 10.1093/carcin/20.10.1893] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Although cellular autophagy is recognized as a major pathway of macromolecular catabolism, little data are available regarding its activity or regulation in tumor cells. We approach this problem by morphometrical investigation into the possible changes in autophagic activity during progression of rat pancreatic adenocarcinoma induced by azaserine and promoted by a raw soya flour-containing pancreatotrophic diet. In the present study, the autophagic capacity of the carcinogen-induced premalignant atypical acinar nodule cells was characterized and compared with controls (normal tissue of rats kept on standard laboratory or pancreatotrophic diet and host tissue of the premalignant nodules of the azaserine-treated rats). Given for 90 min, vinblastine, an enhancer of autophagic segregation (i.e. formation of autophagic vacuoles), caused a one to two orders of magnitude larger expansion of the autophagic compartment in atypical nodule cells than in the controls. Then a 20 min blockade of segregation by cycloheximide led to regression of the autophagic compartment, which was barely measurable or moderate in the controls but exceeded 50% in the premalignant cells. At the same time, the cytoplasmic volume fraction of early autophagic vacuoles regressed to a near zero value in each cell type. Expansion and regression rates of these nascent vacuoles showed that both segregation and degradation were 6-20 times faster in the nodule than in normal tissue cells. These results show that the autophagic capacity of the premalignant cells in our system is greatly increased, possibly making these cells unusually sensitive to up-regulation of their self-digesting activity in response to different extracellular signals or drugs.
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Affiliation(s)
- G Réz
- Department of General Zoology, Loránd Eötvös University, pf 330, H-1445 Budapest, Hungary. grez2cerberus.elte.hu
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26
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Gebreselassie D, Schön A. Energy metabolism of non-transformed and benzypyrene-transformed 3T3 cells: a microcalorimetric study. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1143:211-4. [PMID: 8318520 DOI: 10.1016/0005-2728(93)90145-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Non-transformed and benzpyrene-transformed 3T3 cells attached to microcarriers were studied with microcalorimetry. The transformed cells manifested a higher rate of heat production and a larger anaerobic contribution to the total catabolism than did the non-transformed cells. Moreover, the transformed cells were characterized by a highly pH-dependent metabolism with a drop in thermal power occurring 0.3 pH units lower than the corresponding drop for the non-transformed cell line. We believe this shift in pH to be due to the higher intracellular pH maintained by the transformed cells. In addition, the study describes the correlation between rate of heat production per cell and the degree of confluency for each cell line, respectively.
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27
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Thorén SA. Calorimetry: a new quantitative in vitro method in cell toxicology. A dose/effect study of alveolar macrophages exposed to particles. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1992; 36:307-18. [PMID: 1507265 DOI: 10.1080/15287399209531641] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A short-term toxicological test has been developed using a calorimetric method. The metabolic activity, observed as the heat exchange rate, was monitored from alveolar rabbit macrophages in monolayers exposed to different metal and non-metal particles. Calorimetric activity indices and viability indices were introduced, from which toxic effects could be assessed. Manganese dioxide particles were found to be cytotoxic. In contrast, titanium dioxide particles seemed to be harmless. The results were in accordance with the cell survival found by use of a fluorescein ester staining method and measured by an image analyzer. Toxic effects from quartz in the form of increased metabolic activity of exposed cells could be detected by the calorimeter in contradiction to the use of the image analyzer. This latter result supports the hypothesis that silica particles cause chronic modification of the macrophage function and that this change in the alveolar macrophage function may be the first of a series of processes leading to pulmonary fibrosis.
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Affiliation(s)
- S A Thorén
- Department of Internal Medicine, University Hospital, Lund, Sweden
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28
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Lee HK, Jones RT, Myers RA, Marzella L. Regulation of protein degradation in normal and transformed human bronchial epithelial cells in culture. Arch Biochem Biophys 1992; 296:271-8. [PMID: 1605636 DOI: 10.1016/0003-9861(92)90572-e] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Protein degradation rates are decreased in some transformed cells of mesenchymal origin. We have tested the generality of this phenomenon and evaluated the role of the lysosomes in this down-regulation. To this end we have compared the induction of lysosomal protein degradation among normal, transformed (BEAS-2B), and transformed tumorigenic (BZR, Calu-1) human bronchial epithelial cells in culture. Serum and/or nutrient deprivation, cell confluency, and Ca2+ were used to modulate lysosomal protein degradation. Protein degradation and synthesis were determined by the release or incorporation of [14C]valine in the cells. Autophagic degradation of cytoplasm by lysosomes was evaluated by ultrastructural morphometry. Basal protein degradation was lower (27%) in two of the transformed cell lines (BEAS-2B and BZR). Incorporation of [14C]valine label was raised approximately 4-fold in the transformed cells. Nutrient deprivation stimulated protein degradation equally (2-fold) in transformed and normal cells. Postconfluency increased (1.5-fold) basal protein degradation in Calu-1 cells and a marked enhancement (4-fold) of degradation occurred during nutrient deprivation. Culture of normal human bronchial epithelial cells in high Ca2+ caused phenotypic changes and increased (30%) the degradation of protein induced by nutrient deprivation. In Calu-1, high Ca2+ caused only phenotypic changes. The volume density (Vd) of autophagic vacuoles and dense bodies in the transformed cells was lower under basal conditions but increased markedly during nutrient deprivation. A marked accumulation of lysosomes also occurred in transformed cells during postconfluency. We conclude that cell transformation lowers basal protein degradation in some human epithelial cells. Lysosomal proteolysis of transformed cells is not down-regulated and can be markedly enhanced during nutritional deprivation by the autophagic degradation pathway.
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Affiliation(s)
- H K Lee
- Department of Pathology, School of Medicine, University of Maryland, Baltimore 21201
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29
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Haliotis T, Trimble W, Chow S, Bull S, Mills G, Girard P, Kuo JF, Hozumi N. Expression of ras oncogene leads to down-regulation of protein kinase C. Int J Cancer 1990; 45:1177-83. [PMID: 2190939 DOI: 10.1002/ijc.2910450631] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The effect of mutated c-Ha-ras expression on Ca2+ and phospholipid-dependent protein kinase C (PKC) activity during the process of transformation was analysed using an inducible metallothionein-ras hybrid oncogene system. A close correlation was found between the timing of ras expression and the loss of PKC enzymatic activity measured in a cell-free system. Examination of the subcellular distribution of the enzyme in inducible and constitutive ras-transformants revealed that expression of ras was associated with an apparent translocation of PKC to the plasma membrane concomitant with down-regulation of PKC enzymatic activity in particulate as well as cytosolic fractions. Quantitation of PKC protein utilizing a PKC-specific antiserum showed that ras expression was associated with a decrease in the total amount of PKC protein present in the cell. We conclude that transformation by c-Ha-ras is accompanied by down-regulation of PKC activity and that the basis of this effect may, to a large extent, lie in the down-regulation of the amount of PKC protein.
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Affiliation(s)
- T Haliotis
- Mount Sinai Hospital Research Institute, University of Toronto, Ontario, Canada
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30
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Thorén SA, Monti M, Holma B. Heat conduction microcalorimetry of overall metabolism in rabbit alveolar macrophages in monolayers and in suspensions. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1033:305-10. [PMID: 2317506 DOI: 10.1016/0304-4165(90)90138-m] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A technique has been developed for studying the overall metabolism in small numbers of cells in monolayers and in suspensions by measuring the heat exchange rate with a thermopile heat-conduction microcalorimeter. The system was tested with alveolar macrophages from rabbits, and heat flux-time curves could be monitored from numbers of cells as low as 0.05 . 10(6). The metabolic activity was found to be unchanged or to decrease very slowly over a period of 20 h. In a conventional cell medium, without the addition of serum, a mean heat flux value of 19.4 (S.D. 3.2) pW. cell-1 (37 degrees C, pH = 7.4) was obtained for alveolar macrophages in monolayers. The corresponding value for cells in the same medium, with the addition of 20% homologous rabbit serum, was 27.0 (S.D. 2.0). We suggest that this calorimetric method can be used as a short-term cytotoxic test for measuring potentially toxic agents in our environment; this test can involve alveolar macrophages of either animal or human origin. In such an assay, the cells should be used in monolayers, and suspensions should be avoided. We found that when alveolar macrophages were used in suspension, the metabolic activity, measured as heat flux, was dependent on cell concentration, even at values as low as 0.2. 10(6) cells per ml.
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Affiliation(s)
- S A Thorén
- Institute of Hygiene and The Budde Laboratory, University of Copenhagen, Denmark
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Gulve EA, Dice JF. Regulation of protein synthesis and degradation in L8 myotubes. Effects of serum, insulin and insulin-like growth factors. Biochem J 1989; 260:377-87. [PMID: 2669733 PMCID: PMC1138680 DOI: 10.1042/bj2600377] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We have examined the regulation of protein turnover in rat skeletal myotubes from the L8 cell line. We measured protein synthesis by the rates of incorporation of radiolabelled tyrosine into protein in the presence of a flooding dose of non-radioactive tyrosine. We monitored degradation of proteins labelled with radioactive tyrosine by the release of acid-soluble radioactivity into medium containing excess nonradioactive tyrosine. Extracellular tyrosine pools and intracellular tyrosyl-tRNA equilibrate rapidly during measurements of protein synthesis, and very little reutilization of the radiolabelled tyrosine occurs during degradation measurements. Measured rates of protein synthesis and degradation are constant for several hours, and changes in myotube protein content can be accurately predicted by the measured rates of protein synthesis and degradation. Most of the myotube proteins labelled with radioactive tyrosine for 2 days are degraded, with half-lives (t1/2) of approx. 50 h. A small proportion (less than 2.5%) of the radiolabelled proteins are degraded more rapidly (t1/2 less than 10 h), and, at most, a small proportion (less than 15%) are degraded more slowly (t1/2 greater than 50 h). A variety of agents commonly added to primary muscle cell cultures or to myoblast cell lines (18% Medium 199, 1% chick-embryo extract, antibiotics and antifungal agents) had no effect on rates of protein synthesis or degradation. Horse serum, fetal bovine serum and insulin stimulate protein synthesis and inhibit the degradation of long-lived proteins without affecting the degradation of short-lived proteins. Insulin-like growth factors (IGF)-1 and -2 also stimulate protein synthesis and inhibit protein degradation. The stimulation of protein synthesis and the inhibition of protein degradation are of similar magnitude (a maximum of approx. 2-fold) and display similar sensitivities to a particular anabolic agent. Insulin stimulates protein synthesis and inhibits protein degradation only at supraphysiological doses, whereas IGF-1 and -2 are effective at physiological concentrations. These and other findings suggest that IGFs may be important regulators of skeletal muscle growth during the fetal and early neonatal periods.
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Affiliation(s)
- E A Gulve
- Department of Physiology and Biophysics, Harvard Medical School, Boston, MA 02115
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Lee HK, Myers RA, Marzella L. Stimulation of autophagic protein degradation by nutrient deprivation in a differentiated murine teratocarcinoma (F9 12-1a) cell line. Exp Mol Pathol 1989; 50:139-46. [PMID: 2646143 DOI: 10.1016/0014-4800(89)90063-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have evaluated the participation of the lysosomal degradation pathway in the increased protein degradation induced by nutrient deprivation in transformed cells. To this end we used a clone, 12-1a, derived from a murine teratocarcinoma cell line (F9 12-1) induced to differentiate by culture in retinoic acid. Culture of 12-1a cells, prelabeled with L-[U-14C]valine, in nutrient-deprived medium (Hanks' balanced salt solution plus Ca++) stimulated the protein degradation rate from 0.9% hr to 1.4% hr. Morphometric analysis demonstrated that during nutrient deprivation, the volume density of lysosomes increased 3-fold; the numerical density of lysosomes increased 2-fold; the mean area of lysosomal profiles increased 1.7-fold (1.40 microns2 vs 0.81 microns2). The volume density and numerical density of the dense bodies tended to decrease by approximately 60% without any change in the mean volume of the dense bodies. These data indicate that nutrient deprivation increases protein degradation in transformed cells by increasing the sequestration of cytoplasm into the lysosomes. The decrease in the number of dense bodies indicates that these structures (also termed residual bodies) are functional in transformed cells and merge with the lysosomes to provide more degradative enzymes to enhance proteolysis. This study provides direct evidence that serum factors and nutrients play a crucial role in modulation of lysosomal protein degradation in transformed cells.
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Affiliation(s)
- H K Lee
- Department of Pathology, School of Medicine, University of Maryland, Baltimore 21201
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Yucel T, Ahlberg J, Blanck A, Glaumann H. Protein degradation in lysosomes from chemically induced malignant rat hepatoma. VIRCHOWS ARCHIV. B, CELL PATHOLOGY INCLUDING MOLECULAR PATHOLOGY 1988; 55:1-9. [PMID: 2898828 DOI: 10.1007/bf02896554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Hepatocellular carcinomas were induced in rat liver by exposing the animals to diethylnitrosamine and 2-acetylaminofluorene in combination with partial hepatectomy. Light and electron microscopy demonstrated that the general appearance of the tumour tissue was that of highly differentiated malignant hepatocytic cells. Morphometrically there was a difference between normal and malignant cells in that the entire lysosomal apparatus was twice as large in malignant cells as in normal cells. This was mainly due to an increase in the fractional volume of autophagic vacuoles. A total lysosomal fraction (dense bodies and autophagic vacuoles) was isolated and characterized from both control and tumour livers. Marker enzyme analysis showed that the lysosomal enzyme activities were significantly lower in malignant liver tissue. Injection of leupeptin, an inhibitor of cathepsins B, H, and L, into rats did not increase the fractional volume of autophagic vacuoles in tumour tissue as much as in normal liver tissue. The proteolytic rate was lower in the lysosomal fraction from hepatoma cell tissue compared with the lysosomal fraction from normal cell tissue. This could conceivably be due to the lower activities of lysosomal enzymes. However, if the recovery of lysosomes is taken into account no clear-cut difference in lysosomal proteolysis between control and malignant liver tissue was noted. Accordingly, in malignant liver tissue a proteolytic balance is obtained characterized by an increased fractional volume of AVs and lower rate of protein degradation in individual lysosomes.
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Affiliation(s)
- T Yucel
- Department of Pathology, Karolinska Institute, Huddinge University Hospital, Sweden
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Papadopoulos T, Pfeifer U. Protein turnover and cellular autophagy in growing and growth-inhibited 3T3 cells. Exp Cell Res 1987; 171:110-21. [PMID: 3622627 DOI: 10.1016/0014-4827(87)90255-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The relationship between growth, protein degradation, and cellular autophagy was tested in growing and in growth-inhibited 3T3 cell monolayers. For the biochemical evaluation of DNA and protein metabolism, growth-inhibited 3T3 cell monolayers with high cell density and growing 3T3 cell monolayers with low cell density were labeled simultaneously with [14C]thymidine and [3H]leucine. The evaluation of the DNA turnover and additional [3H]thymidine autoradiography showed that 24 to 5% of 3T3 cells continue to replicate even in the growth-inhibited state, where no accumulation of protein and DNA can be observed. Cell loss, therefore, has to be assumed to compensate for the ongoing cell proliferation. When the data of protein turnover were corrected for cell loss, it was found that the rate constant of protein synthesis in nongrowing monolayers was reduced to half the value found in growing monolayers. Simultaneously, the rate constant of protein degradation in nongrowing monolayers was increased to about 1.5-fold the value of growing monolayers. In parallel to the increased rate constant of protein degradation, the cytoplasmic volume fraction of early autophagic vacuoles (AVs) as determined by electron microscopic morphometry was found to be increased twofold in nongrowing 3T3 cell monolayers when compared with the volume fraction of early AVs in growing 3T3 cell monolayers. These data are in agreement with the assumption that cellular autophagy represents a major pathway of regulating protein degradation in 3T3 cells and that the regulation of autophagic protein degradation is of relevance for the transition from a growing to a nongrowing state.
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Schön A, Wadsö I. Microcalorimetric measurements on tissue cells attached to microcarriers in stirred suspension. JOURNAL OF BIOCHEMICAL AND BIOPHYSICAL METHODS 1986; 13:135-43. [PMID: 3097112 DOI: 10.1016/0165-022x(86)90086-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Vero cells growing on microcarriers in stirred suspension were observed calorimetrically using a vessel designed for use with the LKB 'BioActivity Monitor'. Rates of formation of carbon dioxide and lactate were followed in parallel. The results showed that the power and rate of lactate formation could be correlated to both cell number and amount of protein, while the rate of carbon dioxide formation was slightly better correlated to cell number. The power per cell was 27.4 +/- 2.1 pW. Only 33% of this power could be accounted for by the formation of lactate and carbon dioxide.
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Ngo JL, Orlando RA, Ibsen KH. Pyruvate kinase and total protein are regulated differently during growth of P-815 mastocytoma cells. Arch Biochem Biophys 1986; 247:171-82. [PMID: 3085594 DOI: 10.1016/0003-9861(86)90546-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Total protein content of P-815 mastocytoma cells decreases and then increases in response to initiation of a new growth cycle. As the level increases, the rate of synthesis declines. Both events occur prior to any decrease in the rate of cellular proliferation. These temporal relationships indicate that the rate of protein synthesis reflects the intracellular concentration of protein rather than the cellular growth rate, as has been hypothesized. Pyruvate kinase protein metabolism differs from that of total protein in three ways: (a) accumulation does not stop, (b) the rate of synthesis does not decrease, and (c) only the rate of pyruvate kinase degradation is altered by a factor present in conditioned media. These observations suggest that there are specific mechanisms regulating pyruvate kinase at a post-transcriptional level.
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Tessitore L, Bonelli G, Isidoro C, Kazakova OV, Baccino FM. Comparative studies on protein turnover regulations in tumor cells and host tissues: development and analysis of an experimental model. Toxicol Pathol 1986; 14:451-6. [PMID: 3544167 DOI: 10.1177/019262338601400411] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The protein mass of cells and tissues is determined by the relative rates of protein synthesis (PS) and degradation (PD). A convergent modulation of both PS and PD is operated by many cell types to regulate protein accumulation and thus growth. Transformed and neoplastic cells may show markedly defective PD regulations. Yet even highly-deviated cells such as those of the transplantable Yoshida ascites hepatoma AH-130 cease growth when attaining a conspicuous population size, by operating a combined reduction of PS and acceleration of PD. As in normal cells, PD acceleration is effected through an activation of the acidic-vacuolar (lysosomal) mechanism. AH-130 tumor-bearing rats develop a markedly negative nitrogen balance early after transplantation. Tumor growth involves pronounced perturbations in host body and tissue protein metabolism. Apparently, these changes occur mostly at the level of PD rather than PS, at least in liver and skeletal muscle (gastrocnemius). These observations indicate that either tumor and host cells sense different signals for PD regulations or their thresholds for the same signals are poised differently. This model seems most suitable for further studies to elucidate which signals and mechanisms are involved in these protein metabolic perturbations and possibly, to develop the rationale for adequate corrective strategies.
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Sakai T, Ikehara T, Yamaguchi H, Ohsaka N, Miyamoto H. Effects of K+-deficiency and serum supplementation on protein turnover and nucleic acid synthesis in HeLa cells. Life Sci 1985; 36:169-76. [PMID: 2578207 DOI: 10.1016/0024-3205(85)90096-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
When most of the K+ in a chemically defined medium was replaced with Rb+, cell growth of HeLa cells was strongly inhibited. The growth was partially but significantly restored by an addition of 5% dialyzed calf serum to the medium. The inhibition of cell growth in Rb+-substituted medium was partly due to suppression of protein synthesis by K+ deficiency, but the key mechanism of inhibition is still unknown. Rb+ substitution did not influence protein degradation or nucleic acid synthesis. The restoration of cell growth on addition of serum took place chiefly through stimulation of DNA synthesis. Protein and RNA syntheses were not affected by addition of serum, and serum-induced prevention of protein degradation was less in Rb+-substituted medium than in normal K+ medium.
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