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Kitaoka Y, Sase K. Molecular aspects of optic nerve autophagy in glaucoma. Mol Aspects Med 2023; 94:101217. [PMID: 37839231 DOI: 10.1016/j.mam.2023.101217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 09/24/2023] [Accepted: 10/08/2023] [Indexed: 10/17/2023]
Abstract
The optic nerve consists of the glia, vessels, and axons including myelin and axoplasm. Since axonal degeneration precedes retinal ganglion cell death in glaucoma, the preceding axonal degeneration model may be helpful for understanding the molecular mechanisms of optic nerve degeneration. Optic nerve samples from these models can provide information on several aspects of autophagy. Autophagosomes, the most typical organelles expressing autophagy, are found much more frequently inside axons than around the glia. Thus, immunoblot findings from the optic nerve can reflect the autophagy state in axons. Autophagic flux impairment may occur in degenerating optic nerve axons, as in other central nervous system neurodegenerative diseases. Several molecular candidates are involved in autophagy enhancement, leading to axonal protection. This concept is an attractive approach to the prevention of further retinal ganglion cell death. In this review, we describe the factors affecting autophagy, including nicotinamide riboside, p38, ULK, AMPK, ROCK, and SIRT1, in the optic nerve and propose potential methods of axonal protection via enhancement of autophagy.
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Affiliation(s)
- Yasushi Kitaoka
- Department of Ophthalmology, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan; Department of Molecular Neuroscience, St. Marianna University Graduate School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan.
| | - Kana Sase
- Department of Ophthalmology, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216-8511, Japan
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Sakai Y, Hanafusa H, Hisamoto N, Matsumoto K. Histidine dephosphorylation of the Gβ protein GPB-1 promotes axon regeneration in C. elegans. EMBO Rep 2022; 23:e55076. [PMID: 36278516 PMCID: PMC9724660 DOI: 10.15252/embr.202255076] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 09/30/2022] [Accepted: 10/04/2022] [Indexed: 12/12/2022] Open
Abstract
Histidine phosphorylation is an emerging noncanonical protein phosphorylation in animals, yet its physiological role remains largely unexplored. The protein histidine phosphatase (PHPT1) was recently identified for the first time in mammals. Here, we report that PHIP-1, an ortholog of PHPT1 in Caenorhabditis elegans, promotes axon regeneration by dephosphorylating GPB-1 Gβ at His-266 and inactivating GOA-1 Goα signaling, a negative regulator of axon regeneration. Overexpression of the histidine kinase NDK-1 also inhibits axon regeneration via GPB-1 His-266 phosphorylation. Thus, His-phosphorylation plays an antiregenerative role in C. elegans. Furthermore, we identify a conserved UNC-51/ULK kinase that functions in autophagy as a PHIP-1-binding protein. We demonstrate that UNC-51 phosphorylates PHIP-1 at Ser-112 and activates its catalytic activity and that this phosphorylation is required for PHIP-1-mediated axon regeneration. This study reveals a molecular link from ULK to protein histidine phosphatase, which facilitates axon regeneration by inhibiting trimeric G protein signaling.
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Affiliation(s)
- Yoshiki Sakai
- Division of Biological Science, Graduate School of ScienceNagoya UniversityNagoyaJapan
| | - Hiroshi Hanafusa
- Division of Biological Science, Graduate School of ScienceNagoya UniversityNagoyaJapan
| | - Naoki Hisamoto
- Division of Biological Science, Graduate School of ScienceNagoya UniversityNagoyaJapan
| | - Kunihiro Matsumoto
- Division of Biological Science, Graduate School of ScienceNagoya UniversityNagoyaJapan
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Gluschko A, Farid A, Herb M, Grumme D, Krönke M, Schramm M. Macrophages target Listeria monocytogenes by two discrete non-canonical autophagy pathways. Autophagy 2021; 18:1090-1107. [PMID: 34482812 DOI: 10.1080/15548627.2021.1969765] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Non-canonical autophagy pathways decorate single-membrane vesicles with Atg8-family proteins such as MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3). Phagosomes containing the bacterial pathogen Listeria monocytogenes (L.m.) can be targeted by a non-canonical autophagy pathway called LC3-associated phagocytosis (LAP), which substantially contributes to the anti-listerial activity of macrophages and immunity. We here characterized a second non-canonical autophagy pathway targeting L.m.-containing phagosomes, which is induced by damage caused to the phagosomal membrane by the pore-forming toxin of L.m., listeriolysin O. This pore-forming toxin-induced non-canonical autophagy pathway (PINCA) was the only autophagic pathway evoked in tissue macrophages deficient for the NADPH oxidase CYBB/NOX2 that produces the reactive oxygen species (ROS) that are required for LAP induction. Similarly, also bone marrow-derived macrophages (BMDM) exclusively targeted L.m. by PINCA as they completely failed to induce LAP because of insufficient production of ROS through CYBB, in part, due to low expression of some CYBB complex subunits. Priming of BMDM with proinflammatory cytokines such as TNF and IFNG/IFNγ increased ROS production by CYBB and endowed them with the ability to target L.m. by LAP. Targeting of L.m. by LAP remained relatively rare, though, preventing LAP from substantially contributing to the anti-listerial activity of BMDM. Similar to LAP, the targeting of L.m.-containing phagosomes by PINCA promoted their fusion with lysosomes. Surprisingly, however, this did not substantially contribute to anti-listerial activity of BMDM. Thus, in contrast to LAP, PINCA does not have clear anti-listerial function suggesting that the two different non-canonical autophagy pathways targeting L.m. may have discrete functions.Abbreviations: actA/ActA: actin assembly-inducing protein A; ATG: autophagy-related; BMDM: Bone marrow-derived macrophages; CALCOCO2/NDP52: calcium-binding and coiled-coil domain-containing protein 2; CYBA/p22phox: cytochrome b-245 light chain; CYBB/NOX2: cytochrome b(558) subunit beta; E. coli: Escherichia coli; IFNG/IFNγ: interferon gamma; L.m.: Listeria monocytogenes; LAP: LC3-associated phagocytosis; LGALS: galectin; LLO: listeriolysin O; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; NCF1/p47phox: neutrophil cytosol factor 1; NCF2/p67phox: neutrophil cytosol factor 2; NCF4/p67phox: neutrophil cytosol factor 4; Peritoneal macrophages: PM; PINCA: pore-forming toxin-induced non-canonical autophagy; plc/PLC: 1-phosphatidylinositol phosphodiesterase; PMA: phorbol 12-myristate 13-acetate; RB1CC1/FIP200: RB1-inducible coiled-coil protein 1; ROS: reactive oxygen species; S. aureus: Staphylococcus aureus; S. flexneri: Shigella flexneri; SQSTM1/p62: sequestosome 1; S. typhimurium: Salmonella typhimurium; T3SS: type III secretion system; TNF: tumor necrosis factor; ULK: unc-51 like autophagy activating kinase; PM: peritoneal macrophages; WT: wild type.
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Affiliation(s)
- Alexander Gluschko
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
| | - Alina Farid
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
| | - Marc Herb
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
| | - Daniela Grumme
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
| | - Martin Krönke
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany.,Center of Molecular Medicine Cologne, Cologne, Germany.,Cologne Cluster of Excellence on Cellular Stress Responses in Aging-associated Diseases Cecad, Cologne, Germany.,German Center for Infection Research Dzif, Cologne, Germany
| | - Michael Schramm
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany
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Guha P, Tyagi R, Chowdhury S, Reilly L, Fu C, Xu R, Resnick AC, Snyder SH. IPMK Mediates Activation of ULK Signaling and Transcriptional Regulation of Autophagy Linked to Liver Inflammation and Regeneration. Cell Rep 2020; 26:2692-2703.e7. [PMID: 30840891 PMCID: PMC6494083 DOI: 10.1016/j.celrep.2019.02.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 12/04/2018] [Accepted: 02/01/2019] [Indexed: 12/14/2022] Open
Abstract
Autophagy plays a broad role in health and disease. Here, we show that
inositol polyphosphate multikinase (IPMK) is a prominent physiological
determinant of autophagy and is critical for liver inflammation and
regeneration. Deletion of IPMK diminishes autophagy in cell lines and mouse
liver. Regulation of autophagy by IPMK does not require catalytic activity. Two
signaling axes, IPMK-AMPK-Sirt-1 and IPMK-AMPK-ULK1, appear to mediate the
influence of IPMK on autophagy. IPMK enhances autophagy-related transcription by
stimulating AMPK-depen-dent Sirt-1 activation, which mediates the deacetylation
of histone 4 lysine 16. Furthermore, direct binding of IPMK to ULK and AMPK
forms a ternary complex that facilitates AMPK-dependent ULK phosphorylation.
Deletion of IPMK in cell lines and intact mice virtually abolishes lipophagy,
promotes liver damage as well as inflammation, and impairs hepatocyte
regeneration. Thus, targeting IPMK may afford therapeutic benefits in
disabilities that depend on autophagy and lipophagy—specifically, in
liver inflammation and regeneration. IPMK is a physiological determinant of autophagy and is critical in liver
inflammation. Two signaling axes, IPMK-AMPK-Sirt-1 and IPMK-AMPK-ULK1, appear to
mediate the influence of IPMK on autophagy. Deletion of IPMK impairs lipophagy
and hepatocyte regeneration.
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Affiliation(s)
- Prasun Guha
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Richa Tyagi
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Sayan Chowdhury
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Luke Reilly
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Chenglai Fu
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Risheng Xu
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Adam C Resnick
- Children's Hospital of Philadelphia, Colket Translational Research Building, 3501 Civic Center Blvd., Philadelphia, PA 19104-4399, USA
| | - Solomon H Snyder
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Dalle Pezze P, Karanasios E, Kandia V, Manifava M, Walker SA, Gambardella Le Novère N, Ktistakis NT. ATG13 dynamics in nonselective autophagy and mitophagy: insights from live imaging studies and mathematical modeling. Autophagy 2020; 17:1131-1141. [PMID: 32320309 PMCID: PMC8143212 DOI: 10.1080/15548627.2020.1749401] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
During macroautophagy/autophagy, the ULK complex nucleates autophagic precursors, which give rise to autophagosomes. We analyzed, by live imaging and mathematical modeling, the translocation of ATG13 (part of the ULK complex) to the autophagic puncta in starvation-induced autophagy and ivermectin-induced mitophagy. In nonselective autophagy, the intensity and duration of ATG13 translocation approximated a normal distribution, whereas wortmannin reduced this effect and shifted to a log-normal distribution. During mitophagy, multiple translocations of ATG13 with increasing time between peaks were observed. We hypothesized that these multiple translocations arise because the engulfment of mitochondrial fragments required successive nucleation of phagophores on the same target, and a mathematical model based on this idea reproduced the oscillatory behavior. Significantly, model and experimental data were also in agreement that the number of ATG13 translocations is directly proportional to the diameter of the targeted mitochondrial fragments. Thus, our data provide novel insights into the early dynamics of selective and nonselective autophagy.Abbreviations: ATG: autophagy related 13; CFP: cyan fluorescent protein; dsRED: Discosoma red fluorescent protein; GABARAP: GABA type A receptor-associated protein; GFP: green fluorescent protein; IVM: ivermectin; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MTORC1: mechanistic target of rapamycin kinase complex 1; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PtdIns3P: PtdIns-3-phosphate; ULK: unc-51 like autophagy activating kinase.
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Affiliation(s)
| | | | - Varvara Kandia
- The Babraham Institute, Babraham Research Campus, Cambridge, UK
| | - Maria Manifava
- The Babraham Institute, Babraham Research Campus, Cambridge, UK
| | - Simon A Walker
- The Babraham Institute, Babraham Research Campus, Cambridge, UK
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6
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Abstract
Macroautophagy/autophagy plays important roles in health and disease, but mechanisms of its activation are unclear. Recently we established IPMK (inositol polyphosphate multikinase) as a physiological determinant of autophagy independent of its catalytic activity. Two signaling axes, IPMK-AMPK-SIRT1 and IPMK-AMPK-ULK1, appear to mediate the influence of IPMK on autophagy. IPMK enhances autophagy-related transcription by stimulating AMPK-dependent SIRT1 activation, which mediates the deacetylation of histone 4 lysine 16. Furthermore, direct binding of IPMK to ULK and AMPK forms a ternary complex that facilitates AMPK-dependent ULK phosphorylation. Deletion of Ipmk virtually abolishes lipophagy, promotes liver damage and impairs hepatocyte regeneration. Our study establishes the importance of IPMK in regulation of autophagy and as a drug target for autophagy-related diseases.
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Affiliation(s)
- Prasun Guha
- a The Solomon H. Snyder Department of Neuroscience , Johns Hopkins University School of Medicine , Baltimore , MD , USA
| | - Solomon H Snyder
- a The Solomon H. Snyder Department of Neuroscience , Johns Hopkins University School of Medicine , Baltimore , MD , USA
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Ravenhill BJ, Boyle KB, von Muhlinen N, Ellison CJ, Masson GR, Otten EG, Foeglein A, Williams R, Randow F. The Cargo Receptor NDP52 Initiates Selective Autophagy by Recruiting the ULK Complex to Cytosol-Invading Bacteria. Mol Cell 2019; 74:320-329.e6. [PMID: 30853402 PMCID: PMC6477152 DOI: 10.1016/j.molcel.2019.01.041] [Citation(s) in RCA: 188] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 11/19/2018] [Accepted: 01/29/2019] [Indexed: 12/27/2022]
Abstract
Xenophagy, a selective autophagy pathway that protects the cytosol against bacterial invasion, relies on cargo receptors that juxtapose bacteria and phagophore membranes. Whether phagophores are recruited from a constitutive pool or are generated de novo at prospective cargo remains unknown. Phagophore formation in situ would require recruitment of the upstream autophagy machinery to prospective cargo. Here, we show that, essential for anti-bacterial autophagy, the cargo receptor NDP52 forms a trimeric complex with FIP200 and SINTBAD/NAP1, which are subunits of the autophagy-initiating ULK and the TBK1 kinase complex, respectively. FIP200 and SINTBAD/NAP1 are each recruited independently to bacteria via NDP52, as revealed by selective point mutations in their respective binding sites, but only in their combined presence does xenophagy proceed. Such recruitment of the upstream autophagy machinery by NDP52 reveals how detection of cargo-associated “eat me” signals, induction of autophagy, and juxtaposition of cargo and phagophores are integrated in higher eukaryotes. NDP52 recruits upstream autophagy machinery to damaged Salmonella-containing vacuoles NDP52 trimerizes with the ULK subunit FIP200 and the TBK1 adaptor SINTBAD NDP52-dependent recruitment of FIP200-ULK and SINTBAD-TBK1 required for xenophagy Recruitment of ULK and TBK1 complexes promotes phagophore formation in situ
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Affiliation(s)
- Benjamin J Ravenhill
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Keith B Boyle
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Natalia von Muhlinen
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Cara J Ellison
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Glenn R Masson
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Elsje G Otten
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Agnes Foeglein
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Roger Williams
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Felix Randow
- Division of Protein and Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK; Addenbrooke's Hospital, Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, UK.
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Tamargo-Gómez I, Mariño G. AMPK: Regulation of Metabolic Dynamics in the Context of Autophagy. Int J Mol Sci 2018; 19:ijms19123812. [PMID: 30501132 PMCID: PMC6321489 DOI: 10.3390/ijms19123812] [Citation(s) in RCA: 161] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 11/20/2018] [Accepted: 11/24/2018] [Indexed: 02/07/2023] Open
Abstract
Eukaryotic cells have developed mechanisms that allow them to link growth and proliferation to the availability of energy and biomolecules. AMPK (adenosine monophosphate-activated protein kinase) is one of the most important molecular energy sensors in eukaryotic cells. AMPK activity is able to control a wide variety of metabolic processes connecting cellular metabolism with energy availability. Autophagy is an evolutionarily conserved catabolic pathway whose activity provides energy and basic building blocks for the synthesis of new biomolecules. Given the importance of autophagic degradation for energy production in situations of nutrient scarcity, it seems logical that eukaryotic cells have developed multiple molecular links between AMPK signaling and autophagy regulation. In this review, we will discuss the importance of AMPK activity for diverse aspects of cellular metabolism, and how AMPK modulates autophagic degradation and adapts it to cellular energetic status. We will explain how AMPK-mediated signaling is mechanistically involved in autophagy regulation both through specific phosphorylation of autophagy-relevant proteins or by indirectly impacting in the activity of additional autophagy regulators.
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Affiliation(s)
- Isaac Tamargo-Gómez
- Instituto de Investigación Sanitaria del Principado de Asturias, 33011 Oviedo, Spain.
- Departamento de Biología Funcional, Universidad de Oviedo, 33011 Oviedo, Spain.
| | - Guillermo Mariño
- Instituto de Investigación Sanitaria del Principado de Asturias, 33011 Oviedo, Spain.
- Departamento de Biología Funcional, Universidad de Oviedo, 33011 Oviedo, Spain.
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Gallagher LE, Williamson LE, Chan EY. Advances in Autophagy Regulatory Mechanisms. Cells 2016; 5:E24. [PMID: 27187479 DOI: 10.3390/cells5020024] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 04/20/2016] [Accepted: 05/05/2016] [Indexed: 12/19/2022] Open
Abstract
Autophagy plays a critical role in cell metabolism by degrading and recycling internal components when challenged with limited nutrients. This fundamental and conserved mechanism is based on a membrane trafficking pathway in which nascent autophagosomes engulf cytoplasmic cargo to form vesicles that transport their content to the lysosome for degradation. Based on this simple scheme, autophagy modulates cellular metabolism and cytoplasmic quality control to influence an unexpectedly wide range of normal mammalian physiology and pathophysiology. In this review, we summarise recent advancements in three broad areas of autophagy regulation. We discuss current models on how autophagosomes are initiated from endogenous membranes. We detail how the uncoordinated 51-like kinase (ULK) complex becomes activated downstream of mechanistic target of rapamycin complex 1 (MTORC1). Finally, we summarise the upstream signalling mechanisms that can sense amino acid availability leading to activation of MTORC1.
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Wesselborg S, Stork B. Autophagy signal transduction by ATG proteins: from hierarchies to networks. Cell Mol Life Sci 2015; 72:4721-57. [PMID: 26390974 PMCID: PMC4648967 DOI: 10.1007/s00018-015-2034-8] [Citation(s) in RCA: 163] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 08/13/2015] [Accepted: 08/31/2015] [Indexed: 02/07/2023]
Abstract
Autophagy represents an intracellular degradation process which is involved in both cellular homeostasis and disease settings. In the last two decades, the molecular machinery governing this process has been characterized in detail. To date, several key factors regulating this intracellular degradation process have been identified. The so-called autophagy-related (ATG) genes and proteins are central to this process. However, several additional molecules contribute to the outcome of an autophagic response. Several review articles describing the molecular process of autophagy have been published in the recent past. In this review article we would like to add the most recent findings to this knowledge, and to give an overview of the network character of the autophagy signaling machinery.
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Affiliation(s)
- Sebastian Wesselborg
- Institute of Molecular Medicine I, Heinrich-Heine-University, Universitätsstr. 1, Building 23.12, 40225, Düsseldorf, Germany
| | - Björn Stork
- Institute of Molecular Medicine I, Heinrich-Heine-University, Universitätsstr. 1, Building 23.12, 40225, Düsseldorf, Germany.
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Giatromanolaki A, Sivridis E, Mitrakas A, Kalamida D, Zois CE, Haider S, Piperidou C, Pappa A, Gatter KC, Harris AL, Koukourakis MI. Autophagy and lysosomal related protein expression patterns in human glioblastoma. Cancer Biol Ther 2015; 15:1468-78. [PMID: 25482944 DOI: 10.4161/15384047.2014.955719] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Glioblastoma cells are resistant to apoptotic stimuli with autophagic death prevailing under cytotoxic stress. Autophagy interfering agents may represent a new strategy to test in combination with chemo-radiation. We investigated the patterns of expression of autophagy related proteins (LC3A, LC3B, p62, Beclin 1, ULK1 and ULK2) in a series of patients treated with post-operative radiotherapy. Experiments with glioblastoma cell lines (T98 and U87) were also performed to assess autophagic response under conditions simulating the adverse intratumoral environment. Glioblastomas showed cytoplasmic overexpression of autophagic proteins in a varying extent, so that cases could be grouped into low and high expression groups. 10/23, 5/23, 13/23, 5/23, 8/23 and 9/23 cases examined showed extensive expression of LC3A, LC3B, Beclin 1, Ulk 1, Ulk 2 and p62, respectively. Lysosomal markers Cathepsin D and LAMP2a, as well as the lyososomal biogenesis transcription factor TFEB were frequently overexpressed in glioblastomas (10/23, 11/23, and 10/23 cases, respectively). TFEB was directly linked with PTEN, Cathepsin D, HIF1α, LC3B, Beclin 1 and p62 expression. PTEN was also significantly related with LC3B but not LC3A expression, in both immunohistochemistry and gene expression analysis. Confocal microscopy in T98 and U87 cell lines showed distinct identity of LC3A and LC3B autophagosomes. The previously reported stone-like structure (SLS) pattern of LC3 expression was related with prognosis. SLS were inducible in glioblastoma cell lines under exposure to acidic conditions and 2DG mediated glucose antagonism. The present study provides the basis for autophagic characterization of human glioblastoma for further translational studies and targeted therapy trials.
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Affiliation(s)
- Alexandra Giatromanolaki
- a Department of Pathology ; Democritus University of Thrace/University General Hospital of Alexandroupolis ; Alexandroupolis , Greece
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Nagy P, Hegedűs K, Pircs K, Varga Á, Juhász G. Different effects of Atg2 and Atg18 mutations on Atg8a and Atg9 trafficking during starvation in Drosophila. FEBS Lett 2013; 588:408-13. [PMID: 24374083 PMCID: PMC3928829 DOI: 10.1016/j.febslet.2013.12.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 12/06/2013] [Accepted: 12/10/2013] [Indexed: 01/13/2023]
Abstract
Atg9 and Atg18 are required for autophagy upstream of Atg8a, unlike Atg2. Atg9 accumulates on Ref(2)P aggregates in Atg8a, Atg7 and Atg2 mutants. Ultrastructurally, Atg9 vesicles cluster around Ref(2)P aggregates in stalled PAS. Atg9 does not accumulate on Ref(2)P upon loss of Atg18 or Vps34, while FIP200 does. Atg18 simultaneously interacts with both Atg9 and Ref(2)P.
The Atg2–Atg18 complex acts in parallel to Atg8 and regulates Atg9 recycling from phagophore assembly site (PAS) during autophagy in yeast. Here we show that in Drosophila, both Atg9 and Atg18 are required for Atg8a puncta formation, unlike Atg2. Selective autophagic degradation of ubiquitinated proteins is mediated by Ref(2)P/p62. The transmembrane protein Atg9 accumulates on refractory to Sigma P (Ref(2)P) aggregates in Atg7, Atg8a and Atg2 mutants. No accumulation of Atg9 is seen on Ref(2)P in cells lacking Atg18 or Vps34 lipid kinase function, while the Atg1 complex subunit FIP200 is recruited. The simultaneous interaction of Atg18 with both Atg9 and Ref(2)P raises the possibility that Atg18 may facilitate selective degradation of ubiquitinated protein aggregates by autophagy. Ref(2)Pphysically interacts with Atg18 by anti tag coimmunoprecipitation (View interaction) Atg18physically interacts with Atg2 by anti tag coimmunoprecipitation (View interaction) CG8678physically interacts with Atg2 by anti tag coimmunoprecipitation (View interaction) Atg18physically interacts with atg9 by anti tag coimmunoprecipitation (View interaction)
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Affiliation(s)
- Péter Nagy
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest H-1117, Hungary
| | - Krisztina Hegedűs
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest H-1117, Hungary
| | - Karolina Pircs
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest H-1117, Hungary
| | - Ágnes Varga
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest H-1117, Hungary
| | - Gábor Juhász
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest H-1117, Hungary.
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Abstract
Cells require the ability to rapidly detect decreases in concentrations of free amino acids so that homeostatic mechanisms, including autophagy, can be engaged to replenish amino acids. Amino acids are transported into cells where it is generally accepted that they are detected by an intracellular sensor. We now show that the cell surface G protein coupled receptor (GPCR) TAS1R1-TAS1R3 (T1R1-T1R3) can sense extracellular amino acids, activate MTORC1, and inhibit autophagy. This receptor is expressed in most tissues and fasted TAS1R3 (-/-) mice have increased autophagy in the heart, skeletal muscle and liver.
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Affiliation(s)
- Eric M Wauson
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA
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