251
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Dynamics of autophagosome formation: a pulse and a sequence of waves. Biochem Soc Trans 2015; 42:1389-95. [PMID: 25233420 DOI: 10.1042/bst20140183] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Autophagosomes form in eukaryotic cells in response to starvation or to other stress conditions brought about by the unwanted presence in the cytosol of pathogens, damaged organelles or aggregated protein assemblies. The uniqueness of autophagosomes is that they form de novo and that they are the only double-membraned vesicles known in cells, having arisen from flat membrane sheets which have expanded and self-closed. The various steps describing their formation as well as most of the protein and lipid components involved have been identified. Furthermore, the hierarchical relationships among the components are well documented, and the mechanistic rationale for some of these hierarchies has been revealed. In the present review, we try to provide a current view of the process of autophagosome formation in mammalian cells, emphasizing along the way gaps in our knowledge that need additional work.
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252
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Usategui-Martín R, García-Aparicio J, Corral-Gudino L, Calero-Paniagua I, Del Pino-Montes J, González Sarmiento R. Polymorphisms in autophagy genes are associated with paget disease of bone. PLoS One 2015; 10:e0128984. [PMID: 26030385 PMCID: PMC4452234 DOI: 10.1371/journal.pone.0128984] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 05/04/2015] [Indexed: 11/19/2022] Open
Abstract
Paget disease of bone (PDB) is a focal bone disorder affecting the skeleton segmentally. The main alteration resides in osteoclasts that increase in size, number and activity. Many osteoclasts have cytoplasmic inclusions that have been associated with protein aggregates, increasing the evidences of a possible deregulation of autophagy in the development of the PDB. Autophagy starts with encapsulation of the target into a double-membrane-bound structure called an “autophagosome.” It has been reported that at least 18 ATG genes (autophagy-related genes) are involved in autophagosome formation. We have studied the distribution of genotypes of the ATG2B rs3759601, ATG16L1 rs2241880, ATG10 rs1864183 and ATG5 rs2245214 polymorphisms in a Spanish cohort of subjects with PDB and compared with healthy subjects. Our results show that being a carrier of the C allele of the ATG16L1 rs2241880 and the G allele of ATG5 rs2245214 polymorphisms were associated with an increased risk of developing PDB, whereas being a carrier of the T allele of ATG10 rs1864183 polymorphism decreased the risk of suffering the disease in our series. This is the first report that shows an association between autophagy and Paget Disease of Bone and requires further confirmation in other series.
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Affiliation(s)
- Ricardo Usategui-Martín
- Unidad de Medicina Molecular-IBSAL, Departamento de Medicina, Universidad de Salamanca-Hospital Universitario de Salamanca-CSIC, Salamanca, España
| | - Judith García-Aparicio
- Servicio de Medicina interna-IBSAL, Hospital Universitario de Salamanca Universidad de Salamanca CSIC, Salamanca, España
| | - Luis Corral-Gudino
- Servicio de Medicina interna-IBSAL, Hospital Universitario de Salamanca Universidad de Salamanca CSIC, Salamanca, España
| | - Ismael Calero-Paniagua
- Servicio de Reumatología-IBSAL, Hospital Universitario de Salamanca-Universidad de Salamanca-CSIC, Salamanca, España
| | - Javier Del Pino-Montes
- Servicio de Reumatología-IBSAL, Hospital Universitario de Salamanca-Universidad de Salamanca-CSIC, Salamanca, España
| | - Rogelio González Sarmiento
- Unidad de Medicina Molecular-IBSAL, Departamento de Medicina, Universidad de Salamanca-Hospital Universitario de Salamanca-CSIC, Salamanca, España
- Instituto de Biología Molecular y Celular del Cáncer (IBMCC), Universidad de Salamanca-CSIC, Salamanca, España
- * E-mail:
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253
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Farhan H. Systems biology of the secretory pathway: what have we learned so far? Biol Cell 2015; 107:205-17. [PMID: 25756903 DOI: 10.1111/boc.201400065] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 03/04/2015] [Indexed: 12/26/2022]
Abstract
Several RNAi screens were performed in search for regulators of the secretory pathway. These screens were performed in different organisms and cell lines and relied on different readouts. Therefore, they have only little overlap among their hits, leading to the question of what we have learned from this approach so far and how these screens contributed towards an integrative understanding of the endomembrane system. The aim of this review is to revisit these screens and discuss their strengths and weaknesses as well as potential reasons for their failure to overlap with each other. As with secretory trafficking, RNAi screens were also performed on other cellular processes such as cell migration and autophagy, both of which were shown to be intimately linked to secretion. Another aim of this review is to compare the outcome of the RNAi screens on secretion, autophagy and cell migration and ask whether the functional genomic approaches have uncovered potential mechanistic insights into the links between these processes.
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Affiliation(s)
- Hesso Farhan
- Department of Biology, University of Konstanz, Konstanz, Germany.,Biotechnology Institute Thurgau, Kreuzlingen, Switzerland
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254
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Goold R, McKinnon C, Tabrizi SJ. Prion degradation pathways: Potential for therapeutic intervention. Mol Cell Neurosci 2015; 66:12-20. [PMID: 25584786 PMCID: PMC4503822 DOI: 10.1016/j.mcn.2014.12.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 12/16/2014] [Indexed: 12/18/2022] Open
Abstract
Prion diseases are fatal neurodegenerative disorders. Pathology is closely linked to the misfolding of native cellular PrP(C) into the disease-associated form PrP(Sc) that accumulates in the brain as disease progresses. Although treatments have yet to be developed, strategies aimed at stimulating the degradation of PrP(Sc) have shown efficacy in experimental models of prion disease. Here, we describe the cellular pathways that mediate PrP(Sc) degradation and review possible targets for therapeutic intervention. This article is part of a Special Issue entitled 'Neuronal Protein'.
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Affiliation(s)
- Rob Goold
- Department of Neurodegenerative Disease, UCL Institute of Neurology, University College London, United Kingdom
| | - Chris McKinnon
- Department of Neurodegenerative Disease, UCL Institute of Neurology, University College London, United Kingdom
| | - Sarah J Tabrizi
- Department of Neurodegenerative Disease, UCL Institute of Neurology, University College London, United Kingdom.
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255
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p53-mediated autophagic regulation: A prospective strategy for cancer therapy. Cancer Lett 2015; 363:101-7. [PMID: 25896632 DOI: 10.1016/j.canlet.2015.04.014] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 04/13/2015] [Accepted: 04/14/2015] [Indexed: 12/25/2022]
Abstract
Autophagy is a major catabolic process that degrades and recycles cytosolic components in autophagosomes, which fuse with lysosomes. This process enables starving cells to sustain their energy requirements and metabolic states, thus facilitating their survival, especially in cancer pathogenesis. The regulation of autophagy is quite intricate. It involves a series of signaling cascades including p53, known as the best-characterized tumor suppressor protein. Recent reports have indicated that p53 plays dual roles in regulating autophagy depending on its subcellular localization. Nuclear p53 facilitates autophagy by transactivating its target genes, whereas cytoplasmic p53 mainly inhibits autophagy through extranuclear, transcription-independent mechanisms. The relationship between autophagy and neoplasia is complicated. It may be intrinsically associated with the functional status of p53, but this is not clearly elucidated. This review focuses on the role of p53 as a master regulator of autophagy. We conclude that the contextual role of autophagy in cancer, which could be switched by p53 status, is expected to be developed into a new anticancer therapeutic approach.
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256
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Köfinger J, Ragusa MJ, Lee IH, Hummer G, Hurley JH. Solution structure of the Atg1 complex: implications for the architecture of the phagophore assembly site. Structure 2015; 23:809-818. [PMID: 25817386 DOI: 10.1016/j.str.2015.02.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 01/29/2015] [Accepted: 02/24/2015] [Indexed: 10/23/2022]
Abstract
The biogenesis of autophagosomes commences at the phagophore assembly site (PAS), a protein-vesicle ultrastructure that is organized by the Atg1 complex. The Atg1 complex consists of the Atg1 protein kinase, the intrinsically disordered region-rich Atg13, and the dimeric double crescent-shaped Atg17-Atg31-Atg29 subcomplex. We show that the PAS contains a relatively uniform ∼28 copies of Atg17, and upon autophagy induction, similar numbers of Atg1 and Atg13 molecules. We then apply ensemble refinement of small-angle X-ray scattering to determine the solution structures of the Atg1-Atg13 and Atg17-Atg31-Atg29 subcomplexes and the Atg1 complex, using a trimmed minipentamer tractable to biophysical studies. We observe tetramers of Atg1 pentamers that assemble via Atg17-Atg31-Atg29. This leads to a model for the higher organization of the Atg1 complex in PAS scaffolding.
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Affiliation(s)
- Jürgen Köfinger
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany.
| | - Michael J Ragusa
- Department of Molecular and Cell Biology, California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA
| | - Il-Hyung Lee
- Department of Molecular and Cell Biology, California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - James H Hurley
- Department of Molecular and Cell Biology, California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA; Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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257
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Núñez A, Dulude D, Jbel M, Rokeach LA. Calnexin is essential for survival under nitrogen starvation and stationary phase in Schizosaccharomyces pombe. PLoS One 2015; 10:e0121059. [PMID: 25803873 PMCID: PMC4372366 DOI: 10.1371/journal.pone.0121059] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 02/06/2015] [Indexed: 12/04/2022] Open
Abstract
Cell fate is determined by the balance of conserved molecular mechanisms regulating death (apoptosis) and survival (autophagy). Autophagy is a process by which cells recycle their organelles and macromolecules through degradation within the vacuole in yeast and plants, and lysosome in metazoa. In the yeast Schizosaccharomyces pombe, autophagy is strongly induced under nitrogen starvation and in aging cells. Previously, we demonstrated that calnexin (Cnx1p), a highly conserved transmembrane chaperone of the endoplasmic reticulum (ER), regulates apoptosis under ER stress or inositol starvation. Moreover, we showed that in stationary phase, Cnx1p is cleaved into two moieties, L_Cnx1p and S_Cnx1p. Here, we show that the processing of Cnx1p is regulated by autophagy, induced by nitrogen starvation or cell aging. The cleavage of Cnx1p involves two vacuolar proteases: Isp6, which is essential for autophagy, and its paralogue Psp3. Blocking autophagy through the knockout of autophagy-related genes (atg) results in inhibition of both, the cleavage and the trafficking of Cnx1p from the ER to the vacuole. We demonstrate that Cnx1p is required for cell survival under nitrogen-starvation and in chronological aging cultures. The death of the mini_cnx1 mutant (overlapping S_cnx1p) cells is accompanied by accumulation of high levels of reactive-oxygen species (ROS), a slowdown in endocytosis and severe cell-wall defects. Moreover, mutant cells expressing only S_Cnx1p showed cell wall defects. Co-expressing mutant overlapping the L_Cnx1p and S_Cnx1p cleavage products reverses the death, ROS phenotype and cell wall defect to wild-type levels. As it is involved in both apoptosis and autophagy, Cnx1p could be a nexus for the crosstalk between these pro-death and pro-survival mechanisms. Ours, and observations in mammalian systems, suggest that the multiple roles of calnexin depend on its sub-cellular localization and on its cleavage. The use of S. pombe should assist in further shedding light on the multiple roles of calnexin.
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Affiliation(s)
- Andrés Núñez
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada
| | - Dominic Dulude
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada
| | - Mehdi Jbel
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada
| | - Luis A. Rokeach
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec, Canada
- * E-mail:
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258
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Perluigi M, Di Domenico F, Butterfield DA. mTOR signaling in aging and neurodegeneration: At the crossroad between metabolism dysfunction and impairment of autophagy. Neurobiol Dis 2015; 84:39-49. [PMID: 25796566 DOI: 10.1016/j.nbd.2015.03.014] [Citation(s) in RCA: 230] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 03/09/2015] [Accepted: 03/12/2015] [Indexed: 02/09/2023] Open
Abstract
Compelling evidence indicates that the mammalian target of rapamycin (mTOR) signaling pathway is involved in cellular senescence, organismal aging and age-dependent diseases. mTOR is a conserved serine/threonine kinase that is known to be part of two different protein complexes: mTORC1 and mTORC2, which differ in some components and in upstream and downstream signalling. In multicellular organisms, mTOR regulates cell growth and metabolism in response to nutrients, growth factors and cellular energy conditions. Growing studies highlight that disturbance in mTOR signalling in the brain affects multiple pathways including glucose metabolism, energy production, mitochondrial function, cell growth and autophagy. All these events are key players in age-related cognitive decline such as development of Alzheimer disease (AD). The current review discusses the main regulatory roles of mTOR signalling in the brain, in particular focusing on autophagy, glucose metabolism and mitochondrial functions. Targeting mTOR in the CNS can offer new prospective for drug discovery; however further studies are needed for a comprehensive understanding of mTOR, which lies at the crossroads of multiple signals involved in AD etiology and pathogenesis.
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Affiliation(s)
- Marzia Perluigi
- Department of Biochemical Sciences, Sapienza University of Rome, Italy.
| | - Fabio Di Domenico
- Department of Biochemical Sciences, Sapienza University of Rome, Italy
| | - D Allan Butterfield
- Sanders-Brown Centre of Aging, University of Kentucky, Lexington KY, USA; Department of Chemistry, University of Kentucky, Lexington KY, USA
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259
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Up-regulation of lysosomal TRPML1 channels is essential for lysosomal adaptation to nutrient starvation. Proc Natl Acad Sci U S A 2015; 112:E1373-81. [PMID: 25733853 DOI: 10.1073/pnas.1419669112] [Citation(s) in RCA: 161] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Upon nutrient starvation, autophagy digests unwanted cellular components to generate catabolites that are required for housekeeping biosynthesis processes. A complete execution of autophagy demands an enhancement in lysosome function and biogenesis to match the increase in autophagosome formation. Here, we report that mucolipin-1 (also known as TRPML1 or ML1), a Ca(2+) channel in the lysosome that regulates many aspects of lysosomal trafficking, plays a central role in this quality-control process. By using Ca(2+) imaging and whole-lysosome patch clamping, lysosomal Ca(2+) release and ML1 currents were detected within hours of nutrient starvation and were potently up-regulated. In contrast, lysosomal Na(+)-selective currents were not up-regulated. Inhibition of mammalian target of rapamycin (mTOR) or activation of transcription factor EB (TFEB) mimicked a starvation effect in fed cells. The starvation effect also included an increase in lysosomal proteostasis and enhanced clearance of lysosomal storage, including cholesterol accumulation in Niemann-Pick disease type C (NPC) cells. However, this effect was not observed when ML1 was pharmacologically inhibited or genetically deleted. Furthermore, overexpression of ML1 mimicked the starvation effect. Hence, lysosomal adaptation to environmental cues such as nutrient levels requires mTOR/TFEB-dependent, lysosome-to-nucleus regulation of lysosomal ML1 channels and Ca(2+) signaling.
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260
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Abstract
The formation of the autophagosome, a landmark event in autophagy, is accomplished by the concerted actions of Atg proteins. The initial step of starvation-induced autophagy in yeast is the assembly of the Atg1 complex, which, with the help of other Atg groups, recruits Atg conjugation systems and initiates the formation of the autophagosome. In this review, we describe from a structural-biological point of view the structure, interaction, and molecular roles of Atg proteins, especially those in the Atg1 complex and in the Atg conjugation systems.
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Affiliation(s)
- Nobuo N Noda
- Institute of Microbial Chemistry (BIKAKEN), Tokyo 141-0021, Japan;
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261
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Bhattacharya A, Eissa NT. Autophagy as a Stress Response Pathway in the Immune System. Int Rev Immunol 2015; 34:382-402. [DOI: 10.3109/08830185.2014.999156] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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262
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Meng SF, Mao WP, Wang F, Liu XQ, Shao LL. The relationship between Cd-induced autophagy and lysosomal activation in WRL-68 cells. J Appl Toxicol 2015; 35:1398-405. [DOI: 10.1002/jat.3114] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 11/30/2014] [Accepted: 12/10/2014] [Indexed: 01/14/2023]
Affiliation(s)
- Su-Fang Meng
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences; Nanjing Normal University; Nanjing Jiangsu People's Republic of China
| | - Wei-Ping Mao
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences; Nanjing Normal University; Nanjing Jiangsu People's Republic of China
| | - Fang Wang
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences; Nanjing Normal University; Nanjing Jiangsu People's Republic of China
| | - Xiao-Qian Liu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences; Nanjing Normal University; Nanjing Jiangsu People's Republic of China
| | - Luan-Luan Shao
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences; Nanjing Normal University; Nanjing Jiangsu People's Republic of China
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263
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Dany M, Ogretmen B. Ceramide induced mitophagy and tumor suppression. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2834-45. [PMID: 25634657 DOI: 10.1016/j.bbamcr.2014.12.039] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 12/09/2014] [Accepted: 12/25/2014] [Indexed: 12/11/2022]
Abstract
Sphingolipids are bioactive lipid effectors, which are involved in the regulation of various cellular signaling pathways. Sphingolipids play essential roles in controlling cell inflammation, proliferation, death, migration, senescence, metastasis and autophagy. Alterations in sphingolipid metabolism have been also implicated in many human cancers. Macroautophagy (referred to here as autophagy) is a form of nonselective sequestering of cytosolic materials by double membrane structures, autophagosomes, which can be either protective or lethal for cells. Ceramide, a central molecule of sphingolipid metabolism is involved in the regulation of autophagy at various levels, including the induction of lethal mitophagy, a selective autophagy process to target and eliminate damaged mitochondria. In this review, we focused on recent studies with regard to the regulation of autophagy, in particular lethal mitophagy, by ceramide, and aimed at providing discussion points for various context-dependent roles and mechanisms of action of ceramide in controlling mitophagy.
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Affiliation(s)
- Mohammed Dany
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA; Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, Charleston, SC 29425, USA
| | - Besim Ogretmen
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA; Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas Street, Charleston, SC 29425, USA.
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264
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Campos T, Ziehe J, Palma M, Escobar D, Tapia JC, Pincheira R, Castro AF. Rheb promotes cancer cell survival through p27Kip1-dependent activation of autophagy. Mol Carcinog 2015; 55:220-9. [DOI: 10.1002/mc.22272] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 11/05/2014] [Accepted: 11/26/2014] [Indexed: 12/19/2022]
Affiliation(s)
- Tania Campos
- Departamento de Bioquímica y Biología Molecular; Facultad de Ciencias Biológicas; Laboratorio de Transducción de Señales y Cáncer; Universidad de Concepción; Concepción Chile
| | - Javiera Ziehe
- Departamento de Bioquímica y Biología Molecular; Facultad de Ciencias Biológicas; Laboratorio de Transducción de Señales y Cáncer; Universidad de Concepción; Concepción Chile
| | - Mario Palma
- Departamento de Bioquímica y Biología Molecular; Facultad de Ciencias Biológicas; Laboratorio de Transducción de Señales y Cáncer; Universidad de Concepción; Concepción Chile
| | - David Escobar
- Departamento de Bioquímica y Biología Molecular; Facultad de Ciencias Biológicas; Laboratorio de Transducción de Señales y Cáncer; Universidad de Concepción; Concepción Chile
| | - Julio C. Tapia
- Facultad de Medicina; Laboratorio de Transformación Celular; ICBM; Universidad de Chile; Santiago Chile
| | - Roxana Pincheira
- Departamento de Bioquímica y Biología Molecular; Facultad de Ciencias Biológicas; Laboratorio de Transducción de Señales y Cáncer; Universidad de Concepción; Concepción Chile
| | - Ariel F. Castro
- Departamento de Bioquímica y Biología Molecular; Facultad de Ciencias Biológicas; Laboratorio de Transducción de Señales y Cáncer; Universidad de Concepción; Concepción Chile
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265
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Niso-Santano M, Malik SA, Pietrocola F, Bravo-San Pedro JM, Mariño G, Cianfanelli V, Ben-Younès A, Troncoso R, Markaki M, Sica V, Izzo V, Chaba K, Bauvy C, Dupont N, Kepp O, Rockenfeller P, Wolinski H, Madeo F, Lavandero S, Codogno P, Harper F, Pierron G, Tavernarakis N, Cecconi F, Maiuri MC, Galluzzi L, Kroemer G. Unsaturated fatty acids induce non-canonical autophagy. EMBO J 2015; 34:1025-41. [PMID: 25586377 DOI: 10.15252/embj.201489363] [Citation(s) in RCA: 132] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 12/19/2014] [Indexed: 12/21/2022] Open
Abstract
To obtain mechanistic insights into the cross talk between lipolysis and autophagy, two key metabolic responses to starvation, we screened the autophagy-inducing potential of a panel of fatty acids in human cancer cells. Both saturated and unsaturated fatty acids such as palmitate and oleate, respectively, triggered autophagy, but the underlying molecular mechanisms differed. Oleate, but not palmitate, stimulated an autophagic response that required an intact Golgi apparatus. Conversely, autophagy triggered by palmitate, but not oleate, required AMPK, PKR and JNK1 and involved the activation of the BECN1/PIK3C3 lipid kinase complex. Accordingly, the downregulation of BECN1 and PIK3C3 abolished palmitate-induced, but not oleate-induced, autophagy in human cancer cells. Moreover, Becn1(+/-) mice as well as yeast cells and nematodes lacking the ortholog of human BECN1 mounted an autophagic response to oleate, but not palmitate. Thus, unsaturated fatty acids induce a non-canonical, phylogenetically conserved, autophagic response that in mammalian cells relies on the Golgi apparatus.
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Affiliation(s)
- Mireia Niso-Santano
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Shoaib Ahmad Malik
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France Government College University, Faisalabad, Pakistan
| | - Federico Pietrocola
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France Université Paris Sud/Paris 11, Le Kremlin Bicêtre, France
| | - José Manuel Bravo-San Pedro
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Guillermo Mariño
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Valentina Cianfanelli
- Department of Biology, University of Rome 'Tor Vergata', Rome, Italy Unit of Cell Stress and Survival, Danish Cancer Society Research Center, Copenhagen, Denmark
| | - Amena Ben-Younès
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Rodrigo Troncoso
- Advanced Center for Chronic Disease (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences/Faculty of Medicine, University of Chile, Santiago, Chile Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile Faculty of Medicine, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile
| | - Maria Markaki
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Valentina Sica
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France Université Paris Sud/Paris 11, Le Kremlin Bicêtre, France
| | - Valentina Izzo
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Kariman Chaba
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Chantal Bauvy
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France INSERM, U1151, Paris, France Institut Necker Enfants-Malades, Paris, France
| | - Nicolas Dupont
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France INSERM, U1151, Paris, France Institut Necker Enfants-Malades, Paris, France
| | - Oliver Kepp
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France INSERM, U1138, Paris, France Cell Biology & Metabolomics Platforms, Gustave Roussy Comprehensive Cancer Center, Villejuif, France
| | - Patrick Rockenfeller
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria BioTechMed Graz, Graz, Austria
| | - Heimo Wolinski
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria BioTechMed Graz, Graz, Austria
| | - Frank Madeo
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria BioTechMed Graz, Graz, Austria
| | - Sergio Lavandero
- Advanced Center for Chronic Disease (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences/Faculty of Medicine, University of Chile, Santiago, Chile Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile Faculty of Medicine, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile Department of Internal Medicine (Cardiology Division), University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Patrice Codogno
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France INSERM, U1151, Paris, France Institut Necker Enfants-Malades, Paris, France
| | - Francis Harper
- Gustave Roussy Comprehensive Cancer Center, Villejuif, France CNRS, UMR8122, Villejuif, France
| | - Gérard Pierron
- Gustave Roussy Comprehensive Cancer Center, Villejuif, France CNRS, UMR8122, Villejuif, France
| | - Nektarios Tavernarakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Greece
| | - Francesco Cecconi
- Department of Biology, University of Rome 'Tor Vergata', Rome, Italy Unit of Cell Stress and Survival, Danish Cancer Society Research Center, Copenhagen, Denmark Laboratory of Molecular Neuroembryology, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Maria Chiara Maiuri
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Lorenzo Galluzzi
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Guido Kroemer
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France INSERM, U1138, Paris, France Université Paris Descartes, Sorbonne Paris Cité, Paris, France Cell Biology & Metabolomics Platforms, Gustave Roussy Comprehensive Cancer Center, Villejuif, France Pôle de Biologie, Hôpital Européen Georges Pompidou, AP-HP, Paris, France
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266
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Teaching the basics of autophagy and mitophagy to redox biologists--mechanisms and experimental approaches. Redox Biol 2015; 4:242-59. [PMID: 25618581 PMCID: PMC4803799 DOI: 10.1016/j.redox.2015.01.003] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 12/24/2014] [Accepted: 01/01/2015] [Indexed: 02/08/2023] Open
Abstract
Autophagy is a lysosomal mediated degradation activity providing an essential mechanism for recycling cellular constituents, and clearance of excess or damaged lipids, proteins and organelles. Autophagy involves more than 30 proteins and is regulated by nutrient availability, and various stress sensing signaling pathways. This article provides an overview of the mechanisms and regulation of autophagy, its role in health and diseases, and methods for its measurement. Hopefully this teaching review together with the graphic illustrations will be helpful for instructors teaching graduate students who are interested in grasping the concepts and major research areas and introducing recent developments in the field. mTOR, Beclin–VPS34, LC3 homologs, and adaptor proteins in autophagy. Autophagosomal membranes may derive from multiple sources. Autophagosomal–lysosomal fusion contributes to the control of autophagic flux. Assess autophagy by autophagosomal and protein turnover, and morphological alterations. Autophagy adysfunction in cancer, aging, neurodegeneration and infection.
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267
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Abstract
Most neurodegenerative diseases that afflict humans are associated with the intracytoplasmic deposition of aggregate-prone proteins in neurons. Autophagy is a powerful process for removing such proteins. In this Review, we consider how certain neurodegenerative diseases may be associated with impaired autophagy and how this may affect pathology. We also discuss how autophagy induction may be a plausible therapeutic strategy for some conditions and review studies in various models that support this hypothesis. Finally, we briefly describe some of the signaling pathways that may be amenable to therapeutic targeting for these goals.
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268
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Ryter SW, Choi AMK. Autophagy in lung disease pathogenesis and therapeutics. Redox Biol 2015; 4:215-25. [PMID: 25617802 PMCID: PMC4803789 DOI: 10.1016/j.redox.2014.12.010] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 12/18/2014] [Accepted: 12/18/2014] [Indexed: 12/16/2022] Open
Abstract
Autophagy, a cellular pathway for the degradation of damaged organelles and proteins, has gained increasing importance in human pulmonary diseases, both as a modulator of pathogenesis and as a potential therapeutic target. In this pathway, cytosolic cargos are sequestered into autophagosomes, which are delivered to the lysosomes where they are enzymatically degraded and then recycled as metabolic precursors. Autophagy exerts an important effector function in the regulation of inflammation, and immune system functions. Selective pathways for autophagic degradation of cargoes may have variable significance in disease pathogenesis. Among these, the autophagic clearance of bacteria (xenophagy) may represent a crucial host defense mechanism in the pathogenesis of sepsis and inflammatory diseases. Our recent studies indicate that the autophagic clearance of mitochondria, a potentially protective program, may aggravate the pathogenesis of chronic obstructive pulmonary disease by activating cell death programs. We report similar findings with respect to the autophagic clearance of cilia components, which can contribute to airways dysfunction in chronic lung disease. In certain diseases such as pulmonary hypertension, autophagy may confer protection by modulating proliferation and cell death. In other disorders, such as idiopathic pulmonary fibrosis and cystic fibrosis, impaired autophagy may contribute to pathogenesis. In lung cancer, autophagy has multiple consequences by limiting carcinogenesis, modulating therapeutic effectiveness, and promoting tumor cell survival. In this review we highlight the multiple functions of autophagy and its selective autophagy subtypes that may be of significance to the pathogenesis of human disease, with an emphasis on lung disease and therapeutics. Autophagy may impact the pathogenesis of pulmonary diseases. Mitophagy may exert deleterious effects in the pathogenesis of COPD. Autophagy can exert pleiotropic effects in lung cancer. Targeting autophagy may represent a promising therapeutic strategy in human diseases.
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Affiliation(s)
- Stefan W Ryter
- Joan and Sanford I. Weill Department of Medicine, Weill Cornell Medical College and New York-Presbyterian Hospital, New York, NY, USA.
| | - Augustine M K Choi
- Joan and Sanford I. Weill Department of Medicine, Weill Cornell Medical College and New York-Presbyterian Hospital, New York, NY, USA
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269
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Yano K, Yanagisawa T, Mukae K, Niwa Y, Inoue Y, Moriyasu Y. Dissection of autophagy in tobacco BY-2 cells under sucrose starvation conditions using the vacuolar H(+)-ATPase inhibitor concanamycin A and the autophagy-related protein Atg8. PLANT SIGNALING & BEHAVIOR 2015; 10:e1082699. [PMID: 26368310 PMCID: PMC4883836 DOI: 10.1080/15592324.2015.1082699] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 08/08/2015] [Indexed: 05/08/2023]
Abstract
Tobacco BY-2 cells undergo autophagy in sucrose-free culture medium, which is the process mostly responsible for intracellular protein degradation under these conditions. Autophagy was inhibited by the vacuolar H(+)-ATPase inhibitors concanamycin A and bafilomycin A1, which caused the accumulation of autophagic bodies in the central vacuoles. Such accumulation did not occur in the presence of the autophagy inhibitor 3-methyladenine, and concanamycin in turn inhibited the accumulation of autolysosomes in the presence of the cysteine protease inhibitor E-64c. Electron microscopy revealed not only that the autophagic bodies were accumulated in the central vacuole, but also that autophagosome-like structures were more frequently observed in the cytoplasm in treatments with concanamycin, suggesting that concanamycin affects the morphology of autophagosomes in addition to raising the pH of the central vacuole. Using BY-2 cells that constitutively express a fusion protein of autophagosome marker protein Atg8 and green fluorescent protein (GFP), we observed the appearance of autophagosomes by fluorescence microscopy, which is a reliable morphological marker of autophagy, and the processing of the fusion protein to GFP, which is a biochemical marker of autophagy. Together, these results suggest the involvement of vacuole type H(+)-ATPase in the maturation step of autophagosomes to autolysosomes in the autophagic process of BY-2 cells. The accumulation of autophagic bodies in the central vacuole by concanamycin is a marker of the occurrence of autophagy; however, it does not necessarily mean that the central vacuole is the site of cytoplasm degradation.
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Affiliation(s)
- Kanako Yano
- Graduate School of Food and Nutritional Sciences; University of Shizuoka; Shizuoka, Japan
| | - Takahiro Yanagisawa
- Department of Regulatory Biology; Graduate School of Science and Engineering; Saitama University; Saitama, Japan
| | - Kyosuke Mukae
- Department of Regulatory Biology; Graduate School of Science and Engineering; Saitama University; Saitama, Japan
| | - Yasuo Niwa
- Graduate School of Food and Nutritional Sciences; University of Shizuoka; Shizuoka, Japan
| | - Yuko Inoue
- Department of Regulatory Biology; Graduate School of Science and Engineering; Saitama University; Saitama, Japan
| | - Yuji Moriyasu
- Department of Regulatory Biology; Graduate School of Science and Engineering; Saitama University; Saitama, Japan
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270
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Baskaran S, Carlson LA, Stjepanovic G, Young LN, Kim DJ, Grob P, Stanley RE, Nogales E, Hurley JH. Architecture and dynamics of the autophagic phosphatidylinositol 3-kinase complex. eLife 2014; 3. [PMID: 25490155 PMCID: PMC4281882 DOI: 10.7554/elife.05115] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 12/08/2014] [Indexed: 12/31/2022] Open
Abstract
The class III phosphatidylinositol 3-kinase complex I (PI3KC3-C1) that functions in early autophagy consists of the lipid kinase VPS34, the scaffolding protein VPS15, the tumor suppressor BECN1, and the autophagy-specific subunit ATG14. The structure of the ATG14-containing PI3KC3-C1 was determined by single-particle EM, revealing a V-shaped architecture. All of the ordered domains of VPS34, VPS15, and BECN1 were mapped by MBP tagging. The dynamics of the complex were defined using hydrogen–deuterium exchange, revealing a novel 20-residue ordered region C-terminal to the VPS34 C2 domain. VPS15 organizes the complex and serves as a bridge between VPS34 and the ATG14:BECN1 subcomplex. Dynamic transitions occur in which the lipid kinase domain is ejected from the complex and VPS15 pivots at the base of the V. The N-terminus of BECN1, the target for signaling inputs, resides near the pivot point. These observations provide a framework for understanding the allosteric regulation of lipid kinase activity. DOI:http://dx.doi.org/10.7554/eLife.05115.001 To survive starvation and other hard times, cells have developed a unique recycling strategy: they can scavenge the resources they need from within the cell itself. To do this, the cell forms a double-layered envelope around particular sections of the cell to seal them off from the rest. Then, the contents of the envelope are taken apart and the resulting raw materials are sent elsewhere in the cell where they can be used as required. This process is called autophagy. In more complex organisms like humans, autophagy can have additional roles. One of the key proteins involved in autophagy—called BECN1—suppresses the growth of tumors, and the gene that makes BECN1 is missing in 40–70% of human breast, ovarian, and prostate cancers. Autophagy may also help to prevent Huntington's disease and other similar conditions by stopping disease-causing proteins or broken cell parts from building up inside brain cells. The BECN1 protein does not work alone. Instead, it becomes part of a group, or ‘complex’, of several proteins that are required to form the envelope made during autophagy. However, the three-dimensional structure of the protein complex is unclear. Baskaran et al. used electron microscopy and other techniques to investigate this structure and found that the complex forms a V shape with two arms, which is held together by its largest protein, VPS15. This protein also acts as a bridge between BECN1 and another protein that is a target for new cancer drugs, called VPS34. Next, Baskaran et al. used a different set of techniques to determine how the complex moves. This revealed that many of the connections between proteins in the complex are flexible. However, one of the arms is inflexible and this limits the ability of the VPS34 protein to move. Understanding this structural constraint may help us to design drugs that are able to target the protein complex more efficiently. DOI:http://dx.doi.org/10.7554/eLife.05115.002
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Affiliation(s)
- Sulochanadevi Baskaran
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Lars-Anders Carlson
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Goran Stjepanovic
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Lindsey N Young
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Do Jin Kim
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Patricia Grob
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Robin E Stanley
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
| | - Eva Nogales
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - James H Hurley
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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271
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Karanasios E, Ktistakis NT. Live-cell imaging for the assessment of the dynamics of autophagosome formation: focus on early steps. Methods 2014; 75:54-60. [PMID: 25498007 DOI: 10.1016/j.ymeth.2014.12.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 12/01/2014] [Accepted: 12/03/2014] [Indexed: 12/22/2022] Open
Abstract
Autophagy is a cytosolic degradative pathway, which through a series of complicated membrane rearrangements leads to the formation of a unique double membrane vesicle, the autophagosome. The use of fluorescent proteins has allowed visualizing the autophagosome formation in live cells and in real time, almost 40 years after electron microscopy studies observed these structures for the first time. In the last decade, live-cell imaging has been extensively used to study the dynamics of autophagosome formation in cultured mammalian cells. Hereby we will discuss how the live-cell imaging studies have tried to settle the debate about the origin of the autophagosome membrane and how they have described the way different autophagy proteins coordinate in space and time in order to drive autophagosome formation.
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272
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Trans-Golgi protein p230/golgin-245 is involved in phagophore formation. Biochem Biophys Res Commun 2014; 456:275-81. [PMID: 25436429 DOI: 10.1016/j.bbrc.2014.11.071] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 11/19/2014] [Indexed: 11/24/2022]
Abstract
p230/golgin-245 is a trans-Golgi coiled-coil protein that is known to participate in regulatory transport from the trans-Golgi network (TGN) to the cell surface. We investigated the role of p230 and its interacting protein, microtubule actin crosslinking protein 1 (MACF1), in amino acid starvation-induced membrane transport. p230 or MACF1 knock-down (KD) cells failed to increase the autophagic flow rate and the number of microtubule-associated protein 1 light chain 3 (LC3)-positive puncta under starvation conditions. Loss of p230 or MACF1 impaired mAtg9 recruitment to peripheral phagophores from the TGN, which was observed in the early step of autophagosome formation. Overexpression of the p230-binding domain of MACF1 resulted in the inhibition of mAtg9 trafficking in starvation conditions as in p230-KD or MACF1-KD cells. These results indicate that p230 and MACF1 cooperatively play an important role in the formation of phagophore through starvation-induced transport of mAtg9-containing membranes from the TGN. In addition, p230 itself was detected in autophagosomes/autolysosome with p62 or LC3 during autophagosome biogenesis. Thus, p230 is an important molecule in phagophore formation, although it remains unclear whether p230 has any role in late steps of autophagy.
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273
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Ge L, Zhang M, Schekman R. Phosphatidylinositol 3-kinase and COPII generate LC3 lipidation vesicles from the ER-Golgi intermediate compartment. eLife 2014; 3:e04135. [PMID: 25432021 PMCID: PMC4270069 DOI: 10.7554/elife.04135] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 11/14/2014] [Indexed: 01/01/2023] Open
Abstract
Formation of the autophagosome requires significant membrane input from cellular organelles. However, no direct evidence has been developed to link autophagic factors and the mobilization of membranes to generate the phagophore. Previously, we established a cell-free LC3 lipidation reaction to identify the ER-Golgi intermediate compartment (ERGIC) as a membrane source for LC3 lipidation, a key step of autophagosome biogenesis (Ge et al., eLife 2013; 2:e00947). We now report that starvation activation of autophagic phosphotidylinositol-3 kinase (PI3K) induces the generation of small vesicles active in LC3 lipidation. Subcellular fractionation studies identified the ERGIC as the donor membrane in the generation of small lipidation-active vesicles. COPII proteins are recruited to the ERGIC membrane in starved cells, dependent on active PI3K. We conclude that starvation activates the autophagic PI3K, which in turn induces the recruitment of COPII to the ERGIC to bud LC3 lipidation-active vesicles as one potential membrane source of the autophagosome.
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Affiliation(s)
- Liang Ge
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
| | - Min Zhang
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
| | - Randy Schekman
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
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274
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Autophagy-related protein 7 deficiency in amyloid β (Aβ) precursor protein transgenic mice decreases Aβ in the multivesicular bodies and induces Aβ accumulation in the Golgi. THE AMERICAN JOURNAL OF PATHOLOGY 2014; 185:305-13. [PMID: 25433221 DOI: 10.1016/j.ajpath.2014.10.011] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 04/13/2014] [Revised: 10/06/2014] [Accepted: 10/14/2014] [Indexed: 12/20/2022]
Abstract
Alzheimer disease (AD) is biochemically characterized by increased levels of amyloid β (Aβ) peptide, which aggregates into extracellular Aβ plaques in AD brains. Before plaque formation, Aβ accumulates intracellularly in both AD brains and in the brains of AD model mice, which may contribute to disease progression. Autophagy, which is impaired in AD, clears cellular protein aggregates and participates in Aβ metabolism. In addition to a degradative role of autophagy in Aβ metabolism we recently showed that Aβ secretion is inhibited in mice lacking autophagy-related gene 7 (Atg7) in excitatory neurons in the mouse forebrain. This inhibition of Aβ secretion leads to intracellular accumulation of Aβ. Here, we used fluorescence and immunoelectron microscopy to elucidate the subcellular localization of the intracellular Aβ accumulation which accumulates in Aβ precursor protein mice lacking Atg7. Autophagy deficiency causes accumulation of p62(+) aggregates, but these aggregates do not contain Aβ. However, knockdown of Atg7 induced Aβ accumulation in the Golgi and a concomitant reduction of Aβ in the multivesicular bodies. This indicates that Atg7 influences the transport of Aβ possibly derived from Golgi to multivesicular bodies.
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275
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Laurent AC, Bisserier M, Lucas A, Tortosa F, Roumieux M, De Régibus A, Swiader A, Sainte-Marie Y, Heymes C, Vindis C, Lezoualc'h F. Exchange protein directly activated by cAMP 1 promotes autophagy during cardiomyocyte hypertrophy. Cardiovasc Res 2014; 105:55-64. [PMID: 25411381 DOI: 10.1093/cvr/cvu242] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
AIMS Stimulation of β-adrenergic receptors (β-AR) increases cAMP production and contributes to the pathogenesis of cardiac hypertrophy and failure through poorly understood mechanisms. We previously demonstrated that Exchange protein directly activated by cAMP 1 (Epac1)-induced hypertrophy in primary cardiomyocytes. Among the mechanisms triggered by cardiac stress, autophagy has been highlighted as a protective or harmful response. Here, we investigate whether Epac1 promotes cardiac autophagy and how altered autophagy has an impact on Epac1-induced cardiomyocyte hypertrophy. METHODS AND RESULTS We reported that direct stimulation of Epac1 with the agonist, Sp-8-(4-chlorophenylthio)-2'-O-methyl-cAMP (Sp-8-pCPT) promoted autophagy activation in neonatal cardiomyocytes. Stimulation of β-AR with isoprenaline (ISO) mimicked the effect of Epac1 on autophagy markers. Conversely, the induction of autophagy flux following ISO treatment was prevented in cardiomyocytes pre-treated with a selective inhibitor of Epac1, CE3F4. Importantly, we found that Epac1 deletion in mice protected against β-AR-induced cardiac remodelling and prevented the induction of autophagy. The signalling mechanisms underlying Epac1-induced autophagy involved a Ca(2+)/calmodulin-dependent kinase kinase β (CaMKKβ)/AMP-dependent protein kinase (AMPK) pathway. Finally, we provided evidence that pharmacological inhibition of autophagy using 3-methyladenine (3-MA) or down-regulation of autophagy-related protein 5 (Atg5) significantly potentiated Epac1-promoted cardiomyocyte hypertrophy. CONCLUSION Altogether, these findings demonstrate that autophagy is an adaptive response to antagonize Epac1-promoted cardiomyocyte hypertrophy.
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Affiliation(s)
- Anne-Coline Laurent
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
| | - Malik Bisserier
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
| | - Alexandre Lucas
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
| | - Florence Tortosa
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
| | - Marie Roumieux
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
| | - Annélie De Régibus
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
| | - Audrey Swiader
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
| | - Yannis Sainte-Marie
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
| | - Christophe Heymes
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
| | - Cécile Vindis
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
| | - Frank Lezoualc'h
- INSERM, UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Toulouse F-31432, France Université de Toulouse, UPS, Toulouse F-31432, France
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276
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Blanchard E, Roingeard P. Virus-induced double-membrane vesicles. Cell Microbiol 2014; 17:45-50. [PMID: 25287059 PMCID: PMC5640787 DOI: 10.1111/cmi.12372] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 09/25/2014] [Accepted: 09/29/2014] [Indexed: 12/27/2022]
Abstract
Many viruses that replicate in the cytoplasm compartmentalize their genome replication and transcription in specific subcellular microenvironments or organelle‐like structures, to increase replication efficiency and protect against host cell defences. Recent studies have investigated the complex membrane rearrangements induced by diverse positive‐strand RNA viruses, which are of two morphotypes : membrane invagination towards the lumen of the endoplasmic reticulum (ER) or other specifically targeted organelles and double‐membrane vesicles (DMVs) formed by extrusion of the ER membrane. DMVs resemble small autophagosomes and the viruses inducing these intriguing organelles are known to promote autophagy, suggesting a potential link between DMVs and the autophagic pathway. In this review, we summarize recent findings concerning the biogenesis, architecture and role of DMVs in the life cycle of viruses from different families and discuss their possible connection to autophagy or other related pathways.
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Affiliation(s)
- Emmanuelle Blanchard
- INSERM U966, Université François Rabelais and CHRU de Tours, Tours, Cedex 37032, France
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277
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Orhon I, Dupont N, Pampliega O, Cuervo AM, Codogno P. Autophagy and regulation of cilia function and assembly. Cell Death Differ 2014; 22:389-97. [PMID: 25361082 DOI: 10.1038/cdd.2014.171] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 09/05/2014] [Accepted: 09/10/2014] [Indexed: 12/21/2022] Open
Abstract
Motile and primary cilia (PC) are microtubule-based structures located at the cell surface of many cell types. Cilia govern cellular functions ranging from motility to integration of mechanical and chemical signaling from the environment. Recent studies highlight the interplay between cilia and autophagy, a conserved cellular process responsible for intracellular degradation. Signaling from the PC recruits the autophagic machinery to trigger autophagosome formation. Conversely, autophagy regulates ciliogenesis by controlling the levels of ciliary proteins. The cross talk between autophagy and ciliated structures is a novel aspect of cell biology with major implications in development, physiology and human pathologies related to defects in cilium function.
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Affiliation(s)
- I Orhon
- 1] INSERM U1151-CNRS UMR 8253, Paris, France [2] Institut Necker Enfants-Malades (INEM), Paris, France [3] Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - N Dupont
- 1] INSERM U1151-CNRS UMR 8253, Paris, France [2] Institut Necker Enfants-Malades (INEM), Paris, France [3] Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - O Pampliega
- 1] Department of Development and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, USA [2] Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, USA
| | - A M Cuervo
- 1] Department of Development and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY, USA [2] Institute for Aging Studies, Albert Einstein College of Medicine, Bronx, NY, USA
| | - P Codogno
- 1] INSERM U1151-CNRS UMR 8253, Paris, France [2] Institut Necker Enfants-Malades (INEM), Paris, France [3] Université Paris Descartes, Sorbonne Paris Cité, Paris, France
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278
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Chiu HW, Tseng YC, Hsu YH, Lin YF, Foo NP, Guo HR, Wang YJ. Arsenic trioxide induces programmed cell death through stimulation of ER stress and inhibition of the ubiquitin-proteasome system in human sarcoma cells. Cancer Lett 2014; 356:762-72. [PMID: 25449439 DOI: 10.1016/j.canlet.2014.10.025] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 10/23/2014] [Indexed: 01/21/2023]
Abstract
Sarcoma is a rare form of cancer that differs from the much more common carcinomas because it occurs in a distinct type of tissue. Many patients of sarcoma have poor response to chemotherapy and an increased risk for local recurrence. Arsenic trioxide (ATO) is used to treat certain types of leukemia. Recently, data have revealed that ATO induces sarcoma cell death in several types of solid tumor cell lines. In the present study, we investigated whether ATO induces cancer cell death and elucidated the underlying anti-cancer mechanisms. Our results showed that ATO caused concentration- and time-dependent cell death in human osteosarcoma and fibrosarcoma cells. The types of cell death that were induced by ATO were primarily autophagy and apoptosis. Furthermore, ATO activated p38, JNK and AMPK and inhibited the Akt/mTOR signaling pathways. Specifically, we found that ATO induced endoplasmic reticulum (ER) stress and suppressed proteasome activation in two types of sarcoma cell lines. However, the level of proteasome inhibition in osteosarcoma cells was lower than in fibrosarcoma cells. Thus, we used combined treatment with ATO and a proteasome inhibitor to examine the antitumor activity in fibrosarcoma cells. The data indicated showed that the combination treatment of ATO and MG132 (a proteasome inhibitor) resulted in synergistic cytotoxicity. In a fibrosarcoma xenograft mouse model, the combined treatment significantly reduced tumor progression. Immunohistochemical studies revealed that combined treatment induced autophagy and apoptosis. In summary, our results suggest a potential clinical application of ATO in sarcoma therapy and that combined treatment with a proteasome inhibitor can increase the therapeutic efficacy.
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Affiliation(s)
- Hui-Wen Chiu
- Department of Environmental and Occupational Health, National Cheng Kung University, Tainan, Taiwan; Division of Nephrology, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, Taiwan; Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan
| | - Yin-Chiu Tseng
- Department of Environmental and Occupational Health, National Cheng Kung University, Tainan, Taiwan
| | - Yung-Ho Hsu
- Division of Nephrology, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, Taiwan
| | - Yuh-Feng Lin
- Division of Nephrology, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, Taiwan; Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan
| | - Ning-Ping Foo
- Department of Environmental and Occupational Health, National Cheng Kung University, Tainan, Taiwan; Department of Emergency Medicine, Chi-Mei Medical Center, Liouying, Tainan, Taiwan; Department of Emergency Medicine, China Medical University-An Nan Hospital, Tainan, Taiwan
| | - How-Ran Guo
- Department of Environmental and Occupational Health, National Cheng Kung University, Tainan, Taiwan; Department of Occupational and Environmental Medicine, National Cheng Kung University Hospital, Tainan, Taiwan.
| | - Ying-Jan Wang
- Department of Environmental and Occupational Health, National Cheng Kung University, Tainan, Taiwan; Department of Biomedical Informatics, Asia University, Taichung, Taiwan; Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan.
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279
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Mechanism and Regulation of Autophagy and Its Role in Neuronal Diseases. Mol Neurobiol 2014; 52:1190-1209. [DOI: 10.1007/s12035-014-8921-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Accepted: 09/29/2014] [Indexed: 12/31/2022]
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280
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Autosis and autophagic cell death: the dark side of autophagy. Cell Death Differ 2014; 22:367-76. [PMID: 25257169 PMCID: PMC4326571 DOI: 10.1038/cdd.2014.143] [Citation(s) in RCA: 537] [Impact Index Per Article: 53.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 08/03/2014] [Accepted: 08/04/2014] [Indexed: 12/31/2022] Open
Abstract
It is controversial whether cells truly die via autophagy or whether — in dying cells — autophagy is merely an innocent bystander or a well-intentioned ‘Good Samaritan' trying to prevent inevitable cellular demise. However, there is increasing evidence that the genetic machinery of autophagy may be essential for cell death in certain settings. We recently identified a novel form of autophagy gene-dependent cell death, termed autosis, which is mediated by the Na+,K+-ATPase pump and has unique morphological features. High levels of cellular autophagy, as occurs with treatment with autophagy-inducing peptides, starvation, or in vivo during certain types of ischemia, can trigger autosis. These findings provide insights into the mechanisms and strategies for prevention of cell death during extreme stress conditions.
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281
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Reorganization of the endosomal system in Salmonella-infected cells: the ultrastructure of Salmonella-induced tubular compartments. PLoS Pathog 2014; 10:e1004374. [PMID: 25254663 PMCID: PMC4177991 DOI: 10.1371/journal.ppat.1004374] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 08/03/2014] [Indexed: 12/03/2022] Open
Abstract
During the intracellular life of Salmonella enterica, a unique membrane-bound compartment termed Salmonella-containing vacuole, or SCV, is formed. By means of translocated effector proteins, intracellular Salmonella also induce the formation of extensive, highly dynamic membrane tubules termed Salmonella-induced filaments or SIF. Here we report the first detailed ultrastructural analyses of the SCV and SIF by electron microscopy (EM), EM tomography and live cell correlative light and electron microscopy (CLEM). We found that a subset of SIF is composed of double membranes that enclose portions of host cell cytosol and cytoskeletal filaments within its inner lumen. Despite some morphological similarities, we found that the formation of SIF double membranes is independent from autophagy and requires the function of the effector proteins SseF and SseG. The lumen of SIF network is accessible to various types of endocytosed material and our CLEM analysis of double membrane SIF demonstrated that fluid phase markers accumulate only between the inner and outer membrane of these structures, a space continual with endosomal lumen. Our work reveals how manipulation of the endosomal membrane system by an intracellular pathogen results in a unique tubular membrane compartmentalization of the host cell, generating a shielded niche permissive for intracellular proliferation of Salmonella. Salmonella enterica is an invasive, facultative intracellular bacterial pathogen. Within mammalian host cells, Salmonella inhabits a specialized membrane-bound compartment, the Salmonella-containing vacuole (SCV), redirects host cell vesicular transport and massively remodels the endosomal system. These activities depend on the function of a type III secretion system and its translocated effector proteins. Intracellular Salmonella induces several types of tubular compartments termed Salmonella-induced tubules (SIT), but the biogenesis and biological function of SIT is only partially understood. Our work combines live cell imaging with correlative light and electron microscopy to provide ultrastructural insight into SIT. We report that SIT emerge as single membrane tubules that convert into double membrane tubules entrapping cytosol and cytoskeletal filaments. Labeling of the endosomal compartment and cytochemistry demonstrate that the space between inner and outer SIT membrane is composed of internalized material and connected to Salmonella within the SCV. The effector proteins SseF and SseG translocated by intracellular Salmonella are essential for the conversion of single to double membrane SIT. These findings challenge current models for the intracellular lifestyle of Salmonella and the composition of its intracellular habitat.
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282
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Chen Y, Zhou F, Zou S, Yu S, Li S, Li D, Song J, Li H, He Z, Hu B, Björn LO, Lipatova Z, Liang Y, Xie Z, Segev N. A Vps21 endocytic module regulates autophagy. Mol Biol Cell 2014; 25:3166-77. [PMID: 25143401 PMCID: PMC4196867 DOI: 10.1091/mbc.e14-04-0917] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Vps21 plays a role in autophagy in addition to its role in endocytosis. Individual deletions of members of the endocytic Vps21 module, including a GEF and four effectors, result in autophagy defects and accumulation of autophagosomal clusters. Therefore the endocytic Vps21 module regulates autophagy. In autophagy, the double-membrane autophagosome delivers cellular components for their degradation in the lysosome. The conserved Ypt/Rab GTPases regulate all cellular trafficking pathways, including autophagy. These GTPases function in modules that include guanine-nucleotide exchange factor (GEF) activators and downstream effectors. Rab7 and its yeast homologue, Ypt7, in the context of such a module, regulate the fusion of both late endosomes and autophagosomes with the lysosome. In yeast, the Rab5-related Vps21 is known for its role in early- to late-endosome transport. Here we show an additional role for Vps21 in autophagy. First, vps21∆ mutant cells are defective in selective and nonselective autophagy. Second, fluorescence and electron microscopy analyses show that vps21∆ mutant cells accumulate clusters of autophagosomal structures outside the vacuole. Third, cells with mutations in other members of the endocytic Vps21 module, including the GEF Vps9 and factors that function downstream of Vps21, Vac1, CORVET, Pep12, and Vps45, are also defective in autophagy and accumulate clusters of autophagosomes. Finally, Vps21 localizes to PAS. We propose that the endocytic Vps21 module also regulates autophagy. These findings support the idea that the two pathways leading to the lysosome—endocytosis and autophagy—converge through the Vps21 and Ypt7 GTPase modules.
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Affiliation(s)
- Yong Chen
- College of Life Sciences, Key Laboratory of Agricultural Environmental Microbiology of Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Fan Zhou
- College of Life Sciences, Key Laboratory of Agricultural Environmental Microbiology of Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China School of Biomedical Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
| | - Shenshen Zou
- College of Life Sciences, Key Laboratory of Agricultural Environmental Microbiology of Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Sidney Yu
- School of Biomedical Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
| | - Shaoshan Li
- Key Laboratory of Ecology and Environmental Science in Guangdong Higher Education, School of Life Science, South China Normal University, Guangzhou 510631, China
| | - Dan Li
- School of Life Sciences and Technology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Jingzhen Song
- School of Life Sciences and Technology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Hui Li
- School of Life Sciences and Technology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Zhiyi He
- Electron Microscope Demonstrating Co. Lab of Nanjing Agriculture University and Tianmei High-Tech Corporation, Nanjing 210095, China
| | - Bing Hu
- Electron Microscope Demonstrating Co. Lab of Nanjing Agriculture University and Tianmei High-Tech Corporation, Nanjing 210095, China
| | - Lars Olof Björn
- Key Laboratory of Ecology and Environmental Science in Guangdong Higher Education, School of Life Science, South China Normal University, Guangzhou 510631, China
| | - Zhanna Lipatova
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607
| | - Yongheng Liang
- College of Life Sciences, Key Laboratory of Agricultural Environmental Microbiology of Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
| | - Zhiping Xie
- School of Life Sciences and Technology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Nava Segev
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, IL 60607
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283
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Abstract
The autophagy-related 1 (Atg1) complex of Saccharomyces cerevisiae has a central role in the initiation of autophagy following starvation and TORC1 inactivation. The complex consists of the protein kinase Atg1, the TORC1 substrate Atg13, and the trimeric Atg17-Atg31-Atg29 scaffolding subcomplex. Autophagy is triggered when Atg1 and Atg13 assemble with the trimeric scaffold. Here we show by hydrogen-deuterium exchange coupled to mass spectrometry that the mutually interacting Atg1 early autophagy targeting/tethering domain and the Atg13 central domain are highly dynamic in isolation but together form a stable complex with ∼ 100-nM affinity. The Atg1-Atg13 complex in turn binds as a unit to the Atg17-Atg31-Atg29 scaffold with ∼ 10-μM affinity via Atg13. The resulting complex consists primarily of a dimer of pentamers in solution. These results lead to a model for autophagy initiation in which Atg1 and Atg13 are tightly associated with one another and assemble transiently into the pentameric Atg1 complex during starvation.
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284
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Abstract
Autophagy is the main cellular catabolic process responsible for degrading organelles and large protein aggregates. It is initiated by the formation of a unique membrane structure, the phagophore, which engulfs part of the cytoplasm and forms a double-membrane vesicle termed the autophagosome. Fusion of the outer autophagosomal membrane with the lysosome and degradation of the inner membrane contents complete the process. The extent of autophagy must be tightly regulated to avoid destruction of proteins and organelles essential for cell survival. Autophagic activity is thus regulated by external and internal cues, which initiate the formation of well-defined autophagy-related protein complexes that mediate autophagosome formation and selective cargo recruitment into these organelles. Autophagosome formation and the signaling pathways that regulate it have recently attracted substantial attention. In this review, we analyze the different signaling pathways that regulate autophagy and discuss recent progress in our understanding of autophagosome biogenesis.
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Affiliation(s)
- Adi Abada
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Zvulun Elazar
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
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285
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Politi Y, Gal L, Kalifa Y, Ravid L, Elazar Z, Arama E. Paternal mitochondrial destruction after fertilization is mediated by a common endocytic and autophagic pathway in Drosophila. Dev Cell 2014; 29:305-20. [PMID: 24823375 DOI: 10.1016/j.devcel.2014.04.005] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 01/16/2014] [Accepted: 04/02/2014] [Indexed: 12/12/2022]
Abstract
Almost all animals contain mitochondria of maternal origin only, but the exact mechanisms underlying this phenomenon are still vague. We investigated the fate of Drosophila paternal mitochondria after fertilization. We demonstrate that the sperm mitochondrial derivative (MD) is rapidly eliminated in a stereotypical process dubbed paternal mitochondrial destruction (PMD). PMD is initiated by a network of vesicles resembling multivesicular bodies and displaying common features of the endocytic and autophagic pathways. These vesicles associate with the sperm tail and mediate the disintegration of its plasma membrane. Subsequently, the MD separates from the axoneme and breaks into smaller fragments, which are then sequestered by autophagosomes for degradation in lysosomes. We further provide evidence for the involvement of the ubiquitin pathway and the autophagy receptor p62 in this process. Finally, we show that the ubiquitin ligase Parkin is not involved in PMD, implying a divergence from the autophagic pathway of damaged mitochondria.
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Affiliation(s)
- Yoav Politi
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Liron Gal
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yossi Kalifa
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Liat Ravid
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Zvulun Elazar
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Eli Arama
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
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286
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Zhang H, Duan C, Yang H. Defective autophagy in Parkinson's disease: lessons from genetics. Mol Neurobiol 2014; 51:89-104. [PMID: 24990317 DOI: 10.1007/s12035-014-8787-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2014] [Accepted: 06/09/2014] [Indexed: 01/09/2023]
Abstract
Parkinson's disease (PD) is the most prevalent neurodegenerative movement disorder. Genetic studies over the past two decades have greatly advanced our understanding of the etiological basis of PD and elucidated pathways leading to neuronal degeneration. Recent studies have suggested that abnormal autophagy, a well conserved homeostatic process for protein and organelle turnover, may contribute to neurodegeneration in PD. Moreover, many of the proteins related to both autosomal dominant and autosomal recessive PD, such as α-synuclein, PINK1, Parkin, LRRK2, DJ-1, GBA, and ATPA13A2, are also involved in the regulation of autophagy. We propose that reduced autophagy enhances the accumulation of α-synuclein, other pathogenic proteins, and dysfunctional mitochondria in PD, leading to oxidative stress and neuronal death.
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Affiliation(s)
- H Zhang
- Center of Parkinson's Disease Beijing Institute for Brain Disorders, Key Laboratory for Neurodegenerative Disease of the Ministry of Education, Department of Neurobiology Capital Medical University, Beijing, 100069, China
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287
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Karanasios E, Stapleton E, Manifava M, Ktistakis NT. Imaging Autophagy. ACTA ACUST UNITED AC 2014; 69:12.34.1-12.34.16. [DOI: 10.1002/0471142956.cy1234s69] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
| | - Eloise Stapleton
- MRC Group, Cardiff School of Biosciences, Cardiff University Cardiff United Kingdom
| | - Maria Manifava
- Signalling Programme, The Babraham Institute Cambridge United Kingdom
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288
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Le Bars R, Marion J, Le Borgne R, Satiat-Jeunemaitre B, Bianchi MW. ATG5 defines a phagophore domain connected to the endoplasmic reticulum during autophagosome formation in plants. Nat Commun 2014; 5:4121. [PMID: 24947672 DOI: 10.1038/ncomms5121] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 05/14/2014] [Indexed: 02/03/2023] Open
Abstract
Autophagosomes are the organelles responsible for macroautophagy and arise, in yeast and animals, from the sealing of a cup-shaped double-membrane precursor, the phagophore. How the phagophore is generated and grows into a sealed autophagosome is still not clear in detail, and unknown in plants. This is due, in part, to the scarcity of structurally informative, real-time imaging data of the required protein machinery at the phagophore formation site. Here we find that in intact living Arabidopsis tissue, autophagy-related protein ATG5, which is essential for autophagosome formation, is present at the phagophore site from early, sub-resolution stages and later defines a torus-shaped structure on a flat cisternal early phagophore. Movement and expansion of this structure are accompanied by the underlying endoplasmic reticulum, suggesting tight connections between the two compartments. Detailed real-time and 3D imaging of the growing phagophore are leveraged to propose a model for autophagosome formation in plants.
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Affiliation(s)
- Romain Le Bars
- Laboratoire Dynamique de la Compartimentation Cellulaire, CNRS UPR2355, Institut des Sciences du Végétal, Centre de Recherche de Gif (FRC3115), Saclay Plant Sciences, 91198 Gif-sur-Yvette, France
| | - Jessica Marion
- Laboratoire Dynamique de la Compartimentation Cellulaire, CNRS UPR2355, Institut des Sciences du Végétal, Centre de Recherche de Gif (FRC3115), Saclay Plant Sciences, 91198 Gif-sur-Yvette, France
| | - Rémi Le Borgne
- 1] Laboratoire Dynamique de la Compartimentation Cellulaire, CNRS UPR2355, Institut des Sciences du Végétal, Centre de Recherche de Gif (FRC3115), Saclay Plant Sciences, 91198 Gif-sur-Yvette, France [2] Pôle de Biologie Cellulaire, Imagif, Centre de Recherche de Gif, (FRC3115), Saclay Plant Sciences, CNRS, 91198 Gif-sur-Yvette, France
| | - Béatrice Satiat-Jeunemaitre
- 1] Laboratoire Dynamique de la Compartimentation Cellulaire, CNRS UPR2355, Institut des Sciences du Végétal, Centre de Recherche de Gif (FRC3115), Saclay Plant Sciences, 91198 Gif-sur-Yvette, France [2] Pôle de Biologie Cellulaire, Imagif, Centre de Recherche de Gif, (FRC3115), Saclay Plant Sciences, CNRS, 91198 Gif-sur-Yvette, France
| | - Michele Wolfe Bianchi
- 1] Laboratoire Dynamique de la Compartimentation Cellulaire, CNRS UPR2355, Institut des Sciences du Végétal, Centre de Recherche de Gif (FRC3115), Saclay Plant Sciences, 91198 Gif-sur-Yvette, France [2] UFR Sciences et Technologie, Université Paris-Est Créteil Val de Marne (UPEC), 61 av. Général de Gaulle, 94010 Créteil, France
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289
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Choi J, Park S, Biering SB, Selleck E, Liu CY, Zhang X, Fujita N, Saitoh T, Akira S, Yoshimori T, Sibley LD, Hwang S, Virgin HW. The parasitophorous vacuole membrane of Toxoplasma gondii is targeted for disruption by ubiquitin-like conjugation systems of autophagy. Immunity 2014; 40:924-35. [PMID: 24931121 DOI: 10.1016/j.immuni.2014.05.006] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 04/14/2014] [Indexed: 01/04/2023]
Abstract
Autophagy is a lysosomal degradation pathway that is important in cellular homeostasis. Prior work showed a key role for the autophagy related 5 (Atg5) in resistance to Toxoplasma gondii. Here we show that the cassette of autophagy proteins involved in the conjugation of microtubule-associated protein 1 light chain 3 (LC3) to phosphatidylethanolamine, including Atg7, Atg3, and the Atg12-Atg5-Atg16L1 complex play crucial roles in the control of T. gondii in vitro and in vivo. In contrast, pharmacologic modulation of the degradative autophagy pathway or genetic deletion of other essential autophagy genes had no substantial effects. Rather the conjugation system was required for targeting of LC3 and interferon-γ effectors onto the vacuolar membrane of T. gondii and its consequent disruption. These data suggest that the ubiquitin-like conjugation systems that reorganize intracellular membranes during canonical autophagy are necessary for proper targeting of immune effectors to the intracellular vacuole membranes utilized by pathogens.
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Affiliation(s)
- Jayoung Choi
- Department of Pathology, University of Chicago, Chicago, IL 60637, USA
| | - Sunmin Park
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Scott B Biering
- Department of Microbiology, University of Chicago, Chicago, IL 60637, USA
| | - Elizabeth Selleck
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Catherine Y Liu
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Xin Zhang
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Naonobu Fujita
- Department of Genetics, Graduate School of Medicine, WPI Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
| | - Tatsuya Saitoh
- Laboratory of Host Defense, WPI Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
| | - Shizuo Akira
- Laboratory of Host Defense, WPI Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
| | - Tamotsu Yoshimori
- Department of Genetics, Graduate School of Medicine, WPI Immunology Frontier Research Center, Osaka University, Osaka 565-0871, Japan
| | - L David Sibley
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Seungmin Hwang
- Department of Pathology, University of Chicago, Chicago, IL 60637, USA.
| | - Herbert W Virgin
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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290
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Merlini L, Nishino I. 201st ENMC International Workshop: Autophagy in muscular dystrophies – Translational approach, 1–3 November 2013, Bussum, The Netherlands. Neuromuscul Disord 2014; 24:546-61. [DOI: 10.1016/j.nmd.2014.03.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 03/03/2014] [Accepted: 03/13/2014] [Indexed: 12/12/2022]
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291
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Therapeutic targeting of autophagy in cancer. Part I: molecular pathways controlling autophagy. Semin Cancer Biol 2014; 31:89-98. [PMID: 24879905 DOI: 10.1016/j.semcancer.2014.05.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 05/09/2014] [Accepted: 05/18/2014] [Indexed: 12/31/2022]
Abstract
Autophagy is a process in which cells can generate energy and building materials, by degradation of redundant and/or damaged organelles and proteins. Especially during conditions of stress, autophagy helps to maintain homeostasis. In addition, autophagy has been shown to influence malignant transformation and cancer progression. The precise molecular events in autophagy are complex and the core autophagic machinery described to date consists of nearly thirty proteins. Apart from these factors that execute the process of autophagy, several signalling pathways are involved in converting internal and external stimuli into an autophagic response. In this review we provide an overview of the signalling pathways that influence autophagy, particularly in cancer cells. We will illustrate that interference with multiple of these signalling pathways can have significant effects on cancer cell survival.
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292
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Öhman T, Teirilä L, Lahesmaa-Korpinen AM, Cypryk W, Veckman V, Saijo S, Wolff H, Hautaniemi S, Nyman TA, Matikainen S. Dectin-1 pathway activates robust autophagy-dependent unconventional protein secretion in human macrophages. THE JOURNAL OF IMMUNOLOGY 2014; 192:5952-62. [PMID: 24808366 DOI: 10.4049/jimmunol.1303213] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Dectin-1 is a membrane-bound pattern recognition receptor for β-glucans, which are the main constituents of fungal cell walls. Detection of β-glucans by dectin-1 triggers an effective innate immune response. In this study, we have used a systems biology approach to provide the first comprehensive characterization of the secretome and associated intracellular signaling pathways involved in activation of dectin-1/Syk in human macrophages. Transcriptome and secretome analysis revealed that the dectin-1 pathway induced significant gene expression changes and robust protein secretion in macrophages. The enhanced protein secretion correlated only partly with increased gene expression. Bioinformatics combined with functional studies revealed that the dectin-1/Syk pathway activates both conventional and unconventional, vesicle-mediated, protein secretion. The unconventional protein secretion triggered by the dectin-1 pathway is dependent on inflammasome activity and an active autophagic process. In conclusion, our results reveal that unconventional protein secretion has an important role in the innate immune response against fungal infections.
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Affiliation(s)
- Tiina Öhman
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Laura Teirilä
- Finnish Institute of Occupational Health, 00250 Helsinki, Finland
| | - Anna-Maria Lahesmaa-Korpinen
- Computational Systems Biology Laboratory, Institute of Biomedicine, Genome-Scale Biology Research Program, Faculty of Medicine, University of Helsinki, 00014 Helsinki, Finland
| | - Wojciech Cypryk
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
| | - Ville Veckman
- Finnish Institute of Occupational Health, 00250 Helsinki, Finland
| | - Shinobu Saijo
- Department of Molecular Immunology, Medical Mycology Research Center, Chiba University, Chiba 260-8673, Japan; and Presto, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - Henrik Wolff
- Finnish Institute of Occupational Health, 00250 Helsinki, Finland
| | - Sampsa Hautaniemi
- Computational Systems Biology Laboratory, Institute of Biomedicine, Genome-Scale Biology Research Program, Faculty of Medicine, University of Helsinki, 00014 Helsinki, Finland
| | - Tuula A Nyman
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
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293
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Degradation of organelles or specific organelle components via selective autophagy in plant cells. Int J Mol Sci 2014; 15:7624-38. [PMID: 24802874 PMCID: PMC4057695 DOI: 10.3390/ijms15057624] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Revised: 03/31/2014] [Accepted: 04/16/2014] [Indexed: 12/13/2022] Open
Abstract
Macroautophagy (hereafter referred to as autophagy) is a cellular mechanism dedicated to the degradation and recycling of unnecessary cytosolic components by their removal to the lytic compartment of the cell (the vacuole in plants). Autophagy is generally induced by stresses causing energy deprivation and its operation occurs by special vesicles, termed autophagosomes. Autophagy also operates in a selective manner, recycling specific components, such as organelles, protein aggregates or even specific proteins, and selective autophagy is implicated in both cellular housekeeping and response to stresses. In plants, selective autophagy has recently been shown to degrade mitochondria, plastids and peroxisomes, or organelle components such as the endoplasmic-reticulum (ER) membrane and chloroplast-derived proteins such as Rubisco. This ability places selective-autophagy as a major factor in cellular steady-state maintenance, both under stress and favorable environmental conditions. Here we review the recent advances documented in plants for this cellular process and further discuss its impact on plant physiology.
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Wolf E, Gebhardt A, Kawauchi D, Walz S, von Eyss B, Wagner N, Renninger C, Krohne G, Asan E, Roussel MF, Eilers M. Miz1 is required to maintain autophagic flux. Nat Commun 2014; 4:2535. [PMID: 24088869 DOI: 10.1038/ncomms3535] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 09/03/2013] [Indexed: 02/07/2023] Open
Abstract
Miz1 is a zinc finger protein that regulates the expression of cell cycle inhibitors as part of a complex with Myc. Cell cycle-independent functions of Miz1 are poorly understood. Here we use a Nestin-Cre transgene to delete an essential domain of Miz1 in the central nervous system (Miz1(ΔPOZNes)). Miz1(ΔPOZNes) mice display cerebellar neurodegeneration characterized by the progressive loss of Purkinje cells. Chromatin immunoprecipitation sequencing and biochemical analyses show that Miz1 activates transcription upon binding to a non-palindromic sequence present in core promoters. Target genes of Miz1 encode regulators of autophagy and proteins involved in vesicular transport that are required for autophagy. Miz1(ΔPOZ) neuronal progenitors and fibroblasts show reduced autophagic flux. Consistently, polyubiquitinated proteins and p62/Sqtm1 accumulate in the cerebella of Miz1(ΔPOZNes) mice, characteristic features of defective autophagy. Our data suggest that Miz1 may link cell growth and ribosome biogenesis to the transcriptional regulation of vesicular transport and autophagy.
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Affiliation(s)
- Elmar Wolf
- 1] Theodor Boveri Institute, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany [2]
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Abstract
Autophagy is a lysosome-mediated degradative system that is a highly conserved pathway present in all eukaryotes. In all cells, double-membrane autophagosomes form and engulf cytoplasmic components, delivering them to the lysosome for degradation. Autophagy is essential for cell health and can be activated to function as a recycling pathway in the absence of nutrients or as a quality-control pathway to eliminate damaged organelles or even to eliminate invading pathogens. Autophagy was first identified as a pathway in mammalian cells using morphological techniques, but the Atg (autophagy-related) genes required for autophagy were identified in yeast genetic screens. Despite tremendous advances in elucidating the function of individual Atg proteins, our knowledge of how autophagosomes form and subsequently interact with the endosomal pathway has lagged behind. Recent progress toward understanding where and how both the endocytotic and autophagic pathways overlap is reviewed here.
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Affiliation(s)
- Sharon A Tooze
- London Research Institute, Cancer Research UK, Secretory Pathways Laboratory, London WC2A 3LY, United Kingdom
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296
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Self-eating to grow and kill: autophagy in filamentous ascomycetes. Appl Microbiol Biotechnol 2014; 97:9277-90. [PMID: 24077722 DOI: 10.1007/s00253-013-5221-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 10/26/2022]
Abstract
Autophagy is a tightly controlled degradation process in which eukaryotic cells digest their own cytoplasm containing protein complexes and organelles in the vacuole or lysosome. Two types of autophagy have been described: macroautophagy and microautophagy. Both types can be further divided into nonselective and selective processes. Molecular analysis of autophagy over the last two decades has mostly used the unicellular ascomycetes Saccharomyces cerevisiae and Pichia pastoris. Genetic analysis in these yeasts has identified 36 autophagy-related (atg) genes; many are conserved in all eukaryotes, including filamentous ascomycetes. However, the autophagic machinery also evolved significant differences in fungi, as a consequence of adaptation to diverse fungal lifestyles. Intensive studies on autophagy in the last few years have shown that autophagy in filamentous fungi is not only involved in nutrient homeostasis but in other cellular processes such as cell differentiation, pathogenicity and secondary metabolite production. This mini-review focuses on the specific roles of autophagy in filamentous fungi.
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297
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Hurley JH, Schulman BA. Atomistic autophagy: the structures of cellular self-digestion. Cell 2014; 157:300-311. [PMID: 24725401 PMCID: PMC4038036 DOI: 10.1016/j.cell.2014.01.070] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 01/28/2014] [Accepted: 01/28/2014] [Indexed: 01/06/2023]
Abstract
Autophagy is directed by numerous distinct autophagy-related (Atg) proteins. These transmit starvation-induced signals to lipids and regulatory proteins and assemble a double-membrane autophagosome sequestering bulk cytoplasm and/or selected cargos destined for degradation upon autophagosome fusion with a vacuole or lysosome. This Review discusses the structural mechanisms by which Atg proteins sense membrane curvature, mediate a PI(3)P-signaling cascade, and utilize autophagy-specific ubiquitin-like protein cascades to tether proteins to autophagosomal membranes. Recent elucidation of molecular interactions enabling vesicle nucleation, elongation, and cargo recruitment provides insights into how dynamic protein-protein and protein-membrane interactions may dictate size, shape, and contents of autophagosomes.
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Affiliation(s)
- James H Hurley
- Department of Molecular and Cell Biology, California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA.
| | - Brenda A Schulman
- Department of Structural Biology and Howard Hughes Medical Institute, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
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298
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Abstract
Alzheimer's disease (AD) is a neurodegenerative disease exhibiting amyloid beta (Aβ) peptide accumulation as a key characteristic. Autophagy, which is dysregulated in AD, participates in the metabolism of Aβ. Unexpectedly, we recently found that autophagy, in addition to its degradative function, also mediates the secretion of Aβ. This finding adds Aβ to an increasing number of biomolecules, the secretion of which is mediated by autophagy. We also showed that inhibition of Aβ secretion through genetic deletion of autophagy leads to intracellular Aβ accumulation, which enhanced neurodegeneration induced by autophagy deficiency. Hence, autophagy may play a central role in two pathological hallmarks of AD: Aβ amyloidosis and neurodegeneration. Herein, we summarize the role of autophagy in AD with focus on Aβ metabolism in light of the recently established role of autophagy in protein secretion. We discuss potential routes for autophagy-mediated Aβ secretion and suggest experimental approaches to further elucidate its mechanisms.
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Affiliation(s)
- Per Nilsson
- Laboratory for Proteolytic Neuroscience, RIKEN Brain Science Institute, Wako, Saitama, Japan; KI-Alzheimer's Disease Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Novum, Huddinge, Sweden
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299
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Cook KL, Soto-Pantoja DR, Abu-Asab M, Clarke PA, Roberts DD, Clarke R. Mitochondria directly donate their membrane to form autophagosomes during a novel mechanism of parkin-associated mitophagy. Cell Biosci 2014; 4:16. [PMID: 24669863 PMCID: PMC3977894 DOI: 10.1186/2045-3701-4-16] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 02/06/2014] [Indexed: 12/14/2022] Open
Abstract
Background Autophagy (macroautophagy), a cellular process of “self-eating”, segregates damaged/aged organelles into vesicles, fuses with lysosomes, and enables recycling of the digested materials. The precise origin(s) of the autophagosome membrane is unclear and remains a critical but unanswered question. Endoplasmic reticulum, mitochondria, Golgi complex, and the plasma membrane have been proposed as the source of autophagosomal membranes. Findings Using electron microscopy, immunogold labeling techniques, confocal microscopy, and flow cytometry we show that mitochondria can directly donate their membrane material to form autophagosomes. We expand upon earlier studies to show that mitochondria donate their membranes to form autophagosomes during basal and drug-induced autophagy. Moreover, electron microscopy and immunogold labeling studies show the first physical evidence of mitochondria forming continuous structures with LC3-labeled autophagosomes. The mitochondria forming these structures also stain positive for parkin, indicating that these mitochondrial-formed autophagosomes represent a novel mechanism of parkin-associated mitophagy. Conclusions With the on-going debate regarding autophagosomal membrane origin, this report demonstrates that mitochondria can donate membrane materials to form autophagosomes. These structures may also represent a novel form of mitophagy where the mitochondria contribute to the formation of autophagosomes. This novel form of parkin-associated mitophagy may be a more efficient bio-energetic process compared with de novo biosynthesis of a new membrane, particularly if the membrane is obtained, at least partly, from the organelle being targeted for later degradation in the mature autolysosome.
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Affiliation(s)
| | | | | | | | | | - Robert Clarke
- Department of Oncology and Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, USA.
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Ge L, Baskaran S, Schekman R, Hurley JH. The protein-vesicle network of autophagy. Curr Opin Cell Biol 2014; 29:18-24. [PMID: 24681112 DOI: 10.1016/j.ceb.2014.02.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 02/28/2014] [Indexed: 10/25/2022]
Abstract
The biogenesis of autophagosomes entails the nucleation and growth of a double-membrane sheet, the phagophore, which engulfs cytosol for delivery to the lysosome. Genetic studies have identified a class of Atg proteins that are essential for the process, yet the molecular mechanism of autophagosome biogenesis has been elusive. Proteomic, structural, super-resolution imaging, and biochemical reconstitution experiments have begun to fill in some of the gaps. This review describes progress and prospects for obtaining a four-dimensional network model of the nucleation and growth of the phagophore.
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Affiliation(s)
- Liang Ge
- Department of Molecular and Cell Biology and Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, United States
| | - Sulochanadevi Baskaran
- Department of Molecular and Cell Biology and California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, United States
| | - Randy Schekman
- Department of Molecular and Cell Biology and Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, United States
| | - James H Hurley
- Department of Molecular and Cell Biology and California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, United States.
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