51
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Mizushima N. A brief history of autophagy from cell biology to physiology and disease. Nat Cell Biol 2018; 20:521-527. [PMID: 29686264 DOI: 10.1038/s41556-018-0092-5] [Citation(s) in RCA: 459] [Impact Index Per Article: 76.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 03/20/2018] [Indexed: 02/06/2023]
Abstract
The field of autophagy research has developed rapidly since the first description of the process in the 1960s and the identification of autophagy genes in the 1990s. Autophagy is now increasingly studied at the level of organismal pathophysiology and is being connected to the medical sciences. This Historical Perspective describes a brief history of autophagy and discusses unanswered cell biological questions in the field.
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Affiliation(s)
- Noboru Mizushima
- Department of Biochemistry and Molecular Biology, Graduate School and Faculty of Medicine, The University of Tokyo, Tokyo, Japan.
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52
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Rahman MA, Mostofa MG, Ushimaru T. The Nem1/Spo7-Pah1/lipin axis is required for autophagy induction after TORC1 inactivation. FEBS J 2018; 285:1840-1860. [PMID: 29604183 DOI: 10.1111/febs.14448] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 02/01/2018] [Accepted: 03/26/2018] [Indexed: 02/06/2023]
Abstract
Autophagy is a process that requires intense membrane remodeling and consumption. The nutrient-responsive TORC1 (target of rapamycin complex 1) kinase regulates autophagy. However, how TORC1 controls autophagy via lipid/membrane biogenesis is unknown. TORC1 regulates the function of yeast phosphatidate phosphatase lipin Pah1 via the Nem1/Spo7 phosphatase complex. Here, we show that the Nem1/Spo7-Pah1 axis is required for autophagy induction after TORC1 inactivation and survival during starvation. Furthermore, this axis was critical for nucleophagy (both micronucleophagy and macronucleophagy) and was required for proper localization of micronucleophagy factor Nvj1 and macronucleophagy receptor Atg39. This study indicated that the Nem1/Spo7-Pah1 axis controlled by TORC1 is a critical branch for autophagy induction in nutrient starvation conditions.
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Affiliation(s)
| | - Md Golam Mostofa
- Graduate School of Science and Technology, Shizuoka University, Japan
| | - Takashi Ushimaru
- Graduate School of Science and Technology, Shizuoka University, Japan.,Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, Japan
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53
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Accelerated invagination of vacuoles as a stress response in chronically heat-stressed yeasts. Sci Rep 2018; 8:2644. [PMID: 29422608 PMCID: PMC5805771 DOI: 10.1038/s41598-018-20781-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 01/24/2018] [Indexed: 01/01/2023] Open
Abstract
When exposed to sublethal high temperatures, budding yeast cells can survive for a period of time; however, a sufficient amount of ubiquitin is necessary for this survival. To understand the nature of the stress, we examined the morphological changes in yeast cells, focusing on the vacuoles. Changes in vacuolar morphology were notable, and ruffled vacuolar membranes, accelerated invaginations of vacuolar membranes, and vesicle-like formations were observed. These changes occurred in the absence of Atg1, Atg9 or Ivy1 but appeared to require endosomal sorting proteins, such as Vps23, Vps24 or Pep12. Furthermore, the serial sections of the vacuoles analysed using an electron microscopic analysis revealed that spherical invaginated structures were linked together in a vacuole. Because degradation of cell surface proteins is induced from heat stress, fusion of endosomal and vacuolar membranes might occur frequently in heat-stressed cells, and yeast cells might be able to cope with a rapid increase in vacuolar surface area by such invaginations.
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54
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Pecenková T, Markovic V, Sabol P, Kulich I, Žárský V. Exocyst and autophagy-related membrane trafficking in plants. JOURNAL OF EXPERIMENTAL BOTANY 2017; 69:47-57. [PMID: 29069430 DOI: 10.1093/jxb/erx363] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Endomembrane traffic in eukaryotic cells functions partially as a means of communication; delivery of membrane in one direction has to be balanced with a reduction at the other end. This effect is typically the case during the defence against pathogens. To combat pathogens, cellular growth and differentiation are suppressed, while endomembrane traffic is poised towards limiting the pathogen attack. The octameric exocyst vesicle-tethering complex was originally discovered as a factor facilitating vesicle-targeting and vesicle-plasma membrane (PM) fusion during exocytosis prior to and possibly during SNARE complex formation. Interestingly, it was recently implicated both in animals and plants in autophagy membrane traffic. In animal cells, the exocyst is integrated into the mTOR-regulated energy metabolism stress/starvation pathway, participating in the formation and especially initiation of an autophagosome. In plants, the first functional link was to autophagy-related anthocyanin import to the vacuole and to starvation. In this concise review, we summarize the current knowledge of exocyst functions in autophagy and defence in plants that might involve unconventional secretion and compare it with animal conditions. Formation of different exocyst complexes during undisturbed cell growth, as opposed to periods of cellular stress reactions involving autophagy, might contribute to the coordination of endomembrane trafficking pathways.
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Affiliation(s)
- Tamara Pecenková
- Laboratory of Cell Biology, Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Czech Republic
- Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Charles University in Prague, Faculty of Science, Czech Republic
| | - Vedrana Markovic
- Laboratory of Cell Biology, Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Czech Republic
- Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Charles University in Prague, Faculty of Science, Czech Republic
| | - Peter Sabol
- Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Charles University in Prague, Faculty of Science, Czech Republic
| | - Ivan Kulich
- Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Charles University in Prague, Faculty of Science, Czech Republic
| | - Viktor Žárský
- Laboratory of Cell Biology, Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Czech Republic
- Laboratory of Cell Morphogenesis, Department of Experimental Plant Biology, Charles University in Prague, Faculty of Science, Czech Republic
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55
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Di Sansebastiano GP, Barozzi F, Piro G, Denecke J, de Marcos Lousa C. Trafficking routes to the plant vacuole: connecting alternative and classical pathways. JOURNAL OF EXPERIMENTAL BOTANY 2017; 69:79-90. [PMID: 29096031 DOI: 10.1093/jxb/erx376] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/27/2017] [Indexed: 05/02/2023]
Abstract
Due to the numerous roles plant vacuoles play in cell homeostasis, detoxification, and protein storage, the trafficking pathways to this organelle have been extensively studied. Recent evidence, however, suggests that our vision of transport to the vacuole is not as simple as previously imagined. Alternative routes have been identified and are being characterized. Intricate interconnections between routes seem to occur in various cases, complicating the interpretation of data. In this review, we aim to summarize the published evidence and link the emerging data with previous findings. We discuss the current state of information on alternative and classical trafficking routes to the plant vacuole.
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Affiliation(s)
- Gian Pietro Di Sansebastiano
- DiSTeBA (Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali), University of Salento, Campus ECOTEKNE, Italy
| | - Fabrizio Barozzi
- DiSTeBA (Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali), University of Salento, Campus ECOTEKNE, Italy
| | - Gabriella Piro
- DiSTeBA (Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali), University of Salento, Campus ECOTEKNE, Italy
| | | | - Carine de Marcos Lousa
- Centre for Plant Sciences, Leeds University, UK
- Leeds Beckett University, School of Applied and Clinical Sciences, UK
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56
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Amanullah A, Upadhyay A, Joshi V, Mishra R, Jana NR, Mishra A. Progressing neurobiological strategies against proteostasis failure: Challenges in neurodegeneration. Prog Neurobiol 2017; 159:1-38. [DOI: 10.1016/j.pneurobio.2017.08.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2017] [Revised: 06/01/2017] [Accepted: 08/25/2017] [Indexed: 02/07/2023]
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57
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Gopaldass N, Fauvet B, Lashuel H, Roux A, Mayer A. Membrane scission driven by the PROPPIN Atg18. EMBO J 2017; 36:3274-3291. [PMID: 29030482 DOI: 10.15252/embj.201796859] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 09/07/2017] [Accepted: 09/08/2017] [Indexed: 12/14/2022] Open
Abstract
Sorting, transport, and autophagic degradation of proteins in endosomes and lysosomes, as well as the division of these organelles, depend on scission of membrane-bound tubulo-vesicular carriers. How scission occurs is poorly understood, but family proteins bind these membranes. Here, we show that the yeast PROPPIN Atg18 carries membrane scission activity. Purified Atg18 drives tubulation and scission of giant unilamellar vesicles. Upon membrane contact, Atg18 folds its unstructured CD loop into an amphipathic α-helix that inserts into the bilayer. This allows the protein to engage its two lipid binding sites for PI3P and PI(3,5)P2 PI(3,5)P2 induces Atg18 oligomerization, which should concentrate lipid-inserted α-helices in the outer membrane leaflet and drive membrane tubulation and scission. The scission activity of Atg18 is compatible with its known roles in endo-lysosomal protein trafficking, autophagosome biogenesis, and vacuole fission. Key features required for membrane tubulation and scission by Atg18 are shared by other PROPPINs, suggesting that membrane scission may be a generic function of this protein family.
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Affiliation(s)
- Navin Gopaldass
- Department of Biochemistry, University of Lausanne, Epalinges, Switzerland
| | - Bruno Fauvet
- Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Hilal Lashuel
- Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Aurélien Roux
- Department of Biochemistry, University of Geneva, Geneva, Switzerland.,Swiss National Centre for Competence in Research Program Chemical Biology, Geneva, Switzerland
| | - Andreas Mayer
- Department of Biochemistry, University of Lausanne, Epalinges, Switzerland
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58
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Wölk C, Janich C, Bakowsky U, Langner A, Brezesinski G. Malonic acid based cationic lipids - The way to highly efficient DNA-carriers. Adv Colloid Interface Sci 2017; 248:20-34. [PMID: 28842122 DOI: 10.1016/j.cis.2017.08.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 08/10/2017] [Accepted: 08/10/2017] [Indexed: 01/21/2023]
Abstract
Cationic lipids play an important role as non-viral nucleic acid carriers in gene therapy since 3 decades. This review will introduce malonic acid derived cationic lipids as nucleic acid carriers which appeared in the literature dealing with lipofection 10years ago. The family of amino-functionalized branched fatty acid amides will be presented as well as different generations of malonic acid diamides. Both groups of cationic lipids yield lipid mixtures with highly efficient nucleic acid transfer activities in in-vitro cell culture models. The DNA transfer screening of lipid libraries with directed structural variations in the lipophilic as well as in the hydrophilic part of the amphiphiles yields structure/activity relationships. Furthermore, the detailed characterizations of selected lipid composites at the air/water interface and in bulk systems are summarized with regard to transfection determining physical-chemical properties. The findings are also discussed in comparison to results obtained with other families of cationic lipids.
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Affiliation(s)
- Christian Wölk
- Martin Luther University Halle-Wittenberg, Institute of Pharmacy, Wolfgang-Langenbeck-Strasse 4, 06120 Halle, Saale, Germany.
| | - Christopher Janich
- Martin Luther University Halle-Wittenberg, Institute of Pharmacy, Wolfgang-Langenbeck-Strasse 4, 06120 Halle, Saale, Germany
| | - Udo Bakowsky
- Department of Pharmaceutics and Biopharmaceutics, University Marburg, Robert-Koch-Straße 4, 35037 Marburg, Germany
| | - Andreas Langner
- Martin Luther University Halle-Wittenberg, Institute of Pharmacy, Wolfgang-Langenbeck-Strasse 4, 06120 Halle, Saale, Germany
| | - Gerald Brezesinski
- Max Planck Institute of Colloids and Interfaces, Science Park Potsdam-Golm, Am Mühlenberg 1, 14476 Potsdam, Germany.
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59
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Oku M, Maeda Y, Kagohashi Y, Kondo T, Yamada M, Fujimoto T, Sakai Y. Evidence for ESCRT- and clathrin-dependent microautophagy. J Cell Biol 2017; 216:3263-3274. [PMID: 28838958 PMCID: PMC5626533 DOI: 10.1083/jcb.201611029] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 04/27/2017] [Accepted: 07/24/2017] [Indexed: 12/20/2022] Open
Abstract
Microautophagy is a mode of autophagy in which the lysosomal or vacuolar membrane invaginates and engulfs target components. Oku et al. show that, upon a diauxic shift, yeast microautophagy involves recruitment of ESCRT proteins to the vacuolar membrane, including clathrin-interacting Vps27, and uptake of lipid droplets by the vacuole. Microautophagy refers to a mode of autophagy in which the lysosomal or vacuolar membrane invaginates and directly engulfs target components. The molecular machinery of membrane dynamics driving microautophagy is still elusive. Using immunochemical monitoring of yeast vacuolar transmembrane proteins, Vph1 and Pho8, fused to fluorescent proteins, we obtained evidence showing an induction of microautophagy after a diauxic shift in the yeast Saccharomyces cerevisiae. Components of the endosomal sorting complex required for transport machinery were found to be required for this process, and the gateway protein of the machinery, Vps27, was observed to change its localization onto the vacuolar membrane after a diauxic shift. We revealed the functional importance of Vps27’s interaction with clathrin in this microautophagy that also contributed to uptake of lipid droplets into the vacuole. This study sheds light on the molecular mechanism of microautophagy, which does not require the core Atg proteins.
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Affiliation(s)
- Masahide Oku
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Yuichiro Maeda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Yoko Kagohashi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Takeshi Kondo
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Mai Yamada
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Toyoshi Fujimoto
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yasuyoshi Sakai
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan .,Research Unit for Physiological Chemistry, Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto, Japan
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60
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Lefebvre C, Legouis R, Culetto E. ESCRT and autophagies: Endosomal functions and beyond. Semin Cell Dev Biol 2017; 74:21-28. [PMID: 28807884 DOI: 10.1016/j.semcdb.2017.08.014] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 07/27/2017] [Accepted: 08/04/2017] [Indexed: 12/20/2022]
Abstract
ESCRT (endosomal sorting complex required for transport) machinery has been initially identified for its role during endocytosis, which allows membrane proteins and lipids to be degraded in the lysosome. ESCRT function is required to form intraluminal vesicles permitting internalization of cytosolic components or membrane embedded cargoes and promoting endosome maturation. ESCRT machinery also contributes to multiple key cell mechanisms in which it reshapes membranes. In addition, ESCRT actively participates in different types of autophagy processes for degrading cytosolic components, such as endosomal microautophagy and macroautophagy. During macroautophagy, ESCRT promotes formation of multivesicular bodies, which can fuse with autophagosomes to generate amphisomes. This latter fusion probably brings to autophagosomes key membrane molecules necessary for the subsequent fusion with lysosomes. Interestingly, during macroautophagy, ESCRT proteins could be involved in non-canonical functions such as vesicle tethering or phagophore membrane sealing. Additionally, ESCRT subunits could directly interact with key autophagy related proteins to build a closer connection between endocytosis and autophagy pathways.
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Affiliation(s)
- Christophe Lefebvre
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette Cedex, France
| | - Renaud Legouis
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette Cedex, France.
| | - Emmanuel Culetto
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette Cedex, France.
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61
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Fernández-Fernández MR, Gragera M, Ochoa-Ibarrola L, Quintana-Gallardo L, Valpuesta JM. Hsp70 - a master regulator in protein degradation. FEBS Lett 2017; 591:2648-2660. [PMID: 28696498 DOI: 10.1002/1873-3468.12751] [Citation(s) in RCA: 145] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 07/04/2017] [Accepted: 07/07/2017] [Indexed: 12/31/2022]
Abstract
Proteostasis, the controlled balance of protein synthesis, folding, assembly, trafficking and degradation, is a paramount necessity for cell homeostasis. Impaired proteostasis is a hallmark of ageing and of many human diseases. Molecular chaperones are essential for proteostasis in eukaryotic cells, and their function has traditionally been linked to protein folding, assembly and disaggregation. More recent findings suggest that chaperones also contribute to key steps in protein degradation. In particular, Hsp70 has an essential role in substrate degradation through the ubiquitin-proteasome system, as well as through different autophagy pathways. Accumulated knowledge suggests that the fate of an Hsp70 substrate is dictated by the combination of partners (cochaperones and other chaperones) that interact with Hsp70 in a given cell context.
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Affiliation(s)
| | - Marcos Gragera
- Centro Nacional de Biotecnología (CNB-CSIC), Madrid, Spain
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62
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Botbol Y, Guerrero-Ros I, Macian F. Key roles of autophagy in regulating T-cell function. Eur J Immunol 2017; 46:1326-34. [PMID: 27151577 DOI: 10.1002/eji.201545955] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 04/11/2016] [Accepted: 05/02/2016] [Indexed: 01/06/2023]
Abstract
In the past 10 years, autophagy has emerged as a crucial regulator of T-cell homeostasis, activation, and differentiation. Through the ability to adjust the cell's proteome in response to different stimuli, different forms of autophagy have been shown to control T-cell homeostasis and survival. Autophagic processes can also determine the magnitude of the T-cell response to TCR engagement, by regulating the cellular levels of specific signaling intermediates and modulating the metabolic output in activated T cells. In this review we will examine the mechanisms that control autophagy activity in T cells, such as ROS signaling and signaling through common gamma-chain cytokine receptors, and the different aspect of T-cell biology, including T-cell survival, effector cell function, and generation of memory, which can be regulated by autophagy.
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Affiliation(s)
- Yair Botbol
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA
| | | | - Fernando Macian
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY, USA
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63
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Tsuji T, Fujimoto M, Tatematsu T, Cheng J, Orii M, Takatori S, Fujimoto T. Niemann-Pick type C proteins promote microautophagy by expanding raft-like membrane domains in the yeast vacuole. eLife 2017; 6:e25960. [PMID: 28590904 PMCID: PMC5462540 DOI: 10.7554/elife.25960] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Accepted: 05/16/2017] [Indexed: 11/13/2022] Open
Abstract
Niemann-Pick type C is a storage disease caused by dysfunction of NPC proteins, which transport cholesterol from the lumen of lysosomes to the limiting membrane of that compartment. Using freeze fracture electron microscopy, we show here that the yeast NPC orthologs, Ncr1p and Npc2p, are essential for formation and expansion of raft-like domains in the vacuolar (lysosome) membrane, both in stationary phase and in acute nitrogen starvation. Moreover, the expanded raft-like domains engulf lipid droplets by a microautophagic mechanism. We also found that the multivesicular body pathway plays a crucial role in microautophagy in acute nitrogen starvation by delivering sterol to the vacuole. These data show that NPC proteins promote microautophagy in stationary phase and under nitrogen starvation conditions, likely by increasing sterol in the limiting membrane of the vacuole.
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Affiliation(s)
- Takuma Tsuji
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Megumi Fujimoto
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Tsuyako Tatematsu
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Jinglei Cheng
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Minami Orii
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Sho Takatori
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Toyoshi Fujimoto
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
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64
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Wu DJ, Adamopoulos IE. Autophagy and autoimmunity. Clin Immunol 2017; 176:55-62. [PMID: 28095319 DOI: 10.1016/j.clim.2017.01.007] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 01/11/2017] [Accepted: 01/12/2017] [Indexed: 12/19/2022]
Abstract
Autophagy is a highly conserved protein degradation pathway from yeasts to humans that is essential for removing protein aggregates and misfolded proteins in healthy cells. Recently, autophagy-related genes polymorphisms have been implicated in several autoimmune diseases including systemic lupus erythematosus, rheumatoid arthritis, psoriasis, and multiple sclerosis. Numerous studies reveal autophagy and autophagy-related proteins also participate in immune regulation. Conditional deletions of autophagy-related proteins in mice have rendered protection from experimental autoimmune encephalomyelitis, and TNF-mediated joint destruction in animal models of multiple sclerosis and experimental arthritis respectively. As autophagy is strongly implicated in immune functions such as removal of intracellular bacteria, inflammatory cytokine secretion, antigen presentation, and lymphocyte development, in this review we summarized current understanding of the roles of autophagy and autophagy proteins in autoimmune diseases.
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Affiliation(s)
- Dennis J Wu
- Graduate Group in Immunology, University of California at Davis, USA; Division of Rheumatology, Allergy and Clinical Immunology, University of California at Davis, USA
| | - Iannis E Adamopoulos
- Graduate Group in Immunology, University of California at Davis, USA; Division of Rheumatology, Allergy and Clinical Immunology, University of California at Davis, USA; Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children Northern California, USA.
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65
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Kalachev AV, Yurchenko OV. Microautophagy in nutritive phagocytes of sea urchins. PROTOPLASMA 2017; 254:609-614. [PMID: 27020676 DOI: 10.1007/s00709-016-0963-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 03/15/2016] [Indexed: 06/05/2023]
Abstract
Two types of cells were observed in germinative epithelium of male and female sea urchins: germ cells and somatic accessory cells; the latter referred to as nutritive phagocytes. At the onset of gametogenesis, nutritive phagocytes accumulate nutrients and greatly increase in their size. As gametogenesis progresses, the accumulated nutrients are transferred from nutritive phagocytes into developing gametes, and size of the nutritive phagocytes decreases. An electron microscopic study of nutritive phagocytes in sea urchins, Strongylocentrotus intermedius, at different stages of annual reproductive cycle showed for the first time that both macro- and microautophagy take place in nutritive phagocytes. Both processes occur simultaneously and regulate size and composition of nutritive phagocytes in male and female sea urchins. Nutritive phagocytes consume redundant cytoplasm via macroautophagy. Microautophagy is probably involved in consumption of redundant membranes that appear within nutritive phagocytes due to destruction of nutrient-storing globules, macroautophagy, and phagocytosis of germ cells or their remnants.
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Affiliation(s)
- Alexander V Kalachev
- A.V. Zhirmunsky Institute of Marine Biology, Far Eastern Branch of the Russian Academy of Sciences, 17 Palchevskogo str., Vladivostok, 690041, Russia.
| | - Olga V Yurchenko
- A.V. Zhirmunsky Institute of Marine Biology, Far Eastern Branch of the Russian Academy of Sciences, 17 Palchevskogo str., Vladivostok, 690041, Russia
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66
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Yamaguchi H, Arakawa S, Kanaseki T, Miyatsuka T, Fujitani Y, Watada H, Tsujimoto Y, Shimizu S. Golgi membrane-associated degradation pathway in yeast and mammals. EMBO J 2016; 35:1991-2007. [PMID: 27511903 DOI: 10.15252/embj.201593191] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 07/14/2016] [Indexed: 01/08/2023] Open
Abstract
Autophagy is a cellular process that degrades subcellular constituents, and is conserved from yeast to mammals. Although autophagy is believed to be essential for living cells, cells lacking Atg5 or Atg7 are healthy, suggesting that a non-canonical degradation pathway exists to compensate for the lack of autophagy. In this study, we show that the budding yeast Saccharomyces cerevisiae, which lacks Atg5, undergoes bulk protein degradation using Golgi-mediated structures to compensate for autophagy when treated with amphotericin B1, a polyene antifungal drug. We named this mechanism Golgi membrane-associated degradation (GOMED) pathway. This process is driven by the disruption of PI(4)P-dependent anterograde trafficking from the Golgi, and it also exists in Atg5-deficient mammalian cells. Biologically, when an Atg5-deficient β-cell line and Atg7-deficient β-cells were cultured in glucose-deprived medium, a disruption in the secretion of insulin granules from the Golgi occurred, and GOMED was induced to digest these (pro)insulin granules. In conclusion, GOMED is activated by the disruption of PI(4)P-dependent anterograde trafficking in autophagy-deficient yeast and mammalian cells.
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Affiliation(s)
- Hirofumi Yamaguchi
- Department of Pathological Cell Biology, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo, Japan
| | - Satoko Arakawa
- Department of Pathological Cell Biology, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo, Japan
| | - Toku Kanaseki
- Department of Pathological Cell Biology, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo, Japan
| | - Takeshi Miyatsuka
- Department of Medicine, Metabolism & Endocrinology, Juntendo University, Bunkyo-ku, Tokyo, Japan
| | - Yoshio Fujitani
- Department of Medicine, Metabolism & Endocrinology, Juntendo University, Bunkyo-ku, Tokyo, Japan
| | - Hirotaka Watada
- Department of Medicine, Metabolism & Endocrinology, Juntendo University, Bunkyo-ku, Tokyo, Japan
| | - Yoshihide Tsujimoto
- Department of Molecular and Cellular Biology, Research Institute, Osaka Medical Center for Cancer and Cardiovascular Diseases, Higashinari, Osaka, Japan
| | - Shigeomi Shimizu
- Department of Pathological Cell Biology, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Bunkyo-ku, Tokyo, Japan
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Papinski D, Kraft C. Regulation of Autophagy By Signaling Through the Atg1/ULK1 Complex. J Mol Biol 2016; 428:1725-41. [PMID: 27059781 DOI: 10.1016/j.jmb.2016.03.030] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 03/25/2016] [Accepted: 03/28/2016] [Indexed: 02/06/2023]
Abstract
Autophagy is an intracellular degradation pathway highly conserved in eukaryotic species. It is characterized by selective or bulk trafficking of cytosolic structures-ranging from single proteins to cell organelles-to the vacuole or a lysosome, in which the autophagic cargo is degraded. Autophagy fulfils a large set of roles, including nutrient mobilization in starvation conditions, clearance of protein aggregates and host defence against intracellular pathogens. Not surprisingly, autophagy has been linked to several human diseases, among them neurodegenerative disorders and cancer. Autophagy is coordinated by the action of the Atg1/ULK1 kinase, which is the target of several important stress signaling cascades. In this review, we will discuss the available information on both upstream regulation and downstream effectors of Atg1/ULK1, with special focus on reported and proposed kinase substrates.
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Affiliation(s)
- Daniel Papinski
- Max F. Perutz Laboratories, Vienna Biocenter, University of Vienna, A-1030 Vienna, Austria
| | - Claudine Kraft
- Max F. Perutz Laboratories, Vienna Biocenter, University of Vienna, A-1030 Vienna, Austria.
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68
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Wen X, Klionsky DJ. An overview of macroautophagy in yeast. J Mol Biol 2016; 428:1681-99. [PMID: 26908221 DOI: 10.1016/j.jmb.2016.02.021] [Citation(s) in RCA: 169] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 02/15/2016] [Accepted: 02/16/2016] [Indexed: 12/19/2022]
Abstract
Macroautophagy is an evolutionarily conserved dynamic pathway that functions primarily in a degradative manner. A basal level of macroautophagy occurs constitutively, but this process can be further induced in response to various types of stress including starvation, hypoxia and hormonal stimuli. The general principle behind macroautophagy is that cytoplasmic contents can be sequestered within a transient double-membrane organelle, an autophagosome, which subsequently fuses with a lysosome or vacuole (in mammals, or yeast and plants, respectively), allowing for degradation of the cargo followed by recycling of the resulting macromolecules. Through this basic mechanism, macroautophagy has a critical role in cellular homeostasis; however, either insufficient or excessive macroautophagy can seriously compromise cell physiology, and thus, it needs to be properly regulated. In fact, a wide range of diseases are associated with dysregulation of macroautophagy. There has been substantial progress in understanding the regulation and molecular mechanisms of macroautophagy in different organisms; however, many questions concerning some of the most fundamental aspects of macroautophagy remain unresolved. In this review, we summarize current knowledge about macroautophagy mainly in yeast, including the mechanism of autophagosome biogenesis, the function of the core macroautophagic machinery, the regulation of macroautophagy and the process of cargo recognition in selective macroautophagy, with the goal of providing insights into some of the key unanswered questions in this field.
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Affiliation(s)
- Xin Wen
- Life Sciences Institute and Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Daniel J Klionsky
- Life Sciences Institute and Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
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69
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Xilouri M, Brekk OR, Stefanis L. Autophagy and Alpha-Synuclein: Relevance to Parkinson's Disease and Related Synucleopathies. Mov Disord 2016; 31:178-92. [PMID: 26813776 DOI: 10.1002/mds.26477] [Citation(s) in RCA: 192] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 10/21/2015] [Accepted: 10/25/2015] [Indexed: 12/14/2022] Open
Abstract
Evidence from human postmortem material, transgenic mice, and cellular/animal models of PD link alpha-synuclein accumulation to alterations in the autophagy lysosomal pathway. Conversely, alpha-synuclein mutations related to PD pathogenesis, as well as post-translational modifications of the wild-type protein, result in the generation of aberrant species that may impair further the function of the autophagy lysosomal pathway, thus generating a vicious cycle leading to neuronal death. Moreover, PD-linked mutations in lysosomal-related genes, such as glucocerebrosidase, have been also shown to contribute to alpha-synuclein accumulation and related toxicity, indicating that lysosomal dysfunction may, in part, account for the neurodegeneration observed in synucleinopathies. In the current review, we summarize findings related to the inter-relationship between alpha-synuclein and lysosomal proteolytic pathways, focusing especially on recent experimental strategies based on the manipulation of the autophagy lysosomal pathway to counteract alpha-synuclein-mediated neurotoxicity in vivo. Pinpointing the factors that regulate alpha-synuclein association to the lysosome may represent potential targets for therapeutic interventions in PD and related synucleinopathies.
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Affiliation(s)
- Maria Xilouri
- Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Oeystein Roed Brekk
- Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Leonidas Stefanis
- Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.,Second Department of Neurology, University of Athens Medical School, Athens, Greece
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70
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Cull B, Prado Godinho JL, Fernandes Rodrigues JC, Frank B, Schurigt U, Williams RA, Coombs GH, Mottram JC. Glycosome turnover in Leishmania major is mediated by autophagy. Autophagy 2015; 10:2143-57. [PMID: 25484087 PMCID: PMC4502677 DOI: 10.4161/auto.36438] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Autophagy is a central process behind the cellular remodeling that occurs during differentiation of Leishmania, yet the cargo of the protozoan parasite's autophagosome is unknown. We have identified glycosomes, peroxisome-like organelles that uniquely compartmentalize glycolytic and other metabolic enzymes in Leishmania and other kinetoplastid parasitic protozoa, as autophagosome cargo. It has been proposed that the number of glycosomes and their content change during the Leishmania life cycle as a key adaptation to the different environments encountered. Quantification of RFP-SQL-labeled glycosomes showed that promastigotes of L. major possess ~20 glycosomes per cell, whereas amastigotes contain ~10. Glycosome numbers were significantly greater in promastigotes and amastigotes of autophagy-defective L. major Δatg5 mutants, implicating autophagy in glycosome homeostasis and providing a partial explanation for the previously observed growth and virulence defects of these mutants. Use of GFP-ATG8 to label autophagosomes showed glycosomes to be cargo in ~15% of them; glycosome-containing autophagosomes were trafficked to the lysosome for degradation. The number of autophagosomes increased 10-fold during differentiation, yet the percentage of glycosome-containing autophagosomes remained constant. This indicates that increased turnover of glycosomes was due to an overall increase in autophagy, rather than an upregulation of autophagosomes containing this cargo. Mitophagy of the single mitochondrion was not observed in L. major during normal growth or differentiation; however, mitochondrial remnants resulting from stress-induced fragmentation colocalized with autophagosomes and lysosomes, indicating that autophagy is used to recycle these damaged organelles. These data show that autophagy in Leishmania has a central role not only in maintaining cellular homeostasis and recycling damaged organelles but crucially in the adaptation to environmental change through the turnover of glycosomes.
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Affiliation(s)
- Benjamin Cull
- a Wellcome Trust Center for Molecular Parasitology; Institute of Infection, Immunity and Inflammation; College of Medical, Veterinary and Life Sciences ; University of Glasgow ; Glasgow , UK
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71
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Chanoca A, Kovinich N, Burkel B, Stecha S, Bohorquez-Restrepo A, Ueda T, Eliceiri KW, Grotewold E, Otegui MS. Anthocyanin Vacuolar Inclusions Form by a Microautophagy Mechanism. THE PLANT CELL 2015; 27:2545-59. [PMID: 26342015 PMCID: PMC4815043 DOI: 10.1105/tpc.15.00589] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 08/11/2015] [Accepted: 08/11/2015] [Indexed: 05/18/2023]
Abstract
Anthocyanins are flavonoid pigments synthesized in the cytoplasm and stored inside vacuoles. Many plant species accumulate densely packed, 3- to 10-μm diameter anthocyanin deposits called anthocyanin vacuolar inclusions (AVIs). Despite their conspicuousness and importance in organ coloration, the origin and nature of AVIs have remained controversial for decades. We analyzed AVI formation in cotyledons of different Arabidopsis thaliana genotypes grown under anthocyanin inductive conditions and in purple petals of lisianthus (Eustoma grandiorum). We found that cytoplasmic anthocyanin aggregates in close contact with the vacuolar surface are directly engulfed by the vacuolar membrane in a process reminiscent of microautophagy. The engulfed anthocyanin aggregates are surrounded by a single membrane derived from the tonoplast and eventually become free in the vacuolar lumen like an autophagic body. Neither endosomal/prevacuolar trafficking nor the autophagy ATG5 protein is involved in the formation of AVIs. In Arabidopsis, formation of AVIs is promoted by both an increase in cyanidin 3-O-glucoside derivatives and by depletion of the glutathione S-transferase TT19. We hypothesize that this novel microautophagy mechanism also mediates the transport of other flavonoid aggregates into the vacuole.
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Affiliation(s)
- Alexandra Chanoca
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin 53706 Laboratory of Molecular and Cellular Biology, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Nik Kovinich
- Center for Applied Plant Sciences, Department of Molecular Genetics and Department of Horticulture and Crop Science, The Ohio State University, Columbus, Ohio 43210
| | - Brian Burkel
- Laboratory for Optical and Computational Instrumentation, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Samantha Stecha
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin 53706 Laboratory of Molecular and Cellular Biology, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Andres Bohorquez-Restrepo
- Center for Applied Plant Sciences, Department of Molecular Genetics and Department of Horticulture and Crop Science, The Ohio State University, Columbus, Ohio 43210
| | - Takashi Ueda
- Department of Biological Sciences, University of Tokyo, Hongo, Bunkyo-ku Tokyo 113-0033, Japan
| | - Kevin W Eliceiri
- Laboratory for Optical and Computational Instrumentation, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Erich Grotewold
- Center for Applied Plant Sciences, Department of Molecular Genetics and Department of Horticulture and Crop Science, The Ohio State University, Columbus, Ohio 43210
| | - Marisa S Otegui
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin 53706 Laboratory of Molecular and Cellular Biology, University of Wisconsin-Madison, Madison, Wisconsin 53706 Department of Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706
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72
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Chaperone-mediated autophagy and neurodegeneration: connections, mechanisms, and therapeutic implications. Neurosci Bull 2015. [PMID: 26206600 DOI: 10.1007/s12264-015-1542-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Lysosomes degrade dysfunctional intracellular components via three pathways: macroautophagy, microautophagy, and chaperone-mediated autophagy (CMA). Unlike the other two, CMA degrades cytosolic proteins with a recognized KFERQ-like motif in lysosomes and is important for cellular homeostasis. CMA activity declines with age and is altered in neurodegenerative diseases. Its impairment leads to the accumulation of aggregated proteins, some of which may be directly tied to the pathogenic processes of neurodegenerative diseases. Its induction may accelerate the clearance of pathogenic proteins and promote cell survival, representing a potential therapeutic approach for the treatment of neurodegenerative diseases. In this review, we summarize the current findings on how CMA is involved in neurodegenerative diseases, especially in Parkinson's disease.
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73
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Numrich J, Péli-Gulli MP, Arlt H, Sardu A, Griffith J, Levine T, Engelbrecht-Vandré S, Reggiori F, De Virgilio C, Ungermann C. The I-BAR protein Ivy1 is an effector of the Rab7 GTPase Ypt7 involved in vacuole membrane homeostasis. J Cell Sci 2015; 128:2278-92. [PMID: 25999476 DOI: 10.1242/jcs.164905] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 05/18/2015] [Indexed: 01/07/2023] Open
Abstract
Membrane fusion at the vacuole depends on a conserved machinery that includes SNAREs, the Rab7 homolog Ypt7 and its effector HOPS. Here, we demonstrate that Ypt7 has an unexpected additional function by controlling membrane homeostasis and nutrient-dependent signaling on the vacuole surface. We show that Ivy1, the yeast homolog of mammalian missing-in-metastasis (MIM), is a vacuolar effector of Ypt7-GTP and interacts with the EGO/ragulator complex, an activator of the target of rapamycin kinase complex 1 (TORC1) on vacuoles. Loss of Ivy1 does not affect EGO vacuolar localization and function. In combination with the deletion of individual subunits of the V-ATPase, however, we observed reduced TORC1 activity and massive enlargement of the vacuole surface. Consistent with this, Ivy1 localizes to invaginations at the vacuole surface and on liposomes in a phosphoinositide- and Ypt7-GTP-controlled manner, which suggests a role in microautophagy. Our data, thus, reveal that Ivy1 is a novel regulator of vacuole membrane homeostasis with connections to TORC1 signaling.
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Affiliation(s)
- Johannes Numrich
- University of Osnabrück, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Marie-Pierre Péli-Gulli
- University of Fribourg, Department of Biology, Division of Biochemistry, Chemin du Musée 10, Fribourg CH-1700, Switzerland
| | - Henning Arlt
- University of Osnabrück, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Alessandro Sardu
- University of Fribourg, Department of Biology, Division of Biochemistry, Chemin du Musée 10, Fribourg CH-1700, Switzerland
| | - Janice Griffith
- University Medical Centre Utrecht, Center for Molecular Medicine, Department of Cell Biology, Heidelberglaan 100, Utrecht 3584 CX, The Netherlands
| | - Tim Levine
- UCL Institute of Ophthalmology, Department of Cell Biology, 11-43 Bath St., London EC1V 9EL, UK
| | - Siegfried Engelbrecht-Vandré
- University of Osnabrück, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Fulvio Reggiori
- University Medical Centre Utrecht, Center for Molecular Medicine, Department of Cell Biology, Heidelberglaan 100, Utrecht 3584 CX, The Netherlands
| | - Claudio De Virgilio
- University of Fribourg, Department of Biology, Division of Biochemistry, Chemin du Musée 10, Fribourg CH-1700, Switzerland
| | - Christian Ungermann
- University of Osnabrück, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
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74
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Larson ER, Domozych DS, Tierney ML. SNARE VTI13 plays a unique role in endosomal trafficking pathways associated with the vacuole and is essential for cell wall organization and root hair growth in arabidopsis. ANNALS OF BOTANY 2014; 114:1147-59. [PMID: 24737717 PMCID: PMC4195547 DOI: 10.1093/aob/mcu041] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
BACKGROUND AND AIMS Root hairs are responsible for water and nutrient uptake from the soil and their growth is responsive to biotic and abiotic changes in their environment. Root hair expansion is a polarized process requiring secretory and endosomal pathways that deliver and recycle plasma membrane and cell wall material to the growing root hair tip. In this paper, the role of VTI13 (AT3G29100), a member of the VTI vesicular soluble NSF attachment receptor (SNARE) gene family in Arabidopsis thaliana, in root hair growth is described. METHODS Genetic analysis and complementation of the vti13 root hair phenotypes of Arabidopsis thaliana were first used to assess the role of VTI13 in root hair growth. Transgenic lines expressing a green fluorescent protein (GFP)-VTI13 construct were used to characterize the intracellular localization of VTI13 in root hairs using confocal microscopy and immunotransmission electron microscopy. KEY RESULTS VTI13 was characterized and genetic analysis used to show that its function is required for root hair growth. Expression of a GFP-VTI13 fusion in the vti13 mutant background was shown to complement the vti13 root hair phenotype. GFP-VTI13 localized to both the vacuole membrane and a mobile endosomal compartment. The function of VTI13 was also required for the localization of SYP41 to the trans-Golgi network. Immunohistochemical analysis indicated that cell wall organization is altered in vti13 root hairs and root epidermal cells. CONCLUSIONS These results show that VTI13 plays a unique role in endosomal trafficking pathways associated with the vacuole within root hairs and is essential for the maintenance of cell wall organization and root hair growth in arabidopsis.
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Affiliation(s)
- Emily R Larson
- Cellular, Molecular and Biomedical Science Program Institute of Molecular Cell and Systems Biology, University of Glasgow College of Medical, Veterinary & Life Sciences, Glasgow G12 8QQ, UK
| | - David S Domozych
- Department of Biology, Skidmore College, Saratoga Springs, NY, USA
| | - Mary L Tierney
- Cellular, Molecular and Biomedical Science Program Department of Plant Biology, University of Vermont, Burlington, VT, USA
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75
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Schuck S, Gallagher CM, Walter P. ER-phagy mediates selective degradation of endoplasmic reticulum independently of the core autophagy machinery. J Cell Sci 2014; 127:4078-88. [PMID: 25052096 PMCID: PMC4163648 DOI: 10.1242/jcs.154716] [Citation(s) in RCA: 184] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Selective autophagy of damaged or redundant organelles is an important mechanism for maintaining cell homeostasis. We found previously that endoplasmic reticulum (ER) stress in the yeast Saccharomyces cerevisiae causes massive ER expansion and triggers the formation of large ER whorls. Here, we show that stress-induced ER whorls are selectively taken up into the vacuole, the yeast lysosome, by a process termed ER-phagy. Import into the vacuole does not involve autophagosomes but occurs through invagination of the vacuolar membrane, indicating that ER-phagy is topologically equivalent to microautophagy. Even so, ER-phagy requires neither the core autophagy machinery nor several other proteins specifically implicated in microautophagy. Thus, autophagy of ER whorls represents a distinct type of organelle-selective autophagy. Finally, we provide evidence that ER-phagy degrades excess ER membrane, suggesting that it contributes to cell homeostasis by controlling organelle size.
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Affiliation(s)
- Sebastian Schuck
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, University of California San Francisco, 600 16th Street, San Francisco, CA 94158, USA
| | - Ciara M Gallagher
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, University of California San Francisco, 600 16th Street, San Francisco, CA 94158, USA
| | - Peter Walter
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, University of California San Francisco, 600 16th Street, San Francisco, CA 94158, USA
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76
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Autophagy-related direct membrane import from ER/cytoplasm into the vacuole or apoplast: a hidden gateway also for secondary metabolites and phytohormones? Int J Mol Sci 2014; 15:7462-74. [PMID: 24786101 PMCID: PMC4057683 DOI: 10.3390/ijms15057462] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 03/18/2014] [Accepted: 03/18/2014] [Indexed: 02/06/2023] Open
Abstract
Transportation of low molecular weight cargoes into the plant vacuole represents an essential plant cell function. Several lines of evidence indicate that autophagy-related direct endoplasmic reticulum (ER) to vacuole (and also, apoplast) transport plays here a more general role than expected. This route is regulated by autophagy proteins, including recently discovered involvement of the exocyst subcomplex. Traffic from ER into the vacuole bypassing Golgi apparatus (GA) acts not only in stress-related cytoplasm recycling or detoxification, but also in developmentally-regulated biopolymer and secondary metabolite import into the vacuole (or apoplast), exemplified by storage proteins and anthocyanins. We propose that this pathway is relevant also for some phytohormones’ (e.g., auxin, abscisic acid (ABA) and salicylic acid (SA)) degradation. We hypothesize that SA is not only an autophagy inducer, but also a cargo for autophagy-related ER to vacuole membrane container delivery and catabolism. ER membrane localized enzymes will potentially enhance the area of biosynthetic reactive surfaces, and also, abundant ER localized membrane importers (e.g., ABC transporters) will internalize specific molecular species into the autophagosome biogenesis domain of ER. Such active ER domains may create tubular invaginations of tonoplast into the vacuoles as import intermediates. Packaging of cargos into the ER-derived autophagosome-like containers might be an important mechanism of vacuole and exosome biogenesis and cytoplasm protection against toxic metabolites. A new perspective on metabolic transformations intimately linked to membrane trafficking in plants is emerging.
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77
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Arlt H, Reggiori F, Ungermann C. Retromer and the dynamin Vps1 cooperate in the retrieval of transmembrane proteins from vacuoles. J Cell Sci 2014; 128:645-55. [DOI: 10.1242/jcs.132720] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Endosomes are dynamic organelles that need to combine the ability to successfully deliver proteins and lipids to the lysosome-like vacuole, and recycle others to the Golgi or the plasma membrane. We now show that retromer, implicated in retrieval of proteins from endosomes to the Golgi or to the plasma membrane, can act on vacuoles. We explore its function using an assay that allows us to dissect the required cofactors during recycling. We demonstrate that recycling of the transmembrane receptor Vps10 from vacuoles requires the retromer, the dynamin-like Vps1, and the Rab7 GTPase Ypt7. While retromer and Vps1 leave the vacuole together with the cargo, Ypt7 stays behind, in agreement with its regulatory function. Recycled cargo then accumulates at endosomes and later at the Golgi, implying consecutive sorting steps to the final destination. Our data further suggest that retromer and Vps1 are essential to maintain vacuole membrane organization. All together, our data demonstrate that retromer can cooperate with Vps1 and the Rab Ypt7 to clear the vacuole of selected membrane proteins.
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78
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Abstract
Autophagy refers to a group of processes that involve degradation of cytoplasmic components including cytosol, macromolecular complexes, and organelles, within the vacuole or the lysosome of higher eukaryotes. The various types of autophagy have attracted increasing attention for at least two reasons. First, autophagy provides a compelling example of dynamic rearrangements of subcellular membranes involving issues of protein trafficking and organelle identity, and thus it is fascinating for researchers interested in questions pertinent to basic cell biology. Second, autophagy plays a central role in normal development and cell homeostasis, and, as a result, autophagic dysfunctions are associated with a range of illnesses including cancer, diabetes, myopathies, some types of neurodegeneration, and liver and heart diseases. That said, this review focuses on autophagy in yeast. Many aspects of autophagy are conserved from yeast to human; in particular, this applies to the gene products mediating these pathways as well as some of the signaling cascades regulating it, so that the information we relate is relevant to higher eukaryotes. Indeed, as with many cellular pathways, the initial molecular insights were made possible due to genetic studies in Saccharomyces cerevisiae and other fungi.
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79
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Busatti HGNO, Alves RJ, Santana-Anjos KG, Gil FF, Cury MC, Vannier-Santos MA, Gomes MA. Effects of metronidazole analogues on Giardia lamblia: experimental infection and cell organization. Diagn Microbiol Infect Dis 2013; 75:160-4. [PMID: 23331963 DOI: 10.1016/j.diagmicrobio.2012.11.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 10/29/2012] [Accepted: 11/03/2012] [Indexed: 11/18/2022]
Abstract
The chemotherapeutic agents used for the treatment of giardiasis are often associated with adverse side effects and are refractory cases, due to the development of resistant parasites. Therefore the search for new drugs is required. We have previously reported the giardicidal effects of metronidazole (MTZ) and its analogues (MTZ-Ms, MTZ-Br, MTZ-N(3), and MTZ-I) on the trophozoites of Giardia lamblia. Now we evaluated the activity of some giardicidal MTZ analogues in experimental infections in gerbils and its effects on the morphology and ultrastructural organization of Giardia. The giardicidal activity in experimental infections showed ED(50) values significantly lower for MTZ-I and MTZ-Br when compared to MTZ. Transmission electron microscopy was employed to approach the mechanism(s) of action of MTZ analogues upon the protozoan. MTZ analogues were more active than MTZ in changing significantly the morphology and ultrastructure of the parasite. The analogues affected parasite cell vesicle trafficking, autophagy, and triggered differentiation into cysts. These results coupled with the excellent giardicidal activity and lower toxicity demonstrate that these nitroimidazole derivates may be important therapeutic alternatives for combating giardiasis. In addition, our results suggest a therapeutic advantage in obtaining synthetic metronidazole analogues for screening of activities against other infectious agents.
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Affiliation(s)
- Haendel G N O Busatti
- Depto. Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte, MG, Brazil
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80
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Son YO, Pratheeshkumar P, Lei W, Wang X, Kim DH, Lee JY, Zhang Z, Lee JC, Shi X. Reactive oxygen species mediate Cr(VI)-induced carcinogenesis through PI3K/AKT-dependent activation of GSK-3β/β-catenin signaling. Toxicol Appl Pharmacol 2013; 271:239-48. [PMID: 23707771 PMCID: PMC3742697 DOI: 10.1016/j.taap.2013.04.036] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/19/2013] [Accepted: 04/20/2013] [Indexed: 01/07/2023]
Abstract
Cr(VI) compounds are known human carcinogens that primarily target the lungs. Cr(VI) produces reactive oxygen species (ROS), but the exact effects of ROS on the signaling molecules involved in Cr(VI)-induced carcinogenesis have not been extensively studied. Chronic exposure of human bronchial epithelial cells to Cr(VI) at nanomolar concentrations (10-100nM) for 3months not only induced cell transformation, but also increased the potential of these cells to invade and migrate. Injection of Cr(VI)-stimulated cells into nude mice resulted in the formation of tumors. Chronic exposure to Cr(VI) increased levels of intracellular ROS and antiapoptotic proteins. Transfection with catalase or superoxide dismutase (SOD) prevented Cr(VI)-mediated increases in colony formation, cell invasion, migration, and xenograft tumors. While chronic Cr(VI) exposure led to activation of signaling cascades involving PI3K/AKT/GSK-3β/β-catenin and PI3K/AKT/mTOR, transfection with catalase or SOD markedly inhibited Cr(VI)-mediated activation of these signaling proteins. Inhibitors specific for AKT or β-catenin almost completely suppressed the Cr(VI)-mediated increase in total and active β-catenin proteins and colony formation. In particular, Cr(VI) suppressed autophagy of epithelial cells under nutrition deprivation. Furthermore, there was a marked induction of AKT, GSK-3β, β-catenin, mTOR, and carcinogenic markers in tumor tissues formed in mice after injection with Cr(VI)-stimulated cells. Collectively, our findings suggest that ROS is a key mediator of Cr(VI)-induced carcinogenesis through the activation of PI3K/AKT-dependent GSK-3β/β-catenin signaling and the promotion of cell survival mechanisms via the inhibition of apoptosis and autophagy.
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Affiliation(s)
- Young-Ok Son
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA
| | - Poyil Pratheeshkumar
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA
| | - Wang Lei
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA
| | - Xin Wang
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA
| | - Dong-Hern Kim
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA
| | - Ju-Yeon Lee
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA
| | - Zhuo Zhang
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA
| | - Jeong-Chae Lee
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA
- School of Dentistry and Institute of Oral Biosciences, Research Center of Bioactive Materials, Chonbuk National University, Jeonju 561-756, South Korea
| | - Xianglin Shi
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA
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81
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Etxeberria E, Gonzalez P, Pozueta-Romero J. Architectural remodeling of the tonoplast during fluid-phase endocytosis. PLANT SIGNALING & BEHAVIOR 2013; 8:e24793. [PMID: 23656870 PMCID: PMC3908939 DOI: 10.4161/psb.24793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
During fluid phase endocytosis (FPE) in plant storage cells, the vacuole receives a considerable amount of membrane and fluid contents. If allowed to accumulate over a period of time, the enlarging tonoplast and increase in fluids would invariably disrupt the structural equilibrium of the mature cells. Therefore, a membrane retrieval process must exist that will guarantee membrane homeostasis in light of tonoplast expansion by membrane addition during FPE. We examined the morphological changes to the vacuolar structure during endocytosis in red beet hypocotyl tissue using scanning laser confocal microscopy and immunohistochemistry. The heavily pigmented storage vacuole allowed us to visualize all architectural transformations during treatment. When red beet tissue was incubated in 200 mM sucrose, a portion of the sucrose accumulated entered the cell by means of FPE. The accumulation process was accompanied by the development of vacuole-derived vesicles which transiently counterbalanced the addition of surplus endocytic membrane during rapid rates of endocytosis. Topographic fluorescent confocal micrographs showed an ensuing reduction in the size of the vacuole-derived vesicles and further suggest their reincorporation into the vacuole to maintain vacuolar unity and solute concentration.
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Affiliation(s)
- Ed Etxeberria
- Department of Horticultural Sciences; University of Florida; Institute of Food and Agricultural Sciences; Citrus Research and Education Center; Lake Alfred, FL USA
- Correspondence to: Ed Etxeberria,
| | - Pedro Gonzalez
- Department of Horticultural Sciences; University of Florida; Institute of Food and Agricultural Sciences; Citrus Research and Education Center; Lake Alfred, FL USA
| | - Javier Pozueta-Romero
- Instituto de Agrobiotecnologia; Universidad Publica de Navarra/Consejo de Investigaciones Cientificas/Gobierno de Navarra; Nafarroa, Spain
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82
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Sriskanthadevan S, Brar SK, Manoharan K, Siu CH. Ca(2+) -calmodulin interacts with DdCAD-1 and promotes DdCAD-1 transport by contractile vacuoles in Dictyostelium cells. FEBS J 2013; 280:1795-806. [PMID: 23441816 DOI: 10.1111/febs.12203] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 01/18/2013] [Accepted: 01/25/2013] [Indexed: 11/28/2022]
Abstract
UNLABELLED The Ca(2+) -dependent cell-cell adhesion molecule DdCAD-1, encoded by the cadA gene of Dictyostelium discoideum, is synthesized at the onset of development as a soluble protein and then transported to the plasma membrane by contractile vacuoles. Calmodulin associates with contractile vacuoles in a Ca(2+) -dependent manner, and co-localizes with DdCAD-1 on the surface of contractile vacuoles. Bioinformatics analysis revealed multiple calmodulin-binding motifs in DdCAD-1. Co-immunoprecipitation and pull-down studies showed that only Ca(2+) -bound calmodulin was able to bind DdCAD-1. Structural integrity of DdCAD-1, but not the native conformation, was required for its interaction with calmodulin. To investigate the role of calmodulin in the import of DdCAD-1 into contractile vacuoles, an in vitro import assay consisting of contractile vacuoles derived from cadA(-) cells and recombinant proteins was employed. Prior stripping of the bound calmodulin from contractile vacuoles by EGTA impaired import of DdCAD-1, which was restored by addition of exogenous calmodulin. The calmodulin antagonists W-7 and compound 48/80 blocked the binding of calmodulin onto stripped contractile vacuoles, and inhibited the import of DdCAD-1. Together, the data show that calmodulin forms a complex with DdCAD-1 and promotes the docking and import of DdCAD-1 into contractile vacuoles. STRUCTURED DIGITAL ABSTRACT CaM physically interacts with DdCAD-1 by pull down (View Interaction: 1, 2) DdCAD-1 binds to CaM by far western blotting (View interaction) DdCAD-1 physically interacts with CaM by anti bait coimmunoprecipitation (View interaction).
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83
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α-Synuclein and protein degradation systems: a reciprocal relationship. Mol Neurobiol 2012; 47:537-51. [PMID: 22941029 DOI: 10.1007/s12035-012-8341-2] [Citation(s) in RCA: 191] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 08/20/2012] [Indexed: 12/18/2022]
Abstract
An increasing wealth of data indicates a close relationship between the presynaptic protein alpha-synuclein and Parkinson's disease (PD) pathogenesis. Alpha-synuclein protein levels are considered as a major determinant of its neurotoxic potential, whereas secreted extracellular alpha-synuclein has emerged as an additional important factor in this regard. However, the manner of alpha-synuclein degradation in neurons remains contentious. Both the ubiquitin-proteasome system (UPS) and the autophagy-lysosome pathway (ALP)-mainly macroautophagy and chaperone-mediated autophagy-have been suggested to contribute to alpha-synuclein turnover. Additionally, other proteases such as calpains, neurosin, and metalloproteinases have been also proposed to have a role in intracellular and extracellular alpha-synuclein processing. Both UPS and ALP activity decline with aging and such decline may play a pivotal role in many neurodegenerative conditions. Alterations in these major proteolytic pathways may result in alpha-synuclein accumulation due to impaired clearance. Conversely, increased alpha-synuclein protein burden promotes the generation of aberrant species that may impair further UPS or ALP function, generating thus a bidirectional positive feedback loop leading to neuronal death. In the current review, we summarize the recent findings related to alpha-synuclein degradation, as well as to alpha-synuclein-mediated aberrant effects on protein degradation systems. Identifying the factors that regulate alpha-synuclein association to cellular proteolytic pathways may represent potential targets for therapeutic interventions in PD and related synucleinopathies.
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84
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Zieger M, Mayer A. Yeast vacuoles fragment in an asymmetrical two-phase process with distinct protein requirements. Mol Biol Cell 2012; 23:3438-49. [PMID: 22787281 PMCID: PMC3431934 DOI: 10.1091/mbc.e12-05-0347] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Yeast vacuoles fragment and fuse in response to environmental conditions, such as changes in osmotic conditions or nutrient availability. Here we analyze osmotically induced vacuole fragmentation by time-lapse microscopy. Small fragmentation products originate directly from the large central vacuole. This happens by asymmetrical scission rather than by consecutive equal divisions. Fragmentation occurs in two distinct phases. Initially, vacuoles shrink and generate deep invaginations that leave behind tubular structures in their vicinity. Already this invagination requires the dynamin-like GTPase Vps1p and the vacuolar proton gradient. Invaginations are stabilized by phosphatidylinositol 3-phosphate (PI(3)P) produced by the phosphoinositide 3-kinase complex II. Subsequently, vesicles pinch off from the tips of the tubular structures in a polarized manner, directly generating fragmentation products of the final size. This phase depends on the production of phosphatidylinositol-3,5-bisphosphate and the Fab1 complex. It is accelerated by the PI(3)P- and phosphatidylinositol 3,5-bisphosphate-binding protein Atg18p. Thus vacuoles fragment in two steps with distinct protein and lipid requirements.
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Affiliation(s)
- Martin Zieger
- Département de Biochimie, Université de Lausanne, 1066 Epalinges, Switzerland
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85
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Petroi D, Popova B, Taheri-Talesh N, Irniger S, Shahpasandzadeh H, Zweckstetter M, Outeiro TF, Braus GH. Aggregate clearance of α-synuclein in Saccharomyces cerevisiae depends more on autophagosome and vacuole function than on the proteasome. J Biol Chem 2012; 287:27567-79. [PMID: 22722939 DOI: 10.1074/jbc.m112.361865] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Parkinson disease is the second most common neurodegenerative disease. The molecular hallmark is the accumulation of proteinaceous inclusions termed Lewy bodies containing misfolded and aggregated α-synuclein. The molecular mechanism of clearance of α-synuclein aggregates was addressed using the bakers' yeast Saccharomyces cerevisiae as the model. Overexpression of wild type α-synuclein or the genetic variant A53T integrated into one genomic locus resulted in a gene copy-dependent manner in cytoplasmic proteinaceous inclusions reminiscent of the pathogenesis of the disease. In contrast, overexpression of the genetic variant A30P resulted only in transient aggregation, whereas the designer mutant A30P/A36P/A76P neither caused aggregation nor impaired yeast growth. The α-synuclein accumulation can be cleared after promoter shut-off by a combination of autophagy and vacuolar protein degradation. Whereas the proteasomal inhibitor MG-132 did not significantly inhibit aggregate clearance, treatment with phenylmethylsulfonyl fluoride, an inhibitor of vacuolar proteases, resulted in significant reduction in clearance. Consistently, a cim3-1 yeast mutant restricted in the 19 S proteasome regulatory subunit was unaffected in clearance, whereas an Δatg1 yeast mutant deficient in autophagy showed a delayed aggregate clearance response. A cim3-1Δatg1 double mutant was still able to clear aggregates, suggesting additional cellular mechanisms for α-synuclein clearance. Our data provide insight into the mechanisms yeast cells use for clearing different species of α-synuclein and demonstrate a higher contribution of the autophagy/vacuole than the proteasome system. This contributes to the understanding of how cells can cope with toxic and/or aggregated proteins and may ultimately enable the development of novel strategies for therapeutic intervention.
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Affiliation(s)
- Doris Petroi
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Georg-August-Universität Göttingen, Göttingen, Germany
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86
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The many faces of mitochondrial autophagy: making sense of contrasting observations in recent research. Int J Cell Biol 2012; 2012:431684. [PMID: 22550491 PMCID: PMC3328949 DOI: 10.1155/2012/431684] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 12/21/2011] [Indexed: 11/17/2022] Open
Abstract
Research into the selective autophagic degradation of mitochondria—mitophagy—has intensified in recent years, yielding significant insights into the function, mechanism, and regulation of this process in the eukaryotic cell. However, while some molecular players in budding yeast, such as Atg32p, Uth1p, and Aup1p, have been identified, studies further interrogating the mechanistic and regulatory features of mitophagy have yielded inconsistent and sometimes conflicting results. In this review, we focus on the current understanding of mitophagy mechanism, induction, and regulation in yeast, and suggest that differences in experimental conditions used in the various studies of mitophagy may contribute to the observed discrepancies. Consideration and understanding of these differences may help place the mechanism and regulation of mitophagy in context, and further indicate the intricate role that this essential process plays in the life and death of eukaryotic cells.
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87
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Li WW, Li J, Bao JK. Microautophagy: lesser-known self-eating. Cell Mol Life Sci 2012; 69:1125-36. [PMID: 22080117 PMCID: PMC11114512 DOI: 10.1007/s00018-011-0865-5] [Citation(s) in RCA: 499] [Impact Index Per Article: 41.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 09/29/2011] [Accepted: 10/14/2011] [Indexed: 12/14/2022]
Abstract
Microautophagy, the non-selective lysosomal degradative process, involves direct engulfment of cytoplasmic cargo at a boundary membrane by autophagic tubes, which mediate both invagination and vesicle scission into the lumen. With its constitutive characteristics, microautophagy of soluble substrates can be induced by nitrogen starvation or rapamycin via regulatory signaling complex pathways. The maintenance of organellar size, membrane homeostasis, and cell survival under nitrogen restriction are the main functions of microautophagy. In addition, microautophagy is coordinated with and complements macroautophagy, chaperone-mediated autophagy, and other self-eating pathways. Three forms of selective microautophagy, including micropexophagy, piecemeal microautophagy of the nucleus, and micromitophagy, share common ground with microautophagy to some degree. As the accumulation of experimental data, the precise mechanisms that govern microautophagy are becoming more appreciated. Here, we review the microautophagic molecular machinery, its physiological functions, and relevance to human diseases, especially in diseases involving multivesicular bodies and multivesicular lysosomes.
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Affiliation(s)
- Wen-wen Li
- School of Life Sciences, Sichuan University, Chengdu, China
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88
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Juenemann K, Reits EA. Alternative macroautophagic pathways. Int J Cell Biol 2012; 2012:189794. [PMID: 22536246 PMCID: PMC3320029 DOI: 10.1155/2012/189794] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Accepted: 01/19/2012] [Indexed: 12/16/2022] Open
Abstract
Macroautophagy is a bulk degradation process that mediates the clearance of long-lived proteins, aggregates, or even whole organelles. This process includes the formation of autophagosomes, double-membrane structures responsible for delivering cargo to lysosomes for degradation. Currently, other alternative autophagy pathways have been described, which are independent of macroautophagic key players like Atg5 and Beclin 1 or the lipidation of LC3. In this review, we highlight recent insights in indentifying and understanding the molecular mechanism responsible for alternative autophagic pathways.
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Affiliation(s)
- Katrin Juenemann
- Department of Cell Biology and Histology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | - Eric A. Reits
- Department of Cell Biology and Histology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
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89
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Son YO, Wang X, Hitron JA, Zhang Z, Cheng S, Budhraja A, Ding S, Lee JC, Shi X. Cadmium induces autophagy through ROS-dependent activation of the LKB1-AMPK signaling in skin epidermal cells. Toxicol Appl Pharmacol 2011; 255:287-96. [PMID: 21767558 DOI: 10.1016/j.taap.2011.06.024] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 06/29/2011] [Accepted: 06/30/2011] [Indexed: 12/17/2022]
Abstract
Cadmium is a toxic heavy metal which is environmentally and occupationally relevant. The mechanisms underlying cadmium-induced autophagy are not yet completely understood. The present study shows that cadmium induces autophagy, as demonstrated by the increase of LC3-II formation and the GFP-LC3 puncta cells. The induction of autophagosomes was directly visualized by electron microscopy in cadmium-exposed skin epidermal cells. Blockage of LKB1 or AMPK by siRNA transfection suppressed cadmium-induced autophagy. Cadmium-induced autophagy was inhibited in dominant-negative AMPK-transfected cells, whereas it was accelerated in cells transfected with the constitutively active form of AMPK. mTOR signaling, a negative regulator of autophagy, was downregulated in cadmium-exposed cells. In addition, cadmium generated reactive oxygen species (ROS) at relatively low levels, and caused poly(ADP-ribose) polymerase-1 (PARP) activation and ATP depletion. Inhibition of PARP by pharmacological inhibitors or its siRNA transfection suppressed ATP reduction and autophagy in cadmium-exposed cells. Furthermore, cadmium-induced autophagy signaling was attenuated by either exogenous addition of catalase and superoxide dismutase, or by overexpression of these enzymes. Consequently, these results suggest that cadmium-mediated ROS generation causes PARP activation and energy depletion, and eventually induces autophagy through the activation of LKB1-AMPK signaling and the down-regulation of mTOR in skin epidermal cells.
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Affiliation(s)
- Young-Ok Son
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, KY 40536-0305, USA
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90
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Siu CH, Sriskanthadevan S, Wang J, Hou L, Chen G, Xu X, Thomson A, Yang C. Regulation of spatiotemporal expression of cell-cell adhesion molecules during development of Dictyostelium discoideum. Dev Growth Differ 2011; 53:518-27. [DOI: 10.1111/j.1440-169x.2011.01267.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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91
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Abstract
Macroautophagy and chaperone-mediated autophagy (CMA) are the two main mammalian lysosomal proteolytic systems. In macroautophagy, double-membrane structures engulf organelles and other intracellular constituents through a highly regulated process that involves the formation of autophagic vacuoles and their fusion with lysosomes. In CMA, selected proteins are targeted through a nonvesicular pathway to a transport complex at the lysosomal membrane, through which they are threaded into the lysosomes and degraded. Autophagy is important in development, differentiation, cellular remodelling and survival during nutrient starvation. Increasing evidence suggests that autophagic dysregulation causes accumulation of abnormal proteins or damaged organelles, which is a characteristic of chronic neurodegenerative conditions, such as Parkinson disease (PD). Evidence from post-mortem material, transgenic mice, and animal and cellular models of PD suggests that both major autophagic pathways are malfunctioning. Numerous connections exist between proteins genetically linked to autosomal dominant PD, in particular α-synuclein and LRRK2, and autophagic pathways. However, proteins involved in recessive PD, such as PINK1 and Parkin (PINK2), function in the process of mitophagy, whereby damaged mitochondria are selectively engulfed by macroautophagy. This wealth of new data suggests that both autophagic pathways are potential targets for therapeutic intervention in PD and other related neurodegenerative conditions.
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92
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Sriskanthadevan S, Lee T, Lin Z, Yang D, Siu CH. Cell adhesion molecule DdCAD-1 is imported into contractile vacuoles by membrane invagination in a Ca2+- and conformation-dependent manner. J Biol Chem 2009; 284:36377-36386. [PMID: 19875452 DOI: 10.1074/jbc.m109.057257] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The cadA gene in Dictyostelium encodes a Ca(2+)-dependent cell adhesion molecule DdCAD-1 that contains two beta-sandwich domains. DdCAD-1 is synthesized in the cytoplasm as a soluble protein and then transported by contractile vacuoles to the plasma membrane for surface presentation or secretion. DdCAD-1-green fluorescent protein (GFP) fusion protein was expressed in cadA-null cells for further investigation of this unconventional protein transport pathway. Both morphological and biochemical characterizations showed that DdCAD-1-GFP was imported into contractile vacuoles. Time-lapse microscopy of transfectants revealed the transient appearance of DdCAD-1-GFP-filled vesicular structures in the lumen of contractile vacuoles, suggesting that DdCAD-1 could be imported by invagination of contractile vacuole membrane. To assess the structural requirements in this transport process, the N-terminal and C-terminal domains of DdCAD-1 were expressed separately in cells as GFP fusion proteins. Both fusion proteins failed to enter the contractile vacuole, suggesting that the integrity of DdCAD-1 is required for import. Such a requirement was also observed in in vitro reconstitution assays using His(6)-tagged fusion proteins and purified contractile vacuoles. Import of DdCAD-1 was compromised when two of its three Ca(2+)-binding sites were mutated, indicating a role for Ca(2+) in the import process. Spectral analysis showed that mutations in the Ca(2+)-binding sites resulted in subtle conformational changes. Indeed, proteins with altered conformation failed to enter the contractile vacuole, suggesting that the import signal is somehow integrated in the three-dimensional structure of DdCAD-1.
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Affiliation(s)
- Shrivani Sriskanthadevan
- Banting and Best Department of Medical Research and Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Teresa Lee
- Banting and Best Department of Medical Research and Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Zhi Lin
- Department of Biological Sciences, National University of Singapore, Singapore 117543
| | - Daiwen Yang
- Department of Biological Sciences, National University of Singapore, Singapore 117543
| | - Chi-Hung Siu
- Banting and Best Department of Medical Research and Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
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93
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Beebo A, Thomas D, Der C, Sanchez L, Leborgne-Castel N, Marty F, Schoefs B, Bouhidel K. Life with and without AtTIP1;1, an Arabidopsis aquaporin preferentially localized in the apposing tonoplasts of adjacent vacuoles. PLANT MOLECULAR BIOLOGY 2009; 70:193-209. [PMID: 19229639 DOI: 10.1007/s11103-009-9465-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Accepted: 01/30/2009] [Indexed: 05/27/2023]
Abstract
The Arabidopsis thaliana Tonoplast Intrinsic Protein 1;1 (AtTIP1;1) is a member of the tonoplast aquaporin family. The tissue-specific expression pattern and intracellular localization of AtTIP1;1 were characterized using GUS and GFP fusion genes. Results indicate that AtTIP1;1 is expressed in almost all cell types with the notable exception of meristematic cells. The highest level of AtTIP1;1 expression was detected in vessel-flanking cells in vascular bundles. AtTIP1;1-GFP fusion protein labelled the tonoplast of the central vacuole and other smaller peripheral vacuoles. The fusion protein was not found evenly distributed along the tonoplast continuum but concentrated in contact zones of tonoplasts from adjacent vacuoles and in invaginations of the central vacuole. Such invaginations may result from partially engulfed small vacuoles. A knockout mutant was isolated and characterized to gain insight into AtTIP1;1 function. No phenotypic alteration was found under optimal growth conditions indicating that AtTIP1;1 function is not essential to the plant and that some members of the TIP family may act redundantly to facilitate water flow across the tonoplast. However, a conditional root phenotype was observed when mutant plants were grown on a glycerol-containing medium.
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Affiliation(s)
- Azeez Beebo
- UMR INRA 1088/CNRS 5184/Université de Bourgogne, Plante-Microbe-Environnement, BP 86510, 21065, Dijon, France.
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94
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Abstract
The original observations and experiments dealing with autophagy were purely morphological in nature. Even though more and more molecular techniques have been introduced, experimenters are often asked to provide visual evidence of autophagic processes in order to back up data obtained via other means. In yeast as well, autophagosomes were initially defined morphologically and indirectly, by observing intravacuolar autophagic bodies that accumulate upon starvation. This can be achieved by electron microscopy, which affords very high resolution but is time consuming and costly, or by light microscopy, which is a relatively inaccurate method of scoring autophagy. A third alternative, which we present here, is to use the unique properties of the fluorescent dye FM 4-64 to follow the accumulation of autophagic bodies.
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95
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Abstract
Microautophagy is the direct uptake of soluble or particulate cellular constituents into lysosomes. Here, I describe methods to reconstitute and study this process in vitro, using vacuoles (lysosomes) from the yeast Saccharomyces cerevisiae as model organelles. Protocols to grow the cells, isolate vacuoles from them, and to induce microautophagy of soluble tracers are presented.
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96
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Two Beclin 1-binding proteins, Atg14L and Rubicon, reciprocally regulate autophagy at different stages. Nat Cell Biol 2009; 11:385-96. [PMID: 19270696 DOI: 10.1038/ncb1846] [Citation(s) in RCA: 907] [Impact Index Per Article: 60.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Accepted: 12/23/2008] [Indexed: 12/11/2022]
Abstract
Beclin 1, a protein essential for autophagy, binds to hVps34/Class III phosphatidylinositol-3-kinase and UVRAG. Here, we have identified two Beclin 1 associated proteins, Atg14L and Rubicon. Atg14L and UVRAG bind to Beclin 1 in a mutually exclusive manner, whereas Rubicon binds only to a subpopulation of UVRAG complexes; thus, three different Beclin 1 complexes exist. GFP-Atg14L localized to the isolation membrane and autophagosome, as well as to the ER and unknown puncta. Knockout of Atg14L in mouse ES cells caused a defect in autophagosome formation. GFP-Rubicon was localized at the endosome/lysosome. Knockdown of Rubicon caused enhancement of autophagy, especially at the maturation step, as well as enhancement of endocytic trafficking. These data suggest that the Beclin 1-hVps34 complex functions in two different steps of autophagy by altering the subunit composition.
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97
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Kraft C, Reggiori F, Peter M. Selective types of autophagy in yeast. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:1404-12. [PMID: 19264099 DOI: 10.1016/j.bbamcr.2009.02.006] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 02/17/2009] [Accepted: 02/18/2009] [Indexed: 12/19/2022]
Abstract
Autophagy is the process through which cytosol and organelles are sequestered into a double-membrane vesicle called an autophagosome and delivered to the vacuole/lysosome for breakdown and recycling. One of its primary roles in unicellular organisms is to regulate intracellular homeostasis and to adjust organelle numbers in response to stress such as changes in nutrient availability. In higher eukaryotes, autophagy plays also an important role in stress-response, development, cell differentiation, immunity and tumor suppression. Importantly, a misregulation in this catabolic pathway is associated with diseases such as cancer, neurodegeneration and myopathies. For a long time, starvation-induced autophagy has been considered a non-selective pathway, however, numerous recent observations revealed that autophagy can also selectively eliminate specific proteins, protein complexes and organelles. Most of these studies used yeast Saccharomyces cerevisiae as a model organism. In this compendium, we will review what is known about the mechanisms and roles of selective types of autophagy in yeast and highlight possible connections of these pathways with human diseases. In addition, we will discuss some selective types of autophagy, which have so far only been described in higher eukaryotes.
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Affiliation(s)
- Claudine Kraft
- Institute of Biochemistry, HPM, ETH Hönggerberg, 8093 Zürich, Switzerland.
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98
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Autophagy: principles and significance in health and disease. Biochim Biophys Acta Mol Basis Dis 2008; 1792:3-13. [PMID: 19022377 DOI: 10.1016/j.bbadis.2008.10.016] [Citation(s) in RCA: 253] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Revised: 10/15/2008] [Accepted: 10/17/2008] [Indexed: 12/23/2022]
Abstract
Degradation processes are important for optimal functioning of eukaryotic cells. The two major protein degradation pathways in eukaryotes are the ubiquitin-proteasome pathway and autophagy. This contribution focuses on autophagy. This process is important for survival of cells during nitrogen starvation conditions but also has a house keeping function in removing exhausted, redundant or unwanted cellular components. We present an overview of the molecular mechanism involved in three major autophagy pathways: chaperone mediated autophagy, microautophagy and macroautophagy. Various recent reports indicate that autophagy plays a crucial role in human health and disease. Examples are presented of lysosomal storage diseases and the role of autophagy in cancer, neurodegenerative diseases, defense against pathogens and cell death.
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99
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Vogiatzi T, Xilouri M, Vekrellis K, Stefanis L. Wild type alpha-synuclein is degraded by chaperone-mediated autophagy and macroautophagy in neuronal cells. J Biol Chem 2008; 283:23542-56. [PMID: 18566453 PMCID: PMC2527094 DOI: 10.1074/jbc.m801992200] [Citation(s) in RCA: 504] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 06/19/2008] [Indexed: 12/19/2022] Open
Abstract
Alpha-synuclein (ASYN) is crucial in Parkinson disease (PD) pathogenesis. Increased levels of wild type (WT) ASYN expression are sufficient to cause PD in humans. The manner of post-transcriptional regulation of ASYN levels is controversial. Previously, we had shown that WT ASYN can be degraded by chaperone-mediated autophagy (CMA) in isolated liver lysosomes. Whether this occurs in a cellular and, in particular, in a neuronal cell context is unclear. Using a mutant ASYN form that lacks the CMA recognition motif and RNA interference against the rate-limiting step in the CMA pathway, Lamp2a, we show here that CMA is indeed involved in WT ASYN degradation in PC12 and SH-SY5Y cells, and in primary cortical and midbrain neurons. However, the extent of involvement varies between cell types, potentially because of differences in compensatory mechanisms. CMA inhibition leads to an accumulation of soluble high molecular weight and detergent-insoluble species of ASYN, suggesting that CMA dysfunction may play a role in the generation of such aberrant species in PD. ASYN and Lamp2a are developmentally regulated in parallel in cortical neuron cultures and in vivo in the central nervous system, and they physically interact as indicated by co-immunoprecipitation. In contrast to previous reports, inhibition of macroautophagy, but not the proteasome, also leads to WT ASYN accumulation, suggesting that this lysosomal pathway is also involved in normal ASYN turnover. These results indicate that CMA and macroautophagy are important pathways for WT ASYN degradation in neurons and underline the importance of CMA as degradation machinery in the nervous system.
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Affiliation(s)
- Tereza Vogiatzi
- Division of Basic Neurosciences,
Biomedical Research Foundation of the Academy of Athens, Soranou Efesiou 4,
11527 Athens and Second Department of Neurology,
Attikon Hospital, University of Athens Medical School, 124 62, Athens,
Greece
| | - Maria Xilouri
- Division of Basic Neurosciences,
Biomedical Research Foundation of the Academy of Athens, Soranou Efesiou 4,
11527 Athens and Second Department of Neurology,
Attikon Hospital, University of Athens Medical School, 124 62, Athens,
Greece
| | - Kostas Vekrellis
- Division of Basic Neurosciences,
Biomedical Research Foundation of the Academy of Athens, Soranou Efesiou 4,
11527 Athens and Second Department of Neurology,
Attikon Hospital, University of Athens Medical School, 124 62, Athens,
Greece
| | - Leonidas Stefanis
- Division of Basic Neurosciences,
Biomedical Research Foundation of the Academy of Athens, Soranou Efesiou 4,
11527 Athens and Second Department of Neurology,
Attikon Hospital, University of Athens Medical School, 124 62, Athens,
Greece
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Krick R, Muehe Y, Prick T, Bremer S, Schlotterhose P, Eskelinen EL, Millen J, Goldfarb DS, Thumm M. Piecemeal microautophagy of the nucleus requires the core macroautophagy genes. Mol Biol Cell 2008; 19:4492-505. [PMID: 18701704 DOI: 10.1091/mbc.e08-04-0363] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Autophagy is a diverse family of processes that transport cytoplasm and organelles into the lysosome/vacuole lumen for degradation. During macroautophagy cargo is packaged in autophagosomes that fuse with the lysosome/vacuole. During microautophagy cargo is directly engulfed by the lysosome/vacuole membrane. Piecemeal microautophagy of the nucleus (PMN) occurs in Saccharomyces cerevisiae at nucleus-vacuole (NV) junctions and results in the pinching-off and release into the vacuole of nonessential portions of the nucleus. Previous studies concluded macroautophagy ATG genes are not absolutely required for PMN. Here we report using two biochemical assays that PMN is efficiently inhibited in atg mutant cells: PMN blebs are produced, but vesicles are rarely released into the vacuole lumen. Electron microscopy of arrested PMN structures in atg7, atg8, and atg9 mutant cells suggests that NV-junction-associated micronuclei may normally be released from the nucleus before their complete enclosure by the vacuole membrane. In this regard PMN is similar to the microautophagy of peroxisomes (micropexophagy), where the side of the peroxisome opposite the engulfing vacuole is capped by a structure called the "micropexophagy-specific membrane apparatus" (MIPA). The MIPA contains Atg proteins and facilitates terminal enclosure and fusion steps. PMN does not require the complete vacuole homotypic fusion genes. We conclude that a spectrum of ATG genes is required for the terminal vacuole enclosure and fusion stages of PMN.
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Affiliation(s)
- R Krick
- Center of Biochemistry and Molecular Cell Biology, Georg-August University, D-37073 Göttingen, Germany
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