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Rudinskiy M, Molinari M. ER-to-lysosome-associated degradation in a nutshell: mammalian, yeast, and plant ER-phagy as induced by misfolded proteins. FEBS Lett 2023; 597:1928-1945. [PMID: 37259628 DOI: 10.1002/1873-3468.14674] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Revised: 05/10/2023] [Accepted: 05/22/2023] [Indexed: 06/02/2023]
Abstract
Conserved catabolic pathways operate to remove aberrant polypeptides from the endoplasmic reticulum (ER), the major biosynthetic organelle of eukaryotic cells. The best known are the ER-associated degradation (ERAD) pathways that control the retrotranslocation of terminally misfolded proteins across the ER membrane for clearance by the cytoplasmic ubiquitin/proteasome system. In this review, we catalog folding-defective mammalian, yeast, and plant proteins that fail to engage ERAD machineries. We describe that they rather segregate in ER subdomains that eventually vesiculate. These ER-derived vesicles are captured by double membrane autophagosomes, engulfed by endolysosomes/vacuoles, or fused with degradative organelles to clear cells from their toxic cargo. These client-specific, mechanistically diverse ER-phagy pathways are grouped under the umbrella term of ER-to-lysosome-associated degradation for description in this essay.
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Affiliation(s)
- Mikhail Rudinskiy
- Università della Svizzera italiana, Lugano, Switzerland
- Institute for Research in Biomedicine, Bellinzona, Switzerland
- Department of Biology, Swiss Federal Institute of Technology, Zurich, Switzerland
| | - Maurizio Molinari
- Università della Svizzera italiana, Lugano, Switzerland
- Institute for Research in Biomedicine, Bellinzona, Switzerland
- School of Life Sciences, École Polytechnique Fédérale de Lausanne, Switzerland
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2
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Kitamura K, Homma T, Sohel MSH, Fuyuki A, Miyawaki S, Onouchi S, Saito S. Expression patterns of prosaposin and its receptors, G protein-coupled receptor (GPR) 37 and GPR37L1, in the mouse olfactory organ. Tissue Cell 2023; 82:102093. [PMID: 37075680 DOI: 10.1016/j.tice.2023.102093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 03/24/2023] [Accepted: 04/14/2023] [Indexed: 04/21/2023]
Abstract
Prosaposin is a glycoprotein conserved widely in vertebrates, because it is a precursor for saposins that are required for normal lysosomal function and thus for autophagy, and acts as a neurotrophic factor. Most tetrapods possess two kinds of olfactory neuroepithelia, namely, the olfactory epithelium (OE) and the vomeronasal epithelium (VNE). This study examined the expression patterns of prosaposin and its candidate receptors, G protein-coupled receptor (GPR) 37 and GPR37L1, in mouse OE and VNE by immunofluorescence and in situ hybridization. Prosaposin immunoreactivity was observed in the olfactory receptor neurons, vomeronasal receptor neurons, Bowman's gland (BG), and Jacobson's gland (JG). Prosaposin expression was mainly observed in mature neurons. Prosaposin mRNA expression was observed not only in these cells but also in the apical region of the VNE. GPR37 and GPR37L1 immunoreactivities were found only in the BG and/or the JG. Prosaposin was suggested to secrete and facilitate the autophagic activities of the neurons and modulate the mucus secretion in mouse olfactory organ.
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Affiliation(s)
- Kai Kitamura
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan
| | - Takeshi Homma
- Laboratory of Veterinary Anatomy, Joint Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, Japan
| | - Md Shahriar Hasan Sohel
- Laboratory of Veterinary Anatomy, Joint Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, Japan
| | - Aimi Fuyuki
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan
| | - Shingo Miyawaki
- Laboratory of Veterinary Surgery, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan
| | - Sawa Onouchi
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan; Laboratory of Veterinary Anatomy, Joint Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, Japan
| | - Shouichiro Saito
- Laboratory of Veterinary Anatomy, Faculty of Applied Biological Sciences, Gifu University, Gifu, Japan; Laboratory of Veterinary Anatomy, Joint Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, Japan.
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Al-Huseini I, Sirasanagandla SR, Babu KS, Sofin RGS, Das S. Kinase Inhibitors Involved in the Regulation of Autophagy: Molecular Concepts and Clinical Implications. Curr Med Chem 2023; 30:1502-1528. [PMID: 35078392 DOI: 10.2174/0929867329666220117114306] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 11/08/2021] [Accepted: 11/22/2021] [Indexed: 11/22/2022]
Abstract
All cells and intracellular components are remodeled and recycled in order to replace the old and damaged cells. Autophagy is a process by which damaged, and unwanted cells are degraded in the lysosomes. There are three different types of autophagy: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy has an effect on adaptive and innate immunity, suppression of any tumour, and the elimination of various microbial pathogens. The process of autophagy has both positive and negative effects, and this pertains to any specific disease or its stage of progression. Autophagy involves various processes which are controlled by various signaling pathways, such as Jun N-terminal kinase, GSK3, ERK1, Leucine-rich repeat kinase 2, and PTEN-induced putative kinase 1 and parkin RBR E3. Protein kinases are also important for the regulation of autophagy as they regulate the process of autophagy either by activation or inhibition. The present review discusses the kinase catalyzed phosphorylated reactions, the kinase inhibitors, types of protein kinase inhibitors and their binding properties to protein kinase domains, the structures of active and inactive kinases, and the hydrophobic spine structures in active and inactive protein kinase domains. The intervention of autophagy by targeting specific kinases may form the mainstay of treatment of many diseases and lead the road to future drug discovery.
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Affiliation(s)
- Isehaq Al-Huseini
- Department of Physiology, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Al-Khodh 123, Oman
| | - Srinivasa Rao Sirasanagandla
- Department of Human and Clinical Anatomy, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Al-Khodh 123, Oman
| | - Kondaveeti Suresh Babu
- Department of Biochemistry, Symbiosis Medical College for Women, Symbiosis International (Deemed) University, Pune, Maharashtra, India
| | | | - Srijit Das
- Department of Human and Clinical Anatomy, College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Al-Khodh 123, Oman
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Cell Autophagy in NASH and NASH-Related Hepatocellular Carcinoma. Int J Mol Sci 2022; 23:ijms23147734. [PMID: 35887082 PMCID: PMC9322157 DOI: 10.3390/ijms23147734] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 07/10/2022] [Accepted: 07/11/2022] [Indexed: 12/21/2022] Open
Abstract
Autophagy, a cellular self-digestion process, involves the degradation of targeted cell components such as damaged organelles, unfolded proteins, and intracellular pathogens by lysosomes. It is a major quality control system of the cell and plays an important role in cell differentiation, survival, development, and homeostasis. Alterations in the cell autophagic machinery have been implicated in several disease conditions, including neurodegeneration, autoimmunity, cancer, infection, inflammatory diseases, and aging. In non-alcoholic fatty liver disease, including its inflammatory form, non-alcoholic steatohepatitis (NASH), a decrease in cell autophagic activity, has been implicated in the initial development and progression of steatosis to NASH and hepatocellular carcinoma (HCC). We present an overview of autophagy as it occurs in mammalian cells with an insight into the emerging understanding of the role of autophagy in NASH and NASH-related HCC.
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Deneubourg C, Ramm M, Smith LJ, Baron O, Singh K, Byrne SC, Duchen MR, Gautel M, Eskelinen EL, Fanto M, Jungbluth H. The spectrum of neurodevelopmental, neuromuscular and neurodegenerative disorders due to defective autophagy. Autophagy 2022; 18:496-517. [PMID: 34130600 PMCID: PMC9037555 DOI: 10.1080/15548627.2021.1943177] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 06/10/2021] [Indexed: 12/15/2022] Open
Abstract
Primary dysfunction of autophagy due to Mendelian defects affecting core components of the autophagy machinery or closely related proteins have recently emerged as an important cause of genetic disease. This novel group of human disorders may present throughout life and comprises severe early-onset neurodevelopmental and more common adult-onset neurodegenerative disorders. Early-onset (or congenital) disorders of autophagy often share a recognizable "clinical signature," including variable combinations of neurological, neuromuscular and multisystem manifestations. Structural CNS abnormalities, cerebellar involvement, spasticity and peripheral nerve pathology are prominent neurological features, indicating a specific vulnerability of certain neuronal populations to autophagic disturbance. A typically biphasic disease course of late-onset neurodegeneration occurring on the background of a neurodevelopmental disorder further supports a role of autophagy in both neuronal development and maintenance. Additionally, an associated myopathy has been characterized in several conditions. The differential diagnosis comprises a wide range of other multisystem disorders, including mitochondrial, glycogen and lysosomal storage disorders, as well as ciliopathies, glycosylation and vesicular trafficking defects. The clinical overlap between the congenital disorders of autophagy and these conditions reflects the multiple roles of the proteins and/or emerging molecular connections between the pathways implicated and suggests an exciting area for future research. Therapy development for congenital disorders of autophagy is still in its infancy but may result in the identification of molecules that target autophagy more specifically than currently available compounds. The close connection with adult-onset neurodegenerative disorders highlights the relevance of research into rare early-onset neurodevelopmental conditions for much more common, age-related human diseases.Abbreviations: AC: anterior commissure; AD: Alzheimer disease; ALR: autophagic lysosomal reformation; ALS: amyotrophic lateral sclerosis; AMBRA1: autophagy and beclin 1 regulator 1; AMPK: AMP-activated protein kinase; ASD: autism spectrum disorder; ATG: autophagy related; BIN1: bridging integrator 1; BPAN: beta-propeller protein associated neurodegeneration; CC: corpus callosum; CHMP2B: charged multivesicular body protein 2B; CHS: Chediak-Higashi syndrome; CMA: chaperone-mediated autophagy; CMT: Charcot-Marie-Tooth disease; CNM: centronuclear myopathy; CNS: central nervous system; DNM2: dynamin 2; DPR: dipeptide repeat protein; DVL3: disheveled segment polarity protein 3; EPG5: ectopic P-granules autophagy protein 5 homolog; ER: endoplasmic reticulum; ESCRT: homotypic fusion and protein sorting complex; FIG4: FIG4 phosphoinositide 5-phosphatase; FTD: frontotemporal dementia; GBA: glucocerebrosidase; GD: Gaucher disease; GRN: progranulin; GSD: glycogen storage disorder; HC: hippocampal commissure; HD: Huntington disease; HOPS: homotypic fusion and protein sorting complex; HSPP: hereditary spastic paraparesis; LAMP2A: lysosomal associated membrane protein 2A; MEAX: X-linked myopathy with excessive autophagy; mHTT: mutant huntingtin; MSS: Marinesco-Sjoegren syndrome; MTM1: myotubularin 1; MTOR: mechanistic target of rapamycin kinase; NBIA: neurodegeneration with brain iron accumulation; NCL: neuronal ceroid lipofuscinosis; NPC1: Niemann-Pick disease type 1; PD: Parkinson disease; PtdIns3P: phosphatidylinositol-3-phosphate; RAB3GAP1: RAB3 GTPase activating protein catalytic subunit 1; RAB3GAP2: RAB3 GTPase activating non-catalytic protein subunit 2; RB1: RB1-inducible coiled-coil protein 1; RHEB: ras homolog, mTORC1 binding; SCAR20: SNX14-related ataxia; SENDA: static encephalopathy of childhood with neurodegeneration in adulthood; SNX14: sorting nexin 14; SPG11: SPG11 vesicle trafficking associated, spatacsin; SQSTM1: sequestosome 1; TBC1D20: TBC1 domain family member 20; TECPR2: tectonin beta-propeller repeat containing 2; TSC1: TSC complex subunit 1; TSC2: TSC complex subunit 2; UBQLN2: ubiquilin 2; VCP: valosin-containing protein; VMA21: vacuolar ATPase assembly factor VMA21; WDFY3/ALFY: WD repeat and FYVE domain containing protein 3; WDR45: WD repeat domain 45; WDR47: WD repeat domain 47; WMS: Warburg Micro syndrome; XLMTM: X-linked myotubular myopathy; ZFYVE26: zinc finger FYVE-type containing 26.
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Affiliation(s)
- Celine Deneubourg
- Department of Basic and Clinical Neuroscience, IoPPN, King’s College London, London, UK
| | - Mauricio Ramm
- Institute of Biomedicine, University of Turku, Turku, Finland
| | - Luke J. Smith
- Randall Division of Cell and Molecular Biophysics, Muscle Signalling Section, King’s College London, London, UK
| | - Olga Baron
- Wolfson Centre for Age-Related Diseases, King’s College London, London, UK
| | - Kritarth Singh
- Department of Cell and Developmental Biology, University College London, London, UK
| | - Susan C. Byrne
- Department of Paediatric Neurology, Neuromuscular Service, Evelina’s Children Hospital, Guy’s & St. Thomas’ Hospital NHS Foundation Trust, London, UK
| | - Michael R. Duchen
- Department of Cell and Developmental Biology, University College London, London, UK
| | - Mathias Gautel
- Randall Division of Cell and Molecular Biophysics, Muscle Signalling Section, King’s College London, London, UK
| | - Eeva-Liisa Eskelinen
- Institute of Biomedicine, University of Turku, Turku, Finland
- Molecular and Integrative Biosciences Research Programme, University of Helsinki, Helsinki, Finland
| | - Manolis Fanto
- Department of Basic and Clinical Neuroscience, IoPPN, King’s College London, London, UK
| | - Heinz Jungbluth
- Department of Basic and Clinical Neuroscience, IoPPN, King’s College London, London, UK
- Randall Division of Cell and Molecular Biophysics, Muscle Signalling Section, King’s College London, London, UK
- Department of Paediatric Neurology, Neuromuscular Service, Evelina’s Children Hospital, Guy’s & St. Thomas’ Hospital NHS Foundation Trust, London, UK
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Reggiori F, Molinari M. ER-phagy: mechanisms, regulation and diseases connected to the lysosomal clearance of the endoplasmic reticulum. Physiol Rev 2022; 102:1393-1448. [PMID: 35188422 PMCID: PMC9126229 DOI: 10.1152/physrev.00038.2021] [Citation(s) in RCA: 43] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
ER-phagy (reticulo-phagy) defines the degradation of portions of the endoplasmic reticulum (ER) within lysosomes or vacuoles. It is part of the self-digestion (i.e., auto-phagic) programs recycling cytoplasmic material and organelles, which rapidly mobilize metabolites in cells confronted with nutrient shortage. Moreover, selective clearance of ER subdomains participates to the control of ER size and activity during ER stress, the re-establishment of ER homeostasis after ER stress resolution and the removal of ER parts, in which aberrant and potentially cytotoxic material has been segregated. ER-phagy relies on the individual and/or concerted activation of the ER-phagy receptors, ER peripheral or integral membrane proteins that share the presence of LC3/Atg8-binding motifs in their cytosolic domains. ER-phagy involves the physical separation of portions of the ER from the bulk ER network, and their delivery to the endolysosomal/vacuolar catabolic district. This last step is accomplished by a variety of mechanisms including macro-ER-phagy (in which ER fragments are sequestered by double-membrane autophagosomes that eventually fuse with lysosomes/vacuoles), micro-ER-phagy (in which ER fragments are directly engulfed by endosomes/lysosomes/vacuoles), or direct fusion of ER-derived vesicles with lysosomes/vacuoles. ER-phagy is dysfunctional in specific human diseases and its regulators are subverted by pathogens, highlighting its crucial role for cell and organism life.
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Affiliation(s)
- Fulvio Reggiori
- Department of Biomedical Sciences of Cells & Systems, grid.4830.fUniversity of Groningen, Netherlands
| | - Maurizio Molinari
- Protein Folding and Quality Control, grid.7722.0Institute for Research in Biomedicine, Bellinzona, Switzerland
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Molinari M. ER-phagy responses in yeast, plants, and mammalian cells and their crosstalk with UPR and ERAD. Dev Cell 2021; 56:949-966. [PMID: 33765438 DOI: 10.1016/j.devcel.2021.03.005] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 02/23/2021] [Accepted: 02/27/2021] [Indexed: 12/24/2022]
Abstract
ER-phagy, literally endoplasmic reticulum (ER)-eating, defines the constitutive or regulated clearance of ER portions within metazoan endolysosomes or yeast and plant vacuoles. The advent of electron microscopy led to the first observations of ER-phagy over 60 years ago, but only recently, with the discovery of a set of regulatory proteins named ER-phagy receptors, has it been dissected mechanistically. ER-phagy receptors are activated by a variety of pleiotropic and ER-centric stimuli. They promote ER fragmentation and engage luminal, membrane-bound, and cytosolic factors, eventually driving lysosomal clearance of select ER domains along with their content. After short historical notes, this review introduces the concept of ER-phagy responses (ERPRs). ERPRs ensure lysosomal clearance of ER portions expendable during nutrient shortage, nonfunctional, present in excess, or containing misfolded proteins. They cooperate with unfolded protein responses (UPRs) and with ER-associated degradation (ERAD) in determining ER size, function, and homeostasis.
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Affiliation(s)
- Maurizio Molinari
- Università della Svizzera italiana (USI), Faculty of Biomedical Sciences, Institute for Research in Biomedicine, CH-6500 Bellinzona, Switzerland; School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
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8
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Ji C, Zhao H, Chen D, Zhang H, Zhao YG. β-propeller proteins WDR45 and WDR45B regulate autophagosome maturation into autolysosomes in neural cells. Curr Biol 2021; 31:1666-1677.e6. [PMID: 33636118 DOI: 10.1016/j.cub.2021.01.081] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 10/26/2020] [Accepted: 01/22/2021] [Indexed: 01/23/2023]
Abstract
Mutations in WDR45 and WDR45B cause the human neurological diseases β-propeller protein-associated neurodegeneration (BPAN) and intellectual disability (ID), respectively. WDR45 and WDR45B, along with WIPI1 and WIPI2, belong to a WD40 repeat-containing phosphatidylinositol-3-phosphate (PI(3)P)-binding protein family. Their yeast homolog Atg18 forms a complex with Atg2 and is required for autophagosome formation in part by tethering isolation membranes (IMs) (autophagosome precursor) to the endoplasmic reticulum (ER) to supply lipid for IM expansion in the autophagy pathway. The exact functions of WDR45/45B are unclear. We show here that WDR45/45B are specifically required for neural autophagy. In Wdr45/45b-depleted cells, the size of autophagosomes is decreased, and this is rescued by overexpression of ATG2A, providing in vivo evidence for the lipid transfer activity of ATG2-WIPI complexes. WDR45/45B are dispensable for the closure of autophagosomes but essential for the progression of autophagosomes into autolysosomes. WDR45/45B interact with the tether protein EPG5 and target it to late endosomes/lysosomes to promote autophagosome maturation. In the absence of Wdr45/45b, formation of the fusion machinery, consisting of SNARE proteins and EPG5, is dampened. BPAN- and ID-related mutations of WDR45/45B fail to rescue the autophagy defects in Wdr45/45b-deficient cells, possibly due to their impaired binding to EPG5. Promoting autophagosome maturation by inhibiting O-GlcNAcylation increases SNARE complex formation and facilitates the fusion of autophagosomes with late endosomes/lysosomes in Wdr45/45b double knockout (DKO) cells. Thus, our results uncover a novel function of WDR45/45B in autophagosome-lysosome fusion and provide molecular insights into the development of WDR45/WDR45B mutation-associated diseases.
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Affiliation(s)
- Cuicui Ji
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, No. 15 Datun Road, Chaoyang District, Beijing 100101, P.R. China
| | - Hongyu Zhao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, No. 15 Datun Road, Chaoyang District, Beijing 100101, P.R. China
| | - Di Chen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, No. 15 Datun Road, Chaoyang District, Beijing 100101, P.R. China
| | - Hong Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, No. 15 Datun Road, Chaoyang District, Beijing 100101, P.R. China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, P.R. China; Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Yan G Zhao
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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Loi M, Marazza A, Molinari M. Endoplasmic Reticulum (ER) and ER-Phagy. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2021; 59:99-114. [PMID: 34050863 DOI: 10.1007/978-3-030-67696-4_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The endoplasmic reticulum (ER) is a biosynthetic organelle in eukaryotic cells. Its capacity to produce proteins, lipids and oligosaccharides responds to physiologic and pathologic demand. The transcriptional and translational unfolded protein response (UPR) programs increase ER size and activity. In contrast, ER-phagy programs in all their flavors select ER subdomains for lysosomal clearance. These programs are activated by nutrient deprivation, accumulation of excess ER (recov-ER-phagy), production of misfolded proteins that cannot be degraded by ER-associated degradation and that are removed from cells by the so-called ER-to-lysosome-associated degradation (ERLAD). Selection of ER subdomains to be cleared from cells relies on ER-phagy receptors, a class of membrane-bound proteins displaying cytosolic domains that engage the cytosolic ubiquitin-like protein LC3. Mechanistically, ER clearance proceeds via macro-ER-phagy, micro-ER-phagy and LC3-regulated vesicular delivery.
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Affiliation(s)
- Marisa Loi
- Università della Svizzera italiana, Lugano, Switzerland
- Institute for Research in Biomedicine, Bellinzona, Switzerland
| | - Alessandro Marazza
- Università della Svizzera italiana, Lugano, Switzerland
- Institute for Research in Biomedicine, Bellinzona, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Maurizio Molinari
- Università della Svizzera italiana, Lugano, Switzerland.
- Institute for Research in Biomedicine, Bellinzona, Switzerland.
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
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Perrotta I. ER-phagy in human atherosclerosis: an exploratory ultrastructural study. Ultrastruct Pathol 2020; 44:489-495. [PMID: 33118423 DOI: 10.1080/01913123.2020.1840468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Autophagy is a vacuolar self-digesting mechanism responsible for the removal of damaged organelles, indigestible aggregates, and nonfunctional long-lived proteins by lysosome. Autophagy is dynamically connected to the endoplasmic reticulum (ER) in several ways. It is capable to counteract the possible harmful effects linked to the impairment of protein folding in the ER; the ER has been proposed as the source for autophagosomal membranes. Also, the ER itself can undergo a selective form of autophagy (called ER-phagy) which ensures the maintenance of ER's morphology and function. Autophagy has been widely investigated in the cardiovascular system however there is no evidence to date regarding the occurrence of ER-phagy into the blood vessel wall. This study has been undertaken to explore the existence of this selective control mechanism in the cells of human atherosclerotic plaques. Transmission Electron Microscopy (TEM) analysis revealed that in the plaque cells the smooth ER profiles reorganized into concentric whorls and closely packed membranes arranged in curved and parallel arrays. Circular, often ring-shaped, ER membranes studded with ribosomes and enclosed in a sequestering vesicle have been also frequently observed. This preliminary study demonstrates the existence of a distinct machinery for the specific turnover of ER membranes in human atherosclerosis and provides the first ultrastructural description of ER-phagy in the diseased vascular tissue. These results may open new perspectives for future investigation in the cardiovascular field.
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Affiliation(s)
- Ida Perrotta
- Centre for Microscopy and Microanalysis, Transmission Electron Microscopy Laboratory - Department of Biology, Ecology and Earth Sciences (Di.B.E.S.T.), University of Calabria , Cosenza, Italy
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11
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Øynebråten I. Involvement of autophagy in MHC class I antigen presentation. Scand J Immunol 2020; 92:e12978. [PMID: 32969499 PMCID: PMC7685157 DOI: 10.1111/sji.12978] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 08/24/2020] [Accepted: 09/13/2020] [Indexed: 12/17/2022]
Abstract
MHC class I molecules on the cellular surface display peptides that either derive from endogenous proteins (self or viral), or from endocytosis of molecules, dying cells or pathogens. The conventional antigen‐processing pathway for MHC class I presentation depends on proteasome‐mediated degradation of the protein followed by transporter associated with antigen‐processing (TAP)‐mediated transport of the generated peptides into the endoplasmic reticulum (ER). Here, peptides are loaded onto MHC I molecules before transportation to the cell surface. However, several alternative mechanisms have emerged. These include TAP‐independent mechanisms, the vacuolar pathway and involvement of autophagy. Autophagy is a cell intrinsic recycling system. It also functions as a defence mechanism that removes pathogens and damaged endocytic compartments from the cytosol. Therefore, it appears likely that autophagy would intersect with the MHC class I presentation pathway to alarm CD8+ T cells of an ongoing intracellular infection. However, the importance of autophagy as a source of antigen for presentation on MHC I molecules remains to be defined. Here, original research papers which suggest involvement of autophagy in MHC I antigen presentation are reviewed. The antigens are from herpesvirus, cytomegalovirus and chlamydia. The studies point towards autophagy as important in MHC class I presentation of endogenous proteins during conditions of immune evasion. Because autophagy is a regulated process which is induced upon activation of, for example, pattern recognition receptors (PRRs), it will be crucial to use relevant stimulatory conditions together with primary cells when aiming to confirm the importance of autophagy in MHC class I antigen presentation in future studies.
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Affiliation(s)
- Inger Øynebråten
- Tumor Immunology Lab, Department of Pathology, Rikshospitalet, Oslo University Hospital, Oslo, Norway
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12
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Patak J, Faraone SV, Zhang-James Y. Sodium hydrogen exchanger 9 NHE9 (SLC9A9) and its emerging roles in neuropsychiatric comorbidity. Am J Med Genet B Neuropsychiatr Genet 2020; 183:289-305. [PMID: 32400953 DOI: 10.1002/ajmg.b.32787] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 12/09/2019] [Accepted: 02/22/2020] [Indexed: 12/16/2022]
Abstract
Variations in SLC9A9 gene expression and protein function are associated with multiple human diseases, which range from Attention-deficit/hyperactivity disorder (ADHD) to glioblastoma multiforme. In an effort to determine the full spectrum of human disease associations with SLC9A9, we performed a systematic review of the literature. We also review SLC9A9's biochemistry, protein structure, and function, as well as its interacting partners with the goal of identifying mechanisms of disease and druggable targets. We report gaps in the literature regarding the genes function along with consistent trends in disease associations that can be used to further research into treating the respective diseases. We report that SLC9A9 has strong associations with neuropsychiatric diseases and various cancers. Interestingly, we find strong overlap in SLC9A9 disease associations and propose a novel role for SLC9A9 in neuropsychiatric comorbidity. In conclusion, SLC9A9 is a multifunctional protein that, through both its endosome regulatory function and its protein-protein interaction network, has the ability to modulate signaling axes, such as the PI3K pathway, among others.
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Affiliation(s)
- Jameson Patak
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, New York, USA.,College of Medicine, MD Program, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Stephen V Faraone
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, New York, USA.,Department of Psychiatry and Behavioral Sciences, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Yanli Zhang-James
- Department of Psychiatry and Behavioral Sciences, SUNY Upstate Medical University, Syracuse, New York, USA
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13
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Ochaba J, Powers AF, Tremble KA, Greenlee S, Post NM, Matson JE, MacLeod AR, Guo S, Aghajan M. A novel and translational role for autophagy in antisense oligonucleotide trafficking and activity. Nucleic Acids Res 2020; 47:11284-11303. [PMID: 31612951 PMCID: PMC6868497 DOI: 10.1093/nar/gkz901] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 09/13/2019] [Accepted: 10/01/2019] [Indexed: 01/26/2023] Open
Abstract
Endocytosis is a mechanism by which cells sense their environment and internalize various nutrients, growth factors and signaling molecules. This process initiates at the plasma membrane, converges with autophagy, and terminates at the lysosome. It is well-established that cellular uptake of antisense oligonucleotides (ASOs) proceeds through the endocytic pathway; however, only a small fraction escapes endosomal trafficking while the majority are rendered inactive in the lysosome. Since these pathways converge and share common molecular machinery, it is unclear if autophagy-related trafficking participates in ASO uptake or whether modulation of autophagy affects ASO activity and localization. To address these questions, we investigated the effects of autophagy modulation on ASO activity in cells and mice. We found that enhancing autophagy through small-molecule mTOR inhibition, serum-starvation/fasting, and ketogenic diet, increased ASO-mediated target reduction in vitro and in vivo. Additionally, autophagy activation enhanced the localization of ASOs into autophagosomes without altering intracellular concentrations or trafficking to other compartments. These results support a novel role for autophagy and the autophagosome as a previously unidentified compartment that participates in and contributes to enhanced ASO activity. Further, we demonstrate non-chemical methods to enhance autophagy and subsequent ASO activity using translatable approaches such as fasting or ketogenic diet.
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Affiliation(s)
- Joseph Ochaba
- Ionis Pharmaceuticals, Inc., Carlsbad, CA 92010, USA
| | | | | | | | - Noah M Post
- Ionis Pharmaceuticals, Inc., Carlsbad, CA 92010, USA
| | - John E Matson
- Ionis Pharmaceuticals, Inc., Carlsbad, CA 92010, USA
| | | | - Shuling Guo
- Ionis Pharmaceuticals, Inc., Carlsbad, CA 92010, USA
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14
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Autophagy in trimethyltin-induced neurodegeneration. J Neural Transm (Vienna) 2020; 127:987-998. [PMID: 32451631 DOI: 10.1007/s00702-020-02210-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 05/15/2020] [Indexed: 02/07/2023]
Abstract
Autophagy is a degradative process playing an important role in removing misfolded or aggregated proteins, clearing damaged organelles, such as mitochondria and endoplasmic reticulum, as well as eliminating intracellular pathogens. The autophagic process is important for balancing sources of energy at critical developmental stages and in response to nutrient stress. Recently, autophagy has been involved in the pathophysiology of neurodegenerative diseases although its beneficial (pro-survival) or detrimental (pro-death) role remains controversial. In the present review, we discuss the role of autophagy following intoxication with trimethyltin (TMT), an organotin compound that induces severe hippocampal neurodegeneration associated with astrocyte and microglia activation. TMT is considered a useful tool to study the molecular mechanisms occurring in human neurodegenerative diseases such as Alzheimer's disease and temporal lobe epilepsy. This is also relevant in the field of environmental safety, since organotin compounds are used as heat stabilizers in polyvinyl chloride polymers, industrial and agricultural biocides, and as industrial chemical catalysts.
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15
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Malla SR, Krueger B, Wartmann T, Sendler M, Mahajan UM, Weiss FU, Thiel FG, De Boni C, Gorelick FS, Halangk W, Aghdassi AA, Reinheckel T, Gukovskaya AS, Lerch MM, Mayerle J. Early trypsin activation develops independently of autophagy in caerulein-induced pancreatitis in mice. Cell Mol Life Sci 2020; 77:1811-1825. [PMID: 31363815 PMCID: PMC8221268 DOI: 10.1007/s00018-019-03254-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 07/16/2019] [Accepted: 07/24/2019] [Indexed: 12/18/2022]
Abstract
Premature intrapancreatic trypsinogen activation is widely regarded as an initiating event for acute pancreatitis. Previous studies have alternatively implicated secretory vesicles, endosomes, lysosomes, or autophagosomes/autophagolysosomes as the primary site of trypsinogen activation, from which a cell-damaging proteolytic cascade originates. To identify the subcellular compartment of initial trypsinogen activation we performed a time-resolution analysis of the first 12 h of caerulein-induced pancreatitis in transgenic light chain 3 (LC3)-GFP autophagy reporter mice. Intrapancreatic trypsin activity increased within 60 min and serum amylase within 2 h, but fluorescent autophagosome formation only by 4 h of pancreatitis in parallel with a shift from cytosolic LC3-I to membranous LC3-II on Western blots. At 60 min, activated trypsin in heavier subcellular fractions was co-distributed with cathepsin B, but not with the autophagy markers LC3 or autophagy protein 16 (ATG16). Supramaximal caerulein stimulation of primary pancreatic acini derived from LC3-GFP mice revealed that trypsinogen activation is independent of autophagolysosome formation already during the first 15 min of exposure to caerulein. Co-localization studies (with GFP-LC3 autophagosomes versus Ile-Pro-Arg-AMC trypsin activity and immunogold-labelling of lysosomal-associated membrane protein 2 [LAMP-2] versus trypsinogen activation peptide [TAP]) indicated active trypsin in autophagolysosomes only at the later timepoints. In conclusion, during the initiating phase of caerulein-induced pancreatitis, premature protease activation develops independently of autophagolysosome formation and in vesicles arising from the secretory pathway. However, autophagy is likely to regulate overall intracellular trypsin activity during the later stages of this disease.
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Affiliation(s)
- Sudarshan R Malla
- Department of Medicine A, University Medicine Greifswald, Ferdinand-Sauerbruchstrasse, Greifswald, 17475, Germany
- Veterans Affairs Greater Los Angeles Healthcare System, David Geffen School of Medicine, Southern California Research Center for Alcoholic Liver and Pancreatic Disease and Cirrhosis, University of California at Los Angeles, Los Angeles, CA, 90073, USA
| | - Burkhard Krueger
- Division of Medical Biology, University of Rostock, Rostock, 18051, Germany
| | - Thomas Wartmann
- Division of Experimental Surgery, University of Magdeburg, Magdeburg, 39120, Germany
| | - Matthias Sendler
- Department of Medicine A, University Medicine Greifswald, Ferdinand-Sauerbruchstrasse, Greifswald, 17475, Germany
| | - Ujjwal M Mahajan
- Department of Medicine A, University Medicine Greifswald, Ferdinand-Sauerbruchstrasse, Greifswald, 17475, Germany
- Department of Medicine II, Ludwigs-Maximilians University Munich, 80539, Munich, Germany
| | - F Ulrich Weiss
- Department of Medicine A, University Medicine Greifswald, Ferdinand-Sauerbruchstrasse, Greifswald, 17475, Germany
| | - Franziska G Thiel
- Department of Medicine A, University Medicine Greifswald, Ferdinand-Sauerbruchstrasse, Greifswald, 17475, Germany
| | - Carina De Boni
- Division of Experimental Surgery, University of Magdeburg, Magdeburg, 39120, Germany
| | | | - Walter Halangk
- Division of Experimental Surgery, University of Magdeburg, Magdeburg, 39120, Germany
| | - Ali A Aghdassi
- Department of Medicine A, University Medicine Greifswald, Ferdinand-Sauerbruchstrasse, Greifswald, 17475, Germany
| | - Thomas Reinheckel
- Institute of Molecular Medicine and Cell Research, University of Freiburg, Freiburg, 79104, Germany
| | - Anna S Gukovskaya
- Veterans Affairs Greater Los Angeles Healthcare System, David Geffen School of Medicine, Southern California Research Center for Alcoholic Liver and Pancreatic Disease and Cirrhosis, University of California at Los Angeles, Los Angeles, CA, 90073, USA
| | - Markus M Lerch
- Department of Medicine A, University Medicine Greifswald, Ferdinand-Sauerbruchstrasse, Greifswald, 17475, Germany.
| | - Julia Mayerle
- Department of Medicine A, University Medicine Greifswald, Ferdinand-Sauerbruchstrasse, Greifswald, 17475, Germany
- Department of Medicine II, Ludwigs-Maximilians University Munich, 80539, Munich, Germany
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16
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Proteostasis Failure in Neurodegenerative Diseases: Focus on Oxidative Stress. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2020; 2020:5497046. [PMID: 32308803 PMCID: PMC7140146 DOI: 10.1155/2020/5497046] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 03/03/2020] [Indexed: 12/11/2022]
Abstract
Protein homeostasis or proteostasis is an essential balance of cellular protein levels mediated through an extensive network of biochemical pathways that regulate different steps of the protein quality control, from the synthesis to the degradation. All proteins in a cell continuously turn over, contributing to development, differentiation, and aging. Due to the multiple interactions and connections of proteostasis pathways, exposure to stress conditions may cause various types of protein damage, altering cellular homeostasis and disrupting the entire network with additional cellular stress. Furthermore, protein misfolding and/or alterations during protein synthesis results in inactive or toxic proteins, which may overload the degradation mechanisms. The maintenance of a balanced proteome, preventing the formation of impaired proteins, is accomplished by two major catabolic routes: the ubiquitin proteasomal system (UPS) and the autophagy-lysosomal system. The proteostasis network is particularly important in nondividing, long-lived cells, such as neurons, as its failure is implicated with the development of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. These neurological disorders share common risk factors such as aging, oxidative stress, environmental stress, and protein dysfunction, all of which alter cellular proteostasis, suggesting that general mechanisms controlling proteostasis may underlay the etiology of these diseases. In this review, we describe the major pathways of cellular proteostasis and discuss how their disruption contributes to the onset and progression of neurodegenerative diseases, focusing on the role of oxidative stress.
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17
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Wilkinson S. Emerging Principles of Selective ER Autophagy. J Mol Biol 2020; 432:185-205. [PMID: 31100386 PMCID: PMC6971691 DOI: 10.1016/j.jmb.2019.05.012] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 05/07/2019] [Accepted: 05/07/2019] [Indexed: 12/13/2022]
Abstract
The endoplasmic reticulum (ER) is a fundamental organelle in cellular metabolism and signal transduction. It is subject to complex, dynamic sculpting of morphology and composition. Degradation of ER content has an important role to play here. Indeed, a major emerging player in ER turnover is ER-phagy, the degradation of ER fragments by selective autophagy, particularly macroautophagy. This article proposes a number of unifying principles of ER-phagy mechanism and compares these with other selective autophagy pathways. A perspective on the likely roles of ER-phagy in determining cell fate is provided. Emerging related forms of intracellular catabolism of the ER or contents, including ER-phagy by microautophagy and selective ER protein removal via the lysosome, are outlined for comparison. Unresolved questions regarding the mechanism of ER-phagy and its significance in cellular and organismal health are put forward. This review concludes with a perspective on how this fundamental knowledge might inform future clinical developments.
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Affiliation(s)
- Simon Wilkinson
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, EH4 2XR, United Kingdom
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18
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The Synaptic Autophagy Cycle. J Mol Biol 2019; 432:2589-2604. [PMID: 31866297 DOI: 10.1016/j.jmb.2019.12.028] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/10/2019] [Accepted: 12/12/2019] [Indexed: 02/08/2023]
Abstract
Macroautophagy (hereafter referred to as autophagy) is an evolutionarily conserved pathway in which proteins and organelles are delivered to the lysosome for degradation. In neurons, autophagy was originally described as associated with disease states and neuronal survival. Over the last decade, however, evidence has accumulated that autophagy controls synaptic function in both the axon and dendrite. Here, we review this literature, highlighting the role of autophagy in the pre- and postsynapse, synaptic plasticity, and behavior. We end by discussing open questions in the field of synaptic autophagy.
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19
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Stolz A, Grumati P. The various shades of ER-phagy. FEBS J 2019; 286:4642-4649. [PMID: 31386802 PMCID: PMC6916603 DOI: 10.1111/febs.15031] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 07/16/2019] [Accepted: 08/02/2019] [Indexed: 12/18/2022]
Abstract
Endoplasmic reticulum (ER) is a large and dynamic cellular organelle. ER morphology consists of sheets, tubules, matrixes, and contact sites shared with other membranous organelles. The capacity of the ER to fulfill its numerous biological functions depends on its continuous remodeling and the quality control of its proteome. Selective turnover of the ER by autophagy, termed ER‐phagy, plays an important role in maintaining ER homeostasis. ER network integrity and turnover rely on specific ER‐phagy receptors, which influence and coordinate alterations in ER morphology and the degradation of ER contents and membranes via the lysosome, by interacting with the LC3/GABARAP family. In this commentary, we discuss general principles and identify the major players in this recently characterized form of selective autophagy, while simultaneously highlighting open questions in the field.
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Affiliation(s)
- Alexandra Stolz
- Structural Genomics Consortium, BMLS, Goethe University, Frankfurt, Germany.,Institute of Biochemistry 2, Goethe University School of Medicine, Frankfurt, Germany
| | - Paolo Grumati
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
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20
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Wilkinson S. ER-phagy: shaping up and destressing the endoplasmic reticulum. FEBS J 2019; 286:2645-2663. [PMID: 31116513 PMCID: PMC6772018 DOI: 10.1111/febs.14932] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 04/09/2019] [Accepted: 05/20/2019] [Indexed: 12/16/2022]
Abstract
The endoplasmic reticulum (ER) network has central roles in metabolism and cellular organization. The ER undergoes dynamic alterations in morphology, molecular composition and functional specification. Remodelling of the network under fluctuating conditions enables the continual performance of ER functions and minimizes stress. Recent data have revealed that selective autophagy‐mediated degradation of ER fragments, or ER‐phagy, fundamentally contributes to this remodelling. This review provides a perspective on established views of selective autophagy, comparing these with emerging mechanisms of ER‐phagy and related processes. The text discusses the impact of ER‐phagy on the function of the ER‐ and the cell, both in normal physiology and when dysregulated within disease settings. Finally, unanswered questions regarding the mechanisms and significance of ER‐phagy are highlighted.
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Affiliation(s)
- Simon Wilkinson
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, UK
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21
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The Late Endosomal Pathway Regulates the Ciliary Targeting of Tetraspanin Protein Peripherin 2. J Neurosci 2019; 39:3376-3393. [PMID: 30819798 PMCID: PMC6495125 DOI: 10.1523/jneurosci.2811-18.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 01/18/2019] [Accepted: 02/10/2019] [Indexed: 12/11/2022] Open
Abstract
Peripherin 2 (PRPH2) is a tetraspanin protein concentrated in the light-sensing cilium (called the outer segment) of the vertebrate photoreceptor. The mechanism underlying the ciliary targeting of PRPH2 and the etiology of cone dystrophy caused by PRPH2 mutations remain elusive. Here we show that the late endosome (LE) is the main waystation that critically sorts newly synthesized PRPH2 to the cilium. PRPH2 is expressed in the luminal membrane of the LE. We delineate multiple C-terminal motifs of PRPH2 that distinctively regulate its LE and ciliary targeting through ubiquitination and binding to ESCRT (Endosomal Sorting Complexes Required for Transport) component Hrs. Using the newly developed TetOn-inducible system in transfected male and female mouse cones in vivo, we show that the entry of nascent PRPH2 into the cone outer segment can be blocked by either cone dystrophy-causing C-terminal mutations of PRPH2, or by short-term perturbation of the LE or recycling endosomal traffic. These findings open new avenues of research to explore the biological role of the LE in the biosynthetic pathway and the etiology of cone dystrophy caused by PRPH2 mutations and/or malfunctions of the LE.SIGNIFICANCE STATEMENT Peripherin 2 (PRPH2) is a tetraspanin protein abundantly expressed in the light-sensing cilium, the outer segment, of the vertebrate photoreceptor. The mechanism underlying the ciliary transport of PRPH2 is unclear. The present study reveals a novel ciliary targeting pathway, in which the newly synthesized PRPH2 is first targeted to the lumen of the late endosome (LE) en route to the cilia. We deciphered the protein motifs and the machinery that regulates the LE trafficking of PRPH2. Using a novel TetOn-inducible system in transfected mouse cones, we showed that the LE pathway of PRPH2 is critical for its outer segment expression. A cone dystrophy-causing mutation impairs the LE and ciliary targeting of PRPH2, implicating the relevance of LE to cone/macular degenerative diseases.
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22
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Zhao YG, Zhang H. Autophagosome maturation: An epic journey from the ER to lysosomes. J Cell Biol 2018; 218:757-770. [PMID: 30578282 PMCID: PMC6400552 DOI: 10.1083/jcb.201810099] [Citation(s) in RCA: 209] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 12/05/2018] [Accepted: 12/05/2018] [Indexed: 12/23/2022] Open
Abstract
Macroautophagy involves the sequestration of cytoplasmic contents in a double-membrane autophagosome and their delivery to lysosomes for degradation. In multicellular organisms, nascent autophagosomes fuse with vesicles originating from endolysosomal compartments before forming degradative autolysosomes, a process known as autophagosome maturation. ATG8 family members, tethering factors, Rab GTPases, and SNARE proteins act coordinately to mediate fusion of autophagosomes with endolysosomal vesicles. The machinery mediating autophagosome maturation is under spatiotemporal control and provides regulatory nodes to integrate nutrient availability with autophagy activity. Dysfunction of autophagosome maturation is associated with various human diseases, including neurodegenerative diseases, Vici syndrome, cancer, and lysosomal storage disorders. Understanding the molecular mechanisms underlying autophagosome maturation will provide new insights into the pathogenesis and treatment of these diseases.
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Affiliation(s)
- Yan G Zhao
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA
| | - Hong Zhang
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China .,National Laboratory of Biomacromolecules, Chinese Academy of Sciences Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
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23
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Smith MD, Harley ME, Kemp AJ, Wills J, Lee M, Arends M, von Kriegsheim A, Behrends C, Wilkinson S. CCPG1 Is a Non-canonical Autophagy Cargo Receptor Essential for ER-Phagy and Pancreatic ER Proteostasis. Dev Cell 2017; 44:217-232.e11. [PMID: 29290589 PMCID: PMC5791736 DOI: 10.1016/j.devcel.2017.11.024] [Citation(s) in RCA: 282] [Impact Index Per Article: 40.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 11/02/2017] [Accepted: 11/29/2017] [Indexed: 12/11/2022]
Abstract
Mechanisms of selective autophagy of the ER, known as ER-phagy, require molecular delineation, particularly in vivo. It is unclear how these events control ER proteostasis and cellular health. Here, we identify cell-cycle progression gene 1 (CCPG1), an ER-resident protein with no known physiological role, as a non-canonical cargo receptor that directly binds to core autophagy proteins via an LIR motif to mammalian ATG8 proteins and, independently and via a discrete motif, to FIP200. These interactions facilitate ER-phagy. The CCPG1 gene is inducible by the unfolded protein response and thus directly links ER stress to ER-phagy. In vivo, CCPG1 protects against ER luminal protein aggregation and consequent unfolded protein response hyperactivation and tissue injury of the exocrine pancreas. Thus, via identification of this autophagy protein, we describe an unexpected molecular mechanism of ER-phagy and provide evidence that this may be physiologically relevant in ER luminal proteostasis. CCPG1 is an ER stress-inducible ER-phagy cargo receptor in mammals CCPG1 binds directly to ATG8 proteins and FIP200 via distinct peptide motifs CCPG1 lysosomal degradation and ER-phagy both require these interactions CCPG1 maintains normal ER luminal proteostasis in pancreatic acinar cells in vivo
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Affiliation(s)
- Matthew D Smith
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Margaret E Harley
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Alain J Kemp
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Jimi Wills
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Martin Lee
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Mark Arends
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Alex von Kriegsheim
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK
| | - Christian Behrends
- Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University Munich, München, Germany
| | - Simon Wilkinson
- Edinburgh Cancer Research UK Centre, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XR, UK.
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24
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Abstract
Intracellular pathogens often exploit RAB functions to establish a safe haven in which to survive and proliferate. Ehrlichia chaffeensis, an obligatory intracellular bacterium, resides in specialized membrane-bound inclusions that have early endosome-like characteristics, e.g., resident RAB5 GTPase and RAB5 effectors, including VPS34 (the catalytic subunit of class III phosphatidylinositol 3-kinase), but the inclusions lack late endosomal or lysosomal markers. Within inclusions, Ehrlichia obtains host-derived nutrients by inducing RAB5-regulated autophagy using Ehrlichia translocated factor-1 deployed by its type IV secretion system. This manipulation of RAB5 by a bacterial molecule offers a simple strategy for Ehrlichia to avoid destruction in lysosomes and obtain nutrients, membrane components, and a homeostatic intra-host-cell environment in which to grow.
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Affiliation(s)
- Yasuko Rikihisa
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH, USA,CONTACT Yasuko Rikihisa Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, 1925 Coffey Road, Columbus, OH 43210-1093, USA
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25
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Zsiros V, Katz S, Dóczi N, Kiss AL. Autophagy is the key process in the re-establishment of the epitheloid phenotype during mesenchymal-epithelial transition (MET). Exp Cell Res 2017; 352:382-392. [DOI: 10.1016/j.yexcr.2017.02.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 02/14/2017] [Accepted: 02/19/2017] [Indexed: 12/15/2022]
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26
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Tooze SA, Hannan LA, Marks MS, Stevens TH, Schroer TA. Fundamental mechanisms deliver the Nobel Prize to Ohsumi. Traffic 2017; 18:93-95. [PMID: 28097732 DOI: 10.1111/tra.12460] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 11/22/2016] [Accepted: 11/22/2016] [Indexed: 11/29/2022]
Affiliation(s)
- Sharon A Tooze
- Molecular Biology of Autophagy, The Francis Crick Institute, London, UK
| | | | - Michael S Marks
- Michael S. Marks, Departments of Pathology & Laboratory Medicine and Physiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
| | - Tom H Stevens
- Tom H. Stevens, Institute of Molecular Biology, University of Oregon, Eugene, Oregon
| | - Trina A Schroer
- Trina A. Schroer, The Johns Hopkins University, Baltimore, Maryland
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27
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Demirsoy S, Martin S, Maes H, Agostinis P. Adapt, Recycle, and Move on: Proteostasis and Trafficking Mechanisms in Melanoma. Front Oncol 2016; 6:240. [PMID: 27896217 PMCID: PMC5108812 DOI: 10.3389/fonc.2016.00240] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 10/27/2016] [Indexed: 12/21/2022] Open
Abstract
Melanoma has emerged as a paradigm of a highly aggressive and plastic cancer, capable to co-opt the tumor stroma in order to adapt to the hostile microenvironment, suppress immunosurveillance mechanisms, and disseminate. In particular, oncogene- and aneuploidy-driven dysregulations of proteostasis in melanoma cells impose a rewiring of central proteostatic processes, such as the heat shock and unfolded protein responses, autophagy, and the endo-lysosomal system, to avoid proteotoxicity. Research over the past decade has indicated that alterations in key nodes of these proteostasis pathways act in conjunction with crucial oncogenic drivers to increase intrinsic adaptations of melanoma cells against proteotoxic stress, modulate the high metabolic demand of these cancer cells and the interface with other stromal cells, through the heightened release of soluble factors or exosomes. Here, we overview and discuss how key proteostasis pathways and vesicular trafficking mechanisms are turned into vital conduits of melanoma progression, by supporting cancer cell's adaptation to the microenvironment, limiting or modulating the ability to respond to therapy and fueling melanoma dissemination.
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Affiliation(s)
- Seyma Demirsoy
- Laboratory for Cell Death Research and Therapy, Department of Cellular and Molecular Medicine, KU Leuven , Leuven , Belgium
| | - Shaun Martin
- Laboratory for Cellular Transport Systems, Department of Cellular and Molecular Medicine, KU Leuven , Leuven , Belgium
| | - Hannelore Maes
- Laboratory for Cell Death Research and Therapy, Department of Cellular and Molecular Medicine, KU Leuven , Leuven , Belgium
| | - Patrizia Agostinis
- Laboratory for Cell Death Research and Therapy, Department of Cellular and Molecular Medicine, KU Leuven , Leuven , Belgium
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Lin M, Liu H, Xiong Q, Niu H, Cheng Z, Yamamoto A, Rikihisa Y. Ehrlichia secretes Etf-1 to induce autophagy and capture nutrients for its growth through RAB5 and class III phosphatidylinositol 3-kinase. Autophagy 2016; 12:2145-2166. [PMID: 27541856 PMCID: PMC5103349 DOI: 10.1080/15548627.2016.1217369] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Ehrlichia chaffeensis is an obligatory intracellular bacterium that causes a potentially fatal emerging zoonosis, human monocytic ehrlichiosis. E. chaffeensis has a limited capacity for biosynthesis and metabolism and thus depends mostly on host-synthesized nutrients for growth. Although the host cell cytoplasm is rich with these nutrients, as E. chaffeensis is confined within the early endosome-like membrane-bound compartment, only host nutrients that enter the compartment can be used by this bacterium. How this occurs is unknown. We found that ehrlichial replication depended on autophagy induction involving class III phosphatidylinositol 3-kinase (PtdIns3K) activity, BECN1 (Beclin 1), and ATG5 (autophagy-related 5). Ehrlichia acquired host cell preincorporated amino acids in a class III PtdIns3K-dependent manner and ehrlichial growth was enhanced by treatment with rapamycin, an autophagy inducer. Moreover, ATG5 and RAB5A/B/C were routed to ehrlichial inclusions. RAB5A/B/C siRNA knockdown, or overexpression of a RAB5-specific GTPase-activating protein or dominant-negative RAB5A inhibited ehrlichial infection, indicating the critical role of GTP-bound RAB5 during infection. Both native and ectopically expressed ehrlichial type IV secretion effector protein, Etf-1, bound RAB5 and the autophagy-initiating class III PtdIns3K complex, PIK3C3/VPS34, and BECN1, and homed to ehrlichial inclusions. Ectopically expressed Etf-1 activated class III PtdIns3K as in E. chaffeensis infection and induced autophagosome formation, cleared an aggregation-prone mutant huntingtin protein in a class III PtdIns3K-dependent manner, and enhanced ehrlichial proliferation. These data support the notion that E. chaffeensis secretes Etf-1 to induce autophagy to repurpose the host cytoplasm and capture nutrients for its growth through RAB5 and class III PtdIns3K, while avoiding autolysosomal killing.
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Affiliation(s)
- Mingqun Lin
- a Department of Veterinary Biosciences , Ohio State University , Columbus , OH , USA
| | - Hongyan Liu
- a Department of Veterinary Biosciences , Ohio State University , Columbus , OH , USA
| | - Qingming Xiong
- a Department of Veterinary Biosciences , Ohio State University , Columbus , OH , USA
| | - Hua Niu
- a Department of Veterinary Biosciences , Ohio State University , Columbus , OH , USA
| | - Zhihui Cheng
- a Department of Veterinary Biosciences , Ohio State University , Columbus , OH , USA
| | - Akitsugu Yamamoto
- b Faculty of Bioscience , Nagahama Institute of Bioscience and Technology , Nagahama , Shiga , Japan
| | - Yasuko Rikihisa
- a Department of Veterinary Biosciences , Ohio State University , Columbus , OH , USA
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Kruppa AJ, Kendrick-Jones J, Buss F. Myosins, Actin and Autophagy. Traffic 2016; 17:878-90. [PMID: 27146966 PMCID: PMC4957615 DOI: 10.1111/tra.12410] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 05/02/2016] [Accepted: 05/02/2016] [Indexed: 12/20/2022]
Abstract
Myosin motor proteins working together with the actin cytoskeleton drive a wide range of cellular processes. In this review, we focus on their roles in autophagy – the pathway the cell uses to ensure homeostasis by targeting pathogens, misfolded proteins and damaged organelles for degradation. The actin cytoskeleton regulated by a host of nucleating, anchoring and stabilizing proteins provides the filament network for the delivery of essential membrane vesicles from different cellular compartments to the autophagosome. Actin networks have also been implicated in structurally supporting the expanding phagophore, moving autophagosomes and enabling efficient fusion with the lysosome. Only a few myosins have so far been shown to play a role in autophagy. Non‐muscle myosin IIA functions in the early stages delivering membrane for the initial formation of the autophagosome, whereas myosin IC and myosin VI are involved in the final stages providing specific membranes for autophagosome maturation and its fusion with the lysosome.
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Affiliation(s)
- Antonina J Kruppa
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - John Kendrick-Jones
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, CB2 0QH, UK
| | - Folma Buss
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
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Fader CM, Salassa BN, Grosso RA, Vergara AN, Colombo MI. Hemin induces mitophagy in a leukemic erythroblast cell line. Biol Cell 2016; 108:77-95. [PMID: 26773440 DOI: 10.1111/boc.201500058] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Accepted: 01/11/2016] [Indexed: 12/29/2022]
Abstract
BACKGROUND INFORMATION In eukaryotic cells, autophagy is considered a lysosomal catabolic process which participates in the degradation of intracellular components in a vacuolar structure termed autolysosome. This pathway plays a significant role in the erythropoiesis process, contributing to the clearance of some organelles (such as mitochondria) that are not necessary in the mature red blood cells. Nevertheless, the role of autophagy in erythrocyte maturation has not been fully established. RESULTS Here, we have demonstrated that hemin (a physiological erythroid maturation stimulator) is able to induce the expression of critical autophagic genes (i.e., Map1a1b (LC3), Beclin-1 gen, Atg5) in an erythroleukemia cell type. We have also shown that hemin increased the size of autophagic vacuoles which were labelled with LC3 and the degradative lysosomal marker dye quenched-bovine serum albumin. In addition, we have determined by Western blot a rise in the lipidated form of the autophagic protein LC3 (i.e., LC3-II) upon hemin treatment. Moreover, we provide evidence that hemin induces mitochondrial membrane depolarisation and that mitochondria sequestration by autophagy requires the active form of the NIX protein. CONCLUSIONS We have found that the physiological erythroid maturation stimulator hemin is able to induce mitophagy in K562 cells, and that the autophagy adaptor NIX is necessary for mitophagy progression. K562 cells have been used as a relevant model to determine the possible therapeutic role of new differentiating compounds. SIGNIFICANCE It has been proposed that autophagy induction is a feasible new therapeutic key in fighting cancer. Our results suggest that hemin is favoring erythroid maturation by inducing an autophagic response in K562 cells, being a possible therapeutic candidate that may help in the chronic myelogenous leukemia (CML) treatment.
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Affiliation(s)
- Claudio Marcelo Fader
- Facultad de Farmacia y Bioquímica, Universidad Juan Agustín Maza, Mendoza, Argentina.,Instituto de Histología y Embriología (IHEM), Facultad de Ciencias Médicas, Universidad Nacional de Cuyo-CONICET, Mendoza, Argentina
| | - Betiana Nebaí Salassa
- Facultad de Farmacia y Bioquímica, Universidad Juan Agustín Maza, Mendoza, Argentina
| | - Rubén Adrián Grosso
- Instituto de Histología y Embriología (IHEM), Facultad de Ciencias Médicas, Universidad Nacional de Cuyo-CONICET, Mendoza, Argentina
| | | | - María Isabel Colombo
- Facultad de Farmacia y Bioquímica, Universidad Juan Agustín Maza, Mendoza, Argentina.,Instituto de Histología y Embriología (IHEM), Facultad de Ciencias Médicas, Universidad Nacional de Cuyo-CONICET, Mendoza, Argentina
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Müller AJ, Proikas-Cezanne T. Function of human WIPI proteins in autophagosomal rejuvenation of endomembranes? FEBS Lett 2015; 589:1546-51. [PMID: 25980605 DOI: 10.1016/j.febslet.2015.05.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 04/30/2015] [Accepted: 05/05/2015] [Indexed: 12/28/2022]
Abstract
Despite the availability of a large pool of experimental approaches and hypothetical considerations, the hunt for the enigmatic membrane origin of autophagosomes is still on. In mammalian cells proposed scenarios for the formation of the autophagosomal membrane include both de novo assembly, and rearrangements plus maturation of pre-existing membrane sections from the endoplasmic reticulum (ER), plasma membrane, Golgi or mitochondria. Earlier, we identified the human WD-repeat protein interacting with phosphoinositides (WIPI) family and showed that WIPI proteins function as essential phosphatidylinositol 3-phosphate (PtdIns3P) effectors at the nascent autophagosome. Interestingly, WIPI proteins localize to both pre-existing endomembranes and nascent autophagosomes. In this context, and on the basis of historical records on the formation of autophagosomes, we discuss with appropriate modesty an alternative perspective on the membrane origin of autophagosomes.
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Affiliation(s)
- Amelie Johanna Müller
- Autophagy Laboratory, Department of Molecular Biology, Interfaculty Institute of Cell Biology, Eberhard Karls University Tuebingen, Auf der Morgenstelle 15, 72076 Tuebingen, Germany
| | - Tassula Proikas-Cezanne
- Autophagy Laboratory, Department of Molecular Biology, Interfaculty Institute of Cell Biology, Eberhard Karls University Tuebingen, Auf der Morgenstelle 15, 72076 Tuebingen, Germany.
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Brix K, McInnes J, Al-Hashimi A, Rehders M, Tamhane T, Haugen MH. Proteolysis mediated by cysteine cathepsins and legumain-recent advances and cell biological challenges. PROTOPLASMA 2015; 252:755-774. [PMID: 25398648 DOI: 10.1007/s00709-014-0730-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 11/04/2014] [Indexed: 06/04/2023]
Abstract
Proteases play essential roles in protein degradation, protein processing, and extracellular matrix remodeling in all cell types and tissues. They are also involved in protein turnover for maintenance of homeostasis and protein activation or inactivation for cell signaling. Proteases range in function and specificity, with some performing distinct substrate cleavages, while others accomplish proteolysis of a wide range of substrates. As such, different cell types use specialized molecular mechanisms to regulate the localization of proteases and their function within the compartments to which they are destined. Here, we focus on the cysteine family of cathepsin proteases and legumain, which act predominately within the endo-lysosomal pathway. In particular, recent knowledge on cysteine cathepsins and their primary regulator legumain is scrutinized in terms of their trafficking to endo-lysosomal compartments and other less recognized cellular locations. We further explore the mechanisms that regulate these processes and point to pathological cases which arise from detours taken by these proteases. Moreover, the emerging biological roles of specific forms and variants of cysteine cathepsins and legumain are discussed. These may be decisive, pathogenic, or even deadly when localizing to unusual cellular compartments in their enzymatically active form, because they may exert unexpected effects by alternative substrate cleavage. Hence, we propose future perspectives for addressing the actions of cysteine cathepsins and legumain as well as their specific forms and variants. The increasing knowledge in non-canonical aspects of cysteine cathepsin- and legumain-mediated proteolysis may prove valuable for developing new strategies to utilize these versatile proteases in therapeutic approaches.
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Affiliation(s)
- Klaudia Brix
- Research Area HEALTH, Research Center MOLIFE-Molecular Life Sciences, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany,
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Okabayashi S, Shimozawa N, Yasutomi Y, Yanagisawa K, Kimura N. Diabetes mellitus accelerates Aβ pathology in brain accompanied by enhanced GAβ generation in nonhuman primates. PLoS One 2015; 10:e0117362. [PMID: 25675436 PMCID: PMC4326359 DOI: 10.1371/journal.pone.0117362] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Accepted: 12/21/2014] [Indexed: 11/18/2022] Open
Abstract
Growing evidence suggests that diabetes mellitus (DM) is one of the strongest risk factors for developing Alzheimer’s disease (AD). However, it remains unclear why DM accelerates AD pathology. In cynomolgus monkeys older than 25 years, senile plaques (SPs) are spontaneously and consistently observed in their brains, and neurofibrillary tangles are present at 32 years of age and older. In laboratory-housed monkeys, obesity is occasionally observed and frequently leads to development of type 2 DM. In the present study, we performed histopathological and biochemical analyses of brain tissue in cynomolgus monkeys with type 2 DM to clarify the relationship between DM and AD pathology. Here, we provide the evidence that DM accelerates Aβ pathology in vivo in nonhuman primates who had not undergone any genetic manipulation. In DM-affected monkey brains, SPs were observed in frontal and temporal lobe cortices, even in monkeys younger than 20 years. Biochemical analyses of brain revealed that the amount of GM1-ganglioside-bound Aβ (GAβ)—the endogenous seed for Aβ fibril formation in the brain—was clearly elevated in DM-affected monkeys. Furthermore, the level of Rab GTPases was also significantly increased in the brains of adult monkeys with DM, almost to the same levels as in aged monkeys. Intraneuronal accumulation of enlarged endosomes was also observed in DM-affected monkeys, suggesting that exacerbated endocytic disturbance may underlie the acceleration of Aβ pathology due to DM.
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Affiliation(s)
- Sachi Okabayashi
- Tsukuba Primate Research Center, National Institute of Biomedical Innovation, 1–1 Hachimandai, Tsukuba-shi, Ibaraki, 305–0843, Japan
- The Corporation for Production and Research of Laboratory Primates, 1–1 Hachimandai, Tsukuba-shi, Ibaraki, 305–0843, Japan
| | - Nobuhiro Shimozawa
- Tsukuba Primate Research Center, National Institute of Biomedical Innovation, 1–1 Hachimandai, Tsukuba-shi, Ibaraki, 305–0843, Japan
| | - Yasuhiro Yasutomi
- Tsukuba Primate Research Center, National Institute of Biomedical Innovation, 1–1 Hachimandai, Tsukuba-shi, Ibaraki, 305–0843, Japan
| | - Katsuhiko Yanagisawa
- Section of Cell Biology and Pathology, Department of Alzheimer's Disease Research, Center for Development of Advanced Medicine for Dementia, National Center for Geriatrics and Gerontology (NCGG), Gengo 35, Moriika, Obu, Aichi, 474–8511, Japan
| | - Nobuyuki Kimura
- Tsukuba Primate Research Center, National Institute of Biomedical Innovation, 1–1 Hachimandai, Tsukuba-shi, Ibaraki, 305–0843, Japan
- Section of Cell Biology and Pathology, Department of Alzheimer's Disease Research, Center for Development of Advanced Medicine for Dementia, National Center for Geriatrics and Gerontology (NCGG), Gengo 35, Moriika, Obu, Aichi, 474–8511, Japan
- * E-mail:
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Abstract
Autophagy is a lysosome-mediated degradative system that is a highly conserved pathway present in all eukaryotes. In all cells, double-membrane autophagosomes form and engulf cytoplasmic components, delivering them to the lysosome for degradation. Autophagy is essential for cell health and can be activated to function as a recycling pathway in the absence of nutrients or as a quality-control pathway to eliminate damaged organelles or even to eliminate invading pathogens. Autophagy was first identified as a pathway in mammalian cells using morphological techniques, but the Atg (autophagy-related) genes required for autophagy were identified in yeast genetic screens. Despite tremendous advances in elucidating the function of individual Atg proteins, our knowledge of how autophagosomes form and subsequently interact with the endosomal pathway has lagged behind. Recent progress toward understanding where and how both the endocytotic and autophagic pathways overlap is reviewed here.
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Affiliation(s)
- Sharon A Tooze
- London Research Institute, Cancer Research UK, Secretory Pathways Laboratory, London WC2A 3LY, United Kingdom
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Abstract
SIGNIFICANCE Autophagy is a highly conserved eukaryotic cellular recycling process. Through the degradation of cytoplasmic organelles, proteins, and macromolecules, and the recycling of the breakdown products, autophagy plays important roles in cell survival and maintenance. Accordingly, dysfunction of this process contributes to the pathologies of many human diseases. RECENT ADVANCES Extensive research is currently being done to better understand the process of autophagy. In this review, we describe current knowledge of the morphology, molecular mechanism, and regulation of mammalian autophagy. CRITICAL ISSUES At the mechanistic and regulatory levels, there are still many unanswered questions and points of confusion that have yet to be resolved. FUTURE DIRECTIONS Through further research, a more complete and accurate picture of the molecular mechanism and regulation of autophagy will not only strengthen our understanding of this significant cellular process, but will aid in the development of new treatments for human diseases in which autophagy is not functioning properly.
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Affiliation(s)
- Katherine R Parzych
- Department of Molecular, Cellular and Developmental Biology, Life Sciences Institute, University of Michigan , Ann Arbor, Michigan
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Szatmári Z, Kis V, Lippai M, Hegedus K, Faragó T, Lorincz P, Tanaka T, Juhász G, Sass M. Rab11 facilitates cross-talk between autophagy and endosomal pathway through regulation of Hook localization. Mol Biol Cell 2013; 25:522-31. [PMID: 24356450 PMCID: PMC3923643 DOI: 10.1091/mbc.e13-10-0574] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
This study shows that the small GTPase Rab11 is required for both autophagosome and endosome maturation. The authors demonstrate a novel cross-talk mechanism through which autophagy can orchestrate endosomal maturation events to ensure the required endolysosomal input for autophagosome maturation. During autophagy, double-membrane autophagosomes deliver sequestered cytoplasmic content to late endosomes and lysosomes for degradation. The molecular mechanism of autophagosome maturation is still poorly characterized. The small GTPase Rab11 regulates endosomal traffic and is thought to function at the level of recycling endosomes. We show that loss of Rab11 leads to accumulation of autophagosomes and late endosomes in Drosophila melanogaster. Rab11 translocates from recycling endosomes to autophagosomes in response to autophagy induction and physically interacts with Hook, a negative regulator of endosome maturation. Hook anchors endosomes to microtubules, and we show that Rab11 facilitates the fusion of endosomes and autophagosomes by removing Hook from mature late endosomes and inhibiting its homodimerization. Thus induction of autophagy appears to promote autophagic flux by increased convergence with the endosomal pathway.
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Affiliation(s)
- Zsuzsanna Szatmári
- Department of Anatomy, Cell, and Developmental Biology, Eötvös Loránd University, Budapest 1117, Hungary MTA-ELTE Comparative Ethology Research Group, Budapest 1117, Hungary Department of Germline Development, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
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Lee YR, Hu HY, Kuo SH, Lei HY, Lin YS, Yeh TM, Liu CC, Liu HS. Dengue virus infection induces autophagy: an in vivo study. J Biomed Sci 2013; 20:65. [PMID: 24011333 PMCID: PMC3848819 DOI: 10.1186/1423-0127-20-65] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 09/04/2013] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND We and others have reported that autophagy is induced by dengue viruses (DVs) in various cell lines, and that it plays a supportive role in DV replication. This study intended to clarify whether DV infection could induce autophagy in vivo. Furthermore, the effect of DV induced autophagy on viral replication and DV-related pathogenesis was investigated. RESULTS AND CONCLUSIONS The physiopathological parameters were evaluated after DV2 was intracranially injected into 6-day-old ICR suckling mice. Autophagy-related markers were monitored by immunohistochemical/immunofluorescent staining and Western blotting. Double-membrane autophagic vesicles were investigated by transmission-electron-microscopy. DV non-structural-protein-1 (NS1) expression (indicating DV infection) was detected in the cerebrum, medulla and midbrain of the infected mice. In these infected tissues, increased LC3 puncta formation, LC3-II expression, double-membrane autophagosome-like vesicles (autophagosome), amphisome, and decreased p62 accumulation were observed, indicating that DV2 induces the autophagic progression in vivo. Amphisome formation was demonstrated by colocalization of DV2-NS1 protein or LC3 puncta and mannose-6-phosphate receptor (MPR, endosome marker) in DV2-infected brain tissues. We further manipulated DV-induced autophagy by the inducer rapamycin and the inhibitor 3-methyladenine (3MA), which accordingly promoted or suppressed the disease symptoms and virus load in the brain of the infected mice.We demonstrated that DV2 infection of the suckling mice induces autophagy, which plays a promoting role in DV replication and pathogenesis.
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Affiliation(s)
- Ying-Ray Lee
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
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Franz A, Ackermann L, Hoppe T. Create and preserve: proteostasis in development and aging is governed by Cdc48/p97/VCP. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:205-15. [PMID: 23583830 DOI: 10.1016/j.bbamcr.2013.03.031] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 03/08/2013] [Accepted: 03/25/2013] [Indexed: 12/24/2022]
Abstract
The AAA-ATPase Cdc48 (also called p97 or VCP) acts as a key regulator in proteolytic pathways, coordinating recruitment and targeting of substrate proteins to the 26S proteasome or lysosomal degradation. However, in contrast to the well-known function in ubiquitin-dependent cellular processes, the physiological relevance of Cdc48 in organismic development and maintenance of protein homeostasis is less understood. Therefore, studies on multicellular model organisms help to decipher how Cdc48-dependent proteolysis is regulated in time and space to meet developmental requirements. Given the importance of developmental regulation and tissue maintenance, defects in Cdc48 activity have been linked to several human pathologies including protein aggregation diseases. Thus, addressing the underlying disease mechanisms not only contributes to our understanding on the organism-wide function of Cdc48 but also facilitates the design of specific medical therapies. In this review, we will portray the role of Cdc48 in the context of multicellular organisms, pointing out its importance for developmental processes, tissue surveillance, and disease prevention. This article is part of a Special Issue entitled: Ubiquitin-Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf.
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Affiliation(s)
- André Franz
- Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Zülpicher Straße 47a, 50674 Cologne, Germany
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Sirohi K, Chalasani MLS, Sudhakar C, Kumari A, Radha V, Swarup G. M98K-OPTN induces transferrin receptor degradation and RAB12-mediated autophagic death in retinal ganglion cells. Autophagy 2013; 9:510-27. [PMID: 23357852 DOI: 10.4161/auto.23458] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Mutations in the autophagy receptor OPTN/optineurin are associated with the pathogenesis of glaucoma and amyotrophic lateral sclerosis, but the underlying molecular basis is poorly understood. The OPTN variant, M98K has been described as a risk factor for normal tension glaucoma in some ethnic groups. Here, we examined the consequence of the M98K mutation in affecting cellular functions of OPTN. Overexpression of M98K-OPTN induced death of retinal ganglion cells (RGC-5 cell line), but not of other neuronal and non-neuronal cells. Enhanced levels of the autophagy marker, LC3-II, a post-translationally modified form of LC3, in M98K-OPTN-expressing cells and the inability of an LC3-binding-defective M98K variant of OPTN to induce cell death, suggested that autophagy contributes to cell death. Knockdown of Atg5 reduced M98K-induced death of RGC-5 cells, further supporting the involvement of autophagy. Overexpression of M98K-OPTN enhanced autophagosome formation and potentiated the delivery of transferrin receptor to autophagosomes for degradation resulting in reduced cellular transferrin receptor levels. Coexpression of transferrin receptor or supplementation of media with an iron donor reduced M98K-induced cell death. OPTN complexes with RAB12, a GTPase involved in vesicle trafficking, and M98K variant shows enhanced colocalization with RAB12. Knockdown of Rab12 increased transferrin receptor level and reduced M98K-induced cell death. RAB12 is present in autophagosomes and knockdown of Rab12 resulted in reduced formation of autolysosomes during starvation-induced autophagy, implicating a role for RAB12 in autophagy. These results also show that transferrin receptor degradation and autophagy play a crucial role in RGC-5 cell death induced by M98K variant of OPTN.
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Affiliation(s)
- Kapil Sirohi
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, India
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Manil-Segalén M, Lefebvre C, Culetto E, Legouis R. Need an ESCRT for autophagosomal maturation? Commun Integr Biol 2013; 5:566-71. [PMID: 23336026 PMCID: PMC3541323 DOI: 10.4161/cib.21522] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Several reports in fly, nematode and mammalian cells have revealed that the inactivation of endosomal sorting complexes required for transport (ESCRT) blocks the endosomal maturation but also leads to the increased number of autophagosomal structures. In this review we compare these data and conclude that the way ESCRT mutations affect the relationships between autophagosomes and endosomes cannot be generalized but depends on the studied species. We propose that the effect of ESCRT mutations on autophagy is directly dependent of the level of interaction between autophagosomes and endosomes. In particular, the formation of amphisomes during autophagosomal maturation could be the key point to explain the differences observed between species. These observations highlight the importance of multiple model organisms to decipher the complexity of relationships between such dynamic vesicles.
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Affiliation(s)
- Marion Manil-Segalén
- Centre de Génétique Moléculaire; Université Paris-Sud; CNRS UPR3404; Gif-sur-Yvette Cedex, France
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Djeddi A, Michelet X, Culetto E, Alberti A, Barois N, Legouis R. Induction of autophagy in ESCRT mutants is an adaptive response for cell survival in C. elegans. J Cell Sci 2012; 125:685-94. [PMID: 22389403 DOI: 10.1242/jcs.091702] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Endosomes and autophagosomes are two vesicular compartments involved in the degradation and recycling of cellular material. They both undergo a maturation process and finally fuse with the lysosome. In mammals, the convergence between endosomes and autophagosomes is a multistep process that can generate intermediate vesicles named amphisomes. Using knockdowns and mutants of the ESCRT machinery (ESCRT-0-ESCRT-III, ATPase VPS-4) and the autophagic pathway (LGG-1, LGG-2, ATG-7, TOR), we analyzed in vivo the functional links between endosomal maturation and autophagy in Caenorhabditis elegans. We report here that, despite a strong heterogeneity of their developmental phenotypes, all ESCRT mutants present an accumulation of abnormal endosomes and autophagosomes. We show that this accumulation of autophagosomes is secondary to the formation of enlarged endosomes and is due to the induction of the autophagic flux and not a blockage of fusion with lysosomes. We demonstrate that the induction of autophagy is not responsible for the lethality of ESCRT mutants but has a protective role on cellular degradation. We also show that increasing the basal level of autophagy reduces the formation of enlarged endosomes in ESCRT mutants. Together, our data indicate that the induction of autophagy is a protective response against the formation of an abnormal vesicular compartment.
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Affiliation(s)
- Abderazak Djeddi
- Centre de Génétique Moléculaire, UPR 3404, CNRS, Associée à l'université Paris-Sud XI, FRC3115, Avenue de terrasse, Gif-sur-Yvette, 91198, France
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Hu J, Lu JY, Wong AM, Hynan LS, Birnbaum SG, Yilmaz DS, Streit BM, Lenartowicz EM, Thompson TC, Cooper JD, Hofmann SL. Intravenous high-dose enzyme replacement therapy with recombinant palmitoyl-protein thioesterase reduces visceral lysosomal storage and modestly prolongs survival in a preclinical mouse model of infantile neuronal ceroid lipofuscinosis. Mol Genet Metab 2012; 107:213-21. [PMID: 22704978 PMCID: PMC3444630 DOI: 10.1016/j.ymgme.2012.05.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 05/16/2012] [Accepted: 05/16/2012] [Indexed: 11/22/2022]
Abstract
PPT1-related neuronal ceroid lipofuscinosis (NCL) is a lysosomal storage disorder caused by deficiency in a soluble lysosomal enzyme, palmitoyl-protein thioesterase-1 (PPT1). Enzyme replacement therapy (ERT) has not been previously examined in a preclinical animal model. Homozygous PPT1 knockout mice reproduce the known features of the disease, developing signs of motor dysfunction at 5 months of age and death by around 8 months. In the current study, PPT1 knockout mice were treated with purified recombinant PPT1 (0.3 mg, corresponding to 12 mg/kg or 180 U/kg for a 25 g mouse) administered intravenously weekly either 1) from birth; or 2) beginning at 8 weeks of age. The treatment was surprisingly well tolerated and neither anaphylaxis nor antibody formation was observed. In mice treated from birth, survival increased from 236 to 271 days (p<0.001) and the onset of motor deterioration was similarly delayed. In mice treated beginning at 8 weeks, no increases in survival or motor performance were seen. An improvement in neuropathology in the thalamus was seen at 3 months in mice treated from birth, and although this improvement persisted it was attenuated by 7 months. Outside the central nervous system, substantial clearance of autofluorescent storage material in many tissues was observed. Macrophages in spleen, liver and intestine were especially markedly improved, as were acinar cells of the pancreas and tubular cells of the kidney. These findings suggest that ERT may be an option for addressing visceral storage as part of a comprehensive approach to PPT1-related NCL, but more effective delivery methods to target the brain are needed.
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Affiliation(s)
- Jie Hu
- Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, TX 75390-8593, USA
| | - Jui-Yun Lu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-8593, USA
- Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, TX 75390-8593, USA
| | - Andrew M.S. Wong
- Pediatric Storage Disorders Laboratory, Department of Neuroscience, Centre for the Cellular Basis of Behavior, King’s Health Partners Centre for Neurodegeneration, James Black Centre, Institute of Psychiatry, King’s College London, 125 Coldharbour Lane, London SE5 9NU, UK
| | - Linda S. Hynan
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390-8593, USA
- Department of Clinical Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390-8593, USA
| | - Shari G. Birnbaum
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX 75390-8593, USA
| | - Denis S. Yilmaz
- Pediatric Storage Disorders Laboratory, Department of Neuroscience, Centre for the Cellular Basis of Behavior, King’s Health Partners Centre for Neurodegeneration, James Black Centre, Institute of Psychiatry, King’s College London, 125 Coldharbour Lane, London SE5 9NU, UK
| | - Barbara M. Streit
- Pediatric Storage Disorders Laboratory, Department of Neuroscience, Centre for the Cellular Basis of Behavior, King’s Health Partners Centre for Neurodegeneration, James Black Centre, Institute of Psychiatry, King’s College London, 125 Coldharbour Lane, London SE5 9NU, UK
| | - Ewelina M. Lenartowicz
- Pediatric Storage Disorders Laboratory, Department of Neuroscience, Centre for the Cellular Basis of Behavior, King’s Health Partners Centre for Neurodegeneration, James Black Centre, Institute of Psychiatry, King’s College London, 125 Coldharbour Lane, London SE5 9NU, UK
| | - Thomas C.M. Thompson
- Pediatric Storage Disorders Laboratory, Department of Neuroscience, Centre for the Cellular Basis of Behavior, King’s Health Partners Centre for Neurodegeneration, James Black Centre, Institute of Psychiatry, King’s College London, 125 Coldharbour Lane, London SE5 9NU, UK
| | - Jonathan D. Cooper
- Pediatric Storage Disorders Laboratory, Department of Neuroscience, Centre for the Cellular Basis of Behavior, King’s Health Partners Centre for Neurodegeneration, James Black Centre, Institute of Psychiatry, King’s College London, 125 Coldharbour Lane, London SE5 9NU, UK
| | - Sandra L. Hofmann
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-8593, USA
- Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, TX 75390-8593, USA
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Sirois I, Groleau J, Pallet N, Brassard N, Hamelin K, Londono I, Pshezhetsky AV, Bendayan M, Hébert MJ. Caspase activation regulates the extracellular export of autophagic vacuoles. Autophagy 2012; 8:927-37. [PMID: 22692030 DOI: 10.4161/auto.19768] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The endothelium plays a central role in the regulation of vascular wall cellularity and tone by secreting an array of mediators of importance in intercellular communication. Nutrient deprivation of human endothelial cells (EC) evokes unconventional forms of secretion leading to the release of nanovesicles distinct from apoptotic bodies and bearing markers of multivesicular bodies (MVB). Nutrient deficiency is also a potent inducer of autophagy and vesicular transport pathways can be assisted by autophagy. Nutrient deficiency induced a significant and rapid increase in autophagic features, as imaged by electron microscopy and immunoblotting analysis of LC3-II/LC3-I ratios. Increased autophagic flux was confirmed by exposing serum-starved cells to bafilomycin A 1. Induction of autophagy was followed by indices of an apoptotic response, as assessed by microscopy and poly (ADP-ribose) polymerase cleavage in absence of cell membrane permeabilization indicative of necrosis. Pan-caspase inhibition with ZVAD-FMK did not prevent the development of autophagy but negatively impacted autophagic vacuole (AV) maturation. Adopting a multidimensional proteomics approach with validation by immunoblotting, we determined that nutrient-deprived EC released AV components (LC3I, LC3-II, ATG16L1 and LAMP2) whereas pan-caspase inhibition with ZVAD-FMK blocked AV release. Similarly, nutrient deprivation in aortic murine EC isolated from CASP3/caspase 3-deficient mice induced an autophagic response in absence of apoptosis and failed to prompt LC3 release. Collectively, the present results demonstrate the release of autophagic components by nutrient-deprived apoptotic human cells in absence of cell membrane permeabilization. These results also identify caspase-3 as a novel regulator of AV release.
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Affiliation(s)
- Isabelle Sirois
- Research Centre, Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, Canada
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Longatti A, Lamb CA, Razi M, Yoshimura SI, Barr FA, Tooze SA. TBC1D14 regulates autophagosome formation via Rab11- and ULK1-positive recycling endosomes. J Cell Biol 2012; 197:659-75. [PMID: 22613832 PMCID: PMC3365497 DOI: 10.1083/jcb.201111079] [Citation(s) in RCA: 291] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 04/25/2012] [Indexed: 12/13/2022] Open
Abstract
Autophagy is a bulk degradation process characterized by the formation of double membrane vesicles called autophagosomes. The exact molecular mechanism of autophagosome formation and the origin of the autophagosomal membrane remain unclear. We screened 38 human Tre-2/Bub2/Cdc16 domain-containing Rab guanosine triphosphatase-activating proteins (GAPs) and identified 11 negative regulators of starvation-induced autophagy. One of these putative RabGAPs, TBC1D14, colocalizes and interacts with the autophagy kinase ULK1. Overexpressed TBC1D14 tubulates ULK1-positive recycling endosomes (REs), impairing their function and inhibiting autophagosome formation. TBC1D14 binds activated Rab11 but is not a GAP for Rab11, and loss of Rab11 prevents TBC1D14-induced tubulation of REs. Furthermore, Rab11 is required for autophagosome formation. ULK1 and Atg9 are found on Rab11- and transferrin (Tfn) receptor (TfnR)-positive recycling endosomes. Amino acid starvation causes TBC1D14 to relocalize from REs to the Golgi complex, whereas TfnR and Tfn localize to forming autophagosomes, which are ULK1 and LC3 positive. Thus, TBC1D14- and Rab11-dependent vesicular transport from REs contributes to and regulates starvation-induced autophagy.
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Affiliation(s)
- Andrea Longatti
- Cancer Research UK London Research Institute, WC2A 3PF London, England, UK
- Department of Immunology and Microbial Science, Scripps Research Institute, La Jolla, CA 92037
| | | | - Minoo Razi
- Cancer Research UK London Research Institute, WC2A 3PF London, England, UK
| | - Shin-ichiro Yoshimura
- Department of Cell Biology, Graduate School of Medicine, Osaka University, 565-0871 Osaka, Japan
| | - Francis A. Barr
- Department of Biochemistry, University of Oxford, OX1 3QU Oxford, England, UK
| | - Sharon A. Tooze
- Cancer Research UK London Research Institute, WC2A 3PF London, England, UK
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Isaacs AM, Johannsen P, Holm I, Nielsen JE. Frontotemporal dementia caused by CHMP2B mutations. Curr Alzheimer Res 2011; 8:246-51. [PMID: 21222599 PMCID: PMC3182073 DOI: 10.2174/156720511795563764] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 11/30/2010] [Indexed: 01/13/2023]
Abstract
CHMP2B mutations are a rare cause of autosomal dominant frontotemporal dementia (FTD). The best studied example is frontotemporal dementia linked to chromosome 3 (FTD-3) which occurs in a large Danish family, with a further CHMP2B mutation identified in an unrelated Belgian familial FTD patient. These mutations lead to C-terminal truncations of the CHMP2B protein and we will review recent advances in our understanding of the molecular effects of these mutant truncated proteins on vesicular fusion events within the endosome-lysosome and autophagy degradation pathways. We will also review the clinical features of FTD caused by CHMP2B truncation mutations as well as new brain imaging and neuropathological findings. Finally, we collate the current data on CHMP2B missense mutations, which have been reported in FTD and motor neuron disease.
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Affiliation(s)
- A M Isaacs
- Department of Neurodegenerative Disease, VCL Institute of Neurology, Queen Square, London, UK.
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Abstract
Macroautophagy is mediated by a unique organelle, the autophagosome, which encloses a portion of cytoplasm for delivery to the lysosome. Autophagosome formation is dynamically regulated by starvation and other stresses and involves complicated membrane reorganization. Since the discovery of yeast Atg-related proteins, autophagosome formation has been dissected at the molecular level. In this review we describe the molecular mechanism of autophagosome formation with particular focus on the function of Atg proteins and the long-standing discussion regarding the origin of the autophagosome membrane.
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Affiliation(s)
- Noboru Mizushima
- Department of Physiology and Cell Biology, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
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Dall'Armi C, Hurtado-Lorenzo A, Tian H, Morel E, Nezu A, Chan RB, Yu WH, Robinson KS, Yeku O, Small SA, Duff K, Frohman MA, Wenk MR, Yamamoto A, Di Paolo G. The phospholipase D1 pathway modulates macroautophagy. Nat Commun 2011; 1:142. [PMID: 21266992 DOI: 10.1038/ncomms1144] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 11/23/2010] [Indexed: 12/15/2022] Open
Abstract
Although macroautophagy is known to be an essential degradative process whereby autophagosomes mediate the engulfment and delivery of cytoplasmic components into lysosomes, the lipid changes underlying autophagosomal membrane dynamics are undetermined. Here, we show that phospholipase D1 (PLD1), which is primarily associated with the endosomal system, partially relocalizes to the outer membrane of autophagosome-like structures upon nutrient starvation. The localization of PLD1, as well as the starvation-induced increase in PLD activity, are altered by wortmannin, a phosphatidylinositol 3-kinase inhibitor, suggesting PLD1 may act downstream of Vps34. Pharmacological inhibition of PLD and genetic ablation of PLD1 in mouse cells decreased the starvation-induced expansion of LC3-positive compartments, consistent with a role of PLD1 in the regulation of autophagy. Furthermore, inhibition of PLD results in higher levels of Tau and p62 aggregates in organotypic brain slices. Our in vitro and in vivo findings establish a role for PLD1 in autophagy.
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Affiliation(s)
- Claudia Dall'Armi
- Department of Pathology and Cell Biology, Columbia University Medical Center, New York, New York 10032, USA
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The role of ESCRT proteins in fusion events involving lysosomes, endosomes and autophagosomes. Biochem Soc Trans 2011; 38:1469-73. [PMID: 21118109 DOI: 10.1042/bst0381469] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
ESCRT (endosomal sorting complex required for transport) proteins were originally identified for their role in delivering endocytosed proteins to the intraluminal vesicles of late-endosomal structures termed multivesicular bodies. Multivesicular bodies then fuse with lysosomes, leading to degradation of the internalized proteins. Four ESCRT complexes interact to concentrate cargo on the endosomal membrane, induce membrane curvature to form an intraluminal bud and finally pinch off the bud through a membrane-scission event to produce the intraluminal vesicle. Recent work suggests that ESCRT proteins are also required downstream of these events to enable fusion of multivesicular bodies with lysosomes. Autophagy is a related pathway required for the degradation of organelles, long-lived proteins and protein aggregates which also converges on lysosomes. The proteins or organelle to be degraded are encapsulated by an autophagosome that fuses either directly with a lysosome or with an endosome to form an amphisome, which then fuses with a lysosome. A common machinery is beginning to emerge that regulates fusion events in the multivesicular body and autophagy pathways, and we focus in the present paper on the role of ESCRT proteins. These fusion events have been implicated in diseases including frontotemporal dementia, Alzheimer's disease, lysosomal storage disorders, myopathies and bacterial pathogen invasion, and therefore further examination of the mechanisms involved may lead to new insight into disease pathogenesis and treatments.
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Abstract
Autophagy is a major catabolic pathway in eukaryotes, which is required for the lysosomal/vacuolar degradation of cytoplasmic proteins and organelles. Interest in the autophagy pathway has recently gained momentum largely owing to identification of multiple autophagy-related genes and recognition of its involvement in various physiological conditions. Here we review current knowledge of the molecular mechanisms regulating autophagy in mammals and yeast, specifically the biogenesis of autophagosomes and the selectivity of their cargo recruitment. We discuss the different steps of autophagy, from the signal transduction events that regulate it to the completion of this pathway by fusion with the lysosome/vacuole. We also review research on the origin of the autophagic membrane, the molecular mechanism of autophagosome formation, and the roles of two ubiquitin-like protein families and other structural elements that are essential for this process. Finally, we discuss the various modes of autophagy and highlight their functional relevance for selective degradation of specific cargos.
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Affiliation(s)
- Hilla Weidberg
- Department of Biological Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel
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Zoppino FCM, Militello RD, Slavin I, Alvarez C, Colombo MI. Autophagosome formation depends on the small GTPase Rab1 and functional ER exit sites. Traffic 2010; 11:1246-61. [PMID: 20545908 DOI: 10.1111/j.1600-0854.2010.01086.x] [Citation(s) in RCA: 199] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Autophagy is an important cellular degradation pathway present in all eukaryotic cells. Via this pathway, portions of the cytoplasm and/or organelles are sequestered in double-membrane structures called autophagosomes. In spite of the significant advance achieved in autophagy, the long-standing question about the source of the autophagic membrane remains unsolved. We have investigated the role of the secretory pathway in autophagosome biogenesis. Sar1 and Rab1b are monomeric GTPases that control traffic from the endoplasmic reticulum (ER) to the Golgi. We present evidence indicating that the activity of both proteins is required for autophagosome formation. Overexpression of dominant-negative mutants and the use of siRNAs impaired autophagosome generation as determined by LC3 puncta formation and light chain 3 (LC3)-II processing. In addition, our results indicate that the autophagic and secretory pathways intersect at a level preceding the brefeldin A blockage, suggesting that the transport from the cis/medial Golgi is not necessary for autophagosome biogenesis. Our present results highlight the role of transport from the ER in the initial events of the autophagic vacuole development.
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Affiliation(s)
- Felipe Carlos Martín Zoppino
- Instituto de Histología y Embriología (IHEM-CONICET), Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza 5500, Argentina
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