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De Leonibus C, Maddaluno M, Ferriero R, Besio R, Cinque L, Lim PJ, Palma A, De Cegli R, Gagliotta S, Montefusco S, Iavazzo M, Rohrbach M, Giunta C, Polishchuk E, Medina DL, Di Bernardo D, Forlino A, Piccolo P, Settembre C. Sestrin2 drives ER-phagy in response to protein misfolding. Dev Cell 2024; 59:2035-2052.e10. [PMID: 39094564 PMCID: PMC11338521 DOI: 10.1016/j.devcel.2024.07.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 05/01/2024] [Accepted: 07/09/2024] [Indexed: 08/04/2024]
Abstract
Protein biogenesis within the endoplasmic reticulum (ER) is crucial for organismal function. Errors during protein folding necessitate the removal of faulty products. ER-associated protein degradation and ER-phagy target misfolded proteins for proteasomal and lysosomal degradation. The mechanisms initiating ER-phagy in response to ER proteostasis defects are not well understood. By studying mouse primary cells and patient samples as a model of ER storage disorders (ERSDs), we show that accumulation of faulty products within the ER triggers a response involving SESTRIN2, a nutrient sensor controlling mTORC1 signaling. SESTRIN2 induction by XBP1 inhibits mTORC1's phosphorylation of TFEB/TFE3, allowing these transcription factors to enter the nucleus and upregulate the ER-phagy receptor FAM134B along with lysosomal genes. This response promotes ER-phagy of misfolded proteins via FAM134B-Calnexin complex. Pharmacological induction of FAM134B improves clearance of misfolded proteins in ERSDs. Our study identifies the interplay between nutrient signaling and ER quality control, suggesting therapeutic strategies for ERSDs.
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Affiliation(s)
- Chiara De Leonibus
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy; Department of Health Sciences, University of Basilicata, Potenza, Italy
| | - Marianna Maddaluno
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy; Department of Clinical Medicine and Surgery, Federico II University, Naples, Italy
| | - Rosa Ferriero
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Roberta Besio
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Laura Cinque
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy; Department of Clinical Medicine and Surgery, Federico II University, Naples, Italy
| | - Pei Jin Lim
- Division of Metabolism and Children's Research Center, University Hospital of Zurich, Zurich, Switzerland
| | - Alessandro Palma
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Rossella De Cegli
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | | | - Sandro Montefusco
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Maria Iavazzo
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy; Department of Clinical Medicine and Surgery, Federico II University, Naples, Italy
| | - Marianne Rohrbach
- Division of Metabolism and Children's Research Center, University Hospital of Zurich, Zurich, Switzerland
| | - Cecilia Giunta
- Division of Metabolism and Children's Research Center, University Hospital of Zurich, Zurich, Switzerland
| | - Elena Polishchuk
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Diego Louis Medina
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy; Department of Translational Medical Sciences, Federico II University, Naples, Italy
| | - Diego Di Bernardo
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy; Department of Chemical, Materials and Industrial Production Engineering, University of Naples "Federico II", Naples, Italy
| | | | - Pasquale Piccolo
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Carmine Settembre
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy; Department of Clinical Medicine and Surgery, Federico II University, Naples, Italy.
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2
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Holzer E, Martens S, Tulli S. The Role of ATG9 Vesicles in Autophagosome Biogenesis. J Mol Biol 2024; 436:168489. [PMID: 38342428 DOI: 10.1016/j.jmb.2024.168489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 02/02/2024] [Accepted: 02/07/2024] [Indexed: 02/13/2024]
Abstract
Autophagy mediates the degradation and recycling of cellular material in the lysosomal system. Dysfunctional autophagy is associated with a plethora of diseases including uncontrolled infections, cancer and neurodegeneration. In macroautophagy (hereafter autophagy) this material is encapsulated in double membrane vesicles, the autophagosomes, which form upon induction of autophagy. The precursors to autophagosomes, referred to as phagophores, first appear as small flattened membrane cisternae, which gradually enclose the cargo material as they grow. The assembly of phagophores during autophagy initiation has been a major subject of investigation over the past decades. A special focus has been ATG9, the only conserved transmembrane protein among the core machinery. The majority of ATG9 localizes to small Golgi-derived vesicles. Here we review the recent advances and breakthroughs regarding our understanding of how ATG9 and the vesicles it resides in serve to assemble the autophagy machinery and to establish membrane contact sites for autophagosome biogenesis. We also highlight open questions in the field that need to be addressed in the years to come.
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Affiliation(s)
- Elisabeth Holzer
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria; University of Vienna, Max Perutz Labs, Department of Biochemistry and Cell Biology, Vienna, Austria; Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Campus-Vienna-Biocenter 1, Vienna, Austria.
| | - Sascha Martens
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria; University of Vienna, Max Perutz Labs, Department of Biochemistry and Cell Biology, Vienna, Austria.
| | - Susanna Tulli
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria; University of Vienna, Max Perutz Labs, Department of Biochemistry and Cell Biology, Vienna, Austria.
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3
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Jiang T, Ma C, Chen H. Unraveling the ultrastructure and dynamics of autophagic vesicles: Insights from advanced imaging techniques. FASEB Bioadv 2024; 6:189-199. [PMID: 38974114 PMCID: PMC11226998 DOI: 10.1096/fba.2024-00035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 04/18/2024] [Accepted: 04/22/2024] [Indexed: 07/09/2024] Open
Abstract
Autophagy, an intracellular self-degradation process, is governed by a complex interplay of signaling pathways and interactions between proteins and organelles. Its fundamental purpose is to efficiently clear and recycle cellular components that are damaged or redundant. Central to this process are autophagic vesicles, specialized structures that encapsulate targeted cellular elements, playing a pivotal role in autophagy. Despite growing interest in the molecular components of autophagic machinery and their regulatory mechanisms, capturing the detailed ultrastructural dynamics of autophagosome formation continues to present significant challenges. However, recent advancements in microscopy, particularly in electron microscopy, have begun to illuminate the dynamic regulatory processes underpinning autophagy. This review endeavors to provide an exhaustive overview of contemporary research on the ultrastructure of autophagic processes. By synthesizing observations from diverse technological methodologies, this review seeks to deepen our understanding of the genesis of autophagic vesicles, their membrane origins, and the dynamic alterations that transpire during the autophagy process. The aim is to bridge gaps in current knowledge and foster a more comprehensive comprehension of this crucial cellular mechanism.
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Affiliation(s)
- Ting Jiang
- Institute of Reproductive MedicineMedical School of Nantong UniversityNantongPR China
| | - Chaoye Ma
- Institute of Reproductive MedicineMedical School of Nantong UniversityNantongPR China
| | - Hao Chen
- Institute of Reproductive MedicineMedical School of Nantong UniversityNantongPR China
- Guangzhou Women and Children’s Medical Center, GMU‐GIBH Joint School of Life ScienceGuangzhou Medical UniversityGuangzhouChina
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4
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Esrefoglu M. Harnessing autophagy: A potential breakthrough in digestive disease treatment. World J Gastroenterol 2024; 30:3036-3043. [PMID: 38983959 PMCID: PMC11230060 DOI: 10.3748/wjg.v30.i24.3036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Revised: 04/30/2024] [Accepted: 06/04/2024] [Indexed: 06/25/2024] Open
Abstract
Autophagy, a conserved cellular degradation process, is crucial for various cellular processes such as immune responses, inflammation, metabolic and oxidative stress adaptation, cell proliferation, development, and tissue repair and remodeling. Dysregulation of autophagy is suspected in numerous diseases, including cancer, neurodegenerative diseases, digestive disorders, metabolic syndromes, and infectious and inflammatory diseases. If autophagy is disrupted, for example, this can have serious consequences and lead to chronic inflammation and tissue damage, as occurs in diseases such as Chron's disease and ulcerative colitis. On the other hand, the influence of autophagy on the development and progression of cancer is not clear. Autophagy can both suppress and promote the progression and metastasis of cancer at various stages. From inflammatory bowel diseases to gastrointestinal cancer, researchers are discovering the intricate role of autophagy in maintaining gut health and its potential as a therapeutic target. Researchers should carefully consider the nature and progression of diseases such as cancer when trying to determine whether inhibiting or stimulating autophagy is likely to be beneficial. Multidisciplinary approaches that combine cutting-edge research with clinical expertise are key to unlocking the full therapeutic potential of autophagy in digestive diseases.
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Affiliation(s)
- Mukaddes Esrefoglu
- Department of Histology and Embryology, Bezmialem Vakif University Medical Faculty, Istanbul 34093, Türkiye
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5
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Nakamura K, Aoyama-Ishiwatari S, Nagao T, Paaran M, Obara CJ, Sakurai-Saito Y, Johnston J, Du Y, Suga S, Tsuboi M, Nakakido M, Tsumoto K, Kishi Y, Gotoh Y, Kwak C, Rhee HW, Seo JK, Kosako H, Potter C, Carragher B, Lippincott-Schwartz J, Polleux F, Hirabayashi Y. PDZD8-FKBP8 tethering complex at ER-mitochondria contact sites regulates mitochondrial complexity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.08.22.554218. [PMID: 38895210 PMCID: PMC11185567 DOI: 10.1101/2023.08.22.554218] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Mitochondria-ER membrane contact sites (MERCS) represent a fundamental ultrastructural feature underlying unique biochemistry and physiology in eukaryotic cells. The ER protein PDZD8 is required for the formation of MERCS in many cell types, however, its tethering partner on the outer mitochondrial membrane (OMM) is currently unknown. Here we identified the OMM protein FKBP8 as the tethering partner of PDZD8 using a combination of unbiased proximity proteomics, CRISPR-Cas9 endogenous protein tagging, Cryo-Electron Microscopy (Cryo-EM) tomography, and correlative light-EM (CLEM). Single molecule tracking revealed highly dynamic diffusion properties of PDZD8 along the ER membrane with significant pauses and capture at MERCS. Overexpression of FKBP8 was sufficient to narrow the ER-OMM distance, whereas independent versus combined deletions of these two proteins demonstrated their interdependence for MERCS formation. Furthermore, PDZD8 enhances mitochondrial complexity in a FKBP8-dependent manner. Our results identify a novel ER-mitochondria tethering complex that regulates mitochondrial morphology in mammalian cells.
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6
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Nähse V, Stenmark H, Schink KO. Omegasomes control formation, expansion, and closure of autophagosomes. Bioessays 2024; 46:e2400038. [PMID: 38724256 DOI: 10.1002/bies.202400038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Revised: 04/04/2024] [Accepted: 04/05/2024] [Indexed: 05/28/2024]
Abstract
Autophagy, an essential cellular process for maintaining cellular homeostasis and eliminating harmful cytoplasmic objects, involves the de novo formation of double-membraned autophagosomes that engulf and degrade cellular debris, protein aggregates, damaged organelles, and pathogens. Central to this process is the phagophore, which forms from donor membranes rich in lipids synthesized at various cellular sites, including the endoplasmic reticulum (ER), which has emerged as a primary source. The ER-associated omegasomes, characterized by their distinctive omega-shaped structure and accumulation of phosphatidylinositol 3-phosphate (PI3P), play a pivotal role in autophagosome formation. Omegasomes are thought to serve as platforms for phagophore assembly by recruiting essential proteins such as DFCP1/ZFYVE1 and facilitating lipid transfer to expand the phagophore. Despite the critical importance of phagophore biogenesis, many aspects remain poorly understood, particularly the complete range of proteins involved in omegasome dynamics, and the detailed mechanisms of lipid transfer and membrane contact site formation.
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Affiliation(s)
- Viola Nähse
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Harald Stenmark
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Kay O Schink
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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7
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Schmid M, Fischer P, Engl M, Widder J, Kerschbaum-Gruber S, Slade D. The interplay between autophagy and cGAS-STING signaling and its implications for cancer. Front Immunol 2024; 15:1356369. [PMID: 38660307 PMCID: PMC11039819 DOI: 10.3389/fimmu.2024.1356369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 03/26/2024] [Indexed: 04/26/2024] Open
Abstract
Autophagy is an intracellular process that targets various cargos for degradation, including members of the cGAS-STING signaling cascade. cGAS-STING senses cytosolic double-stranded DNA and triggers an innate immune response through type I interferons. Emerging evidence suggests that autophagy plays a crucial role in regulating and fine-tuning cGAS-STING signaling. Reciprocally, cGAS-STING pathway members can actively induce canonical as well as various non-canonical forms of autophagy, establishing a regulatory network of feedback mechanisms that alter both the cGAS-STING and the autophagic pathway. The crosstalk between autophagy and the cGAS-STING pathway impacts a wide variety of cellular processes such as protection against pathogenic infections as well as signaling in neurodegenerative disease, autoinflammatory disease and cancer. Here we provide a comprehensive overview of the mechanisms involved in autophagy and cGAS-STING signaling, with a specific focus on the interactions between the two pathways and their importance for cancer.
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Affiliation(s)
- Maximilian Schmid
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria
- MedAustron Ion Therapy Center, Wiener Neustadt, Austria
- Department of Medical Biochemistry, Medical University of Vienna, Max Perutz Labs, Vienna Biocenter, Vienna, Austria
| | - Patrick Fischer
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria
- MedAustron Ion Therapy Center, Wiener Neustadt, Austria
- Department of Medical Biochemistry, Medical University of Vienna, Max Perutz Labs, Vienna Biocenter, Vienna, Austria
| | - Magdalena Engl
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria
- Department of Medical Biochemistry, Medical University of Vienna, Max Perutz Labs, Vienna Biocenter, Vienna, Austria
- Vienna Biocenter PhD Program, a Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Joachim Widder
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria
| | - Sylvia Kerschbaum-Gruber
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria
- MedAustron Ion Therapy Center, Wiener Neustadt, Austria
| | - Dea Slade
- Department of Radiation Oncology, Medical University of Vienna, Vienna, Austria
- Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria
- MedAustron Ion Therapy Center, Wiener Neustadt, Austria
- Department of Medical Biochemistry, Medical University of Vienna, Max Perutz Labs, Vienna Biocenter, Vienna, Austria
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8
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Yang Q, Miki T. Characterization of peptide-fused protein assemblies in living cells. Methods Enzymol 2024; 697:293-319. [PMID: 38816127 DOI: 10.1016/bs.mie.2024.01.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2024]
Abstract
Assembly of de novo peptides designed from scratch is in a semi-rational manner and creates artificial supramolecular structures with unique properties. Considering that the functions of various proteins in living cells are highly regulated by their assemblies, building artificial assemblies within cells holds the potential to simulate the functions of natural protein assemblies and engineer cellular activities for controlled manipulation. How can we evaluate the self-assembly of designed peptides in cells? The most effective approach involves the genetic fusion of fluorescent proteins (FPs). Expressing a self-assembling peptide fused with an FP within cells allows for evaluating assemblies through fluorescence signal. When µm-scale assemblies such as condensates are formed, the peptide assemblies can be directly observed by imaging. For sub-µm-scale assemblies, fluorescence correlation spectroscopy analysis is more practical. Additionally, the fluorescence resonance energy transfer (FRET) signal between FPs is valuable evidence of proximity. The decrease in fluorescence anisotropy associated with homo-FRET reveals the properties of self-assembly. Furthermore, by combining two FPs, one acting as a donor and the other as an acceptor, the heteromeric interaction between two different components can be studied through the FRET signal. In this chapter, we provide detailed protocols, from designing and constructing plasmid DNA expressing the peptide-fused protein to analysis of self-assembly in living cells.
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Affiliation(s)
- Qinxuan Yang
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Takayuki Miki
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan.
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9
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Shatz O, Fraiberg M, Isola D, Das S, Gogoi O, Polyansky A, Shimoni E, Dadosh T, Dezorella N, Wolf SG, Elazar Z. Rim aperture of yeast autophagic membranes balances cargo inclusion with vesicle maturation. Dev Cell 2024; 59:911-923.e4. [PMID: 38447569 DOI: 10.1016/j.devcel.2024.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 11/28/2023] [Accepted: 02/06/2024] [Indexed: 03/08/2024]
Abstract
Autophagy eliminates cytoplasmic material by engulfment in membranous vesicles targeted for lysosome degradation. Nonselective autophagy coordinates sequestration of bulk cargo with the growth of the isolation membrane (IM) in a yet-unknown manner. Here, we show that in the budding yeast Saccharomyces cerevisiae, IMs expand while maintaining a rim sufficiently wide for sequestration of large cargo but tight enough to mature in due time. An obligate complex of Atg24/Snx4 with Atg20 or Snx41 assembles locally at the rim in a spatially extended manner that specifically depends on autophagic PI(3)P. This assembly stabilizes the open rim to promote autophagic sequestration of large cargo in correlation with vesicle expansion. Moreover, constriction of the rim by the PI(3)P-dependent Atg2-Atg18 complex and clearance of PI(3)P by Ymr1 antagonize rim opening to promote autophagic maturation and consumption of small cargo. Tight regulation of membrane rim aperture by PI(3)P thus couples the mechanism and physiology of nonselective autophagy.
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Affiliation(s)
- Oren Shatz
- Departments of Biomolecular Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Milana Fraiberg
- Departments of Biomolecular Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Damilola Isola
- Departments of Biomolecular Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Shubhankar Das
- Departments of Biomolecular Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Olee Gogoi
- Departments of Biomolecular Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Alexandra Polyansky
- Departments of Biomolecular Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Eyal Shimoni
- Chemical Research Support, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Tali Dadosh
- Chemical Research Support, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Nili Dezorella
- Chemical Research Support, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Sharon G Wolf
- Chemical Research Support, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Zvulun Elazar
- Departments of Biomolecular Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel.
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10
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Sakai Y, Takahashi S, Koyama-Honda I, Saito C, Mizushima N. Experimental determination and mathematical modeling of standard shapes of forming autophagosomes. Nat Commun 2024; 15:91. [PMID: 38167876 PMCID: PMC10762205 DOI: 10.1038/s41467-023-44442-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 12/12/2023] [Indexed: 01/05/2024] Open
Abstract
The formation of autophagosomes involves dynamic morphological changes of a phagophore from a flat membrane cisterna into a cup-shaped intermediate and a spherical autophagosome. However, the physical mechanism behind these morphological changes remains elusive. Here, we determine the average shapes of phagophores by statistically investigating three-dimensional electron micrographs of more than 100 phagophores. The results show that the cup-shaped structures adopt a characteristic morphology; they are longitudinally elongated, and the rim is catenoidal with an outwardly recurved shape. To understand these characteristic shapes, we establish a theoretical model of the shape of entire phagophores. The model quantitatively reproduces the average morphology and reveals that the characteristic shape of phagophores is primarily determined by the relative size of the open rim to the total surface area. These results suggest that the seemingly complex morphological changes during autophagosome formation follow a stable path determined by elastic bending energy minimization.
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Affiliation(s)
- Yuji Sakai
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan.
- Department of Biosystems Science, Institute for Life and Medical Sciences, Kyoto University, Sakyo-ku, Kyoto, 606-8507, Japan.
- Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS) Program, RIKEN, Wako, Saitama, 351-0198, Japan.
| | - Satoru Takahashi
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
- Department of Neurosurgery, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Ikuko Koyama-Honda
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Chieko Saito
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Noboru Mizushima
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan.
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11
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Shimizu T, Tamura N, Nishimura T, Saito C, Yamamoto H, Mizushima N. Comprehensive analysis of autophagic functions of WIPI family proteins and their implications for the pathogenesis of β-propeller associated neurodegeneration. Hum Mol Genet 2023; 32:2623-2637. [PMID: 37364041 PMCID: PMC10407718 DOI: 10.1093/hmg/ddad096] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 05/15/2023] [Accepted: 06/13/2023] [Indexed: 06/28/2023] Open
Abstract
β-propellers that bind polyphosphoinositides (PROPPINs) are an autophagy-related protein family conserved throughout eukaryotes. The PROPPIN family includes Atg18, Atg21 and Hsv2 in yeast and WD-repeat protein interacting with phosphoinositides (WIPI)1-4 in mammals. Mutations in the WIPI genes are associated with human neuronal diseases, including β-propeller associated neurodegeneration (BPAN) caused by mutations in WDR45 (encoding WIPI4). In contrast to yeast PROPPINs, the functions of mammalian WIPI1-WIPI4 have not been systematically investigated. Although the involvement of WIPI2 in autophagy has been clearly shown, the functions of WIPI1, WIPI3 and WIPI4 in autophagy remain poorly understood. In this study, we comprehensively analyzed the roles of WIPI proteins by using WIPI-knockout (single, double and quadruple knockout) HEK293T cells and recently developed HaloTag-based reporters, which enable us to monitor autophagic flux sensitively and quantitatively. We found that WIPI2 was nearly essential for autophagy. Autophagic flux was unaffected or only slightly reduced by single deletion of WIPI3 (encoded by WDR45B) or WIPI4 but was profoundly reduced by double deletion of WIPI3 and WIPI4. Furthermore, we revealed variable effects of BPAN-related missense mutations on the autophagic activity of WIPI4. BPAN is characterized by neurodevelopmental and neurodegenerative abnormalities, and we found a possible association between the magnitude of the defect of the autophagic activity of WIPI4 mutants and the severity of neurodevelopmental symptoms. However, some of the BPAN-related missense mutations, which produce neurodegenerative signs, showed almost normal autophagic activity, suggesting that non-autophagic functions of WIPI4 may be related to neurodegeneration in BPAN.
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Affiliation(s)
- Takahiro Shimizu
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan
- Department of Neurology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan
| | - Norito Tamura
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan
| | - Taki Nishimura
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan
- PRESTO, Japan Science and Technology Agency, Tokyo 102-0076, Japan
| | - Chieko Saito
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan
| | - Hayashi Yamamoto
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan
- Department of Molecular Oncology, Nippon Medical School, Institute for Advanced Medical Sciences, Tokyo 113-8602, Japan
| | - Noboru Mizushima
- Department of Biochemistry and Molecular Biology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan
- International Research Center for Neurointelligence (WPI-IRCN), UTIAS, The University of Tokyo, Tokyo 113-8655, Japan
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12
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Zhen Y, Stenmark H. Autophagosome Biogenesis. Cells 2023; 12:cells12040668. [PMID: 36831335 PMCID: PMC9954227 DOI: 10.3390/cells12040668] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 02/10/2023] [Accepted: 02/16/2023] [Indexed: 02/22/2023] Open
Abstract
Autophagy-the lysosomal degradation of cytoplasm-plays a central role in cellular homeostasis and protects cells from potentially harmful agents that may accumulate in the cytoplasm, including pathogens, protein aggregates, and dysfunctional organelles. This process is initiated by the formation of a phagophore membrane, which wraps around a portion of cytoplasm or cargo and closes to form a double-membrane autophagosome. Upon the fusion of the autophagosome with a lysosome, the sequestered material is degraded by lysosomal hydrolases in the resulting autolysosome. Several alternative membrane sources of autophagosomes have been proposed, including the plasma membrane, endosomes, mitochondria, endoplasmic reticulum, lipid droplets, hybrid organelles, and de novo synthesis. Here, we review recent progress in our understanding of how the autophagosome is formed and highlight the proposed role of vesicles that contain the lipid scramblase ATG9 as potential seeds for phagophore biogenesis. We also discuss how the phagophore is sealed by the action of the endosomal sorting complex required for transport (ESCRT) proteins.
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Affiliation(s)
- Yan Zhen
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Montebello, N-0379 Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, N-0379 Oslo, Norway
- Correspondence: (Y.Z.); (H.S.); Tel.: +47-22781911 (Y.Z.); +47-22781818 (H.S.)
| | - Harald Stenmark
- Centre for Cancer Cell Reprogramming, Faculty of Medicine, University of Oslo, Montebello, N-0379 Oslo, Norway
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, N-0379 Oslo, Norway
- Correspondence: (Y.Z.); (H.S.); Tel.: +47-22781911 (Y.Z.); +47-22781818 (H.S.)
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Capitanio C, Bieber A, Wilfling F. How Membrane Contact Sites Shape the Phagophore. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2023; 6:25152564231162495. [PMID: 37366413 PMCID: PMC10243513 DOI: 10.1177/25152564231162495] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 02/15/2023] [Accepted: 02/18/2023] [Indexed: 06/28/2023]
Abstract
During macroautophagy, phagophores establish multiple membrane contact sites (MCSs) with other organelles that are pivotal for proper phagophore assembly and growth. In S. cerevisiae, phagophore contacts have been observed with the vacuole, the ER, and lipid droplets. In situ imaging studies have greatly advanced our understanding of the structure and function of these sites. Here, we discuss how in situ structural methods like cryo-CLEM can give unprecedented insights into MCSs, and how they help to elucidate the structural arrangements of MCSs within cells. We further summarize the current knowledge of the contact sites in autophagy, focusing on autophagosome biogenesis in the model organism S. cerevisiae.
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Affiliation(s)
- Cristina Capitanio
- Department of Molecular Machines and
Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
- Aligning Science Across Parkinson's (ASAP)
Collaborative Research Network, Chevy Chase, MD, USA
| | - Anna Bieber
- Department of Molecular Machines and
Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
- Aligning Science Across Parkinson's (ASAP)
Collaborative Research Network, Chevy Chase, MD, USA
| | - Florian Wilfling
- Mechanisms of Cellular Quality Control, Max Planck Institute of Biophysics, Frankfurt a. M., Germany
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