1
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Li H, Song JZ, He CW, Xie MX, Zhang ZT, Zhou Y, Li XJ, Cui L, Zhu J, Gong Q, Xie Z. Temporal dissection of the roles of Atg4 and ESCRT in autophagosome formation in yeast. Cell Death Differ 2024:10.1038/s41418-024-01438-8. [PMID: 39715823 DOI: 10.1038/s41418-024-01438-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2024] [Revised: 12/07/2024] [Accepted: 12/16/2024] [Indexed: 12/25/2024] Open
Abstract
Autophagosomes are formed by the enlargement and sealing of phagophores. This is accompanied by the recruitment and release of autophagy-related (Atg) proteins that function therein. Presently, the relationship among factors that act after the initial emergence of the phagophore is unclear. The endosomal sorting complexes required for transport (ESCRT) machinery and Atg4 are known to function in phagophore sealing and Atg8 release, respectively. Here we show that biochemically, both Atg4 and ESCRT promoted phagophore sealing. Intriguingly, Atg4-mediated release of Atg8 from the phagophore promoted phagophore sealing even in the absence of ESCRT. This sealing activity could be reconstituted in vitro using cell lysate and purified Atg4. To elucidate the temporal relationship between Atg4 and ESCRT, we charted a timeline of the autophagosome formation cycle based on the trafficking of Atg proteins and mapped the actions of Atg4 and ESCRT to specific stages. The temporal impact of Atg4-mediated release of Atg8 from phagophore was mapped to the stage after the assembly of phagophore assembly site (PAS) scaffold and phosphatidylinositol-3-kinase (PtdIns-3-K) complex; its retardation only extended the duration of Atg8 release stage, leading to delayed phagophore sealing and accumulation of multiple phagophores. The impacts of ESCRT were mapped to two stages. In addition to promoting phagophore sealing, it also dictates whether PtdIns-3-K recruitment can occur by controlling Atg9 trafficking, thereby determining the incidence of autophagosome formation. Accordingly, ESCRT deficiency led to a combination of reduced autophagosome frequency and extended autophagosome formation duration, manifesting as reduced autophagic flux but normal apparent Atg8 puncta number. Our study thus identifies Atg4-mediated Atg8 shedding as a novel membrane scission mechanism and reveals a new early-stage role for ESCRT in autophagy.
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Affiliation(s)
- Hui Li
- Shanghai Sixth People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, PR China
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - Jing-Zhen Song
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - Cheng-Wen He
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - Meng-Xi Xie
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - Zheng-Tan Zhang
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - You Zhou
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - Xin-Jing Li
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - Li Cui
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - Jing Zhu
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - Qingqiu Gong
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China
| | - Zhiping Xie
- State Key Laboratory of Microbial Metabolism & Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China.
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2
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Mathur A, Ritu, Chandra P, Das A. Autophagy: a necessary evil in cancer and inflammation. 3 Biotech 2024; 14:87. [PMID: 38390576 PMCID: PMC10879063 DOI: 10.1007/s13205-023-03864-w] [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: 07/20/2023] [Accepted: 11/21/2023] [Indexed: 02/24/2024] Open
Abstract
Autophagy, a highly regulated cellular process, assumes a dual role in the context of cancer. On the one hand, it functions as a crucial homeostatic pathway, responsible for degrading malfunctioning molecules and organelles, thereby maintaining cellular health. On the other hand, its involvement in cancer development and regression is multifaceted, contingent upon a myriad of factors. This review meticulously examines the intricacies of autophagy, from its molecular machinery orchestrated by Autophagy-Related Genes (ATG) initially discovered in yeast to the various modes of autophagy operative within cells. Beyond its foundational role in cellular maintenance, autophagy reveals context-specific functions in processes like angiogenesis and inflammation. Our analysis delves into how autophagy-related factors directly impact inflammation, underscoring their profound implications for cancer dynamics. Additionally, we extend our inquiry to explore autophagy's associations with cardiovascular conditions, neurodegenerative disorders, and autoimmune diseases, illuminating the broader medical relevance of this process. Furthermore, this review elucidates how autophagy contributes to sustaining hallmark cancer features, including stem cell maintenance, proliferation, angiogenesis, metastasis, and metabolic reprogramming. Autophagy emerges as a pivotal process that necessitates careful consideration in cancer treatment strategies. To this end, we investigate innovative approaches, ranging from enzyme-based therapies to MTOR inhibitors, lysosomal blockers, and nanoparticle-enabled interventions, all aimed at optimizing cancer treatment outcomes by targeting autophagy pathways. In summary, this comprehensive review provides a nuanced perspective on the intricate and context-dependent role of autophagy in cancer biology. Our exploration not only deepens our understanding of this fundamental process but also highlights its potential as a therapeutic target. By unraveling the complex interplay between autophagy and cancer, we pave the way for more precise and effective cancer treatments, promising better outcomes for patients.
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Affiliation(s)
- Amit Mathur
- Department of Biotechnology, Delhi Technological University, Main Bawana Road, Delhi, 110042 India
| | - Ritu
- Department of Biotechnology, Delhi Technological University, Main Bawana Road, Delhi, 110042 India
| | - Prakash Chandra
- Department of Biotechnology, Delhi Technological University, Main Bawana Road, Delhi, 110042 India
| | - Asmita Das
- Department of Biotechnology, Delhi Technological University, Main Bawana Road, Delhi, 110042 India
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3
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Sakai Y, Oku M. ATG and ESCRT control multiple modes of microautophagy. FEBS Lett 2024; 598:48-58. [PMID: 37857501 DOI: 10.1002/1873-3468.14760] [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: 07/20/2023] [Revised: 08/30/2023] [Accepted: 09/01/2023] [Indexed: 10/21/2023]
Abstract
The discovery of microautophagy, the direct engulfment of cytoplasmic material by the lysosome, dates back to 1966 in a morphological study of mammalian cells by Christian de Duve. Since then, studies on microautophagy have shifted toward the elucidation of the physiological significance of the process. However, in contrast to macroautophagy, studies on the molecular mechanisms of microautophagy have been limited. Only recent studies revealed that ATG proteins involved in macroautophagy are also operative in several types of microautophagy and that ESCRT proteins, responsible for the multivesicular body pathway, play a central role in most microautophagy processes. In this review, we summarize our current knowledge on the function of ATG and ESCRT proteins in microautophagy.
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Affiliation(s)
- Yasuyoshi Sakai
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan
| | - Masahide Oku
- Department of Bioscience and Biotechnology, Faculty of Bioenvironmental Sciences, Kyoto University of Advanced Science, Kameoka, Japan
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4
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Kimura Y, Tsuji T, Shimizu Y, Watanabe Y, Kimura M, Fujimoto T, Higuchi M. Physicochemical properties of the vacuolar membrane and cellular factors determine formation of vacuolar invaginations. Sci Rep 2023; 13:16187. [PMID: 37759072 PMCID: PMC10533490 DOI: 10.1038/s41598-023-43232-5] [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: 02/26/2023] [Accepted: 09/21/2023] [Indexed: 09/29/2023] Open
Abstract
Vacuoles change their morphology in response to stress. In yeast exposed to chronically high temperatures, vacuolar membranes get deformed and invaginations are formed. We show that phase-separation of vacuolar membrane occurred after heat stress leading to the formation of the invagination. In addition, Hfl1, a vacuolar membrane-localized Atg8-binding protein, was found to suppress the excess vacuolar invaginations after heat stress. At that time, Hfl1 formed foci at the neck of the invaginations in wild-type cells, whereas it was efficiently degraded in the vacuole in the atg8Δ mutant. Genetic analysis showed that the endosomal sorting complex required for transport machinery was necessary to form the invaginations irrespective of Atg8 or Hfl1. In contrast, a combined mutation with the vacuole BAR domain protein Ivy1 led to vacuoles in hfl1Δivy1Δ and atg8Δivy1Δ mutants having constitutively invaginated structures; moreover, these mutants showed stress-sensitive phenotypes. Our findings suggest that vacuolar invaginations result from the combination of changes in the physiochemical properties of the vacuolar membrane and other cellular factors.
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Affiliation(s)
- Yoko Kimura
- Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka, 422-8529, Japan.
- Department of Agriculture, Shizuoka University, Shizuoka, 422-8529, Japan.
| | - Takuma Tsuji
- Laboratory of Molecular Cell Biology, Research Institute for Diseases of Old Age, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Yosuke Shimizu
- Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka, 422-8529, Japan
| | - Yuki Watanabe
- Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka, 422-8529, Japan
| | - Masafumi Kimura
- Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka, 422-8529, Japan
| | - Toyoshi Fujimoto
- Laboratory of Molecular Cell Biology, Research Institute for Diseases of Old Age, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Miyuki Higuchi
- Department of Agriculture, Shizuoka University, Shizuoka, 422-8529, Japan
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5
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Mutvei AP, Nagiec MJ, Blenis J. Balancing lysosome abundance in health and disease. Nat Cell Biol 2023; 25:1254-1264. [PMID: 37580388 DOI: 10.1038/s41556-023-01197-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Accepted: 06/28/2023] [Indexed: 08/16/2023]
Abstract
Lysosomes are catabolic organelles that govern numerous cellular processes, including macromolecule degradation, nutrient signalling and ion homeostasis. Aberrant changes in lysosome abundance are implicated in human diseases. Here we outline the mechanisms of lysosome biogenesis and turnover, and discuss how changes in the lysosome pool impact physiological and pathophysiological processes.
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Affiliation(s)
- Anders P Mutvei
- Department of Laboratory Medicine, Division of Pathology, Karolinska Institutet, Huddinge, Sweden.
- Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden.
| | - Michal J Nagiec
- Meyer Cancer Center and Department of Pharmacology, Weill Cornell Medical College, New York, NY, USA
| | - John Blenis
- Meyer Cancer Center and Department of Pharmacology, Weill Cornell Medical College, New York, NY, USA.
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6
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Wang L, Klionsky DJ, Shen HM. The emerging mechanisms and functions of microautophagy. Nat Rev Mol Cell Biol 2023; 24:186-203. [PMID: 36097284 DOI: 10.1038/s41580-022-00529-z] [Citation(s) in RCA: 159] [Impact Index Per Article: 159.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/02/2022] [Indexed: 02/08/2023]
Abstract
'Autophagy' refers to an evolutionarily conserved process through which cellular contents, such as damaged organelles and protein aggregates, are delivered to lysosomes for degradation. Different forms of autophagy have been described on the basis of the nature of the cargoes and the means used to deliver them to lysosomes. At present, the prevailing categories of autophagy in mammalian cells are macroautophagy, microautophagy and chaperone-mediated autophagy. The molecular mechanisms and biological functions of macroautophagy and chaperone-mediated autophagy have been extensively studied, but microautophagy has received much less attention. In recent years, there has been a growth in research on microautophagy, first in yeast and then in mammalian cells. Here we review this form of autophagy, focusing on selective forms of microautophagy. We also discuss the upstream regulatory mechanisms, the crosstalk between macroautophagy and microautophagy, and the functional implications of microautophagy in diseases such as cancer and neurodegenerative disorders in humans. Future research into microautophagy will provide opportunities to develop novel interventional strategies for autophagy- and lysosome-related diseases.
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Affiliation(s)
- Liming Wang
- School of Biomedical Sciences, Hunan University, Changsha, China
| | - Daniel J Klionsky
- Life Sciences Institute and Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
| | - Han-Ming Shen
- Faculty of Health Sciences, Ministry of Education Frontiers Science Center for Precision Oncology, University of Macau, Macau, China. .,Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
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7
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Chen W, Chen Y, Liu Y, Wang X. Autophagy in muscle regeneration: potential therapies for myopathies. J Cachexia Sarcopenia Muscle 2022; 13:1673-1685. [PMID: 35434959 PMCID: PMC9178153 DOI: 10.1002/jcsm.13000] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 03/28/2022] [Accepted: 03/30/2022] [Indexed: 12/19/2022] Open
Abstract
Autophagy classically functions as a physiological process to degrade cytoplasmic components, protein aggregates, and/or organelles, as a mechanism for nutrient breakdown, and as a regulator of cellular architecture. Its biological functions include metabolic stress adaptation, stem cell differentiation, immunomodulation and diseases regulation, and so on. Current researches have proved that autophagy dysfunction may contribute to the pathogenesis of some myopathies through impairment of myofibres regeneration. Studies of autophagy inhibition also indicate the importance of autophagy in muscle regeneration, while activation of autophagy can restore muscle function in some myopathies. In this review, we aim to report the mechanisms of action of autophagy on muscle regeneration to provide relevant references for the treatment of regenerating defective myopathies by regulating autophagy. Results have shown that one key mechanism of autophagy regulating the muscle regeneration is to affect the differentiation fate of muscle stem cells (MuSCs), including quiescence maintenance, activation and differentiation. The roles of autophagy (organelle/protein degradation, energy facilitation, and/or other) vary at different myogenic stages of the repair process. When the muscle is in homeostasis, basal autophagy can maintain the quiescence state and stemness of MuSCs by renewing organelle and protein. After injury, the increased autophagy flux contributes to meet biological energy demand of MuSCs during activation and proliferation. By mitochondrial remodelling, autophagy during differentiation can promote the metabolic transformation and balance mitochondrial-mediated apoptosis signals in myoblasts. Autophagy in mature myofibres is also essential for the degradation of necrotic myofibres, and may affect the dynamics of MuSCs by affecting the secretion spectrum of myofibres or the recruitment of supporting cells. Except for myogenic cells, autophagy also plays an important role in regulating the function of non-myogenic cells in the muscle microenvironment, which is also essential for successful muscle recovery. Autophagy can regulate the immune microenvironment during muscle regeneration through the recruitment and polarization of macrophages, while autophagy in endothelial cells can regulate muscle regeneration in an angiogenic or angiogenesis-independent manner. Drug or nutrition targeted autophagy has been preliminarily proved to restore muscle function in myopathies by promoting muscle regeneration, and further understanding the role and mechanism of autophagy in various cell types during muscle regeneration will enable more effective combinatorial therapeutic strategies.
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Affiliation(s)
- Wei Chen
- College of Animal Sciences, Zhejiang University, Hangzhou, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, China
| | - Yushi Chen
- College of Animal Sciences, Zhejiang University, Hangzhou, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, China
| | - Yuxi Liu
- College of Animal Sciences, Zhejiang University, Hangzhou, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, China
| | - Xinxia Wang
- College of Animal Sciences, Zhejiang University, Hangzhou, China.,Key Laboratory of Molecular Animal Nutrition (Zhejiang University), Ministry of Education, Hangzhou, China.,Key Laboratory of Animal Nutrition and Feed Science (Eastern of China), Ministry of Agriculture and Rural Affairs, Hangzhou, China.,Key Laboratory of Animal Feed and Nutrition of Zhejiang Province, Hangzhou, China
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8
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Liu R, Zhang R, Yang Y, Liu X, Gong Q. Monitoring Autophagy in Rice With GFP-ATG8 Marker Lines. FRONTIERS IN PLANT SCIENCE 2022; 13:866367. [PMID: 35548298 PMCID: PMC9083259 DOI: 10.3389/fpls.2022.866367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 03/28/2022] [Indexed: 06/15/2023]
Abstract
Autophagy is a conserved intracellular trafficking pathway for bulk degradation and recycling of cellular components in eukaryotes. The hallmark of autophagy is the formation of double-membraned vesicles termed autophagosomes, which selectively or non-selectively pack up various macromolecules and organelles and deliver these cargoes into the vacuole/lysosome. Like all other membrane trafficking pathways, the observation of autophagy is largely dependent on marker lines. ATG8/LC3 is the only autophagy-related (ATG) protein that, through a covalent bond to phosphatidylethanolamine (PE), associates tightly with the isolation membrane/pre-autophagosomal structure (PAS), the growing phagophore, the mature autophagosome, and the autophagic bodies. Therefore, fluorescent protein (FP)-tagged ATG8 had been widely used for monitoring autophagosome formation and autophagic flux. In rice (Oryza sativa), FP-OsATG8 driven by Cauliflower mosaic virus (CaMV) 35S promoter had been used for imaging autophagosome and autophagic bodies. Here, we constructed three vectors carrying GFP-OsATG8a, driven by 35S, ubiquitin, and the endogenous ATG8a promoter, individually. Then, we compared them for their suitability in monitoring autophagy, by observing GFP-ATG8a puncta formation in transiently transformed rice protoplasts, and by tracking the autophagic flux with GFP-ATG8 cleavage assay in rice stable transgenic lines. GFP-Trap immunoprecipitation and mass spectrometry were also performed with the three marker lines to show that they can be used reliably for proteomic studies. We found out that the ubiquitin promoter is the best for protoplast imaging. Transgenic rice seedlings of the three marker lines showed comparable performance in autophagic flux measurement using the GFP-ATG8 cleavage assay. Surprisingly, the levels of GFP-ATG8a transcripts and protein contents were similar in all marker lines, indicating post-transcriptional regulation of the transgene expression by a yet unknown mechanism. These marker lines can serve as useful tools for autophagy studies in rice.
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Affiliation(s)
- Rui Liu
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Rongxue Zhang
- Tianjin Key Laboratory of Crop Genetics and Breeding, Tianjin Agricultural University, Tianjin, China
| | - Yi Yang
- College of Life Sciences, Nankai University, Tianjin, China
| | - Xuejun Liu
- Tianjin Key Laboratory of Crop Genetics and Breeding, Tianjin Agricultural University, Tianjin, China
| | - Qingqiu Gong
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
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9
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Duarte PV, Hardenberg R, Mari M, Walter S, Reggiori F, Fröhlich F, Montoro AG, Ungermann C. The yeast LYST homolog Bph1 is a Rab5 effector and prevents Atg8 lipidation at endosomes. J Cell Sci 2022; 135:274866. [PMID: 35343566 DOI: 10.1242/jcs.259421] [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: 09/30/2021] [Accepted: 03/18/2022] [Indexed: 01/18/2023] Open
Abstract
Lysosomes mediate degradation of macromolecules to their precursors for their cellular recycling. Additionally, lysosome-related organelles mediate cell type-specific functions. The Chédiak-Higashi syndrome is an autosomal, recessive disease, in which loss of the protein LYST causes defects in lysosomes and lysosome-related organelles. The molecular function of LYST, however, is largely unknown. Here, we dissected the function of the yeast LYST homolog, Bph1. We show that Bph1 is an endosomal protein, and an effector of the minor Rab5 isoform Ypt52. Strikingly, the bph1▵ mutant has lipidated Atg8 on their endosomes, which is sorted via late endosomes into the vacuole lumen under non-autophagy inducing conditions. In agreement, proteomics of bph1▵ vacuoles reveal an accumulation of Atg8, reduced flux via selective autophagy, and defective endocytosis. Additionally, bph1▵ cells have reduced autophagic flux under starvation conditions. Our observations suggest that Bph1 is a novel Rab5 effector that maintains endosomal functioning. When lost, Atg8 is lipidated at endosomes even during normal growth and ends up in the vacuole lumen. Thus, our results contribute to the understanding of the role of LYST-related proteins and associated diseases.
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Affiliation(s)
- Prado Vargas Duarte
- Osnabrück University, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Ralph Hardenberg
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Muriel Mari
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Stefan Walter
- Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs), Barbarastrasse 11, 49076 Osnabrück, Germany
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Florian Fröhlich
- Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs), Barbarastrasse 11, 49076 Osnabrück, Germany.,Osnabrück University, Department of Biology/Chemistry, Molecular Membrane Biology section, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Ayelén González Montoro
- Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs), Barbarastrasse 11, 49076 Osnabrück, Germany.,Osnabrück University, Department of Biology/Chemistry, Cellular Communication Laboratory, Barbarastrasse 13, 49076 Osnabrück, Germany
| | - Christian Ungermann
- Osnabrück University, Department of Biology/Chemistry, Biochemistry section, Barbarastrasse 13, 49076 Osnabrück, Germany.,Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs), Barbarastrasse 11, 49076 Osnabrück, Germany
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10
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Ding X, Zhang X, Paez-Valencia J, McLoughlin F, Reyes FC, Morohashi K, Grotewold E, Vierstra RD, Otegui MS. Microautophagy Mediates Vacuolar Delivery of Storage Proteins in Maize Aleurone Cells. FRONTIERS IN PLANT SCIENCE 2022; 13:833612. [PMID: 35251104 PMCID: PMC8894768 DOI: 10.3389/fpls.2022.833612] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Accepted: 01/28/2022] [Indexed: 06/14/2023]
Abstract
The molecular machinery orchestrating microautophagy, whereby eukaryotic cells sequester autophagic cargo by direct invagination of the vacuolar/lysosomal membrane, is still largely unknown, especially in plants. Here, we demonstrate microautophagy of storage proteins in the maize aleurone cells of the endosperm and analyzed proteins with potential regulatory roles in this process. Within the cereal endosperm, starchy endosperm cells accumulate storage proteins (mostly prolamins) and starch whereas the peripheral aleurone cells store oils, storage proteins, and specialized metabolites. Although both cell types synthesize prolamins, they employ different pathways for their subcellular trafficking. Starchy endosperm cells accumulate prolamins in protein bodies within the endoplasmic reticulum (ER), whereas aleurone cells deliver prolamins to vacuoles via an autophagic mechanism, which we show is by direct association of ER prolamin bodies with the tonoplast followed by engulfment via microautophagy. To identify candidate proteins regulating this process, we performed RNA-seq transcriptomic comparisons of aleurone and starchy endosperm tissues during seed development and proteomic analysis on tonoplast-enriched fractions of aleurone cells. From these datasets, we identified 10 candidate proteins with potential roles in membrane modification and/or microautophagy, including phospholipase-Dα5 and a possible EUL-like lectin. We found that both proteins increased the frequency of tonoplast invaginations when overexpressed in Arabidopsis leaf protoplasts and are highly enriched at the tonoplast surface surrounding ER protein bodies in maize aleurone cells, thus supporting their potential connections to microautophagy. Collectively, this candidate list now provides useful tools to study microautophagy in plants.
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Affiliation(s)
- Xinxin Ding
- Department of Botany, University of Wisconsin-Madison, Madison, WI, United States
- Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Madison, WI, United States
| | - Xiaoguo Zhang
- Department of Botany, University of Wisconsin-Madison, Madison, WI, United States
- Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Madison, WI, United States
| | - Julio Paez-Valencia
- Department of Botany, University of Wisconsin-Madison, Madison, WI, United States
- Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Madison, WI, United States
| | - Fionn McLoughlin
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Francisca C. Reyes
- Department of Botany, University of Wisconsin-Madison, Madison, WI, United States
| | - Kengo Morohashi
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, United States
| | - Erich Grotewold
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, United States
| | - Richard D. Vierstra
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Marisa S. Otegui
- Department of Botany, University of Wisconsin-Madison, Madison, WI, United States
- Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Madison, WI, United States
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11
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Cho TS, Beigaitė E, Klein NE, Sweeney ST, Bhattacharya MRC. The Putative Drosophila TMEM184B Ortholog Tmep Ensures Proper Locomotion by Restraining Ectopic Firing at the Neuromuscular Junction. Mol Neurobiol 2022; 59:2605-2619. [PMID: 35107803 PMCID: PMC9018515 DOI: 10.1007/s12035-022-02760-3] [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: 09/13/2021] [Accepted: 01/20/2022] [Indexed: 11/29/2022]
Abstract
TMEM184B is a putative seven-pass membrane protein that promotes axon degeneration after injury. TMEM184B mutation causes aberrant neuromuscular architecture and sensory and motor behavioral defects in mice. The mechanism through which TMEM184B causes neuromuscular defects is unknown. We employed Drosophila melanogaster to investigate the function of the closely related gene, Tmep (CG12004), at the neuromuscular junction. We show that Tmep is required for full adult viability and efficient larval locomotion. Tmep mutant larvae have a reduced body contraction rate compared to controls, with stronger deficits in females. In recordings from body wall muscles, Tmep mutants show substantial hyperexcitability, with many postsynaptic potentials fired in response to a single stimulation, consistent with a role for Tmep in restraining synaptic excitability. Additional branches and satellite boutons at Tmep mutant neuromuscular junctions are consistent with an activity-dependent synaptic overgrowth. Tmep is expressed in endosomes and synaptic vesicles within motor neurons, suggesting a possible role in synaptic membrane trafficking. Using RNAi knockdown, we show that Tmep is required in motor neurons for proper larval locomotion and excitability, and that its reduction increases levels of presynaptic calcium. Locomotor defects can be rescued by presynaptic knockdown of endoplasmic reticulum calcium channels or by reducing evoked release probability, further suggesting that excess synaptic activity drives behavioral deficiencies. Our work establishes a critical function for Tmep in the regulation of synaptic transmission and locomotor behavior.
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Affiliation(s)
- Tiffany S Cho
- Department of Neuroscience, University of Arizona, 1040 E 4th Street, Tucson, AZ, 85721, USA
| | - Eglė Beigaitė
- Department of Biology, University of York, York, YO10 5DD, UK.,York Biomedical Research Institute, University of York, York, YO10 5DD, UK
| | - Nathaniel E Klein
- Department of Neuroscience, University of Arizona, 1040 E 4th Street, Tucson, AZ, 85721, USA
| | - Sean T Sweeney
- Department of Biology, University of York, York, YO10 5DD, UK.,York Biomedical Research Institute, University of York, York, YO10 5DD, UK
| | - Martha R C Bhattacharya
- Department of Neuroscience, University of Arizona, 1040 E 4th Street, Tucson, AZ, 85721, USA.
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