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Takeo Y, Crite M, Mehmood K, DiMaio D. γ-secretase facilitates retromer-mediated retrograde transport. J Cell Sci 2025; 138:JCS263538. [PMID: 39865938 PMCID: PMC11883284 DOI: 10.1242/jcs.263538] [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: 09/12/2024] [Accepted: 01/14/2025] [Indexed: 01/28/2025] Open
Abstract
Retromer mediates retrograde transport of protein cargoes from endosomes to the trans-Golgi network (TGN). γ-secretase is a protease that cleaves the transmembrane domain of its target proteins. Although retromer can form a stable complex with γ-secretase, the functional consequences of this interaction are not known. Here, we report that retromer-mediated retrograde protein trafficking in cultured human epithelial cells is impaired by the γ-secretase inhibitor XXI or by knockout of PS1 (also known as PSEN1), the catalytic subunit of γ-secretase. These treatments inhibited endosome-to-TGN trafficking of retromer-dependent retrograde cellular cargoes, divalent metal transporter 1 isoform II, cation-independent mannose-6-phosphate receptor and shiga toxin, whereas trafficking of retromer-independent cargoes, cholera toxin and a mutant CIMPR unable to bind retromer was not affected. Moreover, we found that γ-secretase associates with retromer cargoes even in the absence of retromer. XXI treatment and PS1 knockout did not inhibit the ability of retromer or γ-secretase to associate with cargo and did not affect the expression of retromer subunits or Rab7-GTP, which regulates retromer-cargo interaction. These results imply that the γ-secretase-retromer interaction facilitates retromer-mediated retrograde trafficking of cellular transmembrane proteins.
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Affiliation(s)
- Yuka Takeo
- Department of Genetics, Yale School of Medicine, New Haven, CT 06510, USA
| | - Mac Crite
- Department of Genetics, Yale School of Medicine, New Haven, CT 06510, USA
| | - Kashif Mehmood
- Department of Genetics, Yale School of Medicine, New Haven, CT 06510, USA
| | - Daniel DiMaio
- Department of Genetics, Yale School of Medicine, New Haven, CT 06510, USA
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06510, USA
- Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT 06510, USA
- Yale Cancer Center, Yale School of Medicine, New Haven, CT 06510, USA
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2
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Takeo Y, Crite M, DiMaio D. γ-secretase facilitates retromer-mediated retrograde transport. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.07.597932. [PMID: 38895404 PMCID: PMC11185792 DOI: 10.1101/2024.06.07.597932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
The retromer complex mediates retrograde transport of protein cargos from endosomes to the trans-Golgi network (TGN). γ-secretase is a multisubunit protease that cleaves the transmembrane domain of its target proteins. Mutations in genes encoding subunits of retromer or γ-secretase can cause familial Alzheimer disease (AD) and other degenerative neurological diseases. It has been reported that retromer interacts with γ-secretase, but the consequences of this interaction are not known. Here, we report that retromer-mediated retrograde protein trafficking in cultured human epithelial cells is impaired by inhibition of γ-secretase activity or by genetic elimination of γ-secretase. γ-secretase inhibitor XXI and knockout of PS1, the catalytic subunit of γ-secretase, inhibit endosome to TGN trafficking of retromer-dependent retrograde cargos, divalent metal transporter 1 isoform II (DMT1-II), cation-independent mannose-6-phosphate receptor (CIMPR), and shiga toxin. Trafficking of retromer-independent cargos, such as cholera toxin and a CIMPR mutant that does not bind to retromer was not affected by γ-secretase inhibition. XXI treatment and PS1 KO inhibit interaction of γ-secretase with retromer but do not inhibit the association of cargo with retromer or with γ-secretase in intact cells. Similarly, these treatments do not affect the level of Rab7-GTP, which regulates retromer-cargo interaction. These results suggest that the γ-secretase-retromer interaction facilitates retromer-mediated retrograde trafficking.
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Affiliation(s)
- Yuka Takeo
- Department of Genetics, Yale School of Medicine
| | - Mac Crite
- Department of Genetics, Yale School of Medicine
- Current affiliation: American University
| | - Daniel DiMaio
- Department of Genetics, Yale School of Medicine
- Department of Molecular Biophysics and Biochemistry, Yale University
- Department of Therapeutic Radiology, Yale School of Medicine
- Yale Cancer Center, Yale School of Medicine
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3
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Overduin M, Bhat R. Recognition and remodeling of endosomal zones by sorting nexins. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184305. [PMID: 38408696 DOI: 10.1016/j.bbamem.2024.184305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2023] [Revised: 02/05/2024] [Accepted: 02/18/2024] [Indexed: 02/28/2024]
Abstract
The proteolipid code determines how cytosolic proteins find and remodel membrane surfaces. Here, we investigate how this process works with sorting nexins Snx1 and Snx3. Both proteins form sorting machines by recognizing membrane zones enriched in phosphatidylinositol 3-phosphate (PI3P), phosphatidylserine (PS) and cholesterol. This co-localized combination forms a unique "lipid codon" or lipidon that we propose is responsible for endosomal targeting, as revealed by structures and interactions of their PX domain-based readers. We outline a membrane recognition and remodeling mechanism for Snx1 and Snx3 involving this code element alongside transmembrane pH gradients, dipole moment-guided docking and specific protein-protein interactions. This generates an initial membrane-protein assembly (memtein) that then recruits retromer and additional PX proteins to recruit cell surface receptors for sorting to the trans-Golgi network (TGN), lysosome and plasma membranes. Post-translational modification (PTM) networks appear to regulate how the sorting machines form and operate at each level. The commonalities and differences between these sorting nexins show how the proteolipid code orchestrates parallel flows of molecular information from ribosome emergence to organelle genesis, and illuminates a universally applicable model of the membrane.
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Affiliation(s)
- Michael Overduin
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
| | - Rakesh Bhat
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
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Simonetti B, Daly JL, Cullen PJ. Out of the ESCPE room: Emerging roles of endosomal SNX-BARs in receptor transport and host-pathogen interaction. Traffic 2023; 24:234-250. [PMID: 37089068 PMCID: PMC10768393 DOI: 10.1111/tra.12885] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 02/22/2023] [Accepted: 03/28/2023] [Indexed: 04/25/2023]
Abstract
Several functions of the human cell, such as sensing nutrients, cell movement and interaction with the surrounding environment, depend on a myriad of transmembrane proteins and their associated proteins and lipids (collectively termed "cargoes"). To successfully perform their tasks, cargo must be sorted and delivered to the right place, at the right time, and in the right amount. To achieve this, eukaryotic cells have evolved a highly organized sorting platform, the endosomal network. Here, a variety of specialized multiprotein complexes sort cargo into itineraries leading to either their degradation or their recycling to various organelles for further rounds of reuse. A key sorting complex is the Endosomal SNX-BAR Sorting Complex for Promoting Exit (ESCPE-1) that promotes the recycling of an array of cargos to the plasma membrane and/or the trans-Golgi network. ESCPE-1 recognizes a hydrophobic-based sorting motif in numerous cargoes and orchestrates their packaging into tubular carriers that pinch off from the endosome and travel to the target organelle. A wide range of pathogens mimic this sorting motif to hijack ESCPE-1 transport to promote their invasion and survival within infected cells. In other instances, ESCPE-1 exerts restrictive functions against pathogens by limiting their replication and infection. In this review, we discuss ESCPE-1 assembly and functions, with a particular focus on recent advances in the understanding of its role in membrane trafficking, cellular homeostasis and host-pathogen interaction.
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Affiliation(s)
- Boris Simonetti
- Charles River Laboratories, Discovery House, Quays Office ParkConference Avenue, PortisheadBristolUK
| | - James L. Daly
- Department of Infectious DiseasesSchool of Immunology and Microbial Sciences, Guy's Hospital, King's College LondonLondonUK
| | - Peter J. Cullen
- School of Biochemistry, Faculty of Life Sciences, Biomedical Sciences BuildingUniversity of BristolBristolUK
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5
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Da Graça J, Morel E. Canonical and Non-Canonical Roles of SNX1 and SNX2 in Endosomal Membrane Dynamics. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2023; 6:25152564231217867. [PMID: 38033809 PMCID: PMC10683387 DOI: 10.1177/25152564231217867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 11/07/2023] [Accepted: 11/15/2023] [Indexed: 12/02/2023]
Abstract
Sorting nexins (SNXs) are a family of membrane-binding proteins known to play a critical role in regulating endocytic pathway sorting and endosomal membrane trafficking. Among them, SNX1 and SNX2 are members of the SNX-BAR subfamily and possess a membrane-curvature domain and a phosphoinositide-binding domain, which enables their stabilization at the phosphatidylinositol-3-phosphate (PI3P)-positive surface of endosomes. While their binding to PI3P-positive platforms facilitates interaction with endosomal partners and stabilization at the endosomal membrane, their SNX-BAR region is pivotal for generating membrane tubulation from endosomal compartments. In this context, their primary identified biological roles-and their partnership-are tightly associated with the retromer and endosomal SNX-BAR sorting complex for promoting exit 1 complex trafficking, facilitating the transport of cargoes from early endosomes to the secretory pathway. However, recent literature indicates that these proteins also possess biological functions in other aspects of endosomal features and sorting processes. Notably, SNX2 has been found to regulate endosome-endoplasmic reticulum (ER) contact sites through its interaction with VAP proteins at the ER membrane. Furthermore, data from our laboratory show that SNX1 and SNX2 are involved in the tubulation of early endosomes toward ER sites associated with autophagy initiation during starvation. These findings shed light on a novel role of SNXs in inter-organelle tethering and communication. In this concise review, we will explore the non-retromer functions of SNX1 and SNX2, specifically focusing on their involvement in endosomal membrane dynamics during stress sensing and autophagy-associated processes.
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Affiliation(s)
- Juliane Da Graça
- Université Paris Cité, INSERM UMR-S1151, CNRS UMR-S8253, Institut Necker Enfants Malades, Paris, France
| | - Etienne Morel
- Université Paris Cité, INSERM UMR-S1151, CNRS UMR-S8253, Institut Necker Enfants Malades, Paris, France
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Lu Y, He P, Zhang Y, Ren Y, Zhang L. The emerging roles of retromer and sorting nexins in the life cycle of viruses. Virol Sin 2022; 37:321-330. [PMID: 35513271 PMCID: PMC9057928 DOI: 10.1016/j.virs.2022.04.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Accepted: 04/12/2022] [Indexed: 02/06/2023] Open
Abstract
Retromer and sorting nexins (SNXs) transport cargoes from endosomes to the trans-Golgi network or plasma membrane. Recent studies have unveiled the emerging roles for retromer and SNXs in the life cycle of viruses, including members of Coronaviridae, Flaviviridae and Retroviridae. Key components of retromer/SNXs, such as Vps35, Vps26, SNX5 and SNX27, can affect multiple steps of the viral life cycle, including facilitating the entry of viruses into cells, participating in viral replication, and promoting the assembly of virions. Here we present a comprehensive updated review on the interplay between retromer/SNXs and virus, which will shed mechanistic insights into controlling virus infection.
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Affiliation(s)
- Yue Lu
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, 250013, China; Department of Pathogen Biology, School of Basic Medical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250117, China; Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250117, China
| | - Ping He
- Department of Pathogen Biology, School of Basic Medical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250117, China; Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250117, China
| | - Yuxuan Zhang
- Department of Pathogen Biology, School of Basic Medical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250117, China; Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250117, China
| | - Yongwen Ren
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, 250013, China; Department of Pathogen Biology, School of Basic Medical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250117, China; Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250117, China
| | - Leiliang Zhang
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, 250013, China; Department of Pathogen Biology, School of Basic Medical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250117, China; Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250117, China.
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Yoshida S, Hasegawa T. Beware of Misdelivery: Multifaceted Role of Retromer Transport in Neurodegenerative Diseases. Front Aging Neurosci 2022; 14:897688. [PMID: 35601613 PMCID: PMC9120357 DOI: 10.3389/fnagi.2022.897688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 04/19/2022] [Indexed: 11/13/2022] Open
Abstract
Retromer is a highly integrated multimeric protein complex that mediates retrograde cargo sorting from endosomal compartments. In concert with its accessory proteins, the retromer drives packaged cargoes to tubular and vesicular structures, thereby transferring them to the trans-Golgi network or to the plasma membrane. In addition to the endosomal trafficking, the retromer machinery participates in mitochondrial dynamics and autophagic processes and thus contributes to cellular homeostasis. The retromer components and their associated molecules are expressed in different types of cells including neurons and glial cells, and accumulating evidence from genetic and biochemical studies suggests that retromer dysfunction is profoundly involved in the pathogenesis of neurodegenerative diseases including Alzheimer’s Disease and Parkinson’s disease. Moreover, targeting retromer components could alleviate the neurodegenerative process, suggesting that the retromer complex may serve as a promising therapeutic target. In this review, we will provide the latest insight into the regulatory mechanisms of retromer and discuss how its dysfunction influences the pathological process leading to neurodegeneration.
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Affiliation(s)
- Shun Yoshida
- Division of Neurology, Department of Neuroscience and Sensory Organs, Tohoku University Graduate School of Medicine, Sendai, Japan
- Department of Neurology, National Hospital Organization Yonezawa Hospital, Yonezawa, Japan
| | - Takafumi Hasegawa
- Division of Neurology, Department of Neuroscience and Sensory Organs, Tohoku University Graduate School of Medicine, Sendai, Japan
- *Correspondence: Takafumi Hasegawa,
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8
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Nakano A. The Golgi Apparatus and its Next-Door Neighbors. Front Cell Dev Biol 2022; 10:884360. [PMID: 35573670 PMCID: PMC9096111 DOI: 10.3389/fcell.2022.884360] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Accepted: 03/28/2022] [Indexed: 12/20/2022] Open
Abstract
The Golgi apparatus represents a central compartment of membrane traffic. Its apparent architecture, however, differs considerably among species, from unstacked and scattered cisternae in the budding yeast Saccharomyces cerevisiae to beautiful ministacks in plants and further to gigantic ribbon structures typically seen in mammals. Considering the well-conserved functions of the Golgi, its fundamental structure must have been optimized despite seemingly different architectures. In addition to the core layers of cisternae, the Golgi is usually accompanied by next-door compartments on its cis and trans sides. The trans-Golgi network (TGN) can be now considered as a compartment independent from the Golgi stack. On the cis side, the intermediate compartment between the ER and the Golgi (ERGIC) has been known in mammalian cells, and its functional equivalent is now suggested for yeast and plant cells. High-resolution live imaging is extremely powerful for elucidating the dynamics of these compartments and has revealed amazing similarities in their behaviors, indicating common mechanisms conserved along the long course of evolution. From these new findings, I would like to propose reconsideration of compartments and suggest a new concept to describe their roles comprehensively around the Golgi and in the post-Golgi trafficking.
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Ciesielska A, Krawczy M, Sas-Nowosielska H, Hromada-Judycka A, Kwiatkowska K. CD14 recycling modulates LPS-induced inflammatory responses of murine macrophages. Traffic 2022; 23:310-330. [PMID: 35411668 DOI: 10.1111/tra.12842] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Revised: 03/07/2022] [Accepted: 04/01/2022] [Indexed: 11/28/2022]
Abstract
TLR4 is activated by the bacterial endotoxin lipopolysaccharide (LPS) and triggers two pro-inflammatory signaling cascades: a MyD88-dependent one in the plasma membrane, and the following TRIF-dependent one in endosomes. An inadequate inflammatory reaction can be detrimental for the organism by leading to sepsis. Therefore, novel approaches to therapeutic modulation of TLR4 signaling are being sought after. The TLR4 activity is tightly connected with the presence of CD14, a GPI-anchored protein that transfers LPS monomers to the receptor and controls its endocytosis. In this study we focused on CD14 trafficking as a still poorly understood factor affecting TLR4 activity. Two independent assays were used to show that after endocytosis CD14 can recycle back to the plasma membrane in both unstimulated and stimulated cells. This route of CD14 trafficking can be controlled by sorting nexins (SNX) 1, 2, and 6, and is important for maintaining the surface level and the total level of CD14, but can also affect the amount of TLR4. Silencing of these SNXs attenuated especially the CD14-dependent endosomal signaling of TLR4, making them a new target for therapeutic regulation of the inflammatory response of macrophages to LPS.
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Affiliation(s)
- Anna Ciesielska
- Laboratory of Molecular Membrane Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland
| | - Marta Krawczy
- Laboratory of Molecular Membrane Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland
| | - Hanna Sas-Nowosielska
- Laboratory of Molecular Basis of Cell Motility, Nencki Institute of Experimental Biology of Polish Academy of Sciences, 3 Pasteur St., 02-093 Warsaw, Poland
| | - Aneta Hromada-Judycka
- Laboratory of Molecular Membrane Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland
| | - Katarzyna Kwiatkowska
- Laboratory of Molecular Membrane Biology, Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland
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10
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Selyunin AS, Nieves-Merced K, Li D, McHardy SF, Mukhopadhyay S. Tamoxifen Derivatives Alter Retromer-Dependent Endosomal Tubulation and Sorting to Block Retrograde Trafficking of Shiga Toxins. Toxins (Basel) 2021; 13:toxins13060424. [PMID: 34203879 PMCID: PMC8232625 DOI: 10.3390/toxins13060424] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 06/09/2021] [Accepted: 06/11/2021] [Indexed: 12/19/2022] Open
Abstract
Shiga toxin 1 and 2 (STx1 and STx2) undergo retrograde trafficking to reach the cytosol of cells where they target ribosomes. As retrograde trafficking is essential for disease, inhibiting STx1/STx2 trafficking is therapeutically promising. Recently, we discovered that the chemotherapeutic drug tamoxifen potently inhibits the trafficking of STx1/STx2 at the critical early endosome-to-Golgi step. We further reported that the activity of tamoxifen against STx1/STx2 is independent of its selective estrogen receptor modulator (SERM) property and instead depends on its weakly basic chemical nature, which allows tamoxifen to increase endolysosomal pH and alter the recruitment of retromer to endosomes. The goal of the current work was to obtain a better understanding of the mechanism of action of tamoxifen against the more disease-relevant toxin STx2, and to differentiate between the roles of changes in endolysosomal pH and retromer function. Structure activity relationship (SAR) analyses revealed that a weakly basic amine group was essential for anti-STx2 activity. However, ability to deacidify endolysosomes was not obligatorily necessary because a tamoxifen derivative that did not increase endolysosomal pH exerted reduced, but measurable, activity. Additional assays demonstrated that protective derivatives inhibited the formation of retromer-dependent, Golgi-directed, endosomal tubules, which mediate endosome-to-Golgi transport, and the sorting of STx2 into these tubules. These results identify retromer-mediated endosomal tubulation and sorting to be fundamental processes impacted by tamoxifen; provide an explanation for the inhibitory effect of tamoxifen on STx2; and have important implications for the therapeutic use of tamoxifen, including its development for treating Shiga toxicosis.
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Affiliation(s)
- Andrey S. Selyunin
- Division of Pharmacology and Toxicology, Institute for Neuroscience, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA; (A.S.S.); (D.L.)
| | - Karinel Nieves-Merced
- Center for Innovative Drug Discovery, Department of Chemistry, University of Texas San Antonio, San Antonio, TX 78249, USA;
| | - Danyang Li
- Division of Pharmacology and Toxicology, Institute for Neuroscience, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA; (A.S.S.); (D.L.)
| | - Stanton F. McHardy
- Center for Innovative Drug Discovery, Department of Chemistry, University of Texas San Antonio, San Antonio, TX 78249, USA;
- Correspondence: (S.F.M.); (S.M.)
| | - Somshuvra Mukhopadhyay
- Division of Pharmacology and Toxicology, Institute for Neuroscience, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA; (A.S.S.); (D.L.)
- Correspondence: (S.F.M.); (S.M.)
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11
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The Protein Toxins Ricin and Shiga Toxin as Tools to Explore Cellular Mechanisms of Internalization and Intracellular Transport. Toxins (Basel) 2021; 13:toxins13060377. [PMID: 34070659 PMCID: PMC8227415 DOI: 10.3390/toxins13060377] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/12/2021] [Accepted: 05/22/2021] [Indexed: 12/18/2022] Open
Abstract
Protein toxins secreted by bacteria and found in plants can be threats to human health. However, their extreme toxicity can also be exploited in different ways, e.g., to produce hybrid toxins directed against cancer cells and to study transport mechanisms in cells. Investigations during the last decades have shown how powerful these molecules are as tools in cell biological research. Here, we first present a partly historical overview, with emphasis on Shiga toxin and ricin, of how such toxins have been used to characterize processes and proteins of importance for their trafficking. In the second half of the article, we describe how one can now use toxins to investigate the role of lipid classes for intracellular transport. In recent years, it has become possible to quantify hundreds of lipid species using mass spectrometry analysis. Thus, it is also now possible to explore the importance of lipid species in intracellular transport. The detailed analyses of changes in lipids seen under conditions of inhibited toxin transport reveal previously unknown connections between syntheses of lipid classes and demonstrate the ability of cells to compensate under given conditions.
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12
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Yang L, Tan W, Yang X, You Y, Wang J, Wen G, Zhong J. Sorting nexins: A novel promising therapy target for cancerous/neoplastic diseases. J Cell Physiol 2020; 236:3317-3335. [PMID: 33090492 DOI: 10.1002/jcp.30093] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/18/2020] [Accepted: 09/22/2020] [Indexed: 12/17/2022]
Abstract
Sorting nexins (SNXs) are a diverse group of cytoplasmic- and membrane-associated phosphoinositide-binding proteins containing the PX domain proteins. The function of SNX proteins in regulating intracellular protein trafficking consists of endocytosis, endosomal sorting, and endosomal signaling. Dysfunctions of SNX proteins are demonstrated to be involved in several cancerous/neoplastic diseases. Here, we review the accumulated evidence of the molecular structure and biological function of SNX proteins and discuss the regulatory role of SNX proteins in distinct cancerous/neoplastic diseases. SNX family proteins may be a valuable potential biomarker and therapeutic strategy for diagnostics and treatment of cancerous/neoplastic diseases.
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Affiliation(s)
- Lu Yang
- Hunan Province Key Laboratory of Tumor Cellular & Molecular Pathology, Cancer Research Institute, University of South China, Hengyang, Hunan, China
- Institute of Clinical Medicine, the First Affiliated Hospital of University of South China, Hengyang, Hunan, China
| | - Weihua Tan
- Institute of Clinical Medicine, the First Affiliated Hospital of University of South China, Hengyang, Hunan, China
- Emergency Department, the First Affiliated Hospital of University of South China, Hengyang, Hunan, China
| | - Xinzhi Yang
- Hunan Province Key Laboratory of Tumor Cellular & Molecular Pathology, Cancer Research Institute, University of South China, Hengyang, Hunan, China
- Institute of Clinical Medicine, the First Affiliated Hospital of University of South China, Hengyang, Hunan, China
| | - Yong You
- Research Lab of Translational Medicine, Hengyang Medical College, University of South China, Hengyang, Hunan, China
| | - Jing Wang
- Research Lab of Translational Medicine, Hengyang Medical College, University of South China, Hengyang, Hunan, China
| | - Gebo Wen
- Hunan Province Key Laboratory of Tumor Cellular & Molecular Pathology, Cancer Research Institute, University of South China, Hengyang, Hunan, China
- Institute of Clinical Medicine, the First Affiliated Hospital of University of South China, Hengyang, Hunan, China
| | - Jing Zhong
- Hunan Province Key Laboratory of Tumor Cellular & Molecular Pathology, Cancer Research Institute, University of South China, Hengyang, Hunan, China
- Institute of Clinical Medicine, the First Affiliated Hospital of University of South China, Hengyang, Hunan, China
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13
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Targeting the Early Endosome-to-Golgi Transport of Shiga Toxins as a Therapeutic Strategy. Toxins (Basel) 2020; 12:toxins12050342. [PMID: 32456007 PMCID: PMC7290323 DOI: 10.3390/toxins12050342] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 05/19/2020] [Accepted: 05/20/2020] [Indexed: 02/07/2023] Open
Abstract
Shiga toxin (STx) produced by Shigella and closely related Shiga toxin 1 and 2 (STx1 and STx2) synthesized by Shiga toxin-producing Escherichia coli (STEC) are bacterial AB5 toxins. All three toxins target kidney cells and may cause life-threatening renal disease. While Shigella infections can be treated with antibiotics, resistance is increasing. Moreover, antibiotic therapy is contraindicated for STEC, and there are no definitive treatments for STEC-induced disease. To exert cellular toxicity, STx, STx1, and STx2 must undergo retrograde trafficking to reach their cytosolic target, ribosomes. Direct transport from early endosomes to the Golgi apparatus is an essential step that allows the toxins to bypass degradative late endosomes and lysosomes. The essentiality of this transport step also makes it an ideal target for the development of small-molecule inhibitors of toxin trafficking as potential therapeutics. Here, we review the recent advances in understanding the molecular mechanisms of the early endosome-to-Golgi transport of STx, STx1, and STx2, as well as the development of small-molecule inhibitors of toxin trafficking that act at the endosome/Golgi interface.
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14
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Morimoto K, Suzuki N, Tanida I, Kakuta S, Furuta Y, Uchiyama Y, Hanada K, Suzuki Y, Yamaji T. Blood group P1 antigen-bearing glycoproteins are functional but less efficient receptors of Shiga toxin than conventional glycolipid-based receptors. J Biol Chem 2020; 295:9490-9501. [PMID: 32409578 DOI: 10.1074/jbc.ra120.013926] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 05/12/2020] [Indexed: 12/29/2022] Open
Abstract
Shiga toxin (STx) is a virulence factor produced by enterohemorrhagic Escherichia coli. STx is taken up by mammalian host cells by binding to the glycosphingolipid (GSL) globotriaosylceramide (Gb3; Galα1-4Galβ1-4Glc-ceramide) and causes cell death after its retrograde membrane transport. However, the contribution of the hydrophobic portion of Gb3 (ceramide) to STx transport remains unclear. In pigeons, blood group P1 glycan antigens (Galα1-4Galβ1-4GlcNAc-) are expressed on glycoproteins that are synthesized by α1,4-galactosyltransferase 2 (pA4GalT2). To examine whether these glycoproteins can also function as STx receptors, here we constructed glycan-remodeled HeLa cell variants lacking Gb3 expression but instead expressing pA4GalT2-synthesized P1 glycan antigens on glycoproteins. We compared STx binding and sensitivity of these variants with those of the parental, Gb3-expressing HeLa cells. The glycan-remodeled cells bound STx1 via N-glycans of glycoproteins and were sensitive to STx1 even without Gb3 expression, indicating that P1-containing glycoproteins also function as STx receptors. However, these variants were significantly less sensitive to STx than the parent cells. Fluorescence microscopy and correlative light EM revealed that the STx1 B subunit accumulates to lower levels in the Golgi apparatus after glycoprotein-mediated than after Gb3-mediated uptake but instead accumulates in vacuole-like structures probably derived from early endosomes. Furthermore, coexpression of Galα1-4Gal on both glycoproteins and GSLs reduced the sensitivity of cells to STx1 compared with those expressing Galα1-4Gal only on GSLs, probably because of competition for STx binding or internalization. We conclude that lipid-based receptors are much more effective in STx retrograde transport and mediate greater STx cytotoxicity than protein-based receptors.
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Affiliation(s)
- Kanta Morimoto
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan.,Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, Tokyo, Japan
| | - Noriko Suzuki
- Graduate School of Science and Technology, Niigata University, Niigata, Japan
| | - Isei Tanida
- Department of Cellular and Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Soichiro Kakuta
- Department of Cellular and Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo, Japan.,Laboratory of Morphology and Image Analysis, Biomedical Research Center, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Yoko Furuta
- Department of Cellular and Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Yasuo Uchiyama
- Department of Cellular and Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Kentaro Hanada
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan
| | - Yusuke Suzuki
- Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, Tokyo, Japan
| | - Toshiyuki Yamaji
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan
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15
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Lingwood C. Verotoxin Receptor-Based Pathology and Therapies. Front Cell Infect Microbiol 2020; 10:123. [PMID: 32296648 PMCID: PMC7136409 DOI: 10.3389/fcimb.2020.00123] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 03/05/2020] [Indexed: 12/22/2022] Open
Abstract
Verotoxin, VT (aka Shiga toxin,Stx) is produced by enterohemorrhagic E. coli (EHEC) and is the key pathogenic factor in EHEC-induced hemolytic uremic syndrome (eHUS-hemolytic anemia/thrombocytopenia/glomerular infarct) which can follow gastrointestinal EHEC infection, particularly in children. This AB5 subunit toxin family bind target cell globotriaosyl ceramide (Gb3), a glycosphingolipid (GSL) (aka CD77, pk blood group antigen) of the globoseries of neutral GSLs, initiating lipid raft-dependent plasma membrane Gb3 clustering, membrane curvature, invagination, scission, endosomal trafficking, and retrograde traffic via the TGN to the Golgi, and ER. In the ER, A/B subunits separate and the A subunit hijacks the ER reverse translocon (dislocon-used to eliminate misfolded proteins-ER associated degradation-ERAD) for cytosolic access. This property has been used to devise toxoid-based therapy to temporarily block ERAD and rescue the mutant phenotype of several genetic protein misfolding diseases. The A subunit avoids cytosolic proteosomal degradation, to block protein synthesis via its RNA glycanase activity. In humans, Gb3 is primarily expressed in the kidney, particularly in the glomerular endothelial cells. Here, Gb3 is in lipid rafts (more ordered membrane domains which accumulate GSLs/cholesterol) whereas renal tubular Gb3 is in the non-raft membrane fraction, explaining the basic pathology of eHUS (glomerular endothelial infarct). Females are more susceptible and this correlates with higher renal Gb3 expression. HUS can be associated with encephalopathy, more commonly following verotoxin 2 exposure. Gb3 is expressed in the microvasculature of the brain. All members of the VT family bind Gb3, but with varying affinity. VT2e (pig edema toxin) binds Gb4 preferentially. Verotoxin-specific therapeutics based on chemical analogs of Gb3, though effective in vitro, have failed in vivo. While some analogs are effective in animal models, there are no good rodent models of eHUS since Gb3 is not expressed in rodent glomeruli. However, the mouse mimics the neurological symptoms more closely and provides an excellent tool to assess therapeutics. In addition to direct cytotoxicity, other factors including VT–induced cytokine release and aberrant complement cascade, are now appreciated as important in eHUS. Based on atypical HUS therapy, treatment of eHUS patients with anticomplement antibodies has proven effective in some cases. A recent switch using stem cells to try to reverse, rather than prevent VT induced pathology may prove a more effective methodology.
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Affiliation(s)
- Clifford Lingwood
- Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto, ON, Canada
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16
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Functional dissection of the retrograde Shiga toxin trafficking inhibitor Retro-2. Nat Chem Biol 2020; 16:327-336. [PMID: 32080624 PMCID: PMC7039708 DOI: 10.1038/s41589-020-0474-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 01/10/2020] [Indexed: 11/29/2022]
Abstract
The retrograde transport inhibitor Retro-2 has a protective effect on cells and in mice against Shiga-like toxins and ricin. Retro-2 causes toxin accumulation in early endosomes, and relocalization of the Golgi SNARE protein syntaxin-5 to the endoplasmic reticulum. The molecular mechanisms by which this is achieved remain unknown. Here, we show that Retro-2 targets the endoplasmic reticulum exit site component Sec16A, affecting anterograde transport of syntaxin-5 from the endoplasmic reticulum to the Golgi. The formation of canonical SNARE complexes involving syntaxin-5 is not affected in Retro-2-treated cells. In contrast, the interaction of syntaxin-5 with a newly discovered binding partner, the retrograde trafficking chaperone GPP130, is abolished, and we show that GPP130 must indeed bind to syntaxin-5 to drive Shiga toxin transport from endosomes to the Golgi. We thereby identify Sec16A as a druggable target, and provide evidence for a non-SNARE function for syntaxin-5 in interaction with the GPP130.
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17
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Sun S, Yang J, Xie W, Peng T, Lv Y. Complicated trafficking behaviors involved in paradoxical regulation of sortilin in lipid metabolism. J Cell Physiol 2019; 235:3258-3269. [PMID: 31608989 DOI: 10.1002/jcp.29292] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 09/30/2019] [Indexed: 11/06/2022]
Abstract
This review aims to summarize and discuss the most recent advances in our understanding of the underlying mechanisms of the paradoxical effects of sortilin on lipid metabolism. The vacuolar protein sorting 10 protein (Vps10p) domain in the sortilin protein is responsible for substrate binding. Its cytoplasmic tail interacts with adaptor molecules, and modifications can determine whether sortilin trafficking occurs via the anterograde or retrograde pathway. The complicated trafficking behaviors likely contribute to the paradoxical roles of sortilin in lipid metabolism. The anterograde pathway of sortilin trafficking in hepatocytes, enterocytes, and peripheral cells likely causes an increase in plasma lipid levels, while the retrograde pathway leads to the opposite effect. Hepatocyte sortilin functions via the anterograde or retrograde pathway in a complicated and paradoxical manner to regulate apoB-containing lipoprotein metabolism. Clarifying the regulatory mechanisms underlying the trafficking behaviors of sortilin is necessary and may lead to artificial sortilin intervention as a potential therapeutic strategy for lipid disorder diseases. Conclusively, the paradoxical regulation of sortilin in lipid metabolism is likely due to its complicated trafficking behaviors.
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Affiliation(s)
- Sha Sun
- Clinical Anatomy & Reproductive Medicine Application Institute, Hengyang Medical College, University of South China, Hengyang City, China
| | - Jing Yang
- Clinical Medical Research Institute of the First Affiliated Hospital, Hengyang Medical College, University of South China, Hengyang City, China
| | - Wei Xie
- Clinical Anatomy & Reproductive Medicine Application Institute, Hengyang Medical College, University of South China, Hengyang City, China
| | - Tianhong Peng
- Clinical Anatomy & Reproductive Medicine Application Institute, Hengyang Medical College, University of South China, Hengyang City, China
| | - Yuncheng Lv
- Clinical Anatomy & Reproductive Medicine Application Institute, Hengyang Medical College, University of South China, Hengyang City, China
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18
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Retrograde Transport by Clathrin-Coated Vesicles is Involved in Intracellular Transport of PrP Sc in Persistently Prion-Infected Cells. Sci Rep 2018; 8:12241. [PMID: 30115966 PMCID: PMC6095914 DOI: 10.1038/s41598-018-30775-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 08/03/2018] [Indexed: 12/22/2022] Open
Abstract
Intracellular dynamics of an abnormal isoform of prion protein (PrPSc) are tightly associated with prion propagation. However, the machineries involved in the intracellular trafficking of PrPSc are not fully understood. Our previous study suggested that PrPSc in persistently prion-infected cells dynamically circulates between endocytic-recycling compartments (ERCs) and peripheral regions of the cells. To investigate these machineries, we focused on retrograde transport from endosomes to the trans-Golgi network, which is one of the pathways involved in recycling of molecules. PrPSc was co-localized with components of clathrin-coated vesicles (CCVs) as well as those of the retromer complex, which are known as machineries for retrograde transport. Fractionation of intracellular compartments by density gradient centrifugation showed the presence of PrPSc and the components of CCVs in the same fractions. Furthermore, PrPSc was detected in CCVs isolated from intracellular compartments of prion-infected cells. Knockdown of clathrin interactor 1, which is one of the clathrin adaptor proteins involved in retrograde transport, did not change the amount of PrPSc, but it altered the distribution of PrPSc from ERCs to peripheral regions, including late endosomes/lysosomes. These data demonstrated that some PrPSc is transported from endosomes to ERCs by CCVs, which might be involved in the recycling of PrPSc.
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19
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Elwell C, Engel J. Emerging Role of Retromer in Modulating Pathogen Growth. Trends Microbiol 2018; 26:769-780. [PMID: 29703496 DOI: 10.1016/j.tim.2018.04.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 03/21/2018] [Accepted: 04/02/2018] [Indexed: 12/20/2022]
Abstract
Intracellular pathogens have developed elegant mechanisms to modulate host endosomal trafficking. The highly conserved retromer pathway has emerged as an important target of viruses and intravacuolar bacteria. Some pathogens require retromer function to survive. For others, retromer activity restricts intracellular growth; these pathogens must disrupt retromer function to survive. In this review, we discuss recent paradigm changes to the current model for retromer assembly and cargo selection. We highlight how the study of pathogen effectors has contributed to these fundamental insights, with a special focus on the biology and structure of two recently described bacterial effectors, Chlamydia trachomatis IncE and Legionella pneumophila RidL. These two pathogens employ distinct strategies to target retromer components and overcome restriction of intracellular growth imposed by retromer.
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Affiliation(s)
- Cherilyn Elwell
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Joanne Engel
- Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94143, USA.
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20
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Luginbuehl V, Meier N, Kovar K, Rohrer J. Intracellular drug delivery: Potential usefulness of engineered Shiga toxin subunit B for targeted cancer therapy. Biotechnol Adv 2018; 36:613-623. [PMID: 29432805 DOI: 10.1016/j.biotechadv.2018.02.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 01/30/2018] [Accepted: 02/05/2018] [Indexed: 12/15/2022]
Abstract
A treasure trove of intracellular cancer drug targets remains hidden behind cell membranes. However, engineered pathogen-derived toxins such as Shiga toxins can deliver small or macromolecular drugs to specific intracellular organelles. After binding to ganglioglobotriaosylceramide (Gb3, CD77), the non-toxic subunit B (StxB) of the Shiga-holotoxin is endocytosed and delivers its payload by a unique retrograde trafficking pathway via the endoplasmic reticulum to the cytosol. This review provides an overview of biomedical applications of StxB-based drug delivery systems in targeted cancer diagnosis and therapy. Biotechnological production of the Stx-material is discussed from the perspective of developing efficacious and safe therapeutics.
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Affiliation(s)
- Vera Luginbuehl
- Institute of Chemistry and Biotechnology, Zurich University of Applied Sciences, Grueental, P.O.X. 335, CH-8820 Waedenswil, Switzerland
| | - Nicolas Meier
- Institute of Chemistry and Biotechnology, Zurich University of Applied Sciences, Grueental, P.O.X. 335, CH-8820 Waedenswil, Switzerland
| | - Karin Kovar
- Institute of Chemistry and Biotechnology, Zurich University of Applied Sciences, Grueental, P.O.X. 335, CH-8820 Waedenswil, Switzerland
| | - Jack Rohrer
- Institute of Chemistry and Biotechnology, Zurich University of Applied Sciences, Grueental, P.O.X. 335, CH-8820 Waedenswil, Switzerland.
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21
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Mechanism of inhibition of retromer transport by the bacterial effector RidL. Proc Natl Acad Sci U S A 2018; 115:E1446-E1454. [PMID: 29386389 DOI: 10.1073/pnas.1717383115] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Retrograde vesicle trafficking pathways are responsible for returning membrane-associated components from endosomes to the Golgi apparatus and the endoplasmic reticulum (ER), and they are critical for maintaining organelle identity, lipid homeostasis, and many other cellular functions. The retrograde transport pathway has emerged as an important target for intravacuolar bacterial pathogens. The opportunistic pathogen Legionella pneumophila exploits both the secretory and recycling branches of the vesicle transport pathway for intracellular bacterial proliferation. Its Dot/Icm effector RidL inhibits the activity of the retromer by directly engaging retromer components. However, the mechanism underlying such inhibition remains unknown. Here we present the crystal structure of RidL in complex with VPS29, a subunit of the retromer. Our results demonstrate that RidL binds to a highly conserved hydrophobic pocket of VPS29. This interaction is critical for endosomal recruitment of RidL and for its inhibitory effects. RidL inhibits retromer activity by direct competition, in which it occupies the VPS29-binding site of the essential retromer regulator TBC1d5. The mechanism of retromer inhibition by RidL reveals a hotspot on VPS29 critical for recognition by its regulators that is also exploited by pathogens, and provides a structural basis for the development of small molecule inhibitors against the retromer.
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22
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Johannes L. Shiga Toxin-A Model for Glycolipid-Dependent and Lectin-Driven Endocytosis. Toxins (Basel) 2017; 9:toxins9110340. [PMID: 29068384 PMCID: PMC5705955 DOI: 10.3390/toxins9110340] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 10/15/2017] [Accepted: 10/20/2017] [Indexed: 12/27/2022] Open
Abstract
The cellular entry of the bacterial Shiga toxin and the related verotoxins has been scrutinized in quite some detail. This is due to their importance as a threat to human health. At the same time, the study of Shiga toxin has allowed the discovery of novel molecular mechanisms that also apply to the intracellular trafficking of endogenous proteins at the plasma membrane and in the endosomal system. In this review, the individual steps that lead to Shiga toxin uptake into cells will first be presented from a purely mechanistic perspective. Membrane-biological concepts will be highlighted that are often still poorly explored, such as fluctuation force-driven clustering, clathrin-independent membrane curvature generation, friction-driven scission, and retrograde sorting on early endosomes. It will then be explored whether and how these also apply to other pathogens, pathogenic factors, and cellular proteins. The molecular nature of Shiga toxin as a carbohydrate-binding protein and that of its cellular receptor as a glycosylated raft lipid will be an underlying theme in this discussion. It will thereby be illustrated how the study of Shiga toxin has led to the proposal of the GlycoLipid-Lectin (GL-Lect) hypothesis on the generation of endocytic pits in processes of clathrin-independent endocytosis.
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Affiliation(s)
- Ludger Johannes
- Cellular and Chemical Biology Department, Institut Curie, PSL Research University, U1143 INSERM, UMR3666 CNRS, 26 rue d'Ulm, 75248 Paris CEDEX 05, France.
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23
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Pillay S, Carette JE. Host determinants of adeno-associated viral vector entry. Curr Opin Virol 2017; 24:124-131. [PMID: 28672171 DOI: 10.1016/j.coviro.2017.06.003] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 05/28/2017] [Accepted: 06/09/2017] [Indexed: 12/18/2022]
Abstract
Viral vectors based on adeno-associated virus (AAV) are leading candidates for therapeutic gene delivery. Understanding rate-limiting steps in the entry of AAV vectors may be used in a rational approach to improve efficiency and specificity of transduction. This review describes our current understanding of AAV entry, a key step during infection. We discuss the identity and functions of AAV receptors and attachment factors, including the recently discovered multi-serotype receptor AAVR. We further provide an overview of other host factors that act during the trafficking stage of AAV vector transduction. In particular, we focus on cellular protein complexes associated with retrograde transport from endosomes to the trans-Golgi network. The novel insights in AAV-host interactions facilitated by technological advances in genetic screening approaches provide a greater depth in our understanding how AAV vectors exploit host factors to deliver its genetic cargo to the nucleus.
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Affiliation(s)
- Sirika Pillay
- Stanford University, Department of Microbiology and Immunology, Stanford, CA 94305, USA
| | - Jan E Carette
- Stanford University, Department of Microbiology and Immunology, Stanford, CA 94305, USA.
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24
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Role of the VPS35 D620N mutation in Parkinson's disease. Parkinsonism Relat Disord 2017; 36:10-18. [DOI: 10.1016/j.parkreldis.2016.12.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 11/29/2016] [Accepted: 12/02/2016] [Indexed: 12/21/2022]
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25
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Bhowmick S, Chakravarty C, Sellathamby S, Lal SK. The influenza A virus matrix protein 2 undergoes retrograde transport from the endoplasmic reticulum into the cytoplasm and bypasses cytoplasmic proteasomal degradation. Arch Virol 2016; 162:919-929. [PMID: 27942972 DOI: 10.1007/s00705-016-3153-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 11/07/2016] [Indexed: 11/28/2022]
Abstract
The matrix protein 2 (M2) is a spliced product of segment 7 genome of influenza A virus. Previous studies indicate its role in uncoating of the viral ribonucleoprotein complex during viral entry and in membrane scission while budding. Despite its crucial role in the viral life cycle, little is known about its subcellular distribution and dynamics. In this study, we have shown that the M2 protein is translocated from the membrane to the cytoplasm by a retrograde route via endosomes and the Golgi network. It utilizes retromer cargo while moving from the endosome to the trans-Golgi network and prevents endosome fusion with the lysosome. Further, M2 interacts with the endoplasmic-reticulum-resident AAA-ATPase p97 for its release into the cytoplasm. Our study also revealed that the M2 protein in the cellular milieu does not undergo ubiquitin-mediated proteasomal degradation. The migration of M2 through this pathway inside the infected cell suggests possible new roles that the M2 protein may have in the host cytoplasm, apart from its previously described functions.
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Affiliation(s)
- Sanchari Bhowmick
- Virology Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India
| | - Chandrani Chakravarty
- Virology Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.,Department of Biomedical Science, Bharathidasan University, Trichy, India
| | | | - Sunil K Lal
- Virology Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India. .,School of Science, Monash University, 47500, Bandar Sunway, Malaysia.
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26
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Liu JJ. Retromer-Mediated Protein Sorting and Vesicular Trafficking. J Genet Genomics 2016; 43:165-77. [PMID: 27157806 DOI: 10.1016/j.jgg.2016.02.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 02/02/2016] [Accepted: 02/02/2016] [Indexed: 12/25/2022]
Abstract
Retromer is an evolutionarily conserved multimeric protein complex that mediates intracellular transport of various vesicular cargoes and functions in a wide variety of cellular processes including polarized trafficking, developmental signaling and lysosome biogenesis. Through its interaction with the Rab GTPases and their effectors, membrane lipids, molecular motors, the endocytic machinery and actin nucleation promoting factors, retromer regulates sorting and trafficking of transmembrane proteins from endosomes to the trans-Golgi network (TGN) and the plasma membrane. In this review, I highlight recent progress in the understanding of retromer-mediated protein sorting and vesicle trafficking and discuss how retromer contributes to a diverse set of developmental, physiological and pathological processes.
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Affiliation(s)
- Jia-Jia Liu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Beijing 100101, China.
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27
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Li C, Shah SZA, Zhao D, Yang L. Role of the Retromer Complex in Neurodegenerative Diseases. Front Aging Neurosci 2016; 8:42. [PMID: 26973516 PMCID: PMC4772447 DOI: 10.3389/fnagi.2016.00042] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 02/15/2016] [Indexed: 11/13/2022] Open
Abstract
The retromer complex is a protein complex that plays a central role in endosomal trafficking. Retromer dysfunction has been linked to a growing number of neurological disorders. The process of intracellular trafficking and recycling is crucial for maintaining normal intracellular homeostasis, which is partly achieved through the activity of the retromer complex. The retromer complex plays a primary role in sorting endosomal cargo back to the cell surface for reuse, to the trans-Golgi network (TGN), or alternatively to specialized endomembrane compartments, in which the cargo is not subjected to lysosomal-mediated degradation. In most cases, the retromer acts as a core that interacts with associated proteins, including sorting nexin family member 27 (SNX27), members of the vacuolar protein sorting 10 (VPS10) receptor family, the major endosomal actin polymerization-promoting complex known as Wiskott-Aldrich syndrome protein and scar homolog (WASH), and other proteins. Some of the molecules carried by the retromer complex are risk factors for neurodegenerative diseases. Defects such as haplo-insufficiency or mutations in one or several units of the retromer complex lead to various pathologies. Here, we summarize the molecular architecture of the retromer complex and the roles of this system in intracellular trafficking related the pathogenesis of neurodegenerative diseases.
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Affiliation(s)
- Chaosi Li
- National Animal Transmissible Spongiform Encephalopathy Laboratory, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University Beijing, China
| | - Syed Zahid Ali Shah
- National Animal Transmissible Spongiform Encephalopathy Laboratory, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University Beijing, China
| | - Deming Zhao
- National Animal Transmissible Spongiform Encephalopathy Laboratory, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University Beijing, China
| | - Lifeng Yang
- National Animal Transmissible Spongiform Encephalopathy Laboratory, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University Beijing, China
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28
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Selyunin AS, Mukhopadhyay S. A Conserved Structural Motif Mediates Retrograde Trafficking of Shiga Toxin Types 1 and 2. Traffic 2015; 16:1270-87. [PMID: 26420131 DOI: 10.1111/tra.12338] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 09/15/2015] [Accepted: 09/15/2015] [Indexed: 12/20/2022]
Abstract
Shiga toxin-producing Escherichia coli (STEC) produce two types of Shiga toxin (STx): STx1 and STx2. The toxin A-subunits block protein synthesis, while the B-subunits mediate retrograde trafficking. STEC infections do not have definitive treatments, and there is growing interest in generating toxin transport inhibitors for therapy. However, a comprehensive understanding of the mechanisms of toxin trafficking is essential for drug development. While STx2 is more toxic in vivo, prior studies focused on STx1 B-subunit (STx1B) trafficking. Here, we show that, compared with STx1B, trafficking of the B-subunit of STx2 (STx2B) to the Golgi occurs with slower kinetics. Despite this difference, similar to STx1B, endosome-to-Golgi transport of STx2B does not involve transit through degradative late endosomes and is dependent on dynamin II, epsinR, retromer and syntaxin5. Importantly, additional experiments show that a surface-exposed loop in STx2B (β4-β5 loop) is required for its endosome-to-Golgi trafficking. We previously demonstrated that residues in the corresponding β4-β5 loop of STx1B are required for interaction with GPP130, the STx1B-specific endosomal receptor, and for endosome-to-Golgi transport. Overall, STx1B and STx2B share a common pathway and use a similar structural motif to traffic to the Golgi, suggesting that the underlying mechanisms of endosomal sorting may be evolutionarily conserved.
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Affiliation(s)
- Andrey S Selyunin
- Division of Pharmacology & Toxicology, College of Pharmacy; Institute for Cellular & Molecular Biology, Institute for Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA
| | - Somshuvra Mukhopadhyay
- Division of Pharmacology & Toxicology, College of Pharmacy; Institute for Cellular & Molecular Biology, Institute for Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA
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29
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Abstract
Retrograde transport from the endosome to the Golgi is mediated by a 5 protein complex known as the retromer. These five proteins (Vps5, Vps17, Vps26, Vps29, and Vps35 in yeast and SNX1/2, SNX5/6, Vps26, Vps29, and Vps35 in mammalian cells) act as a coat for vesicles budding off of the endosome, as well as perform cargo sorting at the endosome. The retromer is well conserved between yeast and mammalian systems, though variations exist within the mammalian retromer. Functionally, the retromer has been linked to prominent neurodegenerative diseases such as Alzheimer's and Parkinson's in human models as well as diabetes mellitus. However, the retromer also plays a role in the virulence of several microbial pathogens. Despite the current understanding of the retromer complex, there are still many questions to be answered in regards to its overall role in cell homeostasis.
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Affiliation(s)
- Christopher Trousdale
- Department of Biology, Missouri State University, 901 S National, Springfield, MO 65807, United States
| | - Kyoungtae Kim
- Department of Biology, Missouri State University, 901 S National, Springfield, MO 65807, United States.
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Geldanamycin Enhances Retrograde Transport of Shiga Toxin in HEp-2 Cells. PLoS One 2015; 10:e0129214. [PMID: 26017782 PMCID: PMC4445914 DOI: 10.1371/journal.pone.0129214] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 05/06/2015] [Indexed: 12/22/2022] Open
Abstract
The heat shock protein 90 (Hsp90) inhibitor geldanamycin (GA) has been shown to alter endosomal sorting, diverting cargo destined for the recycling pathway into the lysosomal pathway. Here we investigated whether GA also affects the sorting of cargo into the retrograde pathway from endosomes to the Golgi apparatus. As a model cargo we used the bacterial toxin Shiga toxin, which exploits the retrograde pathway as an entry route to the cytosol. Indeed, GA treatment of HEp-2 cells strongly increased the Shiga toxin transport to the Golgi apparatus. The enhanced Golgi transport was not due to increased endocytic uptake of the toxin or perturbed recycling, suggesting that GA selectively enhances endosomal sorting into the retrograde pathway. Moreover, GA activated p38 and both inhibitors of p38 or its substrate MK2 partially counteracted the GA-induced increase in Shiga toxin transport. Thus, our data suggest that GA-induced p38 and MK2 activation participate in the increased Shiga toxin transport to the Golgi apparatus.
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31
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Bergan J, Skotland T, Lingelem ABD, Simm R, Spilsberg B, Lindbäck T, Sylvänne T, Simolin H, Ekroos K, Sandvig K. The ether lipid precursor hexadecylglycerol protects against Shiga toxins. Cell Mol Life Sci 2014; 71:4285-300. [PMID: 24740796 PMCID: PMC11113769 DOI: 10.1007/s00018-014-1624-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 03/12/2014] [Accepted: 04/01/2014] [Indexed: 11/24/2022]
Abstract
Shiga toxin-producing Escherichia coli bacteria cause hemorrhagic colitis and hemolytic uremic syndrome in humans. Currently, only supportive treatment is available for diagnosed patients. We show here that 24-h pretreatment with an ether lipid precursor, the alkylglycerol sn-1-O-hexadecylglycerol (HG), protects HEp-2 cells against Shiga toxin and Shiga toxin 2. Also the endothelial cell lines HMEC-1 and HBMEC are protected against Shiga toxins after HG pretreatment. In contrast, the corresponding acylglycerol, DL-α-palmitin, has no effect on Shiga toxicity. Although HG treatment provides a strong protection (~30 times higher IC₅₀) against Shiga toxin, only a moderate reduction in toxin binding was observed, suggesting that retrograde transport of the toxin from the plasma membrane to the cytosol is perturbed. Furthermore, endocytosis of Shiga toxin and retrograde sorting from endosomes to the Golgi apparatus remain intact, but transport from the Golgi to the endoplasmic reticulum is inhibited by HG treatment. As previously described, HG reduces the total level of all quantified glycosphingolipids to 50-70% of control, including the Shiga toxin receptor globotriaosylceramide (Gb3), in HEp-2 cells. In accordance with this, we find that interfering with Gb3 biosynthesis by siRNA-mediated knockdown of Gb3 synthase for 24 h causes a similar cytotoxic protection and only a moderate reduction in toxin binding (to 70% of control cells). Alkylglycerols, including HG, have been administered to humans for investigation of therapeutic roles in disorders where ether lipid biosynthesis is deficient, as well as in cancer therapy. Further studies may reveal if HG can also have a therapeutic potential in Shiga toxin-producing E. coli infections.
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Affiliation(s)
- Jonas Bergan
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway
| | - Tore Skotland
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway
| | - Anne Berit Dyve Lingelem
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway
| | - Roger Simm
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway
| | - Bjørn Spilsberg
- Section of Bacteriology-Food and GMO, Norwegian Veterinary Institute, Oslo, Norway
| | - Toril Lindbäck
- Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Oslo, Norway
| | | | | | | | - Kirsten Sandvig
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway
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Yamasaki T, Suzuki A, Hasebe R, Horiuchi M. Comparison of the anti-prion mechanism of four different anti-prion compounds, anti-PrP monoclonal antibody 44B1, pentosan polysulfate, chlorpromazine, and U18666A, in prion-infected mouse neuroblastoma cells. PLoS One 2014; 9:e106516. [PMID: 25181483 PMCID: PMC4152300 DOI: 10.1371/journal.pone.0106516] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 08/04/2014] [Indexed: 01/07/2023] Open
Abstract
Molecules that inhibit the formation of an abnormal isoform of prion protein (PrPSc) in prion-infected cells are candidate therapeutic agents for prion diseases. Understanding how these molecules inhibit PrPSc formation provides logical basis for proper evaluation of their therapeutic potential. In this study, we extensively analyzed the effects of the anti-PrP monoclonal antibody (mAb) 44B1, pentosan polysulfate (PPS), chlorpromazine (CPZ) and U18666A on the intracellular dynamics of a cellular isoform of prion protein (PrPC) and PrPSc in prion-infected mouse neuroblastoma cells to re-evaluate the effects of those agents. MAb 44B1 and PPS rapidly reduced PrPSc levels without altering intracellular distribution of PrPSc. PPS did not change the distribution and levels of PrPC, whereas mAb 44B1 appeared to inhibit the trafficking of cell surface PrPC to organelles in the endocytic-recycling pathway that are thought to be one of the sites for PrPSc formation. In contrast, CPZ and U18666A initiated the redistribution of PrPSc from organelles in the endocytic-recycling pathway to late endosomes/lysosomes without apparent changes in the distribution of PrPC. The inhibition of lysosomal function by monensin or bafilomycin A1 after the occurrence of PrPSc redistribution by CPZ or U18666A partly antagonized PrPSc degradation, suggesting that the transfer of PrPSc to late endosomes/lysosomes, possibly via alteration of the membrane trafficking machinery of cells, leads to PrPSc degradation. This study revealed that precise analysis of the intracellular dynamics of PrPC and PrPSc provides important information for understanding the mechanism of anti-prion agents.
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Affiliation(s)
- Takeshi Yamasaki
- Laboratory of Veterinary Hygiene, Graduate School of Veterinary Medicine, Hokkaido University, Kita-ku, Sapporo, Japan
| | - Akio Suzuki
- Laboratory of Veterinary Hygiene, Graduate School of Veterinary Medicine, Hokkaido University, Kita-ku, Sapporo, Japan
| | - Rie Hasebe
- Laboratory of Veterinary Hygiene, Graduate School of Veterinary Medicine, Hokkaido University, Kita-ku, Sapporo, Japan
| | - Motohiro Horiuchi
- Laboratory of Veterinary Hygiene, Graduate School of Veterinary Medicine, Hokkaido University, Kita-ku, Sapporo, Japan
- * E-mail:
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Kerr M, Teasdale RD. Live imaging of endosome dynamics. Semin Cell Dev Biol 2014; 31:11-9. [PMID: 24704360 DOI: 10.1016/j.semcdb.2014.03.027] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 03/21/2014] [Accepted: 03/25/2014] [Indexed: 11/26/2022]
Abstract
When studying the living endosome one must first recognise that we are not studying a single discrete organelle but rather a highly dynamic interconnected network of membrane-bound compartments. Endocytosed molecules are sorted and transported through various polymorphic intracellular organelles that mature and interact with one another via fusion and fission events in a highly spatially and temporally co-ordinated manner. As such, we recognise that being a dynamic system, it must be studied in a dynamic fashion. Videomicroscopy has provided profound insights into the cell, and its use in the study of the living endosome has exemplified this supplying a unique perspective on this elusive organelle. In this review we will examine some of the seminal observations that this technology has contributed as well as survey the various assays, tools and technologies that can be applied to understanding the living endosome.
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Affiliation(s)
- Markus Kerr
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia.
| | - Rohan D Teasdale
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, Australia
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Kavaliauskiene S, Nymark CM, Bergan J, Simm R, Sylvänne T, Simolin H, Ekroos K, Skotland T, Sandvig K. Cell density-induced changes in lipid composition and intracellular trafficking. Cell Mol Life Sci 2014; 71:1097-116. [PMID: 23921715 PMCID: PMC11113877 DOI: 10.1007/s00018-013-1441-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 07/24/2013] [Accepted: 07/25/2013] [Indexed: 12/11/2022]
Abstract
Cell density is one of the extrinsic factors to which cells adapt their physiology when grown in culture. However, little is known about the molecular changes which occur during cell growth and how cellular responses are then modulated. In many cases, inhibitors, drugs or growth factors used for in vitro studies change the rate of cell proliferation, resulting in different cell densities in control and treated samples. Therefore, for a comprehensive data analysis, it is essential to understand the implications of cell density on the molecular level. In this study, we have investigated how lipid composition changes during cell growth, and the consequences it has for transport of Shiga toxin. By quantifying 308 individual lipid species from 17 different lipid classes, we have found that the levels and species distribution of several lipids change during cell growth, with the major changes observed for diacylglycerols, phosphatidic acids, cholesterol esters, and lysophosphatidylethanolamines. In addition, there is a reduced binding and retrograde transport of Shiga toxin in high density cells which lead to reduced intoxication by the toxin. In conclusion, our data provide novel information on how lipid composition changes during cell growth in culture, and how these changes can modulate intracellular trafficking.
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Affiliation(s)
- Simona Kavaliauskiene
- Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, Montebello, 0379 Oslo, Norway
- Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Carl-Martin Nymark
- Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, Montebello, 0379 Oslo, Norway
- Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway
| | - Jonas Bergan
- Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, Montebello, 0379 Oslo, Norway
- Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Roger Simm
- Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, Montebello, 0379 Oslo, Norway
- Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway
| | | | | | | | - Tore Skotland
- Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, Montebello, 0379 Oslo, Norway
- Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway
| | - Kirsten Sandvig
- Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, The Norwegian Radium Hospital, Montebello, 0379 Oslo, Norway
- Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway
- Department of Biosciences, University of Oslo, Oslo, Norway
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Abstract
The endosomal network comprises an interconnected network of membranous compartments whose primary function is to receive, dissociate, and sort cargo that originates from the plasma membrane and the biosynthetic pathway. A major challenge in cell biology is to achieve a thorough molecular description of how this network operates, and in so doing, how defects contribute to the etiology and pathology of human disease. We discuss the increasing body of evidence that implicates an ancient evolutionary conserved complex, termed "retromer," as a master conductor in the complex orchestration of multiple cargo-sorting events within the endosomal network.
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Affiliation(s)
- Christopher Burd
- Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520
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36
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Sandvig K, Bergan J, Kavaliauskiene S, Skotland T. Lipid requirements for entry of protein toxins into cells. Prog Lipid Res 2014; 54:1-13. [PMID: 24462587 DOI: 10.1016/j.plipres.2014.01.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 01/15/2014] [Accepted: 01/15/2014] [Indexed: 01/05/2023]
Abstract
The plant toxin ricin and the bacterial toxin Shiga toxin both belong to a group of protein toxins having one moiety that binds to the cell surface, and another, enzymatically active moiety, that enters the cytosol and inhibits protein synthesis by inactivating ribosomes. Both toxins travel all the way from the cell surface to endosomes, the Golgi apparatus and the ER before the ribosome-inactivating moiety enters the cytosol. Shiga toxin binds to the neutral glycosphingolipid Gb3 at the cell surface and is therefore dependent on this lipid for transport into the cells, whereas ricin binds both glycoproteins and glycolipids with terminal galactose. The different steps of transport used by these toxins have specific requirements for lipid species, and with the recent developments in mass spectrometry analysis of lipids and microscopical and biochemical dissection of transport in cells, we are starting to see the complexity of endocytosis and intracellular transport. In this article we describe lipid requirements and the consequences of lipid changes for the entry and intoxication with ricin and Shiga toxin. These toxins can be a threat to human health, but can also be exploited for diagnosis and therapy, and have proven valuable as tools to study intracellular transport.
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Affiliation(s)
- Kirsten Sandvig
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway; Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Department of Biosciences, University of Oslo, Oslo, Norway.
| | - Jonas Bergan
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway; Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
| | - Simona Kavaliauskiene
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway; Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Department of Biosciences, University of Oslo, Oslo, Norway.
| | - Tore Skotland
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway; Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
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37
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Breusegem SY, Seaman MN. Image-Based and Biochemical Assays to Investigate Endosomal Protein Sorting. Methods Enzymol 2014; 534:155-78. [DOI: 10.1016/b978-0-12-397926-1.00009-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
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38
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Opazo F. Probing Biological Samples in High-Resolution Microscopy: Making Sense of Spots. NEUROMETHODS 2014. [DOI: 10.1007/978-1-62703-983-3_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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39
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Smith CJ, McGlade CJ. The ubiquitin ligase RNF126 regulates the retrograde sorting of the cation-independent mannose 6-phosphate receptor. Exp Cell Res 2013; 320:219-32. [PMID: 24275455 DOI: 10.1016/j.yexcr.2013.11.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 11/13/2013] [Accepted: 11/15/2013] [Indexed: 11/15/2022]
Abstract
The ubiquitin proteasome system is central to the regulation of a number of intracellular sorting pathways in mammalian cells including quality control at the endoplasmic reticulum and the internalization and endosomal sorting of cell surface receptors. Here we describe that RNF126, an E3 ubiquitin ligase, is involved in the sorting of the cation-independent mannose 6-phosphate receptor (CI-MPR). In cells transiently depleted of RNF126, the CI-MPR is dispersed into Rab4 positive endosomes and the efficiency of retrograde sorting is delayed. Furthermore, the stable knockdown of RNF126 leads to the lysosomal degradation of CI-MPR and missorting of cathepsin D. RNF126 specifically regulates the sorting of the CI-MPR as other cargo that follow the retrograde sorting route including the cholera toxin, furin and TGN38 are unaffected in the absence of RNF126. Lastly we show that the RING finger domain of RNF126 is required to rescue the decrease in CI-MPR levels, suggesting that the ubiquitin ligase activity of RNF126 is required for CI-MPR sorting. Together, our data indicate that the ubiquitin ligase RNF126 has a role in the retrograde sorting of the CI-MPR.
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Affiliation(s)
| | - C Jane McGlade
- Department of Medical Biophysics, University of Toronto, Canada; The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, 686 Bay Street 17-9706, Toronto, Ontario, Canada M5G 0A4.
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40
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Sandvig K, Skotland T, van Deurs B, Klokk TI. Retrograde transport of protein toxins through the Golgi apparatus. Histochem Cell Biol 2013; 140:317-26. [PMID: 23765164 DOI: 10.1007/s00418-013-1111-z] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/01/2013] [Indexed: 12/13/2022]
Abstract
A number of protein toxins from plants and bacteria take advantage of transport through the Golgi apparatus to gain entry into the cytosol where they exert their action. These toxins include the plant toxin ricin, the bacterial Shiga toxins, and cholera toxin. Such toxins bind to lipids or proteins at the cell surface, and they are endocytosed both by clathrin-dependent and clathrin-independent mechanisms. Sorting to the Golgi and retrograde transport to the endoplasmic reticulum (ER) are common to these toxins, but the exact mechanisms turn out to be toxin and cell-type dependent. In the ER, the enzymatically active part is released and then transported into the cytosol, exploiting components of the ER-associated degradation system. In this review, we will discuss transport of different protein toxins, but we will focus on factors involved in entry and sorting of ricin and Shiga toxin into and through the Golgi apparatus.
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Affiliation(s)
- Kirsten Sandvig
- Centre for Cancer Biomedicine, University of Oslo, Oslo, Norway.
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41
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Chua RYR, Wong SH. SNX3 recruits to phagosomes and negatively regulates phagocytosis in dendritic cells. Immunology 2013; 139:30-47. [PMID: 23237080 DOI: 10.1111/imm.12051] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2012] [Revised: 12/10/2012] [Accepted: 12/10/2012] [Indexed: 12/11/2022] Open
Abstract
Phagocytes such as dendritic cells (DC) and macrophages employ phagocytosis to take up pathogenic bacteria into phagosomes, digest the bacteria and present the bacteria-derived peptide antigens to the adaptive immunity. Hence, efficient antigen presentation depends greatly on a well-regulated phagocytosis process. Lipids, particularly phosphoinositides, are critical components of the phagosomes. Phosphatidylinositol-3,4,5-triphosphate [PI(3,4,5)P3 ] is formed at the phagocytic cup, and as the phagosome seals off from the plasma membrane, rapid disappearance of PI(3,4,5)P3 is accompanied by high levels of phosphatidylinositol-3-phosphate (PI3P) formation. The sorting nexin (SNX) family consists of a diverse group of Phox-homology (PX) domain-containing cytoplasmic and membrane-associated proteins that are potential effectors of phosphoinositides. We hypothesized that SNX3, a small sorting nexin that contains a single PI3P lipid-binding PX domain as its only protein domain, localizes to phagosomes and regulates phagocytosis in DC. Our results show that SNX3 recruits to nascent phagosomes and silencing of SNX3 enhances phagocytic uptake of bacteria by DC. Furthermore, SNX3 competes with PI3P lipid-binding protein, early endosome antigen-1 (EEA1) recruiting to membranes. Our results indicate that SNX3 negatively regulates phagocytosis in DC possibly by modulating recruitment of essential PI3P lipid-binding proteins of the phagocytic pathways, such as EEA1, to phagosomal membranes.
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Affiliation(s)
- Rong Yuan Ray Chua
- Laboratory of Membrane Trafficking and Immunoregulation, Department of Microbiology, Immunology Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Kvalvaag AS, Pust S, Sundet KI, Engedal N, Simm R, Sandvig K. The ERM proteins ezrin and moesin regulate retrograde Shiga toxin transport. Traffic 2013; 14:839-52. [PMID: 23593995 DOI: 10.1111/tra.12077] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 04/12/2013] [Accepted: 04/17/2013] [Indexed: 01/23/2023]
Abstract
The ERM proteins (ezrin, radixin and moesin) are known for connecting the actin cytoskeleton to the plasma membrane. They have been found to associate with lipid rafts as well as to be important for endosomal sorting and receptor signaling. However, little is known about the role of ERM proteins in retrograde transport and lipid homeostasis. In this study, we show that ezrin and moesin are important for efficient cell surface association of Shiga toxin (Stx) as well as for its retrograde transport. Furthermore, we show that depletion of these proteins influences endosomal dynamics and seems to enhance Stx transport toward lysosomes. We also show that knockdown of Vps11, a subunit of the HOPS complex, leads to increased retrograde Stx transport and reverses the inhibiting effect of ezrin and moesin knockdown. Importantly, retrograde transport of the plant toxin ricin, which binds to both glycolipids and glycoproteins with a terminal galactose, seems to be unaffected by ezrin and moesin depletion.
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Affiliation(s)
- Audun Sverre Kvalvaag
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, N-0379, Oslo, Norway
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43
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Mukhopadhyay S, Linstedt AD. Retrograde trafficking of AB₅ toxins: mechanisms to therapeutics. J Mol Med (Berl) 2013; 91:1131-41. [PMID: 23665994 DOI: 10.1007/s00109-013-1048-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 04/23/2013] [Accepted: 04/24/2013] [Indexed: 01/28/2023]
Abstract
Bacterial AB5 toxins are a clinically relevant class of exotoxins that include several well-known members such as Shiga, cholera, and pertussis toxins. Infections with toxin-producing bacteria cause devastating human diseases that affect millions of individuals each year and have no definitive medical treatment. The molecular targets of AB5 toxins reside in the cytosol of infected cells, and the toxins reach the cytosol by trafficking through the retrograde membrane transport pathway that avoids degradative late endosomes and lysosomes. Focusing on Shiga toxin as the archetype member, we review recent advances in understanding the molecular mechanisms involved in the retrograde trafficking of AB5 toxins and highlight how these basic science advances are leading to the development of a promising new therapeutic approach based on inhibiting toxin transport.
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Affiliation(s)
- Somshuvra Mukhopadhyay
- Division of Pharmacology & Toxicology, College of Pharmacy and Institute for Cellular & Molecular Biology, The University of Texas at Austin, Austin, TX, 78712, USA
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44
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Raiborg C, Schink KO, Stenmark H. Class III phosphatidylinositol 3-kinase and its catalytic product PtdIns3P in regulation of endocytic membrane traffic. FEBS J 2013; 280:2730-42. [PMID: 23289851 DOI: 10.1111/febs.12116] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Revised: 12/20/2012] [Accepted: 12/24/2012] [Indexed: 01/01/2023]
Abstract
Endocytosis and subsequent membrane traffic through endosomes are cellular processes that are integral to eukaryotic evolution, and numerous human diseases are associated with their dysfunction. Consequently, it is important to untangle the molecular machineries that regulate membrane dynamics and protein flow in the endocytic pathway. Central in this context is class III phosphatidylinositol 3-kinase, an evolutionarily conserved enzyme complex that phosphorylates phosphatidylinositol into phosphatidylinositol 3-phosphate. Phosphatidylinositol 3-phosphate recruits specific effector proteins, most of which contain FYVE or PX domains, to promote endocytosis, endosome fusion, endosome motility and endosome maturation, as well as cargo sorting to lysosomes, the biosynthetic pathway or the plasma membrane. Here we review the functions of key phosphatidylinositol 3-phosphate effectors in regulation of endocytic membrane dynamics and protein sorting.
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Affiliation(s)
- Camilla Raiborg
- Centre for Cancer Biomedicine, Faculty of Medicine, Oslo University Hospital, Montebello, Norway
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45
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McGough IJ, Cullen PJ. Clathrin is not required for SNX-BAR-retromer-mediated carrier formation. J Cell Sci 2013; 126:45-52. [PMID: 23015596 PMCID: PMC3603510 DOI: 10.1242/jcs.112904] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/10/2012] [Indexed: 02/03/2023] Open
Abstract
Clathrin has been implicated in retromer-mediated trafficking, but its precise function remains elusive. Given the importance of retromers for efficient endosomal sorting, we have sought to clarify the relationship between clathrin and the SNX-BAR retromer. We find that the retromer SNX-BARs do not interact directly or indirectly with clathrin. In addition, we observe that SNX-BAR-retromer tubules and carriers are not clathrin coated. Furthermore, perturbing clathrin function, by overexpressing a dominant-negative clathrin or through suppression of clathrin expression, has no detectable effect on the frequency of SNX-BAR-retromer tubulation. We propose that SNX-BAR-retromer-mediated membrane deformation and carrier formation does not require clathrin, and hence the role of clathrin in SNX-BAR-retromer function would appear to lie in pre-SNX-BAR-retromer cargo sorting.
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Affiliation(s)
| | - Peter J. Cullen
- Henry Wellcome Integrated Signalling Laboratories, School of Biochemistry, Medical Sciences Building, University Walk, University of Bristol, Bristol BS8 1TD, UK
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Khan AR. Oligomerization of rab/effector complexes in the regulation of vesicle trafficking. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 117:579-614. [PMID: 23663983 DOI: 10.1016/b978-0-12-386931-9.00021-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Rabs comprise the largest member of the Ras superfamily of small GTPases with over 60 proteins in mammals and 11 proteins in yeast. Like all small GTPases, Rabs oscillate between an inactive GDP-bound conformation and an active GTP-bound state that is tethered to lipid membranes via a C-terminal prenylation site on conserved cysteine residues. In their active state, Rabs regulate various aspects of membrane trafficking, including vesicle formation, transport, docking, and fusion. The critical element of biological activity is the recruitment of cytosolic effector proteins to specific endomembranes by active Rabs. The importance of Rabs in cellular processes is apparent from their links to genetic disorders, immunodeficiency, cancer, and pathogen invasion. During the last decade, numerous structures of complexes have shed light on the molecular basis for Rab/effector specificity and their topological organization on subcellular membranes. Here, I review the known structures of Rab/effector complexes and their modes of oligomerization. This is followed by a brief discussion on the thermodynamics of effector recruitment, which has not been documented sufficiently in previous reviews. A summary of diseases associated with Rab/effector trafficking pathways concludes this chapter.
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Affiliation(s)
- Amir R Khan
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
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Abstract
The retromer complex is a vital element of the endosomal protein sorting machinery that is conserved across all eukaryotes. Retromer is most closely associated with the endosome-to-Golgi retrieval pathway and is necessary to maintain an active pool of hydrolase receptors in the trans-Golgi network. Recent progress in studies of retromer have identified new retromer-interacting proteins, including the WASH complex and cargo such as the Wntless/MIG-14 protein, which now extends the role of retromer beyond the endosome-to-Golgi pathway and has revealed that retromer is required for aspects of endosome-to-plasma membrane sorting and regulation of signalling events. The interactions between the retromer complex and other macromolecular protein complexes now show how endosomal protein sorting is coordinated with actin assembly and movement along microtubules, and place retromer squarely at the centre of a complex set of protein machinery that governs endosomal protein sorting. Dysregulation of retromer-mediated endosomal protein sorting leads to various pathologies, including neurodegenerative diseases such as Alzheimer disease and spastic paraplegia and the mechanisms underlying these pathologies are starting to be understood. In this Commentary, I will highlight recent advances in the understanding of retromer-mediated endosomal protein sorting and discuss how retromer contributes to a diverse set of physiological processes.
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Molecular basis for SNX-BAR-mediated assembly of distinct endosomal sorting tubules. EMBO J 2012; 31:4466-80. [PMID: 23085988 PMCID: PMC3512392 DOI: 10.1038/emboj.2012.283] [Citation(s) in RCA: 151] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 09/25/2012] [Indexed: 12/23/2022] Open
Abstract
A systematic analysis of the dimerization, membrane remodelling and higher order assembly properties of all 12 human SNX-BAR sorting nexins reveals how different SNX-BAR combinations allow the formation of distinct tubular subdomains from the same endosomal vacuole during cargo sorting. Sorting nexins (SNXs) are regulators of endosomal sorting. For the SNX-BAR subgroup, a Bin/Amphiphysin/Rvs (BAR) domain is vital for formation/stabilization of tubular subdomains that mediate cargo recycling. Here, by analysing the in vitro membrane remodelling properties of all 12 human SNX-BARs, we report that some, but not all, can elicit the formation of tubules with diameters that resemble sorting tubules observed in cells. We reveal that SNX-BARs display a restricted pattern of BAR domain-mediated dimerization, and by resolving a 2.8 Å structure of a SNX1-BAR domain homodimer, establish that dimerization is achieved in part through neutralization of charged residues in the hydrophobic BAR-dimerization interface. Membrane remodelling also requires functional amphipathic helices, predicted to be present in all SNX-BARs, and the formation of high order SNX-BAR oligomers through selective ‘tip–loop' interactions. Overall, the restricted and selective nature of these interactions provide a molecular explanation for how distinct SNX-BAR-decorated tubules are nucleated from the same endosomal vacuole, as observed in living cells. Our data provide insight into the molecular mechanism that generates and organizes the tubular endosomal network.
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Bergan J, Dyve Lingelem AB, Simm R, Skotland T, Sandvig K. Shiga toxins. Toxicon 2012; 60:1085-107. [PMID: 22960449 DOI: 10.1016/j.toxicon.2012.07.016] [Citation(s) in RCA: 148] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 06/19/2012] [Accepted: 07/25/2012] [Indexed: 02/03/2023]
Abstract
Shiga toxins are virulence factors produced by the bacteria Shigella dysenteriae and certain strains of Escherichia coli. There is currently no available treatment for disease caused by these toxin-producing bacteria, and understanding the biology of the Shiga toxins might be instrumental in addressing this issue. In target cells, the toxins efficiently inhibit protein synthesis by inactivating ribosomes, and they may induce signaling leading to apoptosis. To reach their cytoplasmic target, Shiga toxins are endocytosed and transported by a retrograde pathway to the endoplasmic reticulum, before the enzymatically active moiety is translocated to the cytosol. The toxins thereby serve as powerful tools to investigate mechanisms of intracellular transport. Although Shiga toxins are a serious threat to human health, the toxins may be exploited for medical purposes such as cancer therapy or imaging.
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Affiliation(s)
- Jonas Bergan
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway
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Annexin A1 and A2: roles in retrograde trafficking of Shiga toxin. PLoS One 2012; 7:e40429. [PMID: 22792315 PMCID: PMC3391278 DOI: 10.1371/journal.pone.0040429] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Accepted: 06/06/2012] [Indexed: 01/05/2023] Open
Abstract
Annexins constitute a family of calcium and membrane binding proteins. As annexin A1 and A2 have previously been linked to various membrane trafficking events, we initiated this study to investigate the role of these annexins in the uptake and intracellular transport of the bacterial Shiga toxin (Stx) and the plant toxin ricin. Once endocytosed, both toxins are retrogradely transported from endosomes to the Golgi apparatus and the endoplasmic reticulum before being targeted to the cytosol where they inhibit protein synthesis. This study was performed to obtain new information both about toxin transport and the function of annexin A1 and annexin A2. Our data show that depletion of annexin A1 or A2 alters the retrograde transport of Stx but not ricin, without affecting toxin binding or internalization. Knockdown of annexin A1 increases Golgi transport of Stx, whereas knockdown of annexin A2 slightly decreases the same transport step. Interestingly, annexin A1 was found in proximity to cytoplasmic phospholipase A2 (cPLA2), and the basal as well as the increased Golgi transport of Stx upon annexin A1 knockdown is dependent on cPLA2 activity. In conclusion, annexin A1 and A2 have different roles in Stx transport to the trans-Golgi network. The most prominent role is played by annexin A1 which normally works as a negative regulator of retrograde transport from the endosomes to the Golgi network, most likely by complex formation and inhibition of cPLA2.
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