1
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Tucker SK, McHugh RE, Roe AJ. One problem, multiple potential targets: Where are we now in the development of small molecule inhibitors against Shiga toxin? Cell Signal 2024; 121:111253. [PMID: 38852937 DOI: 10.1016/j.cellsig.2024.111253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2024] [Revised: 06/04/2024] [Accepted: 06/06/2024] [Indexed: 06/11/2024]
Abstract
Shiga toxin-producing Escherichia coli (STEC) are a group of enteric pathogens which carry phage-encoded Shiga toxins (Stx). STEC infections begin with severe abdominal pain and non-bloody diarrhoea, which can progress to bloody diarrhoea after approximately 4-days post-infection. In high-risk groups such as children and the elderly, patients may develop haemolytic uremic syndrome (HUS). HUS is characterised by microangiopathic haemolytic anaemia, thrombocytopenia, and in severe disease acute renal failure. Traditional antibiotics have been linked with increased toxin production due to the activation of recA-mediated bacterial stress response, resulting in poorer patient outcomes. Therefore, treatment relies on supportive therapies. Antivirulence strategies have been explored as an alternative treatment for bacterial infections and blockers of virulence factors such as the Type III Secretion System. Recent improvements in the mechanistic understanding of the Stx pathway have led to the design of inhibitors to disrupt the pathway, leading to toxin-mediated ribosome damage. However, compounds have yet to progress beyond Phase III clinical trials successfully. This review explores the progress in developing small molecule inhibitors by collating lead compounds derived from in-silico and experimental approaches.
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Affiliation(s)
- Samantha K Tucker
- School of Infection and Immunity, University of Glasgow, Glasgow G12 8TA, United Kingdom
| | - Rebecca E McHugh
- School of Infection and Immunity, University of Glasgow, Glasgow G12 8TA, United Kingdom
| | - Andrew J Roe
- School of Infection and Immunity, University of Glasgow, Glasgow G12 8TA, United Kingdom.
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2
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Lingwood C. Is cholesterol both the lock and key to abnormal transmembrane signals in Autism Spectrum Disorder? Lipids Health Dis 2024; 23:114. [PMID: 38643132 PMCID: PMC11032007 DOI: 10.1186/s12944-024-02075-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 03/08/2024] [Indexed: 04/22/2024] Open
Abstract
Disturbances in cholesterol homeostasis have been associated with ASD. Lipid rafts are central in many transmembrane signaling pathways (including mTOR) and changes in raft cholesterol content affect their order function. Cholesterol levels are controlled by several mechanisms, including endoplasmic reticulum associated degradation (ERAD) of the rate limiting HMGCoA reductase. A new approach to increase cholesterol via temporary ERAD blockade using a benign bacterial toxin-derived competitor for the ERAD translocon is suggested.A new lock and key model for cholesterol/lipid raft dependent signaling is proposed in which the rafts provide both the afferent and efferent 'tumblers' across the membrane to allow 'lock and key' receptor transmembrane signals.
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Affiliation(s)
- Clifford Lingwood
- Division of Molecular Medicine, Research Institute, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, M5G 0A4, Canada.
- Departments of Biochemistry and Laboratory Medicine & Pathobiology, University of Toronto, Ontario, M5S 1A8, Canada.
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3
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Chen Z, Zhang SL. Endoplasmic Reticulum Stress: A Key Regulator of Cardiovascular Disease. DNA Cell Biol 2023. [PMID: 37140435 DOI: 10.1089/dna.2022.0532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023] Open
Abstract
The problems associated with economic development and social progress have led to an increase in the occurrence of cardiovascular diseases (CVDs), which affect the health of an increasing number of people and are a leading cause of disease and population mortality worldwide. Endoplasmic reticulum stress (ERS), a hot topic of interest for scholars in recent years, has been confirmed in numerous studies to be an important pathogenetic basis for many metabolic diseases and play an important role in maintaining physiological processes. The endoplasmic reticulum (ER) is a major organelle that is involved in protein folding and modification synthesis, and ERS occurs when several physiological and pathological factors allow excessive amounts of unfolded/misfolded proteins to accumulate. ERS often leads to initiation of the unfolded protein response (UPR) in a bid to re-establish tissue homeostasis; however, UPR has been documented to induce vascular remodeling and cardiomyocyte damage under various pathological conditions, leading to or accelerating the development of CVDs such as hypertension, atherosclerosis, and heart failure. In this review, we summarize the latest knowledge gained concerning ERS in terms of cardiovascular system pathophysiology, and discuss the feasibility of targeting ERS as a novel therapeutic target for the treatment of CVDs. Investigation of ERS has immense potential as a new direction for future research involving lifestyle intervention, the use of existing drugs, and the development of novel drugs that target and inhibit ERS.
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Affiliation(s)
- Zhao Chen
- Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Shi-Liang Zhang
- Section 4, Department of Cardiology, The Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China
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4
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Jassar O, Ghanim M. Association of endoplasmic reticulum associated degradation (ERAD) with the transmission of Liberibacter solanacearum by its psyllid vector. INSECT MOLECULAR BIOLOGY 2023. [PMID: 37060303 DOI: 10.1111/imb.12842] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 04/03/2023] [Indexed: 06/19/2023]
Abstract
Candidatus Liberibacter solanacearum (CLso) is a complex of gram negative plant pathogenic and fastidious bacterial haplotypes restricted to the phloem and transmitted by several psyllid species. In Israel, the carrot psyllid Bactericera trigonica transmits CLso haplotype D in a persistent and propagative manner and causes the carrot yellows disease, inflicting significant economic losses in many countries. Understanding the transmission of CLso is fundamental to devising sustainable management strategies. Persistent transmission of vector-borne pathogens involves the critical steps of adhesion, cell invasion and replication inside the insect gut cells before passage to the hemolymph. Using microscopy and expression analyses, we have previously confirmed a role for the endoplasmic reticulum (ER) in inducing immune responses and subsequent molecular pathways resulting in programmed cell death (apoptosis) upon CLso-infection in the midgut. In the current study, we confirm that the ER-associated degradation (ERAD) machinery and its associated marker genes were upregulated in CLso infected insects, including Derlin-1, Selenoprotein-1 and Ubiquitin Ligase RNF-185. Silencing Derlin-1, which acts on the ER membrane by regulating the degradation of unfolded proteins upon ER stress, revealed its role in CLso persistence and transmission. Molecular pathways initiated in the ER membrane upon bacterial infection are well documented in human, animal and insect systems, and this study confirms the role of the ER in CLso-psyllid interactions.
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Affiliation(s)
- Ola Jassar
- Department of Entomology, Volcani Institute, Rishon Lezion, Israel
- The Robert H. Smith Faculty of Agriculture, Food & Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Murad Ghanim
- Department of Entomology, Volcani Institute, Rishon Lezion, Israel
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5
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Schäfer AB, Steenhuis M, Jim KK, Neef J, O’Keefe S, Whitehead RC, Swanton E, Wang B, Halbedel S, High S, van Dijl JM, Luirink J, Wenzel M. Dual Action of Eeyarestatin 24 on Sec-Dependent Protein Secretion and Bacterial DNA. ACS Infect Dis 2023; 9:253-269. [PMID: 36637435 PMCID: PMC9926488 DOI: 10.1021/acsinfecdis.2c00404] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Eeyarestatin 24 (ES24) is a promising new antibiotic with broad-spectrum activity. It shares structural similarity with nitrofurantoin (NFT), yet appears to have a distinct and novel mechanism: ES24 was found to inhibit SecYEG-mediated protein transport and membrane insertion in Gram-negative bacteria. However, possible additional targets have not yet been explored. Moreover, its activity was notably better against Gram-positive bacteria, for which its mechanism of action had not yet been investigated. We have used transcriptomic stress response profiling, phenotypic assays, and protein secretion analyses to investigate the mode of action of ES24 in comparison with NFT using the Gram-positive model bacterium Bacillus subtilis and have compared our findings to Gram-negative Escherichia coli. Here, we show the inhibition of Sec-dependent protein secretion in B. subtilis and additionally provide evidence for DNA damage, probably caused by the generation of reactive derivatives of ES24. Interestingly, ES24 caused a gradual dissipation of the membrane potential, which led to delocalization of cytokinetic proteins and subsequent cell elongation in E. coli. However, none of those effects were observed in B. subtilis, thereby suggesting that ES24 displays distinct mechanistic differences with respect to Gram-positive and Gram-negative bacteria. Despite its structural similarity to NFT, ES24 profoundly differed in our phenotypic analysis, which implies that it does not share the NFT mechanism of generalized macromolecule and structural damage. Importantly, ES24 outperformed NFT in vivo in a zebrafish embryo pneumococcal infection model. Our results suggest that ES24 not only inhibits the Sec translocon, but also targets bacterial DNA and, in Gram-negative bacteria, the cell membrane.
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Affiliation(s)
- Ann-Britt Schäfer
- Division
of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, 412 96 Gothenburg, Sweden
| | - Maurice Steenhuis
- Molecular
Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Kin Ki Jim
- Department
of Medical Microbiology and Infection Prevention, Amsterdam University Medical Centers - Location Vrije Universiteit
Amsterdam, 1081 HZ Amsterdam, The Netherlands,Amsterdam
Institute for Infection and Immunity, Amsterdam
University Medical Centers, 1081 HZ Amsterdam, The Netherlands
| | - Jolanda Neef
- Department
of Medical Microbiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, PO Box 30001, 9700 RB Groningen, The Netherlands
| | - Sarah O’Keefe
- School
of
Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Roger C. Whitehead
- School
of Chemistry, Faculty of Science and Engineering, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Eileithyia Swanton
- School
of
Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Biwen Wang
- Bacterial
Cell Biology and Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
| | - Sven Halbedel
- FG11
Division of Enteropathogenic Bacteria and Legionella, Robert Koch Institute, 38855 Wernigerode, Germany,Institute
for Medical Microbiology and Hospital Hygiene, Otto von Guericke University Magdeburg, 39120 Magdeburg, Germany
| | - Stephen High
- School
of
Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Jan Maarten van Dijl
- Department
of Medical Microbiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, PO Box 30001, 9700 RB Groningen, The Netherlands
| | - Joen Luirink
- Molecular
Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands,
| | - Michaela Wenzel
- Division
of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, 412 96 Gothenburg, Sweden,
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6
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Inhibitors of the Sec61 Complex and Novel High Throughput Screening Strategies to Target the Protein Translocation Pathway. Int J Mol Sci 2021; 22:ijms222112007. [PMID: 34769437 PMCID: PMC8585047 DOI: 10.3390/ijms222112007] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/25/2021] [Accepted: 10/29/2021] [Indexed: 02/08/2023] Open
Abstract
Proteins targeted to the secretory pathway start their intracellular journey by being transported across biological membranes such as the endoplasmic reticulum (ER). A central component in this protein translocation process across the ER is the Sec61 translocon complex, which is only intracellularly expressed and does not have any enzymatic activity. In addition, Sec61 translocon complexes are difficult to purify and to reconstitute. Screening for small molecule inhibitors impairing its function has thus been notoriously difficult. However, such translocation inhibitors may not only be valuable tools for cell biology, but may also represent novel anticancer drugs, given that cancer cells heavily depend on efficient protein translocation into the ER to support their fast growth. In this review, different inhibitors of protein translocation will be discussed, and their specific mode of action will be compared. In addition, recently published screening strategies for small molecule inhibitors targeting the whole SRP-Sec61 targeting/translocation pathway will be summarized. Of note, slightly modified assays may be used in the future to screen for substances affecting SecYEG, the bacterial ortholog of the Sec61 complex, in order to identify novel antibiotic drugs.
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7
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Shi Y, Zhu C, Liu Y, Lu Y, Li X, Qin B, Luo Z, Luo L, Jiang M, Zhang J, Guan G, Zheng C, You J. A Vaccination with Boosted Cross Presentation by ER-Targeted Antigen Delivery for Anti-Tumor Immunotherapy. Adv Healthc Mater 2021; 10:e2001934. [PMID: 33502831 DOI: 10.1002/adhm.202001934] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 12/17/2020] [Indexed: 12/16/2022]
Abstract
Vaccination is a widely-accepted resort against the invasion or proliferation of bacteria, parasites, viruses, and even cancer, which accounts heavily on an active involvement of CD8+ T cells. As one of the pivotal strategies taken by dendritic cells (DCs) to promote the responsiveness of CD8+ T cells to exogenous antigens, cross presentation culminates in an elevated overall host defense against cancer or infection. However, the precise mechanisms regulating such a process remains elusive, and current attempts to fuel cross presentation usually fail to exert efficiency. Here, model antigen OVA-loaded, endoplasmic reticulum (ER)-targeting cationic liposome (OVA@lipoT) is developed and characterized with a booster effect on the activation and maturation of DCs. Moreover, OVA@lipoT pulsed DCs exhibit overwhelming superiority in triggering cytotoxic T lymphocyte response both in vivo and in vitro. Data reveal that lipoT alters the intracellular trafficking and presenting pathway of antigen, which promotes cross presentation and bears close relationship to the ER-associated degradation (ERAD). These results may drop a hint about the interconnectivity between cross presentation and ER-targeted antigen delivery, provide extra information to the understanding of ERAD-mediated cross priming, and even shed new light on the design and optimization of vaccines against currently intractable cancers or virus-infection.
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Affiliation(s)
- Yingying Shi
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Chunqi Zhu
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Yu Liu
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Yichao Lu
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Xiang Li
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Bing Qin
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Zhenyu Luo
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Lihua Luo
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Mengshi Jiang
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Junlei Zhang
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Guannan Guan
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
| | - Cheng Zheng
- Zhejiang Institute for Food and Drug Control Zhejiang 310058 P. R. China
| | - Jian You
- College of Pharmaceutical Sciences Zhejiang University Zhejiang 310058 P. R. China
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8
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Steenhuis M, Koningstein GM, Oswald J, Pick T, O'Keefe S, Koch HG, Cavalié A, Whitehead RC, Swanton E, High S, Luirink J. Eeyarestatin 24 impairs SecYEG-dependent protein trafficking and inhibits growth of clinically relevant pathogens. Mol Microbiol 2020; 115:28-40. [PMID: 32798330 PMCID: PMC8273874 DOI: 10.1111/mmi.14589] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/29/2020] [Indexed: 02/06/2023]
Abstract
Eeyarestatin 1 (ES1) is an inhibitor of endoplasmic reticulum (ER) associated protein degradation, Sec61‐dependent Ca2+ homeostasis and protein translocation into the ER. Recently, evidence was presented showing that a smaller analog of ES1, ES24, targets the Sec61‐translocon, and captures it in an open conformation that is translocation‐incompetent. We now show that ES24 impairs protein secretion and membrane protein insertion in Escherichia coli via the homologous SecYEG‐translocon. Transcriptomic analysis suggested that ES24 has a complex mode of action, probably involving multiple targets. Interestingly, ES24 shows antibacterial activity toward clinically relevant strains. Furthermore, the antibacterial activity of ES24 is equivalent to or better than that of nitrofurantoin, a known antibiotic that, although structurally similar to ES24, does not interfere with SecYEG‐dependent protein trafficking. Like nitrofurantoin, we find that ES24 requires activation by the NfsA and NfsB nitroreductases, suggesting that the formation of highly reactive nitroso intermediates is essential for target inactivation in vivo.
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Affiliation(s)
- Maurice Steenhuis
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, Amsterdam, the Netherlands
| | - Gregory M Koningstein
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, Amsterdam, the Netherlands
| | - Julia Oswald
- Institute of Biochemistry and Molecular Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Tillman Pick
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, Homburg, Germany
| | - Sarah O'Keefe
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Hans-Georg Koch
- Institute of Biochemistry and Molecular Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Adolfo Cavalié
- Experimental and Clinical Pharmacology and Toxicology, Saarland University, Homburg, Germany
| | - Roger C Whitehead
- School of Chemistry, Faculty of Science and Engineering, University of Manchester, Manchester, UK
| | - Eileithyia Swanton
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Stephen High
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Joen Luirink
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, Amsterdam, the Netherlands
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9
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Pradeep Yeola A, Akbar I, Baillargeon J, Mercy Ignatius Arokia Doss P, Paavilainen VO, Rangachari M. Protein translocation and retro-translocation across the endoplasmic reticulum are crucial to inflammatory effector CD4 + T cell function. Cytokine 2020; 129:154944. [PMID: 32146280 DOI: 10.1016/j.cyto.2019.154944] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 11/22/2019] [Accepted: 11/23/2019] [Indexed: 10/24/2022]
Abstract
Effector CD4+ T cells can be classified by the cytokines they secrete, with T helper 1 (Th1) cells generating interferon (IFN)γ and Th17 cells secreting interleukin (IL)-17. Both Th1 and Th17 cells are strongly implicated in the initiation and chronicity of autoimmune diseases such as multiple sclerosis. The endoplasmic reticulum (ER) has been implicated as a potentially crucial site in regulating CD4+ T cell function. Secretory and transmembrane proteins are shuttled into the ER via the Sec61 translocon, where they undergo appropriate folding; misfolded proteins are retro-translocated from the ER in a p97-dependent manner. Here, we provide evidence that both processes are crucial to the secretion of inflammatory cytokines from effector CD4+ T cells. The pan-ER inhibitor eeeyarestatin-1 (ESI), which interferes with both Sec61 translocation and p97 retro-translocation, inhibited secretion of interferon (IFN)γ, interleukin (IL)-2 and tumor necrosis factor (TNF)α from Th1 cells in a dose-dependent manner. Selective inhibition of Sec61 by Apratoxin A (ApraA) revealed that ER translocation is crucial for Th1 cytokine secretion, while inhibition of p97 by NMS-873 also inhibited Th1 function, albeit to a lesser degree. By contrast, none of ESI, ApraA or NMS-873 could significantly reduce IL-17 secretion from Th17 cells. ApraA, but not NMS-873, reduced phosphorylation of Stat1 in Th1 cells, indicating the involvement of ER translocation in Th1 differentiation pathways. ApraA had modest effects on activation of the Th17 transcription factor Stat3, while NMS-873 had no effect. Interestingly, NMS-873 was able to reduce disease severity in CD4+ T cell-driven experimental autoimmune encephalomyelitis (EAE). Together, our data indicate that CD4+ T cell function, and Th1 cell function in particular, is dependent on protein translocation and dislocation across the ER.
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Affiliation(s)
- Asmita Pradeep Yeola
- axe Neurosciences, Centre de recherche du CHU de Québec - Université Laval, Quebec City, QC, Canada
| | - Irshad Akbar
- axe Neurosciences, Centre de recherche du CHU de Québec - Université Laval, Quebec City, QC, Canada
| | - Joanie Baillargeon
- axe Neurosciences, Centre de recherche du CHU de Québec - Université Laval, Quebec City, QC, Canada
| | | | | | - Manu Rangachari
- axe Neurosciences, Centre de recherche du CHU de Québec - Université Laval, Quebec City, QC, Canada; Department of Molecular Medicine, Faculty of Medicine, Laval University, Quebec City, QC, Canada.
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10
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Luesch H, Paavilainen VO. Natural products as modulators of eukaryotic protein secretion. Nat Prod Rep 2020; 37:717-736. [PMID: 32067014 DOI: 10.1039/c9np00066f] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Covering: up to the end of 2019Diverse natural product small molecules have allowed critical insights into processes that govern eukaryotic cells' ability to secrete cytosolically synthesized secretory proteins into their surroundings or to insert newly synthesized integral membrane proteins into the lipid bilayer of the endoplasmic reticulum. In addition, many components of the endoplasmic reticulum, required for protein homeostasis or other processes such as lipid metabolism or maintenance of calcium homeostasis, are being investigated for their potential in modulating human disease conditions such as cancer, neurodegenerative conditions and diabetes. In this review, we cover recent findings up to the end of 2019 on natural products that influence protein secretion or impact ER protein homeostasis, and serve as powerful chemical tools to understand protein flux through the mammalian secretory pathway and as leads for the discovery of new therapeutics.
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Affiliation(s)
- Hendrik Luesch
- Department of Medicinal Chemistry, Center for Natural Products, Drug Discovery and Development (CNPD3), University of Florida, P.O. Box 100485, Gainesville, Florida 32610, USA.
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11
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Eeyarestatin Compounds Selectively Enhance Sec61-Mediated Ca 2+ Leakage from the Endoplasmic Reticulum. Cell Chem Biol 2019; 26:571-583.e6. [PMID: 30799222 PMCID: PMC6483976 DOI: 10.1016/j.chembiol.2019.01.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 10/06/2018] [Accepted: 01/24/2019] [Indexed: 01/01/2023]
Abstract
Eeyarestatin 1 (ES1) inhibits p97-dependent protein degradation, Sec61-dependent protein translocation into the endoplasmic reticulum (ER), and vesicular transport within the endomembrane system. Here, we show that ES1 impairs Ca2+ homeostasis by enhancing the Ca2+ leakage from mammalian ER. A comparison of various ES1 analogs suggested that the 5-nitrofuran (5-NF) ring of ES1 is crucial for this effect. Accordingly, the analog ES24, which conserves the 5-NF domain of ES1, selectively inhibited protein translocation into the ER, displayed the highest potency on ER Ca2+ leakage of ES1 analogs studied and induced Ca2+-dependent cell death. Using small interfering RNA-mediated knockdown of Sec61α, we identified Sec61 complexes as the targets that mediate the gain of Ca2+ leakage induced by ES1 and ES24. By interacting with the lateral gate of Sec61α, ES1 and ES24 likely capture Sec61 complexes in a Ca2+-permeable, open state, in which Sec61 complexes allow Ca2+ leakage but are translocation incompetent. ES1, ES2, and ES24 deplete Ca2+ in ER ESR35 and ES47 do not affect cellular Ca2+ homeostasis The most potent eeyarestatin, ES24, comprises only the 5-nitrofuran domain ES1 and ES24 target Sec61 complexes in ER
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12
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Klein W, Rutz C, Eckhard J, Provinciael B, Specker E, Neuenschwander M, Kleinau G, Scheerer P, von Kries JP, Nazaré M, Vermeire K, Schülein R. Use of a sequential high throughput screening assay to identify novel inhibitors of the eukaryotic SRP-Sec61 targeting/translocation pathway. PLoS One 2018; 13:e0208641. [PMID: 30543669 PMCID: PMC6292634 DOI: 10.1371/journal.pone.0208641] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 11/20/2018] [Indexed: 11/22/2022] Open
Abstract
The SRP-Sec61 targeting/translocation pathway of eukaryotic cells targets nascent protein chains to the membrane of the endoplasmic reticulum. Using this machinery, secretory proteins are translocated across this membrane whereas membrane proteins are integrated into the lipid bilayer. One of the key players of the pathway is the protein-conducting Sec61 (translocon) complex of the endoplasmic reticulum. The Sec61 complex has no enzymatic activity, is expressed only intracellularly and is difficult to purify and to reconstitute. Screening for small molecule inhibitors impairing its functions is thus notoriously difficult. Such inhibitors may not only be valuable tools for cell biology, they may also represent novel anti-tumor drugs. Here we have developed a two-step, sequential screening assay for inhibitors of the whole SRP-Sec61 targeting/translocation pathway which might include molecules affecting Sec61 complex functions. The resulting hit compounds were analyzed using a whole cell biosynthesis assay and a cell free transcription/translation/translocation assay. Using this methodology, we identified novel compounds inhibiting this pathway. Following structure-based back screening, one of these substances was analyzed in more detail and we could show that it indeed impairs translocation at the level of the Sec61 complex. A slightly modified methodology may be used in the future to screen for substances affecting SecYEG, the bacterial ortholog of the Sec61 complex in order to derive novel antibiotic drugs.
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Affiliation(s)
- Wolfgang Klein
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Claudia Rutz
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Jamina Eckhard
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Becky Provinciael
- KU Leuven, Department of Microbiology and Immunology, Rega Institute, Laboratory of Virology and Chemotherapy, Leuven, Belgium
| | - Edgar Specker
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | | | - Gunnar Kleinau
- Charité—Universitätsmedizin Berlin, Campus Charité Mitte, Charité Centrum Grundlagenmedizin CC2, Institut für Medizinische Physik und Biophysik, Group Protein X-ray Crystallography & Signal Transduction, Berlin, Germany
| | - Patrick Scheerer
- Charité—Universitätsmedizin Berlin, Campus Charité Mitte, Charité Centrum Grundlagenmedizin CC2, Institut für Medizinische Physik und Biophysik, Group Protein X-ray Crystallography & Signal Transduction, Berlin, Germany
| | | | - Marc Nazaré
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Kurt Vermeire
- KU Leuven, Department of Microbiology and Immunology, Rega Institute, Laboratory of Virology and Chemotherapy, Leuven, Belgium
| | - Ralf Schülein
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
- * E-mail:
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13
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Durgeau A, Virk Y, Gros G, Voilin E, Corgnac S, Djenidi F, Salmon J, Adam J, de Montpréville V, Validire P, Ferrone S, Chouaib S, Eggermont A, Soria JC, Lemonnier F, Tartour E, Chaput N, Besse B, Mami-Chouaib F. Human preprocalcitonin self-antigen generates TAP-dependent and -independent epitopes triggering optimised T-cell responses toward immune-escaped tumours. Nat Commun 2018; 9:5097. [PMID: 30504837 PMCID: PMC6269466 DOI: 10.1038/s41467-018-07603-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 10/30/2018] [Indexed: 12/25/2022] Open
Abstract
Tumours often evade CD8 T-cell immunity by downregulating TAP. T-cell epitopes associated with impaired peptide processing are immunogenic non-mutated neoantigens that emerge during tumour immune evasion. The preprocalcitonin (ppCT)16-25 neoepitope belongs to this category of antigens. Here we show that most human lung tumours display altered expression of TAP and frequently express ppCT self-antigen. We also show that ppCT includes HLA-A2-restricted epitopes that are processed by TAP-independent and -dependent pathways. Processing occurs in either the endoplasmic reticulum, by signal peptidase and signal peptide peptidase, or in the cytosol after release of a signal peptide precursor or retrotranslocation of a procalcitonin substrate by endoplasmic-reticulum-associated degradation. Remarkably, ppCT peptide-based immunotherapy induces efficient T-cell responses toward antigen processing and presenting machinery-impaired tumours transplanted into HLA-A*0201-transgenic mice and in NOD-scid-Il2rγnull mice adoptively transferred with human PBMC. Thus, ppCT-specific T lymphocytes are promising effectors for treatment of tumours that have escaped immune recognition.
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Affiliation(s)
- Aurélie Durgeau
- INSERM UMR 1186, Integrative Tumour Immunology and Genetic Oncology, Gustave Roussy, EPHE, PSL, Fac. de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France.,ElyssaMed, Paris Biotech Santé, 75014, Paris, France
| | - Yasemin Virk
- INSERM UMR 1186, Integrative Tumour Immunology and Genetic Oncology, Gustave Roussy, EPHE, PSL, Fac. de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France
| | - Gwendoline Gros
- INSERM UMR 1186, Integrative Tumour Immunology and Genetic Oncology, Gustave Roussy, EPHE, PSL, Fac. de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France
| | - Elodie Voilin
- INSERM UMR 1186, Integrative Tumour Immunology and Genetic Oncology, Gustave Roussy, EPHE, PSL, Fac. de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France
| | - Stéphanie Corgnac
- INSERM UMR 1186, Integrative Tumour Immunology and Genetic Oncology, Gustave Roussy, EPHE, PSL, Fac. de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France
| | - Fayçal Djenidi
- INSERM UMR 1186, Integrative Tumour Immunology and Genetic Oncology, Gustave Roussy, EPHE, PSL, Fac. de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France
| | - Jérôme Salmon
- CNRS (Centre National de la Recherche Scientifique) UMR 8122, Gustave Roussy, Faculté de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France
| | - Julien Adam
- INSERM U 981, Gustave Roussy, Faculté de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France
| | - Vincent de Montpréville
- INSERM UMR 1186, Integrative Tumour Immunology and Genetic Oncology, Gustave Roussy, EPHE, PSL, Fac. de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France.,Service d'Anatomie Pathologique, Centre Chirurgical Marie-Lannelongue, 92350, Le-Plessis-Robinson, France
| | - Pierre Validire
- Service d'Anatomie Pathologique, Institut Mutualiste Montsouris, 75014, Paris, France
| | - Soldano Ferrone
- Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA
| | - Salem Chouaib
- INSERM UMR 1186, Integrative Tumour Immunology and Genetic Oncology, Gustave Roussy, EPHE, PSL, Fac. de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France.,Thumbay Institute for Precision Medicine, Gulf Medical University, Ajman, 4184, UAE
| | - Alexander Eggermont
- Cancer Institute, Gustave Roussy Cancer Campus, Grand Paris, 94805, Villejuif, France
| | - Jean-Charles Soria
- Department of Drug Development (DITEP), Gustave Roussy, 94805, Villejuif, France
| | - François Lemonnier
- Département Endocrinologie, Métabolisme et Diabète, Equipe Immunologie des Diabètes, INSERM U1016, 75014, Paris, France
| | - Eric Tartour
- INSERM U970, Paris Cardiovascular Research Centre, Université Paris-Descartes, Sorbonne Paris Cité, Equipe Labellisée Ligue Contre le Cancer, Hôpital Européen Georges Pompidou, Service d'Immunologie Biologique, 75015, Paris, France
| | - Nathalie Chaput
- Laboratory of Immunomonitoring in Oncology, and CNRS-UMS 3655 and INSERM-US23, Gustave Roussy Cancer Campus, Villejuif, France.,Faculté de Pharmacie, University Paris-Sud, F-92296, Chatenay-Malabry, France
| | - Benjamin Besse
- Département de Médecine, Gustave Roussy, 94805, Villejuif, France
| | - Fathia Mami-Chouaib
- INSERM UMR 1186, Integrative Tumour Immunology and Genetic Oncology, Gustave Roussy, EPHE, PSL, Fac. de Médecine, Univ. Paris-Sud, Université Paris-Saclay, 94805, Villejuif, France.
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14
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Van Puyenbroeck V, Vermeire K. Inhibitors of protein translocation across membranes of the secretory pathway: novel antimicrobial and anticancer agents. Cell Mol Life Sci 2018; 75:1541-1558. [PMID: 29305616 PMCID: PMC5897483 DOI: 10.1007/s00018-017-2743-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 12/15/2017] [Accepted: 12/27/2017] [Indexed: 12/22/2022]
Abstract
Proteins routed to the secretory pathway start their journey by being transported across biological membranes, such as the endoplasmic reticulum. The essential nature of this protein translocation process has led to the evolution of several factors that specifically target the translocon and block translocation. In this review, various translocation pathways are discussed together with known inhibitors of translocation. Properties of signal peptide-specific systems are highlighted for the development of new therapeutic and antimicrobial applications, as compounds can target signal peptides from either host cells or pathogens and thereby selectively prevent translocation of those specific proteins. Broad inhibition of translocation is also an interesting target for the development of new anticancer drugs because cancer cells heavily depend on efficient protein translocation into the endoplasmic reticulum to support their fast growth.
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Affiliation(s)
- Victor Van Puyenbroeck
- Laboratory of Virology and Chemotherapy, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven - University of Leuven, 3000, Leuven, Belgium
| | - Kurt Vermeire
- Laboratory of Virology and Chemotherapy, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven - University of Leuven, 3000, Leuven, Belgium.
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15
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Figueiredo Costa B, Cassella P, Colombo SF, Borgese N. Discrimination between the endoplasmic reticulum and mitochondria by spontaneously inserting tail‐anchored proteins. Traffic 2018; 19:182-197. [DOI: 10.1111/tra.12550] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 01/18/2018] [Accepted: 01/18/2018] [Indexed: 01/16/2023]
Affiliation(s)
- Bruna Figueiredo Costa
- CNR Institute of Neuroscience and BIOMETRA DepartmentUniversità degli Studi di Milano Milan Italy
| | - Patrizia Cassella
- CNR Institute of Neuroscience and BIOMETRA DepartmentUniversità degli Studi di Milano Milan Italy
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16
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Berry GE, Asokan A. Chemical Modulation of Endocytic Sorting Augments Adeno-associated Viral Transduction. J Biol Chem 2016; 291:939-47. [PMID: 26527686 PMCID: PMC4705411 DOI: 10.1074/jbc.m115.687657] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 10/24/2015] [Indexed: 01/10/2023] Open
Abstract
Intracellular trafficking of viruses can be influenced by a variety of inter-connected cellular sorting and degradation pathways involving endo-lysosomal vesicles, the ubiquitin-proteasome system, and autophagy-based or endoplasmic reticulum-associated machinery. In the case of recombinant adeno-associated viruses (AAV), proteasome inhibitors are known to prevent degradation of ubiquitinated AAV capsids, thereby leading to increased nuclear accumulation and transduction. However, the impact of other cellular degradation pathways on AAV trafficking is not well understood. In the current study, we screened a panel of small molecules focused on modulating different cellular degradation pathways and identified eeyarestatin I (EerI) as a novel reagent that enhances AAV transduction. EerI improved AAV transduction by an order of magnitude regardless of vector dose, genome architecture, cell type, or serotype. This effect was preceded by sequestration of AAV within enlarged vesicles that were dispersed throughout the cytoplasm. Specifically, EerI treatment redirected AAV particles toward large vesicles positive for late endosomal (Rab7) and lysosomal (LAMP1) markers. Notably, MG132 and EerI (proteasomal and endoplasmic reticulum-associated degradation inhibitors, respectively) appear to enhance AAV transduction by increasing the intracellular accumulation of viral particles in a mutually exclusive fashion. Taken together, our results expand on potential strategies to redirect recombinant AAV vectors toward more productive trafficking pathways by deregulating cellular degradation mechanisms.
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Affiliation(s)
- Garrett E Berry
- From the Gene Therapy Center, Department of Genetics, Curriculum in Genetics and Molecular Biology, and
| | - Aravind Asokan
- From the Gene Therapy Center, Department of Genetics, Department of Biochemistry and Biophysics, The University of North Carolina, Chapel Hill, North Carolina 27599-7352
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17
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Kalies KU, Römisch K. Inhibitors of Protein Translocation Across the ER Membrane. Traffic 2015; 16:1027-38. [PMID: 26122014 DOI: 10.1111/tra.12308] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 06/18/2015] [Accepted: 06/22/2015] [Indexed: 12/21/2022]
Abstract
Protein translocation into the endoplasmic reticulum (ER) constitutes the first step of protein secretion. ER protein import is essential in all eukaryotic cells and is particularly critical in fast-growing tumour cells. Thus, the process can serve as target both for potential cancer drugs and for bacterial virulence factors. Inhibitors of protein transport across the ER membrane range from broad-spectrum to highly substrate-specific and can interfere with virtually any stage of this multistep process, and even with transport of endocytosed antigens into the cytosol for cross-presentation.
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Affiliation(s)
- Kai-Uwe Kalies
- Institute of Biology, CSCM, University of Lübeck, Lübeck, Germany
| | - Karin Römisch
- Department of Microbiology, Faculty of Natural Sciences and Technology VIII, Saarland University, 66123, Saarbrücken, Germany
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18
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Meinig JM, Fu L, Peterson BR. Synthesis of Fluorophores that Target Small Molecules to the Endoplasmic Reticulum of Living Mammalian Cells. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201504156] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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19
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Meinig JM, Fu L, Peterson BR. Synthesis of Fluorophores that Target Small Molecules to the Endoplasmic Reticulum of Living Mammalian Cells. Angew Chem Int Ed Engl 2015; 54:9696-9. [PMID: 26118368 DOI: 10.1002/anie.201504156] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Indexed: 01/09/2023]
Abstract
The endoplasmic reticulum (ER) plays critical roles in the processing of secreted and transmembrane proteins. To deliver small molecules to this organelle, we synthesized fluorinated hydrophobic analogues of the fluorophore rhodol. These cell-permeable fluorophores are exceptionally bright, with quantum yields of around 0.8, and they were found to specifically accumulate in the ER of living HeLa cells, as imaged by confocal laser scanning microscopy. To target a biological pathway controlled by the ER, we linked a fluorinated hydrophobic rhodol to 5-nitrofuran-2-acrylaldehyde. In contrast to an untargeted nitrofuran warhead, delivery of this electrophilic nitrofuran to the ER by the rhodol resulted in cytotoxicity comparable to the ER-targeted cytotoxin eeyarestatin I, and specifically inhibited protein processing by the ubiquitin-proteasome system. Fluorinated hydrophobic rhodols are outstanding fluorophores that enable the delivery of small molecules for targeting ER-associated proteins and pathways.
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Affiliation(s)
- J Matthew Meinig
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS 66045 (USA)
| | - Liqiang Fu
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS 66045 (USA)
| | - Blake R Peterson
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS 66045 (USA).
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20
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Deubiquitinase inhibition as a cancer therapeutic strategy. Pharmacol Ther 2015; 147:32-54. [DOI: 10.1016/j.pharmthera.2014.11.002] [Citation(s) in RCA: 200] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 09/16/2014] [Indexed: 12/27/2022]
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21
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Whole-genome RNAi screen highlights components of the endoplasmic reticulum/Golgi as a source of resistance to immunotoxin-mediated cytotoxicity. Proc Natl Acad Sci U S A 2015; 112:E1135-42. [PMID: 25713356 DOI: 10.1073/pnas.1501958112] [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] [Indexed: 11/18/2022] Open
Abstract
Immunotoxins (antibody-toxin fusion proteins) target surface antigens on cancer cells and kill these cells via toxin-mediated inhibition of protein synthesis. To identify genes controlling this process, an RNAi whole-genome screen (∼ 22,000 genes at three siRNAs per gene) was conducted via monitoring the cytotoxicity of the mesothelin-directed immunotoxin SS1P. SS1P, a Pseudomonas exotoxin-based immunotoxin, was chosen because it is now in clinical trials and has produced objective tumor regressions in patients. High and low concentrations of SS1P were chosen to allow for the identification of both mitigators and sensitizers. As expected, silencing known essential genes in the immunotoxin pathway, such as mesothelin, furin, KDEL receptor 2, or members of the diphthamide pathway, protected cells. Of greater interest was the observation that many RNAi targets increased immunotoxin sensitivity, indicating that these gene products normally contribute to inefficiencies in the killing pathway. Of the top sensitizers, many genes encode proteins that locate to either the endoplasmic reticulum (ER) or Golgi and are annotated as part of the secretory system. Genes related to the ER-associated degradation system were not among high-ranking mitigator or sensitizer candidates. However, the p97 inhibitor eeyarestatin 1 enhanced immunotoxin killing. Our results highlight potential targets for chemical intervention that could increase immunotoxin killing of cancer cells and enhance our understanding of toxin trafficking.
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22
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Abstract
ABSTRACT
Shiga toxin (Stx)-producing
Escherichia coli
(STEC) is an etiologic agent of bloody diarrhea. A serious sequela of disease, the hemolytic uremic syndrome (HUS) may arise in up to 25% of patients. The development of HUS after STEC infection is linked to the presence of Stx. STEC strains may produce one or more Stxs, and the Stxs come in two major immunological groups, Stx1 and Stx2. A multitude of possible therapeutics designed to inhibit the actions of the Stxs have been developed over the past 30 years. Such therapeutics are important because antibiotic treatment of STEC infections is contraindicated due to an increased potential for development of HUS. The reason for the increased risk of HUS after antibiotic treatment is likely because certain antibiotics induce expression of the Stxs, which are generally associated with lysogenic bacteriophages. There are a few potential therapeutics that either try to kill STEC without inducing Stx expression or target gene expression within STEC. However, the vast majority of the treatments under development are designed to limit Stx receptor generation or to prevent toxin binding, trafficking, processing, or activity within the cell. The potential therapies described in this review include some that have only been tested in vitro and several that demonstrate efficacy in animals. The therapeutics that are currently the furthest along in development (completed phase I and II trials) are monoclonal antibodies directed against Stx1 and Stx2.
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23
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Abstract
Shiga toxin (Stx) is one of the most potent bacterial toxins known. Stx is found in Shigella dysenteriae 1 and in some serogroups of Escherichia coli (called Stx1 in E. coli). In addition to or instead of Stx1, some E. coli strains produce a second type of Stx, Stx2, that has the same mode of action as Stx/Stx1 but is antigenically distinct. Because subtypes of each toxin have been identified, the prototype toxin for each group is now designated Stx1a or Stx2a. The Stxs consist of two major subunits, an A subunit that joins noncovalently to a pentamer of five identical B subunits. The A subunit of the toxin injures the eukaryotic ribosome and halts protein synthesis in target cells. The function of the B pentamer is to bind to the cellular receptor, globotriaosylceramide, Gb3, found primarily on endothelial cells. The Stxs traffic in a retrograde manner within the cell, such that the A subunit of the toxin reaches the cytosol only after the toxin moves from the endosome to the Golgi and then to the endoplasmic reticulum. In humans infected with Stx-producing E. coli, the most serious manifestation of the disease, hemolytic-uremic syndrome, is more often associated with strains that produce Stx2a rather than Stx1a, and that relative toxicity is replicated in mice and baboons. Stx1a and Stx2a also exhibit differences in cytotoxicity to various cell types, bind dissimilarly to receptor analogs or mimics, induce differential chemokine responses, and have several distinctive structural characteristics.
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Affiliation(s)
- Angela R. Melton-Celsa
- Department of Microbiology & Immunology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814,
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24
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Li S, Spooner RA, Hampton RY, Lord JM, Roberts LM. Cytosolic entry of Shiga-like toxin a chain from the yeast endoplasmic reticulum requires catalytically active Hrd1p. PLoS One 2012; 7:e41119. [PMID: 22829918 PMCID: PMC3400632 DOI: 10.1371/journal.pone.0041119] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Accepted: 06/19/2012] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Escherichia coli Shiga-like toxin 1 normally traffics to the endoplasmic reticulum (ER) in sensitive mammalian cells from where the catalytic A chain (SLTxA1) dislocates to the cytosol to inactivate ribosomes. Currently, no molecular details of the dislocation process are available. To investigate the mechanism of the dislocation step we expressed SLTxA1 in the ER of Saccharomyces cerevisiae. METHODOLOGY AND PRINCIPAL FINDINGS Using a combination of growth studies and biochemical tracking in yeast knock-out strains we show that SLTxA1 follows an ER-associated degradation (ERAD) pathway to enter the cytosol in a step mediated by the transmembrane Hrd1p ubiquitin ligase complex. ER-to-cytosol dislocation of the bulk population of SLTxA1 requires Cdc48p and its ubiquitin-handling co-factor Npl4p, and this population of toxin is terminally dispatched by proteasomal degradation. A small sub-population of SLTxA1 uncouples from this classical ERAD pathway and recovers catalytic activity in the cytosol. The pathway that leads to toxicity is also Hrd1p-dependent but, unlike that for the related ricin A chain toxin, SLTxA1 dislocation does require the catalytic cysteine of Hrd1p. However it does not depend on canonical ubiquitylation since toxin variants lacking endogenous lysyl residues also utilize this pathway, and furthermore there is no requirement for a number of Cdc48p co-factors. CONCLUSIONS AND SIGNIFICANCE The fraction of SLTxA1 that disengages from the ERAD pathway thus does so upstream of Cdc48p interactions and downstream of Hrd1p interactions, in a step that possibly involves de-ubiquitylation. Mechanistically therefore, the dislocation of this toxin is quite distinct from that of conventional ERAD substrates that are normally degraded, and the toxins partially characterised to date that do not require the catalytic cysteine of the major Hrd1p component of the dislocation apparatus.
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Affiliation(s)
- Shuyu Li
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Robert A. Spooner
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Randolph Y. Hampton
- Section of Cell and Developmental Biology, Division of Biology, University of California San Diego, La Jolla, California, United States of America
| | - J. Michael Lord
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Lynne M. Roberts
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
- * E-mail:
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25
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Inhibition of protein translocation at the endoplasmic reticulum promotes activation of the unfolded protein response. Biochem J 2012; 442:639-48. [PMID: 22145777 PMCID: PMC3286858 DOI: 10.1042/bj20111220] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Selective small-molecule inhibitors represent powerful tools for the dissection of complex biological processes. ESI (eeyarestatin I) is a novel modulator of ER (endoplasmic reticulum) function. In the present study, we show that in addition to acutely inhibiting ERAD (ER-associated degradation), ESI causes production of mislocalized polypeptides that are ubiquitinated and degraded. Unexpectedly, our results suggest that these non-translocated polypeptides promote activation of the UPR (unfolded protein response), and indeed we can recapitulate UPR activation with an alternative and quite distinct inhibitor of ER translocation. These results suggest that the accumulation of non-translocated proteins in the cytosol may represent a novel mechanism that contributes to UPR activation.
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26
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Johnson N, Vilardi F, Lang S, Leznicki P, Zimmermann R, High S. TRC40 can deliver short secretory proteins to the Sec61 translocon. J Cell Sci 2012; 125:3612-20. [PMID: 22505607 PMCID: PMC3445324 DOI: 10.1242/jcs.102608] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Whilst the co-translational translocation of nascent proteins across the mammalian endoplasmic reticulum (ER) is well defined, the capacity of this organelle for post-translational translocation is poorly delineated. Here we identify two human secretory protein precursors, apelin and statherin, as bona fide substrates for post-translational translocation across the ER membrane. Further studies, in combination with Hyalophora cecropia preprocecropin A (ppcecA), show that all three proteins bind to TRC40 and can utilise this component for their delivery to the ER membrane in a well-established in vitro system. However, ppcecA is not an obligate TRC40 substrate, and it can also be delivered to the ER by an alternative TRC40-independent pathway. Upon arrival at the ER membrane, these short secretory proteins appear to be ubiquitously transported across the ER membrane through the Sec61 translocon, apparently irrespective of their delivery route. We speculate that the post-translational translocation of secretory proteins in higher eukaryotes is more prevalent than previously acknowledged.
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Affiliation(s)
- Nicholas Johnson
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
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27
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Naydenov NG, Harris G, Brown B, Schaefer KL, Das SK, Fisher PB, Ivanov AI. Loss of soluble N-ethylmaleimide-sensitive factor attachment protein α (αSNAP) induces epithelial cell apoptosis via down-regulation of Bcl-2 expression and disruption of the Golgi. J Biol Chem 2011; 287:5928-41. [PMID: 22194596 DOI: 10.1074/jbc.m111.278358] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Intracellular trafficking represents a key mechanism that regulates cell fate by participating in either prodeath or prosurvival signaling. Soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein α (αSNAP) is a well known component of vesicle trafficking machinery that mediates intermembrane fusion. αSNAP increases cell resistance to cytotoxic stimuli, although mechanisms of its prosurvival function are poorly understood. In this study, we found that either siRNA-mediated knockdown of αSNAP or expression of its dominant negative mutant induced epithelial cell apoptosis. Apoptosis was not caused by activation of the major prodeath regulators Bax and p53 and was independent of a key αSNAP binding partner, NSF. Instead, death of αSNAP-depleted cells was accompanied by down-regulation of the antiapoptotic Bcl-2 protein; it was mimicked by inhibition and attenuated by overexpression of Bcl-2. Knockdown of αSNAP resulted in impairment of Golgi to endoplasmic reticulum (ER) trafficking and fragmentation of the Golgi. Moreover, pharmacological disruption of ER-Golgi transport by brefeldin A and eeyarestatin 1 or siRNA-mediated depletion of an ER/Golgi-associated p97 ATPase recapitulated the effects of αSNAP inhibition by decreasing Bcl-2 level and triggering apoptosis. These results reveal a novel role for αSNAP in promoting epithelial cell survival by unique mechanisms involving regulation of Bcl-2 expression and Golgi biogenesis.
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Affiliation(s)
- Nayden G Naydenov
- Department of Medicine, University of Rochester, Rochester, New York 14642, USA
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