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Targeting the Inside of Cells with Biologicals: Toxin Routes in a Therapeutic Context. BioDrugs 2023; 37:181-203. [PMID: 36729328 PMCID: PMC9893211 DOI: 10.1007/s40259-023-00580-y] [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] [Accepted: 01/12/2023] [Indexed: 02/03/2023]
Abstract
Numerous toxins translocate to the cytosol in order to fulfil their function. This demonstrates the existence of routes for proteins from the extracellular space to the cytosol. Understanding these routes is relevant to multiple aspects related to therapeutic applications. These include the development of anti-toxin treatments, the potential use of toxins as shuttles for delivering macromolecular cargo to the cytosol or the use of drugs based on toxins. Compared with other strategies for delivery, such as chemicals as carriers for macromolecular delivery or physical methods like electroporation, toxin routes present paths into the cell that potentially cause less damage and can be specifically targeted. The efficiency of delivery via toxin routes is limited. However, low-delivery efficiencies can be entirely sufficient, if delivered cargoes possess an amplification effect or if very few molecules are sufficient for inducing the desired effects. This is known for example from RNA-based vaccines that have been developed during the coronavirus disease 2019 pandemic as well as for other approved RNA-based drugs, which elicited the desired effect despite their typically low delivery efficiencies. The different mechanisms by which toxins enter cells may have implications for their technological utility. We review the mechanistic principles of the translocation pathway of toxins from the extracellular space to the cytosol, the delivery efficiencies, and therapeutic strategies or applications that exploit toxin routes for intracellular delivery.
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2
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Zagirova D, Autenried R, Nelson ME, Rezvani K. Proteasome Complexes and Their Heterogeneity in Colorectal, Breast and Pancreatic Cancers. J Cancer 2021; 12:2472-2487. [PMID: 33854609 PMCID: PMC8040722 DOI: 10.7150/jca.52414] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 02/09/2021] [Indexed: 11/26/2022] Open
Abstract
Targeting the ubiquitin-proteasome system (UPS) - in particular, the proteasome complex - has emerged as an attractive novel cancer therapy. While several proteasome inhibitors have been successfully approved by the Food and Drug Administration for the treatment of hematological malignancies, the clinical efficacy of these inhibitors is unexpectedly lower in the treatment of solid tumors due to the functional and structural heterogeneity of proteasomes in solid tumors. There are ongoing trials to examine the effectiveness of compound and novel proteasome inhibitors that can target solid tumors either alone or in combination with conventional chemotherapeutic agents. The modest therapeutic efficacy of proteasome inhibitors such as bortezomib in solid malignancies demands further research to clarify the exact effects of these proteasome inhibitors on different proteasomes present in cancer cells. The structural, cellular localization and functional analysis of the proteasome complexes in solid tumors originated from different tissues provides new insights into the diversity of proteasomes' responses to inhibitors. In this study, we used an optimized iodixanol gradient ultracentrifugation to purify a native form of proteasome complexes with their intact associated protein partners enriched within distinct cellular compartments. It is therefore possible to isolate proteasome subcomplexes with far greater resolution than sucrose or glycerol fractionations. We have identified differences in the catalytic activities, subcellular distribution, and inhibitor sensitivity of cytoplasmic proteasomes isolated from human colon, breast, and pancreatic cancer cell lines. Our developed techniques and generated results will serve as a valuable guideline for investigators developing a new generation of proteasome inhibitors as an effective targeted therapy for solid tumors.
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Affiliation(s)
- Diana Zagirova
- Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, 414 E. Clark Street, Lee Medical Building, Vermillion, SD 57069, USA
| | - Rebecca Autenried
- Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, 414 E. Clark Street, Lee Medical Building, Vermillion, SD 57069, USA
| | - Morgan E Nelson
- Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, 414 E. Clark Street, Lee Medical Building, Vermillion, SD 57069, USA
| | - Khosrow Rezvani
- Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, 414 E. Clark Street, Lee Medical Building, Vermillion, SD 57069, USA
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3
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Intracellular Transport and Cytotoxicity of the Protein Toxin Ricin. Toxins (Basel) 2019; 11:toxins11060350. [PMID: 31216687 PMCID: PMC6628406 DOI: 10.3390/toxins11060350] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 06/13/2019] [Accepted: 06/14/2019] [Indexed: 12/17/2022] Open
Abstract
Ricin can be isolated from the seeds of the castor bean plant (Ricinus communis). It belongs to the ribosome-inactivating protein (RIP) family of toxins classified as a bio-threat agent due to its high toxicity, stability and availability. Ricin is a typical A-B toxin consisting of a single enzymatic A subunit (RTA) and a binding B subunit (RTB) joined by a single disulfide bond. RTA possesses an RNA N-glycosidase activity; it cleaves ribosomal RNA leading to the inhibition of protein synthesis. However, the mechanism of ricin-mediated cell death is quite complex, as a growing number of studies demonstrate that the inhibition of protein synthesis is not always correlated with long term ricin toxicity. To exert its cytotoxic effect, ricin A-chain has to be transported to the cytosol of the host cell. This translocation is preceded by endocytic uptake of the toxin and retrograde traffic through the trans-Golgi network (TGN) and the endoplasmic reticulum (ER). In this article, we describe intracellular trafficking of ricin with particular emphasis on host cell factors that facilitate this transport and contribute to ricin cytotoxicity in mammalian and yeast cells. The current understanding of the mechanisms of ricin-mediated cell death is discussed as well. We also comment on recent reports presenting medical applications for ricin and progress associated with the development of vaccines against this toxin.
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Guo Z, Wang Z, Meng S, Zhao Z, Zhang C, Fu Y, Li J, Nie X, Zhang C, Liu L, Lu B, Qian J. Effects of ricin on primary pulmonary alveolar macrophages. J Int Med Res 2019; 47:3763-3777. [PMID: 31156015 PMCID: PMC6726780 DOI: 10.1177/0300060519842959] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Objective We systematically investigated the cytotoxic effects of ricin in primary pulmonary alveolar macrophages (PAMs). Methods Primary PAMs were isolated from BALB/c mice. The cytotoxic effects of ricin were investigated in vitro by optical and transmission electron microscopy, detection of the inflammatory cytokine response, proteomic analysis, and subsequent biological functional analysis. Results Ricin induced shrinkage, apoptosis, vacuolization, and multi-organelle lesions in primary PAMs as demonstrated by optical and transmission electron microscopy. Ricin also induced a pronounced pro-inflammatory cytokine response in primary PAMs, including induction of tumor necrosis factor-α, interferon-γ, interleukin (IL)-1, IL-2, IL-6, IL-12, C-C motif chemokine ligand 2, and C-X-C motif chemokine ligand 2, while the anti-inflammatory cytokines IL-4 and IL-10 were less affected. Proteomic analysis and subsequent biological functional analysis identified eight proteins that were up/downregulated by ricin treatment and which might thus contribute to ricin toxicity. These proteins were involved in various functions, including redox, molecular chaperone, glycolysis, protein translation, and protein degradation functions. Conclusion The results of the present study further our understanding of the pathogenic mechanism of inhalational ricin poisoning.
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Affiliation(s)
- Zhendong Guo
- 1 Academy of Military Medical Sciences, Beijing, China
| | - Zhongyi Wang
- 1 Academy of Military Medical Sciences, Beijing, China
| | - Shanyu Meng
- 2 Agricultural and Biological Engineering Department, University of Florida, Gainesville, FL, USA
| | | | - Chunmao Zhang
- 1 Academy of Military Medical Sciences, Beijing, China
| | - Yingying Fu
- 1 Academy of Military Medical Sciences, Beijing, China
| | - Jiaming Li
- 1 Academy of Military Medical Sciences, Beijing, China
| | - Xin Nie
- 3 No. 65316 Unit of PLA, Dalian, China
| | - Cheng Zhang
- 1 Academy of Military Medical Sciences, Beijing, China
| | - Linna Liu
- 1 Academy of Military Medical Sciences, Beijing, China
| | - Bing Lu
- 1 Academy of Military Medical Sciences, Beijing, China
| | - Jun Qian
- 1 Academy of Military Medical Sciences, Beijing, China
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5
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Nowakowska-Gołacka J, Sominka H, Sowa-Rogozińska N, Słomińska-Wojewódzka M. Toxins Utilize the Endoplasmic Reticulum-Associated Protein Degradation Pathway in Their Intoxication Process. Int J Mol Sci 2019; 20:E1307. [PMID: 30875878 PMCID: PMC6471375 DOI: 10.3390/ijms20061307] [Citation(s) in RCA: 21] [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: 02/16/2019] [Revised: 03/08/2019] [Accepted: 03/10/2019] [Indexed: 12/25/2022] Open
Abstract
Several bacterial and plant AB-toxins are delivered by retrograde vesicular transport to the endoplasmic reticulum (ER), where the enzymatically active A subunit is disassembled from the holotoxin and transported to the cytosol. In this process, toxins subvert the ER-associated degradation (ERAD) pathway. ERAD is an important part of cellular regulatory mechanism that targets misfolded proteins to the ER channels, prior to their retrotranslocation to the cytosol, ubiquitination and subsequent degradation by a protein-degrading complex, the proteasome. In this article, we present an overview of current understanding of the ERAD-dependent transport of AB-toxins to the cytosol. We describe important components of ERAD and discuss their significance for toxin transport. Toxin recognition and disassembly in the ER, transport through ER translocons and finally cytosolic events that instead of overall proteasomal degradation provide proper folding and cytotoxic activity of AB-toxins are discussed as well. We also comment on recent reports presenting medical applications for toxin transport through the ER channels.
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Affiliation(s)
- Jowita Nowakowska-Gołacka
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland.
| | - Hanna Sominka
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland.
| | - Natalia Sowa-Rogozińska
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland.
| | - Monika Słomińska-Wojewódzka
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland.
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6
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Thermal Unfolding of the Pertussis Toxin S1 Subunit Facilitates Toxin Translocation to the Cytosol by the Mechanism of Endoplasmic Reticulum-Associated Degradation. Infect Immun 2016; 84:3388-3398. [PMID: 27647866 DOI: 10.1128/iai.00732-16] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 09/10/2016] [Indexed: 11/20/2022] Open
Abstract
Pertussis toxin (PT) moves from the host cell surface to the endoplasmic reticulum (ER) by retrograde vesicular transport. The catalytic PTS1 subunit dissociates from the rest of the toxin in the ER and then shifts to a disordered conformation which may trigger its export to the cytosol through the quality control mechanism of ER-associated degradation (ERAD). Functional roles for toxin instability and ERAD in PTS1 translocation have not been established. We addressed these issues with the use of a surface plasmon resonance system to quantify the cytosolic pool of PTS1 from intoxicated cells. Only 3% of surface-associated PTS1 reached the host cytosol after 3 h of toxin exposure. This represented, on average, 38,000 molecules of cytosolic PTS1 per cell. Cells treated with a proteasome inhibitor contained larger quantities of cytosolic PTS1. Stabilization of the dissociated PTS1 subunit with chemical chaperones inhibited toxin export to the cytosol and blocked PT intoxication. ERAD-defective cell lines likewise exhibited reduced quantities of cytosolic PTS1 and PT resistance. These observations identify the unfolding of dissociated PTS1 as a trigger for its ERAD-mediated translocation to the cytosol.
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7
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Zhao YQ, Song J, Wang HL, Xu B, Liu F, He K, Wang N. Rapid Detection of Ricin in Serum Based on Cu-Chelated Magnetic Beads Using Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:748-751. [PMID: 26873724 DOI: 10.1007/s13361-016-1340-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 01/02/2016] [Accepted: 01/09/2016] [Indexed: 06/05/2023]
Abstract
The protein toxin ricin obtained from castor bean plant (Ricinus communis) seeds is a potent biological warfare agent due to its ease of availability and acute toxicity. In this study, we demonstrated a rapid and simple method to detect ricin in serum in vitro. The ricin was mixed with serum and digested by trypsin, then all the peptides were efficiently extracted using Cu-chelated magnetic beads and were detected with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The specific ricin peptides were identified by Nanoscale Ultra Performance liquid chromatography coupled to tandem mass spectrometry according to their sequences. The assay required 2.5 hours, and a characteristic peptide could be detected down to 4 ng/μl and used as a biomarker to detect ricin in serum. The high sensitivity and simplicity of the procedure makes it valuable in clinical practice. Graphical Abstract ᅟ.
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Affiliation(s)
- Yong-Qiang Zhao
- The Institute of Basic Medical Sciences, National Center of Biomedical Analysis, Beijing, China, 100850
| | - Jian Song
- The School of Pharmacy, Jilin University, Changchun, China, 130021
| | - Hong-Li Wang
- The Institute of Basic Medical Sciences, National Center of Biomedical Analysis, Beijing, China, 100850
| | - Bin Xu
- The Institute of Basic Medical Sciences, National Center of Biomedical Analysis, Beijing, China, 100850
| | - Feng Liu
- The Institute of Basic Medical Sciences, National Center of Biomedical Analysis, Beijing, China, 100850
| | - Kun He
- The Institute of Basic Medical Sciences, National Center of Biomedical Analysis, Beijing, China, 100850.
| | - Na Wang
- The Institute of Basic Medical Sciences, National Center of Biomedical Analysis, Beijing, China, 100850.
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8
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Chang VT, Spooner RA, Crispin M, Davis SJ. Glycan Remodeling with Processing Inhibitors and Lectin-Resistant Eukaryotic Cells. Methods Mol Biol 2016; 1321:307-22. [PMID: 26082231 DOI: 10.1007/978-1-4939-2760-9_21] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Some of the most important and interesting molecules in metazoan biology are glycoproteins. The importance of the carbohydrate component of these structures is often revealed by the disease phenotypes that manifest when the biosynthesis of particular glycoforms is disrupted. On the other hand, the presence of large amounts of carbohydrate can often hinder the structural and functional analysis of glycoproteins. There are often good reasons, therefore, for wanting to engineer and predefine the N-glycans present on glycoproteins, e.g., in order to characterize the functions of the glycans or facilitate their subsequent removal. Here, we describe in detail two distinct ways in which to usefully interfere with oligosaccharide processing, one involving the use of specific processing inhibitors, and the other the selection of cell lines mutated at gene loci that control oligosaccharide processing, using cytotoxic lectins. Both approaches have the capacity for controlled, radical alteration of oligosaccharide processing in eukaryotic cells used for heterologous protein expression, and have great utility in the structural analysis of glycoproteins.
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Affiliation(s)
- Veronica T Chang
- Radcliffe Department of Medicine and MRC Human Immunology Unit, John Radcliffe Hospital, University of Oxford, Oxford, UK
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9
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Sokołowska I, Piłka ES, Sandvig K, Węgrzyn G, Słomińska-Wojewódzka M. Hydrophobicity of protein determinants influences the recognition of substrates by EDEM1 and EDEM2 in human cells. BMC Cell Biol 2015; 16:1. [PMID: 25655076 PMCID: PMC4340280 DOI: 10.1186/s12860-015-0047-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 01/05/2015] [Indexed: 11/22/2022] Open
Abstract
Background EDEM1 and EDEM2 are crucial regulators of the endoplasmic reticulum (ER)-associated degradation (ERAD) that extracts misfolded glycoproteins from the calnexin chaperone system. The degradation of ERAD substrates involves mannose trimming of N-linked glycans; however the precise mechanism of substrate recognition and sorting to the ERAD pathway is still poorly understood. It has previously been demonstrated that EDEM1 and EDEM2 binding does not require the trimming of substrate glycans or even ERAD substrate glycosylation, thus suggesting that both chaperones probably recognize misfolded regions of aberrant proteins. Results In this work, we focused on the substrate recognition by EDEM1 and EDEM2, asking whether hydrophobicity of protein determinants might be important for these interactions in human cells. In the study we used ricin, a protein toxin that utilizes the ERAD pathway in its retrotranslocation from the ER to the cytosol, and a model misfolded protein, the pancreatic isoform of human β-secretase, BACE457. Mutations in the hydrophobic regions of these proteins allowed us to obtain mutated forms with increased and decreased hydrophobicity. Conclusions Our data provide the first evidence that recognition of ERAD substrates by EDEM1 and EDEM2 might be determined by a sufficiently high hydrophobicity of protein determinants. Moreover, EDEM proteins can bind hydrophobic transmembrane regions of misfolded ERAD substrates. These data contribute to the general understanding of the regulation of ERAD in mammalian cells. Electronic supplementary material The online version of this article (doi:10.1186/s12860-015-0047-7) contains supplementary material, which is available to authorized users.
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10
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Abstract
The heterodimeric plant toxin ricin binds exposed galactosyls at the cell surface of target mammalian cells, and, following endocytosis, is transported in vesicular carriers to the endoplasmic reticulum (ER). Subsequently, the cell-binding B chain (RTB) and the catalytic A chain (RTA) are separated reductively, RTA embeds in the ER membrane and then retrotranslocates (or dislocates) across this membrane. The protein conducting channels used by RTA are usually regarded as part of the ER-associated protein degradation system (ERAD) that removes misfolded proteins from the ER for destruction by the cytosolic proteasomes. However, unlike ERAD substrates, cytosolic RTA avoids destruction and folds into a catalytic conformation that inactivates its target ribosomes. Protein synthesis ceases, and subsequently the cells die apoptotically. This raises questions about how this protein avoids the pathways that are normally sanctioned for ER-dislocating substrates. In this review we focus on the molecular events that occur with non-tagged ricin and its isolated subunits at the ER–cytosol interface. This focus reveals that intra-membrane interactions of RTA may control its fate, an area that warrants further investigation.
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Affiliation(s)
- Robert A Spooner
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK.
| | - J Michael Lord
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK.
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11
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Morris LL, Hartman IZ, Jun DJ, Seemann J, DeBose-Boyd RA. Sequential actions of the AAA-ATPase valosin-containing protein (VCP)/p97 and the proteasome 19 S regulatory particle in sterol-accelerated, endoplasmic reticulum (ER)-associated degradation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase. J Biol Chem 2014; 289:19053-66. [PMID: 24860107 DOI: 10.1074/jbc.m114.576652] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Accelerated endoplasmic reticulum (ER)-associated degradation (ERAD) of the cholesterol biosynthetic enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase results from its sterol-induced binding to ER membrane proteins called Insig-1 and Insig-2. This binding allows for subsequent ubiquitination of reductase by Insig-associated ubiquitin ligases. Once ubiquitinated, reductase becomes dislocated from ER membranes into the cytosol for degradation by 26 S proteasomes through poorly defined reactions mediated by the AAA-ATPase valosin-containing protein (VCP)/p97 and augmented by the nonsterol isoprenoid geranylgeraniol. Here, we report that the oxysterol 25-hydroxycholesterol and geranylgeraniol combine to trigger extraction of reductase across ER membranes prior to its cytosolic release. This conclusion was drawn from studies utilizing a novel assay that measures membrane extraction of reductase by determining susceptibility of a lumenal epitope in the enzyme to in vitro protease digestion. Susceptibility of the lumenal epitope to protease digestion and thus membrane extraction of reductase were tightly regulated by 25-hydroxycholesterol and geranylgeraniol. The reaction was inhibited by RNA interference-mediated knockdown of either Insigs or VCP/p97. In contrast, reductase continued to become membrane-extracted, but not cytosolically dislocated, in cells deficient for AAA-ATPases of the proteasome 19 S regulatory particle. These findings establish sequential roles for VCP/p97 and the 19 S regulatory particle in the sterol-accelerated ERAD of reductase that may be applicable to the ERAD of other substrates.
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Affiliation(s)
| | | | | | | | - Russell A DeBose-Boyd
- From the Departments of Molecular Genetics and the Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9046
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12
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Role of Fc in antibody-mediated protection from ricin toxin. Toxins (Basel) 2014; 6:1512-25. [PMID: 24811206 PMCID: PMC4052250 DOI: 10.3390/toxins6051512] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 03/24/2014] [Accepted: 03/28/2014] [Indexed: 11/28/2022] Open
Abstract
We have studied the role of the antibody (Ab) Fc region in mediating protection from ricin toxicity. We compared the in vitro and in vivo effects of intact Ig and of Fab fragments derived from two different neutralizing Ab preparations, one monoclonal, the other polyclonal. Consistent results were obtained from each, showing little difference between Ig and Fab in terms of antigen binding and in vitro neutralization, but with relatively large differences in protection of animals. We also studied whether importing Ab into the cell by Fc receptors enhanced the intracellular neutralization of ricin toxin. We found that the imported Ab was found in the ER and Golgi, a compartment traversed by ricin, as it traffics through the cell, but intracellular Ab did not contribute to the neutralization of ricin. These results indicate that the Fc region of antibody is important for in vivo protection, although the mechanism of enhanced protection by intact Ig does not appear to operate at the single cell level. When using xenogeneic antibodies, the diminished immunogenicity of Fab/F(ab’)2 preparations should be balanced against possible loss of protective efficacy.
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Redmann V, Gardner T, Lau Z, Morohashi K, Felsenfeld D, Tortorella D. Novel class of potential therapeutics that target ricin retrograde translocation. Toxins (Basel) 2013; 6:33-53. [PMID: 24366208 PMCID: PMC3920248 DOI: 10.3390/toxins6010033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 12/11/2013] [Accepted: 12/16/2013] [Indexed: 01/11/2023] Open
Abstract
Ricin toxin, an A-B toxin from Ricinus communis, induces cell death through the inhibition of protein synthesis. The toxin binds to the cell surface via its B chain (RTB) followed by its retrograde trafficking through intracellular compartments to the ER where the A chain (RTA) is transported across the membrane and into the cytosol. Ricin A chain is transported across the ER membrane utilizing cellular proteins involved in the disposal of aberrant ER proteins by a process referred to as retrograde translocation. Given the current lack of therapeutics against ricin intoxication, we developed a high-content screen using an enzymatically attenuated RTA chimera engineered with a carboxy-terminal enhanced green fluorescent protein (RTA(E177Q)egfp) to identify compounds that target RTA retrograde translocation. Stabilizing RTA(E177Q)egfp through the inclusion of proteasome inhibitor produced fluorescent peri-nuclear granules. Quantitative analysis of the fluorescent granules provided the basis to discover compounds from a small chemical library (2080 compounds) with known bioactive properties. Strikingly, the screen found compounds that stabilized RTA molecules within the cell and several compounds limited the ability of wild type RTA to suppress protein synthesis. Collectively, a robust high-content screen was developed to discover novel compounds that stabilize intracellular ricin and limit ricin intoxication.
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Affiliation(s)
- Veronika Redmann
- Icahn School of Medicine at Mount Sinai, Department of Microbiology, One Gustave L. Levy Place, New York, NY 10029, USA; E-Mails: (V.R.); (T.G.)
| | - Thomas Gardner
- Icahn School of Medicine at Mount Sinai, Department of Microbiology, One Gustave L. Levy Place, New York, NY 10029, USA; E-Mails: (V.R.); (T.G.)
| | - Zerlina Lau
- Icahn School of Medicine at Mount Sinai, Integrated Screening Core, Experimental Therapeutics Institute, One Gustave L. Levy Place, New York, NY 10029, USA; E-Mails: (Z.L.); (K.M.); (D.F.)
| | - Keita Morohashi
- Icahn School of Medicine at Mount Sinai, Integrated Screening Core, Experimental Therapeutics Institute, One Gustave L. Levy Place, New York, NY 10029, USA; E-Mails: (Z.L.); (K.M.); (D.F.)
| | - Dan Felsenfeld
- Icahn School of Medicine at Mount Sinai, Integrated Screening Core, Experimental Therapeutics Institute, One Gustave L. Levy Place, New York, NY 10029, USA; E-Mails: (Z.L.); (K.M.); (D.F.)
| | - Domenico Tortorella
- Icahn School of Medicine at Mount Sinai, Department of Microbiology, One Gustave L. Levy Place, New York, NY 10029, USA; E-Mails: (V.R.); (T.G.)
- Author whom correspondence should be addressed. E-Mail: ; Tel.: +1-212-2415447; Fax: +1-212-534-1684
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Teter K. Toxin instability and its role in toxin translocation from the endoplasmic reticulum to the cytosol. Biomolecules 2013; 3:997-1029. [PMID: 24970201 PMCID: PMC4030972 DOI: 10.3390/biom3040997] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 11/26/2013] [Accepted: 11/27/2013] [Indexed: 12/21/2022] Open
Abstract
AB toxins enter a host cell by receptor-mediated endocytosis. The catalytic A chain then crosses the endosome or endoplasmic reticulum (ER) membrane to reach its cytosolic target. Dissociation of the A chain from the cell-binding B chain occurs before or during translocation to the cytosol, and only the A chain enters the cytosol. In some cases, AB subunit dissociation is facilitated by the unique physiology and function of the ER. The A chains of these ER-translocating toxins are stable within the architecture of the AB holotoxin, but toxin disassembly results in spontaneous or assisted unfolding of the isolated A chain. This unfolding event places the A chain in a translocation-competent conformation that promotes its export to the cytosol through the quality control mechanism of ER-associated degradation. A lack of lysine residues for ubiquitin conjugation protects the exported A chain from degradation by the ubiquitin-proteasome system, and an interaction with host factors allows the cytosolic toxin to regain a folded, active state. The intrinsic instability of the toxin A chain thus influences multiple steps of the intoxication process. This review will focus on the host-toxin interactions involved with A chain unfolding in the ER and A chain refolding in the cytosol.
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Affiliation(s)
- Ken Teter
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, 12722 Research Parkway, Orlando, FL 32826, USA.
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