1
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Dutta A, Szekely Z, Guven H, Li XP, McLaughlin JE, Tumer NE. A fluorescence anisotropy-based competition assay to identify inhibitors against ricin and Shiga toxin ribosome interactions. Anal Biochem 2024; 692:115580. [PMID: 38825159 DOI: 10.1016/j.ab.2024.115580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 05/16/2024] [Accepted: 05/24/2024] [Indexed: 06/04/2024]
Abstract
Ricin is one of the most toxic substances known and a type B biothreat agent. Shiga toxins (Stxs) produced by E. coli (STEC) and Shigella dysenteriae are foodborne pathogens. There is no effective therapy against ricin or STEC and there is an urgent need for inhibitors. Ricin toxin A subunit (RTA) and A1 subunit of Stx2a (Stx2A1) bind to the C-terminal domain (CTD) of the ribosomal P-stalk proteins to depurinate the sarcin/ricin loop. Modulation of toxin-ribosome interactions has not been explored as a strategy for inhibition. Therefore, development of assays that detect inhibitors targeting toxin-ribosome interactions remains a critical need. Here we describe a fluorescence anisotropy (FA)-based competitive binding assay using a BODIPY-TMR labeled 11-mer peptide (P11) derived from the P-stalk CTD to measure the binding affinity of peptides ranging from 3 to 11 amino acids for the P-stalk pocket of RTA and Stx2A1. Comparison of the affinity with the surface plasmon resonance (SPR) assay indicated that although the rank order was the same by both methods, the FA assay could differentiate better between peptides that show nonspecific interactions by SPR. The FA assay detects only interactions that compete with the labeled P11 and can validate inhibitor specificity and mechanism of action.
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Affiliation(s)
- Arkajyoti Dutta
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ, 08901, USA
| | - Zoltan Szekely
- Molecular Design and Synthesis Core, Rutgers University Biomolecular Innovations Cores, Office for Research, Rutgers University, 610 Taylor Rd, Piscataway, NJ, 08854, USA
| | - Hakan Guven
- Molecular Design and Synthesis Core, Rutgers University Biomolecular Innovations Cores, Office for Research, Rutgers University, 610 Taylor Rd, Piscataway, NJ, 08854, USA
| | - Xiao-Ping Li
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ, 08901, USA.
| | - John E McLaughlin
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ, 08901, USA
| | - Nilgun E Tumer
- Molecular Design and Synthesis Core, Rutgers University Biomolecular Innovations Cores, Office for Research, Rutgers University, 610 Taylor Rd, Piscataway, NJ, 08854, USA.
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2
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Zheng X, Shen J, Jiang H, Tian M, Wang Q, Guo K, Chen R, Xia Q, Yan Q, Du L, Duan S. Exploring the multifaceted role of GCN1: Implications in cellular responses and disease pathogenesis. Biomed Pharmacother 2024; 175:116681. [PMID: 38705128 DOI: 10.1016/j.biopha.2024.116681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2024] [Revised: 04/21/2024] [Accepted: 04/29/2024] [Indexed: 05/07/2024] Open
Abstract
GCN1 is a highly conserved protein present widely across eukaryotes. As an upstream activator of protein kinase GCN2, GCN1 plays a pivotal role in integrated stress responses, such as amino acid starvation and oxidative stress. Through interaction with GCN2, GCN1 facilitates the activation of GCN2, thus initiating downstream signaling cascades in response to cellular stressors. In these contexts, the activation of GCN2 necessitates the presence and action of GCN1. Notably, GCN1 also operates as a ribosome collision sensor, contributing significantly to the translation quality control pathway. These discoveries offer valuable insights into cellular responses to internal stresses, vital for maintaining cellular homeostasis. Additionally, GCN1 exhibits the ability to regulate the cell cycle and suppress inflammation, among other processes, independently of GCN2. Our review outlines the structural characteristics and biological functions of GCN1, shedding light on its significant involvement in the onset and progression of various cancer and non-cancer diseases. Our work underscores the role of GCN1 in the context of drug therapeutic effects, hinting at its potential as a promising drug target. Furthermore, our work delves deep into the functional mechanisms of GCN1, promising innovative avenues for the diagnosis and treatment of diseases in the future. The exploration of GCN1's multifaceted roles not only enhances our understanding of its mechanisms but also paves the way for novel therapeutic interventions. The ongoing quest to unveil additional functions of GCN1 holds the promise of further enriching our comprehension of its mode of action.
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Affiliation(s)
- Xinying Zheng
- College of Pharmacy, Zhejiang University of Technology, Hangzhou, Zhejiang 310014, China; Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang 310015, China
| | - Jinze Shen
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang 310015, China
| | - Hongting Jiang
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang 310015, China
| | - Mei Tian
- College of Pharmacy, Zhejiang University of Technology, Hangzhou, Zhejiang 310014, China; Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang 310015, China; Geriatric Medicine Center, Department of Endocrinology, Zhejiang Provincial People's Hospital (Affiliated People's Hospital), Hangzhou Medical College, Hangzhou, Zhejiang 310014, China
| | - Qurui Wang
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang 310015, China
| | - Kailin Guo
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang 310015, China
| | - Ruixiu Chen
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang 310015, China
| | - Qing Xia
- College of Pharmacy, Zhejiang University of Technology, Hangzhou, Zhejiang 310014, China; Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang 310015, China
| | - Qibin Yan
- College of Pharmacy, Zhejiang University of Technology, Hangzhou, Zhejiang 310014, China; Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang 310015, China
| | - Lihua Du
- College of Pharmacy, Zhejiang University of Technology, Hangzhou, Zhejiang 310014, China
| | - Shiwei Duan
- Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University, Hangzhou, Zhejiang 310015, China.
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3
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Li XP, Rudolph MJ, Chen Y, Tumer NE. Structure-Function Analysis of the A1 Subunit of Shiga Toxin 2 with Peptides That Target the P-Stalk Binding Site and Inhibit Activity. Biochemistry 2024; 63:893-905. [PMID: 38467020 DOI: 10.1021/acs.biochem.3c00733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Shiga toxin 2a (Stx2a) is the virulence factor of Escherichia coli (STEC), which is associated with hemolytic uremic syndrome, the leading cause of pediatric kidney failure. The A1 subunit of Stx2a (Stx2A1) binds to the conserved C-terminal domain (CTD) of the ribosomal P-stalk proteins to remove an adenine from the sarcin-ricin loop (SRL) in the 28S rRNA, inhibiting protein synthesis. There are no antidotes against Stx2a or any other ribosome-inactivating protein (RIP). The structural and functional details of the binding of Stx2A1 to the P-stalk CTD are not known. Here, we carry out a deletion analysis of the conserved P-stalk CTD and show that the last eight amino acids (P8) of the P-stalk proteins are the minimal sequence required for optimal affinity and maximal inhibitory activity against Stx2A1. We determined the first X-ray crystal structure of Stx2A1 alone and in complex with P8 and identified the exact binding site. The C-terminal aspartic acid of the P-stalk CTD serves as an anchor, forming key contacts with the conserved arginine residues at the P-stalk binding pocket of Stx2A1. Although the ricin A subunit (RTA) binds to the P-stalk CTD, the last aspartic acid is more critical for the interaction with Stx2A1, indicating that RIPs differ in their requirements for the P-stalk. These results demonstrate that the catalytic activity of Stx2A1 is inhibited by blocking its interactions with the P-stalk, providing evidence that P-stalk binding is an essential first step in the recruitment of Stx2A1 to the SRL for depurination.
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Affiliation(s)
- Xiao-Ping Li
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 08901, United States
| | - Michael J Rudolph
- New York Structural Biology Center, 89 Convent Ave, New York, New York 10027, United States
| | - Yang Chen
- New York Structural Biology Center, 89 Convent Ave, New York, New York 10027, United States
| | - Nilgun E Tumer
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 08901, United States
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4
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Rudolph MJ, Dutta A, Tsymbal AM, McLaughlin JE, Chen Y, Davis SA, Theodorous SA, Pierce M, Algava B, Zhang X, Szekely Z, Roberge JY, Li XP, Tumer NE. Structure-based design and optimization of a new class of small molecule inhibitors targeting the P-stalk binding pocket of ricin. Bioorg Med Chem 2024; 100:117614. [PMID: 38340640 DOI: 10.1016/j.bmc.2024.117614] [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: 12/18/2023] [Revised: 01/24/2024] [Accepted: 01/26/2024] [Indexed: 02/12/2024]
Abstract
Ricin, a category-B agent for bioterrorism, and Shiga toxins (Stxs), which cause food poisoning bind to the ribosomal P-stalk to depurinate the sarcin/ricin loop. No effective therapy exists for ricin or Stx intoxication. Ribosome binding sites of the toxins have not been targeted by small molecules. We previously identified CC10501, which inhibits toxin activity by binding the P-stalk pocket of ricin toxin A subunit (RTA) remote from the catalytic site. Here, we developed a fluorescence polarization assay and identified a new class of compounds, which bind P-stalk pocket of RTA with higher affinity and inhibit catalytic activity with submicromolar potency. A lead compound, RU-NT-206, bound P-stalk pocket of RTA with similar affinity as a five-fold larger P-stalk peptide and protected cells against ricin and Stx2 holotoxins for the first time. These results validate the P-stalk binding site of RTA as a critical target for allosteric inhibition of the active site.
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Affiliation(s)
- Michael J Rudolph
- New York Structural Biology Center, 89 Convent Ave, New York, NY 10027, United States
| | - Arkajyoti Dutta
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ 08901, United States
| | - Anastasiia M Tsymbal
- Molecular Design and Synthesis Core, Rutgers University Biomolecular Innovations Cores, Office for Research, Rutgers University, 610 Taylor Rd, Piscataway, NJ 08854, United States
| | - John E McLaughlin
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ 08901, United States
| | - Yang Chen
- New York Structural Biology Center, 89 Convent Ave, New York, NY 10027, United States
| | - Simon A Davis
- New York Structural Biology Center, 89 Convent Ave, New York, NY 10027, United States
| | - Sophia A Theodorous
- New York Structural Biology Center, 89 Convent Ave, New York, NY 10027, United States
| | - Michael Pierce
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ 08901, United States
| | - Benjamin Algava
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ 08901, United States
| | - Xiaoyu Zhang
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ 08901, United States
| | - Zoltan Szekely
- Molecular Design and Synthesis Core, Rutgers University Biomolecular Innovations Cores, Office for Research, Rutgers University, 610 Taylor Rd, Piscataway, NJ 08854, United States
| | - Jacques Y Roberge
- Molecular Design and Synthesis Core, Rutgers University Biomolecular Innovations Cores, Office for Research, Rutgers University, 610 Taylor Rd, Piscataway, NJ 08854, United States
| | - Xiao-Ping Li
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ 08901, United States.
| | - Nilgun E Tumer
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, NJ 08901, United States.
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5
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Santos-López J, Gómez S, Fernández FJ, Vega MC. Protein-Protein Binding Kinetics by Biolayer Interferometry. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 3234:73-88. [PMID: 38507201 DOI: 10.1007/978-3-031-52193-5_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/22/2024]
Abstract
The specific kinetics and thermodynamics of protein-protein interactions underlie the molecular mechanisms of cellular functions; hence the characterization of these interaction parameters is central to the quantitative understanding of physiological and pathological processes. Many methods have been developed to study protein-protein interactions, which differ in various features including the interaction detection principle, the sensitivity, whether the method operates in vivo, in vitro, or in silico, the temperature control, the use of labels, immobilization, the amount of sample required, the number of measurements that can be accomplished simultaneously, or the cost. Bio-Layer Interferometry (BLI) is a label-free biophysical method to measure the kinetics of protein-protein interactions. Label-free interaction assays are a broad family of methods that do not require protein modifications (other than immobilization) or labels such as fusions with fluorescent proteins or transactivating domains or chemical modifications like biotinylation or reaction with radionuclides. Besides BLI, other label-free techniques that are widely used for determining protein-protein interactions include surface plasmon resonance (SPR), thermophoresis, and isothermal titration calorimetry (ITC), among others.
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Affiliation(s)
- Jorge Santos-López
- Centro de Investigaciones Biológicas Margarita Salas (CIB-CSIC), Madrid, Spain
| | - Sara Gómez
- Centro de Investigaciones Biológicas Margarita Salas (CIB-CSIC), Madrid, Spain
- Universidad Europea de Madrid, Madrid, Spain
| | | | - M Cristina Vega
- Centro de Investigaciones Biológicas Margarita Salas (CIB-CSIC), Madrid, Spain.
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6
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Cryo-EM structure of Shiga toxin 2 in complex with the native ribosomal P-stalk reveals residues involved in the binding interaction. J Biol Chem 2022; 299:102795. [PMID: 36528064 PMCID: PMC9823235 DOI: 10.1016/j.jbc.2022.102795] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 12/05/2022] [Accepted: 12/09/2022] [Indexed: 12/23/2022] Open
Abstract
Shiga toxin 2a (Stx2a) is the virulence factor of enterohemorrhagic Escherichia coli. The catalytic A1 subunit of Stx2a (Stx2A1) interacts with the ribosomal P-stalk for loading onto the ribosome and depurination of the sarcin-ricin loop, which halts protein synthesis. Because of the intrinsic flexibility of the P-stalk, a structure of the Stx2a-P-stalk complex is currently unknown. We demonstrated that the native P-stalk pentamer binds to Stx2a with nanomolar affinity, and we employed cryo-EM to determine a structure of the 72 kDa Stx2a complexed with the P-stalk. The structure identifies Stx2A1 residues involved in binding and reveals that Stx2a is anchored to the P-stalk via only the last six amino acids from the C-terminal domain of a single P-protein. For the first time, the cryo-EM structure shows the loop connecting Stx2A1 and Stx2A2, which is critical for activation of the toxin. Our principal component analysis of the cryo-EM data reveals the intrinsic dynamics of the Stx2a-P-stalk interaction, including conformational changes in the P-stalk binding site occurring upon complex formation. Our computational analysis unveils the propensity for structural rearrangements within the C-terminal domain, with its C-terminal six amino acids transitioning from a random coil to an α-helix upon binding to Stx2a. In conclusion, our cryo-EM structure sheds new light into the dynamics of the Stx2a-P-stalk interaction and indicates that the binding interface between Stx2a and the P-stalk is the potential target for drug discovery.
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7
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Parenteral Exposure of Mice to Ricin Toxin Induces Fatal Hypoglycemia by Cytokine-Mediated Suppression of Hepatic Glucose-6-Phosphatase Expression. Toxins (Basel) 2022; 14:toxins14120820. [PMID: 36548717 PMCID: PMC9786807 DOI: 10.3390/toxins14120820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 11/08/2022] [Accepted: 11/14/2022] [Indexed: 11/25/2022] Open
Abstract
Ricin toxin is an agent of biodefense concern and we have been developing countermeasures for ricin threats. In doing so, we sought biomarkers of ricin toxicosis and found that in mice parenteral injection of ricin toxin causes profound hypoglycemia, in the absence of other clinical laboratory abnormalities. We now seek to identify the mechanisms underlying this hypoglycemia. Within the first hours following injection, while still normoglycemic, lymphopenia and pro-inflammatory cytokine secretion were observed, particularly tumor necrosis factor (TNF)-α. The cytokine response evolved over the next day into a complex storm of both pro- and anti-inflammatory cytokines. Evaluation of pancreatic function and histology demonstrated marked islet hypertrophy involving predominantly β-cells, but only mildly elevated levels of insulin secretion, and diminished hepatic insulin signaling. Drops in blood glucose were observed even after destruction of β-cells with streptozotocin. In the liver, we observed a rapid and persistent decrease in the expression of glucose-6-phosphatase (G6Pase) RNA and protein levels, accompanied by a drop in glucose-6-phosphate and increase in glycogen. TNF-α has previously been reported to suppress G6Pase expression. In humans, a genetic deficiency of G6Pase results in glycogen storage disease, type-I (GSD-1), a hallmark of which is potentially fatal hypoglycemia.
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8
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Lu JQ, Wong KB, Shaw PC. A Sixty-Year Research and Development of Trichosanthin, a Ribosome-Inactivating Protein. Toxins (Basel) 2022; 14:toxins14030178. [PMID: 35324675 PMCID: PMC8950148 DOI: 10.3390/toxins14030178] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 02/23/2022] [Accepted: 02/25/2022] [Indexed: 02/04/2023] Open
Abstract
Tian Hua Fen, a herbal powder extract that contains trichosanthin (TCS), was used as an abortifacient in traditional Chinese medicine. In 1972, TCS was purified to alleviate the side effects. Because of its clinical applications, TCS became one of the most active research areas in the 1960s to the 1980s in China. These include obtaining the sequence information in the 1980s and the crystal structure in 1995. The replication block of TCS on human immunodeficiency virus in lymphocytes and macrophages was found in 1989 and started a new chapter of its development. Clinical studies were subsequently conducted. TCS was also found to have the potential for gastric and colorectal cancer treatment. Studies on its mechanism showed TCS acts as an rRNA N-glycosylase (EC 3.2.2.22) by hydrolyzing and depurinating A-4324 in α-sarcin/ricin loop on 28S rRNA of rat ribosome. Its interaction with acidic ribosomal stalk proteins was revealed in 2007, and its trafficking in mammalian cells was elucidated in the 2000s. The adverse drug reactions, such as inducing immune responses, short plasma half-life, and non-specificity, somehow became the obstacles to its usage. Immunotoxins, sequence modification, or coupling with polyethylene glycerol and dextran were developed to improve the pharmacological properties. TCS has nicely shown the scientific basis of traditional Chinese medicine and how its research and development have expanded the knowledge and applications of ribosome-inactivating proteins.
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Affiliation(s)
- Jia-Qi Lu
- Centre for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, China; (J.-Q.L.); (K.-B.W.)
| | - Kam-Bo Wong
- Centre for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, China; (J.-Q.L.); (K.-B.W.)
| | - Pang-Chui Shaw
- Centre for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, China; (J.-Q.L.); (K.-B.W.)
- Li Dak Sum Yip Yio Chin R&D Centre for Chinese Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, China
- Correspondence:
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9
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Czajka TF, Vance DJ, Davis S, Rudolph MJ, Mantis NJ. Single-domain antibodies neutralize ricin toxin intracellularly by blocking access to ribosomal P-stalk proteins. J Biol Chem 2022; 298:101742. [PMID: 35182523 PMCID: PMC8941211 DOI: 10.1016/j.jbc.2022.101742] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 02/10/2022] [Accepted: 02/14/2022] [Indexed: 12/27/2022] Open
Abstract
During ricin intoxication in mammalian cells, ricin's enzymatic (RTA) and binding (RTB) subunits disassociate in the endoplasmic reticulum. RTA is then translocated into the cytoplasm where, by virtue of its ability to depurinate a conserved residue within the sarcin-ricin loop (SRL) of 28S rRNA, it functions as a ribosome-inactivating protein. It has been proposed that recruitment of RTA to the SRL is facilitated by ribosomal P-stalk proteins, whose C-terminal domains interact with a cavity on RTA normally masked by RTB; however, evidence that this interaction is critical for RTA activity within cells is lacking. Here, we characterized a collection of single-domain antibodies (VHHs) whose epitopes overlap with the P-stalk binding pocket on RTA. The crystal structures of three such VHHs (V9E1, V9F9, and V9B2) in complex with RTA revealed not only occlusion of the ribosomal P-stalk binding pocket but also structural mimicry of C-terminal domain peptides by complementarity-determining region 3. In vitro assays confirmed that these VHHs block RTA-P-stalk peptide interactions and protect ribosomes from depurination. Moreover, when expressed as "intrabodies," these VHHs rendered cells resistant to ricin intoxication. One VHH (V9F6), whose epitope was structurally determined to be immediately adjacent to the P-stalk binding pocket, was unable to neutralize ricin within cells or protect ribosomes from RTA in vitro. These findings are consistent with the recruitment of RTA to the SRL by ribosomal P-stalk proteins as a requisite event in ricin-induced ribosome inactivation.
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Affiliation(s)
- Timothy F Czajka
- Department of Biomedical Sciences, University at Albany, Albany, New York, USA
| | - David J Vance
- Department of Biomedical Sciences, University at Albany, Albany, New York, USA; Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Simon Davis
- New York Structural Biology Center, New York, New York, USA
| | | | - Nicholas J Mantis
- Department of Biomedical Sciences, University at Albany, Albany, New York, USA; Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, New York, USA.
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10
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Li XP, Harijan RK, Cao B, Kahn JN, Pierce M, Tsymbal AM, Roberge JY, Augeri D, Tumer NE. Synthesis and Structural Characterization of Ricin Inhibitors Targeting Ribosome Binding Using Fragment-Based Methods and Structure-Based Design. J Med Chem 2021; 64:15334-15348. [PMID: 34648707 PMCID: PMC10704857 DOI: 10.1021/acs.jmedchem.1c01370] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ricin toxin A subunit (RTA) is the catalytic subunit of ricin, which depurinates an adenine from the sarcin/ricin loop in eukaryotic ribosomes. There are no approved inhibitors against ricin. We used a new strategy to disrupt RTA-ribosome interactions by fragment screening using surface plasmon resonance. Here, using a structure-guided approach, we improved the affinity and inhibitory activity of small-molecular-weight lead compounds and obtained improved compounds with over an order of magnitude higher efficiency. Four advanced compounds were characterized by X-ray crystallography. They bind at the RTA-ribosome binding site as the original compound but in a distinctive manner. These inhibitors bind remotely from the catalytic site and cause local conformational changes with no alteration of the catalytic site geometry. Yet they inhibit depurination by ricin holotoxin and inhibit the cytotoxicity of ricin in mammalian cells. They are the first agents that protect against ricin holotoxin by acting directly on RTA.
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Affiliation(s)
- Xiao-Ping Li
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 08901, United States
| | - Rajesh K Harijan
- Department of Biochemistry, Albert Einstein College of Medicine, Jack and Pearl Resnick Campus, 1300 Morris Park Avenue, Bronx, New York 10461, United States
| | - Bin Cao
- Molecular Design and Synthesis Core, Rutgers University Biomolecular Innovations Cores, Office for Research, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
| | - Jennifer N Kahn
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 08901, United States
| | - Michael Pierce
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 08901, United States
| | - Anastasiia M Tsymbal
- Molecular Design and Synthesis Core, Rutgers University Biomolecular Innovations Cores, Office for Research, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
| | - Jacques Y Roberge
- Molecular Design and Synthesis Core, Rutgers University Biomolecular Innovations Cores, Office for Research, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
| | - David Augeri
- Molecular Design and Synthesis Core, Rutgers University Biomolecular Innovations Cores, Office for Research, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
| | - Nilgun E Tumer
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 08901, United States
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11
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Das S, Roy B, Chakrabarty S. Non-ribosomal insights into ribosomal P2 protein in Plasmodium falciparum-infected erythrocytes. Microbiologyopen 2021; 10:e1188. [PMID: 34459544 PMCID: PMC8380560 DOI: 10.1002/mbo3.1188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 04/10/2021] [Indexed: 11/12/2022] Open
Abstract
The enormous complexity of the eukaryotic ribosome has been a real challenge in unlocking the mechanistic aspects of its amazing molecular function during mRNA translation and many non‐canonical activities of ribosomal proteins in eukaryotic cells. While exploring the uncanny nature of ribosomal P proteins in malaria parasites Plasmodium falciparum, the 60S stalk ribosomal P2 protein has been shown to get exported to the infected erythrocyte (IE) surface as an SDS‐resistant oligomer during the early to the mid‐trophozoite stage. Inhibiting IE surface P2 either by monoclonal antibody or through genetic knockdown resulted in nuclear division arrest of the parasite. This strange and serendipitous finding has led us to explore more about un‐canonical cell biology and the structural involvement of P2 protein in Plasmodium in the search for a novel biochemical role during parasite propagation in the human host.
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Affiliation(s)
- Sudipta Das
- Asymmetric Cell Division Laboratory, Division of Infectious Disease and Immunology, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Bhaskar Roy
- Asymmetric Cell Division Laboratory, Division of Infectious Disease and Immunology, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Saswata Chakrabarty
- Asymmetric Cell Division Laboratory, Division of Infectious Disease and Immunology, CSIR-Indian Institute of Chemical Biology, Kolkata, India
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12
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Horbowicz-Drożdżal P, Kamel K, Kmiecik S, Borkiewicz L, Tumer NE, Shaw PC, Tchórzewski M, Grela P. Phosphorylation of the conserved C-terminal domain of ribosomal P-proteins impairs the mode of interaction with plant toxins. FEBS Lett 2021; 595:2221-2236. [PMID: 34328639 DOI: 10.1002/1873-3468.14170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 07/14/2021] [Accepted: 07/21/2021] [Indexed: 11/12/2022]
Abstract
The ribosome is subjected to post-translational modifications, including phosphorylation, that affect its biological activity. Among ribosomal elements, the P-proteins undergo phosphorylation within the C terminus, the element which interacts with trGTPases or ribosome-inactivating proteins (RIPs); however, the role of phosphorylation has never been elucidated. Here, we probed the function of phosphorylation on the interaction of P-proteins with RIPs using the ribosomal P1-P2 dimer. We determined the kinetic parameters of the interaction with the toxins using biolayer interferometry and microscale thermophoresis. The results present the first mechanistic insight into the function of P-protein phosphorylation, showing that introduction of a negative charge into the C terminus of P1-P2 proteins promotes α-helix formation and decreases the affinity of the P-proteins for the RIPs.
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Affiliation(s)
- Patrycja Horbowicz-Drożdżal
- Department of Molecular Biology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Lublin, Poland
| | - Karol Kamel
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznań, Poland
| | - Sebastian Kmiecik
- Biological and Chemical Research Centre, Faculty of Chemistry, University of Warsaw, Poland
| | - Lidia Borkiewicz
- Department of Biochemistry and Molecular Biology, Medical University of Lublin, Poland
| | - Nilgun E Tumer
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ, USA
| | - Pang-Chui Shaw
- School of Life Sciences, The Chinese University of Hong Kong, China
| | - Marek Tchórzewski
- Department of Molecular Biology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Lublin, Poland
| | - Przemysław Grela
- Department of Molecular Biology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Lublin, Poland
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13
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Rudolph MJ, Davis SA, Tumer NE, Li XP. Structural basis for the interaction of Shiga toxin 2a with a C-terminal peptide of ribosomal P stalk proteins. J Biol Chem 2020; 295:15588-15596. [PMID: 32878986 PMCID: PMC7667979 DOI: 10.1074/jbc.ac120.015070] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 08/28/2020] [Indexed: 01/07/2023] Open
Abstract
The principal virulence factor of human pathogenic enterohemorrhagic Escherichia coli is Shiga toxin (Stx). Shiga toxin 2a (Stx2a) is the subtype most commonly associated with severe disease outcomes such as hemorrhagic colitis and hemolytic uremic syndrome. The catalytic A1 subunit (Stx2A1) binds to the conserved elongation factor binding C-terminal domain (CTD) of ribosomal P stalk proteins to inhibit translation. Stx2a holotoxin also binds to the CTD of P stalk proteins because the ribosome-binding site is exposed. We show here that Stx2a binds to an 11-mer peptide (P11) mimicking the CTD of P stalk proteins with low micromolar affinity. We cocrystallized Stx2a with P11 and defined their interactions by X-ray crystallography. We found that the last six residues of P11 inserted into a shallow pocket on Stx2A1 and interacted with Arg-172, Arg-176, and Arg-179, which were previously shown to be critical for binding of Stx2A1 to the ribosome. Stx2a formed a distinct P11-binding mode within a different surface pocket relative to ricin toxin A subunit and trichosanthin, suggesting different ribosome recognition mechanisms for each ribosome inactivating protein (RIP). The binding mode of Stx2a to P11 is also conserved among the different Stx subtypes. Furthermore, the P stalk protein CTD is flexible and adopts distinct orientations and interaction modes depending on the structural differences between the RIPs. Structural characterization of the Stx2a-ribosome complex is important for understanding the role of the stalk in toxin recruitment to the sarcin/ricin loop and may provide a new target for inhibitor discovery.
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Affiliation(s)
| | - Simon A. Davis
- New York Structural Biology Center, New York, New York, USA
| | - Nilgun E. Tumer
- Department of Plant Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA,For correspondence: Xiao-Ping Li, ; Nilgun E. Tumer,
| | - Xiao-Ping Li
- Department of Plant Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA,For correspondence: Xiao-Ping Li, ; Nilgun E. Tumer,
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14
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Filipek K, Michalec-Wawiórka B, Boguszewska A, Kmiecik S, Tchórzewski M. Phosphorylation of the N-terminal domain of ribosomal P-stalk protein uL10 governs its association with the ribosome. FEBS Lett 2020; 594:3002-3019. [PMID: 32668052 DOI: 10.1002/1873-3468.13885] [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: 03/16/2020] [Revised: 07/07/2020] [Accepted: 07/07/2020] [Indexed: 12/25/2022]
Abstract
The uL10 protein is the main constituent of the ribosomal P-stalk, anchoring the whole stalk to the ribosome through interactions with rRNA. The P-stalk is the core of the GTPase-associated center (GAC), a critical element for ribosome biogenesis and ribosome translational activity. All P-stalk proteins (uL10, P1, and P2) undergo phosphorylation within their C termini. Here, we show that uL10 has multiple phosphorylation sites, mapped also within the N-terminal rRNA-binding domain. Our results reveal that the introduction of a negative charge within the N terminus of uL10 impairs its association with the ribosome. These findings demonstrate that uL10 N-terminal phosphorylation has regulatory potential governing the uL10 interaction with the ribosome and may control the activity of GAC.
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Affiliation(s)
- Kamil Filipek
- Department of Molecular Biology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Lublin, Poland
| | - Barbara Michalec-Wawiórka
- Department of Molecular Biology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Lublin, Poland
| | - Aleksandra Boguszewska
- Department of Molecular Biology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Lublin, Poland
| | - Sebastian Kmiecik
- Biological and Chemical Research Centre, Faculty of Chemistry, University of Warsaw, Warsaw, Poland
| | - Marek Tchórzewski
- Department of Molecular Biology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Lublin, Poland
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15
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Li XP, Harijan RK, Kahn JN, Schramm VL, Tumer NE. Small Molecule Inhibitors Targeting the Interaction of Ricin Toxin A Subunit with Ribosomes. ACS Infect Dis 2020; 6:1894-1905. [PMID: 32428396 DOI: 10.1021/acsinfecdis.0c00127] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Ricin toxin A subunit (RTA) removes an adenine from the universally conserved sarcin/ricin loop (SRL) on eukaryotic ribosomes, thereby inhibiting protein synthesis. No high affinity and selective small molecule therapeutic antidotes have been reported against ricin toxicity. RTA binds to the ribosomal P stalk to access the SRL. The interaction anchors RTA to the P protein C-termini at a well-defined hydrophobic pocket, which is on the opposite face relative to the active site. The RTA ribosome binding site has not been previously targeted by small molecule inhibitors. We used fragment screening with surface plasmon resonance to identify small molecular weight lead compounds that bind RTA and defined their interactions by crystallography. We identified five fragments, which bound RTA with mid-micromolar affinity. Three chemically distinct binding fragments were cocrystallized with RTA, and crystal structures were solved. Two fragments bound at the P stalk binding site, and the third bound to helix D, a motif distinct from the P stalk binding site. All fragments bound RTA remote from the catalytic site and caused little change in catalytic site geometry. Two fragments uniquely bound at the hydrophobic pocket with affinity sufficient to inhibit the catalytic activity on eukaryotic ribosomes in the low micromolar range. The binding mode of these inhibitors mimicked the interaction of the P stalk peptide, establishing that small molecule inhibitors can inhibit RTA binding to the ribosome with the potential for therapeutic intervention.
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Affiliation(s)
- Xiao-Ping Li
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 08901, United States
| | - Rajesh K. Harijan
- Department of Biochemistry, Albert Einstein College of Medicine, Jack and Pearl Resnick Campus,1300 Morris Park Avenue, Bronx, New York 10461, United States
| | - Jennifer N. Kahn
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 08901, United States
| | - Vern L. Schramm
- Department of Biochemistry, Albert Einstein College of Medicine, Jack and Pearl Resnick Campus,1300 Morris Park Avenue, Bronx, New York 10461, United States
| | - Nilgun E. Tumer
- Department of Plant Biology, Rutgers, The State University of New Jersey, 59 Dudley Road, New Brunswick, New Jersey 08901, United States
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16
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Tumer NE. Introduction to the Toxins Special Issue "Ricin Toxins". Toxins (Basel) 2019; 12:E13. [PMID: 31892170 PMCID: PMC7020407 DOI: 10.3390/toxins12010013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 12/24/2019] [Indexed: 12/28/2022] Open
Abstract
Ricin toxin isolated from the castor bean (Ricinus communis) is one of the most potent and lethal molecules known [...].
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Affiliation(s)
- Nilgun E Tumer
- Department of Plant Biology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901-8520, USA
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17
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Szajwaj M, Wawiórka L, Molestak E, Michalec-Wawiórka B, Mołoń M, Wojda I, Tchórzewski M. The influence of ricin-mediated rRNA depurination on the translational machinery in vivo - New insight into ricin toxicity. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:118554. [DOI: 10.1016/j.bbamcr.2019.118554] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 08/10/2019] [Accepted: 09/04/2019] [Indexed: 11/29/2022]
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18
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Choi KHA, Yang L, Lee KM, Yu CWH, Banfield DK, Ito K, Uchiumi T, Wong KB. Structural and Mutagenesis Studies Evince the Role of the Extended Protuberant Domain of Ribosomal Protein uL10 in Protein Translation. Biochemistry 2019; 58:3744-3754. [PMID: 31419120 DOI: 10.1021/acs.biochem.9b00528] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The lateral stalk of ribosomes constitutes the GTPase-associated center and is responsible for recruiting translation factors to the ribosomes. The eukaryotic stalk contains a P-complex, in which one molecule of uL10 (formerly known as P0) protein binds two copies of P1/P2 heterodimers. Unlike bacterial uL10, eukaryotic uL10 has an extended protuberant (uL10ext) domain inserted into the N-terminal RNA-binding domain. Here, we determined the solution structure of the extended protuberant domain of Bombyx mori uL10 by nuclear magnetic resonance spectroscopy. Comparison of the structures of the B. mori uL10ext domain with eRF1-bound and eEF2-bound ribosomes revealed significant structural rearrangement in a "hinge" region surrounding Phe183, a residue conserved in eukaryotic but not in archaeal uL10. 15N relaxation analyses showed that residues in the hinge region have significantly large values of transverse relaxation rates. To test the role of the conserved phenylalanine residue, we created a yeast mutant strain expressing an F181A variant of uL10. An in vitro translation assay showed that the alanine substitution increased the level of polyphenylalanine synthesis by ∼33%. Taken together, our results suggest that the hinge motion of the uL10ext domain facilitates the binding of different translation factors to the GTPase-associated center during protein synthesis.
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Affiliation(s)
- Kwok-Ho Andrew Choi
- School of Life Sciences, Centre for Protein Science and Crystallography, State Key Laboratory of Agrobiotechnology , The Chinese University of Hong Kong , Shatin , Hong Kong, China
| | - Lei Yang
- School of Life Sciences, Centre for Protein Science and Crystallography, State Key Laboratory of Agrobiotechnology , The Chinese University of Hong Kong , Shatin , Hong Kong, China
| | - Ka-Ming Lee
- School of Life Sciences, Centre for Protein Science and Crystallography, State Key Laboratory of Agrobiotechnology , The Chinese University of Hong Kong , Shatin , Hong Kong, China
| | - Conny Wing-Heng Yu
- School of Life Sciences, Centre for Protein Science and Crystallography, State Key Laboratory of Agrobiotechnology , The Chinese University of Hong Kong , Shatin , Hong Kong, China
| | - David K Banfield
- Division of Life Science , Hong Kong University of Science and Technology , Clear Water Bay , Hong Kong , China
| | - Kosuke Ito
- Department of Biology, Faculty of Science , Niigata University , Ikarashi 2-8050 , Nishi-ku, Niigata 950-2191 , Japan
| | - Toshio Uchiumi
- Department of Biology, Faculty of Science , Niigata University , Ikarashi 2-8050 , Nishi-ku, Niigata 950-2191 , Japan
| | - Kam-Bo Wong
- School of Life Sciences, Centre for Protein Science and Crystallography, State Key Laboratory of Agrobiotechnology , The Chinese University of Hong Kong , Shatin , Hong Kong, China
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19
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Tanzawa T, Kato K, Girodat D, Ose T, Kumakura Y, Wieden HJ, Uchiumi T, Tanaka I, Yao M. The C-terminal helix of ribosomal P stalk recognizes a hydrophobic groove of elongation factor 2 in a novel fashion. Nucleic Acids Res 2019; 46:3232-3244. [PMID: 29471537 PMCID: PMC5887453 DOI: 10.1093/nar/gky115] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 02/09/2018] [Indexed: 01/17/2023] Open
Abstract
Archaea and eukaryotes have ribosomal P stalks composed of anchor protein P0 and aP1 homodimers (archaea) or P1•P2 heterodimers (eukaryotes). These P stalks recruit translational GTPases to the GTPase-associated center in ribosomes to provide energy during translation. The C-terminus of the P stalk is known to selectively recognize GTPases. Here we investigated the interaction between the P stalk and elongation factor 2 by determining the structures of Pyrococcus horikoshii EF-2 (PhoEF-2) in the Apo-form, GDP-form, GMPPCP-form (GTP-form), and GMPPCP-form bound with 11 C-terminal residues of P1 (P1C11). Helical structured P1C11 binds to a hydrophobic groove between domain G and subdomain G′ of PhoEF-2, where is completely different from that of aEF-1α in terms of both position and sequence, implying that such interaction characteristic may be requested by how GTPases perform their functions on the ribosome. Combining PhoEF-2 P1-binding assays with a structural comparison of current PhoEF-2 structures and molecular dynamics model of a P1C11-bound GDP form, the conformational changes of the P1C11-binding groove in each form suggest that in response to the translation process, the groove has three states: closed, open, and release for recruiting and releasing GTPases.
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Affiliation(s)
- Takehito Tanzawa
- Graduate School of Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | - Koji Kato
- Graduate School of Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.,Faculty of Advanced Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | - Dylan Girodat
- Alberta RNA Research and Training Institute, Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge AB T1K 3M4, Canada
| | - Toyoyuki Ose
- Graduate School of Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.,Faculty of Advanced Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | - Yuki Kumakura
- Graduate School of Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | - Hans-Joachim Wieden
- Alberta RNA Research and Training Institute, Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge AB T1K 3M4, Canada
| | - Toshio Uchiumi
- Department of Biology, Faculty of Science, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan
| | - Isao Tanaka
- Faculty of Advanced Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | - Min Yao
- Graduate School of Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.,Faculty of Advanced Life Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
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20
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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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21
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How Ricin Damages the Ribosome. Toxins (Basel) 2019; 11:toxins11050241. [PMID: 31035546 PMCID: PMC6562825 DOI: 10.3390/toxins11050241] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 04/17/2019] [Accepted: 04/24/2019] [Indexed: 12/20/2022] Open
Abstract
Ricin belongs to the group of ribosome-inactivating proteins (RIPs), i.e., toxins that have evolved to provide particular species with an advantage over other competitors in nature. Ricin possesses RNA N-glycosidase activity enabling the toxin to eliminate a single adenine base from the sarcin-ricin RNA loop (SRL), which is a highly conserved structure present on the large ribosomal subunit in all species from the three domains of life. The SRL belongs to the GTPase associated center (GAC), i.e., a ribosomal element involved in conferring unidirectional trajectory for the translational apparatus at the expense of GTP hydrolysis by translational GTPases (trGTPases). The SRL represents a critical element in the GAC, being the main triggering factor of GTP hydrolysis by trGTPases. Enzymatic removal of a single adenine base at the tip of SRL by ricin blocks GTP hydrolysis and, at the same time, impedes functioning of the translational machinery. Here, we discuss the consequences of SRL depurination by ricin for ribosomal performance, with emphasis on the mechanistic model overview of the SRL modus operandi.
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22
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Zhou Y, Li XP, Kahn JN, Tumer NE. Functional Assays for Measuring the Catalytic Activity of Ribosome Inactivating Proteins. Toxins (Basel) 2018; 10:toxins10060240. [PMID: 29899209 PMCID: PMC6024586 DOI: 10.3390/toxins10060240] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 06/01/2018] [Accepted: 06/07/2018] [Indexed: 12/11/2022] Open
Abstract
Ribosome-inactivating proteins (RIPs) are potent toxins that inactivate ribosomes by catalytically removing a specific adenine from the α-sarcin/ricin loop (SRL) of the large rRNA. Direct assays for measuring depurination activity and indirect assays for measuring the resulting translation inhibition have been employed to determine the enzyme activity of RIPs. Rapid and sensitive methods to measure the depurination activity of RIPs are critical for assessing their reaction mechanism, enzymatic properties, interaction with ribosomal proteins, ribotoxic stress signaling, in the search for inhibitors and in the detection and diagnosis of enteric infections. Here, we review the major assays developed for measuring the catalytic activity of RIPs, discuss their advantages and disadvantages and explain how they are used in understanding the catalytic mechanism, ribosome specificity, and dynamic enzymatic features of RIPs.
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Affiliation(s)
- Yijun Zhou
- Department of Plant Biology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901-8520, USA.
| | - Xiao-Ping Li
- Department of Plant Biology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901-8520, USA.
| | - Jennifer N Kahn
- Department of Plant Biology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901-8520, USA.
| | - Nilgun E Tumer
- Department of Plant Biology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901-8520, USA.
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