1
|
Czajka TF, Vance DJ, Song R, Mantis NJ. A Biparatopic Intrabody Renders Vero Cells Impervious to Ricin Intoxication. Biochemistry 2024; 63:2391-2396. [PMID: 39297955 DOI: 10.1021/acs.biochem.4c00385] [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: 09/25/2024]
Abstract
Expression of camelid-derived, single-domain antibodies (VHHs) within the cytoplasm of mammalian cells as "intrabodies" has opened up novel avenues for medical countermeasures against fast-acting biothreat agents. In this report, we describe a heterodimeric intrabody that renders Vero cells virtually impervious to ricin toxin (RT), a potent Category B ribosome-inactivating protein. The intrabody consists of two structurally defined VHHs that target distinct epitopes on RT's enzymatic subunit (RTA): V9E1 targets RTA's P-stalk recruitment site, and V2A11 targets RTA's active site. Resistance to RT conferred by the biparatopic VHH construct far exceeded that of either of the VHHs alone and effectively inhibited all measurable RT-induced cytotoxicity in vitro. We propose that the targeted delivery of bispecific intrabodies to lung tissues may represent a novel means to shield the airways from the effects of inhalational RT exposure.
Collapse
Affiliation(s)
- Timothy F Czajka
- Department of Biomedical Sciences, University at Albany, Albany, New York 12201, United States
| | - David J Vance
- Department of Biomedical Sciences, University at Albany, Albany, New York 12201, United States
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States of America
| | - Renji Song
- Division of Research, Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States of America
| | - Nicholas J Mantis
- Department of Biomedical Sciences, University at Albany, Albany, New York 12201, United States
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States of America
| |
Collapse
|
2
|
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 PMCID: PMC11418909 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] [Grants] [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.
Collapse
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.
| |
Collapse
|
3
|
Strader MB, Saha AL, Fernandes C, Sharma K, Hadiwinarta C, Calheiros D, Conde-de-Oliveira G, Gonçalves T, Slater JE. Distinct proteomes and allergen profiles appear across the life-cycle stages of Alternaria alternata. J Allergy Clin Immunol 2024; 154:424-434. [PMID: 38663817 DOI: 10.1016/j.jaci.2024.03.026] [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: 09/28/2023] [Revised: 03/01/2024] [Accepted: 03/20/2024] [Indexed: 05/26/2024]
Abstract
BACKGROUND Alternaria alternata is associated with allergic respiratory diseases, which can be managed with allergen extract-based diagnostics and immunotherapy. It is not known how spores and hyphae contribute to allergen content. Commercial allergen extracts are manufactured by extracting proteins without separating the different forms of the fungus. OBJECTIVE We sought to determine differences between spore and hyphae proteomes and how allergens are distributed in Aalternata. METHODS Data-independent acquisition mass spectrometry was used to quantitatively compare the proteomes of asexual spores (nongerminating and germinating) with vegetative hyphae. RESULTS We identified 4515 proteins in nongerminating spores, germinating spores, and hyphae; most known allergens are more abundant in nongerminating spores. On comparing significant protein fold-change differences between nongerminating spores and hyphae, we found that 174 proteins were upregulated in nongerminating spores and 80 proteins in hyphae. Among the spore proteins are ones functionally involved in cell wall synthesis, responding to cellular stress, and maintaining redox balance and homeostasis. On comparing nongerminating and germinating spores, 25 proteins were found to be upregulated in nongerminating spores and 54 in germinating spores. Among the proteins specific to germinating spores were proteases known to be virulence factors. One of the most abundant proteins in the spore proteome is sialidase, which has not been identified as an allergen but may be important in the pathogenicity of this fungus. Major allergen Alt a 1 is present at low levels in spores and hyphae and appears to be largely secreted into growth media. CONCLUSIONS Spores and hyphae express overlapping but distinct proteomes. Most known allergens are found more abundantly in nongerminating spores.
Collapse
Affiliation(s)
- Michael Brad Strader
- Laboratory of Immunobiochemistry, Division of Bacterial, Parasitic and Allergenic Products, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, US Food and Drug Administration, Silver Spring, Md.
| | - Aishwarya L Saha
- Laboratory of Immunobiochemistry, Division of Bacterial, Parasitic and Allergenic Products, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, US Food and Drug Administration, Silver Spring, Md
| | - Chantal Fernandes
- University of Coimbra, CNC-UC - Center for Neuroscience and Cell Biology, FMUC - Faculty of Medicine of the University of Coimbra, Coimbra, Portugal
| | - Kavita Sharma
- Laboratory of Immunobiochemistry, Division of Bacterial, Parasitic and Allergenic Products, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, US Food and Drug Administration, Silver Spring, Md
| | - Christian Hadiwinarta
- Laboratory of Immunobiochemistry, Division of Bacterial, Parasitic and Allergenic Products, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, US Food and Drug Administration, Silver Spring, Md
| | - Daniela Calheiros
- University of Coimbra, CNC-UC - Center for Neuroscience and Cell Biology, FMUC - Faculty of Medicine of the University of Coimbra, Coimbra, Portugal
| | - Gonçalo Conde-de-Oliveira
- University of Coimbra, CNC-UC - Center for Neuroscience and Cell Biology, FMUC - Faculty of Medicine of the University of Coimbra, Coimbra, Portugal
| | - Teresa Gonçalves
- University of Coimbra, CNC-UC - Center for Neuroscience and Cell Biology, FMUC - Faculty of Medicine of the University of Coimbra, Coimbra, Portugal
| | - Jay E Slater
- Laboratory of Immunobiochemistry, Division of Bacterial, Parasitic and Allergenic Products, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, US Food and Drug Administration, Silver Spring, Md
| |
Collapse
|
4
|
Czajka TF, Vance DJ, Song R, Mantis NJ. A Biparatopic Intrabody Renders Vero Cells Impervious to Ricin Intoxication. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.02.601761. [PMID: 39005371 PMCID: PMC11244990 DOI: 10.1101/2024.07.02.601761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Expression of camelid-derived, single-domain antibodies (VHHs) within the cytoplasm of mammalian cells as "intrabodies" has opened-up novel avenues for medical countermeasures against fast-acting biothreat agents. In this report, we describe a heterodimeric intrabody that renders Vero cells virtually impervious to ricin toxin (RT), a potent Category B ribosome-inactivating protein (RIP). The intrabody consists of two structurally defined VHHs that target distinct epitopes on RT's enzymatic subunit (RTA): V9E1 targets RTA's P-stalk recruitment site, and V2A11 targets RTA's active site. Resistance to RT conferred by the biparatopic VHH construct far exceeded that of either of the VHHs alone and effectively inhibited all measurable RT-induced cytotoxicty in vitro. We propose that targeted delivery of bispecific intrabodies to lung tissues may represent a novel means to shield the airways from the effects of inhalational RT exposure.
Collapse
Affiliation(s)
- Timothy F. Czajka
- Department of Biomedical Sciences, University at Albany, Albany, NY 12201 United States
| | - David J. Vance
- Department of Biomedical Sciences, University at Albany, Albany, NY 12201 United States
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, 12208
| | - Renji Song
- Division of Research, Wadsworth Center, New York State Department of Health, Albany, NY, 12208
| | - Nicholas J. Mantis
- Department of Biomedical Sciences, University at Albany, Albany, NY 12201 United States
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, 12208
| |
Collapse
|
5
|
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 PMCID: PMC11418912 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] [Grants] [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.
Collapse
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.
| |
Collapse
|
6
|
Dougherty K, Hudak KA. Phylogeny and domain architecture of plant ribosome inactivating proteins. PHYTOCHEMISTRY 2022; 202:113337. [PMID: 35934106 DOI: 10.1016/j.phytochem.2022.113337] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 07/01/2022] [Accepted: 07/20/2022] [Indexed: 06/15/2023]
Abstract
Ribosome inactivating proteins (RIPs) are rRNA N-glycosylases (EC 3.2.2.22) best known for hydrolyzing an adenine base from the conserved sarcin/ricin loop of ribosomal RNA. Protein translation is inhibited by ribosome depurination; therefore, RIPs are generally considered toxic to cells. The expression of some RIPs is upregulated by biotic and abiotic stress, though the connection between RNA depurination and defense response is not well understood. Despite their prevalence in approximately one-third of flowering plant orders, our knowledge of RIPs stems primarily from biochemical analyses of individuals or genomics-scale analyses of small datasets from a limited number of species. Here, we performed an unbiased search for proteins with RIP domains and identified several-fold more RIPs than previously known - more than 800 from 120 species, many with novel associated domains and physicochemical characteristics. Based on protein domain configuration, we established 15 distinct groups, suggesting diverse functionality. Surprisingly, most of these RIPs lacked a signal peptide, indicating they may be localized to the nucleocytoplasm of cells, raising questions regarding their toxicity against conspecific ribosomes. Our phylogenetic analysis significantly extends previous models for RIP evolution in plants, predicting an original single-domain RIP that later evolved to acquire a signal peptide and different protein domains. We show that RIPs are distributed throughout 21 plant orders with many species maintaining genes for more than one RIP group. Our analyses provide the foundation for further characterization of these new RIP types, to understand how these enzymes function in plants.
Collapse
Affiliation(s)
- Kyra Dougherty
- Department of Biology, York University, Toronto, Canada.
| | | |
Collapse
|
7
|
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.
Collapse
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.
| |
Collapse
|
8
|
Abstract
Ricin is a plant-derived toxin with a history as a biothreat agent. The toxin's enzymatic subunit, ricin toxin A chain (RTA), is a ribosome-inactivating protein that, when delivered into the cytoplasm of mammalian cells, arrests protein synthesis with extraordinary efficiency. Once within the cytoplasm, RTA is shielded from circulating toxin-neutralizing antibodies. Here, we describe methods we developed to neutralize RTA within the cytoplasm of Vero cells using DNA-based delivery of alpaca-derived single-domain antibodies (VHHs) targeting RTA's active site. We describe the design of the VHH expression vectors, assessment of transient expression of VHHs in Vero cells by enzyme-linked immunosorbent assay and western blotting, and cytotoxicity studies. While the protocols here are specific to ricin, they are easily modified for other toxins or even intracellular pathogens such as viruses.
Collapse
Affiliation(s)
- Timothy F Czajka
- Department of Biomedical Sciences, University at Albany School of Public Health, Albany, NY, USA
| | - Nicholas J Mantis
- Department of Biomedical Sciences, University at Albany School of Public Health, Albany, NY, USA.
- Division of Infectious Diseases, New York State Department of Health, Wadsworth Center, Albany, NY, USA.
| |
Collapse
|
9
|
Pathanraj D, Choowongkomon K, Roytrakul S, Yokthongwattana C. Structural Distinctive 26SK, a Ribosome-Inactivating Protein from Jatropha curcas and Its Biological Activities. Appl Biochem Biotechnol 2021; 193:3877-3897. [PMID: 34669111 DOI: 10.1007/s12010-021-03714-6] [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: 07/12/2021] [Accepted: 10/08/2021] [Indexed: 11/28/2022]
Abstract
Ribosome-inactivating proteins (RIPs) are a group of proteins exhibiting N-glycosidase activity leading to an inactivation of protein synthesis. Thirteen predicted Jatropha curcas RIP sequences could be grouped into RIP types 1 or 2. The expression of the RIP genes was detected in seed kernels, seed coats, and leaves. The full-length cDNA of two RIP genes (26SK and 34.7(A)SK) were cloned and studied. The 34.7(A)SK protein was successfully expressed in the host cells while it was difficult to produce even only a small amount of the 26SK protein. Therefore, the crude proteins were used from E. coli expressing 26SK and 34.7(A)SK constructs and they showed RIP activity. Only the cell lysate from 26SK could inhibit the growth of E. coli. In addition, the crude protein extracted from 26SK expressing cells displayed the effect on the growth of MDA-MB-231, a human breast cancer cell line. Based on in silico analysis, all 13 J. curcas RIPs contained RNA and ribosomal P2 stalk protein binding sites; however, the C-terminal region of the P2 stalk binding site was lacking in the 26SK structure. In addition, an amphipathic distribution between positive and negative potential was observed only in the 26SK protein, similar to that found in the anti-microbial peptide. These findings suggested that this 26SK protein structure might have contributed to its toxicity, suggesting potential uses against pathogenic bacteria in the future.
Collapse
Affiliation(s)
- Danulada Pathanraj
- Interdisciplinary Program in Genetic Engineering, Graduate School, Kasetsart University, 50 Ngamwongwan Rd., Bangkok, 10900, Thailand
| | - Kiattawee Choowongkomon
- Department of Biochemistry, Faculty of Science, Kasetsart University, 50 Ngamwongwan Rd., Bangkok, 10900, Thailand
| | - Sittiruk Roytrakul
- Functional Ingredients and Food Innovation Research Group, National Center for Genetic Engineering and Biotechnology, Pathum Thani, 12120, Thailand
| | - Chotika Yokthongwattana
- Department of Biochemistry, Faculty of Science, Kasetsart University, 50 Ngamwongwan Rd., Bangkok, 10900, Thailand.
| |
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
Dong HJ, Zhang R, Kuang Y, Wang XJ. Selective regulation in ribosome biogenesis and protein production for efficient viral translation. Arch Microbiol 2020; 203:1021-1032. [PMID: 33124672 PMCID: PMC7594972 DOI: 10.1007/s00203-020-02094-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 09/18/2020] [Accepted: 10/13/2020] [Indexed: 11/25/2022]
Abstract
As intracellular parasites, viruses depend heavily on host cell structures and their functions to complete their life cycle and produce new viral particles. Viruses utilize or modulate cellular translational machinery to achieve efficient replication; the role of ribosome biogenesis and protein synthesis in viral replication particularly highlights the importance of the ribosome quantity and/or quality in controlling viral protein synthesis. Recently reported studies have demonstrated that ribosome biogenesis factors (RBFs) and ribosomal proteins (RPs) act as multifaceted regulators in selective translation of viral transcripts. Here we summarize the recent literature on RBFs and RPs and their association with subcellular redistribution, post-translational modification, enzyme catalysis, and direct interaction with viral proteins. The advances described in this literature establish a rationale for targeting ribosome production and function in the design of the next generation of antiviral agents.
Collapse
Affiliation(s)
- Hui-Jun Dong
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Rui Zhang
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
| | - Yu Kuang
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
| | - Xiao-Jia Wang
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
| |
Collapse
|
12
|
Leucine 232 and hydrophobic residues at the ribosomal P stalk binding site are critical for biological activity of ricin. Biosci Rep 2020; 39:BSR20192022. [PMID: 31548364 PMCID: PMC6822507 DOI: 10.1042/bsr20192022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 08/15/2019] [Accepted: 08/21/2019] [Indexed: 01/16/2023] Open
Abstract
Ricin interacts with the ribosomal P stalk to cleave a conserved adenine from the α-sarcin/ricin loop (SRL) of the rRNA. Ricin toxin A chain (RTA) uses Arg235 as the most critical arginine for binding to the P stalk through electrostatic interactions to facilitate depurination. Structural analysis showed that a P2 peptide binds to a hydrophobic pocket on RTA and the last two residues form hydrogen bonds with Arg235. The importance of hydrophobic residues relative to Arg235 in the interaction with the P stalk in vivo and on the toxicity of RTA is not known. Here, we mutated residues in the hydrophobic pocket to analyze their contribution to toxicity and depurination activity in yeast and in mammalian cells. We found that Leu232, Tyr183 and Phe240 contribute cumulatively to toxicity, with Leu232 being the most significant. A quadruple mutant, Y183A/L232A/R235A/F240A, which combined mutations in critical hydrophobic residues with R235A completely abolished the activity of RTA, indicating that Arg235 and hydrophobic residues are required for full biological activity. Y183A and F240A mutants had reduced activity on RNA, but higher activity on ribosomes compared with R235A in vitro, suggesting that they could partially regain activity upon interaction with ribosomes. These results expand the region of interaction between RTA and the P stalk critical for cellular activity to include the hydrophobic pocket and provide the first evidence that interaction of P stalk with the hydrophobic pocket promotes a conformational rearrangement of RTA to correctly position the active site residues for catalytic attack on the SRL.
Collapse
|
13
|
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.
Collapse
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
| |
Collapse
|
14
|
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 [...].
Collapse
Affiliation(s)
- Nilgun E Tumer
- Department of Plant Biology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901-8520, USA
| |
Collapse
|
15
|
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]
|
16
|
Johnson AG, Lapointe CP, Wang J, Corsepius NC, Choi J, Fuchs G, Puglisi JD. RACK1 on and off the ribosome. RNA (NEW YORK, N.Y.) 2019; 25:881-895. [PMID: 31023766 PMCID: PMC6573788 DOI: 10.1261/rna.071217.119] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 04/21/2019] [Indexed: 05/17/2023]
Abstract
Receptor for activated C kinase 1 (RACK1) is a eukaryote-specific ribosomal protein (RP) implicated in diverse biological functions. To engineer ribosomes for specific fluorescent labeling, we selected RACK1 as a target given its location on the small ribosomal subunit and other properties. However, prior results suggested that RACK1 has roles both on and off the ribosome, and such an exchange might be related to its various cellular functions and hinder our ability to use RACK1 as a stable fluorescent tag for the ribosome. In addition, the kinetics of spontaneous exchange of RACK1 or any RP from a mature ribosome in vitro remain unclear. To address these issues, we engineered fluorescently labeled human ribosomes via RACK1, and applied bulk and single-molecule biochemical analyses to track RACK1 on and off the human ribosome. Our results demonstrate that, despite its cellular nonessentiality from yeast to humans, RACK1 readily reassociates with the ribosome, displays limited conformational dynamics, and remains stably bound to the ribosome for hours in vitro. This work sheds insight into the biochemical basis of RPs exchange on and off a mature ribosome and provides tools for single-molecule analysis of human translation.
Collapse
Affiliation(s)
- Alex G Johnson
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Christopher P Lapointe
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Jinfan Wang
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Nicholas C Corsepius
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Junhong Choi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Gabriele Fuchs
- The RNA Institute, Department of Biological Sciences, University of Albany, Albany, New York 12222, USA
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
| |
Collapse
|
17
|
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.
Collapse
|
18
|
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.
Collapse
|
19
|
Li XP, Kahn JN, Tumer NE. Peptide Mimics of the Ribosomal P Stalk Inhibit the Activity of Ricin A Chain by Preventing Ribosome Binding. Toxins (Basel) 2018; 10:E371. [PMID: 30217009 PMCID: PMC6162817 DOI: 10.3390/toxins10090371] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 09/07/2018] [Accepted: 09/10/2018] [Indexed: 11/27/2022] Open
Abstract
Ricin A chain (RTA) depurinates the sarcin/ricin loop (SRL) by interacting with the C-termini of the ribosomal P stalk. The ribosome interaction site and the active site are located on opposite faces of RTA. The interaction with P proteins allows RTA to depurinate the SRL on the ribosome at physiological pH with an extremely high activity by orienting the active site towards the SRL. Therefore, if an inhibitor disrupts RTA⁻ribosome interaction by binding to the ribosome binding site of RTA, it should inhibit the depurination activity. To test this model, we synthesized peptides mimicking the last 3 to 11 amino acids of P proteins and examined their interaction with wild-type RTA and ribosome binding mutants by Biacore. We measured the inhibitory activity of these peptides on RTA-mediated depurination of yeast and rat liver ribosomes. We found that the peptides interacted with the ribosome binding site of RTA and inhibited depurination activity by disrupting RTA⁻ribosome interactions. The shortest peptide that could interact with RTA and inhibit its activity was four amino acids in length. RTA activity was inhibited by disrupting its interaction with the P stalk without targeting the active site, establishing the ribosome binding site as a new target for inhibitor discovery.
Collapse
Affiliation(s)
- Xiao-Ping Li
- Department of Plant Biology, School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901-8520, USA.
| | - Jennifer N Kahn
- Department of Plant Biology, School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901-8520, USA.
| | - Nilgun E Tumer
- Department of Plant Biology, School of Environmental and Biological Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901-8520, USA.
| |
Collapse
|
20
|
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.
Collapse
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.
| |
Collapse
|
21
|
Human ribosomal P1-P2 heterodimer represents an optimal docking site for ricin A chain with a prominent role for P1 C-terminus. Sci Rep 2017; 7:5608. [PMID: 28717148 PMCID: PMC5514047 DOI: 10.1038/s41598-017-05675-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 06/15/2017] [Indexed: 12/26/2022] Open
Abstract
The eukaryotic P-stalk contains two P1-P2 protein dimers with a conserved C- terminal domain (CTD) critical for the interaction with external factors. To understand the role of the individual CTD of human P1/P2 proteins, we examined the interaction of reconstituted human P-protein complexes and C-terminally truncated forms with ricin A chain (RTA), which binds to the stalk to depurinate the sarcin/ricin loop (SRL). The interaction between P-protein complexes and RTA was examined by surface plasmon resonance, isothermal titration calorimetry, microscale thermophoresis and bio-layer interferometry. The P1-P2 heterodimer missing a CTD on P2 was able to bind RTA. In contrast, the P1-P2 heterodimer missing the CTD of P1 protein displayed almost no binding toward RTA. Very low interaction was detected between RTA and the non-truncated P2-P2 homodimer, suggesting that the structural architecture of the P1-P2 heterodimer is critical for binding RTA. The reconstituted pentameric human stalk complex had higher affinity for RTA than the P1-P2 dimer. Deletion of P1 CTD, but not P2 CTD reduced the affinity of the pentamer for RTA. These results highlight the importance of the heterodimeric organization of P1-P2 in the human stalk pentamer and functional non-equivalence of the individual P-protein CTDs in the interaction with RTA.
Collapse
|
22
|
Zhou Y, Li XP, Chen BY, Tumer NE. Ricin uses arginine 235 as an anchor residue to bind to P-proteins of the ribosomal stalk. Sci Rep 2017; 7:42912. [PMID: 28230053 PMCID: PMC5322317 DOI: 10.1038/srep42912] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 01/17/2017] [Indexed: 01/24/2023] Open
Abstract
Ricin toxin A chain (RTA) binds to stalk P-proteins to reach the α-sarcin/ricin loop (SRL) where it cleaves a conserved adenine. Arginine residues at the RTA/RTB interface are involved in this interaction. To investigate the individual contribution of each arginine, we generated single, double and triple arginine mutations in RTA. The R235A mutation reduced toxicity and depurination activity more than any other single arginine mutation in yeast. Further reduction in toxicity, depurination activity and ribosome binding was observed when R235A was combined with a mutation in a nearby arginine. RTA interacts with the ribosome via a two-step process, which involves slow and fast interactions. Single arginine mutations eliminated the fast interactions with the ribosome, indicating that they increase the binding rate of RTA. Arginine residues form a positively charged patch to bind to negatively charged residues at the C-termini of P-proteins. When electrostatic interactions conferred by the arginines are lost, hydrophobic interactions are also abolished, suggesting that the hydrophobic interactions alone are insufficient to allow binding. We propose that Arg235 serves as an anchor residue and cooperates with nearby arginines and the hydrophobic interactions to provide the binding specificity and strength in ribosome targeting of RTA.
Collapse
Affiliation(s)
- Yijun Zhou
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey 08901-8520, USA
| | - Xiao-Ping Li
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey 08901-8520, USA
| | - Brian Y Chen
- Department of Computer Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015-3084, USA
| | - Nilgun E Tumer
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey 08901-8520, USA
| |
Collapse
|
23
|
Fan X, Zhu Y, Wang C, Niu L, Teng M, Li X. Structural insights into the interaction of the ribosomal P stalk protein P2 with a type II ribosome-inactivating protein ricin. Sci Rep 2016; 6:37803. [PMID: 27886256 PMCID: PMC5122897 DOI: 10.1038/srep37803] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 10/31/2016] [Indexed: 01/07/2023] Open
Abstract
Ricin is a type II ribosome-inactivating protein (RIP) that depurinates A4324 at the sarcin-ricin loop of 28 S ribosomal RNA (rRNA), thus inactivating the ribosome by preventing elongation factors from binding to the GTPase activation centre. Recent studies have disclosed that the conserved C-terminal domain (CTD) of eukaryotic ribosomal P stalk proteins is involved in the process that RIPs target ribosome. However, the details of the molecular interaction between ricin and P stalk proteins remain unknown. Here, we report the structure of ricin-A chain (RTA) in a complex with the CTD of the human ribosomal protein P2. The structure shows that the Phe111, Leu113 and Phe114 residues of P2 insert into a hydrophobic pocket formed by the Tyr183, Arg235, Phe240 and Ile251 residues of RTA, while Asp115 of P2 forms hydrogen bonds with Arg235 of RTA. The key residues in RTA and P2 for complex formation were mutated, and their importance was determined by pull-down assays. The results from cell-free translation assays further confirmed that the interaction with P stalk proteins is essential for the inhibition of protein synthesis by RTA. Taken together, our results provide a structural basis that will improve our understanding of the process by which ricin targets the ribosome, which will benefit the development of effective small-molecule inhibitors for use as therapeutic agents.
Collapse
Affiliation(s)
- Xiaojiao Fan
- Hefei National Laboratory for Physical Sciences at Microscale, Innovation Center for Cell Signaling Networks, School of Life Science, University of Science and Technology of China, Hefei, Anhui, 230026, People’s Republic of China,Key Laboratory of Structural Biology, Hefei Science Center of Chinese Academy of Science, Hefei, Anhui, 230026, People’s Republic of China
| | - Yuwei Zhu
- Hefei National Laboratory for Physical Sciences at Microscale, Innovation Center for Cell Signaling Networks, School of Life Science, University of Science and Technology of China, Hefei, Anhui, 230026, People’s Republic of China,Key Laboratory of Structural Biology, Hefei Science Center of Chinese Academy of Science, Hefei, Anhui, 230026, People’s Republic of China
| | - Chongyuan Wang
- Hefei National Laboratory for Physical Sciences at Microscale, Innovation Center for Cell Signaling Networks, School of Life Science, University of Science and Technology of China, Hefei, Anhui, 230026, People’s Republic of China,Key Laboratory of Structural Biology, Hefei Science Center of Chinese Academy of Science, Hefei, Anhui, 230026, People’s Republic of China
| | - Liwen Niu
- Hefei National Laboratory for Physical Sciences at Microscale, Innovation Center for Cell Signaling Networks, School of Life Science, University of Science and Technology of China, Hefei, Anhui, 230026, People’s Republic of China,Key Laboratory of Structural Biology, Hefei Science Center of Chinese Academy of Science, Hefei, Anhui, 230026, People’s Republic of China
| | - Maikun Teng
- Hefei National Laboratory for Physical Sciences at Microscale, Innovation Center for Cell Signaling Networks, School of Life Science, University of Science and Technology of China, Hefei, Anhui, 230026, People’s Republic of China,Key Laboratory of Structural Biology, Hefei Science Center of Chinese Academy of Science, Hefei, Anhui, 230026, People’s Republic of China,
| | - Xu Li
- Hefei National Laboratory for Physical Sciences at Microscale, Innovation Center for Cell Signaling Networks, School of Life Science, University of Science and Technology of China, Hefei, Anhui, 230026, People’s Republic of China,Key Laboratory of Structural Biology, Hefei Science Center of Chinese Academy of Science, Hefei, Anhui, 230026, People’s Republic of China,
| |
Collapse
|
24
|
Shi WW, Tang YS, Sze SY, Zhu ZN, Wong KB, Shaw PC. Crystal Structure of Ribosome-Inactivating Protein Ricin A Chain in Complex with the C-Terminal Peptide of the Ribosomal Stalk Protein P2. Toxins (Basel) 2016; 8:toxins8100296. [PMID: 27754366 PMCID: PMC5086656 DOI: 10.3390/toxins8100296] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 09/27/2016] [Accepted: 09/30/2016] [Indexed: 11/16/2022] Open
Abstract
Ricin is a type 2 ribosome-inactivating protein (RIP), containing a catalytic A chain and a lectin-like B chain. It inhibits protein synthesis by depurinating the N-glycosidic bond at α-sarcin/ricin loop (SRL) of the 28S rRNA, which thereby prevents the binding of elongation factors to the GTPase activation center of the ribosome. Here, we present the 1.6 Å crystal structure of Ricin A chain (RTA) complexed to the C-terminal peptide of the ribosomal stalk protein P2, which plays a crucial role in specific recognition of elongation factors and recruitment of eukaryote-specific RIPs to the ribosomes. Our structure reveals that the C-terminal GFGLFD motif of P2 peptide is inserted into a hydrophobic pocket of RTA, while the interaction assays demonstrate the structurally untraced SDDDM motif of P2 peptide contributes to the interaction with RTA. This interaction mode of RTA and P protein is in contrast to that with trichosanthin (TCS), Shiga-toxin (Stx) and the active form of maize RIP (MOD), implying the flexibility of the P2 peptide-RIP interaction, for the latter to gain access to ribosome.
Collapse
Affiliation(s)
- Wei-Wei Shi
- Centre for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
| | - Yun-Sang Tang
- Centre for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
| | - See-Yuen Sze
- Centre for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
| | - Zhen-Ning Zhu
- Centre for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
| | - Kam-Bo Wong
- Centre for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
| | - Pang-Chui Shaw
- Centre for Protein Science and Crystallography, School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
| |
Collapse
|
25
|
Jetzt AE, Li XP, Tumer NE, Cohick WS. Toxicity of ricin A chain is reduced in mammalian cells by inhibiting its interaction with the ribosome. Toxicol Appl Pharmacol 2016; 310:120-128. [PMID: 27639428 DOI: 10.1016/j.taap.2016.09.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 09/08/2016] [Accepted: 09/10/2016] [Indexed: 01/11/2023]
Abstract
Ricin is a potent ribotoxin that is considered a bioterror threat due to its ease of isolation and possibility of aerosolization. In yeast, mutation of arginine residues away from the active site results in a ricin toxin A chain (RTA) variant that is unable to bind the ribosome and exhibits reduced cytotoxicity. The goal of the present work was to determine if these residues contribute to ribosome binding and cytotoxicity of RTA in mammalian cells. The RTA mutant R193A/R235A did not interact with mammalian ribosomes, while a G212E variant with a point mutation near its active site bound ribosomes similarly to wild-type (WT) RTA. R193A/R235A retained full catalytic activity on naked RNA but had reduced activity on mammalian ribosomes. To determine the effect of this mutant in intact cells, pre R193A/R235A containing a signal sequence directing it to the endoplasmic reticulum and mature R193A/R235A that directly targeted cytosolic ribosomes were each expressed. Depurination and protein synthesis inhibition were reduced by both pre- and mature R193A/R235A relative to WT. Protein synthesis inhibition was reduced to a greater extent by R193A/R235A than by G212E. Pre R193A/R235A caused a greater reduction in caspase activation and loss of mitochondrial membrane potential than G212E relative to WT RTA. These findings indicate that an RTA variant with reduced ribosome binding is less toxic than a variant with less catalytic activity but normal ribosome binding activity. The toxin-ribosome interaction represents a novel target for the development of therapeutics to prevent or treat ricin intoxication.
Collapse
Affiliation(s)
- Amanda E Jetzt
- Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901-8520, United States
| | - Xiao-Ping Li
- Department of Plant Biology and Pathology, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901-8520, United States
| | - Nilgun E Tumer
- Department of Plant Biology and Pathology, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901-8520, United States
| | - Wendie S Cohick
- Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901-8520, United States.
| |
Collapse
|
26
|
Artero-Castro A, Perez-Alea M, Feliciano A, Leal JA, Genestar M, Castellvi J, Peg V, Ramón Y Cajal S, Lleonart MEL. Disruption of the ribosomal P complex leads to stress-induced autophagy. Autophagy 2016; 11:1499-519. [PMID: 26176264 DOI: 10.1080/15548627.2015.1063764] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
The human ribosomal P complex, which consists of the acidic ribosomal P proteins RPLP0, RPLP1, and RPLP2 (RPLP proteins), recruits translational factors, facilitating protein synthesis. Recently, we showed that overexpression of RPLP1 immortalizes primary cells and contributes to transformation. Moreover, RPLP proteins are overexpressed in human cancer, with the highest incidence in breast carcinomas. It is thought that disruption of the P complex would directly affect protein synthesis, causing cell growth arrest and eventually apoptosis. Here, we report a distinct mechanism by which cancer cells undergo cell cycle arrest and induced autophagy when RPLP proteins are downregulated. We found that absence of RPLP0, RPLP1, or RPLP2 resulted in reactive oxygen species (ROS) accumulation and MAPK1/ERK2 signaling pathway activation. Moreover, ROS generation led to endoplasmic reticulum (ER) stress that involved the EIF2AK3/PERK-EIF2S1/eIF2α-EIF2S2-EIF2S3-ATF4/ATF-4- and ATF6/ATF-6-dependent arms of the unfolded protein response (UPR). RPLP protein-deficient cells treated with autophagy inhibitors experienced apoptotic cell death as an alternative to autophagy. Strikingly, antioxidant treatment prevented UPR activation and autophagy while restoring the proliferative capacity of these cells. Our results indicate that ROS are a critical signal generated by disruption of the P complex that causes a cellular response that follows a sequential order: first ROS, then ER stress/UPR activation, and finally autophagy. Importantly, inhibition of the first step alone is able to restore the proliferative capacity of the cells, preventing UPR activation and autophagy. Overall, our results support a role for autophagy as a survival mechanism in response to stress due to RPLP protein deficiency.
Collapse
Affiliation(s)
- Ana Artero-Castro
- a Oncology and Pathology Group ; Pathology Department; Institut de Recerca Hospital Vall d'Hebron ; Barcelona , Spain
| | - Mileidys Perez-Alea
- a Oncology and Pathology Group ; Pathology Department; Institut de Recerca Hospital Vall d'Hebron ; Barcelona , Spain
| | - Andrea Feliciano
- a Oncology and Pathology Group ; Pathology Department; Institut de Recerca Hospital Vall d'Hebron ; Barcelona , Spain
| | - Jose A Leal
- a Oncology and Pathology Group ; Pathology Department; Institut de Recerca Hospital Vall d'Hebron ; Barcelona , Spain
| | - Mónica Genestar
- a Oncology and Pathology Group ; Pathology Department; Institut de Recerca Hospital Vall d'Hebron ; Barcelona , Spain
| | - Josep Castellvi
- a Oncology and Pathology Group ; Pathology Department; Institut de Recerca Hospital Vall d'Hebron ; Barcelona , Spain
| | - Vicente Peg
- a Oncology and Pathology Group ; Pathology Department; Institut de Recerca Hospital Vall d'Hebron ; Barcelona , Spain
| | - Santiago Ramón Y Cajal
- a Oncology and Pathology Group ; Pathology Department; Institut de Recerca Hospital Vall d'Hebron ; Barcelona , Spain
| | - Matilde E L Lleonart
- a Oncology and Pathology Group ; Pathology Department; Institut de Recerca Hospital Vall d'Hebron ; Barcelona , Spain
| |
Collapse
|
27
|
The A1 Subunit of Shiga Toxin 2 Has Higher Affinity for Ribosomes and Higher Catalytic Activity than the A1 Subunit of Shiga Toxin 1. Infect Immun 2015; 84:149-61. [PMID: 26483409 DOI: 10.1128/iai.00994-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 10/12/2015] [Indexed: 01/25/2023] Open
Abstract
Shiga toxin (Stx)-producing Escherichia coli (STEC) infections can lead to life-threatening complications, including hemorrhagic colitis (HC) and hemolytic-uremic syndrome (HUS), which is the most common cause of acute renal failure in children in the United States. Stx1 and Stx2 are AB5 toxins consisting of an enzymatically active A subunit associated with a pentamer of receptor binding B subunits. Epidemiological evidence suggests that Stx2-producing E. coli strains are more frequently associated with HUS than Stx1-producing strains. Several studies suggest that the B subunit plays a role in mediating toxicity. However, the role of the A subunits in the increased potency of Stx2 has not been fully investigated. Here, using purified A1 subunits, we show that Stx2A1 has a higher affinity for yeast and mammalian ribosomes than Stx1A1. Biacore analysis indicated that Stx2A1 has faster association and dissociation with ribosomes than Stx1A1. Analysis of ribosome depurination kinetics demonstrated that Stx2A1 depurinates yeast and mammalian ribosomes and an RNA stem-loop mimic of the sarcin/ricin loop (SRL) at a higher catalytic rate and is a more efficient enzyme than Stx1A1. Stx2A1 depurinated ribosomes at a higher level in vivo and was more cytotoxic than Stx1A1 in Saccharomyces cerevisiae. Stx2A1 depurinated ribosomes and inhibited translation at a significantly higher level than Stx1A1 in human cells. These results provide the first direct evidence that the higher affinity for ribosomes in combination with higher catalytic activity toward the SRL allows Stx2A1 to depurinate ribosomes, inhibit translation, and exhibit cytotoxicity at a significantly higher level than Stx1A1.
Collapse
|
28
|
Basu D, Tumer NE. Do the A subunits contribute to the differences in the toxicity of Shiga toxin 1 and Shiga toxin 2? Toxins (Basel) 2015; 7:1467-85. [PMID: 25938272 PMCID: PMC4448158 DOI: 10.3390/toxins7051467] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 04/23/2015] [Accepted: 04/27/2015] [Indexed: 12/25/2022] Open
Abstract
Shiga toxin producing Escherichia coli O157:H7 (STEC) is one of the leading causes of food-poisoning around the world. Some STEC strains produce Shiga toxin 1 (Stx1) and/or Shiga toxin 2 (Stx2) or variants of either toxin, which are critical for the development of hemorrhagic colitis (HC) or hemolytic uremic syndrome (HUS). Currently, there are no therapeutic treatments for HC or HUS. E. coli O157:H7 strains carrying Stx2 are more virulent and are more frequently associated with HUS, which is the most common cause of renal failure in children in the US. The basis for the increased potency of Stx2 is not fully understood. Shiga toxins belong to the AB5 family of protein toxins with an A subunit, which depurinates a universally conserved adenine residue in the α-sarcin/ricin loop (SRL) of the 28S rRNA and five copies of the B subunit responsible for binding to cellular receptors. Recent studies showed differences in the structure, receptor binding, dependence on ribosomal proteins and pathogenicity of Stx1 and Stx2 and supported a role for the B subunit in differential toxicity. However, the current data do not rule out a potential role for the A1 subunits in the differential toxicity of Stx1 and Stx2. This review highlights the recent progress in understanding the differences in the A1 subunits of Stx1 and Stx2 and their role in defining toxicity.
Collapse
Affiliation(s)
- Debaleena Basu
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901-8520, USA.
| | - Nilgun E Tumer
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901-8520, USA.
| |
Collapse
|
29
|
Structures of eukaryotic ribosomal stalk proteins and its complex with trichosanthin, and their implications in recruiting ribosome-inactivating proteins to the ribosomes. Toxins (Basel) 2015; 7:638-47. [PMID: 25723321 PMCID: PMC4379515 DOI: 10.3390/toxins7030638] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 01/30/2015] [Accepted: 02/15/2015] [Indexed: 11/17/2022] Open
Abstract
Ribosome-inactivating proteins (RIP) are RNA N-glycosidases that inactivate ribosomes by specifically depurinating a conserved adenine residue at the α-sarcin/ricin loop of 28S rRNA. Recent studies have pointed to the involvement of the C-terminal domain of the eukaryotic stalk proteins in facilitating the toxic action of RIPs. This review highlights how structural studies of eukaryotic stalk proteins provide insights into the recruitment of RIPs to the ribosomes. Since the C-terminal domain of eukaryotic stalk proteins is involved in specific recognition of elongation factors and some eukaryote-specific RIPs (e.g., trichosanthin and ricin), we postulate that these RIPs may have evolved to hijack the translation-factor-recruiting function of ribosomal stalk in reaching their target site of rRNA.
Collapse
|
30
|
Functional divergence between the two P1-P2 stalk dimers on the ribosome in their interaction with ricin A chain. Biochem J 2014; 460:59-67. [PMID: 24576056 DOI: 10.1042/bj20140014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The eukaryotic stalk, which is responsible for the recruitment of translation factors, is a pentamer containing two P1-P2 dimers with unclear modes of action. In Saccharomyces cerevisiae, P1/P2 proteins (individual P1 and P2 proteins) are organized into two distinct dimers, P1A-P2B and P1B-P2A. To investigate the functional contribution of each dimer on the ribosome, RTA (ricin A chain), which binds to the stalk to depurinate the SRL (sarcin/ricin loop), was used as a molecular probe in yeast mutants in which the binding site for one or the other dimer on P0 was deleted. Ribosome depurination and toxicity of RTA were greatly reduced in mutants containing only P1A-P2B on the ribosome, whereas those with only P1B-P2A were reduced less in depurination and were unaffected in toxicity. Ribosomes bearing P1B-P2A were depurinated by RTA at a similar level as wild-type, but ribosomes bearing P1A-P2B were depurinated at a much lower level in vitro. The latter ribosomes showed the lowest association and almost no dissociation with RTA by surface plasmon resonance. These results indicate that the P1B-P2A dimer is more critical for facilitating the access of RTA to the SRL, providing the first in vivo evidence for functional divergence between the two stalk dimers on the ribosome.
Collapse
|
31
|
Li XP, Kahn PC, Kahn JN, Grela P, Tumer NE. Arginine residues on the opposite side of the active site stimulate the catalysis of ribosome depurination by ricin A chain by interacting with the P-protein stalk. J Biol Chem 2013; 288:30270-30284. [PMID: 24003229 DOI: 10.1074/jbc.m113.510966] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Ricin inhibits protein synthesis by depurinating the α-sarcin/ricin loop (SRL). Ricin holotoxin does not inhibit translation unless the disulfide bond between the A (RTA) and B (RTB) subunits is reduced. Ricin holotoxin did not bind ribosomes or depurinate them but could depurinate free RNA. When RTA is separated from RTB, arginine residues located at the interface are exposed to the solvent. Because this positively charged region, but not the active site, is blocked by RTB, we mutated arginine residues at or near the interface of RTB to determine if they are critical for ribosome binding. These variants were structurally similar to wild type RTA but could not bind ribosomes. Their K(m) values and catalytic rates (k(cat)) for an SRL mimic RNA were similar to those of wild type, indicating that their activity was not altered. However, they showed an up to 5-fold increase in K(m) and up to 38-fold decrease in kcat toward ribosomes. These results suggest that the stalk binding stimulates the catalysis of ribosome depurination by RTA. The mutated arginines have side chains behind the active site cleft, indicating that the ribosome binding surface of RTA is on the opposite side of the surface that interacts with the SRL. We propose that stalk binding stimulates the catalysis of ribosome depurination by orienting the active site of RTA toward the SRL and thereby allows docking of the target adenine into the active site. This model may apply to the translation factors that interact with the stalk.
Collapse
Affiliation(s)
- Xiao-Ping Li
- From the Departments of Plant Biology and Pathology and
| | - Peter C Kahn
- Biochemistry and Microbiology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey 08901-8520
| | | | | | - Nilgun E Tumer
- From the Departments of Plant Biology and Pathology and.
| |
Collapse
|
32
|
Ricin and Ricin-Containing Immunotoxins: Insights into Intracellular Transport and Mechanism of action in Vitro. Antibodies (Basel) 2013. [DOI: 10.3390/antib2020236] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
|
33
|
May KL, Yan Q, Tumer NE. Targeting ricin to the ribosome. Toxicon 2013; 69:143-51. [PMID: 23454625 DOI: 10.1016/j.toxicon.2013.02.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 02/01/2013] [Accepted: 02/06/2013] [Indexed: 12/15/2022]
Abstract
The plant toxin ricin is highly toxic for mammalian cells and is of concern for bioterrorism. Ricin belongs to a family of functionally related toxins, collectively referred to as ribosome inactivating proteins (RIPs), which disable ribosomes and halt protein synthesis. Currently there are no specific antidotes against ricin or related RIPs. The catalytic subunit of ricin is an N-glycosidase that depurinates a universally conserved adenine residue within the sarcin/ricin loop (SRL) of the 28S rRNA. This depurination activity inhibits translation and its biochemistry has been intensively studied. Yet, recent developments paint a more complex picture of toxicity, with ribosomal proteins and cellular signaling pathways contributing to the potency of ricin. In particular, several studies have now established the importance of the ribosomal stalk structure in facilitating the depurination activity and ribosome specificity of ricin and other RIPs. This review highlights recent developments defining toxin-ribosome interactions and examines the significance of these interactions for toxicity and therapeutic intervention.
Collapse
Affiliation(s)
- Kerrie L May
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901-8520, USA
| | | | | |
Collapse
|