1
|
Dong N, Luo L, Wu J, Jia P, Li Q, Wang Y, Gao Z, Peng H, Lv M, Huang C, Feng J, Li H, Shan J, Han G, Shen B. Monoclonal antibody, mAb 4C13, an effective detoxicant antibody against ricin poisoning. Vaccine 2015; 33:3836-42. [PMID: 26141013 DOI: 10.1016/j.vaccine.2015.06.096] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 06/15/2015] [Accepted: 06/19/2015] [Indexed: 11/30/2022]
Abstract
Ricin is a glycoprotein produced in castor seeds and consists of two polypeptide chains named Ricin Toxin A Chain (RTA) and Ricin Toxin B Chain (RTB), linked via a disulfide bridge. Due to its high toxicity, ricin is regarded as a high terrorist risk for the public. However, antibodies can play a pivotal role in neutralizing the toxin. In this research, the anti-toxicant effect of mAb 4C13, a monoclonal antibody (mAb) established using detoxicated ricin as the immunized antigen, was evaluated. Compared with mAb 4F2 and mAb 5G6, the effective mechanism of mAb 4C13 was analyzed by experiments relating to its cytotoxicity, epitope on ricin, binding kinetics with the toxin, its blockage on the protein synthesis inhibition induced by ricin and the intracelluar tracing of its complex with ricin. Our result indicated that mAb 4C13 could recognize and bind to RTA, RTB and exert its high affinity to the holotoxin. Both cytotoxicity and animal toxicity of ricin were well blocked by pre-incubating the toxin with mAb 4C13. By intravenous injection, mAb 4C13 could rescue the mouse intraperitoneally (ip) injected with a lethal dose of ricin (20μg/kg) even at 6h after the intoxication and its efficacy was dependent on its dosage. This research indicated that mAb 4C13 could be an excellent candidate for therapeutic antibodies. Its potent antitoxic efficiency was related to its recognition on the specific epitope with very high affinity and its blockage of protein synthesis inhibition in cytoplasm followed by cellular internalization with ricin.
Collapse
Affiliation(s)
- Na Dong
- Beijing Institute of Pharmacology and Toxicology, State Key Laboratory of Toxicology and Medical Countermeasures, Beijing 100850, China
| | - Longlong Luo
- Beijing Institute of Basic Medical Sciences, Beijing 100850, China
| | - Junhua Wu
- Beijing Institute of Pharmacology and Toxicology, State Key Laboratory of Toxicology and Medical Countermeasures, Beijing 100850, China
| | - Peiyuan Jia
- Beijing Institute of Pharmacology and Toxicology, State Key Laboratory of Toxicology and Medical Countermeasures, Beijing 100850, China
| | - Qian Li
- Beijing Institute of Pharmacology and Toxicology, State Key Laboratory of Toxicology and Medical Countermeasures, Beijing 100850, China; Beijing Institute of Basic Medical Sciences, Beijing 100850, China
| | - Yuxia Wang
- Beijing Institute of Pharmacology and Toxicology, State Key Laboratory of Toxicology and Medical Countermeasures, Beijing 100850, China.
| | - Zhongcai Gao
- Beijing Institute of Pharmacology and Toxicology, State Key Laboratory of Toxicology and Medical Countermeasures, Beijing 100850, China
| | - Hui Peng
- Beijing Institute of Basic Medical Sciences, Beijing 100850, China
| | - Ming Lv
- Beijing Institute of Basic Medical Sciences, Beijing 100850, China
| | - Chunqian Huang
- Beijing Institute of Pharmacology and Toxicology, State Key Laboratory of Toxicology and Medical Countermeasures, Beijing 100850, China
| | - Jiannan Feng
- Beijing Institute of Basic Medical Sciences, Beijing 100850, China.
| | - Hua Li
- Beijing Institute of Pharmacology and Toxicology, State Key Laboratory of Toxicology and Medical Countermeasures, Beijing 100850, China
| | - Junjie Shan
- Beijing Institute of Pharmacology and Toxicology, State Key Laboratory of Toxicology and Medical Countermeasures, Beijing 100850, China
| | - Gang Han
- Beijing Institute of Pharmacology and Toxicology, State Key Laboratory of Toxicology and Medical Countermeasures, Beijing 100850, China
| | - Beifen Shen
- Beijing Institute of Basic Medical Sciences, Beijing 100850, China
| |
Collapse
|
2
|
Zhang T, Kang L, Gao S, Yang H, Xin W, Wang J, Guo M, Wang J. Truncated abrin A chain expressed in Escherichia coli: a promising vaccine candidate. Hum Vaccin Immunother 2014; 10:2648-55. [PMID: 25483485 DOI: 10.4161/hv.29645] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Abrin toxin (AT) is a highly potent toxin, and is classified as one of the most important biological warfare and bioterrorism agents. There is currently no approved vaccine for AT. Therefore, the development of an effective vaccine is important in the prevention of intoxication by abrin. In this study, five vectors containing different gene of truncated abrin toxin A chain (tATA) fragments were constructed, and two of them (tATA1(1-126), tATA4(1-188)) were successfully expressed as a soluble form in E.coli strain. Both of the two tATA retained most of their immunogenicity with either low or no toxic effects as determined by both in vitro and in vivo assays. They were used to immunize BALB/c mice three times at an interval of three weeks apart. As a result, the tATA1 can elicite 80% protective efficacy against i.p. challenge of 5×LD50 of abrin, and the tATA4 provides a better protection, which can elicite 100% protective efficacy against intraperitoneal challenge of 40×LD50 of abrin. The superior fragment (tATA4(1-188)) should be considered as a promising vaccine candidate for further investigations.
Collapse
Key Words
- AU, absorbance unit
- BSA, bovine serum albumin
- E.coli, Escherichia coli
- IPTG, isopropyl-1-thio-β-galactopyranoside
- LD50, 50% lethal dose
- PBS, phosphate–buffered saline solution
- PCR, polymerase chain reaction
- SD, standard deviation
- abrin
- i.g., intragastric
- i.n., intranasal
- i.p., intraperitoneal/intraperitoneally
- immunity
- pAb, polyclonal antibody
- protection
- rATA, recombinant A chain of abrin toxin
- s.c., subcutaneous/subcutaneously
- tATA, truncated A chain of abrin toxin
- toxicity
- toxin
- truncated protein
- vaccine
Collapse
Affiliation(s)
- Tao Zhang
- a State Key Laboratory of Pathogen and Biosecurity ; The Institute of Microbiology and Epidemiology; Academy of Military Medical Sciences ; Beijing , PR China
| | | | | | | | | | | | | | | |
Collapse
|
3
|
Kumar RB, Suresh MX. A computational perspective of molecular interactions through virtual screening, pharmacokinetic and dynamic prediction on ribosome toxin A chain and inhibitors of Ricinus communis. Pharmacognosy Res 2012; 4:2-10. [PMID: 22224054 PMCID: PMC3250034 DOI: 10.4103/0974-8490.91027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 09/04/2011] [Accepted: 12/22/2011] [Indexed: 11/28/2022] Open
Abstract
Background: Ricin is considered to be one of the most deadly toxins and gained its favor as a bioweapon that has a serious social and biological impact, due to its widespread nature and abundant availability. The hazardous effects of this toxin in human being are seen in almost all parts of the organ system. The severe consequences of the toxin necessitate the need for developing potential inhibitors that can effectively block its interaction with the host system. Materials and Methods: In order to identify potential inhibitors that can effectively block ricin, we employed various computational approaches. In this work, we computationally screened and analyzed 66 analogs and further tested their ADME/T profiles. From the kinetic and toxicity studies we selected six analogs that possessed appropriate pharmacokinetic and dynamic property. We have also performed a computational docking of these analogs with the target. Results: On the basis of the dock scores and hydrogen bond interactions we have identified analog 64 to be the best interacting molecule. Molecule 64 seems to have stable interaction with the residues Tyr80, Arg180, and Val81. The pharmacophore feature that describes the key functional features of a molecule was also studied and presented. Conclusion: The pharmacophore features of the drugs provided suggests the key functional groups that can aid in the design and synthesis of more potential inhibitors.
Collapse
Affiliation(s)
- R Barani Kumar
- Department of Bioinformatics, Sathyabama University, Chennai, Tamil Nadu, India
| | | |
Collapse
|
4
|
Jetzt AE, Cheng JS, Li XP, Tumer NE, Cohick WS. A relatively low level of ribosome depurination by mutant forms of ricin toxin A chain can trigger protein synthesis inhibition, cell signaling and apoptosis in mammalian cells. Int J Biochem Cell Biol 2012; 44:2204-11. [PMID: 22982239 DOI: 10.1016/j.biocel.2012.09.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 08/27/2012] [Accepted: 09/05/2012] [Indexed: 11/25/2022]
Abstract
The A chain of the plant toxin ricin (RTA) is an N-glycosidase that inhibits protein synthesis by removing a specific adenine from the 28S rRNA. RTA also induces ribotoxic stress, which activates stress-induced cell signaling cascades and apoptosis. However, the mechanistic relationship between depurination, protein synthesis inhibition and apoptosis remains an open question. We previously identified two RTA mutants that suggested partial independence of these processes in a yeast model. The goals of this study were to establish an endogenous RTA expression system in mammalian cells and utilize RTA mutants to examine the relationship between depurination, protein synthesis inhibition, cell signaling and apoptosis in mammalian cells. The non-transformed epithelial cell line MAC-T was transiently transfected with plasmid vectors encoding precursor (pre) or mature forms of wild-type (WT) RTA or mutants. PreRTA was glycosylated indicating that the native signal peptide targeted RTA to the ER in mammalian cells. Mature RTA was not glycosylated and thus served as a control to detect changes in catalytic activity. Both pre- and mature WT RTA induced ribosome depurination, protein synthesis inhibition, activation of cell signaling and apoptosis. Analysis of RTA mutants showed for the first time that depurination can be reduced by 40% in mammalian cells with minimal effects on inhibition of protein synthesis, activation of cell signaling and apoptosis. We further show that protein synthesis inhibition by RTA correlates more linearly with apoptosis than ribosome depurination.
Collapse
Affiliation(s)
- Amanda E Jetzt
- Department of Animal Sciences, School of Environmental and Biological Sciences, 59 Dudley Road, Rutgers, The State University of NJ, New Brunswick, NJ 08901-8520, USA
| | | | | | | | | |
Collapse
|
5
|
Pincus SH, Smallshaw JE, Song K, Berry J, Vitetta ES. Passive and active vaccination strategies to prevent ricin poisoning. Toxins (Basel) 2011; 3:1163-84. [PMID: 22069761 PMCID: PMC3202875 DOI: 10.3390/toxins3091163] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 08/17/2011] [Accepted: 09/05/2011] [Indexed: 11/16/2022] Open
Abstract
Ricin toxin (RT) is derived from castor beans, produced by the plant Ricinus communis. RT and its toxic A chain (RTA) have been used therapeutically to arm ligands that target disease-causing cells. In most cases these ligands are cell-binding monoclonal antibodies (MAbs). These ligand-toxin conjugates or immunotoxins (ITs) have shown success in clinical trials [1]. Ricin is also of concern in biodefense and has been classified by the CDC as a Class B biothreat. Virtually all reports of RT poisoning have been due to ingestion of castor beans, since they grow abundantly throughout the world and are readily available. RT is easily purified and stable, and is not difficult to weaponize. RT must be considered during any "white powder" incident and there have been documented cases of its use in espionage [2,3]. The clinical syndrome resulting from ricin intoxication is dependent upon the route of exposure. Countermeasures to prevent ricin poisoning are being developed and their use will depend upon whether military or civilian populations are at risk of exposure. In this review we will discuss ricin toxin, its cellular mode of action, the clinical syndromes that occur following exposure and the development of pre- and post-exposure approaches to prevent of intoxication.
Collapse
Affiliation(s)
- Seth H. Pincus
- Children’s Hospital and LSU Health Sciences Center, New Orleans, LA 70118, USA;
| | - Joan E. Smallshaw
- Cancer Immunobiology Center and Department of Microbiology, University of Texas, Southwestern Medical Center, Dallas, TX 75235, USA;
| | - Kejing Song
- Children’s Hospital, New Orleans, LA 70118, USA;
| | - Jody Berry
- Cangene Corporation, Winnipeg, MB R3T 5Y3, Canada;
| | - Ellen S. Vitetta
- Cancer Immunobiology Center, Departments Of Immunology and Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75230, USA
| |
Collapse
|
6
|
Porter A, Phillips G, Smith L, Erwin-Cohen R, Tammariello R, Hale M, DaSilva L. Evaluation of a ricin vaccine candidate (RVEc) for human toxicity using an in vitro vascular leak assay. Toxicon 2011; 58:68-75. [DOI: 10.1016/j.toxicon.2011.05.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Revised: 05/04/2011] [Accepted: 05/05/2011] [Indexed: 01/05/2023]
|
7
|
Abstract
In this chapter we discuss vaccines to protect against the highly toxic plant-derived toxin, ricin. Due to its prevalence, ease of use, and stability it has been used in sporadic incidents of espionage. There is also concern that it will be used as an agent of bioterrorism. As a result there has been a great deal of interest in developing a safe vaccine or antidote to protect humans, and in particular soldiers and first responders. Although multiple types of vaccines have been tested, at this time two recombinant vaccines are the leading candidates for the national vaccine stockpile. In terms of passive post-exposure protection, monoclonal neutralizing antibodies that passively protect animals are also under development. These vaccines and antibodies are discussed in the context of the toxicity and structure of ricin.
Collapse
Affiliation(s)
- Joan E Smallshaw
- The Cancer Immunobiology Center, Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, USA
| | | |
Collapse
|
8
|
Intradermal administration of RiVax protects mice from mucosal and systemic ricin intoxication. Vaccine 2010; 28:5315-22. [PMID: 20562013 DOI: 10.1016/j.vaccine.2010.05.045] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 05/06/2010] [Accepted: 05/15/2010] [Indexed: 11/24/2022]
Abstract
Ricin toxin is a CDC level B biothreat. We have developed a ricin vaccine, RiVax, which is a recombinant mutant of ricin A chain. RiVax is safe, immunogenic and protective in mice when administered intramuscularly (IM). We have now attempted to increase the utility and immunogenicity of RiVax by administering it intradermally (ID) with or without alum. Without alum, Rivax administered by the ID and IM routes was equally immunogenic and protective. With alum, ID vaccinations were more immunogenic and protective against both systemic and mucosal challenge with ricin and superior in protecting animals from ricin-induced lung damage.
Collapse
|
9
|
Griffiths GD, Phillips GJ, Holley J. Inhalation Toxicology of Ricin Preparations: Animal Models, Prophylactic and Therapeutic Approaches to Protection. Inhal Toxicol 2008; 19:873-87. [PMID: 17687718 DOI: 10.1080/08958370701432124] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Ricin is a toxin and seed protein produced by the castor oil plant, Ricinus communis. The toxin is a dimeric protein consisting of an enzymic A chain and a B chain with lectin properties aiding the uptake of the whole molecule into cells. Ricin has been considered a possible military threat for several decades and is now also of some concern as a terrorist agent. The inhalation route is of primary concern in these situations, although previous attacks with ricin have used other approaches. Medical countermeasures against ricin are urgently required and the strategy adopted has been first to understand the nature of the problem, in this case the inhalation toxicology of ricin, followed by the preparation of vaccine antigens. Toxoided ricin and modified recombinant A chain components have been examined in terms of efficacy as potential vaccine candidates in protection of animal models against inhaled ricin, primarily in laboratories both in the United Kingdom and in the United States. One recombinant A chain vaccine has been taken through to clinical trials in the United States and should become commercially available in the next few years. Toxoided ricin has also been used as an antigen to prepare antitoxin antibodies for therapeutic treatment following poisoning. In this review, a synopsis of the inhalation toxicology of ricin and approaches to medical prophylaxis and therapy of poisoning is given, based on work conducted at our laboratory and at other research institutes.
Collapse
Affiliation(s)
- Gareth D Griffiths
- Biology, Biomedical Sciences Department, Defence Science and Technology Laboratory, Porton Down, Salisbury, Wiltshire, United Kingdom.
| | | | | |
Collapse
|
10
|
Smallshaw JE, Richardson JA, Vitetta ES. RiVax, a recombinant ricin subunit vaccine, protects mice against ricin delivered by gavage or aerosol. Vaccine 2007; 25:7459-69. [PMID: 17875350 PMCID: PMC2049008 DOI: 10.1016/j.vaccine.2007.08.018] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Revised: 07/16/2007] [Accepted: 08/02/2007] [Indexed: 10/22/2022]
Abstract
Ricin is a plant toxin that is a CDC level B biothreat. Our recombinant ricin A chain vaccine (RiVax), which contains mutations in both known toxic sites, has no residual toxicity at doses at least 800 times the immunogenic dose. RiVax without adjuvant given intramuscularly (i.m.) protected mice against intraperitoneally administered ricin. Furthermore the vaccine without alum was safe and immunogenic in human volunteers. Here we describe the development of gavage and aerosol ricin challenge models in mice and demonstrate that i.m. vaccination protects mice against ricin delivered by either route. Also RiVax protects against aerosol-induced lung damage as determined by histology and lung function tests.
Collapse
Affiliation(s)
- Joan E. Smallshaw
- The Cancer Immunobiology Center and the Department of Microbiology, University of Texas Southwestern Medical Center at Dallas, 6000 Harry Hines Blvd., Dallas, Texas 75390-8576, USA
| | - James A. Richardson
- Departments of Pathology and Molecular Biology, University of Texas Southwestern Medical Center at Dallas, 6000 Harry Hines Blvd., Dallas, Texas 75390-8576, USA
| | - Ellen S. Vitetta
- The Cancer Immunobiology Center and the Department of Microbiology, University of Texas Southwestern Medical Center at Dallas, 6000 Harry Hines Blvd., Dallas, Texas 75390-8576, USA
| |
Collapse
|
11
|
Marsden CJ, Smith DC, Roberts LM, Lord JM. Ricin: current understanding and prospects for an antiricin vaccine. Expert Rev Vaccines 2006; 4:229-37. [PMID: 15889996 DOI: 10.1586/14760584.4.2.229] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Ricin is a potent cytotoxin that can be rapidly internalized into mammalian cells leading to cell death. The ease in obtaining the toxin and its deadly nature combine to implicate ricin as a convenient agent for bioterrorism. Research into the mechanism of toxicity, as well as strategies for treatment and protection from the toxin has been widely undertaken for a number of years. This article reviews the current understanding of the mechanism of action of the toxin, the clinical effects of ricin intoxication and how these relate to current and continuing prospects for vaccine development.
Collapse
Affiliation(s)
- Catherine J Marsden
- Department of Biological Sciences, University of Warwick, Coventry, CV4 7AL, UK.
| | | | | | | |
Collapse
|
12
|
Vitetta ES, Smallshaw JE, Coleman E, Jafri H, Foster C, Munford R, Schindler J. A pilot clinical trial of a recombinant ricin vaccine in normal humans. Proc Natl Acad Sci U S A 2006; 103:2268-73. [PMID: 16461456 PMCID: PMC1413738 DOI: 10.1073/pnas.0510893103] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ricin, a highly potent toxin produced by castor beans, is classified by the Centers for Disease Control and Prevention as a level B biothreat because it is easily produced, readily available, and highly stable. There have been >750 cases of documented ricin intoxication in humans. There is no approved vaccine for ricin. Ricin contains a lectin-binding B chain and a ribotoxic A chain (RTA). In addition to its ribotoxic site, we have identified a separate site on RTA that is responsible for inducing vascular leak syndrome (VLS) in humans. We have generated a recombinant RTA with two amino acid substitutions that disrupt its ribotoxic site (Y80A) and its VLS-inducing site (V76M). This mutant recombinant RTA (named RiVax) was expressed and produced in Escherichia coli and purified. When RiVax was injected i.m. into mice it protected them against a ricin challenge of 10 LD50s. Preclinical studies in both mice and rabbits demonstrated that RiVax was safe. Based on these results, we have now conducted a pilot clinical trial in humans under an investigational new drug application submitted to the Food and Drug Administration. In this study, three groups of five normal volunteers were injected three times at monthly intervals with 10, 33, or 100 mug of RiVax. The vaccine was safe and elicited ricin-neutralizing Abs in one of five individuals in the low-dose group, four of five in the intermediate-dose group, and five of five in the high-dose group. These results justify further development of the vaccine.
Collapse
Affiliation(s)
- Ellen S Vitetta
- Cancer Immunobiology Center, Aston Center, Department of Microbiology, University of Texas Southwestern Medical School, Dallas, TX 75390, USA.
| | | | | | | | | | | | | |
Collapse
|
13
|
Bramwell VW, Eyles JE, Oya Alpar H. Particulate delivery systems for biodefense subunit vaccines. Adv Drug Deliv Rev 2005; 57:1247-65. [PMID: 15935873 DOI: 10.1016/j.addr.2005.01.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2004] [Accepted: 01/25/2005] [Indexed: 02/03/2023]
Abstract
Expanding identification of potentially protective subunit antigens and correlates of protection has provided a basis for the introduction of safer vaccines. Despite encouraging results in animal models, the significant potential of particulate delivery systems in vaccine design has not yet translated into effective vaccines available for use in humans. This review article will focus on the current status of the development of particulate vaccines, mainly liposomes and bio-degradable polymers, against potential agents for biowarfare: plague, anthrax, botulinum, and smallpox; and filoviruses: Marburg and Ebola.
Collapse
Affiliation(s)
- Vincent W Bramwell
- School of Pharmacy, University of London, 29-39 Brunswick Square, London, WC1N 1AX, UK
| | | | | |
Collapse
|
14
|
Abstract
Ricin is a potent, plant-derived, ribosome inactivating protein. To target ribosomes in the mammalian cytosol, ricin must firstly negotiate the endomembrane system of the cell to reach the endoplasmic reticulum. Here, the toxin is reduced and the catalytic A chain is recognised by ER components that facilitate its membrane translocation to the cytosol. To be toxic, ricin A chain must then avoid degradation, a conundrum made more tricky in that ubiquitination and proteasomal degradation are normally tightly coupled to the translocation process. This mini-review summarises current understanding of these events.
Collapse
Affiliation(s)
- Lynne M Roberts
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK.
| | | |
Collapse
|