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Yoon C, Lee EJ, Kim D, Joung S, Kim Y, Jung H, Kim YG, Lee GM. SiMPl-GS: Advancing Cell Line Development via Synthetic Selection Marker for Next-Generation Biopharmaceutical Production. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2405593. [PMID: 39105414 DOI: 10.1002/advs.202405593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2024] [Revised: 07/24/2024] [Indexed: 08/07/2024]
Abstract
Rapid and efficient cell line development (CLD) process is essential to expedite therapeutic protein development. However, the performance of widely used glutamine-based selection systems is limited by low selection efficiency, stringency, and the inability to select multiple genes. Therefore, an AND-gate synthetic selection system is rationally designed using split intein-mediated protein ligation of glutamine synthetase (GS) (SiMPl-GS). Split sites of the GS are selected using a computational approach and validated with GS-knockout Chinese hamster ovary cells for their potential to enable cell survival in a glutamine-free medium. In CLD, SiMPl-GS outperforms the wild-type GS by selectively enriching high producers. Unlike wild-type GS, SiMPl-GS results in cell pools in which most cells produce high levels of therapeutic proteins. Harnessing orthogonal split intein pairs further enables the selection of four plasmids with a single selection, streamlining multispecific antibody-producing CLD. Taken together, SiMPl-GS is a simple yet effective means to expedite CLD for therapeutic protein production.
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Affiliation(s)
- Chansik Yoon
- Department of Biological Sciences, KAIST, Daejeon, 34141, Republic of Korea
| | - Eun-Ji Lee
- Biotherapeutics Translational Research Center, KRIBB, Daejeon, 34113, Republic of Korea
- Department of Bioprocess Engineering, KRIBB School of Biotechnology, UST, Daejeon, 34141, Republic of Korea
| | - Dongil Kim
- Department of Biological Sciences, KAIST, Daejeon, 34141, Republic of Korea
| | - Siyun Joung
- Department of Biological Sciences, KAIST, Daejeon, 34141, Republic of Korea
| | - Yujin Kim
- Department of Biological Sciences, KAIST, Daejeon, 34141, Republic of Korea
| | - Heungchae Jung
- Department of Bioprocess Engineering, KRIBB School of Biotechnology, UST, Daejeon, 34141, Republic of Korea
- BIO Center, Daejeon Technopark, Daejeon, 34054, Republic of Korea
| | - Yeon-Gu Kim
- Biotherapeutics Translational Research Center, KRIBB, Daejeon, 34113, Republic of Korea
- Department of Bioprocess Engineering, KRIBB School of Biotechnology, UST, Daejeon, 34141, Republic of Korea
| | - Gyun Min Lee
- Department of Biological Sciences, KAIST, Daejeon, 34141, Republic of Korea
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Yuan S, Bremmer A, Yang X, Li J, Hu Q. Splittable systems in biomedical applications. Biomater Sci 2024; 12:4103-4116. [PMID: 39012216 DOI: 10.1039/d4bm00709c] [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: 07/17/2024]
Abstract
Splittable systems have emerged as a powerful approach for the precise spatiotemporal control of biological processes. This concept relies on splitting a functional molecule into inactive fragments, which can be reassembled under specific conditions or stimuli to regain activity. Several binding pairs and orthogonal split fragments are introduced by fusing with other modalities to develop more complex and robust designs. One of the pillars of these splittable systems is modularity, which involves decoupling targeting, activation, and effector functions. Challenges, such as off-target effects and overactivation, can be addressed through precise control. This review provides an overview of the design principles, strategies, and applications of splittable systems across diverse fields including immunotherapy, gene editing, prodrug activation, biosensing, and synthetic biology.
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Affiliation(s)
- Sichen Yuan
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin, Madison (UW-Madison), Madison, Wisconsin 53705, USA.
- Wisconsin Center for NanoBioSystems, University of Wisconsin, Madison (UW-Madison), Madison, Wisconsin 53705, USA
- Carbone Cancer Center, School of Medicine and Public Health, University of Wisconsin, Madison (UW-Madison), Madison, Wisconsin 53705, USA
| | - Alexa Bremmer
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin, Madison (UW-Madison), Madison, Wisconsin 53705, USA.
| | - Xicheng Yang
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin, Madison (UW-Madison), Madison, Wisconsin 53705, USA.
| | - Jiayue Li
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin, Madison (UW-Madison), Madison, Wisconsin 53705, USA.
| | - Quanyin Hu
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin, Madison (UW-Madison), Madison, Wisconsin 53705, USA.
- Wisconsin Center for NanoBioSystems, University of Wisconsin, Madison (UW-Madison), Madison, Wisconsin 53705, USA
- Carbone Cancer Center, School of Medicine and Public Health, University of Wisconsin, Madison (UW-Madison), Madison, Wisconsin 53705, USA
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Anastassov S, Filo M, Khammash M. Inteins: A Swiss army knife for synthetic biology. Biotechnol Adv 2024; 73:108349. [PMID: 38552727 DOI: 10.1016/j.biotechadv.2024.108349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 03/21/2024] [Accepted: 03/23/2024] [Indexed: 04/13/2024]
Abstract
Inteins are proteins found in nature that execute protein splicing. Among them, split inteins stand out for their versatility and adaptability, presenting creative solutions for addressing intricate challenges in various biological applications. Their exquisite attributes, including compactness, reliability, orthogonality, low toxicity, and irreversibility, make them of interest to various fields including synthetic biology, biotechnology and biomedicine. In this review, we delve into the inherent challenges of using inteins, present approaches for overcoming these challenges, and detail their reliable use for specific cellular tasks. We will discuss the use of conditional inteins in areas like cancer therapy, drug screening, patterning, infection treatment, diagnostics and biocontainment. Additionally, we will underscore the potential of inteins in executing basic logical operations with practical implications. We conclude by showcasing their potential in crafting complex genetic circuits for performing computations and feedback control that achieves robust perfect adaptation.
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Affiliation(s)
- Stanislav Anastassov
- Department of Biosystems Science and Engineering, ETH Zürich, Basel 4056, Switzerland
| | - Maurice Filo
- Department of Biosystems Science and Engineering, ETH Zürich, Basel 4056, Switzerland
| | - Mustafa Khammash
- Department of Biosystems Science and Engineering, ETH Zürich, Basel 4056, Switzerland.
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Schmitz M, Ballestin JB, Liang J, Tomas F, Freist L, Voigt K, Di Ventura B, Öztürk MA. Int&in: A machine learning-based web server for active split site identification in inteins. Protein Sci 2024; 33:e4985. [PMID: 38717278 PMCID: PMC11078102 DOI: 10.1002/pro.4985] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 03/06/2024] [Accepted: 03/24/2024] [Indexed: 05/12/2024]
Abstract
Inteins are proteins that excise themselves out of host proteins and ligate the flanking polypeptides in an auto-catalytic process called protein splicing. In nature, inteins are either contiguous or split. In the case of split inteins, the two fragments must first form a complex for the splicing to occur. Contiguous inteins have previously been artificially split in two fragments because split inteins allow for distinct applications than contiguous ones. Even naturally split inteins have been split at unnatural split sites to obtain fragments with reduced affinity for one another, which are useful to create conditional inteins or to study protein-protein interactions. So far, split sites in inteins have been heuristically identified. We developed Int&in, a web server freely available for academic research (https://intein.biologie.uni-freiburg.de) that runs a machine learning model using logistic regression to predict active and inactive split sites in inteins with high accuracy. The model was trained on a dataset of 126 split sites generated using the gp41-1, Npu DnaE and CL inteins and validated using 97 split sites extracted from the literature. Despite the limited data size, the model, which uses various protein structural features, as well as sequence conservation information, achieves an accuracy of 0.79 and 0.78 for the training and testing sets, respectively. We envision Int&in will facilitate the engineering of novel split inteins for applications in synthetic and cell biology.
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Affiliation(s)
- Mirko Schmitz
- BIOSS and CIBSS Research Signalling Centers, University of FreiburgFreiburgGermany
- Institute of Biology II, University of FreiburgFreiburgGermany
- 4HF Biotec GmbHFreiburgGermany
| | - Jara Ballestin Ballestin
- BIOSS and CIBSS Research Signalling Centers, University of FreiburgFreiburgGermany
- Institute of Biology II, University of FreiburgFreiburgGermany
- Bioprocess Innovation Unit, ViraTherapeutics GmbHRumAustria
| | - Junsheng Liang
- BIOSS and CIBSS Research Signalling Centers, University of FreiburgFreiburgGermany
- Institute of Biology II, University of FreiburgFreiburgGermany
| | - Franziska Tomas
- BIOSS and CIBSS Research Signalling Centers, University of FreiburgFreiburgGermany
- Institute of Biology II, University of FreiburgFreiburgGermany
- Department of Molecular Life SciencesUniversity of ZurichZurichSwitzerland
| | - Leon Freist
- Institute of Biology III, University of FreiburgFreiburgGermany
| | - Karsten Voigt
- Institute of Biology III, University of FreiburgFreiburgGermany
| | - Barbara Di Ventura
- BIOSS and CIBSS Research Signalling Centers, University of FreiburgFreiburgGermany
- Institute of Biology II, University of FreiburgFreiburgGermany
| | - Mehmet Ali Öztürk
- BIOSS and CIBSS Research Signalling Centers, University of FreiburgFreiburgGermany
- Institute of Biology II, University of FreiburgFreiburgGermany
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Free K, Nakanishi H, Itaka K. Development of Synthetic mRNAs Encoding Split Cytotoxic Proteins for Selective Cell Elimination Based on Specific Protein Detection. Pharmaceutics 2023; 15:pharmaceutics15010213. [PMID: 36678842 PMCID: PMC9867180 DOI: 10.3390/pharmaceutics15010213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 12/25/2022] [Accepted: 12/30/2022] [Indexed: 01/11/2023] Open
Abstract
For the selective elimination of deleterious cells (e.g., cancer cells and virus-infected cells), the use of a cytotoxic gene is a promising approach. DNA-based systems have achieved selective cell elimination but risk insertional mutagenesis. Here, we developed a synthetic mRNA-based system to selectively eliminate cells expressing a specific target protein. The synthetic mRNAs used in the system are designed to express an engineered protein pair that are based on a cytotoxic protein, Barnase. Each engineered protein is composed of an N- or C-terminal fragment of Barnase, a target protein binding domain, and an intein that aids in reconstituting full-length Barnase from the two fragments. When the mRNAs are transfected to cells expressing the target protein, both N- and C-terminal Barnase fragments bind to the target protein, causing the intein to excise itself and reconstitute cytotoxic full-length Barnase. In contrast, when the target protein is not present, the reconstitution of full-length Barnase is not induced. Four candidate constructs containing split Barnase were evaluated for the ability to selectively eliminate target protein-expressing cells. One of the candidate sets demonstrated highly selective cell death. This system will be a useful therapeutic tool to selectively eliminate deleterious cells.
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Affiliation(s)
| | - Hideyuki Nakanishi
- Correspondence: (H.N.); (K.I.); Tel.: +81-3-5280-8087 (H.N. & K.I.); Fax: +81-3-5280-8088 (H.N. & K.I.)
| | - Keiji Itaka
- Correspondence: (H.N.); (K.I.); Tel.: +81-3-5280-8087 (H.N. & K.I.); Fax: +81-3-5280-8088 (H.N. & K.I.)
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Expanding the Therapeutic Window of EGFR-Targeted PE24 Immunotoxin for EGFR-Overexpressing Cancers by Tailoring the EGFR Binding Affinity. Int J Mol Sci 2022; 23:ijms232415820. [PMID: 36555466 PMCID: PMC9779439 DOI: 10.3390/ijms232415820] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 11/23/2022] [Accepted: 12/09/2022] [Indexed: 12/23/2022] Open
Abstract
Immunotoxins (ITs), which are toxin-fused tumor antigen-specific antibody chimeric proteins, have been developed to selectively kill targeted cancer cells. The epidermal growth factor receptor (EGFR) is an attractive target for the development of anti-EGFR ITs against solid tumors due to its overexpression on the cell surface of various solid tumors. However, the low basal level expression of EGFR in normal tissue cells can cause undesirable on-target/off-tumor toxicity and reduce the therapeutic window of anti-EGFR ITs. Here, based on an anti-EGFR monobody with cross-reactivity to both human and murine EGFR, we developed a strategy to tailor the anti-EGFR affinity of the monobody-based ITs carrying a 24-kDa fragment of Pseudomonas exotoxin A (PE24), termed ER-PE24, to distinguish tumors that overexpress EGFR from normal tissues. Five variants of ER-PE24 were generated with different EGFR affinities (KD ≈ 0.24 nM to 104 nM), showing comparable binding activity for both human and murine EGFR. ER/0.2-PE24 with the highest affinity (KD ≈ 0.24 nM) exhibited a narrow therapeutic window of 19 pM to 93 pM, whereas ER/21-PE24 with an intermediate affinity (KD ≈ 21 nM) showed a much broader therapeutic window of 73 pM to 1.5 nM in in vitro cytotoxic assays using tumor model cell lines. In EGFR-overexpressing tumor xenograft mouse models, the maximum tolerated dose (MTD) of intravenous injection of ER/21-PE24 was found to be 0.4 mg/kg, which was fourfold higher than the MTD (0.1 mg/kg) of ER/0.2-PE24. Our study provides a strategy for the development of IT targeting tumor overexpressed antigens with basal expression in broad normal tissues by tailoring tumor antigen affinities.
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Wu T, Song Z, Huang H, Jakos T, Jiang H, Xie Y, Zhu J. Construction and evaluation of GPC3-targeted immunotoxins as a novel therapeutic modality for hepatocellular carcinoma. Int Immunopharmacol 2022; 113:109393. [DOI: 10.1016/j.intimp.2022.109393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 10/11/2022] [Accepted: 10/24/2022] [Indexed: 11/15/2022]
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Sibuh BZ, Gahtori R, Al-Dayan N, Pant K, Far BF, Malik AA, Gupta AK, Sadhu S, Dohare S, Gupta PK. Emerging trends in immunotoxin targeting cancer stem cells. Toxicol In Vitro 2022; 83:105417. [PMID: 35718257 DOI: 10.1016/j.tiv.2022.105417] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 06/10/2022] [Accepted: 06/11/2022] [Indexed: 12/30/2022]
Abstract
Cancer stem cells (CSCs) are self-renewing multipotent cells that play a vital role in the development of cancer drug resistance conditions. Various therapies like conventional, targeted, and radiotherapies have been broadly used in targeting and killing these CSCs. Among these, targeted therapy selectively targets CSCs and leads to overcoming disease recurrence conditions in cancer patients. Immunotoxins (ITs) are protein-based therapeutics with selective targeting capabilities. These chimeric molecules are composed of two functional moieties, i.e., a targeting moiety for cell surface binding and a toxin moiety that induces the programmed cell death upon internalization. Several ITs have been constructed recently, and their preclinical and clinical efficacies have been evaluated. In this review, we comprehensively discussed the recent preclinical and clinical advances as well as significant challenges in ITs targeting CSCs, which might reduce the burden of drug resistance conditions in cancer patients from bench to bedside.
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Affiliation(s)
- Belay Zeleke Sibuh
- Department of Biotechnology, School of Engineering and Technology (SET), Sharda University, Knowledge Park III, Greater Noida 201310, Uttar Pradesh, India
| | - Rekha Gahtori
- Department of Biotechnology, Sir J.C. Bose Technical Campus, Kumaun University, Bhimtal, Nainital 263136, Uttarakhand, India
| | - Noura Al-Dayan
- Department of Medical Lab Sciences, Prince Sattam bin Abdulaziz University, Alkharj 16278, Saudi Arabia
| | - Kumud Pant
- Department of Biotechnology, Graphic Era Deemed to be University, Dehradun 248002, Uttarakhand, India
| | - Bahareh Farasati Far
- Department of Chemistry, Iran University of Science and Technology, Tehran, Iran
| | - Asrar Ahmad Malik
- Department of Life Sciences, School of Basic Sciences and Research (SBSR), Sharda University, Knowledge Park III, Greater Noida 201310, Uttar Pradesh, India
| | - Ashish Kumar Gupta
- Department of Life Sciences, J.C. Bose University of Science and Technology, YMCA, Faridabad 121006, Haryana, India
| | - Soumi Sadhu
- Department of Life Sciences, School of Basic Sciences and Research (SBSR), Sharda University, Knowledge Park III, Greater Noida 201310, Uttar Pradesh, India
| | - Sushil Dohare
- Department of Epidemiology, Faculty of Public Health & Tropical Medicine, Jazan University, Jazan, Saudi Arabia
| | - Piyush Kumar Gupta
- Department of Biotechnology, Graphic Era Deemed to be University, Dehradun 248002, Uttarakhand, India; Department of Life Sciences, School of Basic Sciences and Research (SBSR), Sharda University, Knowledge Park III, Greater Noida 201310, Uttar Pradesh, India.
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Li M, Mei S, Yang Y, Shen Y, Chen L. Strategies to mitigate the on- and off-target toxicities of recombinant immunotoxins: an antibody engineering perspective. Antib Ther 2022; 5:164-176. [PMID: 35928456 PMCID: PMC9344849 DOI: 10.1093/abt/tbac014] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 10/14/2021] [Accepted: 06/14/2022] [Indexed: 11/14/2022] Open
Abstract
Abstract
Targeted cancer therapies using immunotoxins has achieved remarkable efficacies in hematological malignancies. However, the clinical development of immunotoxins is also faced with many challenges like anti-drug antibodies and dose-limiting toxicity issues. Such a poor efficacy/safety ratio is also the major hurdle in the research and development of antibody-drug conjugates. From an antibody engineering perspective, various strategies were summarized/proposed to tackle the notorious on target off tumor toxicity issues, including passive strategy (XTENylation of immunotoxins) and active strategies (modulating the affinity and valency of the targeting moiety of immunotoxins, conditionally activating immunotoxins in the tumor microenvironments and reconstituting split toxin to reduce systemic toxicity etc.). By modulating the functional characteristics of the targeting moiety and the toxic moiety of immunotoxins, selective tumor targeting can be augmented while sparing the healthy cells in normal tissues expressing the same target of interest. If successful, the improved therapeutic index will likely help to address the dose-limiting toxicities commonly observed in the clinical trials of various immunotoxins.
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Affiliation(s)
- Mengyu Li
- Department of Postgraduate , Jiangxi University of Traditional Chinese Medicine, Nanchang, P.R. China
- Joint Graduate School , Yangtze Delta Drug Advanced Research Institute, Nantong, P.R. China
- Joint Graduate School , Yangtze Delta Pharmaceutical College, Nantong, P.R. China
| | - Sen Mei
- Biotherapeutics , Biocytogen Jiangsu Co. Ltd, Nantong, P.R. China
| | - Yi Yang
- Joint Graduate School , Yangtze Delta Drug Advanced Research Institute, Nantong, P.R. China
- Joint Graduate School , Yangtze Delta Pharmaceutical College, Nantong, P.R. China
- Institute of Innovative Medicine , Biocytogen Pharmaceuticals (Beijing) Co, Ltd, Beijing, P.R. China
| | - Yuelei Shen
- Joint Graduate School , Yangtze Delta Drug Advanced Research Institute, Nantong, P.R. China
- Joint Graduate School , Yangtze Delta Pharmaceutical College, Nantong, P.R. China
- Biotherapeutics , Biocytogen Pharmaceuticals (Beijing) Co, Ltd, Beijing, P.R. China
- Institute of Innovative Medicine , Biocytogen Pharmaceuticals (Beijing) Co, Ltd, Beijing, P.R. China
| | - Lei Chen
- Biotherapeutics , Biocytogen Jiangsu Co. Ltd, Nantong, P.R. China
- Biotherapeutics , Biocytogen Pharmaceuticals (Beijing) Co, Ltd, Beijing, P.R. China
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Tharappel AM, Li Z, Li H. Inteins as Drug Targets and Therapeutic Tools. Front Mol Biosci 2022; 9:821146. [PMID: 35211511 PMCID: PMC8861304 DOI: 10.3389/fmolb.2022.821146] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 01/10/2022] [Indexed: 12/12/2022] Open
Abstract
Multidrug-resistant pathogens are of significant concern in recent years. Hence new antifungal and anti-bacterial drug targets are urgently needed before the situation goes beyond control. Inteins are polypeptides that self-splice from exteins without the need for cofactors or external energy, resulting in joining of extein fragments. Inteins are present in many organisms, including human pathogens such as Mycobacterium tuberculosis, Cryptococcus neoformans, C. gattii, and Aspergillus fumigatus. Because intein elements are not present in human genes, they are attractive drug targets to develop antifungals and antibiotics. Thus far, a few inhibitors of intein splicing have been reported. Metal-ions such as Zn2+ and Cu2+, and platinum-containing compound cisplatin inhibit intein splicing in M. tuberculosis and C. neoformans by binding to the active site cysteines. A small-molecule inhibitor 6G-318S and its derivative 6G-319S are found to inhibit intein splicing in C. neoformans and C. gattii with a MIC in nanomolar concentrations. Inteins have also been used in many other applications. Intein can be used in activating a protein inside a cell using small molecules. Moreover, split intein can be used to deliver large genes in experimental gene therapy and to kill selected species in a mixed population of microbes by taking advantage of the toxin-antitoxin system. Furthermore, split inteins are used in synthesizing cyclic peptides and in developing cell culture model to study infectious viruses including SARS-CoV-2 in the biosafety level (BSL) 2 facility. This mini-review discusses the recent research developments of inteins in drug discovery and therapeutic research.
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Affiliation(s)
- Anil Mathew Tharappel
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ, United States
| | - Zhong Li
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ, United States
| | - Hongmin Li
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ, United States
- BIO5 Institute, The University of Arizona, Tucson, AZ, United States
- *Correspondence: Hongmin Li,
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Abstract
Intervening proteins, or inteins, are mobile genetic elements that are translated within host polypeptides and removed at the protein level by splicing. In protein splicing, a self-mediated reaction removes the intein, leaving a peptide bond in place. While protein splicing can proceed in the absence of external cofactors, several examples of conditional protein splicing (CPS) have emerged. In CPS, the rate and accuracy of splicing are highly dependent on environmental conditions. Because the activity of the intein-containing host protein is compromised prior to splicing and inteins are highly abundant in the microbial world, CPS represents an emerging form of posttranslational regulation that is potentially widespread in microbes. Reactive chlorine species (RCS) are highly potent oxidants encountered by bacteria in a variety of natural environments, including within cells of the mammalian innate immune system. Here, we demonstrate that two naturally occurring RCS, namely, hypochlorous acid (the active compound in bleach) and N-chlorotaurine, can reversibly block splicing of DnaB inteins from Mycobacterium leprae and Mycobacterium smegmatis in vitro. Further, using a reporter that monitors DnaB intein activity within M. smegmatis, we show that DnaB protein splicing is inhibited by RCS in the native host. DnaB, an essential replicative helicase, is the most common intein-housing protein in bacteria. These results add to the growing list of environmental conditions that are relevant to the survival of the intein-containing host and influence protein splicing, as well as suggesting a novel mycobacterial response to RCS. We propose a model in which DnaB splicing, and therefore replication, is paused when these mycobacteria encounter RCS. IMPORTANCE Inteins are both widespread and abundant in microbes, including within several bacterial and fungal pathogens. Inteins are domains translated within host proteins and removed at the protein level by splicing. Traditionally considered molecular parasites, some inteins have emerged in recent years as adaptive posttranslational regulatory elements. Several studies have demonstrated CPS, in which the rate and accuracy of protein splicing, and thus host protein functions, are responsive to environmental conditions relevant to the intein-containing organism. In this work, we demonstrate that two naturally occurring RCS, including the active compound in household bleach, reversibly inhibit protein splicing of Mycobacterium leprae and Mycobacterium smegmatis DnaB inteins. In addition to describing a new physiologically relevant condition that can temporarily inhibit protein splicing, this study suggests a novel stress response in Mycobacterium, a bacterial genus of tremendous importance to humans.
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Wu T, Zhu J. Recent development and optimization of pseudomonas aeruginosa exotoxin immunotoxins in cancer therapeutic applications. Int Immunopharmacol 2021; 96:107759. [PMID: 34162138 DOI: 10.1016/j.intimp.2021.107759] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 04/30/2021] [Accepted: 05/01/2021] [Indexed: 12/12/2022]
Abstract
Recombinant immunotoxins are fusion proteins composed of a peptide toxin and a specific targeting domain through genetic recombination. They are engineered to recognize disease-specific target receptors and kill the cell upon internalization. Full-sized monoclonal antibodies, smaller antibody fragments and ligands, such as a cytokine or a growth factor, have been commonly used as the targeting domain, while bacterial Pseudomonas aeruginosa exotoxin (PE) is the usual toxin fusion partner, due to its natural cytotoxicity and other unique advantages. PE-based recombinant immunotoxins have shown remarkable efficacy in the treatment of tumors and autoimmune diseases. At the same time, efforts are underway to address major challenges, including immunogenicity, nonspecific cytotoxicity and poor penetration, which limit their clinical applications. Recent strategies for structural optimization of PE-based immunotoxins, combined with mutagenesis approaches, have reduced the immunogenicity and non-specific cytotoxicity, thus increasing both their safety and efficacy. This review highlights novel insights and design concepts that were used to advance immunotoxins for the treatment of hematological and solid tumors and also presents future development prospect of PE-based recombinant immunotoxins that are expected to play an important role in cancer therapy.
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Affiliation(s)
- Tong Wu
- Engineering Research Center of Cell and Therapeutic Antibody, MOE, China; School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China.
| | - Jianwei Zhu
- Engineering Research Center of Cell and Therapeutic Antibody, MOE, China; School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China; Jecho Laboratories, Inc., Frederick, MD 21704, USA.
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