| 1. |
- Li, Lanfen, et al.
(författare)
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Structural genomics studies of human caries pathogen Streptococcus mutans
- 2014
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Ingår i: Journal of Structural and Functional Genomics. - : Springer Science and Business Media LLC. - 1345-711X .- 1570-0267. ; 15:3, s. 9-91
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Tidskriftsartikel (refereegranskat)abstract
- Gram-positive bacterium Streptococcus mutans is the primary causative agent of human dental caries. To better understand this pathogen at the atomic structure level and to establish potential drug and vaccine targets, we have carried out structural genomics research since 2005. To achieve the goal, we have developed various in-house automation systems including novel high-throughput crystallization equipment and methods, based on which a large-scale, high-efficiency and low-cost platform has been establish in our laboratory. From a total of 1,963 annotated open reading frames, 1,391 non-membrane targets were selected prioritized by protein sequence similarities to unknown structures, and clustered by restriction sites to allow for cost-effective high-throughput conventional cloning. Selected proteins were over-expressed in different strains of Escherichia coli. Clones expressed soluble proteins were selected, expanded, and expressed proteins were purified and subjected to crystallization trials. Finally, protein crystals were subjected to X-ray analysis and structures were determined by crystallographic methods. Using the previously established procedures, we have so far obtained more than 200 kinds of protein crystals and 100 kinds of crystal structures involved in different biological pathways. In this paper we demonstrate and review a possibility of performing structural genomics studies at moderate laboratory scale. Furthermore, the techniques and methods developed in our study can be widely applied to conventional structural biology research practice.
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| 2. |
- Colicchia, Valeria, et al.
(författare)
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New regulators of the tetracycline‐inducible gene expression system identified by chemical and genetic screens
- 2022
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Ingår i: FEBS Open Bio. - : Wiley-Blackwell. - 2211-5463. ; 12:10, s. 1896-1908
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Tidskriftsartikel (refereegranskat)abstract
- The tetracycline repressor (tetR)-regulated system is a widely used tool to specifically control gene expression in mammalian cells. Based on this system, we generated a human osteosarcoma cell line, which allows for the inducible expression of an EGFP fusion of the TAR DNA-binding protein 43 (TDP-43), which has been linked to neurodegenerative diseases. Consistent with previous findings, TDP-43 overexpression led to the accumulation of aggregates and limited the viability of U2OS. Using this inducible system, we conducted a chemical screen with a library that included FDA-approved drugs. While the primary screen identified several compounds that prevented TDP-43 toxicity, further experiments revealed that these chemicals abrogated the doxycycline-dependent TDP-43 expression. This antagonistic effect was observed with both doxycycline and tetracycline, and in several Tet-On cell lines expressing different genes, confirming the general effect of these compounds as inhibitors of the tetR system. Using the same cell line, a genome-wide CRISPR/Cas9 screen identified epigenetic regulators such as the G9a methyltransferase and TRIM28 as potential modifiers of TDP-43 toxicity. Yet again, further experiments revealed that G9a inhibition or TRIM28 loss prevented doxycycline-dependent expression of TDP-43. In summary, we have identified new chemical and genetic regulators of the tetR system, thereby raising awareness of the limitations of this approach to conduct chemical or genetic screening in mammalian cells.
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| 3. |
- Li, Xuexin
(författare)
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Computational and chemical approaches to drug repurposing
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Drug repurposing, which entails discovering novel therapeutic applications for already existing drugs, provides numerous benefits compared to conventional drug discovery methods. This strategy can be pursued through two primary approaches: computational and chemical. Computational methods involve the utilization of data mining and bioinformatics techniques to identify potential drug candidates, while chemical approaches involve experimental screens oriented to finding new potential treatments based on existing drugs. Both computational and chemical methods have proven successful in uncovering novel therapeutic uses for established drugs. During my PhD, I participated in several experimental drug repurposing screens based on high-throughput phenotypic approaches. Finally, attracted by the potential of computational drug repurposing pipelines, I decided to contribute and generate a web platform focused on the use of transcriptional signatures to identify potential new treatments for human disease. A summary of these studies follows: In Study I, we utilized the tetracycline repressor (tetR)-regulated mechanism to create a human osteosarcoma cell line (U2OS) with the ability to express TAR DNA-binding protein 43 (TDP-43) upon induction. TDP-43 is a protein known for its association with several neurodegenerative diseases. We implemented a chemical screening with this system as part of our efforts to repurpose approved drugs. While the screening was unsuccessful to identify modulators of TDP-43 toxicity, it revealed compounds capable of inhibiting the doxycyclinedependent TDP-43 expression. Furthermore, a complementary CRISPR/Cas9 screening using the same cell system identified additional regulators of doxycycline-dependent TDP43 expression. This investigation identifies new chemical and genetic modulators of the tetR system and highlights potential limitations of using this system for chemical or genetic screenings in mammalian cells. In Study II, our objective was to reposition compounds that could potentially reduce the toxic effects of a fragment of the Huntingtin (HTT) protein containing a 94 amino acid long glutamine stretch (Htt-Q94), a feature of Huntington's disease (HD). To achieve this, we carried out a high-throughput chemical screening using a varied collection of 1,214 drugs, largely sourced from a drug repurposing library. Through our screening process, we singled out clofazimine, an FDA-approved anti-leprosy drug, as a potential therapeutic candidate. Its effectiveness was validated across several in vitro models as well as a zebrafish model of polyglutamine (polyQ) toxicity. Employing a combination of computational analysis of transcriptional signatures, molecular modeling, and biochemical assays, we deduced that clofazimine is an agonist for the peroxisome proliferator-activated receptor gamma (PPARγ), a receptor previously suggested to be a viable therapeutic target for HD due to its role in promoting mitochondrial biogenesis. Notably, clofazimine was successful in alleviating the mitochondrial dysfunction triggered by the expression of Htt-Q94. These findings lend substantial support to the potential of clofazimine as a viable candidate for drug repurposing in the treatment of polyQ diseases. In Study III, we explored the molecular mechanism of a previously identified repurposing example, the use of diethyldithiocarbamate-copper complex (CuET), a disulfiram metabolite, for cancer treatment. We found CuET effectively inhibits cancer cell growth by targeting the NPL4 adapter of the p97VCP segregase, leading to translational arrest and stress in tumor cells. CuET also activates ribosomal biogenesis and autophagy in cancer cells, and its cytotoxicity can be enhanced by inhibiting these pathways. Thus, CuET shows promise as a cancer treatment, especially in combination therapies. In Study IV, we capitalized on the Molecular Signatures Database (MSigDB), one of the largest signature repositories, and drug transcriptomic profiles from the Connectivity Map (CMap) to construct a comprehensive and interactive drug-repurposing database called the Drug Repurposing Encyclopedia (DRE). Housing over 39.7 million pre-computed drugsignature associations across 20 species, the DRE allows users to conduct real-time drugrepurposing analysis. This can involve comparing user-supplied gene signatures with existing ones in the DRE, carrying out drug-gene set enrichment analyses (drug-GSEA) using submitted drug transcriptomic profiles, or conducting similarity analyses across all database signatures using user-provided gene sets. Overall, the DRE is an exhaustive database aimed at promoting drug repurposing based on transcriptional signatures, offering deep-dive comparisons across molecular signatures and species. Drug repurposing presents a valuable strategy for discovering fresh therapeutic applications for existing drugs, offering numerous benefits compared to conventional drug discovery methods. The studies conducted in this thesis underscore the potential of drug repurposing and highlight the complementary roles of computational and chemical approaches. These studies enhance our understanding of the mechanistic properties of repurposed drugs, such as clofazimine and disulfiram, and reveal novel mechanisms for targeting specific disease pathways. Additionally, the development of the DRE platform provides a comprehensive tool to support researchers in conducting drug-repositioning analyses, further facilitating the advancement of drug repurposing studies.
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| 4. |
- Li, Xuexin, et al.
(författare)
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The anti-leprosy drug clofazimine reduces polyQ toxicity through activation of PPARγ
- 2024
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Ingår i: EBioMedicine. - 2352-3964. ; 103
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Tidskriftsartikel (refereegranskat)abstract
- Background: PolyQ diseases are autosomal dominant neurodegenerative disorders caused by the expansion of CAG repeats. While of slow progression, these diseases are ultimately fatal and lack effective therapies. Methods: A high-throughput chemical screen was conducted to identify drugs that lower the toxicity of a protein containing the first exon of Huntington's disease (HD) protein huntingtin (HTT) harbouring 94 glutamines (Htt-Q94). Candidate drugs were tested in a wide range of in vitro and in vivo models of polyQ toxicity. Findings: The chemical screen identified the anti-leprosy drug clofazimine as a hit, which was subsequently validated in several in vitro models. Computational analyses of transcriptional signatures revealed that the effect of clofazimine was due to the stimulation of mitochondrial biogenesis by peroxisome proliferator-activated receptor gamma (PPARγ). In agreement with this, clofazimine rescued mitochondrial dysfunction triggered by Htt-Q94 expression. Importantly, clofazimine also limited polyQ toxicity in developing zebrafish and neuron-specific worm models of polyQ disease. Interpretation: Our results support the potential of repurposing the antimicrobial drug clofazimine for the treatment of polyQ diseases. Funding: A full list of funding sources can be found in the acknowledgments section.
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