The Ca-loop in thymidylate kinase is critical for growth and contributes to pyrimidine drug sensitivity of Candida albicans

GPX3-Mediated Oxidative Stress Affects Pyrimidine Metabolism Levels in Stomach Adenocarcinoma via the AMPK/mTOR Pathway

Background

Amino acid metabolism, including ATP production, nucleotide synthesis, and redox homeostatic processes, are associated with proliferation and differentiation of tumor cells. This study aimed to identify novel prognostic biomarkers and potential therapeutic targets of amino acid metabolism-related genes for stomach adenocarcinoma (STAD).

Methods

RNA sequencing transcriptome data in the TCGA-STAD (training set) and GTEx datasets (validation set) were used. The LIMMA R program enabled the differentially expressed amino acid metabolism-related genes (AAMRGs) to be found. A prognostic risk score model based on clinical phenotypic features was built using LASSO regression and step multi-Cox analyses. Gene set enrichment analysis (GSEA) was used to find potential molecular pathways associated with STAD. Hierarchical cluster analysis was used to evaluate pyrimidine metabolism. Cultured STAD cells assessed the proliferation of STAD and upregulation of GPX3 expression by CCK8 and flow cytometry. Transwell and wound healing assays assessed the impact of GPX3 on invasion and migration of STAD cells. Western blot and qRT-PCR were used to measure changes in pyrimidine metabolism-related markers and active molecules involved in the AMPK/mTOR signaling pathway.

Results

Three AAMRGs, DNMT1, F2R, and GPX3, could independently predict the course of STAD. Pyrimidine metabolism appeared to be significantly associated with these by GSEA and clustering analyses. Pyrimidine metabolism was negatively correlated with GPX3. Functional studies using an overexpressed GPX3 plasmid showed an enhanced migration and invasion of STAD cells as well as the expression of genes associated with pyrimidine metabolism and the AMPK/mTOR signaling pathway. By using a CAD siRNA, it was found that that GPX3 affected 5-fluorouracil resistance during de novo synthesis of pyrimidine through the CAD-UMPS signaling axis.

Conclusions

GPX3 which regulates the level of pyrimidine metabolism through the AMPK/mTOR pathway was found to be closely associated with STAD. Our findings demonstrate GPX3 is a reliable biomarker for the prognosis of amino acid metabolism and a probable target for STAD therapy.

Sertraline has fungicidal activity against Candida spp. and acts by inhibiting membrane and cell wall biosynthesis

Aim: Our study evaluated the activity of sertraline (SER) alone and associated with antifungal drugs in planktonic Candida spp. strains, and investigated its mechanism of action. Materials & methods: Broth microdilution method and minimum fungicidal concentration/MIC ratio were used to assess SER anticandidal activity, and the interaction with antifungals was determined by fractional inhibitory concentration index. The mechanism of action was investigated by flow cytometry and in silico tests. Results: SER inhibited Candida spp. strains at low concentrations by the fungicidal effect and showed no loss of effectiveness when combined. Its action seemed to be related to the membrane and cell wall biosynthesis inhibition. Conclusion: SER has activity against Candida spp. isolated and associated with antifungals, and acts by causing cell wall and membrane damage.

Antifungal activity of cisatracurium against fluconazole-resistant Candida isolates and its antibiofilm effects

Aim: To evaluate the antifungal activity of cisatracurium against Candida spp. resistant to fluconazole strains in planktonic and biofilm forms, in addition to determining its mechanism of action. Materials & methods: Antifungal activity and pharmacological interactions were determined using broth microdilution methods and the mechanism of action was evaluated by flow cytometry and molecular docking. Results: Cisatracurium presented antifungal activity against Candida spp. planktonic cells due to alterations of mitochondrial transmembrane potential leading to cellular apoptosis in addition to interacting with important targets related to cellular respiration, membrane and cell wall evidenced by molecular docking. Furthermore, the drug both prevented biofilm formation and impaired mature biofilms. Conclusion: Cisatracurium exhibits potential antifungal activity against Candida spp.

Long non-coding RNA terminal differentiation-induced non-coding RNA regulates cisplatin resistance of choroidal melanoma by positively modulating extracellular signal-regulated kinase 2 via sponging microRNA-19b-3p

In the present study, we aimed to investigate the role of long non-coding RNA terminal differentiation-induced non-coding RNA (TINCR) in cisplatin (DDP) resistance of choroidal melanoma (CM) and the potential molecular mechanisms. CM and non-CM tissues were collected from 60 CM patients. DDP-resistant CM cells were obtained by selection with linearly increased DDP treatment. The expression levels of TINCR, microR-19b-3p (miR-19b-3p), and extracellular signal-regulated kinase 2 (ERK-2) were detected by quantitative real-time PCR. Cholecystokinin octapeptide (CCK-8) assay was utilized to detect chemosensitivity and cell viability. Flow cytometry analysis was performed to detect apoptotic cells. The protein levels of Bax, Bcl-2, cleaved-caspase-3, ERK-2, and nuclear factor-kappa B p65 were measured by Western blot. RNA immunoprecipitation (RIP) and dual-luciferase reporter assays were performed to determine the relationship among TINCR, miR-19b-3p, and ERK-2. The results showed that the levels of TINCR and ERK-2 were markedly increased in DDP-resistant CM tissues and cells, while miR-19b-3p level was significantly reduced. TINCR knockdown reduced DDP resistance and cell viability and promoted cell apoptosis, while TINCR overexpression exhibited opposite effects. TINCR and ERK-2 were direct targets of miR-19b-3p. Further experiments revealed that TINCR enhanced DDP resistance in CM cells by regulating the miR-19b-3p/ERK-2/NF-kb axis. Taken together, our study revealed a critical role of TINCR in regulating DDP resistance in CM and suggested that TINCR is a potential cisplatin-resistant CM therapeutic target.

CRISPR-Based Genetic Manipulation of Candida Species: Historical Perspectives and Current Approaches

The Candida genus encompasses a diverse group of ascomycete fungi that have captured the attention of the scientific community, due to both their role in pathogenesis and emerging applications in biotechnology; the development of gene editing tools such as CRISPR, to analyze fungal genetics and perform functional genomic studies in these organisms, is essential to fully understand and exploit this genus, to further advance antifungal drug discovery and industrial value. However, genetic manipulation of Candida species has been met with several distinctive barriers to progress, such as unconventional codon usage in some species, as well as the absence of a complete sexual cycle in its diploid members. Despite these challenges, the last few decades have witnessed an expansion of the Candida genetic toolbox, allowing for diverse genome editing applications that range from introducing a single point mutation to generating large-scale mutant libraries for functional genomic studies. Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 technology is among the most recent of these advancements, bringing unparalleled versatility and precision to genetic manipulation of Candida species. Since its initial applications in Candida albicans, CRISPR-Cas9 platforms are rapidly evolving to permit efficient gene editing in other members of the genus. The technology has proven useful in elucidating the pathogenesis and host-pathogen interactions of medically relevant Candida species, and has led to novel insights on antifungal drug susceptibility and resistance, as well as innovative treatment strategies. CRISPR-Cas9 tools have also been exploited to uncover potential applications of Candida species in industrial contexts. This review is intended to provide a historical overview of genetic approaches used to study the Candida genus and to discuss the state of the art of CRISPR-based genetic manipulation of Candida species, highlighting its contributions to deciphering the biology of this genus, as well as providing perspectives for the future of Candida genetics.

Conformational diversity defines substrate specificity of thymidylate/uridylate kinase from Candida albicans

Thymidylate kinase (TMK) from Candida albicans (CaTMK) contains a unique 15 residue insert, the CaLoop, that is not found on other TMKs. CaTMK is proficient at phosphorylating deoxyuridine monophosphate (dUMP), showing a rate 6-fold higher than TMP. It has been shown that deletion of the CaLoop reduces the activity towards dUMP by 19-fold, but has only a modest 4-fold decrease in activity towards TMP. The molecular dynamics calculations presented here show that the increased activity towards dUMP is due to an increase in flexibility and correlated motions of the protein that allows the enzyme-dUMP complex to more readily approach a catalytically competent state. Deletion of the CaLoop allows the dUMP-enzyme complex to adopt catalytically non-functional conformations. In contrast, TMP stabilizes the deletion such that it remains in a functional conformation that is similar to the conformation of the original enzyme.

Stabilization of Active Site Dynamics Leads to Increased Activity with 3'-Azido-3'-deoxythymidine Monophosphate for F105Y Mutant Human Thymidylate Kinase

Thymidylate kinases are essential enzymes with roles in DNA synthesis and repair and have been the target of drug development for antimalarials, antifungals, HIV treatment, and cancer therapeutics. Human thymidylate kinase (hTMPK) conversion of the anti-HIV prodrug 3'-azido-3'-deoxythymidine (AZT or zidovudine) monophosphate to diphosphate is the rate-limiting step in the activation of AZT. A point mutant (F105Y) has been previously reported with significantly increased activity for the monophosphate form of the drug [3'-azidothymidine-5'-monophosphate (AZTMP)]. Using solution nuclear magnetic resonance (NMR) techniques, we show that while the wild-type (WT) and F105Y hTMPK adopt the same structure in solution, significant changes in dynamics may explain their different activities toward TMP and AZTMP. ¹³C spin-relaxation measurements show that there is little change in dynamics on the ps to ns time scale. In contrast, methyl ¹H relaxation dispersion shows that AZTMP alters adenosine nucleotide handling in the WT protein but not in the mutant. Additionally, the F105Y mutant has reduced conformational flexibility, leading to an increase in affinity for the product ADP and a slower rate of phosphorylation of TMP. The dynamics at the catalytic center for F105Y bound to AZTMP are tuned to the same frequency as WT bound to TMP, which may explain the mutant's catalytic efficiency toward the prodrug.