Is Methionyl-tRNA Synthetase Applicable as a Diagnostic Marker for Lung Cancer in Bronchial Ultrasound-Guided Brushing Cells?

Background and objective: Methionyl-tRNA synthetase (MARS) and A variant of Aminoacyl-tRNA synthetase interacting multifunctional protein 2 (AIMP2) with an exon 2 deletion (AIMP2-DX2) are known to be overexpressed in lung cancer. However, their role as diagnostic markers in lung cancer has not been well established. Thus, we evaluated their diagnostic performance in brushed cells obtained from nodular lung lesions suspected of lung cancer. Methods: Samples obtained by radial endobronchial ultrasound-guided brushing were processed for cytological examination with Papanicolaou (Pap) staining. Then, double IF staining with MARS and AIMP2-DX2 antibodies was measured in the cytology samples for peripheral lung nodules. The diagnostic performance was compared against biomarkers. Results: MARS IF staining was the only independent staining method used for the prediction of malignant cells. The area under the curve (AUC) of conventional cytology, MARS IF, and MARS IF plus cytology was 0.64, 0.68, and 0.69, respectively. The diagnostic accuracy was increased in MARS IF plus conventional cytology compared with cytology alone (71% vs. 47%). Conclusions: The combination of MARS staining with conventional cytology showed increases in the diagnostic accuracy for diagnosing lung nodules suspected of lung cancer on chest-computed tomography scans.

Identifying potential natural inhibitors of Brucella melitensis Methionyl-tRNA synthetase through an in-silico approach

BackgroundBrucellosis is an infectious disease caused by bacteria of the genus Brucella. Although it is the most common zoonosis worldwide, there are increasing reports of drug resistance and cases of relapse after long term treatment with the existing drugs of choice. This study therefore aims at identifying possible natural inhibitors of Brucella melitensis Methionyl-tRNA synthetase through an in-silico approach.MethodsUsing PyRx 0.8 virtual screening software, the target was docked against a library of natural compounds obtained from edible African plants. The compound, 2-({3-[(3,5-dichlorobenzyl) amino] propyl} amino) quinolin-4(1H)-one (OOU) which is a co-crystallized ligand with the target was used as the reference compound. Screening of the molecular descriptors of the compounds for bioavailability, pharmacokinetic properties, and bioactivity was performed using the SWISSADME, pkCSM, and Molinspiration web servers respectively. The Fpocket and PLIP webservers were used to perform the analyses of the binding pockets and the protein ligand interactions. Analysis of the time-resolved trajectories of the Apo and Holo forms of the target was performed using the Galaxy and MDWeb servers. The lead compounds, Strophanthidin and Isopteropodin are present in Corchorus olitorius and Uncaria tomentosa (cat-claw) plants respectively.ResultsIsopteropodin had a binding affinity score of -8.9 kcal / ml with the target and had 17 anti-correlating residues in pocket 1 after molecular dynamics simulation. The complex formed by Isopteropodin and the target had a total RMSD of 4.408 and a total RMSF of 9.8067. However, Strophanthidin formed 3 hydrogen bonds with the target at ILE21, GLY262 and LEU294, and induced a total RMSF of 5.4541 at Pocket 1.ConclusionOverall, Isopteropodin and Strophanthidin were found to be better drug candidates than OOU and they showed potentials to inhibit the Brucella melitensis Methionyl-tRNA synthetase at Pocket 1, hence abilities to treat brucellosis. In vivo and in vitro investigations are needed to further evaluate the efficacy and toxicity of the lead compounds.Author SummaryStrophanthidin and Isopteropodin showed potentials to inhibit the Brucella melitensis Methionyl-tRNA synthetase at Pocket 1Both compounds can be used to treat brucellosis.Both compounds showed potentials of being safe to use in humans.

Homocysteine Thiolactone: Biology and Chemistry

Homocysteine thiolactone is a five-membered cyclic thioester of amino acid homocysteine. It is generated from homocysteine as a result of an error-editing reaction, principally, of methionyl-tRNA synthetase. An elevated level of homocysteine thiolactone is associated with cardiovascular diseases, strokes, atherosclerosis, neurological abnormalities, etc., presumably because it reacts to the side chain of protein lysine causing protein damage and autoimmune responses. It is not only an important metabolite but also a versatile building block for organic and bioorganic synthesis. This entry contains data on the homocysteine thiolactone formation, metabolism, toxicity mechanism in vivo, and the bioorganic chemistry applications as a powerful synthetic tool in polymer science, sustainable materials development, and probes.

Visualization and Identification of Bioorthogonally Labeled Exosome Proteins Following Systemic Administration in Mice

Exosomes transport biologically active cargo (e.g., proteins and microRNA) between cells, including many of the paracrine factors that mediate the beneficial effects associated with stem-cell therapy. Stem cell derived exosomes, in particular mesenchymal stem cells (MSCs), have been shown previously to largely replicate the therapeutic activity associated with the cells themselves, which suggests that exosomes may be a useful cell-free alternative for the treatment of cardiovascular disorders. However, the mechanisms that govern how exosomes home to damaged cells and tissues or the uptake and distribution of exosomal cargo are poorly characterized, because techniques for distinguishing between exosomal proteins and proteins in the targeted tissues are lacking. Here, we report the development of an in vivo model that enabled the visualization, tracking, and quantification of proteins from systemically administered MSC exosomes. The model uses bioorthogonal chemistry and cell-selective metabolic labeling to incorporate the non-canonical amino acid azidonorleucine (ANL) into the MSC proteome. ANL incorporation is facilitated via expression of a mutant (L274G) methionyl-tRNA-synthetase (MetRS∗) and subsequent incubation with ANL-supplemented media; after which ANL can be covalently linked to alkyne-conjugated reagents (e.g., dyes and resins) via click chemistry. Our results demonstrate that when the exosomes produced by ANL-treated, MetRS∗-expressing MSCs were systemically administered to mice, the ANL-labeled exosomal proteins could be accurately and reliably identified, isolated, and quantified from a variety of mouse organs, and that myocardial infarction (MI) both increased the abundance of exosomal proteins and redistributed a number of them from the membrane fraction of intact hearts to the cytosol of cells in infarcted hearts. Additionally, we found that Desmoglein-1c is enriched in MSC exosomes and taken up by ischemic myocardium. Collectively, our results indicate that this newly developed bioorthogonal system can provide crucial insights into exosome homing, as well as the uptake and biodistribution of exosomal proteins.

A Novel Aminoacyl-tRNA Synthetase Appended Domain Can Supply the Core Synthetase with Its Amino Acid Substrate

The structural organization and functionality of aminoacyl-tRNA synthetases have been expanded through polypeptide additions to their core aminoacylation domain. We have identified a novel domain appended to the methionyl-tRNA synthetase (MetRS) of the intracellular pathogen Mycoplasma penetrans. Sequence analysis of this N-terminal region suggests the appended domain is an aminotransferase, which we demonstrate here. The aminotransferase domain of MpMetRS is capable of generating methionine from its α-keto acid analog, 2-keto-4-methylthiobutyrate (KMTB). The methionine thus produced can be subsequently attached to cognate tRNAMet in the MpMetRS aminoacylation domain. Genomic erosion in the Mycoplasma species has impaired many canonical biosynthetic pathways, causing them to rely on their host for numerous metabolites. It is still unclear if this bifunctional MetRS is a key part of pathogen life cycle or is a neutral consequence of the reductive evolution experienced by Mycoplasma species.

High methionyl–tRNA synthetase expression predicts poor prognosis in patients with breast cancer

AimsMethionyl–tRNA synthetase (MARS) is known to play a critical role in initiating translation and protection against cellular damages in vivo. The aim of this study was to clarify the role of MARS in breast cancer (BC) progression.MethodsThe expressions of MARS messenger RNA (mRNA) and protein in human BC tissues and adjacent non-cancerous tissues were detected by quantitative real-time PCR, western blot and immunohistochemistry. The prognostic potential of MARS in patients with BC was assessed by univariate and multivariate survival analyses. The association between the MARS expression and BC progression was further evaluated by the bioinformatics database of UALCAN, Gene Expression Profiling Interactive Analysis (GEPIA) and Gene Expression Database of Normal and Tumor Tissues (GENT). The role of MARS in the proliferation, migration and epithelial-to-mesenchymal transition (EMT) of human breast cancer cell line (MCF-7 cells) was investigated after siRNA transfection.ResultsThe expression level of MARS mRNA in the fresh BC tissues was significantly higher than that in the adjacent tissues. Immunohistochemistry showed that the expression level of MARS was closely associated with the clinicopathologial parameters of patients with BC, including the HER-2 status, Ki-67 status, molecular classification, tumour grade, N stage and tumour, node, metastasis (TNM) stage, and this finding was further confirmed by UALCAN database. The Kaplan-Meier analysis showed that high MARS expression and TNM stage were predictors of poor prognosis of patients with BC. The proliferation, migration and EMT capabilities of MCF-7 cells were significantly suppressed after MARS knockdown. An overview of UALCAN, GEPIA and GENT results suggested that MARS may be an oncogene of BC, as well as a potential therapeutic target of this malignant tumour.ConclusionsHigh expression level of MARS in the human BC tissues was significantly associated with the unfavourable prognosis of patients with BC, suggesting that MARS may serve as a potential prognostic marker for the clinical diagnosis and prognostic prediction of BC.

Methionyl-tRNA synthetase inhibitor has potent in vivo activity in a novel Giardia lamblia luciferase murine infection model

Background Methionyl-tRNA synthetase (MetRS) inhibitors are under investigation for the treatment of intestinal infections caused by Giardia lamblia. Objectives To properly analyse the therapeutic potential of the MetRS inhibitor 1717, experimental tools including a robust cell-based assay and a murine model of infection were developed based on novel strains of G. lamblia that employ luciferase reporter systems to quantify viable parasites. Methods Systematic screening of Giardia-specific promoters and luciferase variants led to the development of a strain expressing the click beetle green luciferase. Further modifying this strain to express NanoLuc created a dual reporter strain capable of quantifying parasites in both the trophozoite and cyst stages. These strains were used to develop a high-throughput cell assay and a mouse infection model. A library of MetRS inhibitors was screened in the cell assay and Compound-1717 was tested for efficacy in the mouse infection model. Results Cell viability in in vitro compound screens was quantified via bioluminescence readouts while infection loads in mice were monitored with non-invasive whole-animal imaging and faecal analysis. Compound-1717 was effective in clearing mice of Giardia infection in 3 days at varying doses, which was supported by data from enzymatic and phenotypic cell assays. Conclusions The new in vitro and in vivo assays based on luciferase expression by engineered G. lamblia strains are useful for the discovery and development of new therapeutics for giardiasis. MetRS inhibitors, as validated by Compound-1717, have promising anti-giardiasis properties that merit further study as alternative therapeutics.