Serine hydroxymethyltransferase as a potential target of antibacterial agents acting synergistically with one-carbon metabolism-related inhibitors.

Serine hydroxymethyltransferase (SHMT) produces 5,10-methylenetetrahydrofolate (CH2-THF) from tetrahydrofolate with serine to glycine conversion. SHMT is a potential drug target in parasites, viruses and cancer. (+)-SHIN-1 was developed as a human SHMT inhibitor for cancer therapy. However, the potential of SHMT as an antibacterial target is unknown. Here, we show that (+)-SHIN-1 bacteriostatically inhibits the growth of Enterococcus faecium at a 50% effective concentration of 10-11 M and synergistically enhances the antibacterial activities of several nucleoside analogues. Our results, including crystal structure analysis, indicate that (+)-SHIN-1 binds tightly to E. faecium SHMT (efmSHMT). Two variable loops in SHMT are crucial for inhibitor binding, and serine binding to efmSHMT enhances the affinity of (+)-SHIN-1 by stabilising the loop structure of efmSHMT. The findings highlight the potency of SHMT as an antibacterial target and the possibility of developing SHMT inhibitors for treating bacterial, viral and parasitic infections and cancer.

Evaluation of [18F]pitavastatin as a positron emission tomography tracer for in vivo organic transporter polypeptide function.

INTRODUCTION: To understand the pathways involved in drug clearance from the body, quantitative evaluations of the hepatobiliary transport of drugs are important. The organic anion transporting polypeptide (OATP) family transporter, particularly OATP1B1 and 1B3, are considered to play an important role in hepatic uptake of organic anion compounds. Pitavastatin is a substrate of OATP, and it includes a fluorine group. Therefore, it represents an acceptable positron-emission tomography (PET) tracer using fluorine-18 to image in vivo hepatic transporter functions. METHOD: [18F]Pitavastatin was synthesized using the method we previously reported. To evaluate the potential of [18F]pitavastatin in PET imaging of in vivo OATP functions, we investigated the hepatic uptake with/without rifampicin as an OATP inhibitor after administration in normal SD rats. [18F]Pitavastatin metabolite was evaluated using reverse-phase thin-layer chromatography (TLC) autoradiography. We subsequently analyzed the PET image results and demonstrated that [18F]pitavastatin selectively accumulated in the liver post-administration. Result and discussion In metabolite analysis using reverse-phase TLC, we found that the radioactivity detected in the plasma, liver (>90% intact), and bile mostly originated from the parent pitavastatin of the PET study (~40 min). [18F]pitavastatin's hepatic uptake decreased (approximately 76%) with rifampicin co-administration in PET analysis. Because [18F]pitavastatin has lower clearance in rats than other previously reported OATP1B PET s, it holds the potential of an imaging tracer that has a higher sensitivity in monitoring hepatic OATP1B function's changes. CONCLUSION: Compared with the previously reported OATP imaging tracers, [18F]pitavastatin is more suitable for the sensitive detection of functional changes in OATP transporters. We believe that [18F]pitavastatin enables quantitative analysis of the hepatobiliary transport system for organic anion compounds.

18F-Labeled Pyrido[3,4-d]pyrimidine as an Effective Probe for Imaging of L858R Mutant Epidermal Growth Factor Receptor.

In nonsmall-cell lung carcinoma patients, L858R mutation of epidermal growth factor receptor (EGFR) is often found, and molecular target therapy using EGFR tyrosine kinase inhibitors is effective for the patients. However, the treatment frequently develops drug resistance by secondary mutation, of which approximately 50% is T790M mutation. Therefore, the ability to predict whether EGFR will undergo secondary mutation is extremely important. We synthesized a novel radiofluorinated 4-(anilino)pyrido[3,4-d]pyrimidine derivative ([18F]APP-1) and evaluated its potential as a positron emission tomography (PET) imaging probe to discriminate the difference in mutations of tumors. EGFR inhibition assay, cell uptake, and biodistribution study showed that [18F]APP-1 binds specifically to the L858R mutant EGFR but not to the L858R/T790M mutant. Finally, on PET imaging study using [18F]APP-1 with tumor-bearing mice, the H3255 tumor (L858R mutant) was more clearly visualized than the H1975 tumor (L858R/T790M mutant).

Reconstruction of monocyte transcriptional regulatory network accompanies monocytic functions in human fibroblasts.

Transcriptional regulatory networks (TRN) control the underlying mechanisms behind cellular functions and they are defined by a set of core transcription factors regulating cascades of peripheral genes. Here we report SPI1, CEBPA, MNDA and IRF8 as core transcription factors of monocyte TRN and demonstrate functional inductions of phagocytosis, inflammatory response and chemotaxis activities in human dermal fibroblasts. The Gene Ontology and KEGG pathway analyses also revealed notable representation of genes involved in immune response and endocytosis in fibroblasts. Moreover, monocyte TRN-inducers triggered multiple monocyte-specific genes based on the transcription factor motif response analysis and suggest that complex cellular TRNs are uniquely amenable to elicit cell-specific functions in unrelated cell types.