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Organismal adaptations to environmental stimuli are governed by intracellular signaling molecules such as nucleotide second messengers. Recent studies have identified functional roles for the noncanonical 2′,3′-cyclic nucleotide monophosphates (2′,3′-cNMPs) in both eukaryotes and prokaryotes. In Escherichia coli, 2′,3′-cNMPs are produced by RNase I-catalyzed RNA degradation, and these cyclic nucleotides modulate biofilm formation through unknown mechanisms. The present work dissects cellular processes in E. coli and Salmonella enterica serovar Typhimurium that are modulated by 2′,3′-cNMPs through the development of cell-permeable 2′,3′-cNMP analogs and a 2′,3′-cyclic nucleotide phosphodiesterase. Utilization of these chemical and enzymatic tools, in conjunction with phenotypic and transcriptomic investigations, identified pathways regulated by 2′,3′-cNMPs, including flagellar motility and biofilm formation, and by oligoribonucleotides with 3′-terminal 2′,3′-cyclic phosphates, including responses to cellular stress. Furthermore, interrogation of metabolomic and organismal databases has identified 2′,3′-cNMPs in numerous organisms and homologs of the E. coli metabolic proteins that are involved in key eukaryotic pathways. Thus, the present work provides key insights into the roles of these understudied facets of nucleotide metabolism and signaling in prokaryotic physiology and suggest broad roles for 2′,3′-cNMPs among bacteria and eukaryotes. IMPORTANCE Bacteria adapt to environmental challenges by producing intracellular signaling molecules that control downstream pathways and alter cellular processes for survival. Nucleotide second messengers serve to transduce extracellular signals and regulate a wide array of intracellular pathways. Recently, 2′,3′-cyclic nucleotide monophosphates (2′,3′-cNMPs) were identified as contributing to the regulation of cellular pathways in eukaryotes and prokaryotes. In this study, we define previously unknown cell processes that are affected by fluctuating 2′,3′-cNMP levels or RNA oligomers with 2′,3′-cyclic phosphate termini in E. coli and Salmonella Typhimurium, providing a framework for studying novel signaling networks in prokaryotes. Furthermore, we utilize metabolomics databases to identify additional prokaryotic and eukaryotic species that generate 2′,3′-cNMPs as a resource for future studies.

Respiration is key to growth of acetotrophic Archaea that generate most of the 109 metric-ton annual production of methane., Although two-thirds of the nearly 1 billion metric tons of methane produced annually in Earth’s biosphere derives from acetate, the in situ process has escaped rigorous understanding. The unresolved question concerns the mechanism by which the exceptionally marginal amount of available energy supports acetotrophic growth of methanogenic archaea in the environment. Here, we show that Methanosarcina acetivorans conserves energy by Fe(III)-dependent respiratory metabolism of acetate, augmenting production of the greenhouse gas methane. An extensively revised, ecologically relevant, biochemical pathway for acetotrophic growth is presented, in which the conservation of respiratory energy is maximized by electron bifurcation, a previously unknown mechanism of biological energy coupling. The results transform the ecological and biochemical understanding of methanogenesis and the role of iron in the mineralization of organic matter in anaerobic environments.

A novel series of highly diverse indole-2-carboxamides was synthesized utilizing the isocyanide based multicomponent reaction (IMCR)-post modification approach and were identified as potential antileishmanial chemotype. Among the synthesized 18 analogues, 12 analogues exhibited better antileishmanial activity against intracellular amastigotes form of Leishmania donovani (IC50 values of 0.6-7.5 μM) as compared to standard drugs miltefosine and sodium stibogluconate. The compounds were also non-toxic towards Vero cells. Compounds 2b, 2m and 2p with significant in vitro activity were then evaluated for their in vivo efficacy following intraperitoneal route. These three compounds at a concentration of 50 mg/kg/day for 5 consecutive days showed 70.0, 63.5 and 63.4% inhibition of Leishmania amastigotes, respectively at day 7 post treatment in hamster model of visceral leishmaniasis.

Trypanothione reductase (TR) is a vital enzyme in the trypanothione based redox metabolism of trypanosomatid parasites. It is one of the few chemically validated targets for Leishmania. Herein, we report the synthesis of novel β-carboline–quinazolinone hybrids that are able to inhibit Leishmania donovani TR (LdTR) and subsequently inhibit cell growth. A molecular modeling approach based on docking studies and subsequent binding free energy estimation was performed in the active site of LdTR to understand their possible binding sites. With the enzymatic assay on LdTR with compounds, we were able to identify six hit compounds (8j–8o) that were all found to be the competitive inhibitors of TR with Ki in the range of 0.8–9.2 μM. The whole-cell screening assay highlighted the analogues 8k, 8l and 8n as the most active compounds with IC50 of 4.4, 6.0 and 4.3 μM, respectively, along with an adequate selectivity index (SI) of >91, 36 and 24, respectively.

Mouse double minute 2 (MDM2) protein functionally inactivates the tumor suppressor p53 in human cancer. Conventional MDM2 inhibitors provide limited clinical application as they interfere only with the MDM2-p53 interaction to release p53 from MDM2 sequestration but do not prevent activated p53 from transcriptionally inducing MDM2 expression. Here, we report a rationally synthesized chalcone-based pyrido[ b ]indole, CPI-7c, as a unique small-molecule inhibitor of MDM2, which not only inhibited MDM2-p53 interaction but also promoted MDM2 degradation. CPI-7c bound to both RING and N-terminal domains of MDM2 to promote its ubiquitin-mediated degradation and p53 stabilization. CPI-7c-induced p53 directly recruited to the promoters of DR4 and DR5 genes and enhanced their expression, resulting in sensitization of TNF-related apoptosis-inducing ligand (TRAIL)-resistant cancer cells toward TRAIL-induced apoptosis. Collectively, we identified CPI-7c as a novel small-molecule inhibitor of MDM2 with a unique two-prong mechanism of action that sensitized TRAIL-resistant cancer cells to apoptosis by modulating the MDM2-p53-DR4/DR5 pathway.

A series of indolylglyoxylamide derivatives have been synthesized and evaluated in vitro against amastigote form of Leishmania donovani. Compound 8c has been identified as the most active analog of the series with IC(50) value of 5.17μM and SI value of 31.48, and is several folds more potent than the standard drugs sodium stilbogluconate and pentamidine.

In an attempt to synthesize pentamidine-aplysinopsin hybrid molecule 25, a lead molecule 8 (containing Z-configured aplysinopsin moiety) was identified for antileishmanial activity. Optimization of lead 8 provided 24 (containing E-configured aplysinopsin) possessing 10 times more activity and 401-fold less toxicity than the drug pentamidine in cell based assays. Synthesis of 24 was possible, surprisingly, because of two innate reactivities of indole-3-carbaldehyde which provided it in diastereo- and regio-selectively pure form without recourse to the long reaction pathway.

Trypanothione reductase (TR) is essential for the survival of the protozoan parasite Leishmania, and, therefore, offers a promising target for the development of selective new drugs against Leishma...

A series of novel β-carboline based chalcones was synthesized and evaluated for their cytotoxic activity against a panel of human cancer cell lines. Among them we found that two of the compounds 7c and 7d, showed marked anti-proliferative activity in a panel of solid tumor cell lines with highest effect in breast cancer. The compounds 7c and 7d showed an IC50 of 2.25 and 3.29 μM, respectively against human breast cancer MCF-7 cell line. Further, the compound 7c markedly induced DNA fragmentation and apoptosis in breast cancer cells.

Artemisinin, with its 1,2,4-trioxane as active motif, is now the first-line treatment for multidrug-resistant malaria. The endoperoxide ring is essential for the antimalarial activity of artemisinin. Based on its mechanism of action, new hybrid molecules named trioxaquines with a dual mode of action have been designed. Trioxaquines are made by the covalent attachment of a trioxane, having alkylating ability, to a quinoline, known to easily penetrate within infected erythrocytes. This review discusses the importance of various hybrid molecules of artemisinin and 4-aminoquinoline in the treatment of malaria and the evolution of a trioxaquine hybrid as a promising antimalarial drug candidate.