RESUMO
Six new macrophilone-type pyrroloiminoquines were isolated and identified from an extract of the marine hydroid Macrorhynchia philippina. The proton-deficient and heteroatom-rich structures of macrophilones B-G (2-7) were elucidated by spectroscopic analysis and comparison of their data with those of the previously reported metabolite macrophilone A (1). Compounds 1-7 are the first pyrroloiminoquines to be reported from a hydroid. The macrophilones were shown to inhibit the enzymatic conjugation of SUMO to peptide substrates, and macrophilones A (1) and C (3) exhibit potent and selective cytotoxic properties in the NCI-60 anticancer screen. Bioinformatic analysis revealed a close association of the cytotoxicity profiles of 1 and 3 with two known B-Raf kinase inhibitory drugs. While compounds 1 and 3 showed no kinase inhibitory activity, they resulted in a dramatic decrease in cellular protein levels of selected components of the ERK signal cascade. As such, the chemical scaffold of the macrophilones could provide small-molecule therapeutic leads that target the ERK signal transduction pathway.
Assuntos
Hidrozoários/química , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Pirroliminoquinonas/isolamento & purificação , Animais , Antineoplásicos/isolamento & purificação , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Estrutura Molecular , Pirroliminoquinonas/farmacologia , Sumoilação/efeitos dos fármacosRESUMO
Approaches to characterize the nucleic acid-binding properties of drugs and druglike small molecules are crucial to understanding the behavior of these compounds in cellular systems. Here, we use a Small Molecule Microarray (SMM) profiling approach to identify the preferential interaction between chlorhexidine, a widely used oral antiseptic, and the G-quadruplex (G4) structure in the KRAS oncogene promoter. The interaction of chlorhexidine and related drugs to the KRAS G4 is evaluated using multiple biophysical methods, including thermal melt, fluorescence titration and surface plasmon resonance (SPR) assays. Chlorhexidine has a specific low micromolar binding interaction with the G4, while related drugs have weaker and/or less specific interactions. Through NMR experiments and docking studies, we propose a plausible binding mode driven by both aromatic stacking and groove binding interactions. Additionally, cancer cell lines harbouring oncogenic mutations in the KRAS gene exhibit increased sensitivity to chlorhexidine. Treatment of breast cancer cells with chlorhexidine decreases KRAS protein levels, while a KRAS gene transiently expressed by a promoter lacking a G4 is not affected. This work confirms that known ligands bind broadly to G4 structures, while other drugs and druglike compounds can have more selective interactions that may be biologically relevant.
Assuntos
Anti-Infecciosos Locais/metabolismo , Clorexidina/metabolismo , Quadruplex G , Bibliotecas de Moléculas Pequenas/metabolismo , Anti-Infecciosos Locais/farmacologia , Sítios de Ligação , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Clorexidina/farmacologia , DNA/genética , DNA/metabolismo , Expressão Gênica/efeitos dos fármacos , Humanos , Ligantes , Espectroscopia de Ressonância Magnética , Regiões Promotoras Genéticas/genética , Proteínas Proto-Oncogênicas p21(ras)/genética , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Bibliotecas de Moléculas Pequenas/farmacologia , Ressonância de Plasmônio de SuperfícieRESUMO
A previously uncharacterized pyrroloiminoquinone natural product, macrophilone A, was isolated from the stinging hydroid Macrorhynchia philippina. The structure was assigned utilizing long-range NMR couplings and DFT calculations and proved by a concise, five-step total synthesis. Macrophilone A and a synthetic analogue displayed potent biological activity, including increased intracellular reactive oxygen species levels and submicromolar cytotoxicity toward lung adenocarcinoma cells.
Assuntos
Quinonas/química , Produtos Biológicos , Estrutura Molecular , Espécies Reativas de OxigênioRESUMO
Conjugation of the small ubiquitin-like modifier (SUMO) to protein substrates is an important disease-associated posttranslational modification, although few inhibitors of this process are known. Herein, we report the discovery of an allosteric small-molecule binding site on Ubc9, the sole SUMO E2 enzyme. An X-ray crystallographic screen was used to identify two distinct small-molecule fragments that bind to Ubc9 at a site distal to its catalytic cysteine. These fragments and related compounds inhibit SUMO conjugation in biochemical assays with potencies of 1.9-5.8â mm. Mechanistic and biophysical analyses, coupled with molecular dynamics simulations, point toward ligand-induced rigidification of Ubc9 as a mechanism of inhibition.