Many protein kinases are valid drug targets in oncology because they are key components of signal transduction pathways. The number of clinical kinase inhibitors is on the rise, but these molecules ...often exhibit polypharmacology, potentially eliciting desired and toxic effects. Therefore, a comprehensive assessment of a compound’s target space is desirable for a better understanding of its biological effects. The enzyme ferrochelatase (FECH) catalyzes the conversion of protoporphyrin IX into heme and was recently found to be an off-target of the BRAF inhibitor Vemurafenib, likely explaining the phototoxicity associated with this drug in melanoma patients. This raises the question of whether FECH binding is a more general feature of kinase inhibitors. To address this, we applied a chemical proteomics approach using kinobeads to evaluate 226 clinical kinase inhibitors for their ability to bind FECH. Surprisingly, low or submicromolar FECH binding was detected for 29 of all compounds tested and isothermal dose response measurements confirmed target engagement in cells. We also show that Vemurafenib, Linsitinib, Neratinib, and MK-2461 reduce heme levels in K562 cells, verifying that drug binding leads to a loss of FECH activity. Further biochemical and docking experiments identified the protoporphyrin pocket in FECH as one major drug binding site. Since the genetic loss of FECH activity leads to photosensitivity in humans, our data strongly suggest that FECH inhibition by kinase inhibitors is the molecular mechanism triggering photosensitivity in patients. We therefore suggest that a FECH assay should generally be part of the preclinical molecular toxicology package for the development of kinase inhibitors.
The receptor tyrosine kinase EPHA2 (Ephrin type-A receptor 2) plays important roles in oncogenesis, metastasis, and treatment resistance, yet therapeutic targeting, drug discovery, or investigation ...of EPHA2 biology is hampered by the lack of appropriate inhibitors and structural information. Here, we used chemical proteomics to survey 235 clinical kinase inhibitors for their kinase selectivity and identified 24 drugs with submicromolar affinities for EPHA2. NMR-based conformational dynamics together with nine new cocrystal structures delineated drug–EPHA2 interactions in full detail. The combination of selectivity profiling, structure determination, and kinome wide sequence alignment allowed the development of a classification system in which amino acids in the drug binding site of EPHA2 are categorized into key, scaffold, potency, and selectivity residues. This scheme should be generally applicable in kinase drug discovery, and we anticipate that the provided information will greatly facilitate the development of selective EPHA2 inhibitors in particular and the repurposing of clinical kinase inhibitors in general.
Kinase inhibitors are important cancer therapeutics. Polypharmacology is commonly observed, requiring thorough target deconvolution to understand drug mechanism of action. Using chemical proteomics, ...we analyzed the target spectrum of 243 clinically evaluated kinase drugs. The data revealed previously unknown targets for established drugs, offered a perspective on the "druggable" kinome, highlighted (non)kinase off-targets, and suggested potential therapeutic applications. Integration of phosphoproteomic data refined drug-affected pathways, identified response markers, and strengthened rationale for combination treatments. We exemplify translational value by discovering SIK2 (salt-inducible kinase 2) inhibitors that modulate cytokine production in primary cells, by identifying drugs against the lung cancer survival marker MELK (maternal embryonic leucine zipper kinase), and by repurposing cabozantinib to treat FLT3-ITD-positive acute myeloid leukemia. This resource, available via the ProteomicsDB database, should facilitate basic, clinical, and drug discovery research and aid clinical decision-making.
Solid supported probes have proven to be an efficient tool for chemical proteomics. The kinobeads technology features kinase inhibitors covalently attached to Sepharose for affinity enrichment of ...kinomes from cell or tissue lysates. This technology, combined with quantitative mass spectrometry, is of particular interest for the profiling of kinase inhibitors. It often leads to the identification of new targets for medicinal chemistry campaigns where it allows a two-in-one binding and selectivity assay. The assay can also uncover resistance mechanisms and molecular sources of toxicity. Here we report on the optimization of the kinobead assay resulting in the combination of five chemical probes and four cell lines to cover half the human kinome in a single assay (∼260 kinases). We show the utility and large-scale applicability of the new version of kinobeads by reprofiling the small molecule kinase inhibitors Alvocidib, Crizotinib, Dasatinib, Fasudil, Hydroxyfasudil, Nilotinib, Ibrutinib, Imatinib, and Sunitinib.
A high efficiency sorbent for CO2 capture was developed by loading polyethylenimine （PEI） on mesoporous carbons which possessed well-developed mesoporous structures and large pore volume. The ...physicochemical properties of the sorbent were characterized by N2 adsorption/desorption, scanning electron microscopy （SEM）, thermal gravimetric analysis （TG） and Fourier transform infrared spectroscopy （FT-IR） techniques followed by testing for CO2 capture. Factors that affected the sorption capacity of the sorbent were studied. The sorbent exhibited extraordinary capture capacity with CO2 concentration ranging from 5% to 80%. The optimal PEI loading was determined to be 65 wt.% with a CO2 sorption capacity of 4.82 mmol-CO2/g-sorbent in 15% CO2/N2 at 75℃, owing to low mass-transfer resistance and a high utilization ratio of the amine compound （63%）. Moisture had a promoting effect on the sorption separation of CO2. In addition, the developed sorbent could be regenerated easily at 100℃, and it exhibited excellent regenerability and stability. These results indicate that this PEI-loaded mesoporous carbon sorbent should have a good potential for CO2 capture in the future.
Werner syndrome （WS） is a premature aging disorder that mainly affects tissues derived from mesoderm. We have recently developed a novel human WS model using WRN-deficient human mesenchymal stem ...cells （MSCs）. This model recapitulates many phenotypic features of WS. Based on a screen of a number of chemicals, here we found that Vitamin C exerts most efficient rescue for many features in premature aging as shown in WRN-deficient MSCs, including cell growth arrest, increased reactive oxygen species levels, teiomere attrition, excessive secretion of inflammatory factors, as well as disorganization of nuclear lamina and heterochromatin. Moreover, Vitamin C restores in vivo viability of MSCs in a mouse model. RNA sequencing analysis indicates that Vitamin C alters the expression of a series of genes involved in chromatin condensation, cell cycle regulation, DNA replication, and DNA damage repair pathways in WRN- deficient MSCs. Our results identify Vitamin C as a rejuvenating factor for WS MSCs, which holds the potential of being applied as a novel type of treatment of WS.
Nitrogen-doped mesoporous carbons (NMCs) with controllable nitrogen doping and similar mesoporous structures are prepared by a facile colloidal silica nanocasting method using melamine, phenol, and ...formaldehyde as precursors. Various physicochemical properties, such as the oxidation stability, the conductivity and the electrochemical capacitive performance, the CO2 adsorption, the basicity, and the metal-free catalytic activity of the NMCs, are studied extensively in relation to the incorporation amount of nitrogen in the carbon backbone. The dependence of the oxidation stability and the conductivity of the NMCs on the nitrogen content are similar; both of the biggest improvements are achieved at a low nitrogen content of ca. 4.2 wt %. While used as the supercapacitor electrodes, the NMCs with a mediate nitrogen content of ca. 8 wt % can take full advantage of the nitrogen-induced pseudocapacitance and the nitrogen-enhanced conductivity, delivering an excellent high-rate capacitive performance. The nitrogen content does not play an important role in the CO2 physical adsorption, where the effect of microporosity prevails over the nitrogen-doped carbon surface. However, the nitrogen content determines the basicity of the NMCs, which governs their CO2 chemical adsorption ability and the metal-free catalytic activity for direct oxidation of H2S. The higher the nitrogen content, the higher the basicity and the catalytic activity. Our studies give a reliable relationship between nitrogen doping and the physicochemical properties of mesoporous carbons, which should provide a useful guide to their practical applications.
We demonstrate that it is possible to transform traditional mesoporous carbons into a superior metal-free catalyst for low-temperature H2S removal via doping a high concentration of nitrogen atoms ...into the carbon. The nitrogen doping level is important for the activity of mesoporous carbons as a metal-free catalyst. Although carbons doped with only an intermediate amount of nitrogen (e.g., 4.3 wt %), show little aptitude for the catalytic oxidation of H2S when nitrogen doping reaches a certain high level (e.g., 8.5 wt %), the nitrogen-rich mesoporous carbons (NMC) exhibit high catalytic activity and selectivity toward H2S oxidation at low temperature. Further study suggests that the pyridinic nitrogen atoms are responsible for the catalytic activity in H2S oxidation. Owing to the metal-free nature of the NMC catalyst, it can be easily regenerated by CS2 scrubbing, and the product sulfur can be recovered. Our desulfurization results suggest that such metal-free carbons could, indeed, overcome the limitations of the conventional H2S catalysts and provide suitable, sustainable, and inexpensive solutions for technological development in H2S removal.
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•Compared with single modified nZVI, CMC-nZVI@BC had a higher effectiveness for the removal of Cr(VI).•BC could act as both electron donor and enhance the rate of electrons transfer ...from nZVI to Cr(VI).•CMC-nZVI@BC has good mobility in porous media with a particle size greater than 0.25 mm.•CMC-nZVI@BC can be used for in situ reaction zone for Cr(Ⅵ) contaminated aquifer.
Hexavalent chromium (Cr(VI)) contamination in groundwater poses a significant threat to human and environmental health. In this study, nanoscale zero-valent iron stabilized by carboxymethyl cellulose loaded on biochar (CMC-nZVI@BC) was used as an in-situ reaction zone material to remove Cr(VI) from groundwater. The experimental results demonstrated that CMC-nZVI@BC effectively removed 99.9 % of Cr(VI) within 180 min, which was 22.4 % and 10.7 % higher than that of nZVI@BC and CMC-nZVI, respectively. Physisorption and chemisorption were responsible for Cr(VI) removal. Electrochemical analysis showed that the number of transferred electrons in Cr(Ⅵ) removal by CMC-nZVI@BC was approximately 47 times greater than that of BC, which indicated that BC mainly acted as an electron shuttle to facilitate the electron transfer between nZVI and Cr(VI). The maximum breakthrough C/C0 values of CMC-nZVI@BC in coarse and medium sand were 0.86 and 0.72, respectively, demonstrating its good mobility. The in-situ reaction zone based on CMC-nZVI@BC was suitable for media with particle size greater than 0.25 mm. The reaction zone continuously removed Cr(VI) from the groundwater, and the effective remediation periods in the coarse sand and medium sand were 4 and 6 days, respectively. This study confirms the great potential of CMC-nZVI@BC for contaminated groundwater remediation.
Nitrogen-enriched mesoporous carbons with tunable nitrogen content and similar mesoporous structures have been prepared by a facile colloid silica nanocasting to house sulfur for lithium–sulfur ...batteries. The results give unequivocal proof that nitrogen doping could assist mesoporous carbon to suppress the shuttling phenomenon, possibly via an enhanced surface interaction between the basic nitrogen functionalities and polysulfide species. However, nitrogen doping only within an appropriate level can improve the electronic conductivity of the carbon matrix. Thus, the dependence of total electrochemical performance on the nitrogen content is nonmonotone. At an optimal nitrogen content of 8.1 wt %, the carbon/sulfur composites deliver a highest reversible discharge capacity of 758 mA h g–1 at a 0.2 C rate and 620 mA h g–1 at a 1 C rate after 100 cycles. Furthermore, with the assistance of PPy/PEG hybrid coating, the composites could further increase the reversible capacity to 891 mA h g–1 after 100 cycles. These encouraging results suggest nitrogen doping and surface coating of the carbon hosts are good strategies to improve the performance carbon/sulfur-based cathodes for lithium–sulfur batteries.
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