Celastrol induces ferroptosis in activated HSCs to ameliorate hepatic fibrosis via targeting peroxiredoxins and HO-1

Ferroptosis is a form of regulated cell death, characterized by excessive membrane lipid peroxidation in an iron- and ROS-dependent manner. Celastrol, a natural bioactive triterpenoid extracted from Tripterygium wilfordii, shows effective anti-fibrotic and anti-inflammatory activities in multiple hepatic diseases. However, the exact molecular mechanisms of action and the direct protein targets of celastrol in the treatment of liver fibrosis remain largely elusive. Here, we discover that celastrol exerts anti-fibrotic effects via promoting the production of reactive oxygen species (ROS) and inducing ferroptosis in activated hepatic stellate cells (HSCs). By using activity-based protein profiling (ABPP) in combination with bio-orthogonal click chemistry reaction and cellular thermal shift assay (CETSA), we show that celastrol directly binds to peroxiredoxins (PRDXs), including PRDX1, PRDX2, PRDX4 and PRDX6, through the active cysteine sites, and inhibits their anti-oxidant activities. Celastrol also targets to heme oxygenase 1 (HO-1) and upregulates its expression in activated-HSCs. Knockdown of PRDX1, PRDX2, PRDX4, PRDX6 or HO-1 in HSCs, to varying extent, elevated cellular ROS levels and induced ferroptosis. Taken together, our findings reveal the direct protein targets and molecular mechanisms via which celastrol ameliorates hepatic fibrosis, thus supporting the further development of celastrol as a promising therapeutic agent for liver fibrosis.

A targeted covalent inhibitor of p97 with proteome-wide selectivity

A resurging interest in targeted covalent inhibitors (TCIs) focus on compounds capable of irreversibly reacting with nucleophilic amino acids in a druggable target. p97 is an emerging protein target for cancer therapy, viral infections and neurodegenerative diseases. Extensive efforts were devoted to the development of p97 inhibitors. The most promising inhibitor of p97 was in phase 1 clinical trials, but failed due to the off-target-induced toxicity, suggesting the selective inhibitors of p97 are highly needed. We report herein a new type of TCIs (i.e., FL-18) that showed proteome-wide selectivity towards p97. Equipped with a Michael acceptor and a basic imidazole, FL-18 showed potent inhibition towards U87MG tumor cells, and in proteome-wide profiling, selectively modified endogenous p97 as confirmed by in situ fluorescence scanning, label-free quantitative proteomics and functional validations. FL-18 selectively modified cysteine residues located within the D2 ATP site of p97. This covalent labeling of cysteine residue in p97 was verified by LC‒MS/MS-based site-mapping and site-directed mutagenesis. Further structure-activity relationship (SAR) studies with FL-18 analogs were established. Collectively, FL-18 is the first known small-molecule TCI capable of covalent engagement of p97 with proteome-wide selectivity, thus providing a promising scaffold for cancer therapy.

Identification of a novel PHGDH covalent inhibitor by chemical proteomics and phenotypic profiling

The first rate-limiting enzyme of the serine synthesis pathway (SSP), phosphoglycerate dehydrogenase (PHGDH), is hyperactive in multiple tumors, which leads to the activation of SSP and promotes tumorigenesis. However, only a few inhibitors of PHGDH have been discovered to date, especially the covalent inhibitors of PHGDH. Here, we identified withangulatin A (WA), a natural small molecule, as a novel covalent inhibitor of PHGDH. Affinity-based protein profiling identified that WA could directly bind to PHGDH and inactivate the enzyme activity of PHGDH. Biolayer interferometry and LC-MS/MS analysis further demonstrated the selective covalent binding of WA to the cysteine 295 residue (Cys295) of PHGDH. With the covalent modification of Cys295, WA blocked the substrate-binding domain (SBD) of PHGDH and exerted an allosteric effect to induce PHGDH inactivation. Further studies revealed that with the inhibition of PHGDH mediated by WA, the glutathione synthesis was decreased and intracellular levels of reactive oxygen species (ROS) were elevated, leading to the inhibition of tumor proliferation. This study indicates WA as a novel PHGDH covalent inhibitor, which identifies Cys295 as a novel allosteric regulatory site of PHGDH and holds great potential in developing anti-tumor agents for targeting PHGDH.

Discovery of a subtype-selective, covalent inhibitor against palmitoylation pocket of TEAD3

The TEA domain (TEAD) family proteins (TEAD1‒4) are essential transcription factors that control cell differentiation and organ size in the Hippo pathway. Although the sequences and structures of TEAD family proteins are highly conserved, each TEAD isoform has unique physiological and pathological functions. Therefore, the development and discovery of subtype selective inhibitors for TEAD protein will provide important chemical probes for the TEAD-related function studies in development and diseases. Here, we identified a novel TEAD1/3 covalent inhibitor (DC-TEADin1072) with biochemical IC

Protein targets of medicinally active molecules based on their original structures and molecular probes / 药学学报

Medicinally active molecules are those that have pharmacological effects. Research on protein targets of these molecules not only clarifies their mechanism of action, but also deepens our understanding of biological systems. Here we review recent advances in protein targets of drugs used in clinical practice or in preclinical research. They have various functions including anti-inflammatory, anti-malarial, anti-tumor and other biological activities. Activity-based protein profiling (ABPP) and cellular thermal shift assay (CETSA) are two useful methods to identify the protein targets of small molecules. ABPP depends on a derivative active molecule probe to pull down the protein targets to reveal the interaction mechanisms between the active molecules and targets. Drug target engagement also can be assessed by means of CETSA based on ligand-induced changes in protein thermal stability. In the CETSA approach, the active molecules do not need to be chemically modified. Combining the CETSA method with quantitative mass spectrometry is an effective approach to study the effect of compounds on the thermal profile of a cellular proteome and identify the protein targets. ABPP and CETSA can be complementary and effectively clarify the protein targets. The study of protein targets will help reveal the mechanism of action of medicinal molecules, reveal toxic mechanisms and aid in the discovery of new medicinal targets to promote the process of drug development.

Progress of methodology for identifying target protein of natural active small molecules / 中国中药杂志

Drug targets are special molecules that can interact with drugs and exert pharmacological functions in human body. The natural active small molecules are the bioactive basis of traditional Chinese medicine, and the mechanism study is a hot topic now, especially for the identification of their target proteins. However, little progress has been made in this field until now. Here, we summarized the recent technologies and methods for the identification of target proteins of natural bioactive small molecules, and introduced the main research methods, principles and successful cases in this field. We also explored the applicability and discussed the advantages and disadvantages among different methods. We hope this review can be used as a reference for the researchers who engaged in natural pharmaceutical chemistry, pharmacology and chemical biology.

Diagnostic value of serum proteome characters analyzed by proteomic fingerprint technology in patients with inflammatory bowel disease / 中华消化杂志

Objective To explore the diagnostic model and clinical application value of serum proteomic fingerprint in inflammatory bowel disease (IBD) .Methods Serum proteome profiles of 72 IBD patients (54 Crohn′s disease (CD) and 18 ulcerative colitis (UC) and 44 healthy controls were analyzed by the weak cation exchange (WCX) beads combined matrix‐assisted laser desorption/ionization time of flight mass spectrometry (MALDI‐TOF‐MS ) technique . Among three groups , every two groups were compared .Wilcoxon rank sum test was used to screen out the peaks of difference expressed protein (P<0 .05) .Genetic algorithm combining with support vector machine (SVM ) was utilized to select the best diagnostic model .The predictive effects of this model was evaluated by leave one out method (LOO ) . Results The 10 most discriminating protein peaks were screened out between CD group and healthy control group , between UC group and healthy control group , between CD group and UC group . A diagnostic model established with four protein peaks ,the mass‐to‐charge ratio (M /Z ) of them was 3 275 .29 ,4 963 .91 ,4 980 .53 and 5 336 .90 ,could better distinguish CD and healthy controls .The specificity was 97 .7% ,and the sensitivity was 92 .6% in CD diagnosis .A diagnostic model established with four protein peaks ,the M /Z of them was 2 272 .41 ,2 660 .42 ,3 029 .77 and 5 002 .78 ,could better distinguish UC and healthy controls .The specificity was 100 .0% ,and the sensitivity was 94 .4% .A specificity was 50 .0% and sensitivity was 88 .9% in CD diagnosis with the diagnostic model of six protein peaks and the M /Z of them was 2 082 .63 ,2 210 .64 ,4 039 .02 ,4 298 .30 ,4 978 .03 ,5 002 .22 .Conclusion The diagnostic model of serum difference expressed protein in CD and UC is established by MALDI‐TOF‐MS technique and genetic algorithm combining with SVM ,which has high diagnostic value in IBD .

Characterization of differentially expressed stress-associated proteins in starch granule development under heat stress in wheat (Triticum aestivum L.).

Abiotic stress causes abrupt increase in the expression of stress-associated proteins, which provide tolerance by modulating the defense mechanism of plants. Small heat shock proteins (sHSPs) and anti-oxidant enzymes are important for environmental stress tolerance of the plants. In this study, two full-length cDNAs encoding small heat shock protein (sHSP) and superoxide dismutase (SOD), designated as TasHSP and SODI were identified and characterized from C-306 (thermotolerant) and PBW343 (thermosusceptible) cultivars of wheat (Triticum aestivum L.). An alpha crystalline domain was observed in TasHSP and manganese/iron binding domain in case of SODI. Quantitative real-time PCR showed very high transcript level of TasHSP and SOD in C-306 compared to PBW343 at different stages of growth and against differential heat stress (HS). Under differential HS at milky-dough stage, the fold change in transcript of both TasHSP and SOD was observed maximum in C-306, compared to PBW343. Protein profiling and isoenzymes analysis showed the expression of several heat-stable proteins and prominent isoenzymes of SOD in C-306, compared to PBW343. Scanning electron microscopy (SEM) of starch granules showed globular, well-shaped and more numbers of endospermic cells in C-306, compared to defragmented, irregular shaped and shrunken granules in case of PBW343 under HS treatment (42°C for 2 h). Diurnal change in soluble starch synthase (SSS) activity showed an increase in the activity during afternoon (35°C), compared to morning (29°C) and evening (32°C) in both the cultivars. Under heat stress (42°C for 2 h), a drastic decrease in the SSS activity was observed, due to the thermal denaturation of the enzyme. Thermotolerance capacity analyzed using cell membrane stability (CMS) showed significantly higher CMS in case of C-306, compared to PBW343 at different stages of growth. Findings suggest that abundance of TasHSP and SODI during milky-dough stage plays a very important role in starch granule biosynthesis. The mechanism may be further exploited to develop tolerant wheat cultivar with high quality seeds.

The Cross-talk Between p27~(kip1) and Its Interacting Molecules in Breast Cancer Cells / 生物化学与生物物理进展

p27kip1 is an important negatively regulator of cell cycle progression and plays a central role in the pathogenesis of a member of tumors including breast cancer. In breast cancer cells, the level of p27kip1 expression usually decreases during tumor development and progression, in addition, cytoplasm mislocalization of p27kip1 has been reported, but less is known about the exact molecular mechanisms. Studies have indicated that phosphorylation is the key regulation way, several signal transduction pathways are involved in the regulation of the expression and distribution of p27kip1. To further understand the mechanism, the disparity of the interacting protein profiling between tumor cells and normal cells must be identified first. Including cyclins, cyclin-depend kinases, CRM1, jab1, SKP2, p27kip1 has various interacting molecules. There are also several interacting molecules especially for breast cancer cells. It seems that different protein profiling cause the different expression and intracellular distribution in different cell cycle phase. So, disparity of the p27kip1 protein profiling may be the main mechanism of its down-expression and mislocalization in breast cancer cells.