Biosynthesis of Epipyrone A Reveals a Highly Specific Membrane-Bound Fungal C-Glycosyltransferase for Pyrone Galactosylation.

Epipyrone A is a unique C-galactosylated 4-hydroxy-2-pyrone derivative with an antifungal potential from the fungus Epicoccum nigrum. We elucidated its biosynthesis via heterologous expression and characterized an unprecedented membrane-bound pyrone C-glycosyltransferase biochemically. Molecular docking and mutagenesis experiments suggested a possible mechanism for the heterocyclic C-glycosylation and the importance of a transmembrane helix for its catalysis. These results expand the repertoire of C-glycosyltransferases and provide new insights into the formation of C-glycosides in fungi.

Adult localized Langerhans cell histiocytosis: A case report.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a rare clonal proliferative disease of Langerhans cells with unknown pathogenesis. An increasing number of clinicians recognize that LCH has a wide clinical spectrum and a highly varied course. Adults rarely develop LCH. Here, we report a case of adult localized LCH. CASE SUMMARY: A 32-year-old woman presented with plaques and ulcers on the vulva and crissum, accompanied by pain that persisted for more than one year. Physical examination revealed a red-infiltrating plaque with ulcerations and exudates in the vulva and crissum. Pathological examination revealed a diffuse infiltration of lymphocytes, eosinophilic granulocytes, and histiocytoid cells in the superficial dermis. Proliferative histiocytoid cells showed mild atypia, partly with kidney-shaped nuclei. Immunohistochemical examination showed that the histiocytoid cells were positive for S100 protein and CD1 and weakly positive for CD68 (20% +), with a Ki-67 index of 30%. Laboratory tests did not reveal any other systemic damage. The patient was diagnosed with adult localized LCH and was prescribed oral prednisone (20 mg) once daily. The skin lesions gradually improved and are still being followed-up. CONCLUSION: Adult localized LCH is rare and must be differentiated from other common conditions.

Photoaffinity labelling-based chemoproteomic strategy identifies PEBP1 as the target of ethyl gallate against macrophage activation.

Ulcerative colitis (UC) is an inflammatory disease of the colon with an unmet need for therapeutic targets. Ethyl gallate (EG) is a natural small molecule for UC treatment, but its cellular target is unknown. By labelling EG with a diazirine photocrosslinker and a click chemistry handle, we identified phosphatidyl-ethanolamine binding protein1 (PEBP1) as a direct cellular target of EG by forming hydrogen bonds with Asp70 and Tyr120. In particular, hydrogen/deuterium exchange mass spectrometry indicated that EG induced the sequence (residues 141-153) embedding to inhibit S153 phosphorylation of PEBP1. Additionally, the EG-mediated sequence (residues 108-122) exposure significantly enhanced PEBP1-Raf-1 interaction to block the downstream NF-κB inflammatory pathway in macrophages. Moreover, PEBP1 siRNA substantially reversed the EG-dependent down-regulation of the phosphorylation of IKKß, IκBα and NF-κB, demonstrating that the NF-κB signal functioned as an essential anti-inflammation mechanism of PEBP1. Collectively, we revealed PEBP1 as a previously undescribed cellular target in macrophages for UC therapy and identified a new allosteric site for PEBP1 biology study using EG as a chemical probe.

Neuroinflammation inhibition by small-molecule targeting USP7 noncatalytic domain for neurodegenerative disease therapy.

Neuroinflammation is a fundamental contributor to progressive neuronal damage, which arouses a heightened interest in neurodegenerative disease therapy. Ubiquitin-specific protease 7 (USP7) has a crucial role in regulating protein stability in multiple biological processes; however, the potential role of USP7 in neurodegenerative progression is poorly understood. Here, we discover the natural small molecule eupalinolide B (EB), which targets USP7 to inhibit microglia activation. Cocrystal structure reveals a previously undisclosed covalent allosteric site, Cys576, in a unique noncatalytic HUBL domain. By selectively modifying Cys576, EB allosterically inhibits USP7 to cause a ubiquitination-dependent degradation of Keap1. Keap1 function loss further results in an Nrf2-dependent transcription activation of anti-neuroinflammation genes in microglia. In vivo, pharmacological USP7 inhibition attenuates microglia activation and resultant neuron injury, thereby notably improving behavioral deficits in dementia and Parkinson's disease mouse models. Collectively, our findings provide an attractive future direction for neurodegenerative disease therapy by inhibiting microglia-mediated neuroinflammation by targeting USP7.

Deoxyhypusine hydroxylase as a novel pharmacological target for ischemic stroke via inducing a unique post-translational hypusination modification.

Ischemic stroke remains one of the leading causes of death worldwide, thereby highlighting the urgent necessary to identify new therapeutic targets. Deoxyhypusine hydroxylase (DOHH) is a fundamental enzyme catalyzing a unique posttranslational hypusination modification of eukaryotic translation initiation factor 5A (eIF5A) and is highly involved in the progression of several human diseases, including HIV-1 infection, cancer, malaria, and diabetes. However, the potential therapeutic role of pharmacological regulation of DOHH in ischemic stroke is still poorly understood. Our study first discovered a natural small-molecule brazilin (BZ) with an obvious neuroprotective effect against oxygen-glucose deprivation/reperfusion insult. Then, DOHH was identified as a crucial cellular target of BZ using HuProt™ human proteome microarray. By selectively binding to the Cys232 residue, BZ induced a previously undisclosed allosteric effect to significantly increase DOHH catalytic activity. Furthermore, BZ-mediated DOHH activation amplified mitophagy for mitochondrial function and morphology maintenance via DOHH/eIF5A hypusination signaling pathway, thereby protecting against ischemic neuronal injury in vitro and in vivo. Collectively, our study first identified DOHH as a previously unreported therapeutic target for ischemic stroke, and provided a future drug design direction for DOHH allosteric activators using BZ as a novel molecular template.

Functional Characterization and Protein Engineering of a Triterpene 3-/6-/2'-O-Glycosyltransferase Reveal a Conserved Residue Critical for the Regiospecificity.

Engineering the function of triterpene glucosyltransferases (GTs) is challenging due to the large size of the sugar acceptors. In this work, we identified a multifunctional glycosyltransferase AmGT8 catalyzing triterpene 3-/6-/2'-O-glycosylation from the medicinal plant Astragalus membranaceus. To engineer its regiospecificity, a small mutant library was built based on semi-rational design. Variants A394F, A394D, and T131V were found to catalyze specific 6-O, 3-O, and 2'-O glycosylation, respectively. The origin of regioselectivity of AmGT8 and its A394F variant was studied by molecular dynamics and hydrogen deuterium exchange mass spectrometry. Residue 394 is highly conserved as A/G and is critical for the regiospecificity of the C- and O-GTs TcCGT1 and GuGT10/14. Finally, astragalosides III and IV were synthesized by mutants A394F, T131V and P192E. This work reports biocatalysts for saponin synthesis and gives new insights into protein engineering of regioselectivity in plant GTs.

Perfluorooctane sulfonate induced toxicity in embryonic stem cell-derived cardiomyocytes via inhibiting autophagy-lysosome pathway.

Perfluorooctane sulfonate (PFOS), a classic environmental pollutant, is reported to cause cardiotoxicity in animals and humans. It has been demonstrated that PFOS exposure down-regulates expression of cardiac-development related genes and proteins. However, the related mechanism of PFOS has not been fully elucidated. In the present study, the embryonic stem (ES) cells-derived cardiomyocytes (ESC-CMs) was employed to investigate PFOS-mediated mechanism in developmental toxicity of cardiomyocytes. Our previous study shows that PFOS induces cardiomyocyte toxicity via causing mitochondrial damage. Nevertheless, the underlying mechanism by which PFOS affects the autophagy-related mitochondrial toxicity in ESC-CMs remains unclear. Here, we found that PFOS induced the swelling of mitochondria and the autophagosome accumulation in ESC-CMs at 40 µM concentration. PFOS increased the levels of LC3-II, p62, and ubiquitinated proteins. PFOS also induced an increase of LC3 and p62 localization into mitochondria, indicating that mitophagy degradation was impaired. The results of autophagic flux using chloroquine and RFP-GFP-LC3 analysis showed that the accumulation of autophagosome was not caused by the formation but by the impaired degradation. PFOS was capable of blocking the fusion between autophagosome and lysosome. PFOS caused dysfunction of lysosomes because it down-regulated Lamp2a and cathepsin D, but it did not induced lysosome membrane permeabilization. Meanwhile, PFOS-mediated lysosomal function and the inhibitory effect of autophagic flux could be reversed by PP242 at 40 nM concentration, an mTOR inhibitor. Furthermore, PP242 restored PFOS-induced ATP depletion and mitochondrial membrane potential. In conclusion, PFOS induced mitochondrial dysfunction via blocking autophagy-lysosome degradation, leading to cardiomyocyte toxicity from ES cells.

Functional Characterization and Structural Basis of an Efficient Di-C-glycosyltransferase from Glycyrrhiza glabra.

A highly efficient di-C-glycosyltransferase GgCGT was discovered from the medicinal plant Glycyrrhiza glabra. GgCGT catalyzes a two-step di-C-glycosylation of flopropione-containing substrates with conversion rates of >98%. To elucidate the catalytic mechanisms of GgCGT, we solved its crystal structures in complex with UDP-Glc, UDP-Gal, UDP/phloretin, and UDP/nothofagin, respectively. Structural analysis revealed that the sugar donor selectivity was controlled by the hydrogen-bond interactions of sugar hydroxyl groups with D390 and other key residues. The di-C-glycosylation capability of GgCGT was attributed to a spacious substrate-binding tunnel, and the G389K mutation could switch di- to mono-C-glycosylation. GgCGT is the first di-C-glycosyltransferase with a crystal structure, and the first C-glycosyltransferase with a complex structure containing a sugar acceptor. This work could benefit the development of efficient biocatalysts to synthesize C-glycosides with medicinal potential.

Allosteric regulation of protein 14-3-3ζ scaffold by small-molecule editing modulates histone H3 post-translational modifications.

Background: Histone post-translational modifications (PTMs) are involved in various biological processes such as transcriptional activation, chromosome packaging, and DNA repair. Previous studies mainly focused on PTMs by directly targeting histone-modifying enzymes such as HDACs and HATs. Methods and Results: In this study, we discovered a previously unexplored regulation mechanism for histone PTMs by targeting transcription regulation factor 14-3-3ζ. Mechanistic studies revealed 14-3-3ζ dimerization as a key prerequisite, which could be dynamically induced via an allosteric effect. The selective inhibition of 14-3-3ζ dimer interaction with histone H3 modulated histone H3 PTMs by exposing specific modification sites including acetylation, trimethylation, and phosphorylation, and reprogrammed gene transcription profiles for autophagy-lysosome function and endoplasmic reticulum stress. Conclusion: Our findings demonstrate the feasibility of editing histone PTM patterns by targeting transcription regulation factor 14-3-3ζ, and provide a distinctive PTM editing strategy which differs from current histone modification approaches.

Diversity of O-Glycosyltransferases Contributes to the Biosynthesis of Flavonoid and Triterpenoid Glycosides in Glycyrrhiza uralensis.

Licorice (Glycyrrhiza uralensis) is a popular medicinal plant containing more than 70 flavonoid and triterpenoid glycosides. Thus far, only a few reports are available on the glycosylation enzymes involved in their biosynthesis. In this work, we mined the transcriptome data of G. uralensis and discovered 43 candidate genes for O-glycosyltransferase (O-GT). Among them, 17 genes could be expressed in E. coli, and functions of the enzymes were analyzed by catalyzing eight native substrates. As a result, we characterized 11 O-GTs, including isoflavone 7-O-GTs, flavonol 3-O-GTs, and promiscuous O-GTs catalyzing flavones, chalcones, and triterpenoids. They could efficiently synthesize key licorice compounds such as liquiritin, isoliquiritin, ononin, and 3-O-ß-d-glucuronosyl glycyrrhetinic acid. The diversity of O-GTs contributes to the biosynthesis of various glycosides in licorice. These enzymes could also be used as biocatalytic tools to synthesize other bioactive O-glycosides.

The opposite roles of PAS-5 and Galectin-1 in immune response during the early infection of Angiostrongylus cantonensis.

BACKGROUND: Angiostrongylus cantonensis is a human zoonotic nematode parasite. Our previous studies found that PAS-5 and Galectin-1 (Gal-1) proteins of A. cantonensis could be strongly recognized by sera from mice infected with A. cantonensis. In this study, we further evaluated the potential roles of these two proteins in the induction of immune response in mice. METHODS: Mice were immunized with recombinant PAS-5 or Gal-1 and then challenged with 30 infective A. cantonensis larvae following the last immunization. We then examined the infected mice for changes in serum antibodies and cytokines by ELISA, CD4+ T cells and CD4+CD25+FoxP3+ regulatory T cells (Tregs) by flow cytometry, and tissue damage severity by hematoxylin-eosin (H&E) staining. RESULTS: Compared with control mice, the PAS-5-immunized mice exhibited increased levels of serum antibodies and cytokines (except for IL-10) at different time points post-infection. PAS-5 immunization promoted significant proliferation of CD4+ T cells, and caused more damage in the brain tissue. Vaccination with Gal-1 inhibited the production of antibodies (except for IgG1) and IFN-γ, but promoted the expression of IL-4 and IL-10. Gal-1 immunization results in significant increases in the levels of CD4+CD25+FoxP3+ Tregs, and mild inflammatory changes. CONCLUSIONS: Taken together, our findings show that PAS-5 enhances, but Gal-1 inhibits the immune response in the early stage of A. cantonensis infections.

Effects of safflower yellow on beta-amyloid deposition and activation of astrocytes in the brain of APP/PS1 transgenic mice.

Safflower yellow (SY), one of traditional Chinese medicine extracted from safflower, has been shown to have neuroprotective effects on animal models of vascular dementia and Alzheimer's diseases (AD), by inhibiting oxidative injury, neuronal apoptosis and tau hyperphosphorylation. In this study, we investigated whether safflower yellow (SY) can improve cognitive function, decrease Amyloid ß (Aß) accumulation and overactivation of astrocytes in AD mouse model. We found that SY treatment significantly ameliorated the learning and memory deficits of APP/PS1 mice. By hematoxylin-eosin staining, we found that the neuronal loss and death in APP/PS1 mice was decreased by SY treatment. Immunohistochemical staining showed that SY treatment dramatically down-regulated Aß1-42 deposition and glial fibrillary acidic protein (GFAP) level in APP/PS1 mice. Biochemical analysis also showed that SY treatment reduced soluble and insoluble Aß1-42 level in the cortex and soluble Aß1-42 level in the hippocampus of APP/PS1 mice. Moreover, we found that SY treatment decreased the expression of proteins related to generation of Aß, and markedly increased expression of enzymes associated with clearance of Aß in the brain of APP/PS1 mice. These results indicate that the SY can serve as a promising therapeutic approach for the treatment of AD.

[Cloning of galectin-1 gene of Angiostrongylus cantonensis and testing the agglutination property of the galectin-1 protein].

Objective: To clone and express the galectin-1 gene of Angiostrongylus cantonensis, and test the agglutination property of its protein. Methods: The three-dimensional structure of galectin-1 was analyzed with Swiss Model. Total RNA was extracted from male worms of A. cantonensis. Primers were designed for galectin-1 based on its coding region (GenBank Accession No. JN133961.1). RT-PCR was performed, and the PCR products were subcloned to pCold Ⅲ plasmid and transduced into Escherichia coli BL21 strain. The recombinant plasmid was extracted from positive clones on LB plate containing 100 µg/ml Kanamycin, and validated with double digestion, PCR identification and sequencing. The confirmed positive clones of E. coli BL21 with the recombinant plasmid were grown in LB medium containing ampicillin (100 µg/ml, 100 µl). IPTG was added to induce expression of the plasmid. The galectin-1 recombinant protein was purified with Ni-NTA beads, and analyzed with SDS-PAGE and Western blotting using anti-serum of mouse immunized with whole worms of A. cantonensis. The agglutination reaction with red blood cells in fresh blood of ICR mouse was observed for the 10-fold serial dilutions of recombinant proteins (5.55 × 10(-1)-5.55 × 10(-5) ng/µl). Results: The Swiss Model analysis showed that the functional galectin-1 had a non-dimeric form. As was expected, the RT-PCR products had a size of 850 bp. Results of double digestion, PCR and sequencing showed successful construction of the pCold Ⅲ-galectin-1 plasmid. SDS-PAGE revealed expression of soluble recombinant fusion protein with molecular weight of ~36 000. Western blotting showed that the galectin-1 protein was recognized by mouse anti-serum. In addition, the minimun concentration of galectin-1 that showed significant agglutination reactions with mouse red blood cells was 5.55 × 10(-4) ng/µl. Conclusion: The galectin-1 clone can be expressed in the pCold Ⅲ plasmid, and its protein product has agglutination property.

Safflower yellow ameliorates cognition deficits and reduces tau phosphorylation in APP/PS1 transgenic mice.

Alzheimer's disease (AD), the most common cause of dementia worldwide, is mainly characterized by the aggregated ß-amyloid (Aß) and hyperphosphorylated tau. Safflower yellow (SY) is a novel water extract of natural safflower and has been suggested to ameliorate memory deficits in several animal models of dementia. In this study, we aimed to investigate the effect and mechanism of SY on deficits of learning and memory and hyperphosphorylation of tau in APP/PS1 double transgenic mice. APP/PS1 mice were administered with SY (10, 30, 100 mg/kg) by oral gavage for three months at the age of six months. The ability of learning and memory was investigated using the step-down test and Morris water maze test, and protein level in the brain was evaluated using western blot. Here, we found that SY treatment can improve spatial learning and memory ability, and reduce tau hyperphosphorylation at Ser199, Thr205, Ser396, Ser404 sites in APP/PS1 mice. In addition, the activity the of cyclin-dependent kinase 5 (CDK-5) and glycogen synthase kinase 3ß (GSK-3ß), major kinases involved in tau phosphorylation, was siginificantly decreased in APP/PS1 mice by SY treatment. These results support SY can serve as a promising multitarget neuronal therapeutic agent for the treatment of AD.

[Optimization of ultrasonic extraction process for Xiaoqinglong granules by Box-Behnken in condition of medium scale].

This paper is to investigate the optimization conditions of ultrasonic technique for extraction process of Xiaoqinglong granules in medium scale. First of all, single factor experiment was used to determine the overall impact tendency and range of each factor； secondly, Box-Behnken method was used for optimization and detecting the content of paeoniflorin, ephedrine hydrochloride, glycyrrhizic acid of the liquid medicine. Their respective extraction rate was calculated and the comprehensive evaluation was carried out. The results were used as the evaluation basis for the efficacy of Xiaoqinglong granules ultrasonic extraction. The test results showed that the optimum extraction process of Xiaoqinglong granules by ultrasonic extraction was under the following conditions: ultrasonic power 600 W, liquid-solid ratio 10∶1, extraction for 31 min. Under this condition, the predicted value of extraction rate for Xiaoqinglong granules was 85.90%, and the test value was 85.87%. The mathematical model(P<0.01) established in this paper was significant, and can be used for the analysis and prediction of the ultrasonic extraction process of Xiaoqinglong granules.

Safflower yellow reduces lipid peroxidation, neuropathology, tau phosphorylation and ameliorates amyloid ß-induced impairment of learning and memory in rats.

Insoluble plaques of amyloid ß proteins (Aß) and neurofibrillary tangles of hyperphosphorylated tau are key markers for Alzheimer's disease (AD). Safflower yellow (SY) is one of traditional Chinese medicine extracted from safflower, which is suggested to have therapeutic potential for neurodegenerative disorders. However, whether SY can ameliorate impairment of learning and memory in AD model, and its causal mechanism are still unclear. Here, we applied different doses of SY intragastrically to Wistar rats injected with amyloid ß (1-42) for 1 month. By the Morris water maze test, we found that treatment of SY significantly attenuated amyloid ß (1-42)-induced impairment of memory in rats. Mechanistically, SY treatment increased the level of superoxidedismutase (SOD) and Glutathione peroxidase (GSH-Px), and decreased the level of malondialdehyde (MDA) and acetylcholinesterase (T-CHE) in brain tissues of AD rats. Pathological analysis also showed that SY treatment inhibited the morphological alteration of neurons and tau hyperphosphorylation induced by amyloid ß (1-42)-injection in the cortex and hippocampus. Moreover, SY treatment inhibited CDK-5 and GSK-3 signaling pathways, which are upregulated in AD rats. Our data indicate that safflower yellow can serve as a therapeutic candidate for Alzheimer's disease.