Screening novel inhibitors of squalene epoxidase and their effects on hepatocellular carcinoma / 药学学报

Squalene epoxidase (SQLE) is a potential target for the treatment of liver cancer. Bioinformatics analysis indicated that the high expression of SQLE was closely related to the clinical stage and poor prognosis of patients with liver cancer. However, the existing inhibitors against SQLE 195 tyrosine residue (Y195) cannot be used clinically due to severe side effects. In this study, 35 small-molecule compounds targeting SQLE 335 tyrosine residue (Y335) were selected by computer virtual screening. Combined with MTT assay, 3 candidate compounds (19#, 31# and 35#) with significant inhibitory effects on the proliferation of Huh7 cell line were obtained. Further studies showed that these 3 compounds could inhibit the migration of Huh7 cells, reduce the contents of total and free cholesterol, up-regulate the expression of tumor suppressor gene PTEN, and down-regulate the expression of PI3K and AKT proteins. The results showed that the novel inhibitors 19#, 31# and 35# targeting SQLE Y335 could reduce cholesterol content, inhibit the proliferation and migration of Huh7, thus playing an anti-liver cancer role.

Cloning and Expression Analysis of Squalene Epoxidase Gene in Poria cocos / 中国实验方剂学杂志

ObjectiveTo clone squalene epoxidase （SE）， a potential key rate-limiting enzyme involved in the synthesis pathway of Poria cocos triterpenes， from P. cocos and analyze for bioinformatics and expression. MethodThe total RNA was extracted by the kit and reverse-transcribed to cDNA. Specific primers were designed， and the cDNA was used as a template for cloning the SE gene， which was analyzed for bioinformatics. The expression of P. cocos qualene epoxidase（PcSE） was examined by Real-time polymerase chain reaction（Real-time PCR） in P. coco Shenzhou No. 10， Xiangjing 28， and 5.78 strains. ResultThe full length of PcSE is 1 571 bp， containing four exons and three introns. The obtained CDS sequence is 1 413 bp， encoding 470 amino acids. This protein is a hydrophobic protein with no signal peptide structure and has two transmembrane structural domains with a FAD/NAD （P） binding domain and SE structural domain localized to the mitochondrial membrane and the plasma membrane. The homologous sequence alignment with fungi of the Poriferae family is 80.92%， and the phylogenetic tree shows that PcSE protein is most closely related to P. cocos from the US. The results of Real-time PCR showed that the PcSE was expressed in all three strains， with the highest expression in 5.78 strain， and there was no significant difference in PcSE expression among the three strains. ConclusionFor the first time， the PcSE gene was cloned and analyzed from P. cocos， providing a basis for further research on the function of PcSE and the analysis of P. cocos triterpene biosynthesis pathway.

Cytoprotective Effect of Dietary Squalene Supplementation on Experimentally Induced Cardiomyopathy in Rats

Background: Adriamycin is a broadspectrum, potent, older chemotherapy drug and antineoplastic agent used in the treatment of several cancers such as solid tumours, leukaemias, and lymphomas, playing a major role in cancer chemotherapy. Long-term use of this drug results in congestive heart failure and to overcome this effect dietary squalene intake reduces the adverse effects of adriamycin-mediated cardiotoxicity and cellular oxidative stress. Methods: The current study aims to investigate the cytoprotective effects of dietary squalene supplementation on adriamycin-induced cardiomyopathy in rats in terms of alterations in Troponin T, homocysteine, diagnostic marker enzymes, and cardiac tissue histology. Results: The findings show that a 1.5 percent dose of dietary squalene supplementation for 21 days reduced adriamycin-induced changes in homocysteine, troponin T, diagnostic marker enzymes, and lesions in cardiac tissues. Conclusion: The outcomes of the study specified squalene's cytoprotective action which stabilizes membranes against adriamycin-induced oxidative membrane degradation, which is primarily responsible for heart cell irreversible necrosis.

Impact of mannitol and poly ethylene glycol 6000 induced water deficit on plant biomass and major secondary metabolites in Centella asiatica (L.) Urb. in vitr

Low water potential related stresses are regulated by modifying water uptake and loss to avoid low water potential, accumulating solutes which in turn enhance active principles and its gene expressions. Present study examined effect of in vitro induced absorption of mannitol and PEG (poly ethelene glycol) 6000 in Indian pennywort, Centella asiatica (L.) Urb., neutraceutical plant, evidenced by phenotypic, molecular and phytochemical analyses. Both mannitol and PEG 6000 induce water deficit conditions in plants and retarded normal plant biomass in terms of fresh and dry weights. These effects were significantly less severe in plants subjected to mannitol, compared to PEG. PEG and mannitol imposed water deficit, resulted in decline in major active compound, asiaticoside evidenced by HPTLC of asiaticoside content. Differential expression of some selected key genes in the asiaticoside pathway including squalene synthase and ? amyrin synthase by qPCR, confirmed decrease in transcript level expression of asiaticoside, whereas upregulated transcript level expression was observed in cycloartenol synthase for synthesis of phytosterols. Estimation of total flavonoids and phenolics under different water deficit conditions were found declined. In conclusion, water deficit by mannitol and PEG 6000 can significantly affects processes associated with biomass growth and ability to synthesize secondary metabolites in C. Asiatica.

The development of folate modified squalene-chidamide prodrug self-assembled nanoparticles to enhance the drug delivery in pancreatic cancer microenvironment / 药学学报

This research aimed at the key issue that chemical drugs and Chinese medicine hydrophilic small molecule anti-tumor drugs were difficult to break through the dense interstitial permeability barrier of pancreatic cancer to achieve the key problem of drug efficacy in the deep part of tumor tissue. To solve this problem, the lipophilic molecule squalene (SQ) and the hydrophilic anti-tumor drug chidamide (CHI) were linked by a trypsin responsive bond to form a prodrug (SQ-CHI) and a folic acid modified prodrug self-assembled nanoparticles (FA-SQ-CHI NPs) were further developed. The feature of prodrug molecules and nanoparticles were characterized. The in vitro release characteristics and cytotoxicity of blank vector were investigated. The efficacy and permeability of the prodrug nanoparticles in the PSN-1 monolayer cell and PSN-1/HSPC co-cultured tumor spheroids model was evaluated. The results showed that SQ-CHI prodrug molecules and FA-SQ-CHI NPs were successfully developed. The nanoparticles were regular spherical, well-dispersed, with a particle size of (173.3 ± 1.5) nm, a drug load of (59.02 ± 0.8) % and showed trypsin responsive release ability. The prodrug nanoparticles can significantly enhance the penetration and anti-proliferation effects of CHI in the PSN-1/HSPC tumor spheroids. In conclusion, the construction of folic acid-modified SQ-CHI prodrug self-assembled nanoparticles can significantly enhance the penetration of CHI in the pancreatic cancer microenvironment in vitro. This research would provide a new idea for the construction of targeted drug delivery system for chemical drugs and Chinese medicine hydrophilic small molecule drugs in the application of anti-pancreatic cancer.

Construction of squalene producing cell factories and screening, cloning and expression of key genes / 生物工程学报

Squalene is widely used in pharmaceutical, nutraceutical, cosmetics and other fields because of its strong antioxidative, antibacterial and anti-tumor activities. In order to produce squalene, a gene ispA encoding farnesyl pyrophosphate synthase was overexpressed in a previously engineered Escherichia coli strain capable of efficiently producing terpenoids, resulting in a chassis strain that efficiently synthesizes triterpenoids. Through phylogenetic analysis, screening, cloning and expression of squalene synthase derived from different prokaryotes, engineered E. coli strains capable of efficiently producing squalene were obtained. Among them, squalene produced by strains harboring squalene synthase derived from Thermosynechococcus elongatus and Synechococcus lividus reached (16.5±1.4) mg/g DCW ((167.1±14.3) mg/L broth) and (12.0±1.9) mg/g DCW ((121.8±19.5) mg/L broth), respectively. Compared with the first-generation strains harboring the human-derived squalene synthase, the squalene synthase derived from T. elongatus and S. lividus remarkably increased the squalene production by 3.3 times and 2.4 times, respectively, making progress toward the cost-effective heterologous production of squalene.

Construction and optimization of squalene epoxide synthetic pathway in Escherichia coli / 生物工程学报

Triterpenoids are a class of natural products of great commercial value that are widely used in pharmaceutical, health care and cosmetic industries. The biosynthesis of triterpenoids relies on the efficient synthesis of squalene epoxide, which is synthesized from the NADPH dependent oxidation of squalene catalyzed by squalene epoxidase. We screened squalene epoxidases derived from different species, and found the truncated squalene epoxidase from Rattus norvegicus (RnSETC) showed the highest activity in engineered Escherichia coli. Further examination of the effect of endogenous cytochrome P450 reductase like (CPRL) proteins showed that overexpression of NADH: quinone oxidoreductase (WrbA) under Lac promoter in a medium-copy number plasmid increased the production of squalene epoxide by nearly 2.5 folds. These results demonstrated that the constructed pathway led to the production of squalene epoxide, an important precursor for the biosynthesis of triterpenoids.

Cloning and Functional Characterization of Full-length cDNA Encoding Squalene Synthase from Fritillaria thunbergii Miq / 中国生物化学与分子生物学报

Squalene is a key metabolic intermediate for sterols and various other triterpenoids. Its biosynthesis is catalyzed by squalene synthase (SQS), which converts two molecules of farnesyl pyrophosphate to squalene. The biosynthetic pathway of Fritillaria thunbergii Miq isosteroid alkaloids is similar to that of triterpenoids. In this study, a full-length cDNA of squalene synthase from Fritillaria thunbergii Mig (FtSQS) was cloned using rapid amplification from cDNA ends (RACE) technology. GenBank accession number was KF551097. 2. Bioinformatics methods were used to characterize the FtSQS in detail, including the detection of conserved regions, sequence homology analysis, secondary and tertiary structure prediction, and phylogenetic tree analysis. The results showed that its open reading frame (ORF) was 1 230 bp and encoded 409 amino acids. Protein-Blast alignment found that amino acid homology with SQS of Indian pine, Truncate alfalfa, Purple shirt, Potato, Bupleurum, Golden iron lock and Arabidopsis reached 73. 84%, 73. 23%, 72. 24%, 70. 66%, 70. 66%, 69. 44%, 68. 14%. Promoter analysis indicated that the 5' upstream region of FtSQS possessed various potential elements associated with physiological and environmental factors. To obtain a soluble recombinant protein, 24 hydrophobic amino acids were deleted from the carboxyl terminus, and the C-terminal truncated mutant FtSQS (FtSQSATM) was expressed in E. coli BL21 (DE3). SDS-PAGE analysis suggested that approximately 66 kD recombinant protein was checked. The in vitro enzymatic reaction proved that FtSQS could catalyze farnesyl pyrophosphate to generate squalene. Expression level of FtSQS mRNA in leaves was the highest, followed by stem and root, but in bulb was much lower than that in other tissues. It suggests that leaves are active organ for biosynthesis of peimine. The identification and function of FtSQS provides an important basis for the study of secondary metabolites of Fritillaria thunbergii Miq.

Cloning and prokaryotic expression analysis of squalene synthase CpSQS1 and CpSQS2 from Crataegus pinnatifida / 中国中药杂志

In order to understand the structural characteristics of squalene synthase genes in the triterpenoids biosynthesis pathway of Crataegus pinnatifida, the squalene synthase genes of C. pinnatifida was cloned and analyzed by bioinformatics and prokaryotic expression. Two squalene synthase genes CpSQS1 and CpSQS2 were cloned from C. pinnatifida fruit by RT-PCR. The ORF length of CpSQS1 and CpSQS2 were 1 239 bp and 1 233 bp respectively, encoding 412 aa and 410 aa respectively. CpSQS1 and CpSQS2 were predicted to be stable acidic proteins by online tools. The secondary structure was mainly composed of α-helix structure, and the tertiary structure was predicted by homology modeling. Structural functional domain analysis showed that 35-367 aa of CpSQS1 and CpSQS2 cDNA containing conserved trans-isoprenyl pyrophosphate synthase domains. Transmembrane domain analysis predicted that two transmembrane domains were founded in CpSQS1 and CpSQS2. The squalene synthase amino sequence of C. pinnatifida had higher homology with the known SQS of Salvia miltiorrhiza and Glycyrrhiza glabra. Phylogenetic tree analysis showed that CpSQS1 and CpSQS2 were clustered into one branch of MdSQS1 and MdSQS2, which were consistent with the phylogenetic rule. Prokaryotic expression vector pGEX-4 T-1-CpSQS1 and pGEX-4 T-1-CpSQS2 were transformed into Escherichia coli Transetta(DE3) for induction, and the target protein was successfully expressed at 65 kDa. The expression levels of CpSQS2 were significantly higher than that of CpSQS1 in three different developmental stages of C. pinnatifida. In this study, the full-length cDNA sequences of C. pinnatifida SQS1 and SQS2 were cloned and analyzed for the first time, which provided the foundation for further study on the metabolic pathway of C. pinnatifida triterpenoids.

A Computational Approach On Understanding Structural Interactions Of Envelope Protein Of Dengue Virus Bound With Squalene, A Prototype Anti-Viral Compound

Objective: The objective of the work was to validate the structural binding affinity of Squalene with the envelope protein of Dengue virus by means of molecular simulations. Methods: Three-dimensional (3D) structure of dengue 2 virus envelope protein was retrieved from Protein Data Bank PDB and Squalene compound from the ZINC database. Molecular docking between the E protein and Squalene were carried out by means of Auto Dock 4.2. Results: Based on the study, it was observed that the binding/docking energy for the complex structure was calculated to be-5.55 kcal/mol. Critical residues to interact with E protein were scrutinized by analyzing the interface of the complex within 4 Å proximity. Residues such as Thr 48, Glu49, Ala 50, Val 130, Leu 135, Ser 186, Pro 187, Thr 189, Gly 190, Leu 191, Phe 193, Leu 198, Leu 207, Thr 268, Phe 279, Thr 280, Gly 281, His 282 and Leu 283 were found to be non-covalently located around the squalene. Conclusion: Scopes to design de novo anti-viral compounds to the dengue viruses by using squalene as a new class of template structure have also been concisely brought into fore.

Anti-inflammatory effects of volatile oils of Desmodium styracifolium via regulation of TRP channels / 中草药

Objective To screen out the key chemical constituents and target protein of essential oil of Desmodium styracifolium for its anti-inflammatory effect. Methods Steam distillation method was used to extract the volatile oils from D. styraci folium, and its chemical constituents were identified by GC-MS, and the relative content of chemical constituents was determined by peak area normalization. The small molecule ligand library was established based on Traditional Chinese Medicine Systems Pharmacology (TCMSP). Reverse target prediction was conducted online using Swiss Target Prediction, the anti-inflammatory pathways were screened by KOBAX 3.0, conducting energy match between the key small molecular and the target protein in the TRP channels by molecular docking (SYBYL2.1). Construction of chemical constituents-targets network model was based on Cytoscape 3.5.1. Results A total of 48 chromatographic peaks were detected from D. styracifolium volatile oils, and 33 kinds of compound structure were determined by searching in mass spectral database and document retrieval, which account for 90.1% of total volatile oils. There were 17 key chemical constituents, and 88 target proteins were selected. TRP channels included 11 potential targets. Through molecular docking, we found that the phytol, hentriacontane, farnesyl acetone, and squalene were the key anti-inflammatory chemical constituents of D. styraci folium volatile oils. TPRV1 (transient receptor potential cation channel, subfamily V, member 1), PRKCB (protein kinase C, beta), and PRKCD (protein kinase C, delta) (degree > 10) are the key anti-inflammatory target protein. Conclusion We preliminarily select the key anti-inflammatory target and active constituents of D. styraci folium volatile oils from this study, and this research provides the theoretical basis for the development and application of its products.

Adaptive evolution analysis of squalene synthase in medicinal plants of Araliaceae / 中草药

Objective: To analyze the adaptive evolution of squalene synthase (SS) in the medicinal plants of Araliaceae. Methods: The adaptive evolutionary analysis of 23 SS genes of seven medicinal plants of Araliaceae was carried out by using the branch model, site model, branch-site model, MEC model, SLAC, FEL, and REL of PAML software. Results: In the analysis of PAML and MEC models, most of the branches and loci were found to be under strong negative selection, and no positive selection sites were found. The analysis by SLAC, FEL, and REL also showed that there were a large number of negative selection sites, only 412P, 413N, and 415K were positive selection sites. Conclusion: This indicates that negative selection plays a leading role in SS gene of Araliaceae. The 412P, 413N, and 415K sites found may be involved in the activity of SS.

Cloning and Prokaryotic Expression of Squalene Epoxidase Gene from Panax vietnamensis var. fuscidiscus / 中国实验方剂学杂志

Objective: To clone the squalene epoxidase genes of Panax vietnamensis var. fuscidiscus(PvfSE),and perform bioinformatics analysis and prokaryotic expression. Method: Total RNA was extracted from root of P. vietnamensis var. fuscidiscus by trizol method, and reverse-transcribed into first stand of cDNA. Specific primers for PvfSE cloning were designed according to the transcriptome data of P. vietnamensis var. fuscidiscus,and the cDNA sequence of PvfSE gene was isolated. Bioinformatics of PvfSE was analyzed by relevant software. The prokaryotic expression vector pMal-c2X-PvfSE was built to express recombinant protein in Escherichia coli cells. Result: The PvfSE gene contained a 1 887 bp open reading frame,encoding a predicted protein of 628 amino acids. The calculated molecular weight was 68.8 kDa,the theoretical isoelectric point was 9.28,the aliphatic index was 95.18,the grand average of hydropathicity was -0.060, and the instability index was 40.36. The protein was unstable. Bioinformatics analysis showed that PvfSE had two transmembrane domains and no signal peptide. PvfSE was most likely to be located in chloroplast or cytoplasmic membrane. PvfSE was a mixed protein with FAD/NAD(P) binding domain and squalene epoxidase domain. Sequence alignment and phylogenetic analysis demonstrated that PvfSE had a relatively close relationship with CpSE1,CpSE3,OsSE1 and OsSE2,which was involved in the biosynthesis of triterpene saponins in Cucurbita pepo and Ononis spinosa. In addition,PvfSE protein was expressed in E. coli. Conclusion: In this study,PvfSE gene was cloned and expressed in BL21(DE3),which lays a foundation for the further study on the gene functions of PvfSE and the biosynthetic pathway of triterpenoid saponins in P. vietnamensis var. fuscidiscus.

Cloning and expression analysis of three critical triterpenoid pathway genes in Osmanthus fragrans

Background: Osmanthus fragrans is an important ornamental tree and has been widely planted in China because of its pleasant aroma, which is mainly due to terpenes. The monoterpenoid and sesquiterpenoid metabolic pathways of sweet osmanthus have been well studied. However, these studies were mainly focused on volatile small molecule compounds. The molecular regulation mechanism of synthesis of large molecule compounds (triterpenoids) remains unclear. Squalene synthase (SQS), squalene epoxidase (SQE), and beta-amyrin synthase (BETA-AS) are three critical enzymes of the triterpenoid biosynthesis pathway. Results: In this study, the full-length cDNA and gDNA sequences of OfSQS, OfSQE, and OfBETA-AS were isolated from sweet osmanthus. Phylogenetic analysis suggested that OfSQS and OfSQE had the closest relationship with Sesamum indicum, and OfBETA-AS sequence shared the highest similarity of 99% with that of Olea europaea. The qRT-PCR analysis revealed that the three genes were highly expressed in flowers, especially OfSQE and OfBETA-AS, which were predominantly expressed in the flowers of both "Boye" and "Rixiang" cultivars, suggesting that they might play important roles in the accumulation of triterpenoids in flowers of O. fragrans. Furthermore, the expression of OfBETA-AS in the two cultivars was significantly different during all the five flowering stages; this suggested that OfBETA-AS may be the critical gene for the differences in the accumulation of triterpenoids. Conclusion: The evidence indicates that OfBETA-AS could be the key gene in the triterpenoid synthesis pathway, and it could also be used as a critical gene resource in the synthesis of essential oils by using bioengineered bacteria.

Cloning and expression analysis of squalene epoxidase genes from Siraitia grosvenorii / 中国中药杂志

Siraitia grosvenorii, vine plant of Cucurbitaceae family, has been used as natural sweetener and folk medicine. The major components and sweet substances are both known as mogrosides which are cucurbitane-type tetra-triterpenoids. Squalene epoxidase (SQE) has been generally recognized as the common rate-limiting enzyme in triterpenes and phytosterols, catalyzing into their common precursor 2,3-oxidosqualene (OS); however, in the biosynthesis of mogrosides, the precursor was 2,3,22,23-dioxidosqualene (DOS) instead of OS. To explore the specific SQE in S. grosvenorii, we cloned two full-length SQEs (SgSQE1, SgSQE2), performed bioinformatic analysis, analyzed the expression patterns in different periods of fruits by Real-time PCR, and induced the prokaryotic expressions. Finally, the interactive sites between SQE and substrate were predicted by docking, which would provide evidence for SQE gene function study of mogrosides and also lay foundation for triterpene biosynthesis in other plants. SgSQE1 and SgSQE2 both encoded predicted proteins of 524 amino acids, and shared 84% identity to each other at residues level, but had high specificity at N-terminal region. They both accumulated in fruits, but with different patterns, SgSQE1 increased rapidly and reached the highest level at 15 d, which had identical co-expression pattern with cucurbitadienol synthase (CS). SgSQE2 had a relatively constant level. The docking results showed that predicted proteins of SgSQE1 and SgSQE2 can interact with OS, with different contact sites (R348 for SgSQE1, H349 for SgSQE2). The recombinant proteins had no activities by prokaryotic expression, which were caused by transmembrane regions. However, all the results strongly suggested that SgSQEs were both involved in secondary metabolites biosynthesis in S. grosvenorii. SgSQE1 might be involved in mogrosides biosynthesis and SgSQE2 might participate in other cucurbitane-type triterpenes or phytosterols biosynthesis.

Cloning and expression analysis of squalene synthase gene in Hedera helix / 中草药

Objective To obtain a full-length cDNA of squalene synthase gene from Hedera helix (HhSS) by cloning technique, and to carry out bioinformatics analysis and expression analysis. Methods Primers were designed based on H. helix transcriptome data, and HhSS was cloned by using RACE technologies. DNAMAN, PROTPARAM, TMHMM, PSORT, ScanProsite, SOPMA, and SWISS-MODEL were used for analysis of sequence and physical and chemical properties and domain of encoded protein. The relative expression of HhSS was detected by qRT-PCR. Results The cDNA sequence of HhSS (GenBank accession number: KX056078) was 1 889 bp which obtained by RACE cloning. It contained an ORF from 248 bp to 1 477 bp and a 5'UTR with 247 bp and a 3'UTR with 412 bp. It encoded a 409-amino-acid protein with a molecular weight of 46 800and an isoelectric point (pI) of 5.68. The HhSS protein had the characteristic domain and transmembrane region of plant SS protein and closer relationship with Eleutherococcus senticosus, Panax ginseng et al. The qRT-PCR results indicated that it had positive correlation between relative expressing level of HhSS gene and contents of saponins in H. helix leaves. Conclusion The cloning and expression analysis results of HhSS provide a theoretical and technical basis for elucidating the role of HhSS in saponins biosynthetic pathway and metabolic regulation.

Cloning, bioinformatics, and expression analysis of squalene epoxidase in Antrodia cinnamomea / 中草药

Objective To clone the squalene epoxidase gene of Antrodia cinnamomea (AcSE) and analyze the bioinformatics and expression of the gene. Methods AcSE was cloned by rapid-amplification of cDNA ends (RACE) from cDNA of A. cinnamomea. The physical and chemical properties of AcSE protein were analyzed, and its secondary structure, tertiary structure, and function were predicted by using bioinformatics analysis. The expression of AcSE in mycelium and fruit body of A. cinnamomea at different culture time was detected by using quantitative real-time PCR (qRT-PCR). Results The full-length cDNA sequence of AcSE were 1 446 bp (Genbank: KT070558), encoding a 481-amino-acid polypeptide. The molecular weight of AcSE was 53 300 and pI was 6.36. Domain analysis results showed that AcSE had three transmembrane domains without coiled-coil structure, and hydrophobic and hydrophilic regions existed alternately. The gDNA sequence of AcSE was 1 607 bp, contained four exons and three introns. A gene expression analysis by relative qRT-PCR showed that the highest expression level of AcSE was in mycelia incubated for 7 d of A. cinnamomea, and it was 7.89 times than that in fruiting body, and a gradual decline was observed with the extension of the culture time. Conclusion Gene AcSE was firstly cloned from A. cinnamomea, and it would lay a foundation for exploring the mechanism of terpenoid biosynthesis in A. cinnamomea.

Construction of prokaryotic expression and over-expression vectors of squalene epoxidase gene from Sanghuangporus baumii / 中草药

Objective To obtain prokaryotic expression and over-expression vectors of squalene epoxidase (SE) gene from Sanghuangporus baumii. Methods The entire protein-coding cDNA of SE was cloned into the expression vector pET-32a (+). Then the recombinant plasmid was transformed into Escherichia coli BL21 (DE3) cells. SDS-PAGE was used to investigate the situation of expression after IPTG induction for 2-10 h. Additionally, primers were designed according to the gpd promoter sequence of Lentinula edodes in GenBank, and the gpd promoter fragment was obtained by PCR. Subsequently, the plant binary expression vector pCAMBIA1301 was selected as the basic vector, and then the 35 S promoter replaced with L. edodes gpd promoter through enzyme digestion and connection. Finally, the coding region of SE was cloned to the downstream of the gpd promoter to construct over-expression vectors. Results The prokaryotic expression vector pET-32a-SE was successfully obtained. SDS-PAGE results showed a significant protein band was found in the vicinity of the relative molecular weight of approximately 55 000, consistent with molecular weight of the predicted protein. Moreover, the over-expression vector pCAMBIA1301-gpd-gpd-SE was constructed successfully through different detection ways. Conclusion These results lay the foundation for the further study of SE in triterpenoid biosynthesis pathway of S. baumii.

Effect of light quality on total gypenosides accumulation and related key enzyme gene expression in Gynostemma pentaphyllum / 中草药·英文版

Objective: Light quality has effect on the accumulation of gypenosides in the medicinal plant Gynostemma pentaphyllum in the family Cucurbitaceae, while the squalene synthase (SS) and squalene epoxidase (SE) are the key enzymes for gypenoside biosynthesis. The objective of this study was to elucidate the relationship between light quality and biosynthesis key enzyme involving the regulation of gypenoside accumulation. Methods: The content of total gypenosides was measured by colorimetric method and the expression of SS and SE gene was determined by quantitative Real-time PCR in the seedlings of G. pentaphyllum which were grown with different light quality. Results: Light quality showed remarkable impacts on the accumulation of total gypenosides. The highest content of total gypenosides in the plant under red light condition was determined, followed by blue light and white light, while the lowest content was recorded under dark condition. qRT-PCR analysis proved that the expression levels of SS and SE genes were also affected by light quality. The high-level gene expressions of SS and SE were found in the plant under red light condition, followed by blue light, with the least content in darkness. The statistical analysis revealed that the total gypenosides were significantly different in different light treatment and the content of total gypenosides was positively related to the expression of SS and SE genes. Conclusions: Light quality regulates gypenoside accumulation via altering the expression of SS and SE in G. pentaphyllum.

Effects of squalene on expression of LDLR in HepG2 cells and its mechanism / 中国药理学通报

Aim To investigate the effect of squalene on LDLR expression in HepG2 cells and its mechanism of down-regulated cholesterol. Methods The prolifer-ation of HepG2 cells exposed to squalene at different concentrations was measured by MTT assay. The effect of squalene on the expression of LDLR in HepG2 cells was measured by flow cytometry and fluorescence mi-croscopy. The effect of different concentrations of squa-lene on the interaction between SCAP and Insig2, two key protein molecules of SREBP pathway, was assayed by FRET technology. Results MTT results showed that squalene had inhibitory effect on the proliferation of HepG2 cells in a dose-dependent manner. Flow cy-tometry and fluorescence microscopy results showed that squalene enhanced LDLR expression in HepG2 cells compared with the control group. The results of FRET technology revealed that compared with model control group, the YFP fluorescence value in Squalene group dramatically declined, and the YFP fluorescence value of each drug group decreased with the range of 5~25 μmol·L-1 squalene concentration. Conclusions Squalene may promote the expression of LDLR in HepG2 cells through inhibiting the interaction between SCAP and Insig2 proteins in SREBP pathway, which may confirm that squalene is a potential novel drug for the down-regulation of cholesterol level.