Ginsenoside-Rb1 Improved Diabetic Cardiomyopathy through Regulating Calcium Signaling by Alleviating Protein O-GlcNAcylation

Ginsenoside-Rb1 (Rb1), a major active component of ginseng, has many benefits for cardiovascular disease and diabetes mellitus (DM), but the effect and mechanism on diabetic cardiomyopathy are not clear. In the present study, we found that Rb1-feeding significantly improved cardiac dysfunction and abnormal cardiomyocytes calcium signaling caused by diabetes. This improved calcium signaling was because Rb1 reduced Ca²⁺ leakage caused by overactivated ryanodine receptor 2 (RyR2) and increased Ca²⁺ uptake by sarcoplasmic reticulum Ca²⁺-ATPase 2a (SERCA 2a). Furthermore, we found that Rb1 not only enhanced energy metabolism like metformin and eliminated O-GlcNAcylation of calcium handling proteins to regulate calcium signaling but also directly inhibited RyR2 activity to regulate calcium signaling. The present study indicated that as a health supplement or drug, Rb1 was a relatively effective auxiliary therapeutic substance for diabetic cardiomyopathy.

Direct Use of Carboxylic Acids in the Photocatalytic Hydroacylation of Styrenes To Generate Dialkyl Ketones

A general protocol for the hydroacylation of styrenes from aliphatic carboxylic acids is reported. These reactions proceed via β-scission of a phosphoranyl radical that is accessed by photoredox catalysis, followed by addition of the resulting acyl radical to the styrenyl olefin. We show that phosphine tunability is critical for efficient intermolecular coupling due to competitive quenching of the photocatalyst by the olefin. Primary, secondary, and structurally rigid tertiary carboxylic acids all generate valuable unsymmetrical dialkyl ketones.

3-Substituted 1-Naphthamidomethyl-C-galactosyls Interact with Two Unique Sub-sites for High-Affinity and High-Selectivity Inhibition of Galectin-3

The galectins are a family of galactose-binding proteins playing key roles in inflammatory processes and cancer. However, they are structurally very closely related, and discovery of highly selective inhibitors is challenging. In this work, we report the design of novel inhibitors binding to a subsite unique to galectin-3, which confers both high selectivity and affinity towards galectin-3. Olefin cross metathesis between allyl β-C-galactopyranosyl and 1-vinylnaphthalenes or acylation of aminomethyl β-C-galactopyranosyl with 1-naphthoic acid derivatives gave C-galactopyranosyls carrying 1-naphthamide structural elements that interacted favorably with a galectin-3 unique subsite according to molecular modeling and X-ray structural analysis of two inhibitor-galectin-3 complexes. Affinities were down to sub-µM and selectivities over galectin-1, 2, 4 N-terminal domain, 4 C-terminal domain, 7, 8 N-terminal domain, 9 N-terminal domain, and 9 C-terminal domain were high. These results show that high affinity and selectivity for a single galectin can be achieved by targeting unique subsites, which holds promise for further development of small and selective galectin inhibitors.

N-Acyl Amino Acids: Metabolism, Molecular Targets, and Role in Biological Processes

The lipid signal is becoming increasingly crowded as increasingly fatty acid amide derivatives are being identified and considered relevant therapeutic targets. The identification of N-arachidonoyl-ethanolamine as endogenous ligand of cannabinoid type-1 and type-2 receptors as well as the development of different–omics technologies have the merit to have led to the discovery of a huge number of naturally occurring N-acyl-amines. Among those mediators, N-acyl amino acids, chemically related to the endocannabinoids and belonging to the complex lipid signaling system now known as endocannabinoidome, have been rapidly growing for their therapeutic potential. Here, we review the current knowledge of the mechanisms for the biosynthesis and inactivation of the N-acyl amino acids, as well as the various molecular targets for some of the N-acyl amino acids described so far.

Ghrelin forms in the modulation of energy balance and metabolism

Ghrelin is a gastric hormone circulating in acylated (AG) and unacylated (UnAG) forms. This narrative review aims at presenting current emerging knowledge on the impact of ghrelin forms on energy balance and metabolism. AG represents ~ 10% of total plasma ghrelin, has an appetite-stimulating effect and is the only form for which a receptor has been identified. Moreover, other metabolic AG-induced effects have been reported, including the modulation of glucose homeostasis with stimulation of liver gluconeogenesis, the increase of fat mass and the improvement of skeletal muscle mitochondrial function. On the other hand, UnAG has no orexigenic effects, however recent reports have shown that it is directly involved in the modulation of skeletal muscle energy metabolism by improving a cluster of interlinked functions including mitochondrial redox activities, tissue inflammation and insulin signalling and action. These findings are in agreement with human studies which show that UnAG circulating levels are positively associated with insulin sensitivity both in metabolic syndrome patients and in a large cohort from the general population. Moreover, ghrelin acylation is regulated by a nutrient sensor mechanism, specifically set on fatty acids availability. These recent findings consistently point towards a novel independent role of UnAG as a regulator of muscle metabolic pathways maintaining energy status and tissue anabolism. While a specific receptor for UnAG still needs to be identified, recent evidence strongly supports the hypothesis that the modulation of ghrelin-related molecular pathways, including those involved in its acylation, may be a potential novel target in the treatment of metabolic derangements in disease states characterized by metabolic and nutritional complications.Level of evidence Level V, narrative review.

O-GlcNAcylation and phosphorylation of β-actin Ser199 in diabetic nephropathy

The function of actin is regulated by various posttranslational modifications. We have previously shown that in the kidneys of nonobese type 2 diabetes model Goto-Kakizaki rats, increased O-GlcNAcylation of β-actin protein is observed. It has also been reported that both O-GlcNAcylation and phosphorylation occur on Ser199 of β-actin. However, their roles are not known. To elucidate their roles in diabetic nephropathy, we examined the rat kidney for changes in O-GlcNAcylation of Ser199 (gS199)-actin and in the phosphorylation of Ser199 (pS199)-actin. Both gS199- and pS199-actin molecules had an apparent molecular weight of 40 kDa and were localized as nonfilamentous actin in both the cytoplasm and nucleus. Compared with the normal kidney, the immunostaining intensity of gS199-actin increased in podocytes of the glomeruli and in proximal tubules of the diabetic kidney, whereas that of pS199-actin did not change in podocytes but decreased in proximal tubules. We confirmed that the same results could be observed in the glomeruli of the human diabetic kidney. In podocytes of glomeruli cultured in the presence of the O-GlcNAcase inhibitor Thiamet G, increased O-GlcNAcylation was accompanied by a concomitant decrease in the amount of filamentous actin and in morphological changes. Our present results demonstrate that dysregulation of O-GlcNAcylation and phosphorylation of Ser199 occurred in diabetes, which may contribute partially to the causes of the morphological changes in the glomeruli and tubules. gS199- and pS199-actin will thus be useful for the pathological evaluation of diabetic nephropathy.

Both male and female gametogenesis require a fully functional protein S-acyl transferase 21 in Arabidopsis thaliana

S-Acylation is a reversible post-translational lipid modification in which a long chain fatty acid covalently attaches to specific cysteine(s) of proteins via a thioester bond. It enhances the hydrophobicity of proteins, contributes to their membrane association and plays roles in protein trafficking, stability and signalling. A family of Protein S-Acyl Transferases (PATs) is responsible for this reaction. PATs are multi-pass transmembrane proteins that possess a catalytic Asp-His-His-Cys cysteine-rich domain (DHHC-CRD). In Arabidopsis, there are currently 24 such PATs, five having been characterized, revealing their important roles in growth, development, senescence and stress responses. Here, we report the functional characterization of another PAT, AtPAT21, demonstrating the roles it plays in Arabidopsis sexual reproduction. Loss-of-function mutation by T-DNA insertion in AtPAT21 results in the complete failure of seed production. Detailed studies revealed that the sterility of the mutant is caused by defects in both male and female sporogenesis and gametogenesis. To determine if the sterility observed in atpat21-1 was caused by upstream defects in meiosis, we assessed meiotic progression in pollen mother cells and found massive chromosome fragmentation and the absence of synapsis in the initial stages of meiosis. Interestingly, the fragmentation phenotype was substantially reduced in atpat21-1 spo11-1 double mutants, indicating that AtPAT21 is required for repair, but not for the formation, of SPO11-induced meiotic DNA double-stranded breaks (DSBs) in Arabidopsis. Our data highlight the importance of protein S-acylation in the early meiotic stages that lead to the development of male and female sporophytic reproductive structures and associated gametophytes in Arabidopsis.

Observations on the Effects of Residualization and Dehalogenation on the Utility of N-Succinimidyl Ester Acylation Agents for Radioiodination of the Internalizing Antibody Trastuzumab

Trastuzumab is an antibody used for the treatment of human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancers. Since trastuzumab is an internalizing antibody, two factors could play an important role in achieving high uptake and prolonged retention of radioactivity in HER2-positive tumors after radioiodination-residualizing capacity after receptor-mediated internalization and susceptibility to dehalogenation. To evaluate the contribution of these two factors, trastuzumab was radiolabeled using the residualizing reagent N-succinimidyl 4-guanidinomethyl-3-[*I]iodobenzoate ([*I]SGMIB) and the nonresidualizing reagent N-succinimidyl-3-[*I]iodobenzoate ([*I]SIB), both of which are highly dehalogenation-resistant. Paired-label uptake and intracellular retention of [¹²⁵I]SGMIB-trastuzumab and [¹³¹I]SIB-trastuzumab was compared on HER2-expressing BT474 human breast carcinoma cells. Tumor uptake and normal tissue distribution characteristics for the two labeled conjugates were assessed in mice bearing BT474M1 xenografts. The internalization and intracellular retention of initially-bound radioactivity in BT474 cells was similar for the two labeled conjugates up to 4 h, but were significantly higher for [¹²⁵I]SGMIB-trastuzumab at 6 and 24 h. Similarly, [*I]SGMIB labeling resulted in significantly higher uptake and retention of radioactivity in BT474M1 xenografts at all studied time points. Moreover, tumor-to-tissue ratios for [¹²⁵I]SGMIB-trastuzumab were consistently higher than those for [¹³¹I]SIB-trastuzumab starting at 12 h postinjection. Thus, optimal targeting of HER2-positive breast cancers with a radioiodinated trastuzumab conjugate requires an acylation agent that imparts residualizing capacity in addition to high stability towards dehalogenation in vivo.

Biocatalytic Synthesis of Lipophilic Baicalin Derivatives as Antimicrobial Agents

Enzymatic acylation is commonly used to increase the lipophilicity of flavonoids. However, the absence of primary hydroxyl groups makes it challenging to acylate baicalin using traditional acylation methods. In this study, an enzymatic esterification strategy was developed to introduce fatty-acid chains into baicalin at its carboxyl group, hence successfully synthesizing a new series of baicalin ester derivatives in nonaqueous media. Under the optimal reaction conditions, up to 95% conversion of baicalin was achieved. Antimicrobial evaluation of the baicalin ester derivatives indicated a corresponding increase to that of C log P values, with a cutoff effect at C log P = 5.2. Baicalin ester derivatives with C log P values of 4.9-5.2 exhibited the most potent antimicrobial activity. Interestingly, the introduction of medium-length fatty alcohol chains not only increased lipophilicity but also endowed them with membrane-disrupting properties. This study, therefore, provides an understanding of the esterification of flavonoid glycosides and a prospective application of the ester derivatives.

A ZDHHC5-GOLGA7 Protein Acyltransferase Complex Promotes Nonapoptotic Cell Death

Lethal small molecules are useful probes to discover and characterize novel cell death pathways and biochemical mechanisms. Here we report that the synthetic oxime-containing small molecule caspase-independent lethal 56 (CIL56) induces an unconventional form of nonapoptotic cell death distinct from necroptosis, ferroptosis, and other pathways. CIL56-induced cell death requires a catalytically active protein S-acyltransferase complex comprising the enzyme ZDHHC5 and an accessory subunit GOLGA7. The ZDHHC5-GOLGA7 complex is mutually stabilizing and localizes to the plasma membrane. CIL56 inhibits anterograde protein transport from the Golgi apparatus, which may be lethal in the context of ongoing ZDHHC5-GOLGA7 complex-dependent retrograde protein trafficking from the plasma membrane to internal sites. Other oxime-containing small molecules, structurally distinct from CIL56, may trigger cell death through the same pathway. These results define an unconventional form of nonapoptotic cell death regulated by protein S-acylation.

Protein S-acyl transferase 15 is involved in seed triacylglycerol catabolism during early seedling growth in Arabidopsis

Seeds of Arabidopsis contain ~40% oil, which is primarily in the form of triacylglycerol and it is converted to sugar to support post-germination growth. We identified an Arabidopsis T-DNA knockout mutant that is sugar-dependent during early seedling establishment and determined that the β-oxidation process involved in catabolising the free fatty acids released from the seed triacylglycerol is impaired. The mutant was confirmed to be transcriptional null for Protein Acyl Transferase 15, AtPAT15 (At5g04270), one of the 24 protein acyl transferases in Arabidopsis. Although it is the shortest, AtPAT15 contains the signature 'Asp-His-His-Cys cysteine-rich domain' that is essential for the enzyme activity of this family of proteins. The function of AtPAT15 was validated by the fact that it rescued the growth defect of the yeast protein acyl transferase mutant akr1 and it was also auto-acylated in vitro. Transient expression in Arabidopsis and tobacco localised AtPAT15 in the Golgi apparatus. Taken together, our data demonstrate that AtPAT15 is involved in β-oxidation of triacylglycerol, revealing the importance of protein S-acylation in the breakdown of seed-storage lipids during early seedling growth of Arabidopsis.

Antiproliferative Acylated Glycerols from New Zealand Propolis

Previous work has shown that a number of phenolic components of NZ propolis possess antiproliferative activity against certain human gastrointestinal cancer cell lines. Here we report on a series of acylglycerols isolated from the nonpolar fraction of propolis resin, which represent further bioactive constituents unrelated to the more usual phenolic compounds generally found in propolis. NZ propolis is sourced from poplar trees, and the acylglycerols have been shown to be present in the leaves and buds of some common poplars. The compounds are a series of monoglycerides containing 3,8-dihydroxy fatty acids, many of which are further acylated with acetic acid residues. The dihydroxy fatty acids are C₁₈ to C₂₄, with the most abundant being C₂₀ and C₂₂. These acylglycerols were found to have strong antiproliferative activity against three human gastrointestinal cell lines, particularly gastric cancer cell line NCI-N87, where one example shows an IC₅₀ of less than 50 μM.

Changing Carrot Color: Insertions in DcMYB7 Alter the Regulation of Anthocyanin Biosynthesis and Modification

The original domesticated carrots (Daucus carota) are thought to have been purple, accumulating large quantities of anthocyanins in their roots. A quantitative trait locus associated with anthocyanin pigmentation in purple carrot roots has been identified on chromosome 3 and includes two candidate genes, DcMYB6 and DcMYB7 Here, we characterized the functions of DcMYB6 and DcMYB7 in carrots. Overexpression of DcMYB7, but not DcMYB6, in the orange carrot 'Kurodagosun' led to anthocyanin accumulation in roots. Knockout of DcMYB7 in the solid purple (purple periderm, phloem, and xylem) carrot 'Deep Purple' using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 system resulted in carrots with yellow roots. DcMYB7 could activate the expression of its DcbHLH3 partner, a homolog of the anthocyanin-related apple (Malus × domestica) bHLH3, and structural genes in the anthocyanin biosynthetic pathway. We determined that the promoter sequence of DcMYB7 in nonpurple carrots was interrupted either by DcMYB8, a nonfunctional tandem duplication of DcMYB7, or by two transposons, leading to the transcriptional inactivation of DcMYB7 in nonpurple carrot roots. As a result, nonpurple carrots fail to accumulate anthocyanins in their roots. Our study supports the hypothesis that another genetic factor suppresses DcMYB7 expression in the phloem and xylem of purple peridermal carrot root tissues. DcMYB7 also regulated the glycosylation and acylation of anthocyanins by directly activating DcUCGXT1 and DcSAT1 We reveal the genetic factors conditioning anthocyanin pigmentation in purple versus nonpurple carrot roots. Our results also provide insights into the mechanisms underlying anthocyanin glycosylation and acylation.

The Importance of Reaction Conditions on the Chemical Structure of N,O-Acylated Chitosan Derivatives

The structure of acylated chitosan derivatives strongly determines the properties of obtained products, influencing their hydrodynamic properties and thereby their solubility or self-assembly susceptibility. In the present work, the significance of slight changes in acylation conditions on the structure and properties of the products is discussed. A series of chitosan-acylated derivatives was synthesized by varying reaction conditions in a two-step process. As reaction media, two diluted acid solutions-i.e., acetic acid and hydrochloric acid)-and two coupling systems-i.e., 1-ethyl-3-(3-dimethyl-aminopropyl)-1-carbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide (EDC/NHS)-were used. The chemical structure of the derivatives was studied in detail by means of two spectroscopic methods, namely infrared and nuclear magnetic resonance spectroscopy, in order to analyze the preference of the systems towards N- or O-acylation reactions, depending on the synthesis conditions used. The results obtained from advanced ¹H-¹³C HMQC spectra emphasized the challenge of achieving a selective acylation reaction path. Additionally, the study of the molecular weight and solution behavior of the derivatives revealed that even slight changes in their chemical structure have an important influence on their final properties. Therefore, an exact knowledge of the obtained structure of derivatives is essential to achieve reaction reproducibility and to target the application.

Low-Background Acyl-Biotinyl Exchange Largely Eliminates the Coisolation of Non-S-Acylated Proteins and Enables Deep S-Acylproteomic Analysis

Protein S-acylation (also called palmitoylation) is a common post-translational modification whose deregulation plays a key role in the pathogenesis of many diseases. Acyl-biotinyl exchange (ABE), a widely used method for the enrichment of S-acylated proteins, has the potential of capturing the entire S-acylproteome in any type of biological sample. Here, we showed that current ABE methods suffer from a high background arising from the coisolation of non-S-acylated proteins. The background can be substantially reduced by an additional blockage of residual free cysteine residues with 2,2'-dithiodipyridine prior to the biotin-HPDP reaction. Coupling the low-background ABE (LB-ABE) method with label-free proteomics, 2 895 high-confidence candidate S-acylated proteins (including 1 591 known S-acylated proteins) were identified from human prostate cancer LNCaP cells, representing so-far the largest S-acylproteome data set identified in a single study. Immunoblotting analysis confirmed the S-acylation of five known and five novel prostate cancer-related S-acylated proteins in LNCaP cells and suggested that their S-acylation levels were about 0.6-1.8%. In summary, the LB-ABE method largely eliminates the coisolation of non-S-acylated proteins and enables deep S-acylproteomic analysis. It is expected to facilitate a much more comprehensive and accurate quantification of S-acylproteomes than previous ABE methods.

Polyacetate and Polycarbonate RNA: Acylating Reagents and Properties

Acylation of RNA at 2'-OH groups is widely applied in mapping RNA structure and recently for controlling RNA function. Reactions are described that install the smallest 2-carbon acyl groups on RNA-namely, 2'-O-acetyl and 2'-O-carbonate groups. Hybridization and thermal melting experiments are performed to assess the effects of the acyl groups on duplex formation. Both reagents can be employed at lower concentrations to map RNA secondary structure by reverse transcriptase primer extension (SHAPE) methods.

Dietary fatty acid profile influences circulating and tissue fatty acid ethanolamide concentrations in a tissue-specific manner in male Syrian hamsters

BACKGROUND

The discovery of N‑acylethanolamines (NAEs) has prompted an increase in research aimed at understanding their biological roles including regulation of appetite and energy metabolism. However, a knowledge gap remains to understand the effect of dietary components on NAE levels, in particular, heterogeneity in dietary fatty acid (DFA) profile, on NAE levels across various organs.

OBJECTIVE

To identify and elucidate the impact of diet on NAE levels in seven different tissues/organs of male hamsters, with the hypothesis that DFA will act as precursors for NAE synthesis in golden Syrian male hamsters.

METHOD

A two-month feeding trial was performed, wherein hamsters were fed various dietary oil blends with different composition of 18-C fatty acid (FA).

RESULTS

DFA directly influences tissue FA and NAE levels. After C18:1n9-enriched dietary treatments, marked increases were observed in duodenal C18:1n9 and oleoylethanolamide (OEA) concentrations. Among all tissues; adipose tissue brown, adipose tissue white, brain, heart, intestine-duodenum, intestine-jejunum, and liver, a negative correlation was observed between gut-brain OEA concentrations and body weight.

CONCLUSION

DFA composition influences FA and NAE levels across all tissues, leading to significant shifts in intestinal-brain OEA concentrations. The endogenously synthesized increased OEA levels in these tissues enable the gut-brain-interrelationship. Henceforth, we summarize that the brain transmits anorexic properties mediated via neuronal signalling, which may contribute to the maintenance of healthy body weight. Thus, the benefits of OEA can be enhanced by the inclusion of C18:1n9-enriched diets, pointing to the possible nutritional use of this naturally occurring bioactive lipid-amide in the management of obesity.

Discovery of New Triterpenoid Saponins Isolated from Maesa japonica with Antifungal Activity against Rice Blast Fungus Magnaporthe oryzae

While searching for new antifungal compounds, we revealed that a methanol extract of plant species Maesa japonica has a potent antifungal activity in vivo against rice blast fungus Magnaporthe oryzae. To identify the antifungal substances, the methanol extract of M. japonica was extracted by organic solvents, and consequently, six active compounds were isolated from the n-butanol layer. The isolated compounds were five new acylated triterpenoid saponins including maejaposide I (1), maejaposides C-1, C-2, and C-3 (2-4), and maejaposide A-1 (5), along with a known one, maejaposide A (6). These chemical structures were determined by NMR and a comparison of their NMR and MS data with those reported in the literature. Based on the in vitro antifungal bioassay, the five compounds (2-6) exhibited strong antifungal activity against M. oryzae with MIC values ranging from 4 to 32 μg/mL, except for maejaposide I (1) (MIC > 250 μg/mL). When the compounds were evaluated at concentrations of 125, 250, and 500 μg/mL for an in vivo antifungal activity against rice blast, compounds 2-6 strongly reduced the development of blast by at least 85% to 98% compared to the untreated control. However, compound 1 did not show any in vivo antifungal activity up to a concentration of 500 μg/mL. Taken together, our results suggest that the methanol extract of M. japonica and the new acylated triterpenoid saponins can be used as a source for the development of natural fungicides.

Identification of the O-GalNAcylation site(s) on FOXA1 catalyzed by ppGalNAc-T2 enzyme in vitro

FOXA1 functions as a pioneer factor of transcriptional regulation that binds to specific sites in the chromatin and recruits other transcription factors, promoting the initiation of gene transcription and mediating the regulation of downstream target gene expression. FOXA1 was reported to facilitate or reprogram ERα binding, thus playing a key function in breast cancer progression. Our previous results indicated that the O-linked N-acetylgalactosamine (O-GalNAc) modification of FOXA1 plays a potentially significant role in the ERα transcription network. However, further investigations are needed to identify the specific mechanism of modification and the specific glycosylation sites on FOXA1. In this study, we first suggested that FOXA1 could be O-GalNAcylated by ppGalNAc-T2 in vitro. By dividing and expressing recombinant FOXA1 as three segments, two O-GalNAcylation sites were found on FOXA1, both located at the C-terminal of the protein. Then, synthesized peptides, including the predicted O-GalNAc sites in the C-terminus of FOXA1, were used in a vitro reaction, and peptides mutated at the predicted O-GalNAc sites were employed as controls. Through an ESI-MS assay, S354 and S355 were identified as probable O-GalNAcylation sites on FOXA1. Additionally, we performed ESI-ETD-MS/MS analysis of the full-length O-GalNAcylated FOXA1 protein and identified S355 as the O-GalNAc modification site on FOXA1, consistent with the peptide reaction. In conclusion, our results demonstrated that FOXA1 can be O-GalNAcylated by ppGalNAc-T2 at S355 in vitro. These results will provide new insights for studying the role of O-GalNAcylation in the development of breast cancer.

O-GlcNAcylation of ITGA5 facilitates the occurrence and development of colorectal cancer

BACKGROUND/OBJECTIVE

Integrin α5 (ITGA5) as one member of integrins family, plays an important role in promoting cancer cell metastasis and invasion through inducing the communications among different cells or cells with extracellular matrix (ECM). However, the mechanisms underlying ITGA5 in colorectal cancer (CRC) progression need to be explored, especially for its O-GlcNAcylation. To this end, the current study was performed to explore the effects of O-GlcNAcylation on ITGA5 expression, as well as to probe the effects of ITGA5 O-GlcNAcylation on CRC progression.

METHODS

The expression profiles of ITGA5, OGT and O-GlcNAc in CRC tissues and cells were detected by immunohistochemistry (IHC), RT-PCR and western blotting. CCK-8, flow cytometry and xenotransplantation assays were used to assess cell growth, apoptosis and tumorigenesis. Immunoprecipitation (IP), in vitro O-GlcNAcylation of ITGA5 and enzymatic labelling of O-GlcNAc assays were used to detect the O-GlcNAcylation of ITGA5 protein.

RESULTS

The expression of ITGA5, OGT and O-GlcNAc were all elevated in CRC tissues and cells compared with the normal tissues and cells. Up-regulation of ITGA5 in CRC RKO cells enhanced cell growth and tumorigenesis while decreased cell apoptosis, while down-regulation of ITGA5 in CRC SW620 cells decreased cell growth and tumorigenesis and induced cell apoptosis. Besides, PUGNAc, GlcN or PUGNAc + GlcNAc treatment increased ITGA5 protein expression in RKO and SW620 cells, as well as increased its protein stability via enhancing its O-GlcNAcylation.

CONCLUSION

Collectively, the present study makes clear that ITGA5 overexpression accelerates the progression of CRC, which is closely associated to its enhanced O-GlcNAcylation.

Highly Acylated Anthocyanins from Purple Sweet Potato ( Ipomoea batatas L.) Alleviate Hyperuricemia and Kidney Inflammation in Hyperuricemic Mice: Possible Attenuation Effects on Allopurinol

Allopurinol is the first-line medication for hyperuricemia treatment. However, severe drug-related adverse effects have often been reported among patients who received allopurinol administration. This study is aimed at evaluating the possible attenuation effects of highly acylated anthocyanins from purple sweet potato (HAA-PSP) on hyperuricemia and kidney inflammation in hyperuricemic mice treated with allopurinol. In comparison with 5 mg kg^-1 allopurinol used alone, the combination of 25 mg kg^-1 HAA-PSP and 2.5 mg kg^-1 allopurinol could not only reduce serum uric acid level in hyperuricemic mice but also attenuate the kidney damage, as indicated by the level of serum biomarkers as well as histopathological examination. The inflammatory response was partially mitigated by inhibiting the protein expression of typical cytokines in the kidney. Our findings provide new evidence for the supplementary therapeutic potential of HAA-PSP with allopurinol on hyperuricemia and inflammation-related syndromes. Moreover, this study provides a theoretical basis for assessing the potential of anthocyanin-rich foods in health.

Proton Oriented-"Smart Depot" for Responsive Release of Ca2+ to Inhibit Peptide Acylation in PLGA Microspheres

PURPOSE

The purpose of this study was to characterize and detail the mechanism of a smart Ca²⁺ release depot (Ca₃(PO₄)₂) about its ability for sustainable inhibition on peptide acylation within PLGA microspheres.

METHODS

The octreotide acetate release and acylation kinetics were analyzed by RP-HPLC. Changes of Ca²⁺ concentration and adsorption behavior were determined by a Calcium Colorimetric Assay Kit. The inner pH changes were delineated by a classic pH sensitive probe, Lysosensor yellow/ blue® dextran. Morphological changes of microspheres, adsorption between polymer and additive, transformation of Ca₃(PO₄)₂ were characterized using SEM, FTIR and SSNMR separately.

RESULTS

Before and after microspheres formulation, the property and effectiveness of Ca₃(PO₄)₂ were investigated. Compared with a commonly used calcium salt (CaCl₂), high encapsulation efficiency (96.56%) of Ca₃(PO₄)₂ guarantees lasting effectiveness. In an increasingly acidic environment that simulated polymer degradation, the poorly water-soluble Ca₃(PO₄)₂ could absorb protons and transform into the more and more soluble CaHPO₄ and Ca(H₂PO₄)₂ to produce sufficient Ca²⁺ according to severity of acylation. The corresponding Ca²⁺ produce capacity fully met the optimum inhibition requirement since the real-time adsorption sites (water-soluble carboxylic acids) inside the degrading microspheres were rare. A sustained retention of three switchable calcium salts and slow release of Ca²⁺ were observed during the microsphere incubation. FTIR results confirmed the long-term inhibition effect induced by Ca₃(PO₄)₂ on the adsorption between drug and polymer.

CONCLUSIONS

With the presence of the smart Ca²⁺ depot (Ca₃(PO₄)₂) in the microspheres, a sustainable and long-term inhibition of peptide acylation was achieved.

Regiospecific methylation of all the hydroxyls in (+)-catechin by a stepwise differentiation strategy

BACKGROUND

Methylated derivatives of catechins have received great attention for health beneficial effects, especially antiallergic activity. However, the scarce natural abundance of methylated catechins limits further bioactive studies. The objective of this work was to investigate regiospecific methylation of the hydroxyls of (+)-catechin through a stepwise differentiation strategy based on electronic difference between the hydroxyl groups.

RESULTS

Selective methylation of the hydroxyls on different rings was realized by employing Meerwein salt as the methylation reagent. Preferential acylation of the phenolic hydroxyls on A and B rings allowed selective exposure of the aliphatic hydroxyl on C ring to methylation. The vicinal phenolic hydroxyls on B ring were preferentially methylated under mild basic condition due to the acidic properties. Methylation of the phenolic hydroxyls on A ring was achieved by sequential protection and deprotection operations. Finally, antioxidant activities of all the individual methylated (+)-catechins were explored by 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) assay.

CONCLUSION

Regiospecific methylation of the phenolic and aliphatic hydroxyls was systematically achieved under mild conditions. Preparation of all the individual methylated (+)-catechins was accomplished with a greener methylation reagent: nonvolatile Meerwein salt. This work laid a solid foundation for preparation of diverse O-methylated catechins for bioactivity studies. © 2019 Society of Chemical Industry.

Unacylated Ghrelin Does Not Acutely Affect Substrate Metabolism or Insulin Sensitivity in Men With Type 2 Diabetes

OBJECTIVE

Unacylated ghrelin (UAG) is suggested to improve insulin sensitivity and may have therapeutic potential. We therefore tested the effects of intravenous UAG infusion on glucose and lipid metabolism, insulin sensitivity, and energy expenditure in men with type 2 diabetes mellitus (T2DM).

DESIGN

Randomized, double-blind, placebo-controlled crossover study performed at a university hospital clinical research center.

METHODS

Ten men with T2DM completed two study days: (i) 6-hour UAG infusion (1 µg/kg/h) and (ii) 6-hour placebo infusion. The patients were investigated in the basal postabsorptive state for 4 hours, followed by a hyperinsulinemic clamp for 2 hours. The turnover rates of glucose and fatty acids were assayed by isotope tracer techniques. Energy expenditure was measured by indirect calorimetry.

RESULTS

The mean plasma UAG was 64.1 ± 11.3 pg/mL at baseline and increased >50-fold during UAG infusion. Plasma glucose was 7.0 ± 0.3 mmol/L during UAG infusion vs 6.7 ± 0.4 mmol/L placebo infusion (P = 0.43) at baseline and was not affected by UAG. During the hyperinsulinemic clamp, glucose infusion rates were 4.69 ± 0.56 mg/kg/min during UAG infusion vs 4.98 ± 0.43 mg/kg/min during placebo infusion (P = 0.66). UAG did not affect glucose oxidation, nonoxidative glucose disposal, lipolysis, energy expenditure, or respiratory exchange rate.

CONCLUSIONS

This study found that native UAG exposure did not exert acute metabolic effects in men with T2DM.

The interplay between molecular flexibility and RNA chemical probing reactivities analyzed at the nucleotide level via an extensive molecular dynamics study

Determination of the tridimensional structure of ribonucleic acid molecules is fundamental for understanding their function in the cell. A common method to investigate RNA structures of large molecules is the use of chemical probes such as SHAPE (2^'-hydroxyl acylation analyzed by primer extension) reagents, DMS (dimethyl sulfate) and CMCT (1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide metho-p-toluene sulfate), the reaction of which is dependent on the local structural properties of each nucleotide. In order to understand the interplay between local flexibility, sugar pucker, canonical pairing and chemical reactivity of the probes, we performed all-atom molecular dynamics simulations on a set of RNA molecules for which both tridimensional structure and chemical probing data are available and we analyzed the correlations between geometrical parameters and the chemical reactivity. Our study confirms that SHAPE reactivity is guided by the local flexibility of the different chemical moieties but suggests that a combination of multiple parameters is needed to better understand the implications of the reactivity at the molecular level. This is also the case for DMS and CMCT for which the reactivity appears to be more complex than commonly accepted.

Preparation and Characterization of Acylcaramel

Caramel is a widely used water-soluble food pigment. The acylation of caramel was conducted by aliphatic acyl chlorides with different chain lengths. Acetyl, butyryl, octyl, lauryl, palmityl, and stearyl caramels were prepared with the ratio of acyl chloride/caramel of 6. The formation of acylated caramel was confirmed by Fourier transform infrared spectra, and the acyl mass fraction in acylcaramel was determined by potentiometric titration. Thermal analysis showed that the weight loss of acylated caramel was higher than that of raw caramel. The scanning electron microscopy analysis showed that the morphology of acylated caramel was significantly different from that of raw material. The acyl mass fraction of acylated caramel increased with the increase of acyl chain lengths. Meanwhile, the lipo-hydro partition coefficient, the solubility in corn oil, and color, red, and yellow indexes increased with the increase of the mass fraction of acyl in acylcaramel. It was found that stearyl caramel has the highest lipid solubility of 5.73 mg/mL in corn oil; however, the color, red, and yellow indexes of palmityl caramel reached 25 818.60, 1.149, and 1.757, respectively. This study provides a method to improve the solubility of caramel in lipid phase and expand the application range of caramel.

Spectroscopic Characterization and Cytotoxicity Assessment towards Human Colon Cancer Cell Lines of Acylated Cycloartane Glycosides from Astragalus boeticus L

In several European countries, especially in Sweden, the seeds of the species Astragalus boeticus L. were widely used as coffee substitutes during the 19th century. Nonetheless, data regarding the phytochemistry and the pharmacological properties of this species are currently extremely limited. Conversely, other species belonging to the Astragalus genus have already been extensively investigated, as they were used for millennia for treating various diseases, including cancer. The current work was addressed to characterize cycloartane glycosides from A. boeticus, and to evaluate their cytotoxicity towards human colorectal cancer (CRC) cell lines. The isolation of the metabolites was performed by using different chromatographic techniques, while their chemical structures were elucidated by nuclear magnetic resonance (NMR) (1D and 2D techniques) and electrospray-ionization quadrupole time-of-flight (ESI-QTOF) mass spectrometry. The cytotoxic assessment was performed in vitro by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays in Caco-2, HT-29 and HCT-116 CRC cells. As a result, the targeted phytochemical study of A. boeticus enabled the isolation of three new cycloartane glycosides, 6-O-acetyl-3-O-(4-O-malonyl)-β-d-xylopyranosylcycloastragenol (1), 3-O-(4-O-malonyl)-β-d-xylopyranosylcycloastragenol (2), 6-O-acetyl-25-O-β-d-glucopyranosyl-3-O-β-d-xylopyranosylcycloastragenol (3) along with two known compounds, 6-O-acetyl-3-O-β-d-xylopyranosylcycloastragenol (4) and 3-O-β-d-xylopyranosylcycloastragenol (5). Importantly, this work demonstrated that the acetylated cycloartane glycosides 1 and 4 might preferentially inhibit cell growth in the CRC cell model resistant to epidermal growth factor receptor (EGFR) inhibitors.

Acylation derivatization based LC-MS analysis of 25-hydroxyvitamin D from finger-prick blood

Vitamin D metabolite analysis possessed significant clinical value for the pediatric department. However, invasive venipuncture sampling and high blood consumption inflicted much suffering on patients. For alleviation, we carried out a LC-MS method for 25-hydroxyvitamin D quantification in only 3 μl of plasma from the considerably less invasive finger-prick blood samples. To improve sensitivity, acylation on C3-hydroxyl (by isonicotinoyl chloride) rather than Diels-Alder adduction on s-cis-diene structure was for the very first time introduced into vitamin D metabolite derivatization. Compared with the existing derivatization approaches, this novel strategy not only prevented isomer interference, but also exhibited higher reacting throughput. For certification, the methodology was systematically validated and showed satisfying consistency with SRM927a. During clinical application, we found a convincing correlation between 25-hydroxyvitamin D and indirect/total bilirubin in jaundiced newborns. Such an observation indicated that vitamin D supplementation may help to achieve optimal outcomes in neonatal jaundice.

Acylated Lignans Isolated from Brachanthemum gobicum and Their Trypanocidal Activity

Eight isovaleryllignans (1-4 and 8-11), three isovalerylphenylpropanoids (5-7), three known lignans (12-14), and four known compounds were isolated from an extract of the aerial part of Brachanthemum gobicum. The structures of the isolated compounds were elucidated based on NMR and MS data analyses. The enantiomers of compounds 1-3, 5, 8, and 9 were isolated using chiral-phase HPLC, and the absolute configurations of 1a/1b-3a/3b, 5a/5b, 8a/8b, and 9a/9b were elucidated from their optical rotations and ECD spectra; the other lignans were assumed to be racemic or scalemic by chiral-phase HPLC analyses and optical rotation data. Some of the acylated lignans (racemic mixtures) (1-4, 8, 9, and 12-14) exhibited moderate inhibitory activities against Trypanosoma congolense, the causative agent of nagana disease in animals.

Simple alkanoyl acylating agents for reversible RNA functionalization and control

We describe the synthesis and RNA acylation activity of a series of minimalist azidoalkanoyl imidazole reagents, with the aim of functionalizing RNA at 2'-hydroxyl groups at stoichiometric to superstoichiometric levels. We find marked effects of small structural changes on their ability to acylate and be reductively removed, and identify reagents and methods that enable efficient RNA functionalization and control.

Quantitative Analysis of Protein S-Acylation Site Dynamics Using Site-Specific Acyl-Biotin Exchange (ssABE)

Protein S-acylation (palmitoylation) is a reversible lipid modification that is increasingly recognized as an important regulator of protein function, including membrane association, trafficking, and subcellular localization. Most proteomic methods to study palmitoylation allow characterization of putative palmitoylated proteins but do not permit identification of individual sites of palmitoylation. We have recently adapted the Acyl-Biotin Exchange (ABE) method that is routinely used for palmitoyl-proteome characterization, to permit global S-acylation site analysis. This site-specific ABE (ssABE) protocol, when combined with SILAC-based quantification, allows both the large-scale identification of palmitoylation sites and quantitative profiling of palmitoylation site changes. This approach enables palmitoylation to be studied at a systems level comparable to other more intensively studied post-translational modifications.

ETV5 regulates GOAT/ghrelin system in an mTORC1-dependent manner

Ghrelin, a 28 amino acid peptide hormone, regulates multiple important metabolic functions. Its acylation by ghrelin-O-acyl-transferase enzyme (GOAT) is required for binding to and activating its receptor, the growth hormone secretagogue receptor 1a. Mechanism underlying the regulation of GOAT and acyl ghrelin remains unclear. The present study demonstrated that ETV5 could transactivate GOAT promoter region and increase its expression, leading to subsequent increase in the production of acyl ghrelin. mTORC1 modulated ETV5 expression levels, likely via altering its protein stability, in the murine hypothalamic CLU122 cells and in mice. Moreover, ETV5 mediated the effects of mTORC1 signaling on the expression level of acyl ghrelin. Our study suggests a novel mTORC1-ETV5-GOAT/ghrelin axis in the regulation of ghrelin system. ETV5 may be a key regulator of mTORC1-GOAT/ghrelin axis in ghrelin producing cells and a potential therapeutic target for organism energy imbalance.

A Small-Molecule SIRT2 Inhibitor That Promotes K-Ras4a Lysine Fatty-Acylation

SIRT2, a member of the sirtuin family of protein lysine deacylases, has been identified as a promising therapeutic target for treating cancer. In addition to catalyzing deacetylation, SIRT2 has recently been shown to remove fatty acyl groups from K-Ras4a and promote its transforming activity. Among the SIRT2-specific inhibitors, only the thiomyristoyl lysine compound TM can weakly inhibit the demyristoylation activity of SIRT2. Therefore, more potent small-molecule SIRT2 inhibitors are needed to further evaluate the therapeutic potential of SIRT2 inhibition, and to understand the function of protein lysine defatty-acylation. Herein we report a SIRT2 inhibitor, JH-T4, which can increase K-Ras4a lysine fatty acylation. This is the first small-molecule inhibitor that can modulate the lysine fatty acylation levels of K-Ras4a. JH-T4 also inhibits SIRT1 and SIRT3 in vitro. The increased potency of JH-T4 is likely due to the formation of hydrogen bonding between the hydroxy group and SIRT1, SIRT2, and SIRT3. This is further supported by in vitro studies with another small-molecule inhibitor, NH-TM. These studies provide useful insight for future SIRT2 inhibitor development.

Evolution of metabolic novelty: A trichome-expressed invertase creates specialized metabolic diversity in wild tomato

Plants produce a myriad of taxonomically restricted specialized metabolites. This diversity-and our ability to correlate genotype with phenotype-makes the evolution of these ecologically and medicinally important compounds interesting and experimentally tractable. Trichomes of tomato and other nightshade family plants produce structurally diverse protective compounds termed acylsugars. While cultivated tomato (Solanum lycopersicum) strictly accumulates acylsucroses, the South American wild relative Solanum pennellii produces copious amounts of acylglucoses. Genetic, transgenic, and biochemical dissection of the S. pennellii acylglucose biosynthetic pathway identified a trichome gland cell-expressed invertase-like enzyme that hydrolyzes acylsucroses (Sopen03g040490). This enzyme acts on the pyranose ring-acylated acylsucroses found in the wild tomato but not on the furanose ring-decorated acylsucroses of cultivated tomato. These results show that modification of the core acylsucrose biosynthetic pathway leading to loss of furanose ring acylation set the stage for co-option of a general metabolic enzyme to produce a new class of protective compounds.

Amarisolide F, an Acylated Diterpenoid Glucoside and Related Terpenoids from Salvia amarissima

Nine terpenoids were isolated from the leaves and flowers of Salvia amarissima, including a new acylated diterpenoid glucoside, amarisolide F (1), a new neo-clerodane diterpenoid, amarissinin D (2), which was isolated as an acetyl derivative (2a), and four known diterpenoids. The structure of amarisolide F (1) was elucidated by NMR and MS data analyses, as well as its methanolysis products 7 and 8, which also constituted new diterpenoids, named amarissinin E and 8- epi-amarissinin E, respectively. The absolute configuration of compound 7 was established by single-crystal X-ray diffraction. The cytotoxicity and anti-MDR effect of 1 in three phenotypes of the MCF-7 cell lines were assayed. Compound 1 was 2-3.6-fold more active than amarissinins A (3) and B (4), but several orders of magnitude less active than teotihuacanin (6) and reserpine.

Exendin-4(Lys27 PAL)/gastrin/xenin-8-Gln: A novel acylated GLP-1/gastrin/xenin hybrid peptide that improves metabolic status in obese-diabetic (ob/ob) mice

BACKGROUND

Therapeutic benefits of peptide-based drugs is limited by rapid renal elimination.

METHODS

Therefore, to prolong the biological action profile of the recently characterized triple-acting hybrid peptide, exendin-4/gastrin/xenin-8-Gln, a fatty acid (C-16) has been covalently attached, creating exendin-4(Lys²⁷ PAL)/gastrin/xenin-8-Gln. Exendin-4/gastrin and liraglutide/gastrin/xenin-8-Gln were also synthesized as direct comparator peptides.

RESULTS

All hybrid peptides evoked significant concentration-dependent increases of insulin secretion from isolated murine islets and BRIN-BD11 cells. Following administration of peptides with glucose to mice, all hybrids significantly reduced the overall glycaemic excursion and increased insulin concentrations. In contrast to other treatments, exendin-4(Lys²⁷ PAL)/gastrin/xenin-8-Gln displayed impressive antihyperglycaemic actions even 12 hours after administration, highlighting protracted duration of effects. Exendin-4/gastrin/xenin-8-Gln, exendin-4/gastrin, and exendin-4(Lys²⁷ PAL)/gastrin/xenin-8-Gln were then progressed to a 31-day twice-daily treatment regimen in obese-diabetic ob/ob mice. All treatments decreased nonfasting glucose and HbA_1c concentrations, as well as enhancing circulating and pancreatic insulin levels. Exendin-4/gastrin and exendin-4/gastrin/xenin-8-Gln also decreased food intake. Glucose tolerance was improved by all treatments, but only exendin-4(Lys²⁷ PAL)/gastrin/xenin-8-Gln augmented glucose-induced insulin secretion. Interestingly, treatment regimens that included a xenin component induced clear advantages on the metabolic response to glucose-dependent insulinotropic polypeptide (GIP) and the glucose-lowering actions of insulin.

CONCLUSION

This study emphasizes the therapeutic promise of long-acting, multi-targeting hybrid gut peptides for type 2 diabetes.

Acylated pelargonidin glycosides from the red-purple flowers of Iberis umbellata L. and the red flowers of Erysimum × cheiri (L.) Crantz (Brassicaceae)

Five previously undescribed acylated pelargonidin 3-sophoroside-5-glucosides (pigments 2-6) were isolated from the red-purple flowers of Iberis umbellata L. 'Candycane Rose' and 'Candycane Red', in addition to a known one (pigment 1). The structures of five undescribed acylated anthocyanins were determined by chemical and spectroscopic methods to be pelargonidin 3-O-[2-O-(2-O-("acyl-A")-β-glucopyranosyl)-6-O-("acyl-B")-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], in which the "acyl-A" group was either trans-sinapic (2), trans-ferulic (3), trans-sinapic (4), trans-ferulic (5), or trans-ferulic acid (6), and "acyl-B" was either glucosyl-trans-p-coumaric acid (2), glucosyl-trans-p-coumaric acid (3), trans-feruloyl-glucosyl-trans-p-coumaric acid (4), trans-feruloyl-glucosyl-trans-p-coumaric acid (5), or glucosyl-trans-feruloyl-glucosyl-trans-p-coumaric acid (6). Moreover, three previously undescribed acylated pelargonidin 3-sambubioside-5-glucosides (pigments 7, 8, and 10) and one undescribed acylated pelargonidin 3-(3^X-glucosylsambubioside)-5-glucoside (pigment 9) were isolated from the red flowers of Erysimum × cheiri (L.) Crantz 'Aurora' as major anthocyanins. The structures of the three undescribed acylated pelargonidin 3-sambubioside-5-glucosides were determined to be pelargonidin 3-O-[2-O-(2-O-("acyl-C")-β-xylopyranosyl)-6-O-("acyl-D")-β-glucopyranoside]-5-O-(β-glucopyranoside), in which the "acyl-C" group was either non (7), non (8), or trans-p-coumaric acid (10) and "acyl-D" was either trans-p-coumaric (7), trans-ferulic (8), or trans-p-coumaric acid (10). Moreover, a previously undescribed acylated pelargonidin 3-(3^X-glucosylsambubioside)-5-glucoside was identified to be pelargonidin 3-O-[2-O-(2-O-(trans-p-coumaroyl)-3-O-(β-glucopyranosyl)-β-xylopyranosyl)-6-O-(trans-p-coumaroyl)-β-glucopyranoside]-5-O-(β-glucopyranoside) (9). In addition, the distribution of anthocyanidins structural elements in 24 Brassicaceous species is compared.

Lipid Headgroup Charge and Acyl Chain Composition Modulate Closure of Bacterial β-Barrel Channels

The outer membrane of Gram-negative bacteria contains β-barrel proteins that form high-conducting ion channels providing a path for hydrophilic molecules, including antibiotics. Traditionally, these proteins have been considered to exist only in an open state so that regulation of outer membrane permeability was accomplished via protein expression. However, electrophysiological recordings show that β-barrel channels respond to transmembrane voltages by characteristically switching from a high-conducting, open state, to a so-called 'closed' state, with reduced permeability and possibly exclusion of large metabolites. Here, we use the bacterial porin OmpF from E. coli as a model system to gain insight on the control of outer membrane permeability by bacterial porins through the modulation of their open state. Using planar bilayer electrophysiology, we perform an extensive study of the role of membrane lipids in the OmpF channel closure by voltage. We pay attention not only to the effects of charges in the hydrophilic lipid heads but also to the contribution of the hydrophobic tails in the lipid-protein interactions. Our results show that gating kinetics is governed by lipid characteristics so that each stage of a sequential closure is different from the previous one, probably because of intra- or intermonomeric rearrangements.

Towards take-all control: a C-21β oxidase required for acylation of triterpene defence compounds in oat

Oats produce avenacins, antifungal triterpenes that are synthesized in the roots and provide protection against take-all and other soilborne diseases. Avenacins are acylated at the carbon-21 position of the triterpene scaffold, a modification critical for antifungal activity. We have previously characterized several steps in the avenacin pathway, including those required for acylation. However, transfer of the acyl group to the scaffold requires the C-21β position to be oxidized first, by an as yet uncharacterized enzyme. We mined oat transcriptome data to identify candidate cytochrome P450 enzymes that may catalyse C-21β oxidation. Candidates were screened for activity by transient expression in Nicotiana benthamiana. We identified a cytochrome P450 enzyme AsCYP72A475 as a triterpene C-21β hydroxylase, and showed that expression of this enzyme together with early pathway steps yields C-21β oxidized avenacin intermediates. We further demonstrate that AsCYP72A475 is synonymous with Sad6, a previously uncharacterized locus required for avenacin biosynthesis. sad6 mutants are compromised in avenacin acylation and have enhanced disease susceptibility. The discovery of AsCYP72A475 represents an important advance in the understanding of triterpene biosynthesis and paves the way for engineering the avenacin pathway into wheat and other cereals for control of take-all and other diseases.

Fabrication of Stable and Self-Assembling Rapeseed Protein Nanogel for Hydrophobic Curcumin Delivery

Food-dervied biopolymer nanogels have recently received considerable attention as favorable carrier systems for nutraceuticals and drugs. In the present study, new biocompatible and self-assembled acylated rapeseed protein isolate (ARPI)-based nanogels were fabricated for potential hydrophobic drug delivery by chemical acylation and heat-induced protein denaturation. The effects of the ARPI concentration, pH, heat temperature, and heat time on the physiochemical properties of self-assembled ARPI nanogels were investigated. The optimized ARPI nanogels were characterized by a hydrodiameter of 170 nm in size, spherical morphology, and light core-dark shell structure. In comparison to native rapeseed protein isolates and ARPI without the heat treatment, ARPI nanogels as a result of dual acylation and heat processes exhibited significantly altered spatial secondary and tertiary structures, increased surface hydrophobicity, and decreased free sulfhydryl contents of the protein. Such properties endow amphilic ARPI with the self-aggregating ability, resulting in the hydrophobic core with formations of covalent disulfide bonds and the hydrophilic shell with succinyl moieties exposed to the water side. Such a cross-linked structure allowed for ARPI nanogels to be resistant against a broad array of pH and ionic strength as well as lyophilization and dilution. ARPI nanogels demonstrated 95% encapsulation efficiency of hydrophobic compound curcumin and significantly increased its anticancer activity against multiple cancer cell lines.

Non-acylated Wnts Can Promote Signaling

Wnts are a family of 19 extracellular ligands that regulate cell fate, proliferation, and migration during metazoan embryogenesis and throughout adulthood. Wnts are acylated post-translationally at a conserved serine and bind the extracellular cysteine-rich domain (CRD) of Frizzled (FZD) seven-pass transmembrane receptors. Although crystal structures suggest that acylation is essential for Wnt binding to FZDs, we show here that several Wnts can promote signaling in Xenopus laevis and Danio rerio embryos, as well as in an in vitro cell culture model, without acylation. The non-acylated Wnts are expressed at levels similar to wild-type counterparts and retain CRD binding. By contrast, we find that certain other Wnts do require acylation for biological activity in Xenopus embryos, although not necessarily for FZD binding. Our data argue that acylation dependence of Wnt activity is context specific. They further suggest that acylation may underlie aspects of ligand-receptor selectivity and/or control other aspects of Wnt function.

Requirement of Two Acyltransferases for 4- O-Acylation during Biosynthesis of Harzianum A, an Antifungal Trichothecene Produced by Trichoderma arundinaceum

Trichothecenes are sesquiterpenoid toxins produced by multiple fungi, including plant pathogens, entomopathogens, and saprotrophs. Most of these fungi have the acyltransferase-encoding gene tri18. Even though its function has not been determined, tri18 is predicted to be involved in trichothecene biosynthesis because of its pattern of expression and its location near other trichothecene biosynthetic genes. Here, molecular genetic, precursor feeding, and analytical chemistry experiments indicate that in the saprotroph Trichoderma arundinaceum the tri18-encoded acyltransferase (TRI18) and a previously characterized acyltransferase (TRI3) are required for conversion of the trichothecene biosynthetic intermediate trichodermol to harzianum A, an antifungal trichothecene analog with an octa-2,4,6-trienedioyl acyl group. On the basis of the results, we propose that TRI3 catalyzes trichothecene 4- O-acetylation, and subsequently, TRI18 catalyzes replacement of the resulting acetyl group with octa-2,4,6-trienedioyl to form harzianum A. Thus, the findings provide evidence for a previously unrecognized two-step acylation process during trichothecene biosynthesis in T. arundinaceum and possibly other fungi.

Whole-Cell Catalytic Synthesis of Puerarin Monoesters and Analysis of Their Antioxidant Activities

Puerarin, an important isoflavonoid from the edible root of Pueraria lobata, shows multiple bioactivities but suffers from low bioavailability. In this study, a new whole-cell catalytic method for acylation modification of puerarin was developed. Among the 12 strains tested, Aspergillus oryzae showed the highest catalytic activity and selectively catalyzed acylation of puerarin at the 6″-hydroxyl group. The organic solvents used significantly influenced the catalytic efficiency of the cells. In the green solvent 2-methyltetrahydrofuran, the reaction showed high substrate conversion (92.5%) and regioselectivity (95.8%), with results similar to those with tetrahydrofuran (94.2% and 98.5%, respectively) under optimal conditions. The monoester products showed higher liposolubility in comparison to puerarin, and those with C3-C8 fatty acid chain lengths showed evidently improved antioxidant activity toward erythrocyte hemolysis. Considering the operational stability of the cells and efficiency of the scaled-up reactions, this method is efficient and cost effective, with promising applications in the health food industry.

Structure and Catalytic Mechanism of a Bacterial Friedel-Crafts Acylase

C-C bond-forming reactions are key transformations for setting up the carbon frameworks of organic compounds. In this context, Friedel-Crafts acylation is commonly used for the synthesis of aryl ketones, which are common motifs in many fine chemicals and natural products. A bacterial multicomponent acyltransferase from Pseudomonas protegens (PpATase) catalyzes such Friedel-Crafts C-acylation of phenolic substrates in aqueous solution, reaching up to >99 % conversion without the need for CoA-activated reagents. We determined X-ray crystal structures of the native and ligand-bound complexes. This multimeric enzyme consists of three subunits: PhlA, PhlB, and PhlC, arranged in a Phl(A2 C2 )2 B4 composition. The structure of a reaction intermediate obtained from crystals soaked with the natural substrate 1-(2,4,6-trihydroxyphenyl)ethanone together with site-directed mutagenesis studies revealed that only residues from the PhlC subunits are involved in the acyl transfer reaction, with Cys88 very likely playing a significant role during catalysis. These structural and mechanistic insights form the basis of further enzyme engineering efforts directed towards enhancing the substrate scope of this enzyme.

Detection of Heterogeneous Protein S-Acylation in Cells

The use of synthetically synthesized azide and alkyne fatty acid analogs coupled with bioorthogonal Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction-based detection methods to study protein S-acylation reactions has replaced the traditional method of using in vivo metabolic radiolabeling with tritiated palmitic acid and has greatly facilitated our understanding of this essential cellular process. Here, we describe the chemical synthesis of myristic (C:14), palmitic (C16:0), and stearic (C18:0) acid-azide probes and detail how they may be utilized as chemical reporters for the analysis of S-acylation of exogenously expressed proteins in cells.

Direct Analysis of Protein S-Acylation by Mass Spectrometry

Dynamic and reversible protein S-acylation, most commonly occurring as S-palmitoylation, plays an important role in protein/membrane association and the regulation of intracellular signaling via cycles of palmitoylation and depalmitoylation. Direct analysis of protein S-acylation by mass spectrometry (MS) offers several benefits over indirect detection methods in that it can definitively determine the location and nature of the acyl modification, and is not prone to false discoveries. However, characterization of acyl proteins is challenging because of the tendency of acyl loss during sample preparation and tandem MS analysis. In this chapter, we present a sample preparation protocol that preserves labile acyl modifications and an LC-MS/MS workflow for detection of S-acylation with high confidence and sensitivity.

Biochemical Assays for Ghrelin Acylation and Inhibition of Ghrelin O-Acyltransferase

Ghrelin O-acyltransferase (GOAT) is an enzyme responsible for octanoylating and activating ghrelin, a peptide hormone that plays a key role in energy regulation and hunger signaling. Due to its nature as an integral membrane protein, GOAT has yet to be purified in active form which has complicated biochemical and structural studies of GOAT-catalyzed ghrelin acylation. In this chapter, we describe protocols for efficient expression and enrichment of GOAT in insect cell-derived microsomal fraction, HPLC-based assays for GOAT acylation activity employing fluorescently labeled peptides, and assessment of inhibitor potency against GOAT.

S-Acylation of Proteins

Palmitoylation or S-acylation is the posttranslational attachment of fatty acids to cysteine residues and is common among integral and peripheral membrane proteins. Palmitoylated proteins have been found in every eukaryotic cell type examined (yeast, insect, and vertebrate cells), as well as in viruses grown in these cells. The exact functions of protein palmitoylation are not well understood. Intrinsically hydrophilic proteins, especially signaling molecules, are anchored by long-chain fatty acids to the cytoplasmic face of the plasma membrane. Palmitoylation may also promote targeting to membrane subdomains enriched in glycosphingolipids and cholesterol or affect protein-protein interactions.This chapter describes (1) a standard protocol for metabolic labeling of palmitoylated proteins and also the procedures to prove a covalent and ester-type linkage of the fatty acids, (2) a simple method to analyze the fatty acid content of S-acylated proteins, (3) two methods to analyze dynamic palmitoylation for a given protein, and (4) protocols to study cell-free palmitoylation of proteins.

Enantiomeric Variability of Distaminolyne A. Refinement of ECD and NMR Methods for Determining Optical Purity of 1-Amino-2-Alkanols

Sample configurations of distaminolyne A (1a); isolated from the ascidians Pseudodistoma opacum and P. cereum, and collected at different sites in New Zealand, were investigated by two methods: Exciton coupled electronic circular dichroism (EC ECD) of the corresponding N,O-dibenzoyl derivative 1b; and chiral reagent derivatization of 1a with (S)- and (R)-α-methoxyphenylacetic acid (MPA), followed by ¹H-NMR analysis. Configuration and optical purity of 1a (%ee) was found to vary depending on the geographic distribution of ascidian colonies. An improved method for preparing N,O-diarenoyl derivatives of 1a was optimized. The EC ECD method was found to be complementary to the MPA-NMR method at different ranges of %ee.

Acylation of the S413-PV cell-penetrating peptide as a means of enhancing its capacity to mediate nucleic acid delivery: Relevance of peptide/lipid interactions

BACKGROUND

Cell-penetrating peptides (CPPs) have been extensively exploited in gene therapy approaches as vectors for intracellular delivery of bioactive molecules. The ability of CPPs to be internalized into cells and their capacity to complex nucleic acids depend on their molecular structure, both primary and secondary, namely regarding hydrophobicity/hydrophilicity. CPP acylation has been used as a strategy to improve this structural feature.

METHODS

Acyl groups (from 6 to 18 carbon atoms) were attached to the S4₁₃-PV peptide and their effects on the peptide competence to complex siRNAs and to mediate gene silencing in glioblastoma (GBM) cells were studied. A systematic characterization of membrane interactions with S4₁₃-PV acyl-derivatives was also conducted, using different biophysical techniques (surface pressure-area isotherms in Langmuir monolayers, DSC and ³¹P NMR) to unravel a relationship between CPP biological activity and CPP effects on membrane stability and lipid organization.

RESULTS

A remarkable concordance was noticed between acylated-S4₁₃-PV peptide competence to promote gene silencing in GBM cells and disturbance induced in membrane models, the lauroyl- and myristoyl-S4₁₃-PV peptides being the most effective. A cut-off effect was described for the first time regarding the influence of acyl-chain length on CPP bioactivity.

CONCLUSIONS

C12-S4₁₃-PV showed high capacity to destabilize lipid bilayers, to escape from lysosomal degradation and to mediate gene silencing without promoting cytotoxicity.

GENERAL SIGNIFICANCE

Besides unraveling a new CPP with high potential to be employed as a gene delivery vector, this work emphasizes the benefit from allying biophysical and biological studies towards a proper CPP structural refinement for successful pre-clinical/clinical application.