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The human pathogen Staphylococcus aureus is responsible for many community-acquired and hospital-associated infections and is associated with high mortality. Concern over the emergence of multidrug-resistant strains has renewed interest in the elucidation of host mechanisms that defend against S. aureus infection. We recently demonstrated that human serum mannose-binding lectin binds to S. aureus wall teichoic acid (WTA), a cell wall glycopolymer—a discovery that prompted further screening to identify additional serum proteins that recognize S. aureus cell wall components. In this report, we incubated human serum with 10 different S. aureus mutants and determined that serum amyloid P component (SAP) bound specifically to a WTA-deficient S. aureus ΔtagO mutant, but not to tagO-complemented, WTA-expressing cells. Biochemical characterization revealed that SAP recognizes bacterial peptidoglycan as a ligand and that WTA inhibits this interaction. Although SAP binding to peptidoglycan was not observed to induce complement activation, SAP-bound ΔtagO cells were phagocytosed by human polymorphonuclear leukocytes in an FcγR-dependent manner. These results indicate that SAP functions as a host defense factor, similar to other peptidoglycan recognition proteins and nucleotide-binding oligomerization domain–like receptors.

Noninvasive imaging of cancer metastasis through the efficient cell labeling constitutes a major technological breakthrough for cancer research and patient monitoring post-surgery. In the current work, we expanded our cell surface labeling technique on the whole-body fluorescence imaging of tumor metastasis in BALB/c nude mice. Four kinds of human cancer cells (two cancer cell lines, MKN45 and HCT116, and their transfected versions expressing surface glycan-related genes, MKN45-GnT-V and HCT116-GMDS) were labeled by azaelectrocyclization with Hilyte Fluor 750 for 10 min and without affecting cell viability. Fluorescence-labeled cancer cells were injected into the abdominal cavities of BALB/c mice and whole-body scans were performed with an eXplore Optix device. In accordance with previous findings, the fluorescence imaging clearly showed that tumor metastasis was dependent upon the cell surface glycans: A larger polylactosamine structure or the loss of fucosylation on the cancer cell surfaces, respectively, enhanced the metastatic potential of the tumor cells. Our noninvasive technique provides the landmark opportunity for sensitively monitoring the dynamics of the cancer cells depending on their surface structures and/or the host environments, thus impacts on the cancer prognosis and the therapeutic applications.

Fatty acids are essential to natural life because they act as key components in biological membranes and glycerides, as well as in various biologically active agents, such as prostaglandins and endocannabinoids. For the construction of structurally diverse carbon frameworks of fatty acids, transition-metal-catalyzed cross-coupling reactions appear to be the most straightforward and efficient methods for carbon carbon bond formation and they have been employed in the synthesis of a wide variety of fatty acids with unsaturated bonds. However, these methods are limited to reactions at sp or sp carbon atoms, in which the stereochemistry of the olefinic moieties that are being introduced must be controlled. In contrast to these reactions, cross-coupling reactions between sp-hybridized carbon centers appear to be a useful and, potentially, more-promising tool, because they are applicable to the synthesis of both saturated and unsaturated fatty acids and they are free from the problems associated with double-bond stereochemistry. However, owing to the lower tolerance of the carboxylic group toward organometallic reagents, including transition-metal complexes, protected carboxy groups or their synthetic equivalents are often employed. Herein, we report a convenient and efficient one-pot procedure for the construction of carbon frameworks of fatty acids by using the nickelcatalyzed cross-coupling of alkyl halides that contain a carboxy functionality with Grignard reagents in the presence of 1,3-butadiene as an additive, in combination with an in situ protection procedure. As an example of a synthetic application of this method, the regioisomers of elaidic acid were synthesized through an iterative cross-coupling procedure. In our previous studies, we reported that the Ni-catalyzed cross-coupling reactions of alkyl halides with alkyl Grignard reagents in the presence of butadienes were effective for the construction of hydrocarbon skeletons that contained aprotic polar functionalities, such as ketones, esters, and nitriles. When alkyl halides that contained a carboxylic acid group are subjected to this cross-coupling reaction, without employing tedious protection-deprotection processes, the deprotonation of the carboxylic acid group is unavoidable. Thus, to develop a simple and straightforward route to fatty acids with various carbon chains, we examined the Ni-catalyzed cross-coupling reactions of 6-bromohexanoic acid (1a) with excess amounts of nBuMgCl under various conditions and we found that the expected decanoic acid was obtained in quantitative yield as the sole product, with no evidence of any undesirable side reactions, when the reaction was conducted at 0 8C for 1 h in the presence of 2.4 equivalents of nBuMgCl (Scheme 1). In this reaction, a

Positron emission tomography (PET) is a non-invasive method that visualizes the locations and levels of radiotracer accumulation with high imaging contrast. A new labeling method using 6π-electrocyclization was developed for PET and fluorescence labeling. The high reactivity of the new method enabled the labeling of peptides and proteins at low concentration within a short period. PET or fluorescent imaging of the labeled glycoproteins and N-glycan glycoclusters successfully visualized their dynamics and bio-distribution depending on the glycan structures. The trafficking of the lymphocytes was also clearly visualized by the non-invasive fluorescence imaging. The present electrocyclization protocol was also applied to the cell-surface engineering by the oligosaccharides; the lymphocytes introduced with N-glycan successfully targeted the tumor tissue implanted in the nude mice.

Acrolein, a highly toxic α, β–unsaturated aldehyde, has been a longstanding key biomarker associated with a range of disorders related to oxidative stresses. One of the most promising methods for detecting acrolein involves the use of antibodies that can recognize the acrolein–lysine conjugate, 3-formyl-3, 4-dehydropiperidines (FDP), within oxidatively stressed cells and tissues from various disease states. We have uncovered here that FDP could reduce nitroarenes in high yields at 100 °C in the presence of excess CaCl2 as a Lewis acid promoter. This unique transformation allowed for the development of a de novo method for detecting levels of FDPs generated from proteins in urine or blood serum samples. Thus we successfully converted a non-fluorescent and inexpensive 4-nitrophthalonitrile probe to the corresponding fluorescent aniline, thereby constituting the concept of fluorescent switching. Its sensitivity level (0.84 nmol/mL) is more than that of ELISA assays (3.13 nmol/mL) and is already equally reliable and reproducible at this early stage of development. More importantly, this method is cost effective and simple to operate, requiring only mixing of samples with a kit solution. Our method thus possesses potential as a future alternative to the more costly and operatively encumbered conventional antibody-based methods.

Acetobacter pasteurianus is an aerobic Gram-negative rod that is used in the fermentation process used to produce the traditional Japanese black rice vinegar kurozu. Previously, we found that a hydrophobic fraction derived from kurozu stimulates Toll-like receptors to produce cytokines. LPSs, particularly LPS from A. pasteurianus, are strong candidates for the immunostimulatory component of kurozu. The LPS of A. pasteurianus remains stable in acidic conditions during the 2 years of the abovementioned fermentation process. Thus, we hypothesized that its stability results from its structure. In this study, we isolated the LPS produced by A. pasteurianus NBRC 3283 bacterial cells and characterized the structure of its lipid A component. The lipid A moiety was obtained by standard weak acid hydrolysis of the LPS. However, the hydrolysis was incomplete because a certain proportion of the LPS contained acid-stable d-glycero-d-talo-oct-2-ulosonic acid (Ko) residues instead of the acid-labile 3-deoxy-d-manno-oct-2-ulosonic acid residues that are normally found in typical LPS. Even so, we obtained a Ko-substituted lipid A with a novel sugar backbone, α-Man(1-4)[α-Ko(2-6)]β-GlcN3N(1-6)α-GlcN(1-1)α-GlcA. Its reducing end GlcN(1-1)GlcA bond was also found to be quite acid-stable. Six fatty acids were attached to the backbone. Both the whole LPS and the lipid A moiety induced TNF-α production in murine cells via Toll-like receptor 4, although their activity was weaker than those of Escherichia coli LPS and lipid A. These results suggest that the structurally atypical A. pasteurianus lipid A found in this study remains stable and, hence, retains its immunostimulatory activity during acetic acid fermentation.

A bio-inspired cascade reaction has been developed for the construction of the marine natural product ageladine A and a de novo array of its N1-substituted derivatives. This cascade features a 2-aminoimidazole formation that is modeled after an arginine post-translational modification and an aza-electrocyclization. It can be effectively carried out in a one-pot procedure from simple anilines or guanidines, leading to structural analogues of ageladine A that had been otherwise synthetically inaccessible. We found that some compounds out of this structurally novel library show a significant activity in modulating the neural differentiation. Namely, these compounds selectively activate or inhibit the differentiation of neural stem cells to neurons, while being negligible in the differentiation to astrocytes. This study represents a successful case in which the native biofunction of a natural product could be altered by structural modifications.

We have elucidated the cooperative stabilization of proteins by sugars, amino acids, and other protein-stabilizing agents using a new and simple assay system. Our system determines the protein-stabilizing ability of various compounds by measuring their ability to protect hemoglobin from denaturation. Hemoglobin denaturation was readily measured by quantitative changes in its ultraviolet–visible absorption spectrum. The efficiency of our assay was confirmed using various sugars such as trehalose and sucrose that are known to be good protein stabilizers. We have also found that mixtures of two different types of protein stabilizers resulted in a cooperative stabilizing effect on protein.

Formal [4+4] reaction of the unsaturated benzyl- or allylimines, which is efficiently mediated by primary amine, provides the 2,6,9-triazabicyclo[3.3.1]nonane derivatives. Variously substituted homo- and hetero-coupling products are obtained in good to excellent yields by quite a simple procedure under mild conditions: by mixing the unsaturated aldehydes with the amines at room temperature.

Lipopolysaccharide (LPS), also known as endotoxin, activates the innate immune response through toll-like receptor 4 (TLR4) and its coreceptor, MD-2. MD-2 has a unique hydrophobic cavity that directly binds to lipid A, the active center of LPS. Tetraacylated lipid IVa, a synthetic lipid A precursor, acts as a weak agonist to mouse TLR4/MD-2, but as an antagonist to human TLR4/MD-2. However, it remains unclear as to how LPS and lipid IVa show agonistic or antagonistic activities in a species-specific manner. The present study reports the crystal structures of mouse TLR4/MD-2/LPS and TLR4/MD-2/lipid IVa complexes at 2.5 and 2.7 Å resolutions, respectively. Mouse TLR4/MD-2/LPS exhibited an agonistic “m”-shaped 2:2:2 complex similar to the human TLR4/MD-2/LPS complex. Mouse TLR4/MD-2/lipid IVa complex also showed an agonistic structural feature, exhibiting architecture similar to the 2:2:2 complex. Remarkably, lipid IVa in the mouse TLR4/MD-2 complex occupied nearly the same space as LPS, although lipid IVa lacked the two acyl chains. Human MD-2 binds lipid IVa in an antagonistic manner completely differently from the way mouse MD-2 does. Together, the results provide structural evidence of the agonistic property of lipid IVa on mouse TLR4/MD-2 and deepen understanding of the ligand binding and dimerization mechanism by the structurally diverse LPS variants.

WaaA is a key enzyme in the biosynthesis of LPS, a critical component of the outer envelope of Gram-negative bacteria. Embedded in the cytoplasmic face of the inner membrane, WaaA catalyzes the transfer of 3-deoxy- d - manno -oct-2-ulosonic acid (Kdo) to the lipid A precursor of LPS. Here we present crystal structures of the free and CMP-bound forms of WaaA from Aquifex aeolicus , an ancient Gram-negative hyperthermophile. These structures reveal details of the CMP-binding site and implicate a unique sequence motif (GGS/TX 5 GXNXLE) in Kdo binding. In addition, a cluster of highly conserved amino acid residues was identified which represents the potential membrane-attachment and acceptor-substrate binding site of WaaA. A series of site-directed mutagenesis experiments revealed critical roles for glycine 30 and glutamate 31 in Kdo transfer. Our results provide the structural basis of a critical reaction in LPS biosynthesis and allowed the development of a detailed model of the catalytic mechanism of WaaA.

Derivatization of ursolic acid, one of the natural ursene-type pentacyclic triterpenes, was investigated by the oxidation with dioxoruthenium(VI) tetraphenylporphyrins. Oxidation selectivity on the terpene structure was modulated by the auxiliaries introduced on the tetraphenylporphyrin. Chemical oxidation of the ursolic acid affected the cytotoxic activity against tumor cell lines.

A new synthetic strategy for obtaining artificial receptors that selectively regulate and/or control specific protein/protein interactions was developed based on the template-assisted and the self-activating click reaction applied to a combinatorial library. Synthetic mimics of the Grb2-SH2 domain, examined as a model case, selectively bound to a target signaling protein to induce cytotoxicity and inhibit tumor growth in vivo.

Immunostimulating glycoconjugates from bacteria were synthesized for elucidation of the recognition with innate immune receptors. Synthesis of partial structures and analogues of lipopolysaccharide and its bioactive principle ‘lipid A’ contributed the elucidation of mode of action, i.e., interaction of lipopolysaccharide with its receptor ‘TLR4/MD-2 complex’. Immunomodulation by parasitic bacteria ‘Helicobacter pylori’ was elucidated by using synthetic lipopolysaccharide partial structures. Intracellular peptidoglycan receptors, ‘Nod1’ and ‘Nod2’, and their ligand structures were identified by using synthetic peptidoglycan partial structures. New Nod1 ligands were identified from the bacterial supernatant. In vivo function of Nod1 was studied by using synthetic ligands found from small library of Nod1 ligands.

Helicobacter pylori is a common cause of gastroduodenal inflammatory diseases such as chronic gastritis and peptic ulcers and also an important factor in gastric carcinogenesis. Recent reports have demonstrated that bacterial inflammatory processes, such as stimulation with H. pylori lipopolysaccharide (LPS), initiate atherosclerosis. To establish the structures responsible for the inflammatory response of H. pylori LPS, we synthesized various kinds of lipid A structures (i.e., triacylated lipid A and Kdo-lipid A compounds), with or without the ethanolamine group at the 1-phosphate moiety, by a new divergent synthetic route. Stereoselective α-glycosylation of Kdo N-phenyltrifluoroacetimidate was achieved by use of microfluidic methods. None of the lipid A and Kdo-lipid A compounds were a strong inducer of IL-1β, IL-6, or IL-8, suggesting that H. pylori LPS is unable to induce acute inflammation. In fact, the lipid A and Kdo-lipid A compounds showed antagonistic activity against cytokine induction by E. coli LPS, except for the lipid A compound with the ethanolamine group, which showed very weak agonistic activity. On the other hand, these H. pylori LPS partial structures showed potent IL-18- and IL-12-inducing activities. IL-18 has been shown to correlate with chronic inflammation, so H. pylori LPS might be implicated in the chronic inflammatory responses induced by H. pylori. These results also indicated that H. pylori LPS can modulate the immune response: NF-κB activation through hTLR4/MD-2 was suppressed, whereas production of IL-18 and IL-12 was promoted.

Ursene-type pentacyclic triterpenes, including the ursolic acid, corosolic acid, and a new ursene-type pentacyclic triterpene, 7,24-dihydroxy ursolic acid, were isolated from the methanolic extract of the leaves of the Bangladeshi medicinal plant, Saurauja roxburghii, a higher plant indigenous to South East Asia and some part of North America. They were tested for the cytotoxicity against C6 rat glioma and A431 human epidermoid carcinoma cell lines. Although they have the same ursene-type pentacyclic triterpene core structure, the position and numbers of hydroxyl groups on the terpene structure significantly affected the activity and the selectivity to the cell lines.

Objective— The goal of this study was to investigate the effects of stimulants for a nucleotide-binding domain, leucine-rich repeat-containing (NLR) protein family on human artery endothelial cells and murine arteries. Methods and Results— Human coronary artery endothelial cells were challenged in vitro with microbial components that stimulate NLRs or Toll-like receptors. We found stimulatory effects of NLR and Toll-like receptor ligands on the adhesion molecule expression and cytokine secretion by human coronary artery endothelial cells. On the basis of these results, we examined the in vivo effects of these ligands in mice. Among them, FK565, 1 of the nucleotide-binding oligomerization domain (Nod)-1 ligands induced strong site-specific inflammation in the aortic root. Furthermore, coronary arteritis/valvulitis developed after direct oral administration or ad libitum drinking of FK565. The degree of the respective vascular inflammation was associated with persistent high expression of proinflammatory chemokine/cytokine and matrix metallopeptidase ( Mmp ) genes in each tissue in vivo by microarray analysis. Conclusion— This is the first coronary arteritis animal model induced by oral administration of a pure synthetic Nod1 ligand. The present study has demonstrated an unexpected role of Nod1 in the development of site-specific vascular inflammation, especially coronary arteritis. These findings might lead to the clarification of the pathogenesis and pathophysiology of coronary artery disease in humans.

Bacteria release immunostimulatory compounds to the environment, and one of the stimulants is the ligand of nucleotide-binding oligomerization domain protein 1 (Nod1), an intracellular protein involved in the recognition of the bacterial component peptidoglycans having a diaminopimelic acid (DAP) structure. The polymorphisms of Nod1 have been linked to several inflammatory diseases and allergies that are strongly affected by environmental factors. The present paper summarizes recent results on the isolation and structural elucidation of natural human Nod1 (hNod1) ligands from the Escherichia coli (E. coli) K-12 culture supernatant, the first chemical synthesis of these natural ligands and related PGN fragments structures, and the hNod1 stimulatory activities of the chemically synthesized DAP-type PGN fragments. For structural characterization studies, the 7-(diethylamino)coumarin-3-carbonyl (DEAC) labeling method was also used to enhance the sensitivity in mass spectrometry studies, in order to observe PGN fragments in a comprehensive manner. The results suggest that DAP-containing bacteria release certain hNod1 ligands to the environment and that these ligands accumulate in the environment and regulate the immune system through Nod1.

Bacterial cell wall peptidoglycan (PGN) is a major innate immunostimulant of bacteria and an important antibiotic target. Chemically prepared PGN fragments are indispensable for the investigation o...

In(OTf)3 efficiently activated N-phenyltrifluoroacetimidate and In(OTf)3 in combination with various halogenated reagents or PhIO promoted glycosylation using thioglycoside in good yields. The comb...

The N-Troc (2,2,2-trichloroethoxycarbonyl) groups in glucosamine and muramic acid derivatives were removed by treatment with tetrabutylammonium fluoride (TBAF) under mild conditions. The use of Troc protection for the amino group in aminosugars such as glucosamine is increasing the importance for selective and efficient glycosylation, and the cleavage method described here will expand the available opportunities for using the Troc group in the preparation of a variety of glycans. This cleavage is especially advantageous for compounds that are labile or may be decomposed under acidic conditions, strong basic conditions, or reductive conditions.

Nucleotide-binding oligomerization domain protein 1 (Nod1) is an intracellular protein involved in recognition of the bacterial component peptidoglycan. This recognition event induces a host defense response to eliminate invading pathogens. The genetic variation of Nod1 has been linked to several inflammatory diseases and allergies, which are strongly affected by environmental factors. We have found that many of the bacteria that contain DAP-type peptidoglycan release Nod1 ligands into the environment. However, the structures of natural Nod1 ligands in the environment are not well understood. Herein, we report the isolation and structural elucidation of natural human Nod1 (hNod1) ligands from the Escherichia coli K-12 culture supernatant. The supernatant was fractionated with reversed-phase high performance liquid chromatography (RP-HPLC), resulting in the isolation of several hNod1 stimulatory fractions. Structural characterization studies demonstrated that the molecular structure of the most active fraction was the native hNod1 ligand GlcNAc-(beta1-4)-(anhydro)MurNAc-l-Ala-gamma-d-Glu-meso-DAP. We also found other peptidoglycan fragments using the 7-(diethylamino)coumarin-3-carbonyl labeling method to enhance sensitivity in mass spectroscopy studies. These results suggested that DAP-containing bacteria release certain hNod1 ligands to the environment, and these ligands would accumulate in the environment and regulate the immune system through Nod1.

Synthesis and clusterization of Galβ(1→3)[NeuAcα(2→6)]GlcNAcβ(1→2)Man motif of the N -glycan, as the molecular probes for their biological evaluation, are reported. Key step is the quantitative and the completely α-selective sialylation of the C5-azide N -phenyltrifluoroacetimidate with the disaccharide acceptor, Galβ(1→3)GlcNTroc. Clusterization of the 16 molecules of trisaccharide motif was also achieved by the ‘self-activating click reaction’. These probes could efficiently be labeled by biotin and/or other fluorescence- or radioactive reporter groups through either cross metathesis, acylation, Cu(I)-mediated Huisgen [2+3]-cycloaddition, or the azaelectrocyclization to utilize the various biological techniques.

Graphical Abstract Combined azaelectrocyclization and Staudinger ligation allowed proteins and living cells to be modified by small molecules (i.e., biotin or N-glycans). Chemically engineered lymphocytes modified by complex-type N-glycan targeted DLD-1 tissues implanted in nude mice at the whole-body level.

L-Propargylglycine was efficiently labeled with 14C at the 1- and 2- positions. The synthesis was achieved according to the scheme illustrated in Fig.1. Ni-complex of Schiff's base, Gly-Ni-BPB(4) was derived from [U-14C]glycine(2) and (S)-BPB(3). Diastereoselective alkylation of 4 with propargyl bromide followed by acid hydrolysis afforded L-propargyl[1, 2-14C]glycine(1). The optical purity of 1was proved to be 97.0% and the overall yield of 1 from 2 was 28.2%.

An efficient one-pot synthetic procedure for the synthesis of 2,4-disubstituted pyridines has been successfully established. The method proceeds through a 6pi-azaelectrocyclization-aromatization sequence. Using this method, a wide variety of pyridine structures substituted at the 2-position have been rapidly constructed from vinyl stannanes, vinyl iodide, sulfonamide, and a palladium catalyst. The method was further applied to the solid-phase synthesis wherein the use of a "traceless" sulfonamide linker enabled the rapid preparation of a small library of pyridines with high purity, without any chromatographic separation.

Continuous flow synthesis for bioactive natural products is described. Efficient procedures using the microfluidic system were developed for the large-scale synthesis of important synthetic units of asparagine-linked oligosaccharide in glycoprotein. Advantageous aspects of microfluidic conditions, i.e., efficient mixing, fast heat transfer, and residence time control led to cation-mediated reactions, such as α-sialylation, β-mannosylation, and reductive opening of the benzylidene acetal groups in high yields. Microfluidic dehydration was developed for the industrial-scale synthesis of the immunostimulating natural terpenoid, pristane. The base-mediated aldol condensation in an aqueous biphasic system enabled the multigram synthesis of β-hydroxyketones in high yields.

In this Letter, a new synthetic method of sulfonamide-containing cyclic sulfides using a microwave-assisted traceless solid-phase approach is described. Using this new method, many highly pure cyclic sulfides were efficiently synthesized based on intramolecular alkylation of the sulfides followed by elimination of the desired products from the generated sulfonium salts.

The synthesis of crosslinked peptidoglycan (PGN) fragments from Streptococcus pneumoniae cell wall was achieved. The immunostimulatory activities, including the induction of IL-6 and the stimulation of the intracellular receptor Nod2, were also determined. The crosslinked PGN fragments were not major human Nod2 ligands.

An integrated microfluidic/batch system was applied to the chemical N-glycosylation by the asparagine amide group, a key glycosyl bond-formation reaction in the synthesis of N-glycopeptides. By applying the advantageous features of microfluidic conditions, that is, efficient mixing and rapid heat transfer, the GlcNTrocβAsn and the Fuca(1―6)GlcNTrocβAsn fragments were efficiently prepared.

Staphylococcus aureus is known to activate mammalian immune cells through Toll-like receptor 2 (TLR2). We recently demonstrated that a lipoprotein fraction obtained from S. aureus by Triton X-114 phase partitioning is a potent activator of TLR2. In this study, we separated TLR2-activating lipoproteins expressed in S. aureus and characterized an N-terminal structure. The lipoprotein fraction of S. aureus was prepared by glass bead disruption followed by Triton X-114 phase partitioning. The TLR2-activating molecules were mainly detected in the mass range of 30–35 kDa. Seven lipoproteins were identified by the mass spectra of their tryptic digests. Among them, three lipoproteins were separated by preparative SDS-PAGE and proved to activate TLR2. After digestion with trypsin in the presence of sodium deoxycholate, the N terminus of the lipopeptide was isolated from lipoprotein SAOUHSC_02699 by normal phase high pressure liquid chromatography and characterized as an S-(diacyloxypropyl)cystein-containing peptide using tandem mass spectra. The synthetic lipopeptide counterpart also stimulated the cells via TLR2. These results showed that the diacylated lipoprotein from S. aureus acts as a TLR2 ligand in mammalian cells.

Combined microfluidic/batch conditions were applied to β-mannosylation, a key glycosylation for the synthesis of the Manβ(1-4)GlcNAc motif in N-glycan structures. By applying the advantageous features of microfluidic conditions (i.e., efficient mixing and fast heat transfer), the Manβ(1-4)GlcNTroc fragment was practically and reproducibly synthesized on the gram scale.

Bacterial cell wall peptidoglycan (PGN) is a potent immunostimulator and immune adjuvant. The PGN of Gram-negative bacteria and some Gram-positive bacteria contain meso-diaminopimelic acid (meso-DAP), and we have recently shown that the intracellular protein Nod1 is a PGN receptor and recognizes DAP-containing peptides. In this study, we achieved the synthesis of DAP-containing PGN fragments, including the first chemical synthesis of tracheal cytotoxin (TCT), GlcNAc-(beta1-4)-(anhydro)MurNAc-L-Ala-gamma-D-Glu-meso-DAP-D-Ala, and a repeating-unit of DAP-type PGN, GlcNAc-(beta1-4)-MurNAc-L-Ala-gamma-D-Glu-meso-DAP-D-Ala. For the synthesis of PGN fragments, we first established a new synthetic method for an orthogonally protected meso-DAP derivative, and then we constructed the glycopeptide structures. The ability of these fragments to stimulate human Nod1, as well as differences in Nod1 recognition of the variety of synthesized ligand structures were examined. The results showed that the substitution of the N terminus of iE-DAP is necessary for stronger Nod1 recognition, but the structure of the substituent seems not to be strictly recognized. The importance of the carboxyl group at the 2-position of DAP for human Nod1 stimulation was also shown.

Nod2 is an intracellular innate immune receptor that plays a role in host defense and susceptibility to inflammatory disease. We show in this study that macrophages rendered refractory to TLR4 and Nod2 signaling by exposure to LPS and muramyl dipeptide (MDP) exhibit impaired TNF-α and IL-6 production in response to pathogenic Listeria monocytogenes and Yersinia pseudotuberculosis as well as commensal bacteria including Escherichia coli and Bacteroides fragilis. Surprisingly, Nod2 deficiency was associated with impaired tolerization in response to pathogenic and commensal bacteria. Mechanistically, reduced tolerization of Nod2-null macrophages was mediated by recognition of bacteria through Nod1 because it was abolished in macrophages deficient in Nod1 and Nod2. Consistently, Nod2-null macrophages tolerant to LPS and MDP showed enhanced production of TNF-α and IL-6 as well as increased NF-κB and MAPK activation in response to the dipeptide KF1B, the Nod1 agonist. Furthermore, reduced tolerization of Nod2-deficient macrophages in response to bacteria was abolished when mutant macrophages were also rendered tolerant to the Nod1 ligand. Finally, MDP stimulation induced refractoriness not only to MDP, but also to iE-DAP stimulation, providing a mechanism to explain the reduced tolerization of Nod2-deficient macrophages infected with bacteria. These results demonstrate that cross-tolerization between Nod1 and Nod2 leads to increase recognition of both pathogenic and commensal bacteria in Nod2-deficient macrophages pre-exposed to microbial ligands.

To elucidate the structural requirements for the endotoxic and antagonistic activities of lipid A derivatives, we have focused on the effects of the acyl moieties and acidic groups at the 1- and 4′...

Autophagy, an evolutionally conserved homeostatic process for catabolizing cytoplasmic components, has been linked to the elimination of intracellular pathogens during mammalian innate immune responses. However, the mechanisms underlying cytoplasmic infection-induced autophagy and the function of autophagy in host survival after infection with intracellular pathogens remain unknown. Here we report that in drosophila, recognition of diaminopimelic acid-type peptidoglycan by the pattern-recognition receptor PGRP-LE was crucial for the induction of autophagy and that autophagy prevented the intracellular growth of Listeria monocytogenes and promoted host survival after this infection. Autophagy induction occurred independently of the Toll and IMD innate signaling pathways. Our findings define a pathway leading from the intracellular pattern-recognition receptors to the induction of autophagy to host defense.

In this study, we isolated a complementary DNA encoding nucleotide-binding oligomerization domain-1 (NOD1) from Peyer's patches (Pps) of swine gut-associated lymphoid tissues (GALT). The complete open reading frame of porcine NOD1 contains 2862 bp, encoding a 953-amino acid polypeptide. The porcine NOD1 amino acid sequence is more closely related to the human sequence (83.8% identity) than the mouse counterpart (79.2% identity). To examine the subcellular expression and function of porcine NOD1, we overexpressed it in human embryonic kidney 293 cells. Immunostaining with an anti-porcine NOD1 polyclonal antibody revealed that the protein was expressed in transfectants as an intracellular membrane-bound molecule. In the transfected cells, both gamma-d-glutamyl-meso-diaminopimelic acid, and meso-diaminopimelic acid and meso-lanthionine activated nuclear factor-kappa B. Quantitative real-time PCR detected NOD1 mRNA in multiple tissues isolated from adult and newborn swine, including the esophagus, duodenum, jejunum, ileum, ileal Pps, colon, spleen, and mesenteric lymph nodes. In the newborn and adults, NOD1 was highly expressed in the esophagus and GALT, such in the ileal Pps and mesenteric lymph nodes. Furthermore, Toll-like receptor and NOD1 ligands as well as immunobiotic lactic acid bacteria enhanced the expression of NOD1 in GALT of adult and newborn swine. Our results should help clarify how the intestinal immune system is modulated by low-molecular weight peptidoglycan fragments through NOD1.

Highly α‐selective sialylation of sialic acid N‐phenyltrifluoroacetimidate with various galactose and lactose acceptors has been achieved by introducing the C‐5 N‐phthalyl group on the donor. The “fixed dipole effect” of the N‐phthalyl group was proposed to explain the high reactivity and α‐selectivity. The microfluidic system was applied to the present α‐sialylation, which is amenable to large‐scale synthesis. The N‐phthalyl group was removed by treatment with methylhydrazine acetate, for which protocol can be readily applied to the synthesis of a variety of sialic acid‐containing oligosaccharides.

The synthesis of immunoregulatory glycoconjugates, namely the active entity of lipopolysaccharide (LPS) from Helicobacter pylori was achieved. The results of biological activities of the LPS partial structures provide the structural basis for the immunobiological activity, especially for the immune inhibitory activity of H. pylori LPS.

Acceleration of Cu(I)-mediated Huisgen 1,3-dipolar cycloaddition (Sharpless ‘click reaction’) by non-basic histidine derivatives was found. An efficient ‘self-activating’ click reaction between the azide- and acetylene-containing peptides on the solid-phase has also been achieved by introducing the N im -benzylhistidine residue on the reacting peptides.

Partial structures of peptidoglycan were chemically synthesized for elucidation of their precise biological activities. By using an efficient synthetic strategy, mono-, di-, tetra- and octasaccharide fragments of peptidoglycan were synthesized in good yields. The biological activity of synthetic fragments of peptidoglycan was evaluated by induction of TNF-α from human monocytes, and TLR2 and NOD2 dependencies by using transfected HEK293 cells, respectively. We revealed that TLR2 was not stimulated by the series of synthetic peptidoglycan partial structures, whereas NOD2 recognizes the partial structures containing the MDP moiety. We also synthesized potent NOD1 agonists, which showed several hundred-fold stronger activity than γ-D-glutamyl- meso-diaminopimelic acid (iE-DAP). Interaction of PGRPs with synthetic peptidoglycan fragments is also described.