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Natural Science 05/2013; 5(5).
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Yuji Kondo,
Kazutaka Ikeda,
Noriyo Tokuda,
Chiaki Nishitani,
Umeharu Ohto,
Sachiko Akashi-Takamura,
Yasutomo Ito,
Makoto Uchikawa, Yoshio Kuroki,
Ryo Taguchi,
Kensuke Miyake,
Qing Zhang,
Keiko Furukawa,
Koichi Furukawa
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ABSTRACT: Although endogenous ligands for Toll-like receptor (TLR)4-myeloid differentiation factor 2 (MD2) have not been well-understood, we here report that a globo-series glycosphingolipid, globotetraosylceramide (Gb4), attenuates the toxicity of lipopolysaccharides (LPSs) by binding to TLR4-MD-2. Because α1,4-galactosyltransferase (A4galt)-deficient mice lacking globo-series glycosphingolipids showed higher sensitivity to LPS than wild-type mice, we examined mechanisms by which globo-series glycosphingolipids attenuate LPS toxicity. Cultured endothelial cells lacking A4galt showed higher expression of LPS-inducible genes upon LPS treatment. In turn, introduction of A4galt cDNA resulted in the neo expression of Gb4, leading to the reduced expression of LPS-inducible genes. Exogenous Gb4 induced similar effects. As a mechanism for the suppressive effects of Gb4 on LPS signals, specific binding of Gb4 to the LPS receptor TLR4-MD-2 was demonstrated by coprecipitation of Gb4 with recombinant MD-2 and by native PAGE. A docking model also supported these data. Taken together with colocalization of TLR4-MD-2 with Gb4 in lipid rafts after LPS stimulation, it was suggested that Gb4 competes with LPS for binding to TLR4-MD-2. Finally, administration of Gb4 significantly protected mice from LPS-elicited mortality. These results suggest that Gb4 is an endogenous ligand for TLR4-MD-2 and is capable of attenuating LPS toxicity, indicating the possibility for its therapeutic application in endotoxin shock.
Proceedings of the National Academy of Sciences 03/2013; · 9.68 Impact Factor
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ABSTRACT: The adherence of uropathogenic Escherichia coli (UPEC) to the host urothelial surface is the first step for establishing UPEC infection. Uroplakin Ia (UPIa), a glycoprotein expressed on bladder urothelium, serves as a receptor for FimH, a lectin located at bacterial pili, and their interaction initiates UPEC infection. Surfactant protein D (SP-D) is known to be expressed on mucosal surfaces in various tissues besides the lung. However, the functions of SP-D in the non-pulmonary tissues are poorly understood. The purposes of this study were to investigate the possible function of SP-D expressed in the bladder urothelium and the mechanisms by which SP-D functions. SP-D was expressed in human bladder mucosa and its mRNA was increased in the bladder of the UPEC infection model in mice. SP-D directly bound to UPEC and strongly agglutinated them in a Ca2+-dependent manner. Co-incubation of SP-D with UPEC decreased the bacterial adherence to 5637 cells, the human bladder cell line, and the UPEC-induced cytotoxicity. In addition, pre-incubation of SP-D with 5637 cells resulted in the decreased adherence of UPEC to the cells and in the reduced number of the cells injured by UPEC. SP-D directly bound to UPIa and competed with FimH for UPIa binding. Consistent with the in vitro data, the exogenous administration of SP-D inhibited UPEC adherence to the bladder and dampened UPEC-induced inflammation in mice. These results support the conclusion that SP-D can protect the bladder urothelium against UPEC infection, and suggest a possible function of SP-D in urinary tract.
Journal of Biological Chemistry 09/2012; · 4.77 Impact Factor
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Motoko Takahashi,
Satoshi Miyata,
Junichi Fujii,
Yoko Inai,
Shigemitsu Ueyama,
Motoko Araki,
Tomoyoshi Soga,
Reiko Fujinawa,
Chiaki Nishitani,
Shigeru Ariki,
Takeyuki Shimizu,
Tomomi Abe,
Yoshito Ihara,
Morimitsu Nishikimi,
Yasunori Kozutsumi,
Naoyuki Taniguchi, Yoshio Kuroki
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ABSTRACT: Aldehyde reductase (AKR1A; EC 1.1.1.2) catalyzes the reduction of various types of aldehydes. To ascertain the physiological role of AKR1A, we examined AKR1A knockout mice.
Ascorbic acid concentrations in AKR1A knockout mice tissues were examined, and the effects of human AKR1A transgene were analyzed. We purified AKR1A and studied the activities of glucuronate reductase and glucuronolactone reductase, which are involved in ascorbic acid biosynthesis. Metabolomic analysis and DNA microarray analysis were performed for a comprehensive study of AKR1A knockout mice.
The levels of ascorbic acid in tissues of AKR1A knockout mice were significantly decreased which were completely restored by human AKR1A transgene. The activities of glucuronate reductase and glucuronolactone reductase, which are involved in ascorbic acid biosynthesis, were suppressed in AKR1A knockout mice. The accumulation of d-glucuronic acid and saccharate in knockout mice tissue and the expression of acute-phase proteins such as serum amyloid A2 are significantly increased in knockout mice liver.
AKR1A plays a predominant role in the reduction of both d-glucuronic acid and d-glucurono-γ-lactone in vivo. The knockout of AKR1A in mice results in accumulation of d-glucuronic acid and saccharate as well as a deficiency of ascorbic acid, and also leads to upregulation of acute phase proteins.
AKR1A is a major enzyme that catalyzes the reduction of d-glucuronic acid and d-glucurono-γ-lactone in vivo, besides acting as an aldehyde-detoxification enzyme. Suppression of AKR1A by inhibitors, which are used to prevent diabetic complications, may lead to the accumulation of d-glucuronic acid and saccharate.
Biochimica et Biophysica Acta 07/2012; 1820(11):1787-96. · 4.66 Impact Factor
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ABSTRACT: We propose two antigenic types of Helicobacter pylori lipopolysaccharides (LPS): highly antigenic epitope-carrying LPS (HA-LPS) and weakly antigenic epitope-carrying LPS (WA-LPS) based on human serum reactivity. Strains carrying WA-LPS are highly prevalent in isolates from gastric cancer patients. WA-LPS exhibits more potent biological activities compared to HA-LPS, namely, upregulation of Toll-like receptor 4 (TLR4) expression and induction of enhanced epithelial cell proliferation. The results of competitive binding assays using monosaccharides and methylglycosides, as well as binding assays using glycosidase-treated LPS, suggested that β-linked N-acetyl-D-glucosamine and β-linked D-galactose residues largely contributed to the highly antigenic epitope and the weakly antigenic epitope, respectively. WA-LPS exhibited greater binding activity to surfactant protein D (SP-D) in a Ca(2+)-dependent manner, and this interaction was inhibited by methyl-β-D-galactoside. The biological activities of WA-LPS were markedly enhanced by the addition of SP-D. Lines of evidence suggested that removal of β-N-acetyl-D-glucosamine residue, which comprises the highly antigenic epitope, results in exposure of the weakly antigenic epitope. The weakly antigenic epitope interacted preferentially with SP-D, and SP-D enhanced the biological activity of WA-LPS.
Infection and immunity 05/2012; 80(8):2956-62. · 4.21 Impact Factor
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ABSTRACT: Toll-like receptors (TLRs) that initiate an innate immune response contain an extracellular leucine rich repeat (LRR) domain and an intracellular Toll IL-receptor (TIR) domain. There are fifteen different TLRs in vertebrates. The LRR domains, which adopt a solenoid structure, usually have higher rates of evolution than do the TIR globular domains. It is important to understand the molecular evolution and functional roles of TLRs from this standpoint. Both pairwise genetic distances and Ka/Ks's (the ratios between non synonymous and synonymous substitution rates) were compared between the LRR domain and the TIR domain of 366 vertebrate TLRs from 96 species (from fish to primates). In fourteen members (TLRs 1, 2, 3, 4, 5, 6, 7, 8, 9, 11/12, 13, 14, 21, and 22/23) the LRR domains evolved significantly more rapidly than did the corresponding TIR domains. The evolutionary rates of the LRR domains are significantly different among these members; LRR domains from TLR3 and TLR7 from primates to fishes have the lowest rate of evolution. In contrast, the fifteenth member, TLR10, shows no significant differences; its TIR domain is not highly conserved. The present results suggest that TLR10 may have a different function in signaling from those other members and that a higher conservation of TLR3 and TLR7 may reflect a more ancient mechanism and/or structure in the innate immune response system. Gene conversions are suggested to have occurred in platypus TLR6 and TLR10. This study provides new insight about structural and functional diversification of vertebrate TLRs.
Gene 04/2012; 503(2):235-43. · 2.34 Impact Factor
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Atsushi Saito,
Shigeru Ariki,
Hitoshi Sohma,
Chiaki Nishitani,
Kanako Inoue,
Nobutaka Ebata,
Motoko Takahashi,
Yoshihiro Hasegawa,
Koji Kuronuma,
Hiroki Takahashi, Yoshio Kuroki
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ABSTRACT: Defensins are important molecules in the innate immune system that eliminate infectious microbes. They also exhibit cytotoxicity against host cells in higher concentrations. The mechanisms by which hosts protect their own cells from cytotoxicity of defensins have been poorly understood. We found that the cytotoxicity of human β-defensin 3 (hBD3) against lung epithelial cells was dose-dependently attenuated by pulmonary surfactant protein A (SP-A), a collectin implicated in host defense and regulation of inflammatory responses in the lung. The direct interaction between SP-A and hBD3 may be an important factor in decreasing this cytotoxicity because preincubation of epithelial cells with SP-A did not affect the cytotoxicity. Consistent with in vitro analysis, intratracheal administration of hBD3 to SP-A(-/-) mice resulted in more severe tissue damage compared with that in WT mice. These data indicate that SP-A protects lung epithelium from tissue injury caused by hBD3. Furthermore, we found that the functional region of SP-A lies within Tyr(161)-Lys(201). Synthetic peptide corresponding to this region, tentatively called SP-A Y161-G200, also inhibited cytotoxicity of hBD3 in a dose-dependent manner. The SP-A Y161-G200 is a candidate as a therapeutic reagent that prevents tissue injury during inflammation.
Journal of Biological Chemistry 03/2012; 287(18):15034-43. · 4.77 Impact Factor
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ABSTRACT: Pulmonary surfactant is a mixture of lipids and proteins that covers alveolar surfaces and keeps alveoli from collapsing. Four specific proteins have been identified in surfactant. Among them, two C-type lectins, surfactant proteins A and D (SP-A and SP-D), are known to be implicated in host defense and regulation of inflammatory responses of the lung. These host defense lectins are structurally characterized by N-terminal collagen-like domains and lectin domains and are called pulmonary collectins. They prevent dissemination of infectious microbes by their biological activities including agglutination and growth inhibition. They also promote clearance of microbes by enhancing phagocytosis in macrophages. In addition, they interact with the other pattern-recognition molecules, including Toll-like receptors (TLRs) and TLR-associated molecules, CD14 and MD-2, and regulate inflammatory responses. Furthermore, recent studies have demonstrated that these collectins modulate functions of neutrophil-derived innate immune molecules by interacting with them. These findings indicate that pulmonary collectins play critical roles in host defense of the lung.
Journal of Biomedicine and Biotechnology 01/2012; 2012:532071. · 2.44 Impact Factor
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ABSTRACT: Hepatitis C virus (HCV) chronic infection is characterized by low-level or undetectable cellular immune response against HCV antigens. HCV proteins affect various intracellular events and modulate immune responses, although the mechanisms that mediate these effects are not fully understood. In this study, we examined the effect of HCV proteins on the differentiation of human peripheral blood monocytes to dendritic cells (DCs). The HCV core (HCVc) and non-structural 3 (NS3) proteins inhibited the expression of CD1a, CD1b and DC-SIGN during monocyte differentiation to DCs, while increasing some markers characteristic of macrophages (CD14 and HLA-DR) and also PD-L1 expression. Meanwhile, HCVc and NS3 could induce differentiating monocytes to secrete IL-10. However, anti-IL-10 mAb could not reverse HCVc and NS3 inhibition of monocyte differentiation into DCs. The HCVc and NS3 proteins increased IL-6 secretion both in immature and in fully differentiated DCs and also promoted CD4+ T-cell IL-17 production. Since T(h) 17 cells are active in many examples of immunopathology, these effects may contribute to HCV autoimmune responses in chronically infected patients.
International Immunology 12/2011; 24(2):97-106. · 3.41 Impact Factor
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Shigeru Ariki,
Takashi Kojima,
Shinsei Gasa,
Atsushi Saito,
Chiaki Nishitani,
Motoko Takahashi,
Takeyuki Shimizu,
Yuichiro Kurimura,
Norimasa Sawada,
Nobuhiro Fujii, Yoshio Kuroki
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ABSTRACT: Pulmonary collectins, surfactant protein A (SP-A) and surfactant protein D (SP-D), play important roles in the innate immunity of the lung. Mycobacterium avium is one of the well-known opportunistic pathogens that can replicate within macrophages. We examined the effects of pulmonary collectins in host defense against M. avium infection achieved via direct interaction between bacteria and collectins. Although both pulmonary collectins bound to M. avium in a Ca(2+)-dependent manner, these collectins revealed distinct ligand-binding specificity and biological activities. SP-A and SP-D bound to a methoxy group containing lipid and lipoarabinomannan, respectively. Binding of SP-D but not SP-A resulted in agglutination of M. avium. A chimeric protein with the carbohydrate recognition domain of SP-D, which chimera revealed a bouquet-like arrangement similar to SP-A, also agglutinated M. avium. The ligand specificity of the carbohydrate recognition domain of SP-D seems to be necessary for agglutination activity. The binding of SP-A strongly inhibited the growth of M. avium in culture media. Although pulmonary collectins did not increase membrane permeability of M. avium, they attenuated the metabolic rate of the bacteria. Observations under a scanning electron microscope revealed that SP-A almost completely covers bacterial surfaces, whereas SP-D binds to certain areas like scattered dots. These observations suggest that a distinct binding pattern of collectins correlates with the difference of their biological activities. Furthermore, the number of bacteria phagocytosed by macrophages was significantly increased in the presence of SP-D. These data indicate that pulmonary collectins play critical roles in host defense against M. avium.
The Journal of Immunology 09/2011; 187(5):2586-94. · 5.79 Impact Factor
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ABSTRACT: Surfactant protein D (SP-D) has been used as a biomarker of lung inflammation. In rat, several types of enzyme-linked immunosorbent assay (ELISA) using polyclonal antibodies have been reported. The purpose of this study was the development of a sensitive ELISA for rat SP-D using monoclonal antibodies. The authors developed a sandwich ELISA using monoclonal antibodies that were obtained by immunizing with purified rat SP-D. The ELISA was evaluated by performance tests. Furthermore, concentrations of serum SP-D were measured in normal control and bleomycin-treated rats. The working range of ELISA was between 0.47 and 30 ng/mL. Different concentrations of added SP-D were recovered, between 94.1% and 102.8%. Serum SP-D levels of bleomycin-treated rats were significantly higher than those of normal rats. In conclusion, this newly developed ELISA for rat SP-D using monoclonal antibodies is applicable for research on the mechanism and therapy of lung injury.
Experimental Lung Research 10/2010; 36(8):463-8. · 1.22 Impact Factor
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ABSTRACT: Leucine rich repeats (LRRs) are present in over 60,000 proteins that have been identified in viruses, bacteria, archae, and eukaryotes. All known structures of repeated LRRs adopt an arc shape. Most LRRs are 20-30 residues long. All LRRs contain LxxLxLxxNxL, in which "L" is Leu, Ile, Val, or Phe and "N" is Asn, Thr, Ser, or Cys and "x" is any amino acid. Seven classes of LRRs have been identified. However, other LRR classes remains to be characterized. The evolution of LRRs is not well understood.
Here we describe a novel LRR domain, or nested repeat observed in 134 proteins from 54 bacterial species. This novel LRR domain has 21 residues with the consensus sequence of LxxLxLxxNxLxxLDLxx(N/L/Q/x)xx or LxxLxCxxNxLxxLDLxx(N/L/x)xx. This LRR domain is characterized by a nested periodicity; it consists of alternating 10- and 11- residues units of LxxLxLxxNx(x/-). We call it "IRREKO" LRR, since the Japanese word for "nested" is "IRREKO". The first unit of the "IRREKO" LRR domain is frequently occupied by an "SDS22-like" LRR with the consensus of LxxLxLxxNxLxxLxxLxxLxx or a "Bacterial" LRR with the consensus of LxxLxLxxNxLxxLPxLPxx. In some proteins an "SDS22-like" LRR intervenes between "IRREKO" LRRs.
Proteins having "IRREKO" LRR domain are almost exclusively found in bacteria. It is suggested that IRREKO@LRR evolved from a common ancestor with "SDS22-like" and "Bacterial" classes and that the ancestor of IRREKO@LRR is 10 or 11 residues of LxxLxLxxNx(x/-). The "IRREKO" LRR is predicted to adopt an arc shape with smaller curvature in which β-strands are formed on both concave and convex surfaces.
BMC Microbiology 09/2010; 10:235. · 3.04 Impact Factor
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Kaku Sawada,
Shigeru Ariki,
Takashi Kojima,
Atsushi Saito,
Masami Yamazoe,
Chiaki Nishitani,
Takeyuki Shimizu,
Motoko Takahashi,
Hiroaki Mitsuzawa,
Shin-Ichi Yokota,
Norimasa Sawada,
Nobuhiro Fujii,
Hiroki Takahashi, Yoshio Kuroki
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ABSTRACT: Pulmonary collectins, surfactant proteins A (SP-A) and D (SP-D), play important roles in innate immunity of the lung. Legionella pneumophila is a bacterial respiratory pathogen that can replicate within macrophages and causes opportunistic infections. L. pneumophila possesses cytolytic activity, resulting from insertion of pores in the macrophage membrane upon contact. We examined whether pulmonary collectins play protective roles against L. pneumophila infection. SP-A and SP-D bound to L. pneumophila and its lipopolysaccharide (LPS) and inhibited the bacterial growth in a Ca(2+)-dependent manner. The addition of LPS in the culture blocked the inhibitory effects on L. pneumophila growth by the collectins, indicating the importance of LPS-collectin interaction. When differentiated THP-1 cells were infected with L. pneumophila in the presence of SP-A and SP-D, the number of permeable cells was significantly decreased, indicating that pulmonary collectins inhibit pore-forming activity of L. pneumophila. The number of live bacteria within the macrophages on days 1-4 after infection was significantly decreased when infection was performed in the presence of pulmonary collectins. The phagocytosis experiments with the pH-sensitive dye-labeled bacteria revealed that pulmonary collectins promoted bacterial localization to an acidic compartment. In addition, SP-A and SP-D significantly increased the number of L. pneumophila co-localized with LAMP-1. These results indicate that pulmonary collectins protect macrophages against contact-dependent cytolytic activity of L. pneumophila and suppress intracellular growth of the phagocytosed bacteria. The promotion of lysosomal fusion with Legionella-containing phagosomes constitutes a likely mechanism of L. pneumophila growth suppression by the collectins.
Journal of Biological Chemistry 03/2010; 285(11):8434-43. · 4.77 Impact Factor
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Kaku Sawada,
Shigeru Ariki,
Takashi Kojima,
Atsushi Saito,
Masami Yamazoe,
Chiaki Nishitani,
Takeyuki Shimizu,
Motoko Takahashi,
Hiroaki Mitsuzawa,
Shin-ichi Yokota,
Norimasa Sawada,
Nobuhiro Fujii,
Hiroki Takahashi, Yoshio Kuroki
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ABSTRACT: Pulmonary collectins, surfactant proteins A (SP-A) and D (SP-D), play important roles in innate immunity of the lung. Legionella pneumophila is a bacterial respiratory pathogen that can replicate within macrophages and causes opportunistic infections. L. pneumophila possesses cytolytic activity, resulting from insertion of pores in the macrophage membrane upon contact. We examined whether
pulmonary collectins play protective roles against L. pneumophila infection. SP-A and SP-D bound to L. pneumophila and its lipopolysaccharide (LPS) and inhibited the bacterial growth in a Ca2+-dependent manner. The addition of LPS in the culture blocked the inhibitory effects on L. pneumophila growth by the collectins, indicating the importance of LPS-collectin interaction. When differentiated THP-1 cells were infected
with L. pneumophila in the presence of SP-A and SP-D, the number of permeable cells was significantly decreased, indicating that pulmonary collectins
inhibit pore-forming activity of L. pneumophila. The number of live bacteria within the macrophages on days 1–4 after infection was significantly decreased when infection
was performed in the presence of pulmonary collectins. The phagocytosis experiments with the pH-sensitive dye-labeled bacteria
revealed that pulmonary collectins promoted bacterial localization to an acidic compartment. In addition, SP-A and SP-D significantly
increased the number of L. pneumophila co-localized with LAMP-1. These results indicate that pulmonary collectins protect macrophages against contact-dependent
cytolytic activity of L. pneumophila and suppress intracellular growth of the phagocytosed bacteria. The promotion of lysosomal fusion with Legionella-containing phagosomes constitutes a likely mechanism of L. pneumophila growth suppression by the collectins.
Journal of Biological Chemistry 03/2010; 285(11):8434-8443. · 4.77 Impact Factor
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ABSTRACT: Vpr, a HIV-1 accessory protein, was believed to be present in the plasma of HIV-1-positive patients, and our previous work demonstrated the presence of plasma Vpr in 20 out of 52 patients. Interestingly, our data revealed that patients' viral titer was correlated with the level of Vpr detected in their plasma. Here, we first show that rVpr, when incubated with human monocytes or MDMs, caused viral production from latently infected cells, and IL-6 was identified as a responsible factor. The induction of IL-6 by rVpr was dependent on signaling through TLR4 and its adaptor molecule, MyD88. We next provide evidence that rVpr induced the formation of OxPC and that a mAb against OxPC blocked rVpr-induced IL-6 production with the concomitant attenuation of MAPK activation. Moreover, the addition of NAC, a scavenger of ROS, abrogated the rVpr-induced formation of OxPC, the phosphorylation of C/EBP-beta, a substrate of MAPK, and IL-6 production. As rIL-6 reactivated viral replication in latently infected cells, our data indicate that rVpr-induced oxidative stress triggers cell-based innate immune responses and reactivates viral production in latently infected cells via IL-6 production. Our results suggest that Vpr should be monitored based on the viral titer, and they provide the rationale for the development of novel, anti-AIDS therapeutics targeting Vpr.
Journal of leukocyte biology 02/2010; 87(6):1133-43. · 4.99 Impact Factor
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ABSTRACT: We have previously shown that lung collectins, surfactant protein A (SP-A) and surfactant protein D, interact with Toll-like receptor (TLR) 2, TLR4, or MD-2. Bindings of lung collectins to TLR2 and TLR4/MD-2 result in the alterations of signaling through these receptors, suggesting the immunomodulatory functions of lung collectins. Mannose binding lectin (MBL) is another collectin molecule which has structural homology to SP-A. The interaction between MBL and TLRs has not yet been determined.
We prepared recombinant MBL, and analyzed its bindings to recombinant soluble forms of TLR4 (sTLR4) and MD-2.
MBL bound to sTLR4 and MD-2. The interactions were Ca2+-dependent and inhibited by mannose or monoclonal antibody against the carbohydrate-recognition domain of MBL. Treatment of sTLR4 or MD-2 by peptide N-glycosidase F significantly decreased the binding of MBL. SP-A bound to deglycosylated sTLR4, and this property did not change in chimeric molecules of SP-A/MBL in which Glu195-Phe228 or Thr174-Gly194 of SP-A were replaced with the corresponding MBL sequences.
These results suggested that MBL binds to TLR4 and MD-2 through the carbohydrate-recognition domain, and that oligosaccharide moieties of TLR4 and MD-2 are important for recognition by MBL. Since our previous studies indicated that lung collectins bind to the peptide portions of TLRs, MBL and lung collectins interact with TLRs by different mechanisms. These direct interactions between MBL and TLR4 or MD-2 suggest that MBL may modulate cellular responses by altering signals through TLRs.
Biochimica et Biophysica Acta 10/2009; 1790(12):1705-10. · 4.66 Impact Factor
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ABSTRACT: Kupffer cells (KC) are important innate immune cells of the liver, functioning as scavenging sinusoidal phagocytes and transducers of pattern recognition signals, including those of toll-like receptors (TLRs). The hepatitis C virus core protein (HCVc) engages TLR2 on peripheral blood monocytes and induces production of multiple inflammatory cytokines. We examined the effects of HCVc on human primary KC functions.
KC were isolated from living donor allografts and stimulated with HCVc and/or ligands for TLRs. KC were examined for production of cytokines, expression of programmed death-ligand 1 (PD-L1), secretion of type 1 interferons (IFNs), and expression of the apoptosis-inducing protein tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL).
HCVc acts as a ligand for TLR2 on human KC, inducing them to secrete interleukin (IL)-1beta, TNF-alpha, and IL-10 and up-regulate cell surface PD-L1. HCVc blocked TLR3-mediated secretion of IFN-alpha, IFN-beta, and cell surface expression of the cytotoxic molecule TRAIL. Inhibition of phosphoinositide 3 kinase with LY294002 blocked the up-regulation of PD-L1 by TLR ligands and the TLR3-specific induction of TRAIL and type 1 IFNs.
KC are intravascular macrophages that are continuously exposed to, and tolerant of, bacterial TLR ligands, which are delivered via the portal circulation. By mimicking a bacterial TLR2 ligand and effectively blocking the TLR3-mediated, double-stranded RNA-induced antiviral response, HCVc might appear to exploit this unique aspect of immunity in the liver.
Gastroenterology 09/2009; 138(1):305-14. · 11.68 Impact Factor
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ABSTRACT: Lipopolysaccharide (LPS), derived from Gram-negative bacteria, is a major cause of acute lung injury and respiratory distress syndrome. Pulmonary surfactant is secreted as a complex mixture of lipids and proteins onto the alveolar surface of the lung. Surfactant phospholipids are essential in reducing surface tension at the air-liquid interface and preventing alveolar collapse at the end of the respiratory cycle. In the present study, we determined that palmitoyl-oleoyl-phosphatidylglycerol and phosphatidylinositol, which are minor components of pulmonary surfactant, and synthetic dimyristoylphosphatidylglycerol regulated the inflammatory response of alveolar macrophages. The anionic lipids significantly inhibited LPS-induced nitric oxide and tumor necrosis factor-alpha production from rat and human alveolar macrophages and a U937 cell line by reducing the LPS-elicited phosphorylation of multiple intracellular protein kinases. The anionic lipids were also effective at attenuating inflammation when administered intratracheally to mice challenged with LPS. Binding studies revealed high affinity interactions between the palmitoyl-oleoyl-phosphatidylglycerol and the Toll-like receptor 4-interacting proteins CD14 and MD-2. Our data clearly identify important anti-inflammatory properties of the minor surfactant phospholipids at the environmental interface of the lung.
Journal of Biological Chemistry 08/2009; 284(38):25488-500. · 4.77 Impact Factor
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ABSTRACT: The role of MD-2 in cell surface expression of Toll-like receptor (TLR) 4 has been controversial. The purposes of this study were to characterize the N-glycan of TLR4 and to investigate the roles of MD-2 in N-linked glycosylation and cell surface expression of TLR4. Lectin blot and cell surface biotinylation revealed that TLR4 exhibited the 110 kDa protein with high mannose type N-glycans and the 130 kDa protein with complex type N-glycans and that only the 130 kDa TLR4 with complex type N-glycans was expressed on the cell surface. The cells transfected with a mutant TLR4(C88A) alone expressed only the 110 kDa TLR4 with a high mannose type N-glycan, which did not appear on the cell surface. However, TLR4(C88A) acquired complex type N-glycans and was expressed on the cell surface when MD-2 was co-transfected. The amount of the 130 kDa TLR4(C88A) with complex type N-glycans expressed on the cell surface depended on that of MD-2 transfected. alpha-Mannosidase II inhibitor blocked the processing N-glycans to complex type, but TLR4 with high mannose type appeared on the cell surface, suggesting that TLR4 is destined to locate on the cell surface before processing N-glycans from a high mannose type to a complex type. From these results, we conclude that MD-2 is critical for cell surface expression of TLR4(C88A). This study provides evidence that MD-2 possesses potential ability to play an essential role in cell surface expression of TLR4.
International Immunology 07/2009; 21(8):925-34. · 3.41 Impact Factor
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ABSTRACT: Among the various posttranslational modification reactions, glycosylation is the most common, and nearly 50% of all known proteins are thought to be glycosylated. In particular, most of the molecules involved in cell-cell communication are glycosylated, and glycosylation is thus implicated in many physiological and pathological events, including cell growth, cell-cell adhesion, and tumor metastasis. As many of the glycosyltransferases are cloned, it is becoming possible to alter the oligosaccharide structures artificially and examine the effects. Among the glycosyltransferases involved in the biosynthesis of N-glycan branching, this review will focus on the function of Fut8 and N-acetylglucosaminyltransferase III, which directly modify the N-glycan core. It is suggested that these two glycosyltransferases are involved in the conformation and the function of the modified proteins including cell-surface receptors and adhesion molecules.
Carbohydrate research 06/2009; 344(12):1387-90. · 2.03 Impact Factor
