Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Immulectin, a C-type lectin from the tobacco hornworm, Manduca sexta, was cloned from a larval fat body cDNA library. The immulectin cDNA encodes a 309 residue polypeptide. Immulectin synthesis was induced by injection of killed gram-positive or gram-negative bacteria or yeast. After injection of bacteria, immulectin mRNA appeared in fat body and immulectin protein was detected in hemolymph. Immulectin contains two carbohydrate recognition domains. The carboxyl-terminal carbohydrate recognition domain is most similar (36% identity) to a lipopolysaccharide-binding protein from the American cockroach, Periplaneta americana. It also shares 26-35% identity to carbohydrate recognition domains of various mammalian C-type lectins. Two immulectin isoforms were identified in the hemolymph of bacteria-injected larvae. Recombinant immulectin agglutinated gram-positive and gram-negative bacteria and yeast. Addition of recombinant immulectin to M. sexta plasma stimulated activation of phenol oxidase. A combination of immulectin with lipopolysaccharide from E. coli activated phenol oxidase more rapidly and to a higher level than immulectin alone, whereas lipopolysaccharide by itself had little effect on phenol oxidase activation. Immulectin synthesized in response to bacterial or fungal infection may help to trigger protective responses in M. sexta in a manner similar to mannose-binding protein, a C-type lectin that functions in the mammalian innate immune system.
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PMID:Immulectin, an inducible C-type lectin from an insect, Manduca sexta, stimulates activation of plasma prophenol oxidase. 1043 35

We have cloned the mouse homologue of human Langerin (h-Langerin), a type II transmembrane protein with a single external C-type lectin domain. Mouse Langerin (m-Langerin) displays 65 and 74% homologies in total amino acid and lectin domains with those of h-Langerin. The cognate mouse and rat genes were assigned to chromosome 6D1-D2 and chromosome 4q33 distal-q34.1 proximal respectively, syntenic to the h-Langerin gene on chromosome 2p13. With RT-PCR, m-Langerin transcripts were as expected detected in MHC class II+, but not MHC class II-, cells from epidermis and the expression level was reduced by culture. However, m-Langerin transcripts were also expressed in spleen, lymph nodes (LN), thymus, liver, lung and even heart, but not gut-associated lymphoid tissues. In single-cell lymphoid suspensions, m-Langerin transcripts were mainly detected in the CD11c+ dendritic cells (DC), especially the CD11blow/CD8high fraction of spleen and LN. DC generated from bone marrow precursors by granulocyte macrophage colony stimulating factor (GM-CSF) expressed m-Langerin, but this was shut down during maturation with CD40 ligand or lipopolysaccharide. DC derived from blood monocytes by GM-CSF + IL-4 lacked m-Langerin unless the cultures were supplemented with transforming growth factor (TGF)-beta1. Unexpectedly, significant amounts of m-Langerin transcripts were detected in skin and LN of TGF-beta1-deficient mice, although in much lower amounts than littermate controls. Recombinant m-Langerin could form multimers and bind to mannan-agarose. These findings indicate that Langerin expression is regulated at several levels: by TGF-beta1, DC subsets, DC maturation and the tissue environment.
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PMID:Identification and expression of mouse Langerin (CD207) in dendritic cells. 1197 73

In insects, the prophenoloxidase activation system is a defense mechanism against parasites and pathogens. Recognition of parasites or pathogens by pattern recognition receptors triggers activation of a serine proteinase cascade, leading to activation of prophenoloxidase-activating proteinase (PAP). PAP converts inactive prophenoloxidase (proPO) to active phenoloxidase (PO), which then catalyzes oxidation of phenolic compounds that can polymerize to form melanin. Because quinone intermediates and melanin are toxic to both hosts and pathogens, activation of proPO must be tightly regulated and localized. We report here purification and cDNA cloning of serine proteinase homologs (SPHs) from the tobacco hornworm, Manduca sexta, which interact with PAP-1 in proPO activation. Two SPHs were co-purified from plasma of M. sexta larvae with immulectin-2, a C-type lectin that binds to bacterial lipopolysaccharide. They contain an amino-terminal clip domain connected to a carboxyl-terminal serine proteinase-like domain. PAP-1 alone cannot efficiently activate proPO, but a mixture of SPHs and PAP-1 was much more effective for proPO activation. Immulectin-2, proPO and PAP-1 in hemolymph bound to the immobilized recombinant proteinase-like domain of SPH-1, indicating that a complex containing these proteins may exist in hemolymph. Since immulectin-2 is a pattern recognition receptor that binds to surface carbohydrates on pathogens, such a protein complex may localize activation of proPO on the surface of pathogens. SPH, which binds to immulectin-2, may function as a mediator to recruit proPO and PAP to the site of infection.
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PMID:Nonproteolytic serine proteinase homologs are involved in prophenoloxidase activation in the tobacco hornworm, Manduca sexta. 1253 78

We previously reported the isolation of a lipopolysaccharide (LPS)-specific immulectin-2 from the tobacco hornworm, Manduca sexta [J. Biol. Chem. 275 (2000) 37373]. Immulectin-2 is a C-type lectin that is present at a constitutively low level in hemolymph of naive larvae, and its synthesis is induced after injection of Gram-negative bacteria or LPS. Immulectin-2 contains two carbohydrate recognition domains. It binds to LPS and stimulates prophenoloxidase activation in plasma. In this paper, we focus on properties of carbohydrate recognition domain-2 of immulectin-2 and the biological functions of immulectin-2 in immune responses. The carboxyl-terminal carbohydrate recognition domain (CRD2) of immulectin-2 was able to bind bacterial LPS. Binding of recombinant CRD2 to LPS stimulated activation of prophenoloxidase in plasma. Injection of antiserum against immulectin-2 into M. sexta larvae inhibited clearance of a Gram-negative bacterial pathogen, Serratia marcescens, and decreased survival of infection. These results suggest that immulectin-2 plays an important role in the immune system of M. sexta, and helps to protect the animal from Gram-negative bacterial infections.
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PMID:Manduca sexta lipopolysaccharide-specific immulectin-2 protects larvae from bacterial infection. 1259 Sep 70

Dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) is a type II C-type lectin that functions as an adhesion receptor and mediates binding and internalization of pathogens such as virus (human immunodeficiency virus, hepatitis C), bacteria (Mycobacterium), fungi, and parasites. DC-SIGN expression in vivo is primarily restricted to interstitial dendritic cells (DC) and certain tissue macrophages. We now report that leukemic THP-1 cells, widely used as a model for monocyte-macrophage differentiation, express very low basal levels of DC-SIGN and that DC-SIGN expression in THP-1 cells is regulated during differentiation. Differentiation-inducing agents (phorbol ester, bryostatin) conveyed THP-1 cells with the ability to up-regulate DC-SIGN mRNA levels and cell surface expression in response to interleukin-4 (IL-4) or IL-13. DC-SIGN up-regulation required a functional JAK-STAT signaling pathway, was inhibited in the presence of lipopolysaccharide (LPS) or tumor necrosis factor-alpha (TNF-alpha), and conferred THP-1 cells with increased pathogen recognition and T cell stimulatory capabilities. The up-regulation of DC-SIGN on THP-1 cells resembles its inducible expression on monocytes and macrophages, where DC-SIGN expression is also induced by IL-4/IL-13 and negatively regulated by TNF-alpha, LPS, and vitamin D(3). These results point to THP-1 cells as a useful cellular system to characterize the pathogen-binding capabilities of DC-SIGN and to dissect the molecular mechanisms that control its regulated and tissue-specific expression in myeloid dendritic cells, and the results suggest that DC-SIGN constitutes a marker for both DC and alternatively activated macrophages.
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PMID:Regulated expression of the pathogen receptor dendritic cell-specific intercellular adhesion molecule 3 (ICAM-3)-grabbing nonintegrin in THP-1 human leukemic cells, monocytes, and macrophages. 1507 Sep 1

A new C-type lectin with putative mannose specificity was identified from the expressed sequence tag (EST) analysis of cDNA library from common carp head kidney (HK), stimulated with concanavalin A and lipopolysaccharide (LPS) during a routine EST analysis. The full sequence of 627 bp was identified by 5'-rapid amplification of cDNA ends. The gene is composed of 146 amino acid residues, including an 18-residue signal peptide for secretion and a single carbohydrate-recognition domain of approximately 118 residues typical of C-type lectins. Based on the predicted structure, this is a calcium dependent C-type lectin with putative mannose specificity suggested by the presence of an EPN motif. By hemagglutination assay, the mannose specificity of the Ca-CTL was determined. Reverse transcription (RT) PCR analysis demonstrated the expression of Ca-CTL mRNA in the hematopoietic organs and also the level of expression increased with LPS induction. Localization studies by in situ hybridization showed the presence of transcripts in the organs.
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PMID:Characterization of a new C-type lectin from common carp Cyprinus carpio. 1526 61

The diverse receptors of the C-type lectin superfamily play key roles in innate immunity. In mammals, cell surface receptors with C-type lectin domains are involved in pathogen recognition and in immune response, and in some cases are exploited by pathogens to gain entry into cells. This study reports on sequence and expression analysis of three paralogous group II C-type lectins from the teleost fish Atlantic salmon (Salmo salar). Each of the receptors showed similarity to immune-relevant mammalian receptors in terms of amino acid sequence and overall organization within the C-type lectin-like domain (CTLD). Two of the three have cytoplasmic motifs consistent with the immunoreceptor tyrosine-based activation motifs (ITAM), which are known to modulate downstream functions in leukocytes. All three C-type lectin receptors were expressed in multiple tissues of healthy fish, including peripheral blood leukocytes and salmon head kidney cells (SHK-1). Each receptor was up-regulated in salmon liver in response to infection by Aeromonas salmonicida and one receptor was substantially up-regulated in cultured SHK-1 cells in response to lipopolysaccharide (LPS). Putative binding sites for the CAAT-enhancer-binding protein (C/EBP) family of transcription factors in the regulatory regions of these C-type lectin genes may mediate their response to bacteria and LPS in salmon leukocytes. The identification of these types of receptors in distinct populations of cells within the immune system will provide important markers for identifying and categorizing the state of differentiation or activation of these cells and lead to further understanding of the interaction between the salmon host and multiple pathogens.
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PMID:Sequence and expression of C-type lectin receptors in Atlantic salmon (Salmo salar). 1549 Jan 54

The human gastric pathogen Helicobacter pylori spontaneously switches lipopolysaccharide (LPS) Lewis (Le) antigens on and off (phase-variable expression), but the biological significance of this is unclear. Here, we report that Le+ H. pylori variants are able to bind to the C-type lectin DC-SIGN and present on gastric dendritic cells (DCs), and demonstrate that this interaction blocks T helper cell (Th)1 development. In contrast, Le- variants escape binding to DCs and induce a strong Th1 cell response. In addition, in gastric biopsies challenged ex vivo with Le+ variants that bind DC-SIGN, interleukin 6 production is decreased, indicative of increased immune suppression. Our data indicate a role for LPS phase variation and Le antigen expression by H. pylori in suppressing immune responses through DC-SIGN.
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PMID:Helicobacter pylori modulates the T helper cell 1/T helper cell 2 balance through phase-variable interaction between lipopolysaccharide and DC-SIGN. 1549 23

In invertebrates, C-type lectin plays an important role in innate immunity by mediating the recognition of pathogens to host cells and clearing microinvaders. A few C-type lectins have been identified from shrimps, but none of their gene or protein sequences is known to date. In this paper, a C-type lectin (named PmLec) specific for bacterial lipopolysaccharide was purified from the serum of the shrimp Penaeus monodon. The binding of PmLec to lipopolysaccharide was mainly mediated through the O-antigen. PmLec had a strong hemagglutinating and bacterial-agglutinating activity as well as an opsonic effect that enhances hemocyte phagocytosis. The PmLec cDNA sequence was obtained from the cDNA library of P. monodon by polymerase chain reaction with the degenerated primer designed according to the amino-terminal residue sequence of purified PmLec. A 546-bp open reading frame was found to encode a putative protein comprising 182 amino acids and containing a preceding signal peptide of 17 amino acids. A C-type lectin domain existed in PmLec, but no glycosylation site was found. The recombinant PmLec protein expressed in Escherichia coli also showed the same agglutinating activity and opsonic effect as that of the native protein. This is the first report of a lectin cDNA from the shrimp. PmLec functions as a pattern-recognition protein and an opsonin in the shrimp, and it provides a clue to elucidate the role of lectin in the innate immunity of aquatic invertebrates at the molecular level.
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PMID:Purification, characterization and cDNA cloning of a novel lipopolysaccharide-binding lectin from the shrimp Penaeus monodon. 1636 36

C-type lectins play an important role in the immune system and are part of a large superfamily that includes C-type lectin-like domain (CTLD)-containing proteins. Divergent evolution, acting on the CTLD fold, has generated the Ca2+-dependent carbohydrate-binding lectins and molecules, as the lectin-like natural killer (NK) receptors that bind proteins, rather than sugars, in a Ca(2+)-independent manner. We have studied ciCD94-1, a CTLD-containing protein from the tunicate Ciona intestinalis, which is a homolog of the CD94 vertebrate receptor that is expressed on NK cells and modulates their cytotoxic activity by interacting with MHC class I molecules. ciCD94-1 shares structural features with the CTLD-containing molecules that recognize proteins, suggesting that it could be located along the evolutionary pathway leading to the NK receptors. ciCD94-1 was up-regulated in response to inflammation induced by lipopolysaccharide (LPS) acting on a blood cell type present in both the tunic and circulating blood. Furthermore, an anti-ciCD94-1 antibody specifically inhibited the phagocytic activity of these cells. ciCD94-1 was also expressed during development in the larva and in the early stages of metamorphosis in structures related to the nervous system, and loss of its function affected the correct differentiation of these territories. These findings suggest that ciCD94-1 has different roles in immunity and in development, thus strengthening the concept of gene co-option during evolution and of an evolutionary relationship between the nervous and the immune systems.
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PMID:ciCD94-1, an ascidian multipurpose C-type lectin-like receptor expressed in Ciona intestinalis hemocytes and larval neural structures. 1792 66


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