Protective effect of lectin from Synadenium carinatum on Leishmania amazonensis infection in BALB/c mice

The protective effect of the Synadenium carinatum latex lectin (ScLL), and the possibility of using it as an adjuvant in murine model of vaccination against American cutaneous leishmaniasis, were evaluated. BALB/c mice were immunized with the lectin ScLL (10, 50, 100 microgram/animal) separately or in association with the soluble Leishmania amazonensis antigen (SLA). After a challenge infection with 10(6) promastigotes, the injury progression was monitored weekly by measuring the footpad swelling for 10 weeks. ScLL appeared to be capable of conferring partial protection to the animals, being most evident when ScLL was used in concentrations of 50 and 100 microgram/animal. Also the parasite load in the interior of macrophages showed significant reduction (61.7%) when compared to the control group. With regard to the cellular response, ScLL 50 and 100 microgram/animal stimulated the delayed-type hypersensitivity (DTH) reaction significantly (P < 0.05) higher than SLA or SLA plus ScLL 10 weeks after the challenge infection. The detection of high levels of IgG2a and the expression of mRNA cytokines, such as IFN-gamma, IL-12, and TNF-alpha (Th1 profiles), corroborated the protective role of this lectin against cutaneous leishmaniasis. This is the first report of the ScLL effect on leishmaniasis and shows a promising role for ScLL to be explored in other experimental models for treatment of leishmaniasis.     

Overexpression of OsJAC1, a Lectin Gene, Suppresses the Coleoptile and Stem Elongation in Rice

Lectin plays an Important role In defense signaling In plants, but its function In plant growth and development is not well known. Previously, we cloneds rice （Oryza sativa L.） gene OsJAC1 encoding s msnnose-blndlng Jscslln-relsted lectln, and found that OsJAC1 was Jssmonlc acid （JA） Inducible. Here we cloned the promoter of OsJAC1, and GUS activity was detected In young roots, coleoptlles, sheaths, leaves, nodes of stems, stems, rschlses, pistils, stsmens and lemmss of OsJAC1：：GUS trsnsgenlc rice, suggesting that OsJAC1 Is s constitutive expression gene In rice. Moreover, OsJAC1-overexpressed （Ubi：：OsJAC1） rice showed dwarfism with shorter coleptlles resulting from the failure of cell elongation of coleoptlles. In addition, compared with coleoptlles of wild-type plants, those of OsJAC1 overexpresslon rice were more sensitive to JA treatment. These data revealed that, besides Its roles in defense response, lectin plays an Important role in rice growth and development.     

Purification and characterization of a mannose-binding lectin from the rhizomes of Aspidistra elatior Blume with antiproliferative activity

A lectin with a novel N-terminal amino acid sequence was purified from the rhizomes of Aspidistra elatior Blume by ammonium sulphate precipitation, ion exchange chromatography on diethylaminoethyl-Sepharose and carboxymethyl-Sepharose and gel filtration chromatography on Sephacryl S-100. The A. elatior Blume lectin （AEL） is a heterotetramer with a molecular mass of 56 kDa and composed of two homodimers consisting of two different polypeptides of 13.5 kDa and 14.5 kDa held together by noncovalent interactions. Hapten inhibition assay indicated that hemagglutinating activity of AEL towards rabbit erythrocytes could be inhibited by D-mannose, mannan, thyroglobulin and ovomucoid. The lectin was stable up to 70 ℃ , and showed maximum activity in a narrow pH range of 7.0-8.0. Chemical modification and spectrum analysis indicated that tryptophan, arginine, cysteine and carboxyl group residues were essential for its hemagglutinating activity. However, they might not be present in the active center, except some carboxyl group residues. AEL also showed significant in vitro antiproliferative activity towards Bre-04 （66%）, Lu-04 （60%） and HepG2 （56%） of human cancer cell lines.     

Inhibitory Effect of Supercritical Extracts from Arctium lappa L. on the Lectin Pathway of the Complement System

The complement system participates in host defense by eliminating microorganisms and triggering inflammation. However, insufficient control or exacerbated complement activation contributes to inflammatory diseases. Since promising antioxidant and anti‐inflammatory activities have been identified in Arctium lappa L. extracts, this study aims to explore the effect of A. lappa extracts on the lectin pathway (LP) of complement activation. Four extracts were obtained by supercritical extraction using scCO₂ with or without ethanol as co‐solvent, at different temperatures and pressures (E1: 2.2 mg/mL, E2: 2.6 mg/mL and E3: 2.0 mg/mL, E4: 1.5 mg/mL). To evaluate the effect of A. lappa extracts on the LP activation, an ELISA assay using mannose binding lectin pathway of complement was carried out with C4 detection. All extracts showed a concentration‐dependent inhibitory effect on the activation of complement by the LP. The following IC₅₀ were observed for E1, E2, E3 and E4: 179.4 μg/mL, 74.69 μg/mL, 119.1 μg/mL and 72.19 μg/mL, respectively. Our results suggest that A. lappa extracts are potential candidates for the treatment of inflammatory disorders that are complement‐related.     

伊蚊C型凝集素mosGCTL-2是登革病毒感染相关的重要蛋白质

C型凝集素是一类含有糖结合结构域的蛋白质,从节肢动物到哺乳动物的C型凝集素都具有共同的基序,它在进化上相当保守,在免疫反应中发挥重要作用. 埃及伊蚊表达30多种C型凝集素蛋白,它是登革病毒的关键传播媒介,这些蛋白质对病毒和细菌感染均有至关重要的作用. 最近研究表明,C型凝集素mosGCTL-3与二型登革热病毒包膜蛋白具有相互作用,能够增强登革病毒对埃及伊蚊的感染. 在本文中,我们发现了C型凝集素蛋白mosGCTL-2具有与mosGCTL-3类似的功能. 两种C型凝集素mosGCTL-2和mosGCTL-3的氨基酸残基序列一致性高达43.56％. 为研究mosGCTL-2在登革病毒蚊媒传播中的作用,我们通过果蝇S2细胞表达系统表达纯化了mosGCTL-2蛋白. 结果表明,mosGCTL-2与二型登革热病毒包膜蛋白的结合具有钙离子依赖性. 进一步的研究表明,埃及伊蚊感染登革病毒能够诱导mosGCTL2表达上调,是二型登革热病毒感染埃及伊蚊所必需的蛋白质. 以上研究说明,mosGCTL-2蛋白可能是在登革热病毒感染埃及伊蚊中起重要作用的一种模式识别受体.     

Novel Ca2+‐independent carbohydrate recognition of the C‐type lectins,SPL‐1 and SPL‐2, from the bivalve Saxidomus purpuratus

Novel Ca²⁺‐independent C‐type lectins, SPL‐1 and SPL‐2, were purified from the bivalve Saxidomus purpuratus. They are composed of dimers with either identical (SPL‐2 composed of two B‐chains) or distinct (SPL‐1 composed of A‐ and B‐chains) polypeptide chains, and show affinity for N‐acetylglucosamine (GlcNAc)‐ and N‐acetylgalactosamine (GalNAc)‐containing carbohydrates, but not for glucose or galactose. A database search for sequence similarity suggested that they belong to the C‐type lectin family. X‐ray crystallographic analysis revealed definite structural similarities between their subunits and the carbohydrate‐recognition domain (CRD) of the C‐type lectin family. Nevertheless, these lectins (especially SPL‐2) showed Ca²⁺‐independent binding affinity for GlcNAc and GalNAc. The crystal structure of SPL‐2/GalNAc complex revealed that bound GalNAc was mainly recognized via its acetamido group through stacking interactions with Tyr and His residues and hydrogen bonds with Asp and Asn residues, while widely known carbohydrate‐recognition motifs among the C‐type CRD (the QPD [Gln‐Pro‐Asp] and EPN [Glu‐Pro‐Asn] sequences) are not involved in the binding of the carbohydrate. Carbohydrate‐binding specificities of individual A‐ and B‐chains were examined by glycan array analysis using recombinant lectins produced from Escherichia coli cells, where both subunits preferably bound oligosaccharides having terminal GlcNAc or GalNAc with α‐glycosidic linkages with slightly different specificities.     

Exacerbation of experimental autoimmune encephalomyelitis in mice deficient for DCIR,an inhibitory C-type lectin receptor

Dendritic cell immunoreceptor (DCIR) is a C-type lectin receptor containing a carbohydrate recognition domain in its extracellular portion and an immunoreceptor tyrosine–based inhibitory motif, which transduces negative signals into cells, in its cytoplasmic portion. Previously, we showed that Dcir^–/– mice spontaneously develop autoimmune diseases such as enthesitis and sialadenitis due to excess expansion of dendritic cells (DCs), suggesting that DCIR is critically important for the homeostasis of the immune system. In this report, we analyzed the role of DCIR in the development of experimental autoimmune encephalomyelitis (EAE), an autoimmune disease model for multiple sclerosis. We found that EAE was exacerbated in Dcir^–/– mice associated with severe demyelination of the spinal cords. The number of infiltrated CD11c⁺ DCs and CD4⁺ T cells into spinal cords was increased in Dcir^–/– mice. Recall proliferative response of lymph node cells was higher in Dcir^–/– mice compared with wild-type mice. These observations suggest that DCIR is an important negative regulator of the immune system, and Dcir^–/– mice should be useful for analyzing the roles of DCIR in an array of autoimmune diseases.     

Anti-inflammatory deficiencies in neutrophilic asthma: reduced galectin-3 and IL-1RA/IL-1β

Background

Galectin-3 (gal-3), a member of the β-galactoside-binding animal lectins, is involved in the recruitment, activation and removal of neutrophils. Neutrophilic asthma is characterized by a persistent elevation of airway neutrophils and impaired efferocytosis. We hypothesized that sputum gal-3 would be reduced in neutrophilic asthma and the expression of gal-3 would be associated with other markers of neutrophilic inflammation.

Methods

Adults with asthma (n = 80) underwent a sputum induction following clinical assessment and blood collection. Sputum was dispersed for a differential cell count and ELISA assessment of gal-3, gal-3 binding protein (BP), interleukin (IL)-1β, IL-1 receptor antagonist (RA), IL-8 and IL-6. Gal-3 and gal-3BP immunoreactivity were assessed in mixed sputum cells.

Results

Sputum gal-3 (median, (q1,q3)) was significantly reduced in neutrophilic asthma (183 ng/mL (91,287)) compared with eosinophilic (293 ng/mL (188,471), p = 0.021) and paucigranulocytic asthma (399 ng/mL (213,514), p = 0.004). The gal-3/gal-3BP ratio and IL-1RA/IL-1β ratio were significantly reduced, while gal-3BP and IL-1β were significantly elevated in neutrophilic asthma compared with eosinophilic and paucigranulocytic asthma.

Conclusion

Patients with neutrophilic asthma have impairment in anti-inflammatory ratio of gal-3/gal-3BP and IL-1RA/IL-1β which provides a further framework for exploration into pathologic mechanisms of asthma phenotypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0163-5) contains supplementary material, which is available to authorized users.     

Structural Hot Spots Determine Functional Diversity of the Candida glabrata Epithelial Adhesin Family

For host colonization, the human fungal pathogen Candida glabrata is known to utilize a large family of highly related surface-exposed cell wall proteins, the lectin-like epithelial adhesins (Epas). To reveal the structure-function relationships within the entire Epa family, we have performed a large scale functional analysis of the adhesion (A) domains of 17 Epa paralogs in combination with three-dimensional structural studies of selected members with cognate ligands. Our study shows that most EpaA domains exert lectin-like functions and together recognize a wide variety of glycans with terminal galactosides for conferring epithelial cell adhesion. We further identify several conserved and variable structural features within the diverse Epa ligand binding pockets, which affect affinity and specificity. These features rationalize why mere phylogenetic relationships within the Epa family are weak indicators for functional classification and explain how Epa-like adhesins have evolved in C. glabrata and related fungal species.     

Sialic Acids on Varicella-Zoster Virus Glycoprotein B Are Required for Cell-Cell Fusion

Varicella-zoster virus (VZV) is a member of the human Herpesvirus family that causes varicella (chicken pox) and zoster (shingles). VZV latently infects sensory ganglia and is also responsible for encephalomyelitis. Myelin-associated glycoprotein (MAG), a member of the sialic acid (SA)-binding immunoglobulin-like lectin family, is mainly expressed in neural tissues. VZV glycoprotein B (gB) associates with MAG and mediates membrane fusion during VZV entry into host cells. The SA requirements of MAG when associating with its ligands vary depending on the specific ligand, but it is unclear whether the SAs on gB are involved in the association with MAG. In this study, we found that SAs on gB are essential for the association with MAG as well as for membrane fusion during VZV infection. MAG with a point mutation in the SA-binding site did not bind to gB and did not mediate cell-cell fusion or VZV entry. Cell-cell fusion and VZV entry mediated by the gB-MAG interaction were blocked by sialidase treatment. N-glycosylation or O-glycosylation inhibitors also inhibited the fusion and entry mediated by gB-MAG interaction. Furthermore, gB with mutations in N-glycosylation sites, i.e. asparagine residues 557 and 686, did not associate with MAG, and the cell-cell fusion efficiency was low. Fusion between the viral envelope and cellular membrane is essential for host cell entry by herpesviruses. Therefore, these results suggest that SAs on gB play important roles in MAG-mediated VZV infection.