Academic literature on the topic 'Lectin receptor'

In order to study whether the carbohydrate moieties of the human placental IGF-I receptor (IGF1R), IGF-II receptor (IGF2R) and insulin receptors (IRs) play a role in ligand binding, solubilised cell membrane preparations were incubated with 125I-labelled IGF-I, IGF-II and insulin in the presence of lectins with different sugar specificities. Three incubation procedures were tested: ligand-first, co-incubation and lectin-first incubation. Wheat germ agglutinin (WGA), concanavalin A (Con A) and phytohaemagglutinin (PHA) altered the binding of IGF-I and insulin to their high-affinity receptors in a lectin specific and dose-dependent manner, whereas these lectins did not affect the interaction of IGF-II with its receptor(s). Moreover, the same lectins either inhibited or enhanced IGF-I and insulin binding, depending on the incubation scheme. These results also suggest that IR-A and IR-B from human placenta might be differently glycosylated.

Many members of the C-type lectin family of glycan-binding receptors have been ascribed roles in the recognition of microorganisms and serve as key receptors in the innate immune response to pathogens. Other mammalian receptors have become targets through which pathogens enter target cells. These receptor roles have often been documented with binding studies involving individual pairs of receptors and microorganisms. To provide a systematic overview of interactions between microbes and the large complement of C-type lectins, here we developed a lectin array and suitable protocols for labeling of microbes that could be used to probe this array. The array contains C-type lectins from cow, chosen as a model organism of agricultural interest for which the relevant pathogen–receptor interactions have not been previously investigated in detail. Screening with yeast cells and various strains of both Gram-positive and -negative bacteria revealed distinct binding patterns, which in some cases could be explained by binding to lipopolysaccharides or capsular polysaccharides, but in other cases they suggested the presence of novel glycan targets on many of the microorganisms. These results are consistent with interactions previously ascribed to the receptors, but they also highlight binding to additional sugar targets that have not previously been recognized. Our findings indicate that mammalian lectin arrays represent unique discovery tools for identifying both novel ligands and new receptor functions.

ABSTRACT Although sialic acid has long been recognized as the primary receptor determinant for attachment of influenza virus to host cells, the specific receptor molecules that mediate viral entry are not known for any cell type. For the infection of murine macrophages by influenza virus, our earlier study indicated involvement of a C-type lectin, the macrophage mannose receptor (MMR), in this process. Here, we have used direct binding techniques to confirm and characterize the interaction of influenza virus with the MMR and to seek additional macrophage surface molecules that may have potential as receptors for viral entry. We identified the macrophage galactose-type lectin (MGL) as a second macrophage membrane C-type lectin that binds influenza virus and is known to be endocytic. Binding of influenza virus to MMR and MGL occurred independently of sialic acid through Ca2+-dependent recognition of viral glycans by the carbohydrate recognition domains of the two lectins; influenza virus also bound to the sialic acid on the MMR. Multivalent ligands of the MMR and MGL inhibited influenza virus infection of macrophages in a manner that correlated with expression of these receptors on different macrophage populations. Influenza virus strain A/PR/8/34, which is poorly glycosylated and infects macrophages poorly, was not recognized by the C-type lectin activity of either the MMR or the MGL. We conclude that lectin-mediated interactions of influenza virus with the MMR or the MGL are required for the endocytic uptake of the virus into macrophages, and these lectins can thus be considered secondary or coreceptors with sialic acid for infection of this cell type.

The asialoglycoprotein receptor belongs to the family of calcium-dependent (C-type) animal lectins. The purified receptor is a glycoprotein in which 10 % of the dry weight consists of sialic acid, galactose, N-acetylglucosamine and mannose. The carbohydrate content of the asialoglycoprotein receptor was investigated by lectin affinity methods. The usefulness of plant lectin affinity methods in the characterization of the saccharide content of the asialoglycoprotein receptor, as an animal lectin, is demonstrated. RCA I ConA, PHA, SNA I and WGA showed greater affinity toward the asialoglycoprotein receptor, while PSL, AAA and PNA showed negligible interactions with the asialoglycoprotein receptor. The obtained results correlated well with the carbohydrate content of the asialoglycoprotein receptor as determined by chemical methods.

Aim. This work is devoted to the search the abnormalities of the receptor-lectin reactions associated with glioblastoma for diagnostic purposes. Methods. Red blood cell (RBC) specimens were taken from 22 persons distributed into the two cohorts: donors without an oncological diagnosis; patients with glioblastoma (GB). Panel of 9 commercial lectins (LECTINOTEST, Lviv, Ukraine) was used: ConA, WGA, PHA-P; PHA-E; PHA-L, SNA, VAA, STA, and LABA. Also the original lectin from persimmon sepals (named PSL) was used. It was obtained by isoelectric focusing and ammonium sulfate fractionation. Intensity of lectin-receptor interactions was determined in reaction of hemagglutination. Results. Тwo lectins showed some directed divergence in patients from donors. For wheat germ agglutinin (WGA) сhanges in the intensity of lectin-receptor binding were downward. In the case of persimmon L (PSL) the alternative result was observed: the intensity of hemagglutination showed a trend to exceed the level of control. Conclusions. Some individual features in the reaction of erythrocytes with a set of lectins are observed in all examined persons. For two studied lectins, namely WGA and PSL, unidirectional deviations were observed in the reaction of erythrocytes of patients with GB compared to individuals without an oncological diagnosis.

Interactions between cells or between cell and substratum involve specificreceptors and their ligands. Among the various cell surface receptorsidentified during the last decades, the carbohydrate-binding proteins, e.g., lectins are of peculiar interest because glycolipids, glycoproteinsand proteoglycans have been shown to interact with lectins on the surfaceof animal cells. Animal lectins are recognized as molecules playingimportant roles in a variety of biological processes through binding toglycoconjugates and lectin-like receptors such as selectins, sialoadhesins(CD22, CD33), natural killer receptors (NKR-P1, CD69 and CD94/NKG2), hyaluronate receptors (CD44, RHAMM, ICAM-1), B-cell associated antigen(CD23, CD72), γ2 leukocyte integrin (CD11b/CD18) or the well-knownreceptors for mannose, mannose-6-phosphate or asialoglycoprotein havebeen suggested to be able to mediate the transfer of information fromthe outside to the inside of the cell. This review focuses on the mostrecent advances in our understanding of the molecular basis of “outside-in” signaling mediated by lectins. Lectin-likereceptors are involved in signal transduction in a great variety of ways;at the molecular level, they mimic in most of the cases the function ofgrowth factor receptor either coupled to tyrosine kinase activity or toheterotrimeric G protein. They lead to a multiplicity of cellular eventsfollowing their activation depending on factors such as cellular type, species and/or tissue. Nevertheless the potential of surface lectins astransducers is emphasized by the observation that in a few cases lectin-likereceptors induce either novel signal transduction mechanism or newintracellular events with regards to what it has been observed as aconsequence of growth factor receptor activation. This observation bringsthe idea that lectins may offer, as cell surface transducers, an alternativeor additional signaling potential to cell.

Aim: Growing interest in lectins is based on their diagnostic and pharmacological potential, especially the ability to inhibit proliferation and initiate apoptosis of cancer cells. In our research microplate lectinoassay able to detect carbohydrate containing structures (receptors) on erythrocyte surface have been proposed for Chornobyl cleanup workers (1986) monitoring. It was expected to reveal specific abnormalities associated with pathological condition arising as a result of late radiation effects. Materials and Methods: Red blood cell (RBC) specimens were taken from 171 persons distributed into the six cohorts: nonexposed donors (1); chronically exposed to the doses below (2) and over 50 cGy (3); exposed to acute radiation without (4) and with manifestation of acute radiation syndrome (5 and 6). Lectins from 24 species of medicinal plants were purified by ethanol fractionation and electrofocusing. Intensity of lectin-receptor interactions was determined in reaction of hemagglutination. Method of flow cytofluorometry was used to study B-cell counts. Hormone levels in blood serum were determined by radioimmunoassay. Results: An elevated ability of RBC to interact with the panel of lectins was found in all cohorts of exposed persons versus nonexposed donors, moreover, changes in the intensity of lectin-receptor binding depended on the dose of irradiation. Diagnostic value of specific RBC reactions with some individual lectins has been elucidated. Elevated intensity of RBC reaction with Zea mays lectin was accompanied by a decrease in serum content of thyroid hormones T4 and T3, as well as reduction of B-cell counts. In the case of Rubus caesius lectin the more intensive reaction with RBC, the higher level of hormone cortisol was observed. Conclusions: Deviations from donor’s norm in intensity of lectin — RBC interactions in radiation exposed men are supposed to carry information about negative changes in their health status following Chornobyl catastrophe and show the diagnostic potential. The most sensitive reactions have been associated primarily with shifts in endocrine and immune systems. This article is a part of a Special Issue entitled “The Chornobyl Nuclear Accident: Thirty Years After”.

Analysis of the human NK (natural killers) cells and their functionally different populations in connection to tumor processes accompanied with viral infections is presented. Receptor lectins (non-immunoglobulin proteins and their complexes recognizing polysaccharides, glycoconjugates and glycopattern-containing molecules) play important role in regulation of innate immunity. Communicative diversity of NK-cell populations (in which lectins cofunction to other receptors) is directed against tumors and viruses. Effectiveness and selectivity of action of NK cell populations can be increased in cooperation together with adaptive immunity. Evaluations of occurrence, redistribution (also under influence of cytokines) and contribution of NK-populations (depending on lectin receptors recognition coupled to multifunctions of receptors) in respect of increasing antitumor and antiviral immune responces are given. The data indicate extended prospects of lectin receptors (coupled to other type receptors) containing NK populations of the network compartment of innate immunity upon realization of different variants of organism protection in cooperation with cellular and humoral immunity. Such NK populations are the basis for further intercellular interactions. Innate immunity Cross-Talk, involving the leader NK cell populations acting according to humoral immunity mechanisms, acts on duty regime (importance for therapy of chronic pathology) that results in providing optimal combined antitumor and antiviral cytokine and cytotoxic responses according to the principle of action as «network-in-network». The influence network of lectin, Ig-like, cytotoxic, other regulator NK populations (also throuph redistribution of production of cytokines by immunocompetent cells) is perspective for forming early prolongated antitumor and antiviral processes of different types in organism. It is of importance to consider CD diversity of receptor repertuar of lectin, Ig-like and other NK populations revealing different ontogenesis as well as to seach patient key NK-populations to select and construct personally (or for contingents in cases of epidemiological significance) optimal therapeutic/prophylactic NK populations (like variants of CAR-T). Aforementioned data indicate perspectiveness of NK cell populations in development of new antitumor/antiviral effective and selective vaccine strategies, preparations and regimes of their applications. Probiotic lectins reveal features of perspective ligands cofunctioning to network of NK cell populations.

Lectins are glycan-binding proteins with no catalytic activity and ubiquitously expressed in nature. Numerous bacteria use lectins to efficiently bind to epithelia, thus facilitating tissue colonisation. Wounded skin is one of the preferred niches for Pseudomonas aeruginosa, which has developed diverse strategies to impair tissue repair processes and promote infection. Here, we analyse the effect of the P. aeruginosa fucose-binding lectin LecB on human keratinocytes and demonstrate that it triggers events in the host, upon binding to fucosylated residues on cell membrane receptors, which extend beyond its role as an adhesion molecule. We found that LecB associates with insulin-like growth factor-1 receptor and dampens its signalling, leading to the arrest of cell cycle. In addition, we describe a novel LecB-triggered mechanism to down-regulate host cell receptors by showing that LecB leads to insulin-like growth factor-1 receptor internalisation and subsequent missorting towards intracellular endosomal compartments, without receptor activation. Overall, these data highlight that LecB is a multitask virulence factor that, through subversion of several host pathways, has a profound impact on keratinocyte proliferation and survival.

Betacoronaviruses, responsible for the “Severe Acute Respiratory Syndrome” (SARS) and the “Middle East Respiratory Syndrome” (MERS), use the spikes protruding from the virion envelope to attach and subsequently infect the host cells. The coronavirus spike (S) proteins contain receptor binding domains (RBD), allowing the specific recognition of either the dipeptidyl peptidase CD23 (MERS-CoV) or the angiotensin-converting enzyme ACE2 (SARS-Cov, SARS-CoV-2) host cell receptors. The heavily glycosylated S protein includes both complex and high-mannose type N-glycans that are well exposed at the surface of the spikes. A detailed analysis of the carbohydrate-binding specificity of mannose-binding lectins from plants, algae, fungi, and bacteria, revealed that, depending on their origin, they preferentially recognize either complex type N-glycans, or high-mannose type N-glycans. Since both complex and high-mannose glycans substantially decorate the S proteins, mannose-specific lectins are potentially useful glycan probes for targeting the SARS-CoV, MERS-CoV, and SARS-CoV-2 virions. Mannose-binding legume lectins, like pea lectin, and monocot mannose-binding lectins, like snowdrop lectin or the algal lectin griffithsin, which specifically recognize complex N-glycans and high-mannose glycans, respectively, are particularly adapted for targeting coronaviruses. The biomedical prospects of targeting coronaviruses with mannose-specific lectins are wide-ranging including detection, immobilization, prevention, and control of coronavirus infection.