Structural and functional analysis of Cyanovirin-N homologs: Carbohydrate binding affinities and antiviral potential of cyanobacterial peptides

Cyanobacteria, a group of photosynthetic prokaryotes, can sinthesize several substances due to their secondary metabolism, with notable properties, such as Cyanovirin-N(CVN), a carbohydrate-binding lectin, that exhibits antiviral activity against several pathogens, due to its ability to bind viral surface carbohydrates such as mannose, thus interfering with the viral entry on the cell. CVN has been described in several cyanobacterial strains and shows biotechnological potential for the development of drugs of pharmaceutical interest. This study focuses on the genomic exploration and characterization of Cyanovirin-N homologs to assess the conservation of carbohydrate-binding affinity within the group. The analysis of their antiviral properties was carried out using bioinformatics tools to study protein models through an in silico pipeline, following the steps of genomic prospection on public databases, homology modeling, docking, molecular dynamics and energetic analysis. Mannose served as the reference ligand, and the lectins' binding affinity with mannose was assessed across Cyanovirin-N homologs. Genomic mining identified 33 cyanobacterial lectin sequences, which underwent structural and functional characterization. The results obtained from this work indicate strong carbohydrate affinity on several homologs, pointing to the conservation of antiviral properties alongside the group. However, this affinity was not uniformly distributed among sequences, exhibiting significant heterogeneity in binding site residues, suggesting potential multi-ligand binding capabilities on the Cyanovirin-N homologs group. Studies focused on the properties involved in these molecules and the investigation of the genetic diversity of Cyanovirin-N homologs could provide valuable insights into the discovery of new drug candidates, harvesting the potential of bioinformatics for large-scale functional and structural analysis.

Glycan-directed SARS-CoV-2 inhibition by leek extract and lectins with insights into the mode-of-action of Concanavalin A

Four years after its outbreak, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains a global challenge for human health. At its surface, SARS-CoV-2 features numerous extensively glycosylated spike proteins. This glycan coat supports virion docking and entry into host cells and at the same time renders the virus less susceptible to neutralizing antibodies. Given the high genetic plasticity of SARS-CoV-2 and the rapid emergence of immune escape variants, targeting the glycan shield by carbohydrate-binding agents emerges as a promising strategy. However, the potential of carbohydrate-targeting reagents as viral inhibitors remains underexplored. Here, we tested seven plant-derived carbohydrate-binding proteins, called lectins, and one crude plant extract for their antiviral activity against SARS-CoV-2 in two types of human lung cells: A549 cells ectopically expressing the ACE2 receptor and Calu-3 cells. We identified three lectins and an Allium porrum (leek) extract inhibiting SARS-CoV-2 infection in both cell systems with selectivity indices (SI) ranging between >2 and >299. Amongst these, the lectin Concanavalin A (Con A) exerted the most potent and broad activity against a panel of SARS-CoV-2 variants. We used multiplex super-resolution microscopy to address lectin interactions with SARS-CoV-2 and its host cells. Notably, we discovered that Con A not only binds to SARS-CoV-2 virions and their host cells, but also causes SARS-CoV-2 aggregation. Thus, Con A exerts a dual mode-of-action comprising both, antiviral and virucidal, mechanisms. These results establish Con A and other plant lectins as candidates for COVID-19 prevention and basis for further drug development.

Lectins as the prominent potential to deliver bioactive metal nanoparticles by recognizing cell surface glycans

Lectins are renowned for recognizing specific carbohydrates, but there is evidence that they can bind to other endogenous ligands. Therefore, lectin can be used as a carrier to recognize glycoconjugates on the cell surface. The anticancer, antibacterial, and immunomodulatory properties of some lectins are established. Metal nanoparticles (MNPs) have been used in various fields recently, but their documented toxicity has raised questions about their suitability for biomedical uses. The advantages of MNPs can be realized if we deliver the NPs to the site of action; as a result, NPs may achieve greater therapeutic efficiency at lower doses with less toxicity. The use of carbohydrate specificity by lectin MNPs conjugates for diagnostics and therapeutics was addressed. The review summarised the multidimensional application of lectins and described their potential for delivery of MNPs in future drug development.

Chemical biology tools to probe bacterial glycans

Bacterial cells are covered by a complex carbohydrate coat of armor that allows bacteria to thrive in a range of environments. As a testament to the importance of bacterial glycans, effective and heavily utilized antibiotics including penicillin and vancomycin target and disrupt the bacterial glycocalyx. Despite their importance, the study of bacterial glycans lags far behind their eukaryotic counterparts. Bacterial cells use a large palette of monosaccharides to craft glycans, leading to molecules that are significantly more complex than eukaryotic glycans and that are refractory to study. Fortunately, chemical tools designed to probe bacterial glycans have yielded insights into these molecules, their structures, their biosynthesis, and their functions.

Secondary sites of the C-type lectin-like fold

C-type lectins are a large superfamily of proteins involved in a multitude of biological processes. In particular, their involvement in immunity and homeostasis has rendered them attractive targets for diverse therapeutic interventions. They share a characteristic C-type lectin-like domain whose adaptability enables them to bind a broad spectrum of ligands beyond the originally defined canonical Ca2+-dependent carbohydrate binding. Together with variable domain architecture and high-level conformational plasticity, this enables C-type lectins to meet diverse functional demands. Secondary sites provide another layer of regulation and are often intricately linked to functional diversity. Located remote from the canonical primary binding site, secondary sites can accommodate ligands with other physicochemical properties and alter protein dynamics, thus enhancing selectivity and enabling fine-tuning of the biological response. In this review, we outline the structural determinants allowing C-type lectins to perform a large variety of tasks and to accommodate the ligands associated with it. Using the six well-characterized Ca2+-dependent and Ca2+-independent C-type lectin receptors DC-SIGN, langerin, MGL, dectin-1, CLEC-2 and NKG2D as examples, we focus on the characteristics of non-canonical interactions and secondary sites and their potential use in drug discovery endeavors.

Lectin-mediated, time-efficient, and high-yield sorting of different morphologically intact nephron segments

The kidney is a highly complex organ equipped with a multitude of miniscule filter-tubule units called nephrons. Each nephron can be subdivided into multiple segments, each with its own morphology and physiological function. To date, conventional manual approaches to isolate specific nephron segments are very laborious, time-consuming, often limited to only a specific segment, and typically have low yield. Here, we describe a novel, unconventional method that is superior in many aspects to previous protocols by combining low-cost fluorophore-conjugated lectins or agglutinins (Flaggs) with flow sorting. This allows the simultaneous separation of different nephron segments with preserved 3D morphology from mouse or human samples in under 3 h. Using a 200-µm nozzle and 5 psi, glomeruli, proximal, or distal convoluted tubules are sorted with Cy3-labeled Sambucus Nigra agglutinin (SNA-Cy3), Fluorescein-labeled Lotus Tetragonolobus lectin (LTL-FITC), or Pacific Blue-labeled soybean agglutinin (SBA-PB), respectively. Connecting tubules and collecting ducts are sorted by double-positive SBA-PB and SNA-Cy3 signals, while thick ascending limb segments are characterized by the absence of any Flaggs labeling. From two mouse kidneys, this yields 37-521 ng protein/s or 0.71-16.71 ng RNA/s, depending on the specific nephron segment. The purity of sorted segments, as assessed by mRNA expression level profiling of 15 genes, is very high with a 96.1-fold median enrichment across all genes and sorted segments. In summary, our method represents a simple, straightforward, cost-effective, and widely applicable tool yielding high amounts of pure and morphologically largely intact renal tubule materials with the potential to propel nephron segment-specific research.

Synthetic assembly of α-O-linked-type GlcNAc using polymer chemistry affords sugar clusters, which effectively bind to lectins

Fischer's glycoside synthesis was applied to linker precursor alcohols of two different lengths having appropriate alkane chains to obtain the corresponding α-glycoside and it was found to be applicable with moderate yields. Water-soluble glycomonomers were systematically prepared from N-acetyl-d-glucosamine (GlcNAc) by introducing two kinds of alcohols having different methylene lengths. Typical radical polymerizations of the glycomonomers with acrylamide as a modulator for control of the distance between carbohydrate residues in water in the presence of ammonium persulfate (APS)-N,N,N',N'-tetramethylethylenediamine (TEMED) gave a series of glycopolymers with various α-glycoside-type GlcNAc residue densities. Fluorometric analysis of the interaction of wheat germ agglutinin (WGA) with the glycopolymers was performed and the results showed unique binding specificities based on structural differences.

Galectin-9 is a target for the treatment of cancer: A patent review

Galectins, which correspond to a group of proteins capable of recognizing and reversibly binding to β-galactoside carbohydrates, have been the subject of innovation and development of technological products. Galectins play biological roles, such as cell proliferation and apoptosis, and some studies showed differences in the concentrations of galectins dispersed in serum of patients with cancer. For this reason, different studies have evaluated the biotechnological potential of these proteins as biomarkers for the prognosis and/or diagnosis of physiological disorders. Thus, this review discusses recent technological advancements in targeting galectins for the treatment of cancer and using galectins for cancer prognosis and diagnosis. Data mining was performed using the search descriptors "Galectin 9* and cancer*" and the ESPACENET and Cortellis Drug Discovery Intelligence (CDDI) databases. PRISMA guidelines were followed as a basis for literature review which aimed to conduct a systematic study of galectin-9 patents related to cancer prognosis, diagnosis and treatment. Results showed the importance of galectin-9 protein patents in furthering biomedical advancements in the global fight against cancer.

Reversal mechanism of multidrug-resistant cancer cells by lectin as chemo-adjuvant and targeted therapy- a systematic review

BACKGROUND

Cancer is characterized as the leading cause of death, and the susceptibility of cancer cells to develop resistance due to long-term exposure to complementary chemotherapeutic treatment is referred to as multidrug resistance cancer cells (MDRC), which is a significant obstacle in the treatment of malignancies. Since complementary medicine lost its effectiveness, the development of potential alternative and novel therapeutic approaches has been elevated to a top priority in recent years. In this context, a bioactive protein lectin from plant and animal sources exhibits an invaluable source of anticancer agents with vast therapeutic potential.

PURPOSE

This manuscript's primary purpose is to enlighten the evidence-based (from 1986 to 2022) possible molecular mechanism of alternative treatment approaches using lectins over the complementary medicines used for cancer treatment.

METHODS

The PRISMA rules have been followed properly and qualitative and quantitative data are synthesized systematically. Articles were identified based on Clinical and preclinical reports published on lectin that investigated the in-depth cellular mechanisms, of reverse drug integrative oncology, as a nano-carried targeted delivery. Articles were systematically screened from 1986 to 2022 and selected based on electronic database searches, Medline (PubMed), Google Scholar, Web of Science, Encyclopaedias, Scopus, and ClinicalTrials.gov database.

RESULTS

The search turned up 4,212 publications from 38 different nations, of which 170 reference articles were used in our analysis, in 16 combination therapy and their mode of action, and 27 clinical trial studies including dosage and mechanism of action were included. Reports from the 30 lectins belonging to 28 different families have been included. The reversal mechanism of lectin and alternative therapy against MDRC is critically screened and according to a few clinical and preclinical reports, lectin can suppress the overexpressing genes like P-53, EGFR, and P-gp, MRP, and ABC transporter proteins associated with intracellular transportation of drugs. Since, the drug efflux mechanism leads to MDRC, in this phenomenon, lectin plays a key role in reversing the efflux mechanism. Few preclinical reports have mentioned that lectin shows synergism in combination with complementary medicine and as a nano drug carrier helps to deliver to the targeted site.

CONCLUSION

We have discussed the alternative therapy using lectin and an in-depth insight into the reversal drug resistance mechanisms to combat MDRC cancer, enhance the efficacy, reduce toxicity and adverse events, and ensure targeted delivery, and their application in the field of cancer diagnosis and prognosis has been discussed. However, further investigation is necessary in drug development and clinical trials which could be helpful to elaborate the reversal mechanism and unlock newer treatment modalities in MDRC cancer.

Fluorogenic Photo-Crosslinking of Glycan-Binding Protein Recognition Using a Fluorinated Azido-Coumarin Fucoside

Glycan recognition by glycan-binding proteins is central to the biology of all living organisms. The efficient capture and characterization of relatively weak non-covalent interactions remains an important challenge in various fields of research. Photoaffinity labeling strategies can create covalent bonds between interacting partners, and photoactive scaffolds such as benzophenone, diazirines and aryl azides have proved widely useful. Since their first introduction, relatively few improvements have been advanced and products of photoaffinity labeling remain difficult to detect. We report a fluorinated azido-coumarin scaffold which enables photolabeling under fast and mild activation, and which can leave a fluorescent tag on crosslinked species. Coupling this scaffold to an α-fucoside, we demonstrate fluorogenic photolabeling of glycan-protein interactions over a wide range of affinities. We expect this strategy to be broadly applicable to other chromophores and we envision that such "fluoro-crosslinkers" could become important tools for the traceable capture of non-covalent binding events.

Multivalent lectin-carbohydrate interactions: Energetics and mechanisms of binding

The biological signaling properties of lectins, which are carbohydrate-binding proteins, are due to their ability to bind and cross-link multivalent glycoprotein receptors on the surface of normal and transformed cells. While the cross-linking properties of lectins with multivalent carbohydrates and glycoproteins are relatively well understood, the mechanisms of binding of lectins to multivalent glycoconjugates are less well understood. Recently, the thermodynamics of binding of lectins to synthetic clustered glycosides, a multivalent globular glycoprotein, and to linear glycoproteins (mucins) have been described. The results are consistent with a dynamic binding mechanism in which lectins bind and jump from carbohydrate to carbohydrate epitope in these molecules. Importantly, the mechanism of binding of lectins to mucins is similar to that for a variety of protein ligands binding to DNA. Recent analysis also shows that high-affinity lectin-mucin cross-linking interactions are driven by favorable entropy of binding that is associated with the bind and jump mechanism. The results suggest that the binding of ligands to biopolymers, in general, may involve a common mechanism that involves enhanced entropic effects which facilitate binding and subsequent complex formation including enzymology.

Differential cellular localization of lectins in the testes of dromedary camel (Camelus dromedarius) during active and inactive breeding seasons

The reproductive activity of the male dromedary camel (Camelus dromedarius) as a seasonal breeder is affected by various seasonal changes that reflect on the reproductive performance. In the current study, we explored a differential cellular localization of lectins in eight dromedary camel testes utilizing lectin histochemistry (LHC). The glycoconjugates' localizations were detected within the testicular tissue utilizing 13 biotin-labeled lectins (PNA, ConA, LCA, RCA120, GS IB4, WGA, BPL, DBA, ECA, PHA-E4, UEA-1, PTL-II, and SBA) distributed into six sets. The cellular structures revealed diverse lectins distribution that may reflect various glycoproteins' structures and their compositional modifications during spermatogenesis. Some of the investigated lectins were restricted to acrosomes of spermatids that will help study different stages during the spermatogenic cycle of dromedary camel, particularly PNA, and ECA. The statistical analysis showed a marked positive correlation between the response intensity of various lectins and the breeding season (P < 0.05). We can conclude that lectins have a fundamental role during camel spermatogenesis and are associated with the reproductive activity of dromedary camel.

Selective targeting of lectins and their macropinocytosis in urothelial tumours: translation from in vitro to ex vivo

Urinary bladder cancer can be treated by intravesical application of therapeutic agents, but the specific targeting of cancer urothelial cells and the endocytotic pathways of the agents are not known. During carcinogenesis, the superficial urothelial cells exhibit changes in sugar residues on the apical plasma membranes. This can be exploited for selective targeting from the luminal side of the bladder. Here we show that the plant lectins Jacalin (from Artocarpus integrifolia), ACA (from Amaranthus caudatus) and DSA (from Datura stramonium) selectively bind to the apical plasma membrane of low- (RT4) and high-grade (T24) cancer urothelial cells in vitro and urothelial tumours ex vivo. The amount of lectin binding was significantly different between RT4 and T24 cells. Endocytosis of lectins was observed only in cancer urothelial cells and not in normal urothelial cells. Transmission electron microscopy analysis showed macropinosomes, endosome-like vesicles and multivesicular bodies filled with lectins in RT4 and T24 cells and also in cells of urothelial tumours ex vivo. Endocytosis of Jacalin and ACA in cancer cells was decreased in vitro after addition of inhibitor of macropinocytosis 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and increased after stimulation of macropinocytosis with epidermal growth factor (EGF). Clathrin, caveolin and flotillin did not colocalise with lectins. These results confirm that the predominant mechanism of lectin endocytosis in cancer urothelial cells is macropinocytosis. Therefore, we propose that lectins in combination with conjugated therapeutic agents are promising tools for improved intravesical therapy by targeting cancer cells.

Design of Glycopolymers for Controlling the Interactions with Lectins

Carbohydrates are involved in life activities through the interactions with their corresponding proteins (lectins). Pathogen infection and the regulation of cell activity are controlled by the binding between lectins and glycoconjugates on cell surfaces. A deeper understanding of the interactions of glycoconjugates has led to the development of therapeutic and preventive methods for infectious diseases. Glycopolymer is one of the classes of the materials present multiple carbohydrates. The properties of glycopolymers can be tuned through the molecular design of the polymer structures. This review focuses on research over the past decade on the design of glycopolymers with the aim of developing inhibitors against pathogens and manipulator of cellular functions.

Glycosylation in extracellular vesicles: Isolation, characterization, composition, analysis and clinical applications

This review provides a comprehensive overview of our understanding of the role that glycans play in the formation, loading and release of extracellular vesicles (EVs). The capture of EVs (typically with a size of 100-200 nm) is described, including approaches based on glycan recognition with glycan-based analysis offering highly sensitive detection of EVs. Furthermore, detailed information is provided about the use of EV glycans and glycan processing enzymes as potential biomarkers, therapeutic targets or tools applied for regenerative medicine. The review also provides a short introduction into advanced methods for the characterization of EVs, new insights into the biomolecular corona covering EVs and bioanalytical tools available for glycan analysis.

Therapeutic potential of lectins in the treatment of breast cancer: A review

Breast cancer is one of the most common malignancies and the leading cause of cancer-related deaths in women. There are 3 major subtypes of breast cancer that are distinguished by expression of estrogen or progesterone receptors and ERBB2 gene amplification. The 3 subtypes have different risk profiles and treatment strategies. Abnormal glycosylation is thought to play an important role in the development of the tumorigenic and metastatic phenotype of breast cancer and resistance to therapy. They may also be a potentially attractive target for breast cancer treatment. Proteins such as lectins, a family of carbohydrate-binding proteins found in a variety of organisms from viruses to humans, can specifically interact with abnormally glycosylated carbohydrate residues in cancer cells and induce cytotoxic effects. In recent years, there has been a growing number of research addressing studies demonstrating their antitumorigenic and antimalignant effects. This review summarizes recent findings on lectins from plants, animals, fungi, and bacteria that are potentially therapeutic agents against breast cancer and outlines the basis of their mechanism of action.

Fucose as a nutrient ligand for Dikarya and a building block of early diverging lineages

Fucose is a deoxyhexose sugar present and studied in mammals. The process of fucosylation has been the primary focus in studies relating to fucose in animals due to the presence of fucose in Lewis antigens. Very few studies have reported its presence in Fungi, mostly in Mucoromycotina. The constitution of 25% and 12% of this sugar in the carbohydrates of cell wall in the respective Umbelopsis and Mucorales strains boosts the need to bridge the gap of knowledge on fucose metabolism across the fungal tree of life. In the absence of a network map involving fucose proteins, we carried out an in-silico approach to construct the fucose metabolic map in Fungi. We analyzed the taxonomic distribution of 85 protein families in Fungi including diverse early diverging fungal lineages. The expression of fucose-related protein-coding genes proteins was validated with the help of transcriptomic data originating from representatives of early diverging fungi. We found proteins involved in several metabolic activities apart from fucosylation such as synthesis, transport and binding. Most of the identified protein families are shared with Metazoa suggesting an ancestral origin in Opisthokonta. However, the overall complexity of fucose metabolism is greater in Metazoa than in Fungi. Massive gene loss has shaped the evolutionary history of these metabolic pathways, leading to a repeated reduction of these pathways in most yeast-forming lineages. Our results point to a distinctive mode of utilization of fucose among fungi belonging to Dikarya and the early diverging lineages. We speculate that, while Dikarya used fucose as a source of nutrients for metabolism, the early diverging group of fungi depended on fucose as a building block and signaling compound.

A not-glycosylated isoform of γ-conglutin, a hexameric glycoprotein of Lupinus albus seed, participates in the oligomerization equilibrium

γ-conglutin (γ-C) is a hexameric glycoprotein accumulated in lupin seeds and has long been considered as a storage protein. Recently, it has been investigated for its possible postprandial glycaemic regulating action in human nutrition and for its physiological role in plant defence. The quaternary structure of γ-C results from the assembly of six monomers in reversible pH-dependent association/dissociation equilibrium. Our working hypothesis was that the γ-C hexamer is made up of glycosylated subunits in association with not-glycosylated isoforms, that seem to have 'escaped' the correct glycosylation process in the Golgi. Here we describe the isolation of not-glycosylated γ-C monomers in native condition by two in tandem lectin-based affinity chromatography and the characterization of their oligomerization capacity. We report, for the first time, the observation that a plant multimeric protein may be formed by identical polypeptide chains that have undergone different post-translational modifications. All obtained considered, the results strongly suggest that the not-glycosylated isoform can also take part in the oligomerization equilibrium of the protein.

Integrating machine learning and electrochemistry to develop a glucose biosensor assembled with Ganoderma applanatum lectin

Fungal lectins have enormous biotechnological potential, but limited knowledge about their biochemical and biophysical features prevents their proper use. Herein, we report an innovative alternative to use Ganoderma applanatum lectin (GAL) as a glucose biorecognition element, after identifying the ideal electroanalytical conditions by machine learning studies performed with a homologous agglutinin from the same macrofungus. The research revealed that GAL has moderate resistance to pH (4-8) and temperature (20-60 °C) variations, but its hemagglutinating activity (376.5 HU mg^-1 GAL at 20 °C) was better conserved under physiological conditions. Integrating electrochemical data and semi-empirical molecular modeling, biocompatible and electrostatically favorable conditions were found to immobilize the lectin on Prussian blue-modified glassy carbon electrode, after thermal activation of the metal-complex film. The glucose dose-response relationship obtained with the developed biosensor, defined as GAL/ta-PB/GCE, showed a typical Hill equation correlation, suggesting electrodic interactions represented by a sigmoidal mathematical function. GAL/ta-PB/GCE achieved remarkable electroanalytical performance, with emphasis on the detection limit (10.2 pM) and sensitivity (0.012 µA µM^-1cm^-2). The biosensor was successfully used to quantify glucose in pharmaceutical formulations, reiterating that the association of theoretical and experimental information drives important advances in bioelectrochemical studies.

Endotheliochorial placental glycosylation reflects evolutionary divergence between Felidae species (Felis catus and Panthera leo) and Canidae (Canisfamiliaris)

Endotheliochorial cat (Felis catus) and lion (Panthera leo) term placentae and one 6 week placenta (term 60-63 days) from a dog (Canis familiaris) were stained with a panel of 24 lectins to compare glycosylation at the feto-maternal interface. Glycan expression in lion and cat placentae was very similar apart from the occurrence of terminal α-galactose in the lion trophoblast. The dog differed in several respects, particularly in the trophoblast, consistent with species-specific glycotypes differing according to the degree of their evolutionary divergence. The data suggest that evolutionary effects on the glycotype are most readily observed in trophoblast.

The glycobiology of plasmodium falciparum: New approaches and recent advances

Like any other microorganism, pathogenic protozoan parasites rely heavily on glycoconjugates and glycan binding proteins to protect themselves from the environment and to interact with their diverse hosts. A thorough comprehension of how glycobiology contributes to the survival and virulence of these organisms may reveal unknown aspects of their biology and may open much needed avenues for the design of new strategies against them. In the case of Plasmodium falciparum, which causes the vast majority of malaria cases and deaths, the restricted variety and the simplicity of its glycans seemed to confer limited significance to the role played by glycoconjugates in the parasite. Nonetheless, the last 10 to 15 years of research are revealing a clearer and more defined picture. Thus, the use of new experimental techniques and the results obtained provide new avenues for understanding the biology of the parasite, as well as opportunities for the development of much required new tools against malaria.

Fluorescent nanoprobes based on quantum dots conjugated to cramoll to assess surface carbohydrates of Aeromonas spp

The association of quantum dots (QDs) to carbohydrate-binding proteins - lectins - has revealed novel biotechnological strategies for glycobiology studies. Herein, carboxyl-coated QDs were conjugated by adsorption to Cramoll, a glucose/mannose lectin obtained from Cratylia mollis seeds. Then, the conjugates were optically characterized and used to evaluate the surface carbohydrate profiles of four Aeromonas species isolated from the tambaqui fish (Colossoma macropomum). All the Aeromonas cells were labeled by the conjugate. Inhibition assays with methyl-α-D-mannopyranoside and mannan were performed to confirm the labeling specificity. Cramoll-QDs conjugates presented high brightness and showed similar absorption and emission profiles compared to bare QDs. According to the labeling pattern of Aeromonas spp. by the conjugate, results suggested that A. jandaei and A. dhakensis strains may harbor a higher content of more complex glucose/mannose surface glycans, with more available sites for Cramoll-QDs interaction, than A. hydrophila and A. caviae. Noteworthy, the Cramoll-QDs conjugates demonstrated to be a potential tool for bacterial characterization based on superficial carbohydrate detection.

Fucose Binding Motifs on Mucin Core Glycopeptides Impact Bacterial Lectin Recognition

Mucin glycoproteins are essential components of the mucosal barrier, which protects the host from pathogens. Throughout evolution, bacteria have developed strategies to modulate and penetrate this barrier, and cause virulence by interacting with mucin O-glycans at the epithelial cell-surface. O-fucosylated glycan epitopes on mucins are key ligands of many bacterial lectins. Here, a chemoenzymatic synthesis strategy is described to prepare a library of fucosylated mucin core glycopeptides to enable studies of mucin-interacting and fucose-binding bacterial lectins. Glycan cores with biologically important Lewis and H-antigens were prepared decorating the peptide backbone at different sites and densities. The fucosylated mucin glycopeptides were applied in microarray binding studies to explore the importance of glycan core and peptide backbone presentation of these antigens in binding interactions with the P. aeruginosa lectin LecB and the C. difficile toxin A.

Tuning specificity and topology of lectins through synthetic biology

Lectins are non-immunoglobulin and non-catalytic glycan binding proteins that are able to decipher the structure and function of complex glycans. They are widely used as biomarkers for following alteration of glycosylation state in many diseases and have application in therapeutics. Controlling and extending lectin specificity and topology is the key for obtaining better tools. Furthermore, lectins and other glycan binding proteins can be combined with additional domains, providing novel functionalities. We provide a view on the current strategy with a focus on synthetic biology approaches yielding to novel specificity, but other novel architectures with novel application in biotechnology or therapy.

A review

Detailed characterization of protein (un)folding intermediates is crucial for understanding the (un)folding pathway, aggregation, stability and their functional properties. In recent years, stress-inducible lectins are being investigated with much interest. In plants phloem proteins PP1 and PP2 are major components of the phloem fluid. While PP1 is a structural protein, PP2 exhibits lectin activity, and was proposed to play key roles in wound sealing, anti-pathogenic activity, and transportation of various molecules including RNA within the plant. Cucurbitaceae fruits contain high concentrations of PP2 lectins, which recognize chitooligosaccharides with high specificity. Although the presence of PP2 lectins in the phloem exudate of Cucurbitaceae species was documented over 40 years ago, so far only a few proteins from this family have been purified and characterized in detail. This review summarizes the results of biophysical studies aimed at investigating the oligomeric status of these lectins, their thermal stability, structural perturbations caused by changes in pH and addition of chaotropic agents and characterization of intermediates observed in the unfolding process. The implications of these results in the functional roles played by PP2 type lectins in their native environment are discussed. Finally, perspectives for future biophysical research on these proteins are given.

The lectin from Schinus terebinthifolia leaf (SteLL) reduces immobility of mice on the tail suspension test dependent on the monoaminergic and nitric oxide signaling

Depression underlies a common psychiatric disorder that has been rising in the diagnosis of long-term disabilities worldwide. Natural products have been studied as an antidepressant and anxiolytic agents aiming to make available new options for the daily basis treatment of those psychological disorders. SteLL is a lectin extracted from Schinus terebinthifolia leaf that has been revealed as an antimicrobial, immunomodulatory, antitumor, and antinociceptive agent. Nonetheless, the efficacy of SteLL in the treatment of depression has not yet been explored. In view of this, the aim of this study was to investigate the effect of SteLL in an acute protocol for symptoms of depression using the tail suspension test (TST) to assess despair. Administration of SteLL (1, 2 e 4 mg/kg) significantly diminished the immobility time of animals in the TST and this anti-immobility action was dependent on the carbohydrate-recognizing domain (CRD) since the prior incubation with casein (an inhibitor of SteLL carbohydrate-binding property) blocked the effect. SteLL effect was also reversed by pre-treatment with pharmacological antagonists of α2-adrenoceptor, 5-HT2A/2C serotonin receptor, and D1 dopamine receptor as well as by a selective inhibitor of iNOS (aminoguanidine). l-arginine, a precursor of NO, potentiated SteLL anti-immobility effect. In a subacute evaluation, the anti-immobility effect of SteLL persisted after seven days of treatment. Our findings suggest a role of SteLL in the modulation of depression mostly through monoaminergic and nitric oxide signaling.

Lectin histochemistry reveals two cytotrophoblast differentiation pathways during placental development in the feline (Feliscatus)

INTRODUCTION

Placental glycosylation has been examined on eight feline placentae ranging from approximately 15 to 60 days post-conception as little is known about changes in glycan distribution in this species.

METHODS

Specimens were resin embedded and lectin histochemistry was applied to semi-thin sections using a panel of 24 lectins and an avidin-biotin revealing system.

RESULTS

Abundant tri-tetraantennary complex N-glycan and α-galactosyl residues found in the syncytium in early pregnancy were greatly reduced in mid-pregnancy, though retained at the invasion front in the syncytium (N-glycan) or cytotrophoblast layer (αGal). Some other glycans were also uniquely present in invading cells. Abundant polylactosamine was found in the infolding basal lamina of syncytiotrophoblast and the apical villous cytotrophoblast membrane. Syncytial secretory granules often clustered near the apical membrane abutting maternal vessels. Decidual cells selectively expressed β-galactosyl residues throughout pregnancy and highly branched N-glycan levels increased over time.

DISCUSSION

Glycan distribution changes significantly over pregnancy, probably relating to the development of transport and invasive properties of trophoblast which in the endotheliochorial placenta reaches the level of the maternal vessels. Highly branched complex N-glycans, often associated with invasive cells, N-Acetylgalactosamine and terminal α-galactosyl residues are present at the invasion front abutting the junctional zone of the endometrium. Abundant polylactosamine on the syncytiotrophoblast basal lamina may reflect the presence of specialised adhesive interactions, while clustering of glycosylated granules apically is probably associated with secretion and absorption of material via maternal vasculature. It is suggested that lamellar and invasive cytotrophoblast represent distinct differentiation pathways. 246 words.

Synthetic assembly of a series of glycopolymers having sialyl α2-3 lactose moieties connected with longer spacer arms

Glycopolymers having sialyl α2-3 lactose moieties via longer spacer arms were systematically prepared from the corresponding glycomonomers. Radical polymerization of glycomonomers gave a series of glycopolymers displaying various sugar densities. Fluorometric analyses of wheat germ agglutinin (WGA) against the glycopolymers were conducted and the results showed unique binding specificities on the basis of sugar densities.

The localization of Toll and Imd pathway and complement system components and their response to Vibrio infection in the nemertean Lineus ruber

BACKGROUND

Innate immunity is the first line of defense against pathogens. In animals, the Toll pathway, the Imd pathway, the complement system, and lectins are well-known mechanisms involved in innate immunity. Although these pathways and systems are well understood in vertebrates and arthropods, they are understudied in other invertebrates.

RESULTS

To shed light on immunity in the nemertean Lineus ruber, we performed a transcriptomic survey and identified the main components of the Toll pathway (e.g., myD88, dorsal/dif/NFκB-p65), the Imd pathway (e.g., imd, relish/NFκB-p105/100), the complement system (e.g., C3, cfb), and some lectins (FreD-Cs and C-lectins). In situ hybridization showed that TLRβ1, TLRβ2, and imd are expressed in the nervous system; the complement gene C3-1 is expressed in the gut; and the lectins are expressed in the nervous system, the blood, and the gut. To reveal their potential role in defense mechanisms, we performed immune challenge experiments, in which Lineus ruber specimens were exposed to the gram-negative bacteria Vibrio diazotrophicus. Our results show the upregulation of specific components of the Toll pathway (TLRα3, TLRβ1, and TLRβ2), the complement system (C3-1), and lectins (c-lectin2 and fred-c5).

CONCLUSIONS

Therefore, similarly to what occurs in other invertebrates, our study shows that components of the Toll pathway, the complement system, and lectins are involved in the immune response in the nemertean Lineus ruber. The presence of these pathways and systems in Lineus ruber, but also in other spiralians; in ecdysozoans; and in deuterostomes suggests that these pathways and systems were involved in the immune response in the stem species of Bilateria.

Combined Lectin- and Immuno-histochemistry (CLIH) for Fluorescence Microscopy

The function of glycoproteins depends both on their polypeptide chain and sugar residues. For detection and localization of glycoproteins in tissue sections, methods of immunohistochemistry (IHC) and lectin histochemistry (LHC) are usually used separately. For a better understanding of the expression and distribution of variants of glycoproteins, tissue sections can be analyzed by combined lectin- and immuno-histochemistry (CLIH). CLIH exploits the advantages of both IHC and LHC and can therefore contribute to research in glycobiology and other fields of cell biology. Since cancer transformation is accompanied by alterations in the glycosylation of some glycoproteins, CLIH could also be exploited for improved classification of cancers. The chapter considers how CLIH could be employed on paraffin sections and semithin cryosections for fluorescence microscopy. Five different protocols of CLIH are described in detail as well as appropriate negative controls.

The health-promoting potential of edible mushroom proteins

Edible mushrooms have been classified as "next-generation food" due to their high nutritional value coupled with their biological and functional potential. The most extensively studied and reported mushroom macromolecules are polysaccharides. However, macrofungi proteins and peptides are also a representative and significant bioactive group. Several factors such as species, substrate composition and harvest time significantly impact the mushroom protein content, typically ranging between 19 and 35% on a dry weight basis. Proteins work based on their shape and structure. Numerous extraction methods, including chemical and non-conventional, and their implications on protein yield and stability will be discussed. Beyond their biological potential, a great advantage of mushroom proteins is their uniqueness, as they often differ from animal, vegetable, and microbial proteins. According to recently published reports, the most relevant mushroom bioactive proteins and peptides include lectins, fungal immunomodulatory proteins, ubiquitin-like proteins, and proteins possessing enzymatic activity such as ribonucleases laccases, and other enzymes and ergothioneine. These are reported as antioxidant, antiviral, antifungal, antibacterial, antihypertensive, immunomodulatory, antitumour, antihypercholesterolemic or antihyperlipidemic, antidiabetic and anti-inflammatory properties, which improved proteins and peptides research interest and contributed to the increase of mushroom market value. This review provides an overview of the most relevant biochemical and biological properties of the main protein groups in edible mushrooms, explicitly focusing on their biomedical potential. Although mushrooms are a rich source of various proteins, many of these molecules have yet to be identified and characterised. Accordingly, it is crucial to identify and characterise new macromolecules of macrofungi origin, which opens an opportunity for further investigation to identify new bioactives for food, nutraceutical, or medicinal applications.

Variations in the carbohydrate expression pattern and in lesions of the uterine horns of BALB/c mice infected with different Tritrichomonas foetus isolates

Bovine tritrichomonosis, a sexually transmitted disease caused by the protozoan Tritrichomonas foetus, is characterized by producing reproductive alterations in cattle. Carbohydrates on the surface of the uterine epithelium are involved in the process of adhesion and colonization of the protozoan. The murine model has proved to be an inexpensive, practical and representative alternative to study the lesions produced in the natural host. For this work, during the first stage, 6-8 week old female BALB/c mice were inoculated with 24 different T. foetus isolates in order to classify them according to their pathogenicity. Then, seven isolates were selected and processed with lectin histochemistry to determine if the differences in pathogenicity corresponded to the changes found in the uterine carbohydrate expression pattern. In this work, we demonstrate the differences in the expression of the carbohydrate pattern between infected and uninfected mice. In addition, within the group of infected mice, differences were found in the degree of pathogenicity of the isolates, thus evidencing their biological variability.

A bispecific, crosslinking lectibody activates cytotoxic T cells and induces cancer cell death

BACKGROUND

Aberrant glycosylation patterns play a crucial role in the development of cancer cells as they promote tumor growth and aggressiveness. Lectins recognize carbohydrate antigens attached to proteins and lipids on cell surfaces and represent potential tools for application in cancer diagnostics and therapy. Among the emerging cancer therapies, immunotherapy has become a promising treatment modality for various hematological and solid malignancies. Here we present an approach to redirect the immune system into fighting cancer by targeting altered glycans at the surface of malignant cells. We developed a so-called "lectibody", a bispecific construct composed of a lectin linked to an antibody fragment. This lectibody is inspired by bispecific T cell engager (BiTEs) antibodies that recruit cytotoxic T lymphocytes (CTLs) while simultaneously binding to tumor-associated antigens (TAAs) on cancer cells. The tumor-related glycosphingolipid globotriaosylceramide (Gb3) represents the target of this proof-of-concept study. It is recognized with high selectivity by the B-subunit of the pathogen-derived Shiga toxin, presenting opportunities for clinical development.

METHODS

The lectibody was realized by conjugating an anti-CD3 single-chain antibody fragment to the B-subunit of Shiga toxin to target Gb3⁺ cancer cells. The reactive non-canonical amino acid azidolysine (AzK) was inserted at predefined single positions in both proteins. The azido groups were functionalized by bioorthogonal conjugation with individual linkers that facilitated selective coupling via an alternative bioorthogonal click chemistry reaction. In vitro cell-based assays were conducted to evaluate the antitumoral activity of the lectibody. CTLs, Burkitt´s lymphoma-derived cells and colorectal adenocarcinoma cell lines were screened in flow cytometry and cytotoxicity assays for activation and lysis, respectively.

RESULTS

This proof-of-concept study demonstrates that the lectibody activates T cells for their cytotoxic signaling, redirecting CTLs´ cytotoxicity in a highly selective manner and resulting in nearly complete tumor cell lysis-up to 93%-of Gb3⁺ tumor cells in vitro.

CONCLUSIONS

This research highlights the potential of lectins in targeting certain tumors, with an opportunity for new cancer treatments. When considering a combinatorial strategy, lectin-based platforms of this type offer the possibility to target glycan epitopes on tumor cells and boost the efficacy of current therapies, providing an additional strategy for tumor eradication and improving patient outcomes.

Structural and functional diversity of lectins associated with immunity in the marine shrimp Litopenaeusvannamei

Lectins are important pattern recognition receptors (PRRs) and their immunological action is related to the recognition of glycans present in the pathogen cells surface. The lectins described for Litopenaeus vannamei are divided into C-type, L-type and galectin, which are mainly expressed in hepatopancreas and hemocytes. They are involved in several immune response pathways, such as phagocytosis, hemocytes recruitment, prophenoloxidase activation, and gene regulation. Although lectins have multiple immune functions, most experimental challenges focus only on WSSV and Vibrio sp. This article is a detailed review on the role of lectins in L. vannamei immune system, bringing together information on molecular structure, temporal and special expression and immune function, highlighting the wide participation of these molecules in shrimp innate immune system.

Neuroprotective Effect of Exogenous Galectin-1 in Status Epilepticus

Intrahippocampal pilocarpine microinjection (H-PILO) induces status epilepticus (SE) that can lead to spontaneous recurrent seizures (SRS) and neurodegeneration in rodents. Studies using animal models have indicated that lectins mediate a variety of biological activities with neuronal benefits, especially galectin-1 (GAL-1), which has been identified as an effective neuroprotective compound. GAL-1 is associated with the regulation of cell adhesion, proliferation, programmed cell death, and immune responses, as well as attenuating neuroinflammation. Here, we administrated GAL-1 to Wistar rats and evaluated the severity of the SE, neurodegenerative and inflammatory patterns in the hippocampal formation. Administration of GAL-1 caused a reduction in the number of class 2 and 4 seizures, indicating a decrease in seizure severity. Furthermore, we observed a reduction in inflammation and neurodegeneration 24 h and 15 days after SE. Overall, these results suggest that GAL-1 has a neuroprotective effect in the early stage of epileptogenesis and provides new insights into the roles of exogenous lectins in temporal lobe epilepsy (TLE).

Plant lectins: A new antimicrobial frontier

Pathogenic bacteria, viruses, fungi, parasites, and other microbes constantly change to ensure survival. Several pathogens have adopted strict and intricate strategies to fight medical treatments. Many drugs, frequently prescribed to treat these pathogens, are becoming obsolete and ineffective. Because pathogens have gained the capacity to tolerate or resist medications targeted at them, hence the term antimicrobial resistance (AMR), in that regard, many natural compounds have been routinely used as new antimicrobial agents to treat infections. Thus, plant lectins, the carbohydrate-binding proteins, have been targeted as promising drug candidates. This article reviewed more than 150 published papers on plant lectins with promising antibacterial and antifungal properties. We have also demonstrated how some plant lectins could express a synergistic action as adjuvants to boost the efficacy of obsolete or abandoned antimicrobial drugs. Emphasis has also been given to their plausible mechanism of action. The study further reports on the immunomodulatory effect of plant lectins and how they boost the immune system to curb or prevent infection.

Bioactive components of Laetiporus species and their pharmacological effects

Laetiporus species are brown rot fungi belonging to the order Polyporales in the division Basidiomycota. These species produce a variety of metabolites and provide a great source of natural material for the screening of medicinally active natural products or their derivatives. This review summarizes the research progress on bioactive metabolites of Laetiporus species up to April 2022, including biological macromolecules, for instance, polysaccharides and lectins, as well as 80 reported small molecule chemical components (15 sterols, 29 triterpenes, 10 sesquiterpenes, 5 polyenes, 10 volatile compounds, and 11 other compounds). These metabolites exhibit antimicrobial, anticancer, antioxidant, hepatoprotective, anti-inflammatory, and antidiabetic activities. Genome mining predicted 23 terpene synthases, 7 polyketide synthases, and 9 non-ribosomal peptide synthases involved in bioactive metabolites biosynthesis, which were analyzed by antiSMASH in L. sulphureus genome. This review will provide a basis for the biosynthesis of active components in Laetiporus species and a reference for the research of medical precursors. KEY POINTS: • The mini-review summarized 80 secondary metabolites of Laetiporus spp. • The main pharmacological activities of Laetiporus spp. were summarized. • Biosynthetic genes of terpenoids, polyketides, and non-ribosomal peptides were also summarized.

The Argentine mistletoes Ligaria cuneifolia (Ruiz & Pav.) Tiegh (Loranthaceae) and Phoradendron liga (Gillies ex Hook. & Arn.) Eichler (Santalaceae). Thirty years of research

Ligaria cuneifolia (Ruiz & Pav.) Tiegh (Loranthaceae) and Phoradendron liga (Gillies ex Hook. & Arn.) Eichler (Santalaceae) are regarded as Argentine mistletoes based on their similarities with the European counterpart, Viscum album L. (Santalaceae). These two species are the most used medicinal plants to treat high blood pressure in the Argentinian population. To provide scientific grounds to their traditional use and therapeutic potential, they were selected as herbal drug candidates. The main findings would support the anti-hypertensive action, the anticholesterolemic and antioxidant features of L. cuneifolia, and immunomodulatory properties for both species. Quercetin-O-glycosides, galloyl glycosides, and proanthocyanidins are present in L. cuneifolia while P. liga shows C-glycosyl flavones and 3-deoxyproanthocyanidins. This review summarizes the phytochemical characterization, medicinal properties and reveals promising results warranting future efforts for further investigation.

Proceedings of workshop: "Neuroglycoproteins in health and disease", INNOGLY cost action

The Cost Action "Innovation with glycans: new frontiers from synthesis to new biological targets" (INNOGLY) hosted the Workshop "Neuroglycoproteins in health and disease", in Alicante, Spain, on March 2022. This event brought together an european group of scientists that presented novel insights into changes in glycosylation in diseases of the central nervous system and cancer, as well as new techniques to study protein glycosylation. Herein we provide the abstracts of all the presentations.

Multicomponent reaction derived small di- and tri-carbohydrate-based glycomimetics as tools for probing lectin specificity

Lectins, carbohydrate-binding proteins, play important functions in all forms of life from bacteria and viruses to plants, animals, and humans, participating in cell-cell communication and pathogen binding. In an attempt to modify lectin functions, artificial lectin ligands were made usually as big dendrimeric or cluster multivalent glycomimetic structures. Here we synthesized a novel set of glycomimetic ligands through protection/deprotection multicomponent reactions (MCR) approach. Multivalent di-and tri-carbohydrate glycomimetics containing D-fructose, D-galactose, and D-allose moieties were prepared in 63-96% yield. MCR glycomimetics demonstrated different binding abilities for plant lectins Con A and UEA I, and human galectin-3. Information gained about the influence of molecule structure, multivalency and optical purity on the lectin binding ability can be used in lectin detection and sensitivity measurements to further facilitate understanding of carbohydrate recognition process.

Genome-wide screening of lectin putative genes from Sorghum bicolor L., distribution in QTLs and a probable implications of lectins in abiotic stress tolerance

BACKGROUND

Sorghum bicolor is one of the most important crops worldwide with the potential to provide resilience when other economic staples might fail against the continuous environmental changes. Many physiological, developmental and tolerance traits in plants are either controlled or influenced by lectins; carbohydrate binding proteins. Hence, we aimed at providing a comprehensive in silico account on sorghum's lectins and study their possible implication on various desired agronomical traits.

RESULTS

We have searched sorghum's genome from grain and sweet types for lectins putative genes that encode proteins with domains capable of differentially binding carbohydrate moieties and trigger various physiological responses. Of the 12 known plant lectin families, 8 were identified regarding their domain architectures, evolutionary relationships, physiochemical characteristics, and gene expansion mechanisms, and they were thoroughly addressed. Variations between grain and sweet sorghum lectin homologs in term of the presence/absence of certain other joint domains like dirigent and nucleotide-binding adaptor shared by APAF-1, R-proteins, and CED-4 (NB-ARC) indicate a possible neofunctionalization. Lectin sequences were found to be preferentially overrepresented in certain quantitative trait loci (QTLs) related to various traits under several subcategories such as cold, drought, salinity, panicle/grain composition, and leaf morphology. The co-localization and distribution of lectins among multiple QTLs provide insights into the pleiotropic effects that could be played by one lectin gene in numerous traits.

CONCLUSION

Our study offers a first-time inclusive details on sorghum lectins and their possible role in conferring tolerance against abiotic stresses and other economically important traits that can be informative for future functional analysis and breeding studies.

One, two, many: Strategies to alter the number of carbohydrate binding sites of lectins

Carbohydrates are more than an energy-storage. They are ubiquitously found on cells and most proteins, where they encode biological information. Lectins bind these carbohydrates and are essential for translating the encoded information into biological functions and processes. Hundreds of lectins are known, and they are found in all domains of life. For half a century, researchers have been preparing variants of lectins in which the binding sites are varied. In this way, the traits of the lectins such as the affinity, avidity and specificity towards their ligands as well as their biological efficacy were changed. These efforts helped to unravel the biological importance of lectins and resulted in improved variants for biotechnological exploitation and potential medical applications. This review gives an overview on the methods for the preparation of artificial lectins and complexes thereof and how reducing or increasing the number of binding sites affects their function.

The role of WSC domain-containing protein encoding gene AOL_s00043g401 in the growth and nematode trapping of Arthrobotrys oligospora

Arthrobotrys oligospora is a model nematode-trapping fungus that has been extensively investigated to understand the interactions between fungi and nematodes. Nematode capture by A. oligospora is a complex process in which recognition of nematodes is generally believed to be mediated by lectins from the fungi. Lectins are a group of carbohydrate-binding proteins that widely exist in microorganisms and contain specific glycosylation recognition domains. In this work, we report the effect of a putative WSC domain-containing protein encoding gene AOL_s00043g401 (g401) on the growth and nematode-trapping of A. oligospora. The g401 gene was knocked out using the homologous recombination approach, and the △g401 mutant strain was then evaluated for its growth rate, conidial yield and germination rate, adaptation to environmental stresses, and nematocidal activity. Interestingly, the deletion of the putative lectin gene g401 had no significant effect on saprophytic growth, conidial yield and germination rate, responses to high salt, surfactant, and strong oxidative environments, as well as nematode-trapping efficiency of A. oligospora. We speculate that this phenomenon might have been caused by an intrinsic genetic compensation of the g401 in this fungus. For instance, more copies of WSC domain encoding genes or PQQ-DH domain encoding genes were found in the genome of A. oligospora. These findings provide further experimental evidence on the effect of lectin-related functional proteins in A. oligospora on nematode capture and will help further analyze their potential roles in the biological control of nematodes in the future.

Lectins and lectibodies: potential promising antiviral agents

In nature, lectins are widely dispersed proteins that selectively recognize and bind to carbohydrates and glycoconjugates via reversible bonds at specific binding sites. Many viral diseases have been treated with lectins due to their wide range of structures, specificity for carbohydrates, and ability to bind carbohydrates. Through hemagglutination assays, these proteins can be detected interacting with various carbohydrates on the surface of cells and viral envelopes. This review discusses the most robust lectins and their rationally engineered versions, such as lectibodies, as antiviral proteins. Fusion of lectin and antibody’s crystallizable fragment (Fc) of immunoglobulin G (IgG) produces a molecule called a “lectibody” that can act as a carbohydrate-targeting antibody. Lectibodies can not only bind to the surface glycoproteins via their lectins and neutralize and clear viruses or infected cells by viruses but also perform Fc-mediated antibody effector functions. These functions include complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), and antibody-dependent cell-mediated phagocytosis (ADCP). In addition to entering host cells, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein S1 binds to angiotensin-converting enzyme 2 (ACE2) and downregulates it and type I interferons in a way that may lead to lung disease. The SARS-CoV-2 spike protein S1 and human immunodeficiency virus (HIV) envelope are heavily glycosylated, which could make them a major target for developing vaccines, diagnostic tests, and therapeutic drugs. Lectibodies can lead to neutralization and clearance of viruses and cells infected by viruses by binding to glycans located on the envelope surface (e.g., the heavily glycosylated SARS-CoV-2 spike protein).

Bacterial Microarrays for Examining Bacterial Glycosignatures and Recognition by Host Lectins

The surface of bacteria displays diverse carbohydrate structures that may significantly differ among bacteria with the same cell wall architecture and even among strains of a given bacterial species. These structures are often recognized by lectins of the innate immune system for triggering defense responses, although some bacterial pathogens exploit recognition by host lectins for favoring infection. Bacterial microarrays are a useful tool for profiling accessible bacterial surface glycans and for exploring their recognition by innate immune lectins. The use of array-printed bacterial cells enables evaluation of the recognition of the glycan epitopes in their natural presentation, i.e., preserving their real density and accessibility. Glycosylation patterns of bacterial surfaces can be examined by testing the binding to the bacterial arrays of a panel of lectins with known carbohydrate-binding preferences, and the recognition of surface glycans by innate immune lectins can easily be assessed using similar binding assays.

Comparative lectin histochemistry on the murine respiratory tract and primary olfactory pathway using a fully automated staining procedure

Lectins are naturally occurring molecules which bind to specific carbohydrates of glycoconjugates. The binding specificity of lectins can therefore be used to specifically elucidate the glycosylation pattern in various tissues. While lectin histochemistry is usually carried out manually on single slides, a fully automated immunostaining system offers an easy, standardized, and high throughput system. In this study lectin histochemistry was implemented and optimized on a fully automated immunostaining system to investigate glycosylation patterns in the murine respiratory tract and the primary olfactory pathway. We tested 22 commercially available biotinylated lectins for their labelling-profiles to specifically identify morphologic structures. The results showed that lectin staining profiles using the implemented protocol on the automated system were constant and suitable for high throughput morphological studies. Further, the morphological evaluation of the stained slides revealed a complete characterization of the murine respiratory tract and primary olfactory pathway including the lectin binding profiles for the olfactory bulb, the vomeronasal organ and the nasal-associated lymphoid tissue.

General Strategies for Glycan Microarray Data Processing and Analysis

Glycan microarrays provide a high-throughput technology for rapidly profiling interactions between carbohydrates and glycan-binding proteins (GBPs). Use of glycan microarrays involves several general steps, including construction of the microarray, carrying out the assay, detection of binding events, and analysis of the results. While multiple platforms have been developed to construct microarrays, most utilize fluorescence for detection of binding events. This chapter describes methods to acquire and process microarray images, including generating GAL files, imaging of the slide, aligning the grid, detecting problematic spots, and evaluating the quality of the data. The chapter focuses on processing our neoglycoprotein microarrays, but many of the lessons we have learned are applicable to other array formats.

Anti-inflammatory and anti-necrotic effects of lectins from Canavalia ensiformis and Canavalia brasiliensis in experimental acute pancreatitis

Lectins isolated from Canavalia ensiformis (ConA) and Canavalia brasiliensis (ConBr) are promising molecules to prevent cell death. Acute pancreatitis, characterized by acinar cell necrosis and inflammation, presents significant morbidity and mortality. This study has investigated the effects of ConA and ConBr in experimental acute pancreatitis and pancreatic acinar cell death induced by bile acid. Pancreatitis was induced by retrograde pancreatic ductal injection of 3% sodium taurocholate (Na-TC) in male Swiss mice. ConA or ConBr (0.1, 1 or 10 mg/kg) were intravenously applied to mice 1 h and 12 h after induction. After 24 h, the severity of pancreatitis was evaluated by serum amylase and lipase, histopathological changes and myeloperoxidase assay. Pancreatic acinar cells were incubated with ConA (200 µg/ml) or ConBr (200 µg/ml) and taurolithocholic acid 3-sulfate (TLCS; 500 µM). Necrosis and changes in mitochondrial membrane potential (ΔѰm) were detected by fluorescence confocal microscopy. Treatment (post-insult) with ConA and ConBr decreased pancreatic damage caused by retrograde injection of Na-TC in mice, reducing pancreatic neutrophil infiltration, edema and necrosis. In addition, ConA and ConBr decreased pancreatic acinar cell necrosis and depolarization of ΔѰm caused by TLCS. The inhibition of necrosis was prevented by the lectin domain blockade. In conclusion, ConA and ConBr markedly inhibited in vitro and in vivo damage, effects partly dependent on the interaction with mannose residues on acinar cells. These data support the potential application of these proteins for treatment of acute pancreatitis.

Defective IGF-1 prohormone N-glycosylation and reduced IGF-1 receptor signaling activation in congenital disorders of glycosylation

The insulin-like growth factor-1 (IGF-1) signaling pathway is crucial for the regulation of growth and development. The correct processing of the IGF-1Ea prohormone (proIGF-1Ea) and the IGF-1 receptor (IGF-1R) peptide precursor requires proper N-glycosylation. Deficiencies of N-linked glycosylation lead to a clinically heterogeneous group of inherited diseases called Congenital Disorders of Glycosylation (CDG). The impact of N-glycosylation defects on IGF-1/IGF-1R signaling components is largely unknown. In this study, using dermal fibroblasts from patients with different CDG [PMM2-CDG (n = 7); ALG3-CDG (n = 2); ALG8-CDG (n = 1); GMPPB-CDG (n = 1)], we analyzed the glycosylation pattern of the proIGF-1Ea, IGF-1 secretion efficiency and IGF-1R signaling activity. ALG3-CDG, ALG8-CDG, GMPPB-CDG and some PMM2-CDG fibroblasts showed hypoglycosylation of the proIGF-1Ea and lower IGF-1 secretion when compared with control (CTR). Lower IGF-1 serum concentration was observed in ALG3-CDG, ALG8-CDG and in some patients with PMM2-CDG, supporting our in vitro data. Furthermore, reduced IGF-1R expression level was observed in ALG3-CDG, ALG8-CDG and in some PMM2-CDG fibroblasts. IGF-1-induced IGF-1R activation was lower in most PMM2-CDG fibroblasts and was associated with decreased ERK1/2 phosphorylation as compared to CTR. In general, CDG fibroblasts showed a slight upregulation of Endoplasmic Reticulum (ER) stress genes compared with CTR, uncovering mild ER stress in CDG cells. ER-stress-related gene expression negatively correlated with fibroblasts IGF-1 secretion. This study provides new evidence of a direct link between N-glycosylation defects found in CDG and the impairment of IGF-1/IGF-1R signaling components. Further studies are warranted to determine the clinical consequences of reduced systemic IGF-1 availability and local activity in patients with CDG.

Probing the glycans accessibility in the nanoparticle biomolecular corona

HYPOTHESIS

Following blood administration, the pristine surface of nanoparticles (NPs) associates with biomolecules from the surrounding environment forming the so-called "biomolecular corona". It is well accepted that the biomolecular corona dramatically affects the NP fate in the biological medium while the pristine surface is no longer available for binding. Recent studies have shown that the glycans associated with the proteins forming the corona have a role in the NP interaction with macrophages, but the glycan identities remain unknown. We aim here to identify the glycan composition of the biomolecular corona and to assess the role of these glycans in the interaction of the proteins from the corona with glycan binding biomolecules, such as lectins.

EXPERIMENTS

In this study, we have characterized the biomolecular corona of citrate stabilised gold NPs after exposure of the NPs to blood plasma at two different plasma concentrations, mimicking the in vitro and in vivo conditions. We have extensively characterized the biomolecular corona using HILIC chromatography and shotgun proteomics. Following this, a lectin binding assay was carried out using Dynamic Light Scattering (DLS) and Fluorescence Correlation Spectroscopy (FCS) to assess whether proteins with known affinity towards specific glycans would bind to the corona.

FINDINGS

Our findings highlighted that the protein corona composition is dependent on the exposing conditions. However, under both plasma concentrations, the biantennary sialylated glycans (A2G2S2) are enriched. DLS and FCS confirmed that the glycans are accessible for binding as the corona interacts with lectins with known affinity towards terminal sialic acids and the enzymatic removal of the glycans leads to a decrease in lectin affinity. This study shows for the first time that the glycans are present in the corona and that they could potentially be responsible for the modulation of NP biological processes as they can directly engage with glycan binding receptors that are highly expressed in an organism.