A Rapid and Facile Purification Method for Glycan-Binding Proteins and Glycoproteins

Glycosylated proteins, namely glycoproteins and proteoglycans (collectively called glycoconjugates), are indispensable in a variety of biological processes. The functions of many glycoconjugates are regulated by their interactions with another group of proteins known as lectins. In order to understand the biological functions of lectins and their glycosylated binding partners, one must obtain these proteins in pure form. The conventional protein purification methods often require long times, elaborate infrastructure, costly reagents, and large sample volumes. To minimize some of these problems, we recently developed and validated a new method termed capture and release (CaRe). This method is time-saving, precise, inexpensive, and it needs a relatively small sample volume. In this approach, targets (lectins and glycoproteins) are captured in solution by multivalent ligands called target capturing agents (TCAs). The captured targets are then released and separated from their TCAs to obtain purified targets. Application of the CaRe method could play an important role in discovering new lectins and glycoconjugates. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Preparation of crude extracts containing the target proteins from soybean flour Alternate Protocol 1: Preparation of crude extracts from Jack bean meal Alternate Protocol 2: Preparation of crude extracts from the corms of Colocasia esculenta, Xanthosoma sagittifolium, and from the bulbs of Allium sativum Alternate Protocol 3: Preparation of Escherichia coli cell lysates containing human galectin-3 Alternate Protocol 4: Preparation of crude extracts from chicken egg whites (source of ovalbumin) Basic Protocol 2: Preparation of 2% (v/v) red blood cell suspension Basic Protocol 3: Detection of lectin activity of the crude extracts Basic Protocol 4: Identification of multivalent inhibitors as target capturing agents by hemagglutination inhibition assays Basic Protocol 5: Testing the capturing abilities of target capturing agents by precipitation/turbidity assays Basic Protocol 6: Capturing of targets (lectins and glycoproteins) in the crude extracts by target capturing agents and separation of the target-TCA complex from other components of the crude extracts Basic Protocol 7: Releasing the captured targets (lectins and glycoproteins) by dissolving the complex Basic Protocol 8: Separation of the targets (lectins and glycoproteins) from their respective target capturing agents Basic Protocol 9: Verification of the purity of the isolated targets (lectins or glycoproteins).

Purification and characterization of two new allergens from the salivary glands of the horsefly, Tabanus yao

BACKGROUND

Horsefly bite can cause allergic reactions in humans. There is no information about allergenic horsefly proteins.

OBJECTIVES

The current work aims to purify and characterize IgE-binding proteins from horsefly salivary glands.

METHODS

Two IgE-binding proteins, Tab a 1 and Tab a 2 with molecular weight of 26 and 35 kd, respectively, were purified and characterized from 60,000 pairs of horsefly salivary glands of Tabanus yao, respectively. Their primary sequences were determined by Edman degradation and cDNA cloning. Their allergenicity was examined using enzyme-linked immunosorbent assay (ELISA), ELISA inhibition tests, and immunoblots.

RESULTS

Immunoblotting demonstrated IgE binding by 32 and 34 of 37 (86.5% and 91.8%) subjects' sera to Tab a 1 and Tab a 2, respectively. They were identified as an antigen 5-related (Ag 5) protein and hyaluronidase, respectively. ELISA inhibitions of serum IgE reactivity to the horsefly salivary gland extract (SGE) using purified Tab a 1 and Tab a 2 were significant (about 45%). In addition, these proteins showed some IgE-binding capacity to sera of subjects with wasp sting allergy.

CONCLUSIONS

We have first identified and characterized two IgE-binding proteins, Tab a 1, an Ag 5-like protein and Tab a 2, a hyaluronidase, from the horsefly salivary glands. They appear to be of importance for the allergic reactions induced by horsefly bite. These allergens are thus not only found in stinging but also found in hematophagous insects. These results also provided support for the presence of the so-called wasp-horsefly syndrome (WHS).

Identification of Ige-binding proteins of raw and cooked extracts of Loligo edulis (white squid)

Allergy to different classes of mollusks, including squid, which are members of the class Cephalopods has been reported. Tropomyosin, a major muscle protein, is the only well-recognized allergen in squid. The aim of this study was to characterize IgE-binding proteins of local Loligo edulis (white squid) consumed in Malaysia. Protein profiles and IgE-binding proteins were detected by sodium dodecyl sulfate-polyacrylamide gel-electrophoresis (SDS-PAGE) and immunoblotting using sera from 23 patients with positive skin prick test to raw squid extract. SDS-PAGE of the raw extract exhibited 21 protein bands (10-170 kDa) but those ranging from 19 to 29 kDa and 41 to 94 kDa were not found in the cooked extract. Immunoblotting of raw extract demonstrated 16 IgE-binding bands, ranging from 13 to 170 kDa. A heat-resistant 36 kDa protein, corresponding to squid tropomyosin, was identified as the major allergen of both extracts. In addition, a 50 kDa heat-sensitive protein was shown to be a major allergen of the raw extract. Our findings indicate that the allergen extract used for diagnosis of squid allergy should contain both the 36 kDa and 50 kDa proteins.

Purification and biochemical characterization of a novel allergenic protein from tatary buckwheat seeds

An allergenic protein from tatary buckwheat seeds, designated TBt, was purified by salting out, anion exchange chromatography and size exclusion chromatography (SEC). Analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and SEC showed that the allergenic protein was composed of two subunits linked by disulfide bonds, which we named TBa and TBb. TBa, TBb and TBt have estimated molecular weights of 24, 34 and 56 kDa, and isoelectric points of 6.85, 5.85 and 7.00, respectively. The immunological characteristics of the three proteins as analyzed by enzyme-linked immunosorbent assay revealed that TBa and TBb have comporable IgE binding activity, both higher than that of TBt. Determination of sulfhydryl (-SH) and disulfide (-S-S-) groups in TBt showed that most cysteine residues exist as disulfide linkages rather than free -SH groups. We calculated that TBt has an -S-S- content of 1.978 M/M protein, indicating that TBt contains one disulfide bond and could be the precursor of a 24 kDa allergenic protein from tatary buckwheat seeds.

Immunoprecipitation of spliceosomal RNAs by antisera to galectin-1 and galectin-3

We have shown that galectin-1 and galectin-3 are functionally redundant splicing factors. Now we provide evidence that both galectins are directly associated with spliceosomes by analyzing RNAs and proteins of complexes immunoprecipitated by galectin-specific antisera. Both galectin antisera co-precipitated splicing substrate, splicing intermediates and products in active spliceosomes. Protein factors co-precipitated by the galectin antisera included the Sm core polypeptides of snRNPs, hnRNP C1/C2 and Slu7. Early spliceosomal complexes were also immunoprecipitated by these antisera. When splicing reactions were sequentially immunoprecipitated with galectin antisera, we found that galectin-1 containing spliceosomes did not contain galectin-3 and vice versa, providing an explanation for the functional redundancy of nuclear galectins in splicing. The association of galectins with spliceosomes was (i) not due to a direct interaction of galectins with the splicing substrate and (ii) easily disrupted by ionic conditions that had only a minimal effect on snRNP association. Finally, addition of excess amino terminal domain of galectin-3 inhibited incorporation of galectin-1 into splicing complexes, explaining the dominant-negative effect of the amino domain on splicing activity. We conclude that galectins are directly associated with splicing complexes throughout the splicing pathway in a mutually exclusive manner and they bind a common splicing partner through weak protein–protein interactions.

Differential allergen sensitization patterns in chestnut allergy with or without associated latex-fruit syndrome

BACKGROUND

Chestnut allergy has been almost exclusively considered in the context of the latex-fruit syndrome. Chestnut allergens not linked to latex hypersensitivity have not been studied.

OBJECTIVE

We sought to explore whether differences in sensitization patterns between chestnut allergy with or without associated latex-fruit syndrome can be detected.

METHODS

Twelve patients sensitized to chestnut but not to latex and 3 control patients with latex-chestnut allergy were analyzed. A major chestnut allergen was purified and characterized. IgE immunoblotting, specific IgE determination, and skin prick tests with 5 isolated allergens involved in food allergy or latex-fruit syndrome were also performed.

RESULTS

A major 9-kd allergen was detected in chestnut extract, isolated, and identified as lipid transfer protein (LTP) Cas s 8. Specific IgE to this allergen was found in 91% (by means of IgE immunoblotting) and 58% (by means of ELISA) of sera from patients with chestnut but not latex allergy. Moreover, 66% of these patients had positive skin prick test responses to Cas s 8. Additionally, allergenic LTPs from peach fruit and Artemisia vulgaris pollen were also reactive. In contrast, avocado class I chitinase and latex hevein, allergens associated with the latex-fruit syndrome, showed no reaction. The opposite situation was exhibited by patients with latex-chestnut allergy.

CONCLUSIONS

Patients with chestnut allergy with or without associated latex hypersensitivity present different patterns of major allergens (LTPs and class I chitinases, respectively).

CLINICAL IMPLICATIONS

LTPs and class I chitinases can be used as diagnostic tools in patients with chestnut allergy to predict whether an associated latex sensitization and a risk of potential cross-reactivity with other plant foods and pollens exist.

Mouse monoclonal IgA binds to the galectin-3/Mac-2 lectin from mouse macrophage cell lines

The beta-galactoside-binding S-type lectin galectin-3/Mac-2, expressed among several other cell types on activated macrophages, is known to bind IgE, but not other Ig classes. We report in this paper that the single major constituent in a detergent lysate from the J774 mouse macrophage cell line bound to a mouse monoclonal IgA-affinity column. This fraction has been identified by mass spectrometry analysis as galectin-3. Binding of both mouse IgA and IgE to galectin-3 coated plates was inhibited by lactose and asialofetuin. Furthermore, three different monoclonal IgAs bound also to purified recombinant hamster galectin-3 coated plates in a concentration dependent manner. The potential functional significance of IgA binding to galectin-3 within macrophages and possibly other cell types is discussed.

Further characterization of IgE-binding antigens from guinea pig hair as new members of the lipocalin family

BACKGROUND

Guinea pigs are important sources of inhalant allergens in home and working environments. However, little is known about the molecular characteristics and the relevant epitopes of guinea pig allergens. Recently, several allergens have been identified in hair extract and urine, and the major allergen Cav p 1 (20 kDa) has been characterized.

OBJECTIVE

The aim of the present study was to isolate and to characterize a further major allergen from guinea pig hair with 17 kDa.

METHODS

Guinea pig hair extract was fractionated using anion exchange chromatography and reverse-phase high performance liquid chromatography. Analyses were carried out by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, 2D-PAGE, immunoblotting, immunoblot inhibition, glycoprotein detection, and N-terminal amino acid sequencing.

RESULTS

The nonglycosylated 17 kDa allergen, which was named Cav p 2, was purified to homogeneity. On the basis its 15 N-terminal residues, there was 69% identity with a sequence of Bos d 2, an allergenic protein from cow dander belonging to the lipocalin family. The 2D-immunoblotting analyses of guinea pig hair extract demonstrated that Cav p 2 and Cav p 1, contained several isoforms with pI values ranging from 3.6 to 5.3. The 2D-immunoblot inhibition disclosed cross-reactive IgE epitopes on the allergens Cav p 2 and Cav p 1. Furthermore, Cav p 1 can form both monomers (20 kDa) and dimers (40-42 kDa).

CONCLUSION

These studies provide important information on the isoallergen character of two relevant guinea pig allergens Cav p 1 and Cav p 2 as well as on their cross-reactive properties.

Galectins and other endogenous carbohydrate-binding proteins of animal bladder

Defects in the glycocalyx of the bladder epithelium may be related to the development of bladder diseases including interstitial cystitis which is a chronic bladder disease of unknown etiology. Indirect evidence has implicated alterations in the bladder epithelial glycoconjugates in interstitial cystitis and vesicaler instillation of glycosaminoglycans is promoted as treatments. However, information on the nature of the glycoconjugates of the bladder epithelium and lectins that may interact with the exogenous instilled glycoconjugates is very limited. We have examined the endogenous lectin associated with bladder epithelium by immunohistochemistry using biotinylated neoglycoconjugates. The strong calcium-independent binding of beta-D-galactose probe suggested the presence of galectins in rabbit and human bladder. Extracts of rabbit bladder organ cultures metabolically labeled with [14C]-amino acids were subjected to affinity chromatography on immobilized lactose and the specifically bound material eluted with 0.2 M lactose. SDS-PAGE of the recovered proteins revealed a major band of approximately 30 kDa and a minor band of 21 kDa. Polymerase chain reaction and northern blot analysis showed that both galectin-3 and galectin-4 are expressed in rabbit bladder. Since galectin-3 from rabbit had been previously cloned, we cloned and sequenced galectin-4 from rabbit bladder. The deduced full length sequence of 328 amino acids revealed four distinct regions: a N-terminal peptide of 19 residues, two carbohydrate recognition domains of 130 residues each, and a linker region of 49 residues. Comparison of the rabbit galectin-4 sequence with those of human, pig, rat, and mouse revealed two invariant peptide motifs that are proposed as signature sequences for identifying related galectins.