Physical and chemical characterization of the major lactose-blockable lectin activity from fetal calf skeletal muscle

Expression of the endogenous 14-kDa beta-galactoside-binding lectin galectin in normal human skin

The localization of an endogenous 14-kDa beta-galactoside-binding lectin (galectin) and its pattern of gene expression were examined in normal human skin by light- and electron microscopy. Under the light microscope, immunostaining of 14-kDa galectin was observed in the cell membrane of cells in the basal and spinous layers of the epidermis. Galectin was also found in the Langerhans cells, as shown by double labeling using anti-14-kDa galectin and anti-CD1a antibodies. In the dermis, immunostaining for the 14-kDa galectin was positive in the extracellular matrix and fibroblasts. At the electron-microscopic level of resolution, galectin was located primarily along the plasma membrane of keratinocytes, and in both the cytoplasm and nucleus of Langerhans cells in the epidermis, whereas in the dermis it was detected in the extracellular matrix and in both the nucleus and cytoplasm of fibroblasts. The gene expression of 14-kDa galectin was visualized by the HRP-staining method following in situ hybridization techniques. The expression was detected in the cytoplasm of cells in the basal and spinous layers of the epidermis; whereas, in the dermis, it was detected in the cytoplasm of fibroblasts. Moreover, SDS-polyacrylamide gel electrophoresis and lectin-blot analysis revealed that this galectin bound to glycoproteins of approximately 17, 62, and 72 kDa in the epidermis and to those of 29, 54, and 220 kDa in the dermis. The present study indicates that 1) normal human skin produces the beta-galactoside-binding 14-kDa galectin, and 2) this galectin is located in both the epidermis, particularly in the keratinocytes and Langerhans cells, and in the dermis. These results suggest that galectin is important for cell-cell contact and/or adhesion in the epidermis and for cell-extracellular matrix interaction in the dermis.

Changes in expression of the endogenous beta-galactoside-binding 14-kDa lectin of chick embryonic skin during epidermal differentiation

Changes in the expression pattern of the gene for the endogenous beta-galactoside-binding 14-kDa lectin of chick embryo were examined immunohistochemically during epidermal differentiation in vivo and in vitro with special reference to detailed localization of the 14-kDa lectin. The gene expression was visualized by the HRP-staining method following in situ hybridization, in which sulfonated cDNA was employed as a probe. The 14-kDa lectin gene expression (mRNA) was detected mainly in the intermediate layer of the epidermis: it was faint in 13-day-old embryos, gradually increased in intensity during epidermal differentiation, and became intensely positive in 17-day-old embryo. The expression of the gene in skin explants was suppressed by vitamin A, which induces mucous metaplasia of the epidermis in vitro. The anti-14-kDa lectin reaction was positive mainly in the intermediate layer of the differentiating epidermis, coinciding chronologically with expression of the gene at the light microscopic level. Immunoelectron microscopy revealed that the positive reaction was primarily localized in desmosomes, in tonofilament bundles anchored to the desmosomes, along the outer surface of the plasma membrane, and in the intercellular space. Essentially the same staining pattern was observed in differentiating epidermis in vitro. The positive reaction was markedly reduced in the epidermis in which differentiation had been suppressed in vitro by the addition of vitamin A.

Immunohistochemical localization of 14 kDa beta-galactoside-binding lectin in various organs of rat

Immunohistochemical localization of 14 kDa beta-galactoside-binding lectin in various organs of adult rat was achieved using a monospecific antibody raised against lectin purified from rat lung. The antibody-stained cells were formed into small aggregates, thin fascicles, or thick bundles in the walls of blood vessels, gastrointestinal tracts and urogenital organs. From the patterns of distribution, as well as their organization, these immunoreactive cells were regarded as smooth muscle cells. This was confirmed by a double immunofluorescence study using a mixture of anti 14 kDa lectin and anti alpha-smooth muscle-specific actin antibodies. Strong 14 kDa lectin immunoreactivity was seen in the pericellular matrix of smooth muscle cells in intact organs as well as in detergent-treated organs from which all cellular components were extracted. From these findings, it is suggested that the 14 kDa lectin may be externalized by smooth muscle cells into their pericellular matrix and participate in the crosslinking of the complementary glycoconjugate(s) localized at that site. The macromolecular xomplex of glycoconjugates thus formed around smooth muscle cells may play a role in anchoring smooth muscle cells to the pericellular connective tissue thereby permitting the force of muscle contraction to be efficiently transmitted to the surrounding connective tissue proper.

Characterization of an S-type lectin purified from porcine heart

We have purified a carbohydrate-binding protein from porcine heart by affinity chromatography on asialofetuin-Sepharose and have characterized this protein with respect to its size, amino acid composition, partial amino acid sequence, and carbohydrate-binding specificity. Porcine heart lectin (PHL) has a subunit molecular mass of 14,700 and is immunologically cross-reactive with a polyclonal antibody raised against a lectin isolated from calf heart. The amino acid composition of PHL is similar to that of lectins that have been isolated from calf heart, bovine brain, and rat lung. Moreover, the primary sequences of four tryptic fragments (52 amino acids total) derived from PHL are closely related to sequences previously determined for 10 other vertebrate-derived lectins. The ability of PHL to agglutinate rabbit erythrocytes was inhibited only by oligosaccharides containing terminal beta-galactosyl residues. These data indicate that PHL is a vertebrate "S-type" lectin and provide further evidence that the structures and carbohydrate-binding specificities of these lectins are highly conserved across diverse vertebrate genera.

Rat lung 29 kD beta-galactoside-binding lectin is secreted by bronchiolar Clara cells into airways

We isolated a mixture of beta-galactoside-binding lectins from rat lung and raised polyclonal antibody against 14 kD lectin purified from the mixture of lectins. Immunoblotting of the mixture of lectins, which was separated with SDS-PAGE under reducing condition and transferred onto a NC paper, showed that the antibody reacted with two bands at 14 and 29 kD, indicating that these two lectins have common antigenic determinants(s). Immunohistochemically, the antibody recognized only bronchiolar Clara cells with intense immunofluorescence in their apical cytoplasmic protrusions where the secretory granules of the cells are known to be stored. Thus, to determine if the lectin(s) might be secreted into airways, we next raised antibody against airway secretions free from serum as well as surfactant proteins. By immunoblot analysis, the resulting antibody stained 29,45 and 55 kD bands, but not 14 kD band, on a NC paper transferred with the mixture of lectins. These findings suggest that at least 29 kD lung lectin is located in bronchiolar Clara cells and secreted by these cells into airways.

Investigation on the occurrence of soluble lectins in mammalian nervous tissue extracts

Five brain or retina crude extracts obtained from adult mammalians and nine fractions of brain extracts prepared by chromatography were screened for their lectin activities. All crude extracts and several fractions contained agglutinins reacting with neuraminidase-treated rabbit red blood cells. Hemagglutination activity varied widely with the method of preparation of the extracts. Hemagglutination inhibition tests were carried out to look for possible differences in the specificities of the agglutinins. All were found to be D-galactosyl specific. Each crude extract was found to contain a second lectin activity, which was detected using ethanol-treated rabbit erythrocytes known to react with heparin-binding lectins. Hemagglutination and inhibition studies showed that they completely differ from the galactoside-binding lectins detected previously. The possible functions of these lectins are discussed.

Isolation and characterization of chicken thymic electrolectin

We have detected the presence of a beta-D-galactoside-binding lectin (electrolectin) in extracts of the thymus of adult chickens. This lectin was purified by affinity chromatography on a lactosyl-Sepharose column to yield 1.4 mg of pure protein from 230 g of thymus. The chicken thymic electrolectin (CTE) has an Mr of 15 300 when analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and of 30 000 when analysed by gel filtration. The amino acid composition of CTE is similar to that of other electrolectins purified from human and rat lung. CTE cross-reacts immunologically, but is not identical, with electrolectins from electric-eel electric organ and from chick-embryo pectoral muscle. CTE agglutinates chicken thymocytes but does not appear to promote their mitosis.

Soluble lectins: a new class of extracellular proteins

Soluble lectins of cellular slime molds and vertebrates are present at extracellular sites in the developing or adult tissues that make them. Some lectins are concentrated around cell groups, as in extracellular matrix or elastic fibers. Others are at the interface between cells and the external environment, as in mucin or slime. Specific glycoproteins, proteoglycans, or polysaccharides that bind these endogenous lectins may also be present at these sites. Interactions between the lectins and glycoconjugates appear to play a role in shaping extracellular environments.

Purification and characterization of beta-galactoside-binding lectin from chick embryonic skin

Lectin activity was found in tarsometatarsal skin of chick embryo. It was specific for beta-linked galactosyl residues and required a thiol-reducing agent for hemagglutination activity. The lectin was extracted from dermis and epidermis (skin) with lactose and purified to apparent homogeneity by affinity chromatography on asialofetuin-Sepharose. Examination of their biochemical properties showed that although dermis and epidermis develop from different origins, they contain the same lectin. The apparent subunit Mr of lectin was 14000 and its isoelectric point was 7.0. Under non-dissociating conditions, the lectin exists mainly as a dimer. Radioimmunoassay showed that this skin-type lectin is present in many tissues including skin, muscle, bone, eye, heart, liver and brain at various developmental stages. A wide distribution and a marked change in its content during development strongly suggest that the lectin might have a fundamental role in cellular function, embryonic development and tissue differentiation.