Concanavalin A binding glycoprotein in human stratum corneum

Qualitative and quantitative alterations of cell surface carbohydrate residues during epidermal morphogenesis

The purpose of this study was to investigate the carbohydrate residue composition of cell surface in the developing epidermis and to define the chronological sequence of its alterations in human fetuses from the 10th to the 20th weeks of gestation and at the 23rd week of gestation, using a panel of six biotinylated lectins: Concanavalin A, Ulex europaeus agglutinin-I, Ricinus communis agglutinin-I, Peanut agglutinin, Wheat germ agglutinin, and Dolichos biflorus agglutinin. Distinct qualitative and quantitative alterations in the expression of cell surface carbohydrate residues were found during epidermal morphogenesis prior to keratinization (10th to 20th weeks). At the 23rd week of gestation, the already keratinized fetal human epidermis revealed a pattern of cell surface glycosylation very similar to that of the adult human epidermis. Further studies are now warranted to answer the question regarding whether the glycosylation pattern in the developing human epidermis is disturbed in fetuses with genodermatoses and whether these disturbances might be important for prenatally diagnosing the latter.

Carbohydrate expression and modification during keratinocyte differentiation in normal human and reconstructed epidermis

Using fluorescein isothiocyanate (FITC)-labeled lectins we were able to demonstrate the presence of specific carbohydrate moieties in normal human and reconstructed epidermis. Evidence is provided that in both cases the strongly reduced lectin staining at the level of the stratum corneum is the result of a hindered accessibility of the lectins in this lipid-rich hydrophobic environment. Isolated corneocytes and purified cornified envelopes (CEs) exhibited clearly glycosylated structures reacting with distinct lectins. The presence of glycosidase activity, particularly in the upper layers of the epidermis characterized by an acidic environment (pH 5.5), indicates that modifications of the sugar residues might be important in epidermal homeostasis, barrier behavior and desquamation. Absent or strongly reduced glycosidase activity in the stratum corneum of reconstructed epidermis with an impaired pH gradient could be in part responsible for the reduced barrier function and the lack of desquamation in this model.

Lectin binding patterns in amphibian skin epithelium

Seven lectins (PNA, DBA, WGA, UEA-I, RCA, SBA, Con A) were used to localize glycoconjugates in the skin of 10 species of Amphibia, 7 anurans (Bufo marinus, Bufo bufo, Rana ridibunda, Rana pipiens, Hyla arborea, Pelobates syriacus and Xenopus laevis) and 3 urodeles (Salamandra salamandra, Triturus vulgaris and Ambystoma mexicanum). It was found that every lectin has a specific binding pattern in the skin of each species. No common pattern could be established, either among frogs or toads, nor for a particular lectin. Each lectin bound specifically and selectively to a particular epithelial component, which differed from one species to the other. A number of lectins showed selective binding to mitochondria-rich cells, but, again, a pattern in positivity could not be found. It is concluded that lectin histochemistry does correlate with cellular function. Our data can be applied in studies of epithelium and skin development, and of changes that occur during adaptation to the environment by amphibian species.

30-kDa trypsin-like proteases in the plantar stratum corneum

The casein digestible proteases in human plantar stratum corneum were determined to be about 75-kDa, 30-kDa and 25-kDa in molecular weight by zymography. The enzymatic activity of the 75-kDa and 25-kDa proteases was specifically inhibited by chymostatin, which is an inhibitor of chymotrypsin-like serine proteases, and the proteases around 30-kDa were inhibited by leupeptin, a trypsin-like serine protease inhibitor. The enzymatic activity of all these proteases was inhibited by aprotinin. The 30-kDa trypsin-like proteases were heat-stable; their enzymatic activity still remained even after heating at 100 degrees C for 60 minutes. Their optimal pH was around 9, and the activity was higher in the outer part of the stratum corneum than in the inner part.

Cohesion and desquamation of epidermal stratum corneum

This article attempts to provide a comprehensive review on the roles of various classes of molecules in the cohesion and desquamation of the stratum corneum. In the first part of this monograph we review the field of epidermal differentiation in vivo and vitro, describing the expression and functions of a number of key structural molecules that characterize the process. In the second part we emphasize terminal differentiation and the biogenesis of the stratum corneum. The stratum corneum is a cell layer unique to fully differentiated squamous epithelia such as skin. While it is a dead stratum, it nevertheless is in a homeostatic process of continual shedding and renewal in synchrony with basal cell replication. It is also a degradative layer containing many proteinases and glycosidases in which a variety of intracellular and intercellular macromolecules are degraded. We highlight the molecules localized within the intercorneal matrix that are most likely to play a role in cohesion and desquamation, including: glycoproteins, lipids and enzymes. Because it is difficult to study the stratum corneum and desquamation in the native tissue, we discuss a number of model systems that have been used. The stratum corneum can be dispersed into single squames in different ways; these include mechanical dispersion as well as agents such as detergents and enzymes. The solubilized molecules and the structures remaining can then be studied as to their specific roles in desquamation. Using this approach it is possible to reconstitute multilayered structures that resemble a real stratum corneum. We have shown that glycoproteins play a key role in squame reaggregation and that this process can be modulated with amino sugars in a lectin-like fashion. Cohesion and desquamation can also be studied in tissue culture. Depending on the culture system, the extent of terminal differentiation and squame accumulation varies. Yet desquamation does not normally occur. It can be induced however by the inclusion of exogenous agents such as IFN-gamma which are found in the native epidermis but are absent in vitro. Modulation of desquamation by other exogenous agents is likely to yield further knowledge of how shedding occurs in vivo. Insight has also come from studies of scaling skin disorders. The glycoprotein and lipid profiles are altered in the stratum corneum in many diseases of aberrant terminal differentiation. A number of abnormalities in the levels of cytokines and growth factors have also been reported in the lesional tissue of such diseases.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of gamma-interferon on lectin-binding glycoproteins in cultured human keratinocytes

We report the effect of exposure of human keratinocyte cultures to human recombinant gamma-interferon (g-IFN) on the expression of glycoproteins. Concanavalia ensiformis agglutinin (Con-A), and Arachis hypogaea agglutinin (PNA) were used to investigate expression of glycoproteins. NP-40 extracts from cultures grown with or without 100 U/ml g-IFN were analyzed by incubation of SDS-polyacrylamide gels with 125I-labeled lectins. Comparison of Con-A binding glycoprotein profiles showed both qualitative and quantitative changes related to the effect of g-IFN. Differences were also apparent after labeling of the gels with PNA. A limited number of components were labeled, with most of the reactivity falling within a couple of diffuse bands with high molecular weight (300 to 360 kDa). These components were strongly labeled in extracts from cells grown in the presence of g-IFN, but weakly reactive in control cultures. Neuraminidase treatment unmasked a 205 kDa PNA binding molecule only when cells were cultured in the absence of g-IFN. These changes are interpreted in terms of increased keratinocyte differentiation induced by g-IFN and demonstrate that glycoproteins bearing carbohydrate residues available to lectins Con-A and PNA have to be taken into account to better understand the complex action of this lymphokine. In inflammatory lesions, such changes in the glycoproteins of keratinocytes expressing HLA-DR antigens remain to be explored.

Evidence that major 78-44-kD concanavalin A-binding glycopolypeptides in pig epidermis arise from the degradation of desmosomal glycoproteins during terminal differentiation

The major concanavalin A (Con A)-binding component in urea/deoxycholate/mercaptoethanol extracts from pig ear epidermis had an apparent Mr of 78 kD. In indirect immunofluorescence affinity-purified polyclonal antibodies against this glycopolypeptide strongly stained the surface of suprabasal cells in the epidermis of pig and human skin. Immunocytochemical labeling with gold-labeled second antibody localized this staining to externally disposed, trypsin-sensitive components of desmosomes. Western blotting showed that the 78-kD glycopolypeptide was immunologically related to several other Con A-binding components in pig epidermis. Immunoreactive components with Mr of 115 and 100 kD were membrane-bound, appeared to be susceptible to trypsin in intact epidermis, and were absent from the stratum corneum. Immunoreactive components of lower Mr (78-44 kD) were not membrane-bound, were resistant to trypsin in intact tissue, and were present predominantly in the keratinized layers of pig epidermis. The 115-44-kD glycopolypeptides were also recognized by antisera raised against desmoglein II/desmocollin glycoproteins isolated from bovine spinous layer desmosomes. In addition, these antisera reacted with 120- and 105-kD bands that were apparently not recognized by the anti-78-kD glycopolypeptide antiserum in immunoblotting. In immune precipitation the anti-78-kD glycopolypeptide and antidesmoglein II/desmocollin antisera precipitated comparable amounts of the radioiodinated 78-44-kD components. Both antisera also precipitated the 120- and 105-kD components although the anti-78-kD glycopolypeptide serum was less effective. Little reaction with the 115- and 105-kD components was observed in immune precipitation with either serum. Proteolytic peptide mapping confirmed that the various immunoreactive glycopolypeptides were biochemically as well as immunologically related. The results suggest that terminal differentiation in pig epidermis is accompanied by the orderly degradation of desmoglein II/desmocollin glycoproteins resulting in the accumulation of 78-44-kD glycopolypeptides in the stratum corneum. These glycopolypeptides may represent functionally important nonmembranous domains of cell-adhesion molecules in desmosomes.

Lectin binding patterns in amphibian epidermis

A battery of 6 different horseradish peroxidase conjugated lectins has been employed for structural localization of glycoconjugates in amphibian epidermis. Lens culinaris (LCA) lectin stained the basal membrane and gave no significant reaction on the epidermal layers. Canavlia ensiformis (Con A) and Griffonia simplicifolia II (GS II) lectins bound the keratinocyte cytoplasm and the basal membrane as well. Ulex europaeus I (UEA I) lectin had only reactivity with flask cells. Griffonia simplifolia I (GS I) and Glycine max (SBA) lectins preferentially bound the cell membranes of keratinocytes, being the intensity of the staining gradually increasing from the stratum spinosum to the stratum granulosum. These results show that UEA I, GS I, and SBA are good markers to distinguish different cell types and the degree of keratinocytes differentiation.

Endogenous lectin from terminally differentiated epidermal cells

We isolated a concanavalin A (Con-A)-binding glycoprotein from human stratum corneum by nonionic detergent extraction, lectin affinity chromatography, and preparative gel electrophoresis. This glycoprotein migrates as a single band at 40 kilodaltons at sodium-dodecyl-sulfate gel electrophoresis with or without the presence of 2-mercaptoethanol. It was shown to have a heterogeneous distribution between pH 5.6 and 7.6 by isoelectric focusing. The glycoprotein is histidine rich (10.4%) but is distinct from other histidine-rich proteins (epidermal filaggrin and the histidine-rich glycoprotein from serum). It does not bind to lectins specific for L-fucose or alpha-D-galactose. We prepared a monospecific polyclonal antibody to the 40-kilodalton glycoprotein; at the ultrastructural level, it cytoimmunolocalizes exclusively to the membranes of the stratum corneum. A unique feature of the glycoprotein is that it is an endogenous lectin: it hemagglutinates trypsinized and gluteraldehyde-fixed rabbit erythrocytes. The inhibition of its hemagglutination was found to be greatest with amino sugars, down to a saccharide concentration of 10(-5) mM. Such a high affinity of binding at the cell surface suggests that this glycoprotein is a major carbohydrate-binding, cross-linking molecule that holds adjacent corneocytes together in the stratum corneum. We hypothesize that this lectin plays a role in the adhesion and desquamation of the stratum corneum.

Isolation and characterization of a 30 kDa membrane glycoprotein from human stratum corneum

Using iodinated concanavalin A in conjunction with gel electrophoresis, we have identified a 30 kDa glycoprotein in the stratum corneum of human skin. We isolated this glycoprotein by extraction in nonionic detergent, affinity chromatography and preparative gel electrophoresis. It binds to concanavalin A but not to three other lectins. The purified glycoprotein migrates at 30 kDa whether or not reducing agents are present. It is rich in histidine and lysine, but lacks arginine, proline, tyrosine and methionine. It is clearly distinct from filaggrin. We prepared a monospecific polyclonal antibody to this glycoprotein and localized it by immunohistochemistry exclusively to the cell membrane of corneocytes. We postulate that the glycoprotein may play a role in the cohesion and desquamation of corneocytes.