Lectin binding by microvillous membranes and coated-pit regions of human syncytial trophoblast

Abstract

The distribution of saccharides on the microvillous membrane of the human syncytial trophoblast was investigated using ferritin conjugates of four lectins: concanavalin A (specific for alpha-D-manno- and alpha-D-glucopyranosyl residues), wheatgerm agglutinin (specific for N-acetylglucosamine), Limulus polyphemus lectin (specific for N-acetylneuraminic acid), and Lotus tetragonolobus lectin (specific for alpha-L-fucose). Concanavalin A and wheatgerm agglutinin (WGA) reacted strongly with the surface membrane and ferritin deposits were also observed in coated pit regions of the membrane. Lectins from L. polyphemus and L. tetragonolobus, however, reacted only weakly with the microvillous border and neither reacted with coated pits. Enhanced agglutinability of trophoblast cells in comparison with other foetal cells from the same conceptus was seen with WGA. This agglutination was inhibited by addition of acetylglucosamine or by a solubilized membrane fraction which was bound by a column of WGA-Sepharose. The membrane fraction which did not bind to the column did not inhibit agglutination. Electrophoresis of the WGA-bound membrane proteins revealed six subunits, the major band having an apparent mol. wt. of 55 000. A protein of this mol. wt was also seen in coated vesicles isolated from equivalent human placentae.

Characterization of the sugar chain expression of normal term human placental villi using lectin histochemistry combined with immunohistochemistry

“…It has been pointed out that the brush border of the syncytiotrophoblast is heavily glycosylated as the primary site for feto-maternal interactions (Whyte 1980;Sgambati et al, 2002). In this study, we demonstrated that the brush border of the syncytiotrophoblast layer strongly expressed GlcNAc, and weakly expressed sialic acid.…”

“…For example, the transferrin receptor and alkaline phosphatase in the brush border are known to be associated with N-linked oligosaccharides and 2,3-linked sialic acid (Fukushima et al, 2003). Alkaline phosphatase is also reported to bind to Con A, and clathrin-coated pits were implied to react with WGA (Whyte, 1980). Although the glycosylation of most of these molecules in the brush border has yet to be fully elucidated, our finding that the trophoblastic brush border mainly expressed GlcNAc accords with previous reports (Reitsma et al, 2007).…”

“…It has been strongly speculated that many kinds of the sugar code system are involved in various placental functions (Gude et al, 2004). Indeed, there have been several studies on the distribution of oligosaccharides of glycoconjugates in normal term human placental tissues (Johnson and Faulk, 1976;Whyte, 1980;Lee and Damjanov, 1984;Konska et al, 2003) and pathological placental tissues (Thrower et al, 1991;Sgambati et al, 2002;Sgambati et al, 2007). These, however, employed various approaches and methods, resulting in discrepant conclusions, resulting in that no consistent and reliable information is available concerning the sugar chain expression of the human placenta.…”

Lectin histochemistry of human placenta

“…Lectins labeled with fluorescein isothiocyanate (FITC) or horseradish peroxidase have been extensively used as histochemical reagents in the study of both normal [3,9,10,12,14,15,18,191 and pathologically altered [l, 2, 4, 5, 13, 161 human and animal tissues. Labeled lectins have been used to characterize human placental tissue, but the data are fragmentary [6,7,11,20,211 and often inconsistent or contradictory, so that a complete histochemical map of lectin-binding carbohydrate sites is still lacking. These discrepancies are due, in part, to the different protocols used in different studies [17] and, in part, to the lack, until recently, of commercially available purified-lectin preparations.…”

Differential Lectin Binding to the Fibrinoid of Human Full-Term Placenta: Correlation with a Fibrin Antibody and the PAF-Halmi Method

“…Furthermore, because of the presence of proteoglycans in placental fibrinoid [Kisalus and Herr, 1988], the reaction of three lectins within placental fibri noid was investigated: Ulex europaeus (UEA-I), which is known to stain placental endothelium and circulating blood cells [Lang et al, 1993], Bandeiraea simplicifolia lectin (BS-I), which labels cell types with a predominantly secre tory activity [Murakami et al, 1992]. Lycopersicon escttiention (LEA) binds to the N-acetyl-D-glucosamine [Nachbar et al, 1980] associated with the syncytiotrophoblast [Whyte. 1980],…”