The extent and the specificity of the initial cell attachment induced by various proteins coated on plastic surfaces have been studied with the following results: (a) Cell adhesion on the surfaces coated with sialidase and ,6-galactosidase was as strong as on concanavalin A and Limulus lectin-coated surfaces and the reactions were strongly inhibited by glycosidase inhibitors or by competitive substrates . The adhesion on sialidase was inhibited by 2-deoxy-2,3-dehydro-N-acetylneuram in ic acid and by polysialoganglioside (GT1b) at low concentration (0 .05-0.1 mM) . The cell adhesion on a-gal actosidase coat was inhibited by 1,4-D-galactonolactone and a-methylgalactoside but not by a-methylgalactoside . Thus, the initiation of cell adhesion on glycosidase surfaces could be mediated through the interactions of the specific binding sites of the enzyme surface with the cell surface substrates under physiological conditions . (b) Cell adhesion on various lectins could be blocked by various competing monosaccharides at the concentrations similar to the inhibitory concentrations for binding of lectins from solution to the cells. (c) Cell adhesion on fibronectin surfaces as well as on gelatincoated surfaces was equally inhibited by GT 1b at relatively high concentrations (0 .25-0.5 mM) . Lower concentrations of GT 1b (0 .05-0.1 mM) inhibited the cell adhesion on surfaces of Limulus lectin and sialidase . It is suggested that the cell adhesion mediated by fibronectin is based on yet unknown interactions in contrast to a specific cell adhesion through glycosidases and lectins.The complex carbohydrates at the cell surface have been implicated to play an essential role in determining the specificity and the reactivity of cell to cell or cell to substratum (e .g., basement membrane) interaction in multicellular system and in tissue . A remarkable change of the carbohydrate structure at the cell surface, associated with oncogenic transformation (24, 65) and differentiation (16,25,47), and the presence of lectins at the animal cell membranes (reviewed in references 1 and 59) have supported this concept. However, the biochemical mechanism of cell-cell interaction and adhesion is far from being clear, and the topic has received much discussion in current studies, particularly in relation to the function of fibronectin, which promotes cell adhesion and spreading (23, 27, 68; reviewed in references 11, 22, and 67 Cell adhesion has been studied on lectins coated on nylon and plastic surfaces (22,29,56), on fibronectin and gelatin coated on plastic plates (11,13,22,23,27,67,68), and on galactose-gel particles (66). These assay systems are sensitive and can be used as a good model to study the mechanism of cell-to-cell or cell-to-substratum adhesion . This paper describes the intensity and the specificity of cell adhesion on two classes of carbohydrate-binding proteins (lectins and glycosidases) as compared with the adhesion on fibronectin-coated surfaces .
The kinetics of cell attachment and cell spreading on the coated surfaces of two classes of carbohydrate-reactive proteins, enzymes and lectins, have been compared with those on fibronectin-coated surfaces with the following results: (a) A remarkable similarity between the kinetics of cell attachment to fibronectin-coated and glycosidase-coated surfaces was found . In contrast, cell attachment kinetics induced by lectin-and galactose oxidase-coated surfaces, in general, were strikingly different from those on fibronectin and glycosidase surfaces . The distinction between fibronectin-or glycosidase-and lectin-or galactose oxidase (an enzyme with lectin-type characteristics) -coated surfaces was further supported by the finding that cytochalasin B and EDTA inhibited cell attachment to fibronectin-and glycosidase-coated surfaces but not lectin-coated surfaces . (b) Fibronectin, if labeled and added to a cell suspension, showed only low or negligible interaction with the cell surface. However, fibronectin absorbed on plastic surfaces showed a high cell-attaching activity . It is assumed that fibronectin coated on plastic surfaces may form polyvalent attachment sites in contrast to its lower valency in aqueous solution . (c) Various inhibitors of cell attachment to both fibronection-, galactose oxidase-, and lectin-coated surfaces were effective only during the first few minutes of the adhesion assay, after which time the attached cells became insensitive to the inhibitors . It is suggested that the initial specific recognition on either lectin-type or fibronectintype surfaces is followed by an active cell-dependent attachment process. The primary role of the adhesion surface is to stimulate the cell-dependent attachment response . (d) Cells attached on tetravalent concanavalin A (Con A) spread very rapidly and quantitatively, whereas divalent succinyl Con A and monovalent Con A were effective stimulators of cell attachment but not cell spreading. Cross-linking of succinyl Con A restored the cell spreading activity . Tetravalent Con A surfaces specifically bind soluble glycoproteins, whereas succinyl Con A has a greatly reduced ability to bind the same glycoproteins . These results suggest that cross-linking of cell surface glycoproteins by the multivalent adhesive surface may trigger the cellular reaction leading to cell spreading.The components and mechanisms involved in cell attachment on various adhesive surfaces have been studied extensively as a model of cell-cell and cell-substratum interactions in multicellular systems (see, for reviews, references 8, 9, 12, 14, 30, 34, and 46) . In the preceding paper (40), two classes of carbohy-138 drate-binding proteins, lectins and glycosidases, have been found to be active promoters for cell adhesion and spreading. Of various components at the cell surface that could promote cell attachment and spreading, fibronectin is the best characterized (21,45,46). This paper provides further information on
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