Interactions between chondroitin sulfate and concanavalin A

Proteoglycans and the modulation of cell adhesion by steric exclusion

The hypothesis that cell aggregation may be driven by linear polymers in the matrix, particularly glycosaminoglycans, is revisited in light of more recent evidence. A model is proposed that extends the concept of steric exclusion to include a role in determining the directionality of cell migration and neurite extension. Recent literature is reviewed to support the conclusion that in living tissues the theoretical conditions for driving aggregation and migration by steric exclusion are met. The ability of a linear polymer to exclude cells is a function of its viscosity, which is optimum with glycosaminoglycans similar to chondroitin sulfate. It is ineffective with low viscosity glycosaminoglycans such as most heparin or heparan sulfate. Hyaluronic acid, a massive polymer, excludes cells poorly when present as an open matrix gel but forms an effective exclusion barrier when attached to the cell surface. According to a model for steric exclusion in organogenesis, when cells have a glycocalyx of linear polymer, they should disperse and migrate down a viscosity gradient of excluding matrix polymer; when they shed or internalize their surface coat in the continued presence of matrix, they should be excluded into a smaller volume and thus stimulated to aggregate.

Quantitative determination of individual glycosaminoglycans in plasma by concanavalin A rocket electrophoresis

A new one-dimensional agarose gel electrophoresis method for the quantitation of glycosaminoglycans in biological samples has been described. In this procedure, concanavalin A, suspended in agarose gel, interacts with glycosaminoglycans such that rocket-like precipitin lines are formed. The area of the rocket is directly proportional to the glycosaminoglycan content of the sample. This procedure permits measurement of glycosaminoglycans in amounts as low as 0.5 nmol uronic acid equivalents with a coefficient of variation of only 8%. The described method has been applied to the determination of free heparan sulfate in plasma. This method can also be used to measure all high-charge glycosaminoglycans of biological interest.

Cell surface proteoglycans as a negative modulator in concanavalin A-mediated agglutination of hepatoma cells

Proteoglycan (heparan sulfate-protein conjugate) was solubilized with 8 M urea from rat liver plasma membranes after enzymic (RNAase, neuraminidase) treatments and extensively purified by chromatography and gel filtration. The final products gave an average ratio of hexuronate to protein (weight) of approx. 1.5, contained hexosamine equimolar to hexuronate and were sensitive to beta-elimination (the molecular weight being reduced from 20 . 10(4) to 3 . 10(4) (gel filtration)). The proteoglycan fraction, when added to trypsinized and untrypsinized ascites hepatoma (AH-130F(N)) cells, inhibited the concanavalin A-mediated agglutination of the cells. However, the alkali-treated proteoglycan (beta-elimination) or acid mucopolysaccharide fraction prepared from liver plasma membranes by papain digestion were less effective, and a reference preparation of heparan sulfate was almost ineffective. It was confirmed that significant amounts of proteoglycan labelled with 35SO4(2-) were firmly bound to or taken up by the trypsinized ascites hepatoma cells. These results together with the sensitization of lectin-mediated agglutination by mild protease treatment of cells suggest that cell surface proteoglycans may act as a negative modulator in the lectin-mediated agglutination of cells.

Glycosaminoglycans: structure and interaction

In the last few years, there has been considerable progress in the studies on glycosaminoglycans, a group of acidic polysaccharides present in the intercellular matrix of connective tissue. X-ray diffraction studies have indicated that these polymers can exist in the condensed phase in some helical form. Chiroptical and hydrodynamic measurements have provided significant information regarding the molecular conformation in solution and other physicochemical properties of the polymers. Studies related to the interaction properties of glycosaminoglycans with polypeptides, metal ions, and other molecules are numerous. This review covers mainly the results and their interpretations of both published and as yet unpublished material of the 1970s, but certain previous data are also included. A present-day concept regarding the structure and interaction properties of these molecules on the basis of various physicochemical measurements is presented. The biosynthesis and metabolism of glycosaminoglycans, and the structure of proteoglycans and glycoproteins, are not discussed.