Qualitative and quantitative aspects of lectin-induced vacuole formation in mouse peritoneal macrophages

The binding, internalization, and vacuologenic activity of several native and chemically modified lectins was investigated on untreated and neuraminidase-treated mouse peritoneal macrophages. The distribution of lectin receptors on the cell surface and their internalization was assessed by employing both radioactive and fluorescent lectin derivatives. On the basis of their effect on the macrophages, the lectins tested can be divided into 2 categories: lectins that induce vacuole formation (concanavalin A, wax bean agglutinin, and wheat germ agglutinin), and lectins that do not induce vocuolation (soybean agglutinin, peanut agglutinin, and Lotus tetragonolbus agglutinin). Soybean and peanut agglutinins bound to macrophages only after neuraminidase treatment, but the latter treatment did not change the effect of other lectins on the cells. Glutaraldehyde-cross-linked polymers of soybean or peanut agglutinins, which are multivalent with respect to the number of sugar binding sites, induced vacuolation in neuraminidase-treated cells. On the other hand, succinylation of concanavalin A, which reduces the lectin's valence from 4 to 2 abolished its vacuologenic activity. While the data do not indicate direct correlation between vacuole induction and the number of lectin receptors or the extent of their internalization, they do suggest that multivalency of lectins is an important factor in vacuole formation. Multivalency of a lectin enables extensive cross-linkage of membrane receptors which may be a prerequisite for triggering vacuolation.