Valence-Dependent Internalization of Lectins into Balb/c 3T3 Cells

Abstract

Requirements for the cross-linking of lectin receptors in the internalization of lectins into Balb/c 3T3 cells were investigated with lectins of various valences. 125I-labeled tetravalent concanavalin A (Con A) was inter-nalized rapidly within 60 min, whereas divalent Con A was internalized only slightly after 60 min, and no monovalent Con A was, even after 120 min. How-ever, additional treatment of the cells which bound either monovalent or divalent Con A with anti-Con A antibody resulted in the rapid internalization of lectin. Internalization of other 125I-labeled lectins (wheat germ agglutinin, Lens culinaris agglutinin and Pisum sativum agglutinin) also appeared to be dependent on their valences. These results suggest that the cross-linking of lectin receptors is required for lectin take up in Balb/c 3T3 cells. When these cells were treated with dansyl cadaverine (500μM) and monoethylamine (90 mM), both potent inhibitors of transglutaminase, the take up of [125I]Con A was inhibited by 80% and 50%, respectively. By contrast, cytochalasin B and colchicine, inhibitors of cytoplasmic structures, inhibited [125I]Con A internalization by 47% and 25%, at the highest concentrations which produce no morphological changes in the cells (10-4 M). These data suggest that cellular transglutaminases are essential in Con A internalization into Balb/c 3T3 cells, and that microfilaments and microtubules have only a partial role.