Specific Interaction Between Lex and Lex Determinants. A Possible Basis for Cell Recognition in Preimplantation Embryos and in Embryonal Carcinoma Cells

The Lex determinant (Gal beta 1----4[Fuc alpha 1----3]GlcNAc-beta 1----R) has been implicated as having a role in mediating compaction of the mouse embryo at the morula stage (Fenderson, B., Zehavi, U., and Hakomori, S. (1984) J. Exp. Med. 160, 1591-1596). Here, we present evidence suggesting a role for Lex in F9 embryonal carcinoma cell adhesion and a mechanism for Lex recognition based on carbohydrate-carbohydrate interaction. Homotypic aggregation of F9 cells was inhibited by lacto-N-fucopentaose III, and F9 cells showed a preferential interaction with Lex liposomes. The following observations suggest that the structure capable of recognizing Lex per se on F9 cells is Lex: (i) Cell surface-labeled components solubilized in octylglucoside, affinity-bound on an Lex-octyl-Sepharose column, contained glycoproteins reactive with anti-Lex antibody. (ii) Liposomes containing Lex showed significant interaction with Lex glycolipid, but not other glycolipids, coated on a plastic surface. (iii) Liposomes containing Lex glycolipid were found to self-aggregate, whereas liposomes containing paragloboside (nLc4) or sialylparagloboside (IV3NeuAcnLc4) did not. (iv) The diffusibility of 3H-labeled lacto-N-fucopentaitol III (but not I or II), incubated with Lex liposome, from the lower to the upper Boyden chamber through a semipermeable membrane was inhibited. In all these experiments (i-iv), the interaction of Lex to Lex (or Lex to lacto-N-fucopentaose III) was clearly observed only in the presence of Ca2+ and Mg2+ and was enhanced by the presence of Mn2+. These interactions were inhibited by EDTA. The results suggest the novel hypothesis that carbohydrate-carbohydrate interactions may play an important role in controlling cell recognition during F9 cell aggregation and during embryonic development.