Human melanoma cell attachment involves an Arg-Gly-Asp-directed adhesion receptor and the disialoganglioside GD2

The disialogangliosides GD2 and GD3 play a major role in the ability of human melanoma cells to attach to Arg-Gly-Asp-containing substrates such as fibronectin and vitronectin, since pretreatment of these cells with monoclonal antibodies to the oligosaccharide of GD2 and GD3 can inhibit their attachment and spreading on such adhesive proteins. This report demonstrates that human melanoma cells (M21) synthesize and express a glycoprotein receptor that shares antigenic epitopes with the vitronectin receptor on human fibroblasts and is capable of specifically recognizing the Gly-Arg-Gly-Asp-Ser-Pro sequence. Biochemical evidence is presented indicating that the vitronectin receptor on M21 human melanoma cells contains associated calcium and GD2. This ganglioside copurified with the glycoprotein receptor for vitronectin on affinity columns containing either an Arg-Gly-Asp-containing peptide, Concanavalin A, or lentil lectin. This major Arg-Gly-Asp-directed receptor on M21 cells could be metabolically labeled with 45Ca++. Chelation of this ion with EDTA caused the dissociation of GD2 from the receptor and rendered the remaining glycoprotein incapable of binding to an Arg-Gly-Asp containing peptide. Reconstitution experiments demonstrated a requirement for calcium and not magnesium for receptor binding to Arg-Gly-Asp and indicated that addition of ganglioside can enhance this interaction.