Cell contact-dependent ganglioside changes in mouse 3T3 gibroblasts and a suppressed sialidase activity on cell contact.

Certain enzyme activities for synthesis and degradation of gangliosides and the chemical quantity and incorporation of radioactivity from [14C] galactose into gangliosides have been studied in 3T3 cells and their transformed counterparts at various cell population densities. The chemical quantity of and the incorporation of radioactivity into GD1a ganglioside increased at the early stage of cell contact ("contact response" of ganglisoide), whereas response was not detectable in transformed 3T3 cells at any stage of cell contact. These phenomena were reproduced in five separate qualitative analyses and two quantitative determinations of gangliosides. As the basis of these phenomena, a membrane-bound sialidase activity which acted on gangliosides was suppressed in 3T3 cells at the "touching" stage of cell-to-cell contact. Transformed cells did not display the change of sialidase activity at any stage of cell contact.