Studies on the Glycosphingolipids of Normal and Virally Transformed 3T3 Mouse Fibroblasts

Abstract

Abstract The neutral glycosphingolipids and the gangliosides of normal 3T3 mouse fibroblasts, one polyoma-transformed, and three SV40-transformed clonal isolates have been examined. The normal 3T3 cells contained mono- and dihexosylceramides and a complex pattern of gangliosides. The carbohydrate and fatty acid compositions of these neutral glycosphingolipids and of the principal gangliosides were determined and partial structures for these compounds are proposed. One polyoma-transformed (3T3-Py6) and one SV40-transformed derivative cell line (3T3-SV-479) were found to exhibit marked simplification of ganglioside pattern as compared with the control cells, a finding in agreement with that of a previous study (Brady, R. O., and Mora, P. T. (1970) Biochim. Biophys. Acta 218, 308). Two other clonal isolates of SV40-transformed cells (3T3-SV-A26 and 3T3-SV-CE56) exhibited complex patterns of gangliosides, generally similar to those found in the control cells, but showing a marked increase of the ganglioside GD1a. Possible explanations for these observations are discussed. No correlation was detected between the complexity of the glycosphingolipid pattern and the saturation density obtained with the cells studied. Experiments using [1-14C]-glucosamine as a precursor confirmed the ability of control and transformed cells to synthesize their complement of gangliosides. Plasma membrane fractions of 3T3 cells were found to be enriched 3-fold with respect to the various gangliosides detected in the whole cells. Certain gangliosides of the control and 3T3-Py6 cells were susceptible to the action of neuraminidase in a membrane-bound state.