Changes in glycosphingolipids accompanying the differentiation of human squamous SQCC/Y1 cells

Abstract

SqCC/Y1 cells grow as a monolayer in culture and differentiate when maintained in the plateau phase; in the absence of serum these cells differentiate more rapidly. The differentiation is characterized by the stratification of the culture to form a structure consisting of several cellular layers, synthesis of specific keratins, and the attainment of the capacity to form a cornified cell membrane. The stratification process is indicative of the importance of cell-cell interactions during maturation. To study the relationship between membrane glycosphingolipids (GSLs) and the state of differentiation of SqCC/Y1 cells, GSLs were measured in cultures grown in the presence or absence of fetal calf serum. Glycolipids were isolated by diethylaminoethyl-Sephadex and Iatrobeads column chromatographies, and their distributions were determined by high-performance thin-layer chromatography. GM3 was the major ganglioside present in these cells. Other ganglioside components were tentatively identified as GM2, GM1, and GD3. Differences in ganglioside patterns were observed in differentiated cultures; the major changes were accumulation of GD3 and depletion of GM1. The predominant neutral GSLs in SqCC/Y1 cells were identified as Glc beta 1-1Cer, Gal beta 1-4Glc beta 1-1Cer, Gal beta 1-4Gal alpha 1-4Glc beta 1-1Cer, Gal NAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc beta 1-1Cer, and three unknown complex GSLs. Differentiated cultures, however, showed variations in banding patterns, which include an increase in Glc beta 1-1Cer and Gal beta 1-4Glc beta 1-1Cer and a decrease in Gal alpha 1-4Gal beta 1-4Glc beta 1-1Cer and Gal NAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc beta-1Cer. These changes, however, were not observed when the cells were grown in the presence of epidermal growth factor or retinoic acid, factors which inhibit the differentiation process. The findings demonstrate significant changes in glycolipid composition of differentiated SqCC/Y1 cells grown in the absence of serum, suggesting that these lipids may be important to the differentiated state.