[Functional significance of glycolipid as an important plasma membrane constituent]

Glycolipids are ubiquitous membrane components in various mammalian cells and participate in several functions through membrane. Until now, about 180 glycolipids with different carbohydrate structures have been characterized. Since alteration in glycolipids during cellular proliferation, differentiation and transformation is dramatic in general, several approaches have been attempted to clarify the meaning. Our findings that ganglioside composition in human milk is characteristically changed during the periods of lactation and that N-(O-linoleoyl-omega-hydroxylignoceroyl) sphingosyl glucose (ester CMH) in mammalian skin is characteristically synthesized during differentiation of epidermis are the examples to indicate the close association of glycolipids in cellular functions. GM3 ganglioside appeared in the later period of lactation has an activity to suppress cell growth of human breast cancer and ester CMH has an activity to promote the keratinization of epidermal cells, respectively. The observations indicate that glycolipids synthesized during cellular differentiation function as an signal transducer through plasma membrane. Structural bases of glycolipids to give such physiological activities are summarized and discussed in this communication.