Roles of membrane lipids in the organization of epithelial cells: Old and new problems.

Epithelial cells have characteristic membrane domains. Identification of membrane proteins playing an important role in these membrane domains has progressed and numerous studies have been performed on the functional analysis of these membrane proteins. On the other hand, the precise roles of membrane lipids in the organization of these membrane domains are largely unknown. Historically, the concept of lipid raft arose from the analysis of lipid composition of the apical membrane, and it can be said that epithelial cells are an optimal experimental model for elucidating the functions of lipids. In this review, I discuss the role of lipids in the formation of epithelial polarity and in the formation of cell membrane structures of epithelial cells such as microvilli in the apical domain, cell-cell adhesion apparatus in the lateral domain and cell-matrix adhesion in the basal domain.