Asymmetric distribution of gangliosides in rat renal brush-border and basolateral membranes

Abstract

Highly enriched brush-border and basolateral membranes isolated from rat renal cortex were used to study the distribution of endogenous gangliosides in the two distinct plasma membrane domains of epithelial cells. These two membrane domains differed in their glycolipid composition. The basolateral membranes contained more of both neutral and acidic glycolipids, expressed on a protein basis. In both membranes, the neutral glycolipids corresponding to mono-, di-, tri- and tetraglycosylceramides were present. The basolateral membranes contained more diglycosylceramide than the brush-border membranes. The major gangliosides found were G M4.G M3 and G D3 with minor amounts of G M1.G D1a. The latter were identified and qualified by sensitive iodinated cholera toxin binding assays. When the distribution of individual gangliosides was calculated as a percent of total gangliosides, the brush-border membranes were enriched with G M3, G M1 and G D1a compared to the basolateral membranes, which were enriched with G D3 and G M M4. The observation of a distinct distribution of glycolipids between brush-border and basolateral membranes of the same epithelial cell suggests that there may be a specific sorting and insertion process for epithelial plasma membrane glycolipids. In turn, asymmetric glycolipid biogenesis may reflect differences in glycolipid function between the two domains of the epithelial plasma membrane.