Selective anchoring in the specific plasma membrane domain: a role in epithelial cell polarity

Previous work has shown that epithelial surface polarity in MDCK cells is generated by intracellular sorting and vectorial delivery of apical and basal proteins (10, 41, 45, 55, 58, 64) . The fence role of tight junctions has been often stressed (17, 34, 81) . This report highlights the necessity of tight junctions to keep mobile fractions segregated and also the important contribution of intradomain restrictions to the lateral mobility for four of the five probes tested. These restrictions may be particularly effective by preventing recycling of the protein and, thus, its exposure to the lysosomal environment and degradation. Matlin and Simons (41) and Pesonen and Simons (54) have shown that VSV G protein incorporated via virus fusion to the apical surface is partially degraded and partially transcytosed to the basolateral membrane, its normal target membrane in MDCK cells infected with VSV. It is a clear prediction of the work in this report that the half-life of anchored antigens will be increased as opposed to antigens in the incorrect surface. It is also expected that recycling receptors with very low fractions in the cell surface and large intracellular pools will not be anchored in significant amounts to the cytoskeleton.