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

These domain-specific phenomena are reminiscent of the lectin-or substrate-induced modulation of lateral diffusion reported for nonpolarized cells (20) , so-called "global modulation: Such modulation of mobility was also observed for molecules of N-CAM upon differentiation of neuroblastoma cells (57) . We were not able to find differences in total cellular TX-100-extractable fractions of four membrane antigens between 1-and 4-d confluent monolayers. Nonetheless, two of them are more polarized in the latter stage. These determinations may be partially masked by an intracellular pool of membrane antigens, presumably TX-100 soluble. However, they support the notion that there is a mobile and TX-100soluble fraction of these antigens even in the fully polarized stage. We speculate that this fraction may be important for turnover of plasma membrane proteins.