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

Recent work has highlighted the role of specific protein-protein interactions in the retention of markers characteristic of the endoplasmic reticulum and Golgi apparatus (39, 53) , raising the possibility that specific retention of membrane proteins at their correct domain may play a significant role in sorting mechanisms (62) . Furthermore, components of the erythroid submembrane cytoskeleton, spectrin and ankyrin, which restrict the lateral mobility of red cell membrane proteins (5, 9) , have been recently described in association with the basolateral surface of kidney tubules and MDCK cells (19, 48) . In this work, we have 1. Abbreviations used in this paper: B2-m, beta-2-microglobulin; EB, extraction buffer; FRAP, fluorescence recovery after photobleaching; PFA, paraformaldehyde; TIE totally immobile fraction (percent of spots with no recovery after photobleaching); TX-100, Triton X-100. pendorf pipette at 0°C and the resultant homogenate spun at 10,000 g for 10 min in a centrifuge (model RC5C; Sorvall Instruments Div., Wilmington, DE) to pellet the nuclei.