DISPARATE MODULATION OF PLASMA-MEMBRANE PROTEIN LATERAL MOBILITY BY VARIOUS CELL PERMEABILIZING AGENTS

The mobility of a cell surface protein on cells osmotically swollen by treatment with several different cell permeabilizing agents retains s pecific restraints despite detachment of the plasma membrane from the cortical cytoskeleton. Fluorescence photobleaching recovery experiment s indicate that the lateral diffusion constants of immunoglobulin E (I gE)-receptor complexes on the surface of rat basophilic leukemia cells increase 2-5x following permeabilization with streptolysin 0 or digit onin, with little change in their mobile fractions. Swelling by hypo-o smotic treatment in water enhances lateral diffusion of IgE-receptor c omplexes and raises the mobile fractions to near 100%. In contrast, sw elling by treatment with filipin arrests lateral diffusion, although r otational mobility remains unhindered. Lateral mobility of a fluoresce nt lipid analogue remains unchanged under these conditions. Crosslinki ng by anti-IgE antibodies redistributes the IgE-receptor complexes int o large patches on untreated cells and on cells swollen by permeabiliz ation with streptolysin 0 or digitonin, but not on cells swollen by tr eatment with filipin. The results indicate a diversity of effects of t he various permeabilizing agents on the mobility of membrane proteins. In particular, treatment with filipin appears to reorganize the plasm a membrane into a network of fluid domains on a scale smaller than the bleaching spot size used (approximately 1.5 mum). (C) 1994 Wiley-Liss , Inc.