Lateral movement of mast cell surface protein detected by gold-labeled anti-IgE and its relation with fodrin.

Rat mast cells were incubated with gold-conjugated concanavalin A and the movement of gold particles was observed using a polarization microscope. In resting cells, the movement of gold particles was very slow. When cells were stimulated with compound 48/80, the gold particles rapidly moved laterally, unrelated to granule extrusion. When sensitized mast cells were stimulated with gold-conjugated anti-IgE (anti-IgE-gold), patching of anti-IgE-gold was also observed. Immunofluorescence microscopy of rat mast cells stained with anti-fodrin antibody and rhodamine-phalloidin revealed that both fodrin and actin exist beneath the cell membrane forming a complicated network. After stimulation of the cells with anti-IgE-gold, the fodrin network was disrupted and thin fluorescence was observed homogeneously on the cell surface. By means of Western blotting, alpha-fodrin was detected in the membrane fraction of mast cells at the 240 kDa protein band. From the present study, it is suggested that disruption of the fodrin network may occur in association with the process leading to mast cell degranulation.