Fig. 4. Formation of spectrin-containing clusters is dependent on calpain activity. BAE cells were detached and replated on fibronectin-coated coverslips in the presence of calpeptin (100 µg/ml) or MDL (150 µM) for 30 minutes, 1 hour or 8 hours, fixed, permeabilized and stained with polyclonal antibodies against spectrin and monoclonal antibody against vß3 integrin. Bar, 10 µm.