Fig. 7. SH3 domain of spectrin delays cell spreading on fibronectin. BAE cells were transiently transfected with plasmid encoding HA epitope-tagged SH3 domain of spectrin or HA epitope-tagged SH3 domain of Crk. Cells were detached and either solubilized in SDS for analysis of SH3 domain expression on western blots (A) or replated on fibronectin-coated coverslips for 1 or 3 hours, fixed and permeabilized (B,C). Cells were stained with TRITC-labeled phalloidin to detect actin filaments. Transfected cells were detected with polyclonal antibodies against HA epitope. (B) Cells transfected with spectrin SH3 domain. (C) Cells transfected with Crk SH3 domain. Arrows indicate transfected cells. Bar, 20 µm.