Fig. 4. The GEF activity and spectrin-repeat region of Kalirin-7 are required for protrusion formation. (A) PC12 cells transfected 24 hours earlier with vector encoding inactive Kalirin-7 ND/AA were fixed and Kalirin-7 was visualized using Myc antibody (green). Filamentous actin was visualized using TRITC-phalloidin (red). No morphological differences were detected in cells expressing Kalirin-7 ND/AA. (B) PC12 cells expressing GFP fusion proteins of constitutively active (CA)-Rac or CA-RhoG were fixed after 24 hours. Fusion proteins were visualized based on GFP fluorescence (green); filamentous actin was visualized with TRITC-phalloidin (red); stars, nontransfected cells. (C) PC12 cells expressing KGEF1-7end or the KGEF1-7end T/A and T/D mutants were visualized with Myc antibody (blue), filamentous actin was visualized simultaneously. Scale bars: 10 µm.