Fig. 4.

Short-RPTPβ ECD acts as a repulsive substrate for glioblastoma attachment. (A) Short-RPTPβ ECD was expressed in a baculovirus system and purified. Coomassie staining of short-RPTPβ ECD (10 μg) and phosphacan mix (10 μg) indicates the relative purity and size of these proteins. Short-RPTPβ ECD runs at about 85 kDa, and the phosphacan mix runs as a large-molecular-weight complex at >300 kDa. (B) U373 cells were plated and allowed to attach for 30 min onto plates coated with BSA, phosphacan, and short-RPTPβ ECD. Following three washes with PBS, the number of viable adherent cells was measured. Short RPTPβ-ECD inhibits binding of U373 cells slightly less effectively than phosphacan (error bars, ±SD; ** P < 0.005; *P < 0.05). (C) U373 cells were plated and allowed to attach for 30 min onto plates coated with BSA, phosphacan, and short-RPTPβ ECD. The cells were then stained with Alexa 594 phalloidin (Molecular Probes) to detect F-actin and cytoskeletal organization. Representative images were taken with a fluorescent microscope.