Figure 8.

R-Ras GAP activity of endogenous Plexin-B1 is required for Sema4D-mediated inhibition of integrin-mediated PC12 cell migration. (A) Schematic representation of the Plexin-B1–N-Cyt–GGA construct used in the experiment. The Rnd1 binding region and the R-Ras GAP domains (C1 and C2) are indicated. Letters indicate the specific amino acid residues within domains (A, Ala; F, Phe; G, Gly; L, Leu; P, Pro; R, Arg; V, Val), and numbers indicate amino acid positions within the sequence. (B) Relative activity of R-Ras was determined as described in the legend to Fig. 5 B. (C) PC12 cells transfected with GFP alone or GFP plus HA–Plexin-B1–N-Cyt–GGA were tested in the transwell assay in either the presence or absence of Sema4D. (D) Relative cell migration was determined by the number of the migrated cells normalized to the total number of cells. Migrated cells were visualized by the fluorescence of GFP. Results are the means ± SEM of three independent experiments. Bar, 1 mm.