Figure 4. Rac1^Ic activation on liposomes by different Dbl family proteins and association with Pak1.

(A) Differential binding of Vav2, Dbl, TrioN, Tiam1 and P-Rex1 to various liposomes. Lipo^+PIP2 is composed of PE, PC, PS, SM and PIP2. In Lipo^+PIP3, PIP2 is replaced by PIP3. (B) Efficient Rac1 activation by Dbl and Vav2 on Lipo^+PIP2. (C) Displacement from the GDI1 complex, activation by GEFs and association of Rac1^Ic with liposomes and Pak1. (D) Tiam1 but not Rac1^Ic binding to Folch III. Rac1GDP, Pak1, Tiam1, GppNHp and different liposomes were preincubated, afterwards the liposome sedimentation assay was conducted. Rac1, PAKα and Tiam1 from the liposome pellet were detected by GST antibody. (E) Rac1^Ic repulsion by PC but not PS. Liposomes (PS and PE or PC and PE) at increasing amounts of PS and PC were sedimented after incubation with Rac1^Ic. (F) Thin layer chromatography of Folch I and Folch III liposomes. Relative lipid content of Folch I and Folch III liposomes was analyzed by thin layer chromatography. PE, PS and PC as well as Folch III containing PS and PS were used as controls. CBB, coomassie brilliant blue; Ec, E. coli; Ic, insect cells; P, liposome pellet; S, supernatant.