Figure 6.

CIB1 is required for adhesion-induced PAK1 activation, and loss of CIB1 disrupts PAK1/GTPase signaling. (A) Mock, control, or specific CIB1 siRNA-transfected REF52 cells were either held in suspension or replated onto FN-coated dishes and were lysed at the indicated times. Immunoprecipitated endogenous PAK1 was subjected to in vitro kinase assays (n = 3). (B) Control or CIB1 siRNA-transfected REF52 cell lysates were assayed for activated and total Rac1 and Cdc42. CIB1 knockdown in REF52 cells was confirmed by immunoblotting cell lysates for endogenous CIB1 expression (right) with ERK as a loading control from the same membrane. (C) REF52 cells transfected with control (left) or CIB1 siRNA (right) were replated on FN for 3 h and were stained with phalloidin. Images are representative of two separate experiments. Bars, 20 μm.