Figure 4.

MP1 knockdown modestly delays PAK autophosphorylation in response to FN and decreases paxillin expression. A) DU145 cells transfected with control or MP1 siRNA were plated on FN for the times indicated. Whole cell lysates were analyzed by immunoblot for PAK phosphorylation of MEK1 (pS298 MEK1) and PAK1-3 autophosphroylation on S141. B) Cells transfected with control or MP1 siRNA were lysed in RIPA (RIPA) or SDS-PAGE (SDS) loading buffer (see Methods) and expression of focal adhesion proteins was assessed by immunoblot. C, Control siRNA; M, MP1 siRNA. Paxillin expression was quantified by densitometry and is expressed as percent of control for each lysis buffer. C) Cells transfected with control, MP1, or p14 siRNA were analyzed for vinculin, paxillin, MP1 and p14 expression.