Figure 3.

Quint mutant of actopaxin is not phosphorylated upon adhesion/spreading. (A) WT actopaxin (WT) and a nonphosphorylatable mutant (Quint) of actopaxin were stably expressed in U2OS cells. WT and Quint clone cells were labeled with inorganic ³²P and either held in suspension (lanes 1 and 3) or spread on collagen-coated dishes for 2 h (lanes 2 and 4). Xpress tagged WT and Quint actopaxin proteins were immunoprecipitated, resolved on SDS-PAGE, and visualized by autoradiography. WCL are shown to indicate equivalent labeling. (B) Parental U2OS, WT, and Quint cells were spread on collagen and Xpress-tagged WT and Quint actopaxin proteins were immunoprecipitated and visualized by Western blotting. The same blot was probed with α-actinin antibodies to indicate equivalent loading.