Figure 5.

Ezrin mediates uPA-induced actin polymerization in dendritic spines. A, representative micrographs of dendrites of WT cerebral cortical neurons treated with vehicle (control; panels a, c, and e), or 5 nm of uPA (panels b, d, and f). 60 min later, the cells were permeabilized and treated with phalloidin (to detect F-actin already present in the cell: panels a and b) and rhodamine-coupled actin in the presence of ATP (to detect new actin polymerization; panels c and d). Panels e and f corresponds to heat maps (HM) of the micrographs depicted in panels c and d. Arrows in f denote the presence of newly formed actin in dendritic spines of uPA-treated neurons. Magnification, 40×. B, representative micrographs of ezrin staining in WT cerebral cortical neurons treated with ezrin siRNA or Sc-siRNA. Magnification, 20×. C and D, representative heat maps of new actin polymerization detected as described in A (C), and quantification of the area with newly polymerized actin (D) in dendrites from WT cerebral cortical neurons treated with ezrin siRNA (panels a and b) or Sc-SiRNA (panels c and d) followed by the addition of 5 nm of uPA or a comparable volume of PBS. Magnification, 40×. The data are expressed as means ± S.E. for n = 450 observations per experimental group.