FIGURE 4.
Vinculin phosphorylation is required for ACh-stimulated actin polymerization but not for MLC phosphorylation. Muscle tissues from sham-treated tissues and tissues expressing vinculin WT, Y1065E, or Y1065F were stimulated with 10−4 m ACh for 5 min or left unstimulated (US). A, immunoblot against MLC shows similar levels of MLC phosphorylation in tissues regardless of the expression of vinculin mutants. Phosphorylated and unphosphorylated MLC can be distinguished after urea gel electrophoresis. B, MLC phosphorylation was not significantly different among tissues subjected to different treatments (n = 4, p < 0.05). C, expression of Y1065F in smooth muscle tissues significantly inhibits the increase in the F-actin/G-actin ratio in response to ACh stimulation (n = 4, p < 0.05). Shown are means ± S.E. (error bars). *, significant difference from sham-treated tissues (p < 0.05).