Fig. 4.
Inactivation of RhoA in tracheal muscle tissues causes a small reduction in ACh-induced myosin light chain (MLC) phosphorylation. MLC phosphorylation and active tension were measured in muscles strips transfected with RhoA T19N, RhoA WT, or sham-treated after stimulation with ACh for 5 min or no stimulation. A: representative immunoblots of unphosphorylated and phosphorylated 20-kDa smooth muscle MLC in unstimulated and ACh-stimulated muscle strips treated with RhoA WT or RhoA T19N or sham treated. B: mean values for MLC phosphorylation in response to ACh in sham-treated tissues and RhoA WT-treated tissues. Expression of the RhoA T19N significantly inhibited MLC phosphorylation in response to ACh (n = 11). Dashed line shows basal level of MLC phosphorylation in unstimulated tissues, which was not significantly different among treatment groups. C: mean values for MLC phosphorylation in response to ACh in untreated tissues and C3-treated tissues. Treatment with C3 significantly reduced MLC phosphorylation in response to ACh (n = 9). Dashed line shows basal level of MLC phosphorylation in unstimulated tissues, which was not significantly different among treatment groups. D: treatment of tissues with RhoA T19N (n = 11) or 10 μg/ml C3 (n = 9) significantly inhibited contractile force in response to 5-min stimulation with 10−5 M ACh relative to sham-treated or untreated smooth muscle tissues and RhoA WT-treated tissues. Values for force are normalized to values for sham-treated muscles. *Significant difference between tissues treated with RhoA T19N or C3 and sham-treated or untreated tissues (P < 0.05). Values are means ± SE.