Role of p120 in mechanical stretch-induced transferring of E-cadherin to cytoplasm in mouse alveolar epithelial cells

Objective To evaluate the role of p120-catenin protein(p120)in mechanical stretch-induced transferring of E-cadherin to cytoplasm in mouse alveolar epithelial cells. Methods Experiment Ⅰ Mouse alveolar epithelial cells(MLE-12 cells)were seeded in 6-well cell stretch plates at a density of(1.0-1.5)×106 cells/well and divided into 3 groups(n=12 each)using a random number table: control group(group C), cyclic stretch for 2 h group(group CS2)and cyclic stretch for 4 h group(group CS4). The cells underwent 20% cyclic stretch at 0.5 Hz(stretch∶intermittence =1∶1)for 2 and 4 h in CS2 and CS4 groups, respectively.The cells underwent no cyclic stretch in group C. The expression of p120, E-cadherin and phosphorylated Src kinase(p-Src)and expression of E-cadherin in cytomembrane and cytoplasma were detected by Western blot.Experiment Ⅱ MLE-12 cells were seeded in 6-well cell stretch plates at a density of (1.0-1.5)×106 cells/well and divided into 4 groups(n=6 each)using a random number table: control group(group C), cyclic stretch group(group CS), p120 small interfering RNA(siRNA)transfection group(group p120 siRNA), and p120 siRNA transfection plus cyclic stretch group(group p120 siRNA+ CS). The cells were transfected with scramble siRNA in C and CS groups, and 24 h later the cells underwent 20% cyclic stretch for 2 h at 0.5 Hz(stretch∶intermittence =1∶1)in group CS.The cells were transfected with p120 siRNA in p120 siRNA and p120 siRNA+ CS groups, and 24 h later the cells underwent 20% cyclic stretch for 2 h at 0.5 Hz(stretch∶intermittence =1∶1)in group p120 siRNA+ CS.The expression of E-cadherin in cytomembrane and cytoplasm was detected by Western blot after the end of treatment in each group. Results Experiment Ⅰ Compared with group C, the expression of p120 and E-cadherin was significantly down-regulated, the expression of p-Src was up-regulated, the expression of E-cadherin in cytomembrane was down-regulated, and the expression of E-cadherin in cytoplasm was up-regulated in CS2 and CS4 groups(P < 0.05). Compared with group CS2, the expression of p120 and E-cadherin was significantly down-regulated, the expression of p-Src was up-regulated, the expression of E-cadherin in cytomembrane was down-regulated, and the expression of E-cadherin in cytoplasm was up-regulated in group CS4(P < 0.05). Experiment Ⅱ Compared with group C, the expression of E-cadherin in cytomembrane was significantly down-regulated, and the expression of E-cadherin in cytoplasm was up-regulated in CS, p120 siRNA and p120 siRNA+ CS groups(P< 0.05). Compared with group CS or group p120 siRNA, the expression of E-cadherin in cytomembrane was significantly down-regulated, and the expression of E-cadherin in cytoplasm was up-regulated in group p120 siRNA+ CS(P<0.05). Conclusion The degradation of p120 can promote mechanical stretch-induced transferring of E-cadherin to cytoplasm in mouse alveolar epithelial cells. Key words: Biomechanics; Epithelial cells; Pulmonary alveoli; Catenins; Cadherins