ABSTRACT
Objective To investigate the expression and distribution of Cdc42-interacting protein 4 (CIP4) in renal fibrotic tissue,and the interaction between CIP4 and β-catenin in transforming growth factor β1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) model of HK-2 cell line.Methods In vivo,the model of renal fibrosis was induced by 5/6 subtotal nephrectomy in rat.Masson staining was used to evaluate the level of renal tissue fibrosis.The expression and distribution of CIP4 was detected by immunohistochemistry.In vitro,the EMT model of HK-2 cell line was induced by TGF-β1 (10 μg/L) for 72 h.Western blotting was used to observe the expression of E-cadherin,β-catenin,CIP4 and α-SMA.Colocalization and interaction of CIP4 and β-catenin were detected by immunofluorescence and immunoprecipitation respectively.Results Compared to sham group,CIP4 expression was increased in group of 5/6 subtotal nephrectomy,CIP4 was mainly distributed in basolateral side of renal tubular epithelia.In vitro,expressions of α-SMA and CIP4 were increased in HK-2 cells stimulated by TGF-β1 for 72 h (2.5and 1.8 folds,respectively) (all P＜0.05),expression of E-cadherin was decreased(P＜0.05).Partial colocalization between CIP4 and β-catenin was detected by immunofluorescence.In control group,CIP4 and β-catenin partially colocalized at the cell membrane.Mter the stimulation of TGF-β1,translocation to nucleus of CIP4 and β-catenin were increased,and partially colocalized in nucleus.The interaction between CIP4 and β-catenin was observed by immunoprecipitation in both control and TGF-β1 stimulated groups.Conclusions Expression of CIP4 in renal fibrotic tissue is increased,which is mainly distributed in basolateral side of renal tubular epithelia.CIP4 and βcatenin partially colocalize and interact with each other.CIP4 may play a role in EMT process through the interaction with β-catenin.
ABSTRACT
Objective To observe the expression and localization of CIP4 (Cdc42 interacting protein-4) in the renal fibrosis and the effect of CIP4 on the expression of E-cadherin,vimentin and β-catenin tyrosine phosphorylation. Methods In vitro, the human tubular epithelial cells (HK-2 cell line) were cultured with 10 μg / L TGF-β1 for 72 h. The protein expressions of CIP4, E-cadherin, vimentin and β-catenin tyrosine phosphorylation were measured by Western blotting; the expression of CIP4 mRNA was detected by RT-PCR. The intracellular distribution of CIP4 was observe by confocal microscope. In vivo, Masson staining was used to evaluate the level of renal fibrosis; the expression and distribution of CIP4 in renal tissue were detected by immunohistochemistry. HK-2 cells were transfected with pcDNA3. 1-CIP via lipofectamine 2000. The expressions of E-cadherin, vimentin and β-catenin tyrosine phosphorylation level in the transfected cells were detected by Western blotting. Results The expressions of CIP4 mRNA and protein were up-regulated in renal tubular EMT cells. Most of CIP4 protein localized in cell membrane, and some was in cytoplasm. After stimulation by TGF-β1, the expression of CIP4 protein both in cytoplasm and nucleus was greatly increased (P ＜0.05),especially in cytoplasm. In vivo, CIP4 was expressed in renal tubular epithelia, but little expressed in glomeruli. In renal from 5/6 nephrectomized rats, CIP4 expression was significantly increased. In the CIP4 transfectants, the expression of CIP4, vimentin and β-catenin tyrosine phosphorylation level were up-regulated (P ＜0.05), but E-cadherin expression was suppressed (P ＜0.05).Conclusion The overexpression of CIP4 is likely to take part in the epithelial-to-mesenchymal transition process, thereby promoting the renal fibrosis.