Erbin inhibits TGF-β1-induced EMT in renal tubular epithelial cells through an ERK-dependent pathway

Epithelial-to-mesenchymal transition (EMT) plays a crucial role in the progression of renal interstitial fibrosis, which finally leads to renal failure. Erbin, a member of LAP family, is recently reported to inhibit Smads and ERK pathway which are two important types of intracellular signaling involved in TGF-beta 1-induced EMT. However, the role of Erbin in the regulation of EMT and the underlying mechanisms remain to be fully understood. To that end, we aimed to evaluate the expression of Erbin in renal interstitial fibrosis and the potential role of Erbin in tubular EMT stimulated by TGF-beta 1. In this study we demonstrated that the expression of Erbin was upregulated in the tubular epithelia of 5/6-nephrectomized rats. We also showed here that TGF-beta 1 upregulated Erbin expression in NRK52E cells during their EMT phenotype acquisition. Importantly, elevated expression of Erbin inhibited ERK signaling and partial reversed EMT stimulated by TGF-beta 1. In the mean time, reducing Erbin expression enhanced ERK phosphorylation, promoted the E-cadherin suppression, and induced alpha-SMA expression and fibronection secretion in response to TGF-beta 1, which could be rescued if cells were treated with the inhibitor of MEK1/2 U0126. However, in the absence of TGF-beta 1, Erbin failed to affect ERK activation and EMT process. These results suggest that Erbin is a negative feedback molecule induced by TGF-beta 1 and inhibits TGF-beta 1-induced EMT via ERK signaling pathway.