Four and a half LIM protein 2 (FHL2) negatively regulates the transcription of E-cadherin through interaction with Snail1
Résumé
E-cadherin is a hallmark of epithelial-mesenchymal transition (EMT), which plays a crucial role in cancer metastasis. We previously demonstrated that four and a half LIM protein 2 (FHL2) inhibited E-cadherin expression and promoted invasive potential and EMT in colon cancer. Here, we aim to further define the mechanism underlying the inhibition of E-cadherin by FHL2 in colon cancer. The expression profiles of FHL2 and Snail1 were first observed by Western blot, immunofluorescence and immunohistochemistry. We found that both the protein level and the cellular localisation of Snail1 were quite similar to FHL2 in colon cancer; reciprocal co-immunoprecipitation assay showed that FHL2 was able to bind Snail1 and its intact structure was required. The expression of FHL2 was positively correlated to Snail1 while negatively to E-cadherin and phospho-Snail1. FHL2 over-expression induced the accumulation of Snail1 in the nucleus. Moreover, dual luciferase assay revealed that FHL2 over-expression decreased while FHL2 siRNA increased the transcriptional activities of two E-cadherin promoter constructs which contained E-box sites (Snail1-binding elements). Mutation of E-boxes increased the transcriptional activities and FHL2 expression was involved in the function of mutation. These results suggested that FHL2 negatively regulated E-cadherin transcriptional activity through interaction with Snail1. Our study established a novel regulatory function of FHL2 and revealed a potential mechanism on promoting the process of EMT.