SHP2 Positively Regulates TGFβ1-induced Epithelial-Mesenchymal Transition Modulated by Its Novel Interacting Protein Hook1

Shuomin Li,Linrun Wang,Qingwei Zhao,Yu Liu,Lingjuan He,Qinqin Xu,Xu Sun,Li Teng,Hongqiang Cheng,Yuehai Ke

doi:10.1074/jbc.m113.546077

Abstract

The epithelial-mesenchymal transition (EMT) is an essential process for embryogenesis. It also plays a critical role in the initiation of tumor metastasis. Src homology 2 (SH2)-domain containing protein-tyrosine phosphatase-2 (SHP2) is a ubiquitously expressed protein-tyrosine phosphatase and is mutated in many tumors. However, its functional role in tumor metastasis remains largely unknown. We found that TGFβ1-induced EMT in lung epithelial A549 cells was partially blocked when SHP2 was decreased by transfected siRNA. The constitutively active form (E76V) promoted EMT while the phosphatase-dead mutation (C459S) and the SHP2 inhibitor PHPS1 blocked EMT, which further demonstrated that the phosphatase activity of SHP2 was required for promoting TGFβ1-induced EMT. Using the protein-tyrosine phosphatase domain of SHP2 as bait, we identified a novel SHP2-interacting protein Hook1. Hook1 was down-regulated during EMT in A549 cells. Overexpression of Hook1 inhibited EMT while knockdown of Hook1 promoted EMT. Moreover, both the protein-tyrosine phosphatase domain and N-terminal SH2 domain of SHP2 directly interacted with Hook1. Down-regulation of Hook1 increased SHP2 activity. These results suggested that Hook1 was an endogenous negative regulator of SHP2 phosphatase activity. Our data showed that the protein-tyrosine phosphatase SHP2 was involved in the process of EMT and Hook1 repressed EMT by regulating the activation of SHP2. SHP2-Hook1 complex may play important roles in tumor metastases by regulating EMT in cancer cells.

Highlights

In the process of epithelial-mesenchymal transition (EMT) in A549 cells induced by TGF␤1, the expression of SHP2 did not change, the activation of ERK pathway was dramatically induced after TGF␤1 stimulation for 48 h (Fig. 1D)
EMT is a form of transformation, which is important for cancer cells to obtain the capacities of migration and invasion
Our data showed that SHP2 positively regulated TGF␤1induced EMT in A549 cells (Fig. 1, F–J)

Summary

Background

PTP and N-SH2 domains of SHP2 interact with Hook[1], which negatively regulates TGF␤1-induced EMT. Significance: SHP2 plays important roles in tumor metastases due to promoting EMT in cancer cells. SHP2-Hook[1] complex may play important roles in tumor metastases by regulating EMT in cancer cells. Previous reports have shown that the Src homology 2 (SH2)-domain containing protein-tyrosine phosphatase-2 (SHP2) plays important roles in cell differentiation, indicating that it might participate in the regulation of EMT (4 – 6). SHP2, a member of the non-receptor protein-tyrosine phosphatase family, participates in many signal transduction and activation of the Ras-ERK signaling pathway, mostly beginning by EGF binding to the EGF receptor (7, 8) This suggests that SHP2 may play regulatory roles in the EMT process (9, 10). The novel interacting protein Hook[1], interacting with SHP2 N-terminal SH2 and PTP domains, negatively regulated EMT

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION