IQGAP2 Inhibits Migration and Invasion of Gastric Cancer Cells via Elevating SHIP2 Phosphatase Activity.

Liang Xu,Xiansheng Liu,Jiegou Xu,Yuling Shao,Lin Ren,Yunyun Li,Yan Ye

doi:10.3390/ijms21061968

Abstract

Previous studies have shown reduced expression of Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) and its tumor-suppressive role in gastric cancer (GC). However, the precise role of SHIP2 in the migration and invasion of GC cells remains unclear. Here, an IQ motif containing the GTPase-activating protein 2 (IQGAP2) as a SHIP2 binding partner, was screened and identified by co-immunoprecipitation and mass spectrometry studies. While IQGAP2 ubiquitously expressed in GC cells, IQGAP2 and SHIP2 co-localized in the cytoplasm of GC cells, and this physical association was confirmed by the binding of IQGAP2 to PRD and SAM domains of SHIP2. The knockdown of either SHIP2 or IQGAP2 promoted cell migration and invasion by inhibiting SHIP2 phosphatase activity, activating Akt and subsequently increasing epithelial–mesenchymal transition (EMT). Furthermore, knockdown of IQGAP2 in SHIP2-overexpressing GC cells reversed the inhibition of cell migration and invasion by SHIP2 induction, which was associated with the suppression of elevated SHIP2 phosphatase activity. Moreover, the deletion of PRD and SAM domains of SHIP2 abrogated the interaction and restored cell migration and invasion. Collectively, these results indicate that IQGAP2 interacts with SHIP2, leading to the increment of SHIP2 phosphatase activity, and thereby inhibiting the migration and invasion of GC cells via the inactivation of Akt and reduction in EMT.

Highlights

The aberrant activation of phosphatidylinositol-3 kinase (PI3K)/ protein kinase B (PKB, known as Akt) signaling, is considered to promote tumor development and progression [1]
As reduced IQ-motif containing region (IQ) motif containing the GTPase-activating protein 2 (IQGAP2) expression was frequently observed in several cancers which correlated with poor survival, we examined the expression of IQGAP2 in 9 gastric cancer (GC) cell lines and the human normal gastric mucosal epithelial cell line GES-1 by Western blot and qRT-PCR analyses
While Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) expression was consistently lower in GC cell lines than that in GES-1, IQGAP2 was generally expressed in GES-1 and GC cell lines, except MKN-28 and NCI-N87 cell lines, at both mRNA and protein levels (Figure S1A,B)

Summary

Introduction

The aberrant activation of phosphatidylinositol-3 kinase (PI3K)/ protein kinase B (PKB, known as Akt) signaling, is considered to promote tumor development and progression [1]. Akt is an important effector protein kinase which is highly activated in nearly 80% of gastric cancers (GCs), and its activation may serve as a biomarker for the diagnosis of GC and as a molecular target for treatment [3]. It has been reported that some lipid phosphatases, such as phosphatase and tensin homolog deleted on chromosome 10 (PTEN), inositol polyphosphate 4-phosphatase type I (INPP4A) and type II (INPP4B), acting as tumor suppressors, negatively regulate the PI3K/Akt signaling via the dephosphorylation of PI(3,4)P2 and PI(3,4,5)P3 at the 3- and 4-position [4,5,6]. It has been demonstrated that 5-phosphatases, such as Src homology 2-containing inositol 5-phosphatase (SHIP) in hematopoietic cells [8], Phosphatidylinositol 4,5-Bisphosphate 5-Phosphatase (PIB5PA) in neuritis and melanoma cells [9,10], and Src homology 2-containing inositol 5-phosphatase 2 (SHIP2) in glioblastoma and GC cells, inhibit Akt activation [11,12]

Methods

Results

Conclusion