Requirement of the p130CAS-Crk Coupling for Metastasis Suppressor KAI1/CD82-mediated Inhibition of Cell Migration

Xin A Zhang,Bo He,Bin Zhou,Li Liu

doi:10.1074/jbc.m303039200

Abstract

KAI1/CD82 protein is a member of the tetraspanin superfamily and has been rediscovered as a cancer metastasis suppressor. The mechanism of KAI1/CD82-mediated suppression of cancer metastasis remains to be established. In this study, we found that migration of the metastatic prostate cancer cell line Du145 was substantially inhibited when KAI1/CD82 was expressed. The expression of focal adhesion kinase (FAK) and Lyn, a Src family tyrosine kinase and substrate of FAK, was up-regulated at both RNA and protein levels upon KAI1/CD82 expression. The activation of FAK and Lyn, however, remained unchanged in Du145-KAI1/CD82 cells. As a downstream target of FAK-Lyn signaling, the p130CAS (Crk-associated substrate) protein was decreased upon the expression of KAI1/CD82. Consequently, less p130CAS-CrkII complex, which functions as a "molecular switch" in cell motility, was formed in Du145-KAI1/CD82 cells. To confirm that the p130CAS-CrkII complex is indeed important for the motility inhibition by KAI1/CD82, overexpression of p130CAS in Du145-KAI1/CD82 cells increased the formation of p130CAS-CrkII complex and largely reversed the KAI1/CD82-mediated inhibition of cell motility. Taken together, our studies indicate the following: 1) signaling of FAK-Lyn-p130CAS-CrkII pathway is altered in KAI1/CD82-expressing cells, and 2) p130CAS-CrkII coupling is required for KAI1/CD82-mediated suppression of cell motility.

Highlights

Understanding the molecular determinants that govern cancer invasiveness and metastasis is fundamentally important for successfully diagnosing and treating metastatic cancers
Other transmembrane 4 superfamily (TM4SF) proteins such as CD81 and CD151 were equivalently expressed on the cell surfaces of both transfectants, and their levels were not altered by the KAI1/CD82 expression in Du145 cells
The diminished haptotactic cell migration in Du145-KAI1/CD82 cells was observed on both FN- and LN5-coated substrata (Fig. 2A), indicating that Du145-KAI1/CD82 has general suppressive effects on cell migration mediated by both FN- and LM-binding integrins such as ␣5␤1 and ␣3␤1, respectively

Summary

Introduction

Understanding the molecular determinants that govern cancer invasiveness and metastasis is fundamentally important for successfully diagnosing and treating metastatic cancers. Tially inhibits cell motility and/or invasiveness of these cancer cells in vitro and dramatically suppresses metastasis in animal models [1, 10, 14, 16] These observations indicate that the KAI1/CD82 expression level may determine the invasive and metastatic potential of various malignant tumors. Clustering KAI1/CD82 with its monoclonal antibody (mAb) induces cytoskeletal rearrangement and elongated cellular extension [26, 27] This signaling event is dependent on the activities of protein kinase A, protein kinase C (PKC), and Rho small GTPases but independent of Src kinase activity [26, 27]. The signaling pathway that involves Shc, MEK, and MAP kinase ERKs determines random cell migration through regulating actin-myosin assembly and cell contraction [28, 29]. The phosphatidylinositol 3-kinase (PI3-K)-Akt/PKB pathway plays an important role in the events of cell movement, such as cellular polarization during chemotaxis, by modulating FAK and Rho signaling pathways (34 –36)

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