Osteopontin Induces AP-1-mediated Secretion of Urokinase-type Plasminogen Activator through c-Src-dependent Epidermal Growth Factor Receptor Transactivation in Breast Cancer Cells

Riku Das,Ganapati H Mahabeleshwar,Gopal C Kundu

doi:10.1074/jbc.m310256200

Riku Das, Ganapati H Mahabeleshwar + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m310256200

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Abstract

We have recently reported that osteopontin (OPN) stimulates cell motility and nuclear factor kappaB-mediated secretion of urokinase-type plasminogen activator (uPA) through phosphatidylinositol 3-kinase/Akt signaling pathways in breast cancer cells (Das, R., Mahabeleshwar, G. H., and Kundu, G. C. (2003) J. Biol. Chem. 278, 28593-28606). However, the role(s) of OPN on AP-1-mediated uPA secretion and cell motility and the involvement of c-Src/epidermal growth factor receptor (EGFR) in these processes in breast cancer cells are not well defined. In this study we report that OPN induces alpha(v)beta(3) integrin-mediated c-Src kinase activity in both highly invasive (MDA-MB-231) and low invasive (MCF-7) breast cancer cells. Ligation of OPN with alpha(v)beta(3) integrin induces kinase activity and tyrosine phosphorylation of EGFR in MDA-MB-231 and wild type EGFR-transfected MCF-7 cells, and this was inhibited by the dominant negative form of c-Src (dn c-Src) indicating that c-Src kinase plays a crucial role in this process. OPN induces association between alpha(v)beta(3) integrin and EGFR on the cell membrane in a macromolecular form with c-Src. Furthermore, OPN induces alpha(v)beta(3) integrin/EGFR-mediated ERK1/2 phosphorylation and AP-1 activation. Moreover, dn c-Src also suppressed the OPN-induced phosphatidylinositol (PI) 3-kinase activity in these cells indicating that c-Src acts as master switch in regulating MEK/ERK1/2 and phosphatidylinositol 3-kinase/Akt signaling pathways. OPN-induced ERK phosphorylation, AP-1 activation, uPA secretion, and cell motility were suppressed when cells were transfected with dn c-Src or pretreated with alpha(v)beta(3) integrin antibody, c-Src kinase inhibitor (pp2), EGFR tyrosine kinase inhibitor (PD153035), and MEK-1 inhibitor (PD98059). To our knowledge, this is the first report that OPN induces alpha(v)beta(3) integrin-mediated AP-1 activity and uPA secretion by activating c-Src/EGFR/ERK signaling pathways and further demonstrates a functional molecular link between OPN-induced integrin/c-Src-dependent EGFR phosphorylation and ERK/AP-1-mediated uPA secretion, and all of these ultimately control the motility of breast cancer cells.

Highlights

Osteopontin (OPN)1 a non-collagenous, sialic acid-rich, and glycosylated phosphoprotein is a member of the extracellular matrix (ECM) protein family [1, 2]
This is the first report that OPN induces ␣v␤3 integrin-mediated AP-1 activity and urokinase-type plasminogen activator (uPA) secretion by activating c-Src/Epidermal growth factor receptor (EGFR)/ERK signaling pathways and further demonstrates a functional molecular link between OPNinduced integrin/c-Src-dependent EGFR phosphorylation and ERK/AP-1-mediated uPA secretion, and all of these control the motility of breast cancer cells
We demonstrate that OPN induces ␣v␤3 integrin-mediated c-Src kinase activity that phosphorylates ERK1/2 through EGFRdependent and -independent pathways

Summary

Introduction

Osteopontin (OPN)1 a non-collagenous, sialic acid-rich, and glycosylated phosphoprotein is a member of the extracellular matrix (ECM) protein family [1, 2]. OPN-induced ERK phosphorylation, AP-1 activation, uPA secretion, and cell motility were suppressed when cells were transfected with dn c-Src or pretreated with ␣v␤3 integrin antibody, c-Src kinase inhibitor (pp2), EGFR tyrosine kinase inhibitor (PD153035), and MEK-1 inhibitor (PD98059).

Results

Conclusion