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Requirement of phosphatidylinositol-3 kinase for epithelial cell migration activated by human macrophage stimulating
M H Wang1, F A Montero-Julian, I Dauny
1Laboratory of Immunobiology, National Cancer Institute and Frederick Cancer Research and Development Center, National Institutes of Health, Frederick, Maryland 21702, USA.
Abstract:
Macrophage stimulating protein (MSP) is a ligand for the RON receptor protein tyrosine kinase. Activation of RON in murine resident macrophages results in cell shape change and migration. We studied cell movement induced by MSP in different types of human epithelial cells and the possible role of phosphatidylinositol-3 (PI-3) kinase in RON-mediated signal transduction. We observed specific and saturable binding of 125I-MSP to RON on several epithelial cell lines. In addition to activation and phosphorylation of RON, MSP also induced tyrosine phosphorylation of the PI-3 kinase p85 subunit in a time-dependent manner, with a peak at 15 min. Moreover, phosphorylated RON formed a complex with PI-3 kinase in both HK-NOC keratinocyte and RON cDNA-transfected MDCK cells. An in vitro protein interaction assay confirmed that PI-3 kinase from a lysate of MSP-activated cells bound to pure RON protein. MSP, at a concentration range of 1 to 5 nM, induced migration of three epithelial cell lines. This effect was inhibited by wortmannin, a specific inhibitor for PI-3 kinase, with an IC50 of 10 nM. MSP-induced shape change in murine resident peritoneal macrophages was also abolished by wortmannin. These data suggest that activation of PI-3 kinase is required for MSP-induced epithelial cell migration. The stimulation by MSP of epithelial cell movement may have implications for tissue repair, wound healing, and tumor metastasis.
Insights
Macrophage stimulating protein (MSP) activates the RON receptor, triggering epithelial cell migration. This process requires phosphatidylinositol-3 (PI-3) kinase activation, suggesting roles in tissue repair and metastasis.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Macrophage stimulating protein (MSP) binds to the RON receptor tyrosine kinase.
- RON activation in macrophages causes shape change and migration.
- The role of PI-3 kinase in MSP-induced RON signaling in epithelial cells was investigated.
Purpose of the Study:
- To investigate MSP-induced cell movement in human epithelial cells.
- To determine the role of phosphatidylinositol-3 (PI-3) kinase in RON-mediated signal transduction.
- To explore the implications of MSP-stimulated epithelial cell movement.
Main Methods:
- Studied 125I-MSP binding to RON on epithelial cell lines.
- Analyzed RON and PI-3 kinase phosphorylation and complex formation.
- Assessed MSP-induced cell migration and shape change, using wortmannin as an inhibitor.
Main Results:
- Specific binding of MSP to RON was observed on epithelial cells.
- MSP induced RON and PI-3 kinase (p85 subunit) tyrosine phosphorylation.
- MSP stimulated epithelial cell migration, an effect inhibited by wortmannin, indicating PI-3 kinase dependence.
Conclusions:
- Activation of PI-3 kinase is essential for MSP-induced epithelial cell migration.
- MSP-stimulated epithelial cell movement has potential implications for wound healing and tumor metastasis.