Potentiation of Growth Factor Signaling by Insulin-like Growth Factor-binding Protein-3 in Breast Epithelial Cells Requires Sphingosine Kinase Activity

• Published in: The Journal of biological chemistry Vol. 284; no. 38; pp. 25542 - 25552
• Main Authors: Martin, Janet L., Lin, Mike Z., McGowan, Eileen M., Baxter, Robert C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 18.09.2009; American Society for Biochemistry and Molecular Biology
• Subjects: Breast - cytology; Breast - metabolism; Cell Line, Tumor; DNA - biosynthesis; Enzyme Activation; Epithelial Cells - cytology; Epithelial Cells - metabolism; ErbB Receptors - metabolism; Female; Gene Silencing; Humans; Insulin-Like Growth Factor Binding Protein 3; Insulin-Like Growth Factor Binding Proteins - metabolism; Insulin-Like Growth Factor I - metabolism; Lysophospholipids - metabolism; Mechanisms of Signal Transduction; Phosphotransferases (Alcohol Group Acceptor) - metabolism; Receptor, IGF Type 1 - metabolism; Receptors, Lysosphingolipid - metabolism; RNA, Small Interfering; Signal Transduction - physiology; Sphingosine - analogs & derivatives; Sphingosine - metabolism; Transcriptional Activation - physiology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.007120

We have investigated the mechanism underlying potentiation of epidermal growth factor receptor (EGFR) and type 1 insulin-like growth factor receptor (IGFR1) signaling by IGF-binding protein-3 (IGFBP-3) in MCF-10A breast epithelial cells, focusing on a possible involvement of the sphingosine kinase (SphK) system. IGFBP-3 potentiated EGF-stimulated EGF receptor activation and DNA synthesis, and this was blocked by inhibitors of SphK activity or small interference RNA-mediated silencing of SphK1, but not SphK2, expression. Similarly, IGFR1 phosphorylation and DNA synthesis stimulated by LR3-IGF-I (an IGF-I analog not bound by IGFBP-3), were enhanced by IGFBP-3, and this was blocked by SphK1 silencing. SphK1 expression and activity were stimulated by IGFBP-3 ∼2-fold over 24 h. Silencing of sphingosine 1-phosphate receptor 1 (S1P1) or S1P3, but not S1P2, abolished the effect of IGFBP-3 on EGF-stimulated EGFR activation. The effects of IGFBP-3 could be reproduced with exogenous S1P or medium conditioned by cells treated with IGFBP-3, and this was also blocked by inhibition of S1P1 and S1P3. These data indicate that potentiation of growth factor signaling by IGFBP-3 in MCF-10A cells requires SphK1 activity and S1P1/S1P3, suggesting that S1P, the product of SphK activity and ligand for S1P1 and S1P3, is the “missing link” mediating IGF and EGFR transactivation and cell growth stimulation by IGFBP-3.