title: Transactivation of CXCR4 by the insulin-like growth factor-1 receptor (IGF-1R) in human MDA-MB-231 breast cancer epithelial cells.
abstract: In the multimolecular environment in tissues and organs, cross-talk between growth factor and G protein-coupled receptors is likely to play an important role in both normal and pathological responses. In this report, we demonstrate transactivation of the chemokine receptor CXCR4 by the growth factor insulin-like growth factor (IGF)-1 is required for IGF-1-induced cell migration in metastatic MDA-MB-231 cells. The induction of chemotaxis in MDA-MB-231 cells by IGF-1 was inhibited by pretreatment of the cells with pertussis toxin (PTX) and by RNAi-mediated knockdown of CXCR4. Transactivation of the CXCR4 pathway by IGF-1 occurred independently of CXCL12, the chemokine ligand of CXCR4. Neither CXCR4 knockdown nor PTX had any effect on the ability of IGF-1 to activate IGF-1R, suggesting that CXCR4 and G proteins are activated subsequent to, or independently of, phosphorylation of IGF-1R by IGF-1. Coprecipitation studies revealed the presence of a constitutive complex containing IGF-1R, CXCR4, and the G protein subunits, G(i)alpha2 and Gbeta, and stimulation of MDA-MB-231 cells with IGF-1 led to the release of G(i)alpha2 and Gbeta from CXCR4. Based on our findings, we propose that CXCR4 constitutively forms a complex with IGF-1R in MDA-MB-231 cells, and that this interaction allows IGF-1 to activate migrational signaling pathways through CXCR4, G(i)alpha2 and Gbeta.
authors.affiliation: School of Molecular and Biomedical Science, the University of Adelaide, Adelaide, South Australia, Australia, 5005.
authors.forename: Chareeporn
authors.initials: C
authors.lastname: Akekawatchai
authors.forename: Jane D
authors.initials: JD
authors.lastname: Holland
authors.forename: Marina
authors.initials: M
authors.lastname: Kochetkova
authors.forename: John C
authors.initials: JC
authors.lastname: Wallace
authors.forename: Shaun R
authors.initials: SR
authors.lastname: McColl
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D002465:Cell Movement; D002633:Chemotaxis; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D006825:Hybridomas / Q000378:metabolism; D047468:Immunoprecipitation; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008024:Ligands; D051379:Mice; D008807:Mice, Inbred BALB C; D009362:Neoplasm Metastasis; D037342:Pertussis Toxin / Q000494:pharmacology; D011485:Protein Binding; D034622:RNA Interference; D017526:Receptor, IGF Type 1 / Q000378:metabolism / Q000502:physiology*; D019718:Receptors, CXCR4 / Q000378:metabolism*; D012190:Retroviridae / Q000235:genetics; D015398:Signal Transduction; D013997:Time Factors; D015533:Transcriptional Activation
chemical_list: D044387:GTP-Binding Protein beta Subunits; D008024:Ligands; D019718:Receptors, CXCR4; D007334:Insulin-Like Growth Factor I; D037342:Pertussis Toxin; D017526:Receptor, IGF Type 1; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go