The activated insulin-like growth factor I receptor induces depolarization in breast epithelial cells characterized by actin filament disassembly and tyrosine dephosphorylation of FAK, Cas, and paxillin.
Insulin-like growth factor I (IGF-I) promotes the motility of different cell types. We investigated the role of IGF-I receptor (IGF-IR) signaling in locomotion of MCF-7 breast cancer epithelial cells overexpressing the wild-type IGF-IR (MCF-7/IGF-IR). Stimulation of MCF-7/IGF-IR cells with 50 ng/ml IGF-I induced disruption of the polarized cell monolayer followed by morphological transition toward a mesenchymal phenotype. Immunofluorescence staining of the cells with rhodamine-phalloidin revealed rapid disassembly of actin fibers and development of a cortical actin meshwork. Activation of phosphatidylinositol (PI)3-kinase downstream of the IGF-IR was necessary for this process, as blocking PI 3-kinase activity with the specific inhibitor LY 294002 at 10 microM prevented disruption of the filamentous actin. In parallel, IGF-IR activation induced rapid and transient tyrosine dephosphorylation of focal adhesion proteins p125 focal adhesion kinase (FAK), p130 Crk-associated substrate (Cas), and paxillin. This process required phosphotyrosine phosphatase (PTP) activity, since pretreatment of the cells with 5 microM phenylarsine oxide (PAO), an inhibitor of PTPs, rescued FAK and its associated proteins Cas and paxillin from IGF-I-induced dephosphorylation. In addition, PAO-pretreated cells were refractory to IGF-I-induced morphological transition. Thus, our findings reveal a new function of the IGF-IR, the ability to depolarize epithelial cells. In MCF-7 cells, mechanisms of IGF-IR-mediated cell depolarization involve PI 3-kinase signaling and putative PTP activities.
Guvakova
M A
MA
Kimmel Cancer Institute, Thomas Jefferson University, 233 South 10th Street, B.L.S.B. 606, Philadelphia, Pennsylvania 19107, USA. Marina.Guvakova@mail.tju.edu
Surmacz
E
E
D000199:Actins / Q000378:metabolism*; D001943:Breast Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D050719:Crk-Associated Substrate Protein; D003593:Cytoplasm / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology*; D051419:Paxillin; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism*; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins; D017526:Receptor, IGF Type 1 / Q000502:physiology*; D050717:Retinoblastoma-Like Protein p130; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured
D000199:Actins; D015815:Cell Adhesion Molecules; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D007334:Insulin-Like Growth Factor I; D051419:Paxillin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D019000:Phosphotyrosine; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; D011505:Protein-Tyrosine Kinases; D011506:Proteins; D017526:Receptor, IGF Type 1; D050717:Retinoblastoma-Like Protein p130; C493841:BCAR1 protein, human; C496061:PXN protein, human; C496050:PTK2 protein, human