title: Filamin A is a novel caveolin-1-dependent target in IGF-I-stimulated cancer cell migration.
abstract: Caveolin-1 is an essential structural constituent of caveolae which is involved in regulation of mitogenic signaling and oncogenesis. Caveolin-1 has been implicated in cell migration but its exact role and mechanism of action in this process remained obscure. We have previously reported that expression of caveolin-1 in stably transfected MCF-7 human breast cancer (MCF-7/Cav1) cells up-regulates phosphorylation of a putative Akt substrate protein, designated pp340 [D. Ravid, S. Maor, H. Werner, M. Liscovitch, Caveolin-1 inhibits cell detachment-induced p53 activation and anoikis by upregulation of insulin-like growth factor-I receptors and signaling, Oncogene 24 (2005) 1338-1347.]. We now show, using differential detergent extraction, SDS-PAGE and mass spectrometry, that the major protein in the pp340 band is the actin filament cross-linking protein filamin A. The identity of pp340 as filamin A was confirmed by immunoprecipitation of pp340 with specific filamin A antibodies. RT-PCR, flow cytometry and Western blot analyses show that filamin A mRNA and protein levels are respectively 3.5- and 2.5-fold higher in MCF-7/Cav1 cells than in MCF-7 cells. Basal filamin A phosphorylation on Ser-2152, normalized to total filamin A levels, is 7.8-fold higher in MCF-7/Cav1 than in MCF-7 cells. Insulin-like growth factor-I (IGF-I) stimulates phosphorylation of filamin A on Ser-2152 in MCF-7 cells and further enhances Ser-2152 phosphorylation over its already high basal level in MCF-7/Cav1 cells. The effect of IGF-I is inhibited by the PI3K inhibitor wortmannin, indicating that IGF-I-stimulated phosphorylation of filamin A occurs via the PI3K/Akt pathway. Co-immunoprecipitation experiments have confirmed a previous report showing that filamin A and caveolin-1 co-exist in a complex and have revealed the presence of active phospho-Akt in this complex. Ser-2152 phosphorylation of filamin A has been implicated in cancer cell migration. Accordingly, caveolin-1 expression dramatically enhances IGF-I-dependent MCF-7 cell migration. These data indicate that caveolin-1 specifies filamin A as a novel target for Akt-mediated filamin A Ser-2152 phosphorylation thus mediating the effects of caveolin-1 on IGF-I-induced cancer cell migration.
authors.affiliation: Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Dana
authors.initials: D
authors.lastname: Ravid
authors.forename: Dana
authors.initials: D
authors.lastname: Chuderland
authors.forename: Limor
authors.initials: L
authors.lastname: Landsman
authors.forename: Yaakov
authors.initials: Y
authors.lastname: Lavie
authors.forename: Reuven
authors.initials: R
authors.lastname: Reich
authors.forename: Mordechai
authors.initials: M
authors.lastname: Liscovitch
mesh_terms: D000595:Amino Acid Sequence / Q000502:physiology; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000503:physiopathology*; D021941:Caveolae / Q000187:drug effects / Q000378:metabolism; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics*; D003285:Contractile Proteins / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D064448:Filamins; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D046911:Macromolecular Substances / Q000378:metabolism; D013058:Mass Spectrometry; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D009361:Neoplasm Invasiveness / Q000235:genetics*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D051242:Caveolin 1; D003285:Contractile Proteins; D064448:Filamins; D007334:Insulin-Like Growth Factor I; D046911:Macromolecular Substances; D008840:Microfilament Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D012694:Serine