title: Proximal events in signaling by plasma membrane estrogen receptors.
abstract: Estradiol (E2) rapidly stimulates signal transduction from plasma membrane estrogen receptors (ER) that are G protein-coupled. This is reported to occur through the transactivation of the epidermal growth factor receptor (EGFR) or insulin-like growth factor-1 receptor, similar to other G protein-coupled receptors. Here, we define the signaling events that result in EGFR and ERK activation. E2-stimulated ERK required ER in breast cancer and endothelial cells and was substantially prevented by expression of a dominant negative EGFR or by tyrphostin AG1478, a specific inhibitor for EGFR tyrosine kinase activity. Transactivation/phosphorylation of EGFR by E2 was dependent on the rapid liberation of heparin-binding EGF (HB-EGF) from cultured MCF-7 cells and was blocked by antibodies to this ligand for EGFR. Expression of dominant negative mini-genes for Galpha(q) and Galpha(i) blocked E2-induced, EGFR-dependent ERK activation, and Gbetagamma also contributed. G protein activation led to activation of matrix metalloproteinases (MMP)-2 and -9. This resulted from Src-induced MMP activation, implicated using PP2 (Src family kinase inhibitor) or the expression of a dominant negative Src protein. Antisense oligonucleotides to MMP-2 and MMP-9 or ICI 182780 (ER antagonist) each prevented E2-induced HB-EGF liberation and ERK activation. E2 also induced AKT up-regulation in MCF-7 cells and p38beta MAP kinase activity in endothelial cells, blocked by an MMP inhibitor, GM6001, and tyrphostin AG1478. Targeting of only the E domain of ERalpha to the plasma membrane resulted in MMP activation and EGFR transactivation. Thus, specific G proteins mediate the ability of E2 to activate MMP-2 and MMP-9 via Src. This leads to HB-EGF transactivation of EGFR and signaling to multiple kinase cascades in several target cells for E2. The E domain is sufficient to enact these events, defining additional details of the important cross-talk between membrane ER and EGFR in breast cancer.
authors.affiliation: Division of Endocrinology, Veterans Affairs Medical Center, Long Beach, California 90822, USA.
authors.forename: Mahnaz
authors.initials: M
authors.lastname: Razandi
authors.forename: Ali
authors.initials: A
authors.lastname: Pedram
authors.forename: Steven T
authors.initials: ST
authors.lastname: Park
authors.forename: Ellis R
authors.initials: ER
authors.lastname: Levin
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D008024:Ligands; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D048290:Mitogen-Activated Protein Kinase 11; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011799:Quinazolines; D011960:Receptors, Estrogen / Q000378:metabolism*; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D004151:Dipeptides; D004791:Enzyme Inhibitors; D008024:Ligands; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; D016376:Oligonucleotides, Antisense; D011480:Protease Inhibitors; D011799:Quinazolines; D011960:Receptors, Estrogen; D020032:Tyrphostins; C101044:RTKI cpd; D066246:ErbB Receptors; D048290:Mitogen-Activated Protein Kinase 11; D020928:Mitogen-Activated Protein Kinases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D020962:Heterotrimeric GTP-Binding Proteins