title: Argonaute-2 expression is regulated by epidermal growth factor receptor and mitogen-activated protein kinase signaling and correlates with a transformed phenotype in breast cancer cells.
abstract: Argonaute (Ago) 2 is the catalytic engine of mammalian RNA interference, but little is known concerning the regulation of Ago2 by cell-signaling pathways. In this study we show that expression of Ago2, but not Ago1, Ago3, or Ago4, is elevated in estrogen receptor (ER) alpha-negative (ERalpha(-)) vs. ERalpha-positive (ERalpha+) breast cancer cell lines, and in ERalpha(-) breast tumors. In MCF-7 cells the low level of Ago2 was found to be dependent upon active ERalpha/estrogen signaling. Interestingly, the high expression of Ago2 in ERalpha(-) cells was severely blunted by inhibition of the epidermal growth factor (EGF) receptor/MAPK signaling pathway, using either a pharmacological MAPK kinase inhibitor, U0126, or a small interfering RNA directed against EGF receptor. Half-life studies using cycloheximide indicated that EGF enhanced, whereas U0126 decreased, Ago2 protein stability. Furthermore, a proteosome inhibitor, MG132, blocked Ago2 protein turnover. The functional consequences of elevated Ago2 levels were examined by stable transfection of ERalpha+ MCF-7 cells with full-length and truncated forms of Ago2. The full-length Ago2 transfectants displayed enhanced proliferation, reduced cell-cell adhesion, and increased migratory ability, as shown by proliferation, homotypic aggregation, and wound healing assays, respectively. Overexpression of full-length Ago2, but not truncated forms of Ago2 or an empty vector control, reduced the levels of E-cadherin, beta-catenin, and beta-actin, as well as enhanced endogenous miR-206 activity. These data indicate that Ago2 is regulated at both the transcriptional and posttranslational level, and also implicate Ago2 and enhanced micro-RNA activity in the tumorigenic progression of breast cancer cell lines.
authors.affiliation: Department of Cell Biology, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, Connecticut 06030-3505, USA.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Adams
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Claffey
authors.forename: Bruce A
authors.initials: BA
authors.lastname: White
mesh_terms: D060565:Argonaute Proteins; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D002449:Cell Aggregation; D002465:Cell Movement; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D003513:Cycloheximide / Q000494:pharmacology; D018450:Disease Progression; D066246:ErbB Receptors / Q000502:physiology*; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D035683:MicroRNAs / Q000235:genetics; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics; D014945:Wound Healing
chemical_list: C466422:AGO2 protein, human; D060565:Argonaute Proteins; D015852:Eukaryotic Initiation Factor-2; D035683:MicroRNAs; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D003513:Cycloheximide; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases
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