title: Filamin A-mediated down-regulation of the exchange factor Ras-GRF1 correlates with decreased matrix metalloproteinase-9 expression in human melanoma cells.
abstract: The actin-binding protein filamin A (FLNa) is associated with diverse cellular processes such as cell motility and signaling through its scaffolding properties. Here we examine the effect of FLNa on the regulation of signaling pathways that control the expression of matrix metalloproteinases (MMPs). The lack of FLNa in human M2 melanoma cells was associated with constitutive and phorbol ester-induced expression and secretion of active MMP-9 in the absence of MMP-2 up-regulation. M2 cells displayed stronger MMP-9 production and activity than their M2A7 counterparts where FLNa had been stably reintroduced. Using an MMP-9 promoter construct (pMMP-9-Luc), in vitro kinase assays, and genetic and pharmacological approaches, we demonstrate that FLNa mediated transcriptional down-regulation of pMMP-9-Luc by suppressing the constitutive hyperactivity of the Ras/MAPK extracellular signal-regulated kinase (ERK) cascade. Experimental evidence indicated that this phenomenon was associated with destabilization and ubiquitylation of Ras-GRF1, a guanine nucleotide exchange factor that activates H-Ras by facilitating the release of GDP. Ectopic expression of Ras-GRF1 was accompanied by ERK activation and elevated levels of MMP-9 in M2A7 cells, whereas a catalytically inactive dominant negative Ras-GRF1, which prevented ERK activation, reduced MMP-9 expression in M2 cells. Our results indicate that expression of FLNa regulates constitutive activation of the Ras/ERK pathway partly through a Ras-GRF1 mechanism to modulate the production of MMP-9.
authors: Diabetes Section, Laboratory of Clinical Investigation, NIA, National Institutes of Health, Baltimore, Maryland 21224, USA.
authors: Tie-Nian
authors: TN
authors: Zhu
authors: Hua-Jun
authors: HJ
authors: He
authors: Sutapa
authors: S
authors: Kole
authors: Theresa
authors: T
authors: D'Souza
authors: Rachana
authors: R
authors: Agarwal
authors: Patrice J
authors: PJ
authors: Morin
authors: Michel
authors: M
authors: Bernier
mesh_terms: D002273:Carcinogens / Q000494:pharmacology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D003285:Contractile Proteins / Q000096:biosynthesis*; D015536:Down-Regulation / Q000187:drug effects; D064448:Filamins; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis*; D008545:Melanoma; D008840:Microfilament Proteins / Q000096:biosynthesis*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D020666:ras-GRF1 / Q000378:metabolism*
chemical_list: D002273:Carcinogens; D003285:Contractile Proteins; D064448:Filamins; D008840:Microfilament Proteins; D020666:ras-GRF1; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D016283:Proto-Oncogene Proteins p21(ras); D013755:Tetradecanoylphorbol Acetate