title: Role of the cytosolic phospholipase A2-linked cascade in signaling by an oncogenic, constitutively active Ha-Ras isoform.
abstract: Activation of Ras signaling by growth factors has been associated with gene regulation and cell proliferation. Here we characterize the contributory role of cytosolic phospholipase A(2) in the oncogenic Ha-Ras(V12) signaling pathway leading to activation of c-fos serum response element (SRE) and transformation in Rat-2 fibroblasts. Using a c-fos SRE-luciferase reporter gene, we showed that the transactivation of SRE by Ha-Ras(V12) is mainly via a Rac-linked cascade, although the Raf-mitogen-activated protein kinase cascade is required for full activation. In addition, Ha-Ras(V12)-induced DNA synthesis was significantly attenuated by microinjection of recombinant Rac(N17), a dominant negative mutant of Rac1. To identify the mediators downstream of Rac in the Ha-Ras(V12) signaling, we investigated the involvement of cytosolic phospholipase A(2). Oncogenic Ha-Ras(V12)-induced SRE activation was significantly inhibited by either pretreatment with mepacrine, a phospholipase A(2) inhibitor, or cotransfection with the antisense oligonucleotide of cytosolic phospholipase A(2). We also found cytosolic phospholipase A(2) to be situated downstream of Ha-Ras(V12) in a signal pathway leading to transformation. Together, these results are indicative of mediatory roles of Rac and cytosolic phospholipase A(2) in the signaling pathway by which Ha-Ras(V12) transactivates c-fos SRE and transformation. Our findings point to cytosolic phospholipase A(2) as a novel potential target for suppressing oncogenic Ha-Ras(V12) signaling in the cell.
authors.affiliation: Department of Life Science, Kwangju Institute of Science and Technology, Kwang-Ju 500-712, Korea.
authors.forename: M H
authors.initials: MH
authors.lastname: Yoo
authors.forename: C H
authors.initials: CH
authors.lastname: Woo
authors.forename: H J
authors.initials: HJ
authors.lastname: You
authors.forename: S H
authors.initials: SH
authors.lastname: Cho
authors.forename: B C
authors.initials: BC
authors.lastname: Kim
authors.forename: J E
authors.initials: JE
authors.lastname: Choi
authors.forename: J S
authors.initials: JS
authors.lastname: Chun
authors.forename: B H
authors.initials: BH
authors.lastname: Jhun
authors.forename: T S
authors.initials: TS
authors.lastname: Kim
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
mesh_terms: D000818:Animals; D001483:Base Sequence; D004261:DNA Replication / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D017930:Genes, Reporter; D011905:Genes, ras / Q000502:physiology*; D008156:Luciferases / Q000235:genetics; D008845:Microinjections; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D011796:Quinacrine / Q000494:pharmacology; D051381:Rats; D026362:Serum Response Factor; D015398:Signal Transduction; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D018631:ras Proteins / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D026362:Serum Response Factor; D008156:Luciferases; D019869:Phosphatidylinositol 3-Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins; D011796:Quinacrine