title: Classic Ras Proteins Promote Proliferation and Survival via Distinct Phosphoproteome Alterations in Neurofibromin-Null Malignant Peripheral Nerve Sheath Tumor Cells.
abstract: Neurofibromin, the tumor suppressor encoded by the neurofibromatosis type 1 (NF1) gene, potentially suppresses the activation of H-Ras, N-Ras, and K-Ras. However, it is not known whether these classic Ras proteins are hyperactivated in NF1-null nerve sheath tumors, how they contribute to tumorigenesis, and what signaling pathways mediate their effects. Here we show that H-Ras, N-Ras, and K-Ras are coexpressed with their activators (guanine nucleotide exchange factors) in neurofibromin-null malignant peripheral nerve sheath tumor (MPNST) cells, and that all 3 Ras proteins are activated. Dominant negative (DN) H-Ras, a pan-inhibitor of the classic Ras family, inhibited MPNST proliferation and survival, but not migration. However, NF1-null MPNST cells were variably dependent on individual Ras proteins. In some lines, ablation of H-Ras, N-Ras, and/or K-Ras inhibited mitogenesis. In others, ablation of a single Ras protein had no effect on proliferation; in these lines, ablation of a single Ras protein resulted in compensatory increases in the activation and/or expression of other Ras proteins. Using mass spectrometry-based phosphoproteomics, we identified 7 signaling networks affecting morphology, proliferation, and survival that are regulated by DN H-Ras. Thus, neurofibromin loss activates multiple classic Ras proteins that promote proliferation and survival by regulating several distinct signaling cascades.
authors.affiliation: From the Departments of Cell Biology (NMB, SLC), Pathology (SJB, SNB, SLC), and Pharmacology and Toxicology (SB, LSW) and the Medical Scientist Training Program (NMB, SNB), University of Alabama at Birmingham, Birmingham, Alabama; and Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina (AMP, JFL, SLC).
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Brossier
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Prechtl
authors.forename: Jody Fromm
authors.initials: JF
authors.lastname: Longo
authors.forename: Stephen
authors.initials: S
authors.lastname: Barnes
authors.forename: Landon S
authors.initials: LS
authors.lastname: Wilson
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Byer
authors.forename: Stephanie N
authors.initials: SN
authors.lastname: Brosius
authors.forename: Steven L
authors.initials: SL
authors.lastname: Carroll
mesh_terms: D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation / Q000187:drug effects / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002853:Chromatography, Liquid; D004318:Doxycycline / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D009154:Mutation / Q000235:genetics; D018317:Nerve Sheath Neoplasms / Q000473:pathology; D009456:Neurofibromatosis 1 / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000502:physiology; D053719:Tandem Mass Spectrometry; D014162:Transfection; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D010750:Phosphoproteins; D034741:RNA, Small Interfering; D018631:ras Proteins; D004318:Doxycycline