title: Ras CAAX peptidomimetic FTI-277 selectively blocks oncogenic Ras signaling by inducing cytoplasmic accumulation of inactive Ras-Raf complexes.
abstract: Ras-induced malignant transformation requires Ras farnesylation, a lipid posttranslational modification catalyzed by farnesyltransferase (FTase). Inhibitors of this enzyme have been shown to block Ras-dependent transformation, but the mechanism by which this occurs remains largely unknown. We have designed FTI-276, a peptide mimetic of the COOH-terminal Cys-Val-Ile-Met of K-Ras4B that inhibited potently FTase in vitro (IC50 = 500 pM) and was highly selective for FTase over geranylgeranyltransferase I (GGTase I) (IC50 = 50 nM). FTI-277, the methyl ester derivative of FTI-276, was extremely potent (IC50 = 100 nM) at inhibiting H-Ras, but not the geranylgeranylated Rap1A processing in whole cells. Treatment of H-Ras oncogene-transformed NIH 3T3 cells with FTI-277 blocked recruitment to the plasma membrane and subsequent activation of the serine/threonine kinase c-Raf-1 in cells transformed by farnesylated Ras (H-RasF), but not geranylgeranylated, Ras (H-RasGG). FTI-277 induced accumulation of cytoplasmic non-farnesylated H-Ras that was able to bind Raf and form cytoplasmic Ras/Raf complexes in which Raf kinase was not activated. Furthermore, FTI-277 blocked constitutive activation of mitogen-activated protein kinase (MAPK) in H-RasF, but not H-RasGG, or Raf-transformed cells. FTI-277 also inhibited oncogenic K-Ras4B processing and constitutive activation of MAPK, but the concentrations required were 100-fold higher than those needed for H-Ras inhibition. The results demonstrate that FTI-277 blocks Ras oncogenic signaling by accumulating inactive Ras/Raf complexes in the cytoplasm, hence preventing constitutive activation of the MAPK cascade.
authors.affiliation: Department of Pharmacology, School of Medicine, University of Pittsburgh, Pennsylvania 15261, USA.
authors.forename: E C
authors.initials: EC
authors.lastname: Lerner
authors.forename: Y
authors.initials: Y
authors.lastname: Qian
authors.forename: M A
authors.initials: MA
authors.lastname: Blaskovich
authors.forename: R D
authors.initials: RD
authors.lastname: Fossum
authors.forename: A
authors.initials: A
authors.lastname: Vogt
authors.forename: J
authors.initials: J
authors.lastname: Sun
authors.forename: A D
authors.initials: AD
authors.lastname: Cox
authors.forename: C J
authors.initials: CJ
authors.lastname: Der
authors.forename: A D
authors.initials: AD
authors.lastname: Hamilton
authors.forename: S M
authors.initials: SM
authors.lastname: Sebti
mesh_terms: D019883:Alkyl and Aryl Transferases; D000595:Amino Acid Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D051231:Farnesyltranstransferase; D006801:Humans; D008715:Methionine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf; D015398:Signal Transduction / Q000187:drug effects; D014166:Transferases / Q000037:antagonists & inhibitors; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; C096856:FTI 277; D009842:Oligopeptides; D011518:Proto-Oncogene Proteins; D008715:Methionine; D014166:Transferases; D019883:Alkyl and Aryl Transferases; D051231:Farnesyltranstransferase; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D018631:ras Proteins