Ras CAAXPeptidomimetic FTI-277 Selectively Blocks Oncogenic Ras Signaling by Inducing Cytoplasmic Accumulation of Inactive Ras-Raf Complexes

Edwina C. Lerner, Yimin Qian, Michelle A. Blaskovich, Renae D. Fossum, Andreas Vogt, Jiazhi Sun, Adrienne D. Cox, Channing J. Der, Andrew D. Hamilton, Saïd M. Sebti
1995 Journal of Biological Chemistry  
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 (IC 50 ‫؍‬ 500 pM) and was highly selective for FTase over
more » ... geranylgeranyltransferase I (GGTase I) (IC 50 ‫؍‬ 50 nM). FTI-277, the methyl ester derivative of FTI-276, was extremely potent (IC 50 ‫؍‬ 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.
doi:10.1074/jbc.270.45.26802 pmid:7592920 fatcat:lzfsoj2udjb6hdpc4yofd54fgy