Reversal of the Ras-induced transformed phenotype by HR12, a novel Ras farnesylation inhibitor, is mediated by the Mek/Erk pathway

Citation
H. Reuveni et al., Reversal of the Ras-induced transformed phenotype by HR12, a novel Ras farnesylation inhibitor, is mediated by the Mek/Erk pathway, J CELL BIOL, 151(6), 2000, pp. 1179-1192
Citations number
69
Categorie Soggetti
Cell & Developmental Biology
Journal title
JOURNAL OF CELL BIOLOGY
ISSN journal
00219525 → ACNP
Volume
151
Issue
6
Year of publication
2000
Pages
1179 - 1192
Database
ISI
SICI code
0021-9525(200012)151:6<1179:ROTRTP>2.0.ZU;2-Z
Abstract
We have used the selective farnesylation inhibitor HR12 [cysteine-N(methyl) valine-N(cyclohexyl) glycine-methionine-O-methyl-ester] to study the role o f oncogenic Ras in cytoskeletal reorganization in Ha-ras(V12)- transformed Rat1 cells (Rat1/ras). Application of HR12 resulted in complete restoration of the cytoskeleton and associated cell adhesions disrupted by oncogenic R as. This included an increase in the number and size of focal adhesions, ac companied by massive stress fiber formation and enhanced tyrosine phosphory lation. Furthermore, HR12 induced assembly of adherens junctions and dramat ically elevated the level of the junctional components, cadherin and beta - catenin. HR12 was unable to restore the nontransformed phenotype in cells e xpressing farnesylation-independent, myristylated Ras. Examination of the m ain Ras-regulated signaling pathways revealed that HR12 induced a dose- and time-dependent decline in Erk1&2 activation (t(1/2) similar to 6 h), which correlated with the accumulation of nonfarnesylated oncogenic-Ras. Inhibit ion of the Mek/Erk pathway in Rat1/ ras cells, using the Mek inhibitor, PD9 8059, resulted in complete cytoskeletal recovery, indistinguishable from th at induced by HR12. Moreover, a constitutively active Mek mimicked the effe ct of ras transformation in Rat1 cells, and prevented HR12-induced cytoskel etal effects in Rat1/ras cells. No such effects were observed after treatme nt of Rat1/ras cells with the phosphatidylinositol 3-kinase inhibitor LY294 002. These findings establish the Mek/Erk pathway as the dominant pathway i nvolved in conferring the cytoskeletal and junctional manifestations of the Ras-induced transformed phenotype.