Evidence that farnesyltransferase inhibitors suppress Ras transformation by interfering with Rho activity.
Small-molecule inhibitors of the housekeeping enzyme farnesyltransferase (FT) suppress the malignant growth of Ras-transformed cells. Previous work suggested that the activity of these compounds reflected effects on actin stress fiber regulation rather than Ras inhibition. Rho proteins regulate stress fiber formation, and one member of this family, RhoB, is farnesylated in vivo. Therefore, we tested the hypothesis that interference with RhoB was the principal basis by which the peptidomimetic FT inhibitor L-739,749 suppressed Ras transformation. The half-life of RhoB was found to be approximately 2 h, supporting the possibility that it could be functionally depleted within the 18-h period required by L-739,749 to induce reversion. Cell treatment with L-739,749 disrupted the vesicular localization of RhoB but did not effect the localization of the closely related RhoA protein. Ras-transformed Rat1 cells ectopically expressing N-myristylated forms of RhoB (Myr-rhoB), whose vesicular localization was unaffected by L-739,749, were resistant to drug treatment. The protective effect of Myr-rhoB required the integrity of the RhoB effector domain and was not due to a gain-of-function effect of myristylation on cell growth. In contrast, Rat1 cells transformed by a myristylated Ras construct remained susceptible to growth inhibition by L-739,749. We concluded that Rho is necessary for Ras transformation and that FT inhibitors suppress the transformed phenotype at least in part by direct or indirect interference with Rho, possibly with RhoB itself.
Lebowitz
P F
PF
Wistar Institute, University of Pennsylvania, Philadelphia 19104, USA.
Davide
J P
JP
Prendergast
G C
GC
D019883:Alkyl and Aryl Transferases; D000818:Animals; D001483:Base Sequence; D002471:Cell Transformation, Neoplastic / Q000187:drug effects*; D002522:Chlorocebus aethiops; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D051231:Farnesyltranstransferase; D019204:GTP-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D011905:Genes, ras; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019814:Myristic Acid; D009227:Myristic Acids / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D011499:Protein Processing, Post-Translational; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D014162:Transfection; D014166:Transferases / Q000037:antagonists & inhibitors*; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein
D017931:DNA Primers; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D009227:Myristic Acids; D009842:Oligopeptides; D011994:Recombinant Proteins; D019814:Myristic Acid; C087363:L 739749; D014166:Transferases; D019883:Alkyl and Aryl Transferases; D051231:Farnesyltranstransferase; D019204:GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein