Disruption of Oncogenic K-Ras4B Processing and Signaling by a Potent Geranylgeranyltransferase I Inhibitor

doi:10.1074/jbc.270.45.26770

Disruption of Oncogenic K-Ras4B Processing and Signaling by a Potent Geranylgeranyltransferase I Inhibitor(*)

From the (1) Department of Pharmacology, School of Medicine and
(2) Department of Chemistry, Faculty of Arts and Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15261

** To whom reprint requests should be addressed.

Abstract

Prenylation of the carboxyl-terminal CAAX (C, cysteine; A, aliphatic acid; and X, any amino acid) of Ras is required for its biological activity. We have designed a CAAX peptidomimetic, GGTI-287, which is 10 times more potent toward inhibiting geranylgeranyltransferase I (GGTase I) in vitro (IC = 5 nM) than our previously reported farnesyltransferase inhibitor, FTI-276. In whole cells, the methyl ester derivative of GGTI-287, GGTI-286, was 25-fold more potent (IC = 2 μM) than the corresponding methyl ester of FTI-276, FTI-277, toward inhibiting the processing of the geranylgeranylated protein Rap1A. Furthermore, GGTI-286 is highly selective for geranylgeranylation over farnesylation since it inhibited the processing of farnesylated H-Ras only at much higher concentrations (IC > 30 μM). While the processing of H-Ras was very sensitive to inhibition by FTI-277 (IC = 100 nM), that of K-Ras4B was highly resistant (IC = 10 μM). In contrast, we found the processing of K-Ras4B to be much more sensitive to GGTI-286 (IC = 2 μM). Furthermore, oncogenic K-Ras4B stimulation of mitogen-activated protein (MAP) kinase was inhibited potently by GGTI-286 (IC = 1 μM) but weakly by FTI-277 (IC = 30 μM). Significant inhibition of oncogenic K-Ras4B stimulation of MAP kinase by GGTI-286 occurred at concentrations (1-3 μM) that did not inhibit oncogenic H-Ras stimulation of MAP kinase. The data presented in this study provide the first demonstration of selective disruption of oncogenic K-Ras4B processing and signaling by a CAAX peptidomimetic. The higher sensitivity of K-Ras4B toward a GGTase I inhibitor has a tremendous impact on future research directions targeting Ras in anticancer therapy.

Footnotes

↵^§ Recipient of a predoctoral fellowship award from the United States Army Medical Research and Development Command.
↵^¶ Recipient of a predoctoral fellowship from the Andrew Mellon Foundation.
↵* This work was supported by National Institutes of Health Grants U19-CA677701 and CA-55823. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

MAP

mitogen-activated protein

FTase

farnesyltransferase

GGTase I

geranylgeranyltransferase I

PAGE

polyacrylamide gel electrophoresis

CAAX

tetrapeptide where C is cysteine, A is aliphatic amino acid, and X is serine or methionine

FTI

farnesyltransferase inhibitor

GGTI

geranylgeranyltransferase inhibitor.
- Received August 29, 1995.
- Revision received September 15, 1995.