Introduction To Protein Farnesyltransferase Structure

High resolution three-dimensional crystal structures of protein farnesyltransferase (FTase) complexed with substrates and inhibitors provide a framework for understanding the molecular basis of substrate specificity and mechanism and may facilitate the development of improved chemotherapeutics. The 2.25A resolution crystal structure of rat FTase provided the first structural information on any protein prenyltransferase enzyme (1). Rat FTase shares 93 sequence identity with the human enzyme and...

Substrate Binding And Recognition

In the X-ray co-crystal structure of rat FTase complexed with FPP, the isoprenoid moiety binds in an extended conformation along one side of the funnel-shaped hydro-phobic cavity of the a-a barrel of the P-subunit (2). This cavity is lined with conserved aromatic residues including W303P, Y251P, W102P, Y205P, and Y200a that make hydrophobic interactions with the isoprenoid. Strictly conserved R202P also forms a hydrophobic interaction with the isoprenoid and is stabilized by interactions with...

Peptidomimetic Inhibitors Of Ftase

Because CAAX tetrapeptides are farnesylated by FTase as efficiently as the corresponding full-length protein and also are potent (10-200 nM) competitive inhibitors of FTase (22), several groups have targeted the CAAX tetrapeptide as an anticancer drug development strategy. The major efforts have involved improving stability of the tetrapeptides toward proteolytic degradation and increasing their cellular uptake (23). Our strategy focused on the CA1A2X motif from K-Ras4B CVIM. We reasoned that...

Biological Evaluation Of The Histidylbenzylglycinamides

Lessons Learned from Predecessors to PD 169451 Table 1 summarizes the biological properties ofthe key compounds that led to the synthesis of PD 169451. Efforts to improve the cellular permeability of this chemical series resulted in PD 152440, which inhibited cellular farnesylation at 5 yM, but proved to be nonselective against FTase relative to other prenylation enzymes (see Fig. 3). Because an increasing number ofliterature reports indicated that K-Ras was an efficient substrate for...

Evolution Of The Histidylbenzylglycinamide Series

Mass screening of the Parke-Davis chemical library resulted in the identification of PD 083176 as a potent inhibitor of rat brain FTase, as evidenced by an IC50 of 20 nM. As shown in Fig. 1, the structure of this protected pentapeptide, which does not contain a cysteine residue, is uniquely different from the CAAX-based tetrapeptides of compara ble potency reportedby Brown and Goldstein (8). Presumably because ofthe high degree ofhydrophobicity ofPD 083176, this inhibitor proved to be...

Cancer Drug Discovery and Development Beverly A Teicher Series Editor

Matrix Metalloproteinase Inhibitors in Cancer Therapy, edited by Neil J. Clendeninn and Krzysztof Appelt, 2000 9. Tumor Suppresor Genes in Human Cancer, edited by David E. Fisher, 2000 8. Farnesyltransferase Inhibitors in Cancer Therapy, edited by Said M. Sebti and Andrew Hamilton, 2000 7. Platinum-Based Drugs in Cancer Therapy, edited by Lloyd R. Kelland and Nicholas P. Farrell, 2000 6. Signaling Networks and Cell Cycle Control The Molecular Basis of Cancer and Other Diseases, edited by J....

Selective Inhibition Of Farnesylation And Geranylgeranylation In Vitro And In Whole Cells

The potency of the FTIs and GGTIs that we have made (Fig. 1) to inhibit FTase and GGTase I was determined as described previously (49,52,55). Table 2 shows the IC50 values ofthe inhibitors. FTI-276 (IC50 0.5 nM) is three times more potent than FTI-2148 (IC50 1.4 nM) at inhibiting FTase. Table 2 shows that GGTI-2154 (IC50 2l nM) is 2.5 times more potent than GGTI-297 (IC50 55 nM) at inhibiting GGTase I. Table 2 also demonstrates that both FTIs are highly selective for FTase over GGTase I,...

References

TropicalDisease Research Progress 1995-1996. World Health Organization, Geneva. 1997. 2. Croft SL. The current status of antiparasitic chemotherapy. Parasitology 1997 114 S3-S15. 3. Glomset JA, Gelb MH, Farnsworth CC. Prenyl protein in eukaryotic cells a new type of membrane anchor. Trends Biochem Sci 1990 15 139-142. 4. Glomset JA, Farnsworth CC. Role of protein modification reactions in programming interactions between ras-related GTPases and cell membranes. Annu...

Induction of Radiation Resistance by the 24kDa Form of bFGF

Clonogenic Survival Curves

In order to examine the relative contributions of the CUG- or AUG-initiated forms in the radioprotective effect attributed to bFGF, cDNA encoding each form were trans-fected in HeLa cells. HeLa cells were transfected with retroviral vector PINA encoding the 24-kDa form (HeLa 3A cells), or the 18-kDa bFGF form (HeLa 5A cells), or the vector alone (HeLa PINA cells). Figure 17 shows the bFGF protein expression profile of the selected clones. Four bands were detected in HeLa and HeLa PINA cells...

Evidence of a Role for Growth Factors in Radiation Resistance

Several growth factors have been found to be radioprotective, especially when given before irradiation. Among these are the cytokines IL1, granulocyte colony stimulating factor (G-CSF), and some members of the FGF family. Irradiation can also cause the release of cytokines. For example, irradiation of mononuclear phagocytes can cause release of platelet-derived growth factor (PDGF), tumor necrosis factor-alpha (TNF-a) and insulin-like growth factor-1 (IGF-I) (53), which may, in addition to...

Radiosensitization Of Human Tumors Expressing Activated Ras Oncogenes

Inhibition of H-Ras farnesylation in human tumor cells by FTI-277. Cells with mutated T24 and HS578T or wild-type H-Ras HeLa, HT-29, and SKBr-3 were treated with the indicated concentration pM ofFTI-277 for 24 h or with an equal volume of10 mM dithiothreitol DTT in DMSO carrier C, control . Cell lysates were then obtained for Western-blot analysis. Blots were probed with monoclonal antibody MAb to H-Ras. Arrows indicate migration of unfarnesylated H-Ras. Fig. 10. Inhibition of H-Ras...

Introduction

Over the last decade, the posttranslational processing pathway ofthe Ras oncoprotein has been elucidated and the enzyme that catalyzes the initial and critical step in this pathway, protein farnesyltransferase FTase , has been characterized 1-6 . These advances led to a great deal ofeffort, both in the pharmaceutical industry and in academia, focused on the discovery of selective FTase inhibitors FTIs . This chapter discusses two aspects of the FTI program at Schering-Plough Research Institute...