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Peptidomimetic inhibitors of Ras farnesylation and function in whole cells
A M Garcia1, C Rowell, K Ackermann
1Eisai Research Institute, Andover, Massachusetts 01810.
Abstract:
The ras protooncogene is involved in regulation of cell growth. Mutations that activate the protein result in uncontrolled cell growth. Ras undergoes a series of posttranslational processing events, the first of which, farnesylation, is crucial for the function of the protein. Inhibitors of the farnesyltransferase enzyme are therefore potential candidates for the development of anticancer drugs. Tetrapeptides have been reported to be good inhibitors of this enzyme in vitro. We have synthesized analogs of the tetrapeptide Cys-Val-Phe-Met by replacement of the amino-terminal amide bonds. One inhibitor, B581, is permeable to the cell membrane. In the cell, it inhibits processing of two farnesylated proteins, H-ras and lamin A, but it does not inhibit processing of a geranylgeranylated protein, Rap 1A. Microinjection of B581 into frog oocytes inhibits maturation induced by activated, farnesylated H-ras but not maturation induced by activated, geranylgeranylated H-ras or by progesterone. These results demonstrate that this peptide mimic inhibits farnesylation selectively in the cell. The inhibition of farnesylation results in inhibition of H-ras function.
Insights
A novel peptide inhibitor, B581, selectively blocks farnesylation, a key step in ras protein processing. This targeted inhibition of farnesyltransferase offers potential for developing new anticancer drugs by controlling cell growth.
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- The ras protooncogene regulates cell growth; mutations lead to uncontrolled proliferation.
- Ras protein function is dependent on posttranslational modification, specifically farnesylation.
- Farnesyltransferase inhibitors are investigated as potential anticancer therapeutics.
Purpose of the Study:
- To synthesize and evaluate novel tetrapeptide analogs as inhibitors of farnesyltransferase.
- To assess the cellular permeability and selectivity of synthesized inhibitors.
- To investigate the effect of a specific inhibitor on H-ras function and cell maturation.
Main Methods:
- Synthesis of tetrapeptide analogs (Cys-Val-Phe-Met) with modified amino-terminal amide bonds.
- Cellular assays to evaluate inhibition of protein processing (H-ras, lamin A, Rap 1A).
- Microinjection into frog oocytes to assess inhibition of maturation induced by different signaling pathways.
Main Results:
- The synthesized inhibitor B581 is cell-permeable and selectively inhibits farnesylation of H-ras and lamin A, but not geranylgeranylation of Rap 1A.
- B581 inhibits maturation induced by activated, farnesylated H-ras in frog oocytes.
- Inhibition is specific to farnesylation, as maturation induced by geranylgeranylated H-ras or progesterone is unaffected.
Conclusions:
- The peptide mimic B581 selectively inhibits farnesylation within the cell.
- Inhibition of farnesylation by B581 effectively blocks H-ras protein function.
- This study validates farnesyltransferase inhibition as a viable strategy for anticancer drug development.