Enlarging the scope of cell-penetrating prenylated peptides to include farnesylated 'CAAX' box sequences and diverse cell types

Protein prenylation is a posttranslational modification that is present in a large number of proteins; it has been proposed to be responsible for membrane association and protein-protein interactions, which contribute to its role in signal transduction pathways. Research has been aimed at inhibiting prenylation with farnesyltransferase inhibitors based on the finding that the farnesylated protein Ras is implicated in 30% of human cancers. Despite numerous studies on the enzymology of prenylation in vitro, many questions remain about the process of prenylation as it occurs in living cells. Here we describe the preparation of a series of farnesylated peptides that contain sequences recognized by protein farnesyltransferase. Using a combination of flow cytometry and confocal microscopy, we show that these peptides enter a variety of different cell types. A related peptide where the farnesyl group has been replaced by a disulfide-linked decyl group is also shown to be able to efficiently enter cells. These results highlight the applicability of these peptides as a platform for further study of protein prenylation and subsequent processing in live cells.