Besides its physiological role in lysosomal protein breakdown, extralysosomal cathepsin B has recently been implicated in apoptotic cell death. Highly specific irreversible cathepsin B inhibitors that are readily cellpermeant should be useful tools to elucidate the effects of cathepsin B in the cytosol. We have covalently functionalised the poorly cellpermeant epoxysuccinyl based cathepsin B inhibitor [RGlyGlyLeu(2S, 3S)tEpsLeuProOH; R=OMe] with the Cterminal heptapeptide segment of penetratin (R=AhxArg ArgNleLysTrpLysLysNH2). The high inhibitory potency and selectivity for cathepsin B versus cathepsin L of the parent compound was not affected by the conjugation with the penetratin heptapeptide. The conjugate was shown to efficiently penetrate into MCF-7 cells as an active inhibitor, thereby circumventing an intracellular activation step that is required by other inhibitors, such as the prodruglike epoxysuccinyl peptides E64d and CA074Me.
Print ISSN: 1431-6730
Volume: 383, 05/2002
Pages: 849 - 852