Abstract
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 cell-permeant should be useful tools to elucidate the effects of cathepsin B in the cytosol. We have covalently functionalised the poorly cell-permeant epoxysuccinyl-based cathepsin B inhibitor [R-Gly-Gly-Leu-(2S,3S)-tEps-Leu-Pro-OH; R=OMe] with the C-terminal heptapeptide segment of penetratin (R=epsilonAhx-Arg-Arg-Nle-Lys-Trp-Lys-Lys-NH2). 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 prodrug-like epoxysuccinyl peptides E64d and CA074Me.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Affinity Labels / chemical synthesis
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Affinity Labels / chemistry
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Amino Acid Sequence
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Carrier Proteins / chemistry
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Carrier Proteins / pharmacokinetics*
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Carrier Proteins / pharmacology
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Cathepsin B / antagonists & inhibitors*
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Cathepsin B / metabolism
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Cathepsin L
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Cathepsins / antagonists & inhibitors*
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Cell Membrane Permeability
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Cell-Penetrating Peptides
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Cysteine Endopeptidases
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Cysteine Proteinase Inhibitors / chemistry
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Cysteine Proteinase Inhibitors / pharmacokinetics*
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Cysteine Proteinase Inhibitors / pharmacology
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Humans
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Kinetics
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Mammary Neoplasms, Experimental / enzymology
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Molecular Sequence Data
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Oligopeptides / chemical synthesis
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Oligopeptides / pharmacokinetics*
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Oligopeptides / pharmacology
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Peptide Fragments / chemistry
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Peptide Fragments / pharmacokinetics
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Peptide Fragments / pharmacology
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Structure-Activity Relationship
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Tumor Cells, Cultured / drug effects
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Tumor Cells, Cultured / enzymology
Substances
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Affinity Labels
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Carrier Proteins
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Cell-Penetrating Peptides
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Cysteine Proteinase Inhibitors
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Oligopeptides
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Peptide Fragments
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penetratin
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Cathepsins
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Cysteine Endopeptidases
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Cathepsin B
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CTSL protein, human
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Cathepsin L