Towards subunit-specific proteasome inhibitors: synthesis and evaluation of peptide alpha',beta'-epoxyketones.
BACKGROUND
The proteasome is a large multicatalytic protease complex (700 kDa) involved in a number of highly regulated processes. It has three major catalytic activities: a chymotrypsin-like activity, a trypsin-like activity and a post-glutamyl peptide hydrolyzing (PGPH) activity. To be useful as molecular probes, which could help dissect the cellular functions of the proteasome, inhibitors should be specific for the proteasome, active in vivo and selectively block only one of the three catalytic activities. To date, few inhibitors fulfill these requirements so we set out to make novel proteasome inhibitors that incorporate these characteristics.


RESULTS
A panel of amino-terminally acetylated peptide alpha',beta'-epoxyketones with leucine in P1 and various aliphatic or aromatic amino acids in P2-P4 were prepared and evaluated. Most compounds selectively inhibited the chymotrypsin-like activity, while only weakly inhibiting the trypsin-like and PGPH activities. After optimization, one inhibitor, Ac-hFLFL-epoxide, was found to be more potent and selective for the inhibition of the chymotrypsin-like activity than several previously described inhibitors. This inhibitor also exhibited strong in vivo anti-inflammatory activity.


CONCLUSIONS
Optimization of amino-terminally acetylated peptide alpha',beta'-epoxyketones furnished a potent proteasome inhibitor, Ac-hFLFL-epoxide, that has an excellent selectivity for the chymotrypsin-like activity. The inhibitor also proved to be a potent antiproliferative and anti-inflammatory agent. The strong in vivo and in vitro activities suggest that this class of proteasome inhibitors could be both molecular probes and therapeutic agents.
Elofsson
M
M
Departments of Molecular, Cellular and Developmental Biology, Organic Chemistry, Yale University, New Haven, CT 06520-8103, USA.
Splittgerber
U
U
Myung
J
J
Mohan
R
R
Crews
C M
CM
D000818:Animals; D001011:Aorta; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002918:Chymotrypsin / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000138:chemical synthesis* / Q000494:pharmacology; D015195:Drug Design; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects; D004852:Epoxy Compounds / Q000138:chemical synthesis* / Q000494:pharmacology; D005971:Glutamates; D007202:Indicators and Reagents; D007509:Irritants; D007700:Kinetics; D046911:Macromolecular Substances; D051379:Mice; D008968:Molecular Conformation; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000378:metabolism*; D010455:Peptides / Q000138:chemical synthesis* / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D014357:Trypsin / Q000378:metabolism
D015853:Cysteine Proteinase Inhibitors; D004852:Epoxy Compounds; D005971:Glutamates; D007202:Indicators and Reagents; D007509:Irritants; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D010455:Peptides; D002918:Chymotrypsin; D014357:Trypsin; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex