Epoxomicin, a potent and selective proteasome inhibitor, exhibitsin vivoantiinflammatory activity

• DOI: 10.1073/pnas.96.18.10403
• Publication Date: 2002-07-26T14:32:33Z
• Authors: Lihao Meng; Royce Mohan; Benjamin H. B. Kwok; Mikael Elofsson; Ny Sin; Craig M. Crews
• Keywords: Proteasome Endopeptidase Complex; Umbilical Veins; 0303 health sciences; Antibiotics, Antineoplastic; Erythrocytes; Anti-Inflammatory Agents, Non-Steroidal; Cysteine Proteinase Inhibitors; 3. Good health; Cysteine Endopeptidases; Kinetics; 03 medical and health sciences; Multienzyme Complexes; Tumor Cells, Cultured; Animals; Humans; Cattle; Endothelium, Vascular; Tumor Suppressor Protein p53; Oligopeptides; Ubiquitins; Cells, Cultured; HeLa Cells

The proteasome regulates cellular processes as diverse as cell cycle progression and NF-κB activation. In this study, we show that the potent antitumor natural product epoxomicin specifically targets the proteasome. Utilizing biotinylated-epoxomicin as a molecular probe, we demonstrate that epoxomicin covalently binds to the LMP7, X, MECL1, and Z catalytic subunits of the proteasome. Enzymatic analyses with purified bovine erythrocyte proteasome reveal that epoxomicin potently inhibits primarily the chymotrypsin-like activity. The trypsin-like and peptidyl-glutamyl peptide hydrolyzing catalytic activities also are inhibited at 100- and 1,000-fold slower rates, respectively. In contrast to peptide aldehyde proteasome inhibitors, epoxomicin does not inhibit nonproteasomal proteases such trypsin, chymotrypsin, papain, calpain, and cathepsin B at concentrations of up to 50 μM. In addition, epoxomicin is a more potent inhibitor of the chymotrypsin-like activity than lactacystin and the peptide vinyl sulfone NLVS. Epoxomicin also effectively inhibits NF-κB activation in vitro and potently blocksin vivoinflammation in the murine ear edema assay. These results thus define epoxomicin as a novel proteasome inhibitor that likely will prove useful in exploring the role of the proteasome in variousin vivoandin vitrosystems.