Hydroxynonenal inactivates cathepsin B by forming Michael adducts with active site residues.
Oxidation of plasma low-density lipoprotein (oxLDL) generates the lipid peroxidation product 4-hydroxy-2 nonenal (HNE) and also reduces proteolytic degradation of oxLDL and other proteins internalized by mouse peritoneal macrophages in culture. This leads to accumulation of undegraded material in lysosomes and formation of ceroid, a component of foam cells in atherosclerotic lesions. To explore the possibility that HNE contributes directly to the inactivation of proteases, structure-function studies of the lysosomal protease cathepsin B have been pursued. We found that treatment of mouse macrophages with HNE reduces degradation of internalized maleyl bovine serine albumin and cathepsin B activity. Purified bovine cathepsin B treated briefly with 15 microM HNE lost approximately 76% of its protease activity and also developed immunoreactivity with antibodies to HNE adducts in Western blot analysis. After stabilization of the potential Michael adducts by sodium borohydride reduction, modified amino acids were localized within the bovine cathepsin B protein structure by mass spectrometric analysis of tryptic peptides. Michael adducts were identified by tandem mass spectrometry at cathepsin B active site residues Cys 29 (mature A chain) and His 150 (mature B chain). Thus, covalent interaction between HNE and critical active site residues inactivates cathepsin B. These results support the hypothesis that the accumulation of undegraded macromolecules in lysosomes after oxidative damage are caused in part by direct protease inactivation by adduct formation with lipid peroxidation products such as HNE.
Crabb
John W
JW
Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA. crabbj@ccf.org
O'Neil
June
J
Miyagi
Masaru
M
West
Karen
K
Hoff
Henry F
HF
D000447:Aldehydes / Q000494:pharmacology*; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002401:Cathepsin B / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D002417:Cattle; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D008401:Gas Chromatography-Mass Spectrometry; D015227:Lipid Peroxidation; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D051379:Mice; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011487:Protein Conformation; D013154:Spleen / Q000187:drug effects* / Q000201:enzymology
D000447:Aldehydes; D000596:Amino Acids; D015853:Cysteine Proteinase Inhibitors; D002401:Cathepsin B; C027576:4-hydroxy-2-nonenal