Myeloperoxidase impairs ABCA1-dependent cholesterol efflux through methionine oxidation and site-specific tyrosine chlorination of apolipoprotein A-I.
High density lipoprotein (HDL) isolated from human atherosclerotic lesions and the blood of patients with established coronary artery disease contains elevated levels of 3-chlorotyrosine. Myeloperoxidase (MPO) is the only known source of 3-chlorotyrosine in vivo, indicating that MPO oxidizes HDL in humans. We previously reported that Tyr-192 is the major site that is chlorinated in apolipoprotein A-I (apoA-I), the chief protein in HDL, and that chlorinated apoA-I loses its ability to promote cholesterol efflux from cells by the ATP-binding cassette transporter A1 (ABCA1) pathway. However, the pathways that promote the chlorination of specific Tyr residues in apoA-I are controversial, and the mechanism for MPO-mediated loss of ABCA1-dependent cholesterol efflux of apoA-I is unclear. Using site-directed mutagenesis, we now demonstrate that lysine residues direct tyrosine chlorination in apoA-I. Importantly, methionine residues inhibit chlorination, indicating that they can act as local, protein-bound antioxidants. Moreover, we observed near normal cholesterol efflux activity when Tyr-192 of apoA-I was mutated to Phe and the oxidized protein was incubated with methionine sulfoxide reductase. Thus, a combination of Tyr-192 chlorination and methionine oxidation is necessary for depriving apoA-I of its ABCA1-dependent cholesterol transport activity. Our observations suggest that biologically significant oxidative damage of apoA-I involves modification of a limited number of specific amino acids, raising the feasibility of producing oxidation-resistant forms of apoA-I that have enhanced anti-atherogenic activity in vivo.
Department of Medicine, University of Washington, Seattle, Washington 98195, USA.
Baohai
B
Shao
Michael N
MN
Oda
Constanze
C
Bergt
Xiaoyun
X
Fu
Pattie S
PS
Green
Nathan
N
Brot
John F
JF
Oram
Jay W
JW
Heinecke
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D016632:Apolipoprotein A-I / Q000378:metabolism*; D050197:Atherosclerosis / Q000503:physiopathology; D008076:Cholesterol, HDL / Q000378:metabolism*; D005487:Foam Cells; D006801:Humans; D008239:Lysine / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D051150:Methionine Sulfoxide Reductases; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism*; D011485:Protein Binding; D014443:Tyrosine / Q000378:metabolism
C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D008076:Cholesterol, HDL; D014443:Tyrosine; D008715:Methionine; D010088:Oxidoreductases; D009195:Peroxidase; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase; D008239:Lysine