Identification of a novel family of oxidized phospholipids that serve as ligands for the macrophage scavenger receptor CD36.
The macrophage scavenger receptor CD36 plays an important role in the uptake of oxidized forms of low density lipoprotein (LDL) and contributes to lesion development in murine models of atherosclerosis. However, the structural basis of CD36 lipoprotein ligand recognition is unknown. We now identify a novel class of oxidized phospholipids that serve as high affinity ligands for CD36 and mediate recognition of oxidized forms of LDL by CD36 on macrophages. Small unilamellar vesicles of homogeneous phosphatidylcholine (PC) molecular species were oxidized by the myeloperoxidase (MPO)-H(2)O(2)-NO(2)(-) system, and products were separated by sequential LC/ESI/MS/MS. In parallel, fractions were tested for their ability to bind to CD36. Four major structurally related phospholipids with CD36 binding activity were identified from oxidized 1-palmitoyl-2-arachidonyl-PC, and four corresponding structural analogs with CD36 binding activity were identified from oxidized 1-palmitoyl-2-linoleoyl-PC. Each was then synthetically prepared, its structure confirmed by multinuclear NMR and high resolution mass spectrometry, and shown to possess identical CD36 binding activity and LC/ESI/MS/MS characteristics in both native and derivatized forms. Based upon the structures of the active compounds identified, and structure-function studies with a variety of synthetic analogs, we conclude that the structural characteristics required for high affinity binding of oxidized PC species to CD36 are a phospholipid with an sn-2 acyl group that incorporates a terminal gamma-hydroxy(or oxo)-alpha,beta-unsaturated carbonyl (oxPC(CD36)). LC/ESI/MS/MS studies demonstrate that oxPC(CD36) are formed during LDL oxidation by multiple distinct pathways. Formation of this novel class of oxidized PC species contributes to CD36-mediated recognition of LDL oxidized by MPO and other biologically relevant mechanisms. The present results offer structural insights into the molecular patterns recognized by the scavenger receptor CD36 and provide a platform for the development of potential therapeutic inhibitory agents.
Podrez
Eugene A
EA
Department of Cell Biology, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Poliakov
Eugenia
E
Shen
Zhongzhou
Z
Zhang
Renliang
R
Deng
Yijun
Y
Sun
Mingjiang
M
Finton
Paula J
PJ
Shan
Lian
L
Gugiu
Bogdan
B
Fox
Paul L
PL
Hoff
Henry F
HF
Salomon
Robert G
RG
Hazen
Stanley L
SL
D000818:Animals; D018955:CD36 Antigens / Q000378:metabolism*; D016466:CHO Cells; D008078:Cholesterol, LDL / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D022162:Cytoplasmic Vesicles / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008264:Macrophages / Q000378:metabolism*; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D015394:Molecular Structure; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism; D010743:Phospholipids / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011971:Receptors, Immunologic / Q000378:metabolism*; D051116:Receptors, Scavenger
D018955:CD36 Antigens; D008078:Cholesterol, LDL; D008024:Ligands; D010743:Phospholipids; D011971:Receptors, Immunologic; D051116:Receptors, Scavenger; D009195:Peroxidase