Identification of a domain that mediates association of platelet-activating factor acetylhydrolase with high density lipoprotein.
The plasma form of platelet-activating factor (PAF) acetylhydrolase (PAF-AH), also known as lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) inactivates potent lipid messengers such as PAF and modified phospholipids generated in settings of oxidant stress. In humans, PAF-AH circulates in blood in fully active form and associates with high and low density lipoproteins (HDL and LDL). Several studies suggest that the location of PAF-AH affects both the catalytic efficiency and the function of the enzyme in vivo. The distribution of PAF-AH among lipoproteins varies widely among mammals. Here, we report that mouse and human PAF-AHs associate with human HDL particles of different density. We made use of this observation in the development of a binding assay to identify domains required for association of human PAF-AH with human HDL. Sequence comparisons among species combined with domain-swapping and site-directed mutagenesis studies led us to the identification of C-terminal residues necessary for the association of human PAF-AH with human HDL. Interestingly, the region identified is not conserved among PAF-AHs, suggesting that PAF-AH interacts with HDL particles in a manner that is unique to each species. These findings contribute to our understanding of the mechanisms responsible for association of human PAF-AH with HDL and may facilitate future studies aimed at precisely determining the function of PAF-AH in each lipoprotein particle.
Gardner
Alison A
AA
Huntsman Cancer Institute and Department of Internal Medicine, University of Utah, Salt Lake City, Utah 84112, USA.
Reichert
Ethan C
EC
Topham
Matthew K
MK
Stafforini
Diana M
DM
D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D017124:Conserved Sequence; D006801:Humans; D008074:Lipoproteins / Q000737:chemistry; D008075:Lipoproteins, HDL / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D008074:Lipoproteins; D008075:Lipoproteins, HDL; D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase