Shotgun proteomics implicates protease inhibition and complement activation in the antiinflammatory properties of HDL
Tomas Vaisar, … , John F. Oram, Jay W. Heinecke
Tomas Vaisar, … , John F. Oram, Jay W. Heinecke
Published March 1, 2007
Citation Information: J Clin Invest. 2007;117(3):746-756. https://doi.org/10.1172/JCI26206.
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Research Article

Shotgun proteomics implicates protease inhibition and complement activation in the antiinflammatory properties of HDL

Abstract

HDL lowers the risk for atherosclerotic cardiovascular disease by promoting cholesterol efflux from macrophage foam cells. However, other antiatherosclerotic properties of HDL are poorly understood. To test the hypothesis that the lipoprotein carries proteins that might have novel cardioprotective activities, we used shotgun proteomics to investigate the composition of HDL isolated from healthy subjects and subjects with coronary artery disease (CAD). Unexpectedly, our analytical strategy identified multiple complement-regulatory proteins and a diverse array of distinct serpins with serine-type endopeptidase inhibitor activity. Many acute-phase response proteins were also detected, supporting the proposal that HDL is of central importance in inflammation. Mass spectrometry and biochemical analyses demonstrated that HDL3 from subjects with CAD was selectively enriched in apoE, raising the possibility that HDL carries a unique cargo of proteins in humans with clinically significant cardiovascular disease. Collectively, our observations suggest that HDL plays previously unsuspected roles in regulating the complement system and protecting tissue from proteolysis and that the protein cargo of HDL contributes to its antiinflammatory and antiatherogenic properties.

Authors

Tomas Vaisar, Subramaniam Pennathur, Pattie S. Green, Sina A. Gharib, Andrew N. Hoofnagle, Marian C. Cheung, Jaeman Byun, Simona Vuletic, Sean Kassim, Pragya Singh, Helen Chea, Robert H. Knopp, John Brunzell, Randolph Geary, Alan Chait, Xue-Qiao Zhao, Keith Elkon, Santica Marcovina, Paul Ridker, John F. Oram, Jay W. Heinecke

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Figure 7

Relationship between unique peptides and protein concentration in HDL and HDL3.

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Relationship between unique peptides and protein concentration in HDL an...
The total number of unique peptides detected by MS in HDL and HDL3 is as shown in Table 2. The protein concentrations of apoA-I (98 mg/dl), apoA-II (42 mg/dl), apoC-II (4.6 mg/dl), apoB (1.7 mg/dl), and transferrin (0.02 mg/dl) in HDL3 and HDL isolated by ultracentrifugation are those reported by McPherson et al. (where HDL equals the sum of HDL2 and HDL3; ref. 41). The concentration of CETP in HDL3 (0.1 mg/dl) was estimated as 50% that of plasma CETP (40). Linear regression analysis revealed a strong correlation (r2 = 0.98 and 0.88) between protein concentration and unique peptides in HDL and HDL3, respectively.