Abstract 12601: O-Glycosylation of ApoB100 is Associated With Enhanced Sphingomyelinase Activity and Atherogenicity of Human Electronegative LDL
Background: Among the 5 (L1-L5) chromatographically resolved subfractions of human LDL, L5 is the most electronegative and atherogenic. L5’s atherogenicity may be attributed in part to its high ceramide content. Because ceramides can be converted from sphingomyelins by sphingomyelinase (SMase), we examined whether L5 has SMase-like properties.
Methods and Results: The total lipid extract of L5 was as capable as L5 in inducing arterial endothelial cell (EC) apoptosis. LC/MSE analysis confirmed that L5 had a significantly greater ceramide content in the lipid extract than L1 (n=4; P<0.01). On Amplex Red SMase assays, L5 but not L1 exhibited a strong SMase-like activity (n=12). ECs treated with L5 increased intracellular ceramide concentrations; the associated cytotoxicity was significantly attenuated by SMase inhibitor desipramine. To identify the putative region of LDL with SMase activities, we compared human apolipoprotein B100 (apoB100) with Bacillus cereus, Leptospira interrogans, and Staphylococcus aureus SMases in amino acid sequences. The predicted catalytic site of human apoB-100 with activities similar to the bacterial SMases comprised N2035, E2079, F2081, N2084, E2140, N2251, D2253, D2312, and H2366 in the α2 region. Post-translational analysis with LC/MSE and ProteinLynx Global SERVER (PLGS) revealed exclusive O-glycosylation of the amino acid residues S1732, S1959, S2378, S2408 and S2429 in the α2 region.
Conclusions: The structural uniqueness of the α2 region of apoB-100 characterized by specific O-glycosylation may underlie L5’s atherogenicity through enhanced SMase activity and ceramide overproduction. Modifying this region may curtail L5’s atherogenicity.
Author Disclosures: L. Ke: None. H. Chan: None. C. Chen: None. J. Lu: None. G. Marathe: None. C. Chu: None. H. Chan: None. C. Wang: None. S. Law: None. Y. Tung: None. T.M. McIntyre: None. J. Yen: None. C. Chen: None.
- © 2015 by American Heart Association, Inc.