Targeted Measurements of O- and N-Glycopeptides Show That Proteins in High Density Lipoprotein Particles Are Enriched with Specific Glycosylation Compared to Plasma

Abstract

High density lipoprotein (HDL) particles are believed to be protective due to their inverse correlation with the prevalence of cardiovascular diseases. However, recent studies show that in some conditions such as heart disease and diabetes, HDL particles can become dysfunctional. Great attention has been directed toward HDL particle composition because the relative abundances of HDL constituents determine HDL's functional properties. A key factor to consider when studying the structure and composition of plasma particles is the protein glycosylation. Here, we profile the O- and N-linked glycosylation of HDL associated-proteins including the truncated form of Apo CIII and their glycan heterogeneity in a site-specific manner. Apolipoprotein CIII, fetuin A, and alpha 1 antitrypsin are glycoproteins associated with lipoproteins and are implicated in many cardiovascular and other disease conditions. A targeted method (UHPLC-QQQ) was used to measure the glycoprotein concentrations and site-specific glycovariations of the proteins in human plasma and compared with HDL particles isolated from the same plasma samples. The proteins found in the plasma are differentially glycosylated compared to those isolated in HDL. The results of this study suggest that glycosylation may play a role in protein partitioning in the blood, with possible functional implications.

Site-Specific Glycoprofiles of HDL-Associated ApoE are Correlated with HDL Functional Capacity and Unaffected by Short-Term Diet

“…ApoE was added to the existing MRM site-specific glycosylation method described previously. 10 The two most abundant ApoC-III glycans, ApoC3_74_O_1102 and ApoC3_74_O_2230, were differentially affected by diet. The disialylated glycopeptide ApoC3_74_O_1102 decreased after FF and increased after Med whereas the non-sialylated glycopeptide ApoC3_74_O_2230 increased after FF and decreased after Med (unadjusted p = 0.001 and 0.021 respectively, Figure 1-E&F).…”

Glycosylation of human plasma lipoproteins reveals a high level of diversity, which directly impacts their functional properties

“…Given that ABCA1 preferentially effluxes cholesterol to small relative to large HDL [59], such effect should have resulted in the elevated cholesterol efflux capacity of the desialylated particles, which was not the case, suggesting that other factors, including HDL charge, were more important for this functional alteration. We interpret these data to hypothesise that the N-glycome of HDL proteins, including fetuin A, alpha-1-antitripsin, angiotensinogen [26,28,29], LCAT [24] and possibly apoA-I [57,58], can be affected by neuroaminidaseinduced desialylation and that these modifications bear a potential to reduce electronegativity and LCAT activity of HDL to concomitantly contribute to the diminished capacity of HDL to efflux cellular cholesterol via ABCA1, counteracting potentially beneficial effects of the diminished HDL size.…”

“…Remarkably, carbohydrate residues are specifically associated with distinct HDL proteins, such as apo C-III which contains O-linked glycans [29].…”

“…As N-and O-glycosylation of human apoA-I was recently reported [57,58], desialylation might equally alter interactions of apoA-I with cellular proteins, including ABCA1. The question of apoA-I glycosylation remains controversial though as apoA-I-associated glycans were not detected in several studies employing LC/MS/MS [26,28,29].…”

Global and site‐specific analysis of protein glycosylation in complex biological systems with Mass Spectrometry

“…Due to the importance of protein glycosylation in biological systems, glycoproteomics has been extensively applied to disease-related research (Whelan et al, 2009;Hwang et al, 2010;Song et al, 2014;Reiding et al, 2017;Yang et al, 2017b;Kailemia et al, 2018), such as hepatitis, cancer (Dai et al, 2011;Liu et al, 2014;Kailemia et al, 2017;Miyamoto et al, 2018;Veillon et al, 2018), and infectious diseases (Vigerust, 2011;Go et al, 2017). Glycosylation can change chemical and physical properties of proteins, and regulate their binding and interactions with ligands or extracellular matrix.…”