Metabolism of PLTP, CETP, and LCAT on multiple HDL sizes using the Orbitrap Fusion Lumos

Abstract

Recent in vivo tracer studies demonstrated that targeted mass spectrometry (MS) on the Q Exactive Orbitrap could determine the metabolism of HDL proteins 100s-fold less abundant than apolipoprotein A1 (APOA1). In this study, we demonstrate that the Orbitrap Lumos can measure tracer in proteins whose abundances are 1000s-fold less than APOA1, specifically the lipid transfer proteins phospholipid transfer protein (PLTP), cholesterol ester transfer protein (CETP), and lecithin-cholesterol acyl transferase (LCAT). Relative to the Q Exactive, the Lumos improved tracer detection by reducing tracer enrichment compression, thereby providing consistent enrichment data across multiple HDL sizes from 6 participants. We determined by compartmental modeling that PLTP is secreted in medium and large HDL (alpha2, alpha1, and alpha0) and is transferred from medium to larger sizes during circulation from where it is catabolized. CETP is secreted mainly in alpha1 and alpha2 and remains in these sizes during circulation. LCAT is secreted mainly in medium and small HDL (alpha2, alpha3, prebeta). Unlike PLTP and CETP, LCAT’s appearance on HDL is markedly delayed, indicating that LCAT may reside for a time outside of systemic circulation before attaching to HDL in plasma. The determination of these lipid transfer proteins’ unique metabolic structures was possible due to advances in MS technologies.

HDL proteome remodeling associates with COVID-19 severity

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Mapping the dynamic cell surface interactome of high-density lipoprotein reveals Aminopeptidase N as modulator of its endothelial uptake

“…It is possible that only the minority of the HDL-associated proteins directly interact with cellular counterparts, but it is more likely that current technology is not sensitive enough to capture all interactions. In view of the large range of abundances of HDL-associated proteins (25), it may well be that the number of accessible cell surface proteins versus the number of accessible HDL proteins did not allow us to reproducibly enriche a larger fraction of the HDL proteome at the cell surface. Moreover, it is important to note that the proteome of the HDL particles includes many cellular proteins.…”

Impact of High-Density Lipoproteins on Sepsis

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