Summary
Apart from transporting lipids through the body, the human plasma lipoproteins very
low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) are also thought
to serve as a modality for intra-organismal protein transfer, shipping proteins with
important roles in inflammation and thrombosis from the site of synthesis to effector
locations. To better understand the role of VLDL and LDL in the transport of proteins,
we applied a combination of LTQ ORBITRAP-XL (nLC-MS/MS) with both in-SDS-PAGE gel
and in-solution tryptic digestion of pure and defined VLDL and LDL fractions. We identified
the presence of 95 VLDL-and 51 LDL-associated proteins including all known apolipoproteins
and lipid transport proteins, and intriguingly a set of coagulation proteins, complement
system and anti-microbial proteins. Prothrombin, protein S, fibrinogen γ, PLTP, CETP,
CD14 and LBP were present on VLDL but not on LDL. Prenylcysteine oxidase 1, dermcidin,
cathelicidin antimicrobial peptide, TFPI-1 and fibrinogen α chain were associated
with both VLDL and LDL. Apo A-V is only present on VLDL and not on LDL. Collectively,
this study provides a wealth of knowledge on the protein constituents of the human
plasma lipoprotein system and strongly supports the notion that protein shuttling
through this system is involved in the regulation of biological processes. Human diseases
related to proteins carried by VLDL and LDL can be divided in three major categories:
1 – dyslipidaemia, 2 – atherosclerosis and vascular disease, and 3 – coagulation disorders.
Keywords
Proteomics - nLC-MS/MS - coagulation - prothrombin - protein S - TFPI-1 - atherothrombosis
- LCAT - CETP - PLTP - apoAV - apolipoproteins - antimicrobial peptides - lysozyme
C - dermicidin - lipopolysaccharide binding protein - CD14 - prenylcysteine oxidase
- cathepcin D - nLC-MS/MS