Table 1.
List of major components of the HDL proteome
| Proteins | Function |
| Apolipoproteins | |
| A-I | Major apolipoprotein of HDL; activates LCAT |
| A-II | Enhances hepatic triglyceride lipase activity |
| A-IV | Participates in reverse cholesterol transport; probably involved in the activation of LCAT and LPL |
| C-I | Activates LCAT; modulates CETP activity; inhibits hepatic lipase |
| C-II | Activator of LPL |
| C-III | Inhibitor of LPL and hepatic lipase |
| C-IV | Involved in triglyceride metabolism |
| D | Associated with LCAT |
| E | Ligand for several members of the LDL receptor gene family (especially LDL-R and LRP) |
| F | Also known as lipid transfer inhibitor protein (LTIP); inhibits CETP |
| H | Also known as β-2-glycoprotein 1; regulates platelet aggregation |
| J | Also called clusterin; binds hydrophobic molecules, interacts with cell receptors |
| L-1 | Trypanolytic factor of human serum |
| M | Binding of small hydrophobic molecules |
| Enzymes | |
| LCAT | Esterification of cholesterol to cholesteryl esters |
| PON1 | Paraoxonase 1: hydrolysis of homocysteine thiolactone; hydrolyses a wide variety of substrates |
| PAF-AH (LpPLA2) | Lipoprotein-associated phospholipase A2: hydrolysis of short-chain oxidized phospholipids |
| GSPx-3 | Plasma glutathione selenoperoxidase 3: reduction of hydroperoxides by glutathione |
| Lipid transfer proteins | |
| PLTP | Phospholipid transfer protein: conversion of HDL into larger and smaller particles, transport of LPS; positive acute-phase reactant |
| CETP | Shuttles cholesteryl esters and triglycerides between HDL and apoB-containing lipoproteins. |
| Acute-phase proteins | |
| SAA | Serum amyloid A; acute-phase protein |
| LBP | LPS binding protein; binds phospholipids, thereby acting as a lipid exchange protein similar to CETP and PLTP |
| α-1 acid glycoprotein 2 | Also called orosomucoid-2; negative acute-phase reactant |
| α-2 HS glycoprotein | Also called fetuin-A; promotes endocytosis; possesses opsonic properties |
| Fibrinogen α-chain | Precursor of fibrin, cofactor in platelet aggregation |
| Complement components | |
| C3 | Complement activator through both classic and alternative activation pathways |
| C4 | Activation of the classic pathway of the complement system |
| C4b-binding protein | Controls the classic pathway. |
| C9 | Pore-forming subunit of the membrane attack complex |
| Vitronectin | Inhibitor of the membrane-damaging effect of the terminal cytolytic pathway |
| Proteinase inhibitors | |
| α-1 antitrypsin | Inhibitor of serine proteinases |
| α-2 antiplasmin | Inhibits plasmin and trypsin and inactivates chymotrypsin |
| Haptoglobin-related protein | Decoy substrate to prevent proteolysis |
| Other proteins | |
| Retinol-binding protein | Delivers retinol from liver to peripheral tissues |
| Transthyretin | Carries the thyroid hormone thyroxine (T4) and retinol-binding protein bound to retinol |
| Serotransferrin | Iron transport glycoprotein |
| Vitamin D-binding protein | Vitamin D binding and transport |
| α-1B glycoprotein | Function unknown |
| Hemopexin | Iron binding protein |
This list is incomplete because only the proteins detected and confirmed by other studies are provided, according to Kontush et al. and Shal et al.159,160 LCAT, lecithin–cholesterol acyltransferase; LPL, lipoprotein lipase; LDL-R, LDL-receptor; LRP, lipoprotein receptor-related protein. Modified from reference 159, with permission.