Phospholipid transfer protein mediated conversion of high density lipoproteins generates pre beta 1-HDL.
High density lipoproteins (HDL) subclasses can be differentiated by two-dimensional non-denaturing polyacrylamide gradient gel electrophoresis (2D-PAGGE) and subsequent immunoblotting. The quantitatively minor HDL-subclasses pre beta 1-LpA-I and gamma-LpE are initial acceptors of cell-derived cholesterol into the plasma compartment. In this study we analysed the effect of phospholipid transfer protein (PLTP) on the electrophoretic distribution of HDL-subclasses in plasma as well as the ability of plasma, pre beta 1-LpA-I, and gamma-LpE to take up [3H]cholesterol from labeled fibroblasts. Pre beta 1-LpA-I but not gamma-LpE disappeared during a 16 hours incubation in the absence of PLTP. During a one minute incubation pre beta 1-LpA-I of pre-incubated plasma released 75% less [3H]cholesterol from radiolabeled fibroblasts than pre beta 1-LpA-I of control plasma. Pre-incubation of plasma reduced the uptake of [3H]cholesterol by gamma-LpE by 40%. Totally, the cholesterol efflux capacity of plasma decreased by 10% compared to the original sample. The amount of immunodetectable pre beta 1-LpA-I increased when plasma was incubated in the presence of PLTP while the amount of immunodetectable gamma-LpE did not change. After one minute incubation of PLTP-conditioned plasma with [3H]cholesterol-labeled fibroblasts, the amount of radioactive cholesterol taken up by pre beta 1-LpA-I was twice as high as in control plasma whereas the amount of [3H]cholesterol taken up by gamma-LpE remained unchanged. As a net result, treatment with PLTP increased the cholesterol efflux into total plasma by 40%. Together with results of previous studies our data suggest that the conversion of alpha-LpA-I3 into alpha-LpA-I2 by PLTP generates pre beta 1-LpA-I but not gamma-LpE. PLTP helps to enhance the uptake of cell-derived cholesterol by pre beta 1-LpA-I and, thereby, the cholesterol efflux capacity of normal plasma.
von Eckardstein
A
A
Institut für Klinische Chemie und Laboratoriumsmedizin, Westfälische Wilhelms-Universität Münster, Germany.
Jauhiainen
M
M
Huang
Y
Y
Metso
J
J
Langer
C
C
Pussinen
P
P
Wu
S
S
Ehnholm
C
C
Assmann
G
G
D016632:Apolipoprotein A-I / Q000378:metabolism; D001057:Apolipoproteins E / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D017270:Lipoprotein(a) / Q000031:analogs & derivatives / Q000378:metabolism; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D049294:Phospholipid Transfer Proteins; D013631:Tangier Disease / Q000378:metabolism
D016632:Apolipoprotein A-I; D001057:Apolipoproteins E; D002352:Carrier Proteins; D017270:Lipoprotein(a); D008075:Lipoproteins, HDL; D008565:Membrane Proteins; D049294:Phospholipid Transfer Proteins; C078260:lipoprotein A-I; D002784:Cholesterol