Submitted on January 27, 2006
Revised on March 3, 2006
Accepted on March 6, 2006
Active plasma phospholipid transfer protein is associated withApo AI- but not Apo E-containing lipoproteins
Marian C. Cheung and John J. Albers
Medicine Dept., University of Washington, Seattle, WA 98109-4517
Corresponding Author: mccheung{at}u.washington.edu
ABSTRACT Plasma phospholipid transfer protein (PLTP) is a multifaceted protein with diverse biological functions. It has been shown to exist in both active and inactive forms. To determine the nature of lipoproteins associated with active PLTP, plasma samples were adsorbed with anti-A-I, anti-A-II, or anti-E immnuoadsorbent, and PLTP activity was measured in the resulting plasma devoid of apo A-I, apo A-II, or apo E. Anti-A-I and anti-A-II immunoadsorbents removed 98+/-1% (n=8) and 38+/-25% (n=7) of plasma PLTP activity, respectively. In contrast, only 1+/-5% of plasma PLTP activity was removed by anti-E immunoadsorbents (n=7). Dextran sulfate (DS) cellulose did not bind apo A-I but it removed 83+/-5% (n=4) of the PLTP activity in plasma. In size exclusion chromatography, PLTP activity removed by anti-A-I or anti-A-II immunoadsorbent was associated primarily with particles in size region corresponding to HDL whereas a substantial portion of the PLTP activity dissociated from DS cellulose was found in particles larger and smaller than HDL. These data show that: (1) Active plasma PLTP is associated primarily with apo A-I- but not apo E-containing lipoproteins. (2) Active PLTP is present in HDL particles with and without apo A-II, and its distribution between these two HDL subpopulations varies widely among individuals. (3) Dextran sulfate cellulose can remove active PLTP from apo A-I-containing lipoproteins, and this process creates new active PLTP-containing particles in vitro.
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