出版社：American Society for Biochemistry and Molecular Biology
摘要：It is generally thought that the large heterogeneity of humanHDL confers antiatherogenic properties; however, the mechanismsgoverning HDL biogenesis and speciation are complex and poorlyunderstood. Here, we show that incubation of exogenous apolipoproteinA-I (apoA-I) with fibroblasts, CaCo-2, or CHO-overexpressingABCA1 cells generates only -nascent apolipoprotein A-I-containingparticles (-LpA-I) with diameters of 8–20 nm, whereashuman umbilical vein endothelial cells and ABCA1 mutant (Q597R)cells were unable to form such particles. Interestingly, incubationof exogenous apoA-I with either HepG2 or macrophages generatesboth -LpA-I and preß1-LpA-I. Furthermore, glyburideinhibits almost completely the formation of -LpA-I but not preß1-LpA-I.Similarly, endogenously secreted HepG2 apoA-I was found to beassociated with both preß1-LpA-I and -LpA-I; by contrast,CaCo-2 cells secreted only -LpA-I. To determine whether -LpA-Igenerated by fibroblasts is a good substrate for LCAT, isolated-LpA-I as well as reconstituted HDL [r(HDL)] was reacted withLCAT. Although both particles had similar Vmax (8.4 vs. 8.2nmol cholesteryl ester/h/µg LCAT, respectively), the Kmvalue was increased 2-fold for -LpA-I compared with r(HDL) (1.2vs. 0.7 µM apoA-I).
These results demonstrate that 1) ABCA1 is required for theformation of -LpA-I but not preß1-LpA-I; and 2) -LpA-Iinteracts efficiently with LCAT. Thus, our study provides directevidence for a new link between specific cell lines and thespeciation of nascent HDL that occurs by both ABCA1-dependentand -independent pathways.Abbreviations: apoA-I, apolipoprotein A-I; CE, cholesteryl ester; HUVEC, human umbilical vein endothelial cells; LpA-I, nascent apolipoprotein A-I-containing particle; MWCO, molecular weight cut off; RCT, reverse cholesterol transport; r(HDL), reconstituted high density lipoprotein; TD, Tangier disease; 2D-PAGGE, two-dimensional polyacrylamide nondenaturing gradient gel electrophoresis; 22OH/9CRA, 22(R)-hydroxycholesterol and 9-cis-retinoic acid
Supplementary key words ATP binding cassette transporter A1 • high density lipoprotein • -nascent apolipoprotein A-I-containing particle • pre-ß1-nascent apolipoprotein A-I-containing particle
-nascent apolipoprotein A-I-containing particles (
