Biogenesis and speciation of nascent apoA-I-containing particles in various cell lines (original) (raw)

2005, The Journal of Lipid Research

It is generally thought that the large heterogeneity of human HDL confers antiatherogenic properties; however, the mechanisms governing HDL biogenesis and speciation are complex and poorly understood. Here, we show that incubation of exogenous apolipoprotein A-I (apoA-I) with fibroblasts, CaCo-2, or CHO-overexpressing ABCA1 cells generates only ␣ -nascent apolipoprotein A-I-containing particles ( ␣ -LpA-I) with diameters of 8-20 nm, whereas human umbilical vein endothelial cells and ABCA1 mutant (Q597R) cells were unable to form such particles. Interestingly, incubation of exogenous apoA-I with either HepG2 or macrophages generates both ␣ -LpA-I and pre ␤ 1 -LpA-I. Furthermore, glyburide inhibits almost completely the formation of ␣ -LpA-I but not pre ␤ 1 -LpA-I. Similarly, endogenously secreted HepG2 apoA-I was found to be associated with both pre ␤ 1 -LpA-I and ␣ -LpA-I; by contrast, CaCo-2 cells secreted only ␣ -LpA-I. To determine whether ␣ -LpA-I generated by fibroblasts is a good substrate for LCAT, isolated ␣ -LpA-I as well as reconstituted HDL [r(HDL)] was reacted with LCAT. Although both particles had similar V max (8.4 vs. 8.2 nmol cholesteryl ester/h/ g LCAT, respectively), the K m value was increased 2-fold for ␣ -LpA-I compared with r(HDL) (1.2 vs. 0.7 M apoA-I). These results demonstrate that 1 ) ABCA1 is required for the formation of ␣ -LpA-I but not pre ␤ 1 -LpA-I; and 2 ) ␣ -LpA-I interacts efficiently with LCAT. Thus, our study provides direct evidence for a new link between specific cell lines and the speciation of nascent HDL that occurs by both ABCA1-dependent and -independent pathways. -Krimbou, L., H. Hajj Hassan, S. Blain, S. Rashid, M. Denis, M. Marcil, and J. Genest. Biogenesis and speciation of nascent apoA-I-containing particles in various cell lines. J. Lipid Res. 2005. 46: 1668-1677.