Recruitment of cell phospholipids and cholesterol by apolipoproteins A-II and A-I: formation of nascent apolipoprotein-specific HDL that differ in size, phospholipid composition, and reactivity with LCAT.

摘要: Studies were carried out to determine whether apolipoprotein (apo) A-II, like apoA-I, can recruit phospholipid and cholesterol from cell membranes, thereby forming nascent apoA-II-specific HDL. ApoA-II apoA-I purified plasma each was incubated with CHO cells at a concentration of 10 micrograms/ml. Lipid-containing complexes isolated the medium in both cases; composition apoA-II- apoA-I-specific similar where percent protein, phospholipid, 35 +/- 3, 38 2, 25 1 for apoA-II, respectively, 40 1, 24 2 respectively. On per mole basis, recruited significantly more than dimeric apoA-II suggesting that its greater number alpha helices binds lipid. By electron microscopy, particles predominantly discoidal morphology. unique their nondenaturing polyacrylamide gradient gel size distribution as six distinct populations diameters 8.1, 9.3, 10.4, 11.8, 13.1, 14.6 nm routinely noted, compared which formed only three major 7.3, 9.2, 11.0 nm. Nascent lecithin:cholesterol acyltransferase (LCAT) transformed into 8.4 particles. The latter is HDL3a, LpA-I particles, extracellularly assembled apoA-I-lipid directly give rise subpopulation upon interaction LCAT. Unlike apoA-II-lipid could not serve substrates LCAT did undergo transformation. This study also demonstrates, first time, show preference recruitment membranes. Although phosphatidylcholine removed by apolipoproteins, preferentially recruits phosphatidylethanolamine (PE) second most abundant while sphingomyelin. As PE usually associated inner leaflet membrane, it likely penetrate farther membrane extract PE. ability insert deeply lipid milieu may explain known resist dissociation mature HDL particle.