Effect of lecithin:cholesterol acyltransferase on distribution of apolipoprotein A-IV among lipoproteins of human plasma.
Effect of lecithin:cholesterol acyltransferase on distribution of apolipoprotein A-IV among lipoproteins of human plasma.
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发表时间：
1987-06
影响因子：
6.5
通讯作者：
C. Bisgaier;O. Sachdev;E. S. Lee;K. Williams;C. Blum;R. Glickman
中科院分区：
文献类型：
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作者：
C. Bisgaier;O. Sachdev;E. S. Lee;K. Williams;C. Blum;R. Glickman
研究了胆固醇酯化对人血浆中apoA-IV分布的影响。在存在或不存在卵磷脂：胆固醇酰基转移酶（LCAT）抑制剂5，5-二硫代双（2-硝基苯甲酸）（DTNB）的情况下孵育人血浆，并立即通过6%琼脂糖柱色谱法进行分级。通过放射免疫测定法（RIA）监测组分的apoA-IV、apoE和apoA-I。孵育导致胆固醇酯的血浆浓度升高和apoA-IV的分布改变。孵育后，apoA-IV洗脱在含有小VLDL颗粒、LDL和HDL 2的通常apoA-IV贫乏的血浆部分中。包括DTNB在孵育过程中导致HDL的一些扩大，然而，胆固醇酯化和脂蛋白结合的载脂蛋白A-IV被抑制。在孵育后和凝胶过滤前向血浆中加入DTNB对脂蛋白立即分级分离时的apoA-IV分布没有影响。空腹血浆apoE分布在两个或三个峰中;在一些血浆中，有一个小峰与柱空体积洗脱，在所有血浆中，有较大的峰与VLDL-LDL区域和HDL 2洗脱。孵育导致HDL apoE置换为更大的脂蛋白，并且在存在或不存在DTNB的情况下观察到这种效应。ApoA-I分布在HDL区域洗脱的单一宽峰中，并且凝胶过滤分布不受DTNB存在或不存在下孵育的影响。将预先加热至56 ℃的血浆孵育至无LCAT，不会导致apoA-IV额外移动至脂蛋白上，除非孵育期间存在纯化的LCAT。加入热灭活的LCAT对apoA-IV的运动没有影响。这些数据表明，人载脂蛋白A-IV从脂蛋白的自由馏分的脂蛋白颗粒的再分布似乎是依赖于LCAT的行动。当LCAT作用时，负责apoA-IV与脂蛋白表面结合增加的机制可能涉及由于表面底物的消耗和核心的额外扩大而在脂蛋白表面产生"间隙"。ApoA-IV可以结合到这些"间隙"，其中磷脂头部基团的堆积密度降低。
The effect of cholesterol esterification on the distribution of apoA-IV in human plasma was investigated. Human plasma was incubated in the presence or absence of the lecithin:cholesterol acyltransferase (LCAT) inhibitor 5,5-dithiobis(2-nitrobenzoic acid) (DTNB) and immediately fractionated by 6% agarose column chromatography. Fractions were monitored for apoA-IV, apoE, and apoA-I by radioimmunoassay (RIA). Incubation resulted in an elevated plasma concentration of cholesteryl ester and in an altered distribution of apoA-IV. After incubation apoA-IV eluted in the ordinarily apoA-IV-poor fractions of plasma that contain small VLDL particles, LDL, and HDL2. Inclusion of DTNB during the incubation resulted in some enlargement of HDL; however, both cholesterol esterification and lipoprotein binding of apoA-IV were inhibited. Addition of DTNB to plasma after incubation and prior to gel filtration had no effect on the apoA-IV distribution when the lipoproteins were immediately fractionated. Fasting plasma apoE was distributed in two or three peaks; in some plasmas there was a small peak that eluted with the column void volume, and, in all plasmas, there were larger peaks that eluted with the VLDL-LDL region and HDL2. Incubation resulted in displacement of HDL apoE to larger lipoproteins and this effect was observed in the presence or absence of DTNB. ApoA-I was distributed in a single broad peak that eluted in the region of HDL and the gel-filtered distribution was unaffected by incubation either in the presence or absence of DTNB. Incubation of plasma that was previously heated to 56 degrees C to inactivate LCAT resulted in no additional movement of apoA-IV onto lipoproteins, unless purified LCAT was present during incubation. The addition of heat-inactivated LCAT to the incubation, had no effect on movement of apoA-IV. These data suggest that human apoA-IV redistribution from the lipoprotein-free fraction to lipoprotein particles appears to be dependent on LCAT action. The mechanism responsible for the increased binding of apoA-IV to the surface of lipoproteins when LCAT acts may involve the generation of "gaps" in the lipoprotein surface due to the consumption of substrate from the surface and additional enlargement of the core. ApoA-IV may bind to these "gaps," where the packing density of the phospholipid head groups is reduced.