The mechanism of human plasma phospholipid transfer protein-induced enlargement of high-density lipoprotein particles: Evidence for particle fusion
The mechanism of human plasma phospholipid transfer protein-induced enlargement of high-density lipoprotein particles: Evidence for particle fusion
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DOI：
10.1042/bj3130275
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发表时间：
1996-01-01
影响因子：
4.1
通讯作者：
Ehnholm, C
中科院分区：
文献类型：
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作者：
Lusa, S;Jauhiainen, M;Ehnholm, C
1.磷脂转移蛋白（PLTP）介导高密度脂蛋白（HDL（3））转化为大颗粒，同时释放载脂蛋白A-I（apoA-I）。为了研究这种转化中涉及的机制，制备了在其核心中含有荧光芘酰胆固醇酯（PyrCE）（PyrCE-rHDL）或在其表面脂质层中含有芘酰磷脂酰胆碱（PyrPC）（PyrPC-rHDL）的重构HDL（rHDL）颗粒。在与PLTP孵育后，它们表现为天然HDL，因为它们的大小显著增加。2.当PyrPC-rHDL与HDL（3）在PLTP存在下孵育时，芘准分子/单体荧光比率（E/M）发生快速下降，表明PLTP诱导PyrPC-rHDL和HDL（3）的表面脂质混合。由于这种混合在观察到HDL颗粒尺寸的任何显著增加之前几乎完成，因此其代表不与大HDL颗粒的形成直接偶联的PLT介导的磷脂转移或交换。3.当核心标记的PyrCE-rHDL在PLTP存在下孵育时，观察到E/M的慢得多的时间依赖性降低，表明PLTP也促进核心脂质的混合。核心脂质的混合速率和程度与PLTP的添加量和粒度的增加相关。通过电子显微镜可以将形成的扩大颗粒视为离散的、非聚集的颗粒。伴随着增大颗粒的出现，释放出贫脂的apoA-I分子。这些数据，连同PLTP已显示不介导胆固醇酯转移的事实，强烈表明颗粒融合而不是（净）脂质转移或颗粒聚集是与PLTP孵育后观察到的HDL颗粒增大的原因。4. apoA-I rHDL，而不是apoA-II rHDL，被转化为大颗粒，表明apoA-I的存在是PLT介导的HDL融合所必需的。一个模型PLTP介导的HDL颗粒的扩大。
1. Phospholipid transfer protein (PLTP) mediates conversion of high-density lipoprotein (HDL(3)) to large particles, with concomitant release of apolipoprotein A-I (apoA-I). To study the mechanisms involved in this conversion, reconstituted HDL (rHDL) particles containing either fluorescent pyrenylacyl cholesterol ester (PyrCE) in their core (PyrCE-rHDL) or pyrenylacyl phosphatidylcholine (PyrPC) in their surface lipid layer (PyrPC-rHDL) were prepared. Upon incubation with PLTP they behaved as native HDL,, in that their size increased considerably. 2. When PyrPC-rHDL was incubated with HDL(3) in the presence of PLTP, a rapid decline of the pyrene excimer/monomer fluorescence ratio (E/M) occurred, demonstrating that PLTP induced mixing of the surface lipids of PyrPC-rHDL and HDL(3). As this mixing was almost complete before any significant increase in HDL particle size was observed, it represents PLTP-mediated phospholipid transfer or exchange that is not directly coupled to the formation of large HDL particles. 3. When core-labelled PyrCE-rHDL was incubated in the presence of PLTP, a much slower, time-dependent decrease of E/M was observed, demonstrating that PLTP also promotes mixing of the core lipids. The rate and extent of mixing of core lipids correlated with the amount of PLTP added and with the increase in particle size. The enlarged particles formed could be visualized as discrete, nonaggregated particles by electron microscopy. Concomitantly with the appearance of enlarged particles, lipid-poor apoA-I molecules were released. These data, together with the fact that PLTP has been shown not to mediate transfer of cholesterol esters, strongly suggest that particle fusion rather than (net) lipid transfer or particle aggregation is responsible for the enlargement of HDL particles observed upon incubation with PLTP. 4. ApoA-I rHDL, but not apoA-II rHDL, were converted into large particles, suggesting that the presence of apoA-I is required for PLTP-mediated HDL fusion. A model for PLTP-mediated enlargement of HDL particles is presented.