Characterization of nascent HDL particles and microparticles formed by ABCA1-mediated efflux of cellular lipids to apoA-I
Characterization of nascent HDL particles and microparticles formed by ABCA1-mediated efflux of cellular lipids to apoA-I
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DOI：
10.1194/jlr.m500531-jlr200
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发表时间：
2006-04-01
影响因子：
6.5
通讯作者：
Phillips, MC
中科院分区：
文献类型：
--
作者：
Duong, PT;Collins, HL;Phillips, MC
由 ABCA1 介导的细胞磷脂 (PL) 和游离（未酯化）胆固醇 (FC) 流出至载脂蛋白 A-I (apoA-I) 所产生的新生 HDL 尚未确定。为了解决这个问题，我们对 J774 小鼠巨噬细胞和 ABCA1 被激活的人皮肤成纤维细胞与人 apoA-I 一起孵育时释放的脂质颗粒进行了表征。在这两种情况下，都会形成三种类型的新生 HDL，每个颗粒含有两个、三个或四个 apoA-I 分子。对于 J774 细胞，主要物种的流体动力学直径类似于 9 和 12 nm。这些盘状 HDL 颗粒具有不同的 FC 含量和 PL 组成，酸性 PL 的存在导致它们表现出 α 电泳迁移率。这些结果与 ABCA1 位于多个膜微环境中并负责异质 HDL 的产生一致。 ABCA1 的激活还会导致不含 apoA-I 的质膜囊泡（微粒）的释放。 J774 细胞释放的这些较大的球形颗粒具有与 12 nm HDL 相同的 PL 组成，并含有 CD14 和神经节苷脂，这与其质膜筏结构域的起源一致。各种HDL颗粒和微粒是同时产生的，它们之间不存在前体-产物关系。重要的是，ABCA1 从这些细胞流出的细胞 FC 的很大一部分位于微粒中。总的来说，这些结果表明 apoA-I/ABCA1 相互作用的产物包括含有不同数量的 apoA-I 分子的盘状 HDL 颗粒。掺入这些新生 HDL 颗粒中的细胞 PL 和胆固醇源自不同的细胞膜域。
The nascent HDL created by ABCA1-mediated efflux of cellular phospholipid ( PL) and free ( unesterified) cholesterol ( FC) to apolipoprotein A-I ( apoA-I) has not been defined. To address this issue, we characterized the lipid particles released when J774mouse macrophages and human skin fibroblasts in which ABCA1 is activated are incubated with human apoA-I. In both cases, three types of nascent HDL containing two, three, or four molecules of apoA-I per particle are formed. With J774 cells, the predominant species have hydrodynamic diameters of similar to 9 and 12 nm. These discoidal HDL particles have different FC contents and PL compositions, and the presence of acidic PL causes them to exhibit alpha-electrophoretic mobility. These results are consistent with ABCA1 located in more than one membrane microenvironment being responsible for the production of the heterogeneous HDL. Activation of ABCA1 also leads to the release of apoA-I-free plasma membrane vesicles ( microparticles). These larger, spherical particles released from J774 cells have the same PL composition as the 12 nm HDL and contain CD14 and ganglioside, consistent with their origin being plasma membrane raft domains. The various HDL particles and microparticles are created concurrently, and there is no precursor-product relationship between them. Importantly, a large fraction of the cellular FC effluxed from these cells by ABCA1 is located in microparticles. Collectively, these results show that the products of the apoA-I/ABCA1 interaction include discoidal HDL particles containing different numbers of apoA-I molecules. The cellular PLs and cholesterol incorporated into these nascent HDL particles originate from different cell membrane domains.