SR-BI/CD36 Chimeric Receptors Define Extracellular Subdomains of SR-BI Critical for Cholesterol Transport
SR-BI/CD36 Chimeric Receptors Define Extracellular Subdomains of SR-BI Critical for Cholesterol Transport
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DOI：
10.1021/bi500706x
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发表时间：
2014-10-07
期刊：
影响因子：
2.9
通讯作者：
Sahoo, Daisy
中科院分区：
文献类型：
--
作者：
Kartz, Gabriella A.;Holme, Rebecca L.;Sahoo, Daisy
高密度脂蛋白（hdl）具有动脉粥样硬化保护作用，主要是因为它们能够通过逆向胆固醇转运（RCT）促进胆固醇从外周组织向肝脏的流动。高密度脂蛋白胆固醇酯（CE）进入细胞是由高密度脂蛋白受体，B类I型清道夫受体（SR-BI）介导的，它是增强全身胆固醇处置和预防心血管疾病的一个有希望的靶点。对于支持细胞选择性摄取HDL- ce的适当SR-BI/HDL排列的结构决定因素的详细了解仍然缺乏。为此，我们利用了CD36，这是一种B类清道夫受体，其预测拓扑结构与SR-BI相似，可结合HDL，但无法介导HDL- ce的有效选择性摄取。我们生成了一系列SR-BI/CD36嵌合受体，它们跨越SR-BI的细胞外（EC）结构域，以描绘SR-BI的胆固醇转运功能所必需的区域。所有16个SR-BI/CD36嵌合体均在COS-7细胞中瞬时表达，并证实其质膜定位。大多数SR-BI/CD36嵌合受体(i)结合HDL， （ii）将HDL- ce传递到细胞，（iii）介导游离胆固醇（FC）向HDL的外排，以及（iv）重新分配FC的质膜结构域的能力显着降低。我们还证明SR-BI功能的变化与受体寡聚化无关。总之，我们已经确定了离散的子结构域，特别是在SR-BI的EC结构域的n端和c端区域，这对产生受体配体至关重要。
High-density lipoproteins (HDLs) are athero-protective, primarily because of their ability to promote cholesterol flux from peripheral tissues to the liver by reverse cholesterol transport (RCT). The delivery of HDL-cholesteryl esters (CE) into cells is mediated by the HDL receptor, scavenger receptor class B type I (SR-BI), a promising target for enhancing whole body cholesterol disposal and preventing cardiovascular disease. A detailed understanding of the structural determinants underlying proper SR-BI/HDL alignment that supports the selective uptake of HDL-CE into cells remains lacking. To this end, we exploited CD36, a class B scavenger receptor with a predicted topology smiliar to that of SR-BI that binds HDL but is unable to mediate efficient selective uptake of HDL-CE. We generated a series of SR-BI/CD36 chimeric receptors that span the extracellular (EC) domain of SR-BI to delineate regions that are essential of SR-BI's cholesterol transport functions. All 16 SR-BI/CD36 chimeras were transiently expressed din COS-7 cells, and their plasma membrane localization was confirmed. The majority of SR-BI/CD36 chimeric receptors displayed significant reductions in their ability to (i) bind HDL, (ii) deliver HDL-CE to cells, (iii) mediate efflux of free cholesterol (FC) to HDL, and (iv) redistribute plasma membrane domains of FC. We also demonstrated that changes in SR-BI function were independent of receptor oligomerization. Altogether, we have identified discrete subdomains, particularly in the N-terminal and C-terminal regions of the EC domains of SR-BI, that are critical for productive receptor-ligand.