Expression of scavenger receptor class B type 1 (SR-BI) promotes microvillar channel formation and selective cholesteryl ester transport in a heterologous reconstituted system.
Expression of scavenger receptor class B type 1 (SR-BI) promotes microvillar channel formation and selective cholesteryl ester transport in a heterologous reconstituted system.
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DOI：
10.1073/pnas.98.4.1613
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发表时间：
2001-02
影响因子：
11.1
通讯作者：
E. Reaven;S. Leers-sucheta;A. Nomoto;Salman Azhar
中科院分区：
文献类型：
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作者：
E. Reaven;S. Leers-sucheta;A. Nomoto;Salman Azhar
在“选择性”摄取胆固醇酯(CE)的过程中，表面相关脂蛋白[高密度脂蛋白(高密度脂蛋白)和低密度脂蛋白]被困在激素刺激的类固醇生成细胞中紧密相对的表面微绒毛(微绒毛通道)之间的空间中。这是发现高密度脂蛋白受体(SR-BI)的同一位置。在目前的研究中，我们试图了解SR-BI和异源昆虫细胞系统中选择性摄取CE的关系。通过Western印迹分析和光镜或电子免疫显微镜检测高表达重组SR-BI的Sf9细胞的SR-BI蛋白，以及(Ii)放射性标记或荧光(BODIPY-CE)标记的高密度脂蛋白(HDLE)选择性摄取脂蛋白CE。未感染或感染对照Sf9细胞不表达SR-BI，不显示微绒毛通道，也不内化CES。一个意想不到的发现是在表达SR-BI的Sf9细胞中诱导了一个复杂的通道系统。SR-BI表达的细胞显示许多细胞表面的双膜通道，免疫金标SR-BI，通道的载脂蛋白(HDL)标记，以及高水平的选择性摄取HDLCE。因此，在异源系统中表达重组SR-BI可以诱导双膜通道，这些特殊结构促进了高密度脂蛋白的结合和选择性地摄取高密度脂蛋白-CE。
In the "selective" cholesteryl ester (CE) uptake process, surface-associated lipoproteins [high density lipoprotein (HDL) and low density lipoprotein] are trapped in the space formed between closely apposed surface microvilli (microvillar channels) in hormone-stimulated steroidogenic cells. This is the same location where an HDL receptor (SR-BI) is found. In the current study, we sought to understand the relationship between SR-BI and selective CE uptake in a heterologous insect cell system. Sf9 (Spodoptera frugiperda) cells overexpressing recombinant SR-BI were examined for (i) SR-BI protein by Western blot analysis and light or electron immunomicroscopy, and (ii) selective lipoprotein CE uptake by the use of radiolabeled or fluorescent (BODIPY-CE)-labeled HDL. Noninfected or infected control Sf9 cells do not express SR-BI, show microvillar channels, or internalize CEs. An unexpected finding was the induction of a complex channel system in Sf9 cells expressing SR-BI. SR-BI-expressing cells showed many cell surface double-membraned channels, immunogold SR-BI, apolipoprotein (HDL) labeling of the channels, and high levels of selective HDL-CE uptake. Thus, double-membraned channels can be induced by expression of recombinant SR-BI in a heterologous system, and these specialized structures facilitate both the binding of HDL and selective HDL-CE uptake.