Cholesterol binding, efflux, and a PDZ-interacting domain of scavenger receptor-BI mediate HDL-initiated signaling
Cholesterol binding, efflux, and a PDZ-interacting domain of scavenger receptor-BI mediate HDL-initiated signaling
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DOI：
10.1172/jci200523858
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发表时间：
2005-04-01
影响因子：
15.9
通讯作者：
Silver, DL
中科院分区：
文献类型：
--
作者：
Assanasen, C;Mineo, C;Silver, DL
高密度脂蛋白与清道夫受体BI(SR-111)的结合介导了胆固醇的运动。高密度脂蛋白还可以诱导多种细胞信号，在内皮细胞中。通过SR-BI发生并融合以激活eNOS。为了确定高密度脂蛋白诱导的信号事件的分子基础，我们研究了高密度脂蛋白激活eNOS的近端机制。在内皮细胞中，高密度脂蛋白和甲基-β-环糊精可引起类似的eNOS激活，而胆固醇负载的甲基-β-环糊精则没有影响。载磷脂酰胆碱的高密度脂蛋白比天然高密度脂蛋白产生更大的刺激，阻断SR-BI抗体，防止胆固醇外流，阻止eNOS激活。在COS-M6细胞的重建模型中，野生型SR-BI同时通过高密度脂蛋白和小单层囊泡(SUV)介导eNOS的激活，而SR-BI突变体AVI不能外排到SUV，仅通过高密度脂蛋白传递信号。此外，甲基-β-环糊精对eNOS的激活依赖于SR-BI。对突变型和嵌合型B类清道夫受体的研究表明，SR-BI的C端胞质PDZ相互作用结构域和C端跨膜结构域都是高密度脂蛋白信号传递所必需的。此外，我们使用一种光活化的胆固醇衍生物证明了胆固醇与C端跨膜结构域的直接结合。因此，高密度脂蛋白信号需要胆固醇结合和SR-BI的外流和C-末端结构域，SR-BI作为质膜上的胆固醇传感器。
The binding of HDL to scavenger receptor-BI (SR-111) mediates cholesterol movement. HDL also induces multiple cellular signals, which in endothelium. occur through SR-BI and converge to activate eNOS. To determine the molecular basis of a signaling event induced by HDL, we examined the proximal mechanisms in HDL activation of eNOS. in endothelial cells, HDL and methyl-beta-cyclodextrin caused comparable eNOS activation, whereas cholesterol-loaded methyl-beta-cyclodextrin had no effect. Phosphatidylcholine-loaded HDL caused greater stimulation than native HDL, and blocking antibody against SR-BI, which prevents cholesterol efflux, prevented eNOS activation. In a reconstitution model in COS-M6 cells, wild-type SR-BI mediated eNOS activation by both HDL and small unilamellar vesicles (SUVs), whereas the SR-BI mutant AVI, which is incapable of efflux to SUV, transmitted signal by only HDL. In addition, eNOS activation by methyl-beta-cyclodextrin was SR-BI dependent. Studies of mutant and chimeric class B scavenger receptors revealed that the C-terminal cytoplasmic PDZ-interacting domain and the C-terminal transmembrane domains of SR-BI are both necessary for HDL signaling. Furthermore, we demonstrated direct binding of cholesterol to the C-terminal transmembrane domain using a photoactivated derivative of cholesterol. Thus, HDL signaling requires cholesterol binding and efflux and C-terminal domains of SR-BI, and SR-BI serves as a cholesterol sensor on the plasma membrane.