Depletion of rafts in late endocytic membranes is controlled by NPC1-dependent recycling of cholesterol to the plasma membrane.
Depletion of rafts in late endocytic membranes is controlled by NPC1-dependent recycling of cholesterol to the plasma membrane.
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发表时间：
2001-05
影响因子：
4
通讯作者：
S. Lusa;Titta S. Blom;E. Eskelinen;E. Kuismanen;J. Månsson;K. Simons;E. Ikonen
中科院分区：
文献类型：
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作者：
S. Lusa;Titta S. Blom;E. Eskelinen;E. Kuismanen;J. Månsson;K. Simons;E. Ikonen
在哺乳动物细胞中，胆固醇被认为与鞘脂结合形成被称为筏的侧膜结构域。越来越多的证据表明，木筏调控蛋白质的相互作用，例如，在信号传递、细胞内运输和宿主-病原体相互作用过程中。木筏存在于富含胆固醇的神经鞘脂膜中，包括早期和再循环的内小体，但是否在晚期的内吞细胞器中发现木筏还没有被分析。在这项研究中，我们分析了胆固醇和晚期内体蛋白与正常细胞中的低密度洗涤剂耐受膜(DRM)以及溶酶体胆固醇-鞘磷脂蓄积的细胞中的关系。在正常细胞中，[(3)H]胆固醇酯-低密度脂蛋白与洗涤剂可溶的膜结合，释放出的大部分[(3)H]胆固醇被迅速转运到质膜，并随着时间的推移变得越来越不溶解。在Niemann-Pick C1(NPC1)蛋白缺陷型脂肪沉积细胞中，低密度脂蛋白-胆固醇与DRM的结合增强，其向质膜的转运被抑制。此外，NPC1蛋白通常在洗涤剂可溶的膜中恢复，其与DRM的联系通过溶酶体胆固醇负荷而增强。此外，溶酶体的胆固醇沉积与神经鞘脂脂的隔离和晚期内吞细胞器中多层小体的形成在动力学上是平行的。这些结果表明，晚期内吞细胞器通常是无RAFT的，内吞的低密度脂蛋白在NPC1依赖的过程中被有效地循环到质膜。胆固醇鞘磷脂堆积是鼻咽癌疾病的特征，也可能是其他鞘磷脂疾病的特征，导致降解室中形成板层小体的木筏过度拥挤。
In mammalian cells, cholesterol is thought to associate with sphingolipids to form lateral membrane domains termed rafts. Increasing evidence suggests that rafts regulate protein interactions, for example, during signalling, intracellular transport and host-pathogen interactions. Rafts are present in cholesterol-sphingolipid-enriched membranes, including early and recycling endosomes, but whether rafts are found in late endocytic organelles has not been analyzed. In this study, we analyzed the association of cholesterol and late endosomal proteins with low-density detergent-resistant membranes (DRMs) in normal cells and in cells with lysosomal cholesterol-sphingolipid accumulation. In normal cells, the majority of [(3)H]cholesterol released from [(3)H]cholesterol ester-LDL associated with detergent-soluble membranes, was rapidly transported to the plasma membrane and became increasingly insoluble with time. In Niemann-Pick C1 (NPC1) protein-deficient lipidosis cells, the association of LDL-cholesterol with DRMs was enhanced and its transport to the plasma membrane was inhibited. In addition, the NPC1 protein was normally recovered in detergent-soluble membranes and its association with DRMs was enhanced by lysosomal cholesterol loading. Moreover, lysosomal cholesterol deposition was kinetically paralleled by the sequestration of sphingolipids and formation of multilamellar bodies in late endocytic organelles. These results suggest that late endocytic organelles are normally raft-poor and that endocytosed LDL-cholesterol is efficiently recycled to the plasma membrane in an NPC1-dependent process. The cholesterol-sphingolipid accumulation characteristic to NPC disease, and potentially to other sphingolipidoses, causes an overcrowding of rafts forming lamellar bodies in the degradative compartments.