Alix regulates cortical actin and the spatial distribution of endosomes
Alix regulates cortical actin and the spatial distribution of endosomes
复制标题
DOI：
10.1242/jcs.02382
复制
发表时间：
2005-06-15
影响因子：
4
通讯作者：
Stenmark, H
中科院分区：
文献类型：
--
作者：
Cabezas, A;Bache, KG;Stenmark, H
Alix/AIP1是一种富含脯氨酸的蛋白，与细胞凋亡、胞膜转运和病毒萌发有关。为了进一步阐明Alix的功能，我们使用了RNA干扰来特异性地抑制其表达。Alix的耗尽导致早期内体从外周到核周的显着重新分布。尽管Alix下调时转铁蛋白的摄取略有减少，但内体的重新分布并不影响转铁蛋白的循环利用或内吞的表皮生长因子受体的降解。定量免疫电子显微镜显示Alix耗竭细胞的多囊内体含有正常数量的CD63，但其溶二磷脂酸水平降低。Alix的耗尽还导致了不寻常的肌动蛋白结构的积累，其中包含网状蛋白和皮质肌动蛋白，这是一种将膜动力学与皮质肌动蛋白细胞骨架偶联的蛋白质。我们的结果表明，Alix在依赖肌动蛋白的内吞体内定位中发挥作用，但对于内吞循环或非极化细胞中早期和晚期内容体之间的膜蛋白运输并不是必需的。
Alix/AIP1 is a proline-rich protein that has been implicated in apoptosis, endocytic membrane trafficking and viral budding. To further elucidate the functions of Alix, we used RNA interference to specifically suppress its expression. Depletion of Alix caused a striking redistribution of early endosomes from a peripheral to a perinuclear location. The redistribution of endosomes did not affect transferrin recycling or degradation of endocytosed epidermal growth factor receptors, although the uptake of transferrin was mildly reduced when Alix was downregulated. Quantitative immunoelectron microscopy showed that multivesicular endosomes of Alix-depleted cells contained normal amounts of CD63, whereas their levels of lysobisphosphatidic acid were reduced. Alix depletion also caused an accumulation of unusual actin structures that contained clathrin and cortactin, a protein that couples membrane dynamics to the cortical actin cytoskeleton. Our results suggest that Alix functions in the actin-dependent intracellular positioning of endosomes, but that it is not essential for endocytic recycling or for trafficking of membrane proteins between early and late endosomes in non-polarised cells.