Filipin-sensitive caveolae-mediated transport in endothelium: reduced transcytosis, scavenger endocytosis, and capillary permeability of select macromolecules.
Filipin-sensitive caveolae-mediated transport in endothelium: reduced transcytosis, scavenger endocytosis, and capillary permeability of select macromolecules.
复制标题
DOI：
10.1083/jcb.127.5.1217
复制
发表时间：
1994-12
期刊：
影响因子：
--
通讯作者：
Allard J
中科院分区：
文献类型：
--
作者：
Schnitzer JE;Oh P;Pinney E;Allard J
质膜小囊或无包膜小泡存在于多种细胞中，参与了许多重要的细胞功能，包括内吞作用、转胞吞作用和光胞吞作用。它们在跨内皮转运中的功能尤其有争议，至少部分是因为没有任何方法选择性地抑制这种假定的途径。我们现在表明，甾醇结合剂，如菲律平的能力，拆卸内皮非涂层，但没有涂层质膜囊泡选择性抑制小窝介导的细胞内和跨细胞运输的选择大分子在内皮细胞。Filipin显著降低胰岛素和白蛋白跨培养的内皮细胞单层的跨细胞转运。大鼠肺微血管对白蛋白的通透性在菲律平灌注后明显降低。相反，细胞旁运输的小溶质菊粉在体外或原位不受抑制。此外，我们表明，小窝介导的清除剂内吞的构象修饰的白蛋白传递到内体和溶酶体降解。这种细胞内转运在体外和原位均被菲律宾肽抑制。其他甾醇结合剂包括制霉菌素和毛地黄皂苷也抑制这种降解过程。相反，活化α 2-巨球蛋白（网格蛋白依赖性途径的已知配体）的内吞作用和降解不受影响。有趣的是，菲律平似乎可以抑制内皮细胞对胰岛素的摄入，以进行转胞吞作用（一种小窝介导的过程），但不会抑制内吞作用以进行降解，这显然是由网格蛋白包被途径介导的。这种对小窝的选择性抑制不仅为小窝在内皮细胞中选择的大分子的细胞内和跨细胞转运中的作用提供了关键证据，而且还可用于区分由包被囊泡与非包被囊泡介导的转运。
Caveolae or noncoated plasmalemmal vesicles found in a variety of cells have been implicated in a number of important cellular functions including endocytosis, transcytosis, and potocytosis. Their function in transport across endothelium has been especially controversial, at least in part because there has not been any way to selectively inhibit this putative pathway. We now show that the ability of sterol binding agents such as filipin to disassemble endothelial noncoated but not coated plasmalemmal vesicles selectively inhibits caveolae-mediated intracellular and transcellular transport of select macromolecules in endothelium. Filipin significantly reduces the transcellular transport of insulin and albumin across cultured endothelial cell monolayers. Rat lung microvascular permeability to albumin in situ is significantly decreased after filipin perfusion. Conversely, paracellular transport of the small solute inulin is not inhibited in vitro or in situ. In addition, we show that caveolae mediate the scavenger endocytosis of conformationally modified albumins for delivery to endosomes and lysosomes for degradation. This intracellular transport is inhibited by filipin both in vitro and in situ. Other sterol binding agents including nystatin and digitonin also inhibit this degradative process. Conversely, the endocytosis and degradation of activated alpha 2- macroglobulin, a known ligand of the clathrin-dependent pathway, is not affected. Interestingly, filipin appears to inhibit insulin uptake by endothelium for transcytosis, a caveolae-mediated process, but not endocytosis for degradation, apparently mediated by the clathrin-coated pathway. Such selective inhibition of caveolae not only provides critical evidence for the role of caveolae in the intracellular and transcellular transport of select macromolecules in endothelium but also may be useful for distinguishing transport mediated by coated versus noncoated vesicles.