Brown D, Weyer P, Orci L
Anat Rec. 1987 Jul;218(3):237-42. doi: 10.1002/ar.1092180303.
Intercalated cells of the kidney collecting duct are able to modify the structure of their apical plasma membrane in response to different physiological conditions. It has been proposed that this process involves the transfer of membrane components (including a proton-pumping ATPase) to and from the apical membrane by a specialized population of tubulovesicles that are found in the apical cytoplasm of these cells. These vesicles have a prominent cytoplasmic coat of regularly arranged dense studs that we have recently shown to be immunocytochemically and morphologically distinct from clathrin. In this study, we have examined the function of these vesicles by using horseradish peroxidase as a tracer of endocytosis at the light and electron microscopic levels. Following the intravenous injection of rats with the tracer, we found a massive labeling of the tubulovesicle compartment of intercalated cells, providing direct evidence that these nonclathrin-coated vesicles are involved in endocytotic events in this cell type. This novel membrane coating material could contain the cytoplasmic domains of molecules transported to and from the plasma membrane by these vesicles (e.g., and H+ ATPase) or it could be a molecule that is involved in vesicle function, by analogy with clathrin.
肾集合管的闰细胞能够根据不同的生理条件改变其顶端质膜的结构。有人提出，这一过程涉及膜成分（包括质子泵ATP酶）通过存在于这些细胞顶端细胞质中的特殊管状小泡在顶端膜与其他部位之间的转移。这些小泡有一层由规则排列的致密颗粒组成的显著细胞质衣被，我们最近通过免疫细胞化学和形态学研究表明，它们与网格蛋白不同。在本研究中，我们通过使用辣根过氧化物酶作为内吞作用的示踪剂，在光学显微镜和电子显微镜水平上研究了这些小泡的功能。给大鼠静脉注射示踪剂后，我们发现闰细胞的管状小泡区有大量标记，这提供了直接证据，表明这些非网格蛋白包被的小泡参与了这种细胞类型的内吞事件。这种新型的膜包被物质可能包含通过这些小泡运输到质膜和从质膜运输出的分子的细胞质结构域（例如H⁺ATP酶），或者它可能是一种类似于网格蛋白的、参与小泡功能的分子。
