Evidence for the sorting of endocytic vesicle contents during the receptor-mediated transport of IgG across the newborn rat intestine.
Evidence for the sorting of endocytic vesicle contents during the receptor-mediated transport of IgG across the newborn rat intestine.
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DOI：
10.1083/jcb.91.1.270
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发表时间：
1981-10
影响因子：
7.8
通讯作者：
Rodewald, R
中科院分区：
文献类型：
--
作者：
Abrahamson, D R;Rodewald, R
新生大鼠肠上皮细胞腔膜上的Fc受体介导功能完整的IgG从肠腔到循环的囊泡转移。此外，存在低水平的非选择性蛋白质摄取，但在这种情况下不会发生转移。为了确定是否一个专门的类的内吞囊泡可以占IgG的选择性转移，IgG结合铁蛋白（IgG-Ft）和未结合辣根过氧化物酶（HRP）的混合物一起注射到近端肠的10-D-老大鼠，和这两种不同的示踪剂的细胞分布，通过电子显微镜测定。几乎所有的顶端内吞囊泡都含有两种示踪剂，表明同一囊泡内同时摄取两种蛋白质。然而，只有IgG-Ft结合到顶端质膜，出现在包被囊泡在侧细胞表面，并从细胞中释放。HRP没有结合到管腔膜，并没有跨细胞转移，但仅限于顶端溶酶体所确定的酸性磷酸酶和芳基硫酸酯酶的活动。为了测试IgG与其受体的结合刺激内吞作用的可能性，HRP被用作流体体积示踪剂，并且在存在和不存在IgG的情况下通过细胞摄取的HRP的量进行形态学和生物化学测量。结果表明，这些细胞中的内吞作用是组成性的，并且在不存在IgG的情况下以相同的水平发生。所提出的证据表明，IgG转移的主要选择性机制是在胞吞作用期间IgG与其受体的结合。持续结合囊泡膜似乎是成功转移所需的，因为未结合的蛋白质在胞吐作用之前从转运途径中除去。这些结果支持IgG作为IgG-受体复合物跨细胞转移的提议。
Fc receptors on the luminal membranes of intestinal epithelial cells in the neonatal rat mediate the vesicular transfer of functionally intact IgG from the intestinal lumen to the circulation. In addition, there is a low level of nonselective protein uptake, but in this case transfer does not occur. To determine whether a specialized class of endocytic vesicles could account for the selective transfer of IgG, mixtures of IgG conjugated to ferritin (IgG-Ft) and unconjugated horseradish peroxidase (HRP) were injected together into the proximal intestine of 10-d-old rats, and the cellular distribution of these two different tracers was determined by electron microscopy. Virtually all apical endocytic vesicles contained both tracers, indicating simultaneous uptake of both proteins within the same vesicle. However, only IgG-Ft bound to the apical plasma membrane, appeared within coated vesicles at the lateral cell surface, and was released from cells. HRP did not bind to the luminal membrane and was not transferred across cells but was confined to apical lysosomes as identified by acid phosphatase and aryl sulfatase activities. To test the possibility that the binding of IgG to its receptor stimulated endocytosis, HRP was used as a fluid volume tracer, and the amount of HRP taken up by cells in the presence and absence of IgG was measured morphologically and biochemically. The results demonstrate that endocytosis in these cells is constitutive and occurs at the same level in the absence of IgG. The evidence presented indicates that the principal selective mechanism for IgG transfer is the binding of IgG to its receptor during endocytosis. Continued binding to vesicle membranes appears to be required for successful transfer because unbound proteins are removed from the transport pathway before exocytosis. These results favor the proposal that IgG is transferred across cells as an IgG-receptor complex.