Structurally distinct endocytic pathways for B cell receptors in B lymphocytes.
Structurally distinct endocytic pathways for B cell receptors in B lymphocytes.
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DOI：
10.1091/mbc.e20-08-0532
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发表时间：
2020-12-01
影响因子：
3.3
通讯作者：
Taraska JW
中科院分区：
文献类型：
--
作者：
Roberts AD;Davenport TM;Dickey AM;Ahn R;Sochacki KA;Taraska JW
B淋巴细胞在获得性免疫中起关键作用。在抗原结合时，B细胞受体（BCR）聚集在质膜上并通过内吞作用内化。在此过程中，B细胞在各种环境和浓度下捕获不同的抗原。然而，目前还不清楚BCR内吞作用的机制是否会因这些因素而改变。在这里，我们研究了可溶性抗原诱导的BCR聚集和内化的机制，在培养的人B细胞系使用相关的超分辨荧光和铂复制电子显微镜。首先，通过可视化纳米级BCR簇，我们提供了直接的证据表明，BCR簇的大小随F（ab '）2浓度的增加。接下来，我们表明，响应于BCR集群大小的内在化开关的物理机制。在低浓度的抗原下，B细胞通过经典的网格蛋白介导的内吞作用内化小的BCR簇。在高抗原浓度下，当簇大小增加超过单个网格蛋白包被的小凹的大小时，B细胞使用被网格蛋白覆盖的质膜的大内陷来取回受体簇。在这些网站上，我们观察到早期和持续的招聘肌动蛋白和肌动蛋白聚合蛋白FCHSD 2。我们进一步表明，肌动蛋白的招聘需要有效地产生这些新的内吞载体和捕获到胞质溶胶。我们提出，在B细胞中，内吞作用的机制切换到容纳当细胞遇到高浓度的可溶性抗原时形成的大受体簇。这种机制是由皮层肌动蛋白细胞骨架的组织和动力学调节的。
B lymphocytes play a critical role in adaptive immunity. On antigen binding, B cell receptors (BCR) cluster on the plasma membrane and are internalized by endocytosis. In this process, B cells capture diverse antigens in various contexts and concentrations. However, it is unclear whether the mechanism of BCR endocytosis changes in response to these factors. Here, we studied the mechanism of soluble antigen-induced BCR clustering and internalization in a cultured human B cell line using correlative superresolution fluorescence and platinum replica electron microscopy. First, by visualizing nanoscale BCR clusters, we provide direct evidence that BCR cluster size increases with F(ab’)2 concentration. Next, we show that the physical mechanism of internalization switches in response to BCR cluster size. At low concentrations of antigen, B cells internalize small BCR clusters by classical clathrin-mediated endocytosis. At high antigen concentrations, when cluster size increases beyond the size of a single clathrin-coated pit, B cells retrieve receptor clusters using large invaginations of the plasma membrane capped with clathrin. At these sites, we observed early and sustained recruitment of actin and an actin polymerizing protein FCHSD2. We further show that actin recruitment is required for the efficient generation of these novel endocytic carriers and for their capture into the cytosol. We propose that in B cells, the mechanism of endocytosis switches to accommodate large receptor clusters formed when cells encounter high concentrations of soluble antigen. This mechanism is regulated by the organization and dynamics of the cortical actin cytoskeleton.
DOI：
10.1007/978-1-4939-6810-7_11
发表时间：
2017
期刊：
Methods in molecular biology (Clifton, N.J.)
影响因子：
--
作者：
Trexler AJ;Taraska JW
通讯作者：
Taraska JW