Constitutive clathrin-mediated endocytosis of CTLA-4 persists during T cell activation.
Constitutive clathrin-mediated endocytosis of CTLA-4 persists during T cell activation.
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DOI：
10.1074/jbc.m111.304329
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发表时间：
2012-03-16
期刊：
影响因子：
--
通讯作者：
Sansom DM
中科院分区：
文献类型：
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作者：
Qureshi OS;Kaur S;Hou TZ;Jeffery LE;Poulter NS;Briggs Z;Kenefeck R;Willox AK;Royle SJ;Rappoport JZ;Sansom DM
背景：CTLA-4是T细胞免疫应答的重要调节因子，具有不寻常的细胞内运输。结果：CTLA-4的内吞是连续的，随后再循环和降解。结论：网格蛋白介导的CTLA-4内吞作用持续存在于活化的T细胞中。意义：这改变了我们对CTLA-4行为的理解，因此，它可能如何发挥作用。CTLA-4是T细胞免疫应答的最重要的负调节因子之一。然而，CTLA-4的亚细胞分布对于与细胞表面跨膜配体相互作用的受体是不寻常的，因为CTLA-4从质膜快速内化。已经提出T细胞活化可以导致细胞表面CTLA-4表达的稳定。在这里，我们详细分析了CTLA-4的内化、回收和降解。我们证明，CTLA-4是迅速内化从质膜在网格蛋白和动力蛋白依赖性的方式驱动的良好特征的YVKM贩运基序。此外，我们表明，一旦内化，CTLA-4与再循环内体的标记物共定位，并被再循环到质膜。尽管我们观察到CTLA-4与溶酶体标志物的有限共定位，但CTLA-4仍以溶酶体阻断抑制的方式降解。T细胞活化刺激CTLA-4的动员，如通过细胞表面表达的增加所判断的;然而，该CTLA-4池继续内吞并且不稳定地保留在细胞表面。这些数据支持一种贩运模型，其中CTLA-4以不依赖配体的方式组成性内化，经历再循环和降解。T细胞的刺激增加了质膜上的CTLA-4周转;然而，CTLA-4内吞作用在人T细胞的活化期间继续并且不稳定。这些发现强调了网格蛋白介导的内吞作用在整个T细胞活化过程中调节CTLA-4运输的重要性。
Background: CTLA-4 is an essential regulator of T cell immune responses with unusual intracellular trafficking. Results: Endocytosis of CTLA-4 is continuous with subsequent recycling and degradation. Conclusion: Clathrin-mediated endocytosis of CTLA-4 persists in activated T cells. Significance: This alters our understanding of CTLA-4 behavior and, therefore, how it might function. CTLA-4 is one of the most important negative regulators of the T cell immune response. However, the subcellular distribution of CTLA-4 is unusual for a receptor that interacts with cell surface transmembrane ligands in that CTLA-4 is rapidly internalized from the plasma membrane. It has been proposed that T cell activation can lead to stabilization of CTLA-4 expression at the cell surface. Here we have analyzed in detail the internalization, recycling, and degradation of CTLA-4. We demonstrate that CTLA-4 is rapidly internalized from the plasma membrane in a clathrin- and dynamin-dependent manner driven by the well characterized YVKM trafficking motif. Furthermore, we show that once internalized, CTLA-4 co-localizes with markers of recycling endosomes and is recycled to the plasma membrane. Although we observed limited co-localization of CTLA-4 with lysosomal markers, CTLA-4 was nonetheless degraded in a manner inhibited by lysosomal blockade. T cell activation stimulated mobilization of CTLA-4, as judged by an increase in cell surface expression; however, this pool of CTLA-4 continued to endocytose and was not stably retained at the cell surface. These data support a model of trafficking whereby CTLA-4 is constitutively internalized in a ligand-independent manner undergoing both recycling and degradation. Stimulation of T cells increases CTLA-4 turnover at the plasma membrane; however, CTLA-4 endocytosis continues and is not stabilized during activation of human T cells. These findings emphasize the importance of clathrin-mediated endocytosis in regulating CTLA-4 trafficking throughout T cell activation.