The chemokine receptor CXCR3 is degraded following internalization and is replenished at the cell surface by de novo synthesis of receptor
The chemokine receptor CXCR3 is degraded following internalization and is replenished at the cell surface by de novo synthesis of receptor
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DOI：
10.4049/jimmunol.180.10.6713
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发表时间：
2008-05-15
影响因子：
4.4
通讯作者：
Pease, James E.
中科院分区：
文献类型：
--
作者：
Meiser, Andrea;Mueller, Ania;Pease, James E.
趋化因子受体CXCR3在静息和活化的T淋巴细胞表面均有表达。在这项研究中，我们描述了CXCR3利用T淋巴细胞和CXCR3转染体的内吞作用。趋化因子诱导的CXCR3下调以剂量依赖的方式快速发生，CXCL11是最有效和最有效的配体。内吞作用部分是由阻滞素介导的，但似乎独立于网状蛋白和小窝发生。与其他趋化因子受体在一小时内大部分回收到细胞表面不同，CXCR3的细胞表面补充发生在几个小时内，依赖于mRNA转录、从头蛋白质合成以及通过内质网和高尔基体的运输。共聚焦显微镜和Western blotting证实了内吞的CXCR3的命运是被降解的，部分地由溶酶体和蛋白酶体介导。CXCR3 C末端的定点突变表明，内化和降解不依赖于磷酸化、泛素化或保守的LL基序。CXCR3被发现在没有配体的情况下能够有效地内化，这一过程涉及C末端的YXXL基序。虽然新鲜分离的T淋巴细胞表达中等水平的CXCR3，但它们只对CXCL11有反应，而CXCL9和CXCL10只对激活的T淋巴细胞有显著的活性。因此，CXCR3的活性在mRNA翻译后受到严格控制。由于CXCR3(+)细胞本身是干扰素-γ的来源，而干扰素-γ可有效地诱导CXCR3配体的表达，因此对CXCR3的严格调控可以作为一种控制，以避免激活的T淋巴细胞募集的不必要放大。
The chemokine receptor CXCR3 is expressed on the surface of both resting and activated T lymphocytes. We describe in this study the endocytosis of CXCR3 using T lymphocytes and CXCR3 transfectants. Chemokine-induced CXCR3 down-regulation occurred in a rapid, dose-dependent manner, with CXCL11 the most potent and efficacious ligand. Endocytosis was mediated in part by arrestins, but appeared to occur independently of clathrin and caveolae. In contrast to other chemokine receptors, which are largely recycled to the cell surface within an hour, cell surface replenishment of CXCR3 occurred over several hours and was dependent upon mRNA transcription, de novo protein synthesis, and transport through the endoplasmic reticulum and Golgi. Confocal microscopy and Western blotting confirmed the fate of endocytosed CXCR3 to be degradation, mediated in part by lysosomes and proteosomes. Site-directed mutagenesis of the CXCR3 C terminus revealed that internalization and degradation were independent of phosphorylation, ubiquitination, or a conserved LL motif. CXCR3 was found to be efficiently internalized in the absence of ligand, a process involving a YXXL motif at the extreme of the C terminus. Although freshly isolated T lymphocytes expressed moderate cell surface levels of CXCR3, they were only responsive to CXCL11 with CXCL9 and CXCL10 only having significant activity on activated T lymphocytes. Thus, the activities of CXCR3 are tightly controlled following mRNA translation. Because CXCR3(+) cells are themselves a source of IFN-gamma, which potently induces the expression of CXCR3 ligands, such tight regulation of CXCR3 may serve as a control to avoid the unnecessary amplification of activated T lymphocyte recruitment.