Droese Jana, Mokros Thilo, Hermosilla Ricardo, Schülein Ralf, Lipp Martin, Höpken Uta E, Rehm Armin
Department of Hematology, Oncology, and Tumor Immunology, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
Biochem Biophys Res Commun. 2004 Sep 10;322(1):42-9. doi: 10.1016/j.bbrc.2004.07.076.
The human cytomegalovirus-encoded G protein-coupled receptor homologue US28 binds inflammatory chemokines and sequesters them from the environment of infected cells. Low surface deposition and endocytosis are dependent on constitutive C-terminal phosphorylation, suggesting a requirement for beta-arrestin binding in receptor internalization. In this report, a US28-dependent redistribution of beta-arrestin into vesicular structures occurred, although internalization of US28 was independent of beta-arrestin. Internalization of US28 was dynamin-dependent, and US28 partially partitioned into the detergent-resistant membrane fraction. Endocytosis was diminished by cholesterol depletion, yet sucrose inhibition was even stronger. The relevance of the clathrin-coated pit pathway was supported by colocalization of beta(2)-adaptin and US28 in endocytic compartments. Exchange of the C-terminal dileucine endocytosis motif inhibited rapid endocytosis, indicating a direct interaction of US28 with the AP-2 adaptor complex. We suggest that the arrestin-independent, dynamin-dependent internalization of US28 reveals a differential sorting of beta-arrestins and the virally encoded chemokine receptor homologue.
人巨细胞病毒编码的G蛋白偶联受体同源物US28可结合炎性趋化因子，并将它们与受感染细胞的环境隔离开来。低水平的表面沉积和内吞作用依赖于组成性的C末端磷酸化，这表明在受体内化过程中需要β抑制蛋白结合。在本报告中，尽管US28的内化不依赖于β抑制蛋白，但β抑制蛋白仍会发生依赖于US28的重新分布并进入囊泡结构。US28的内化依赖于发动蛋白，并且US28部分地分配到抗去污剂膜组分中。胆固醇耗竭会减少内吞作用，但蔗糖抑制作用更强。β(2)-衔接蛋白与US28在内吞区室中共定位，这支持了网格蛋白包被小窝途径的相关性。C末端双亮氨酸内吞基序的交换抑制了快速内吞作用，表明US28与AP-2衔接蛋白复合物存在直接相互作用。我们认为，US28不依赖抑制蛋白、依赖发动蛋白的内化揭示了β抑制蛋白与病毒编码的趋化因子受体同源物的差异分选。
