Zhang Yanyan, Foudi Adlen, Geay Jean-François, Berthebaud Magali, Buet Dorothée, Jarrier Peggy, Jalil Abdelali, Vainchenker William, Louache Fawzia
INSERM U362, Institut Gustave Roussy, PR1, 39 Rue Camille Desmoulins, 94805 Villejuif, France.
Stem Cells. 2004;22(6):1015-29. doi: 10.1634/stemcells.22-6-1015.
CXCR4, the stromal cell-derived factor-1 receptor, plays an important role in the migration of hematopoietic progenitor/stem cells. The surface and cytoplasmic expression of CXCR4 on human hematopoietic CD34(+) cells was investigated. We show that its surface expression is low, whereas a large part of CXCR4 protein is sequestered intracellularly. Using confocal microscopy, we demonstrated that CXCR4 is colocalized with EEA-1, Rab5, Rab4, and Rab11, which are localized in early and recycling endosomes. No significant colocalization of CXCR4 with lysosomal markers CD63 and Lamp-1 was detected. Using antibody feeding experiments, we report a role for CXCR4 constitutive endocytosis in subcellular localization in stably transduced UT7-CXCR4-GFP and CD34(+) cells. Agonist-independent endocytosis of CXCR4 occurs through clathrin-coated vesicles. These data implicate a constitutive endocytosis in the regulation of CXCR4 membrane expression and suggest that constitutive endocytosis may be involved in the regulation of trafficking the human hematopoietic progenitor/stem cells to and in the bone marrow microenvironment.
CXCR4是基质细胞衍生因子-1受体，在造血祖细胞/干细胞迁移中起重要作用。研究了CXCR4在人造血CD34(+)细胞上的表面和细胞质表达。我们发现其表面表达较低，而大部分CXCR4蛋白被隔离在细胞内。利用共聚焦显微镜，我们证明CXCR4与定位于早期和循环内体的EEA-1、Rab5、Rab4和Rab11共定位。未检测到CXCR4与溶酶体标记物CD63和Lamp-1的明显共定位。通过抗体摄取实验，我们报道了CXCR4组成型内吞作用在稳定转导的UT7-CXCR4-GFP和CD34(+)细胞亚细胞定位中的作用。CXCR4的非激动剂依赖性内吞作用通过网格蛋白包被小泡发生。这些数据表明组成型内吞作用参与CXCR4膜表达的调节，并提示组成型内吞作用可能参与调控人造血祖细胞/干细胞向骨髓微环境的转运及其在骨髓微环境中的活动。
