Intracellular localization and constitutive endocytosis of CXCR4 in human CD34+ hematopoietic progenitor cells

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / biosynthesis
  • Antigens, CD34 / biosynthesis*
  • Cell Membrane / metabolism
  • Cell Movement
  • Chemotaxis
  • Clathrin / metabolism
  • Endocytosis
  • Flow Cytometry
  • Gene Expression Regulation
  • Green Fluorescent Proteins / metabolism
  • Hematopoietic Stem Cells / cytology*
  • Hematopoietic Stem Cells / metabolism
  • Humans
  • Ligands
  • Lysosomal Membrane Proteins
  • Membrane Proteins / biosynthesis
  • Microscopy, Confocal
  • Plasmids / metabolism
  • Platelet Membrane Glycoproteins / biosynthesis
  • Receptors, CXCR4 / biosynthesis*
  • Retroviridae / genetics
  • Signal Transduction
  • Temperature
  • Tetraspanin 30
  • Vesicular Transport Proteins
  • rab GTP-Binding Proteins / biosynthesis
  • rab4 GTP-Binding Proteins / biosynthesis
  • rab5 GTP-Binding Proteins / biosynthesis


  • Antigens, CD
  • Antigens, CD34
  • CD63 protein, human
  • Clathrin
  • Ligands
  • Lysosomal Membrane Proteins
  • Membrane Proteins
  • Platelet Membrane Glycoproteins
  • Receptors, CXCR4
  • Tetraspanin 30
  • Vesicular Transport Proteins
  • early endosome antigen 1
  • Green Fluorescent Proteins
  • rab11 protein
  • rab GTP-Binding Proteins
  • rab4 GTP-Binding Proteins
  • rab5 GTP-Binding Proteins