| Marginal expression of CXCR4 on c-kit(+)Sca-1 (+)Lineage (-) hematopoietic stem/progenitor cells. Int J Hematol. 2009 Dec;90(5):553-60 Authors: Sasaki Y, Matsuoka Y, Hase M, Toyohara T, Murakami M, Takahashi M, Nakatsuka R, Uemura Y, Sonoda Y Stromal cell-derived factor 1 (SDF-1) and its receptor CXCR4 are the key regulatory molecules of hematopoietic stem cell (HSC) migration and engraftment to the bone marrow (BM! ) microenvironment. However, the significance of the ligand-receptor complex on HSC in steady-state BM is not clear. There is currently a lack of information as to how CXCR4 is expressed on HSCs. We herein demonstrate that c-kit(+)Sca-1(+)Lineage(-) (KSL) cells freshly isolated from BM expressed very low to undetectable levels of CXCR4. Two hours of incubation at 37 degrees C quickly up-modulated the receptor expression on KSL cells. Protein synthesis was not required for this early stage up-regulation, thus suggesting the emergence of intracellularly pooled receptors to the cell surface. However, protein synthesis was involved at the later stage of up-regulation. The up-regulated CXCR4 was functional, as evidenced by the fact that the incubated KSL cells more efficiently migrated to the SDF-1 gradient in vitro. Therefore, although KSL cells are able to express functional CXCR4, the receptors are only marginally expressed in the steady-state BM microenvironment. These obser! vations therefore indicate the limited role of the SDF-1-CXCR4! axis on HSC functionality in a static BM environment. PMID: 19937482 [PubMed - indexed for MEDLINE] | 
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