Activation of HIV-1 coreceptor (CXCR4) mediates myelosuppression

Chemokines are cytokines that activate and induce the migration of leukocytes. Stroma-derived factor-1 (SDF-1) is a novel chemokine that blocks the entry of T-tropic HIV-1 mediated by fusin/CXCR4/LESTR (leukocyte-derived seven-transmembrane domain receptor). In this work we demonstrate that SDF-1 triggers increases in intracellular calcium and inhibits the proliferation of myeloid progenitor cell line 32D. By contrast, SDF-1 neither triggers a calcium response nor affects the proliferation of the myeloid progenitor cell line 32D-GR that is deficient in CXCR4. Responsiveness to SDF-1 was rescued by transfection of 32D-GR cells with a cDNA encoding the human CXCR4. The data indicate that SDF-1 induces myelosuppression by activation of CXCR4. The constitutive production of SDF-1 by bone marrow stromal cells argues for a major role of SDF-1 on the regulation of myelopoiesis.