title: Reduced activation of protein kinase B, Rac, and F-actin polymerization contributes to an impairment of stromal cell derived factor-1 induced migration of CD34+ cells from patients with myelodysplasia.
abstract: Patients with myelodysplasia (MDS) show a differentiation defect in the multipotent stem-cell compartment. An important factor in stem-cell differentiation is their proper localization within the bone marrow microenvironment, which is regulated by stromal cell-derived factor (SDF-1). We now show that SDF-1-induced migration of CD34(+) progenitor cells from MDS patients is severely impaired. In addition, these cells show a reduced capacity to polymerize F-actin in response to SDF-1. We demonstrate a major role for Rac and phosphatidylinositol 3-kinase (PI3K) and a minor role for the extracellular signal-regulated kinase (ERK)1/2 signaling pathway in SDF-1-induced migration of normal CD34(+) cells. Furthermore, SDF-1-stimulated activation of Rac and the PI3K target protein kinase B is impaired in CD34(+) cells from MDS patients. Lentiviral transduction of MDS CD34(+) cells with constitutive active Rac1V12 results in a partial restoration of F-actin polymerization in response to SDF-1. In addition, expression of constitutive active Rac increases the motility of MDS CD34(+) cells in the absence of SDF-1, although the directional migration of cells toward this chemoattractant is not affected. Taken together, our results show a reduced migration of MDS CD34(+) cells toward SDF-1, as a result of impaired activation of the PI3K and Rac pathways and a decreased F-actin polymerization.
authors: Division of Hematology, Department of Medicine, University Medical Center Groningen, Groningen, The Netherlands.
authors: Gwenny M
authors: GM
authors: Fuhler
authors: A Lyndsay
authors: AL
authors: Drayer
authors: Sandra G M
authors: SG
authors: Olthof
authors: Jan Jacob
authors: JJ
authors: Schuringa
authors: Paul J
authors: PJ
authors: Coffer
authors: Edo
authors: E
authors: Vellenga
mesh_terms: D000199:Actins / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018952:Antigens, CD34 / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D054377:Chemokine CXCL12 / Q000378:metabolism* / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009436:Neural Tube Defects / Q000378:metabolism* / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011108:Polymers / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D018952:Antigens, CD34; D054377:Chemokine CXCL12; D011108:Polymers; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins