title: Opposing effects of engagement of integrins and stimulation of cytokine receptors on cell cycle progression of normal human hematopoietic progenitors.
abstract: We evaluated the effect of beta1-integrin receptor engagement on the expression and activity of cell cycle regulatory proteins in CD34(+) cells under conditions that mimic the steady-state marrow microenvironment and in the presence of supraphysiological concentrations of interleukin-3 (IL3) and stem cell factor (SCF). Adhesion of CD34(+) progenitors to fibronectin (FN) was similar whether IL3 or SCF was present or absent. Engagement of beta1-integrins blocked S-phase entry of CD34(+) cells in the absence of IL3 or SCF, whereas addition of 10 ng/mL IL3 or SCF prevented such a block in S-phase entry. In the absence of IL3 or SCF, cyclin-E levels were significantly lower and p27(KIP1) levels significantly higher in FN-adherent than in FN-nonadherent cells, or than in poly-L-lysine (PLL)-adherent or (PLL)-nonadherent cells. Cyclin-dependent-kinase (cdk)-2 activity was decreased and levels of cyclin-E-cdk2 complexes were lower in FN-adherent than in PLL-adherent cells. In contrast, cyclin-E and p27(KIP1) protein levels and cdk2 activity in cells adherent to FN in the presence of IL3 or SCF were similar to those in PLL-adherent and FN-nonadherent or PLL-nonadherent cells. In conclusion, under physiological cytokine conditions, integrin engagement prevents S-phase entrance of CD34(+) cells, which is associated with elevated levels of the contact-dependent cyclin kinase inhibitor p27(KIP1). Supraphysiological concentrations of IL3 or SCF prevent p27(KIP1) elevation and override the integrin-mediated inhibition of entry into S phase.
authors.affiliation: Stem Cell Laboratory and Division of Hematology, Oncology and Transplantation, Department of Medicine and Cancer Center, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Jiang
authors.forename: F
authors.initials: F
authors.lastname: Prosper
authors.forename: C M
authors.initials: CM
authors.lastname: Verfaillie
mesh_terms: D042846:CDC2-CDC28 Kinases; D002448:Cell Adhesion; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000502:physiology; D005353:Fibronectins / Q000502:physiology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006410:Hematopoiesis / Q000187:drug effects; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D019012:Integrin beta1 / Q000502:physiology*; D007377:Interleukin-3 / Q000494:pharmacology; D008565:Membrane Proteins / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D018121:Receptors, Cytokine / Q000502:physiology*; D016196:S Phase / Q000502:physiology; D019089:Stem Cell Factor / Q000494:pharmacology; D025521:Tumor Suppressor Proteins
chemical_list: D018797:Cell Cycle Proteins; D005353:Fibronectins; D019012:Integrin beta1; D007377:Interleukin-3; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D018121:Receptors, Cytokine; D019089:Stem Cell Factor; D025521:Tumor Suppressor Proteins; C084881:flt3 ligand protein; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases