Alpha 4 beta 1 and alpha 5 beta 1 are differentially expressed during myelopoiesis and mediate the adherence of human CD34+ cells to fibronectin in an activation-dependent way.
To study the receptors involved in the interaction between extracellular matrix proteins and hematopoietic progenitor cells, we analyzed the expression of beta 1 integrins on CD34+ bone marrow cells by means of immunoflowcytometry. Alpha 4 beta 1 and alpha 5 beta 1 were expressed, whereas alpha 1 beta 1, alpha 2 beta 1, alpha 3 beta 1, alpha 6 beta 1, and alpha v beta 1 were virtually absent. Furthermore, we assessed the alpha 4 and alpha 5 expression on committed myeloid progenitor cells. These colony-forming cells were detected in the alpha 4 dull fraction and the alpha 5 dull fraction. During myeloid differentiation, both in vivo and in vitro, a differential expression of alpha 4 beta 1 and alpha 5 beta 1 was observed. alpha 5 beta 1 was found to be lost at the myelocytic-metamyelocytic stage, before the loss of alpha 4 beta 1, at the band stage. Functional studies showed no binding of erythroid progenitor-depleted, CD34+ bone marrow cells to fibronectin. However, protein kinase C activation strongly induced fibronectin binding (68% of the cells). Inhibition experiments with specific antibodies and peptides showed the binding to be mediated by both alpha 4 beta 1 and alpha 5 beta 1. Also, colony-forming cells of granulocytes and macrophages were demonstrated to adhere to fibronectin in an activation-dependent way. During granulocyte colony-stimulating factor-induced in vitro maturation, the activation-dependent fibronectin binding capacity is gradually lost. We conclude that: (1) CD34+ bone marrow cells express alpha 4 beta 1 and alpha 5 beta 1; (2) the expression of alpha 4 beta 1 and alpha 5 beta 1 is differentially expressed during myeloid differentiation; and (3) binding of CD34+ bone marrow cells to fibronectin is activation dependent.
Kerst
J M
JM
Central Laboratory, Red Cross Blood Transfusion Service, Amsterdam, The Netherlands.
Sanders
J B
JB
Slaper-Cortenbach
I C
IC
Doorakkers
M C
MC
Hooibrink
B
B
van Oers
R H
RH
von dem Borne
A E
AE
van der Schoot
C E
CE
D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000032:analysis* / Q000502:physiology*; D018952:Antigens, CD34; D001853:Bone Marrow / Q000502:physiology*; D001854:Bone Marrow Cells; D002448:Cell Adhesion / Q000187:drug effects; D003114:Colony-Forming Units Assay; D005353:Fibronectins / Q000378:metabolism*; D006684:HLA-DR Antigens / Q000032:analysis; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology / Q000502:physiology*; D006801:Humans; D016023:Integrins / Q000276:immunology / Q000502:physiology*; D012016:Reference Values; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018952:Antigens, CD34; D005353:Fibronectins; D006684:HLA-DR Antigens; D016023:Integrins; D013755:Tetradecanoylphorbol Acetate