Stem cell factor prevents Fas-mediated apoptosis of human erythroid precursor cells with Src-family kinase dependency.
The Fas ligand (Fas-L) expressed on mature erythroblasts may induce apoptosis of more immature erythroid cells that express Fas, whereas stem cell factor (SCF) may prevent Fas-mediated cell death in hematopoietic progenitor cells. The manner in which SCF prevents Fas-mediated cell death still is unclear. Given the essential role of SCF and the potentially important involvement of the Fas/Fas-L system in the development of erythrocytes, we studied mechanisms related to SCF prevention of Fas-mediated apoptosis. We used primary cultured human erythroid colony-forming cells (ECFC) derived from CD34+ cells and enriched glycophorin A positive (GPA+) c-kit+ cells in ECFC. Apoptosis of ECFC was induced by an Fas-L mimetic monoclonal antibody CH11. DNA fragmentation and the activation of caspase-3 and caspase-8 were measured using commercially available kits. Characterization of expanded cells was performed using multiparameter flow cytometry. Lyn kinase activity was measured by enolase kinase assays. SCF inhibited the CH11-induced DNA fragmentation of ECFC as well as enriched GPA+ c-kit+ cells in ECFC, but not those of GPA+ c-kit- cells. SCF also inhibited the activation of caspase-3 and caspase-8, without downregulation of the surface expression of Fas, suggesting that SCF prevents apoptosis through uncoupling of Fas ligation from subsequent caspase activation. PP2, a specific inhibitor of Src-family kinases, antagonized the effects of SCF in preventing Fas-mediated apoptosis. We propose that SCF prevents Fas-mediated apoptosis of erythroid progenitor cells in a manner dependent on the activity of Src-family tyrosine kinases. We also identified active Lyn in erythroid cells. These data suggest the presence of a novel Src-family-dependent function of SCF in the development of erythrocytes.
Nishio
M
M
Department of Internal Medicine II, Hokkaido University School of Medicine, N-15, W-7, Kita-ku, Sapporo 060-8638, Japan.
Oda
A
A
Koizumi
K
K
Satoh
I
I
Sato
Y
Y
Endoh
T
T
Tsutsumi
A
A
Fujihara
M
M
Ikebuchi
K
K
Ikeda
H
H
Koike
T
T
Sawada
K I
KI
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D053938:DNA Fragmentation; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D004920:Erythropoiesis / Q000187:drug effects / Q000502:physiology*; D004921:Erythropoietin / Q000494:pharmacology; D053222:Fas Ligand Protein; D000069585:Filgrastim; D005434:Flow Cytometry; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000276:immunology / Q000502:physiology*; D011994:Recombinant Proteins; D019089:Stem Cell Factor / Q000494:pharmacology*; D019014:fas Receptor / Q000502:physiology*; D019061:src-Family Kinases / Q000502:physiology*
D000911:Antibodies, Monoclonal; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D007377:Interleukin-3; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D019014:fas Receptor; D004921:Erythropoietin; D016179:Granulocyte Colony-Stimulating Factor; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D000069585:Filgrastim