Stromal cell-derived factor-1 alpha and stem cell factor/kit ligand share signaling pathways in hemopoietic progenitors: a potential mechanism for cooperative induction of chemotaxis.
Stromal cell-derived factor (SDF-1alpha), the ligand for CXCR4, is a chemokine that acts as a potent chemoattractant for hemopoietic progenitor cells. Stem cell factor/kit ligand (SCF/KL), an early acting cytokine, has recently been reported to enhance the chemotaxis induced by SDF-1alpha. However, very little is known about downstream signaling events following these receptor-ligand interactions. To investigate these events, we utilized a model progenitor cell line, CTS, which expresses both the CXCR4 and c-kit receptors. We observed strong Ca2+ mobilization and enhancement of chemotaxis following treatment with SDF-1alpha or SCF/KL. A combination of these factors enhanced this chemotaxis in CTS cells as well as in CD34+ bone marrow cells. Prior treatment of CTS cells with pertussis toxin inhibited the SDF-1alpha-induced chemotaxis, suggesting that SDF-1alpha signaling involves a pertussis-sensitive Gi-coupled protein. SDF-1alpha treatment resulted in a rapid phosphorylation of the focal adhesion molecules RAFTK (related adhesion focal tyrosine kinase), paxillin, and p130cas, which then declined within minutes. SCF/KL alone or in combination with SDF-1alpha induced a rapid and sustained effect on phosphorylation of these substrates. SDF-1alpha treatment resulted in a rapid and robust activation of p44/42 mitogen-activated protein kinase compared with the relatively weak and delayed effect of SCF/KL treatment. Interestingly, a delayed but sustained activation of mitogen-activated protein kinase activation was observed when the factors were used in combination. Such cooperativity in downstream signaling pathways may explain the enhanced chemotaxis of progenitors observed with SDF-1alpha in combination with SCF/KL.
Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
P
P
Dutt
J F
JF
Wang
J E
JE
Groopman
D018952:Antigens, CD34 / Q000032:analysis; D001854:Bone Marrow Cells / Q000276:immunology / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000502:physiology*; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000276:immunology / Q000502:physiology*; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D051418:Focal Adhesion Kinase 2; D006412:Hematopoietic Stem Cells / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D008565:Membrane Proteins / Q000032:analysis; D020928:Mitogen-Activated Protein Kinases; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins; D050717:Retinoblastoma-Like Protein p130; D015398:Signal Transduction / Q000276:immunology / Q000502:physiology*; D019089:Stem Cell Factor / Q000502:physiology*; D014443:Tyrosine / Q000187:drug effects / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D018952:Antigens, CD34; C493841:BCAR1 protein, human; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D050719:Crk-Associated Substrate Protein; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; D011506:Proteins; D050717:Retinoblastoma-Like Protein p130; D019089:Stem Cell Factor; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium