The related adhesion focal tyrosine kinase (RAFTK) is tyrosine phosphorylated and participates in colony-stimulating factor-1/macrophage colony-stimulating factor signaling in monocyte-macrophages.
RAFTK, a novel nonreceptor protein kinase, has been shown to be involved in focal adhesion signal transduction pathways in neuronal PC12 cells, megakaryocytes, platelets, and T cells. Because focal adhesions may modulate cytoskeletal functions and thereby alter phagocytosis, cell migration, and adhesion in monocyte-macrophages, we investigated the role of RAFTK signaling in these cells. RAFTK was abundantly expressed in THP1 monocytic cells as well as in primary alveolar and peripheral blood-derived macrophages. Colony-stimulating factor-1 (CSF-1)/macrophage colony-stimulating factor (M-CSF) stimulation of THP1 cells increased the tyrosine phosphorylation of RAFTK; similar increases in phosphorylation were also detected after lipopolysaccharide stimulation. RAFTK was phosphorylated with similar kinetics in THP1 cells and peripheral blood-derived macrophages. Immunoprecipitation analysis showed associations between RAFTK and the signaling molecule phosphatidylinositol-3 (PI-3) kinase. PI-3 kinase enzyme activity also coprecipitated with the RAFTK antibody, further confirming this association. The CSF-1/M-CSF receptor c-fms and RAFTK appeared to associate in response to CSF-1/M-CSF treatment of THP1 cells. Inhibition of RAFTK by a dominant-negative kinase mutant reduced CSF-1/M-CSF-induced MAPK activity. These data indicate that RAFTK participates in signal transduction pathways mediated by CSF-1/M-CSF, a cytokine that regulates monocyte-macrophage growth and function.
Hatch
W C
WC
Divisions of Experimental Medicine and Hematology/Oncology, Harvard Institutes of Medicine, Harvard Medical School, Boston, MA, USA.
Ganju
R K
RK
Hiregowdara
D
D
Avraham
S
S
Groopman
J E
JE
D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D051418:Focal Adhesion Kinase 2; D006801:Humans; D007948:Leukemia, Monocytic, Acute / Q000473:pathology; D008070:Lipopolysaccharides / Q000494:pharmacology; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000201:enzymology; D009000:Monocytes / Q000187:drug effects* / Q000201:enzymology; D009363:Neoplasm Proteins / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014407:Tumor Cells, Cultured / Q000187:drug effects
D008070:Lipopolysaccharides; D009363:Neoplasm Proteins; D016173:Macrophage Colony-Stimulating Factor; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D016186:Receptor, Macrophage Colony-Stimulating Factor; D051418:Focal Adhesion Kinase 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases