HEMATOPOIETIC COLONY-STIMULATING FACTORS CSF-1 AND GM-CSF INCREASE PHOSPHATIDYLINOSITOL 3-KINASE ACTIVITY IN MURINE BONE-MARROW-DERIVED MACROPHAGES

The activity of phosphatidylinositol (PI) 3-kinase was examined in mur ine bone marrow-derived macrophages (BMM) stimulated with the haematop oietic growth factors colony stimulating factor-1 (CSF-1) and granuloc yte/macrophage-CSF (GM-CSF). PI 3-kinase was immunoprecipitated from c ell lysates using anti-phosphotyrosine antibody or an antibody directe d against the 85K subunit of PI S-kinase, and the activity assayed by the phosphorylation of PI in the presence of [gamma(32)P]-ATP. The res ults demonstrate that CSF-1 increases the activity of PI 3-kinase, as compared to the non-stimulated control, in murine macrophages. Maximum activity was seen after 10 min of stimulation with CSF-1 at 3000-5000 U/ml. The dose-response of CSF-1 is consistent with other biochemical effects of CSF-1 seen in the BMM. GM-CSF also stimulated PI 3-kinase activity although to a lesser extent than CSF-1, correlating well with their degree of mitogenic activity on the BMM. Non-mitogenic macropha ge activating agents, such as the phorbol myristate acetate, lipopolys accharide, concanavalin A and formyl-methionyl-leucyl-phenylalanine, d id not significantly increase the PI 3-kinase activity. Furthermore, C SF-1 failed to stimulate PI 3-kinase activity in resident peritoneal m acrophages, a population of macrophages with poor proliferative capaci ty. These results suggest that the PI 3-kinase activity may be involve d in the haemopoietic growth factor signalling pathways regulating mac rophage growth.