Granulocyte macrophage-colony stimulating factor stimulates the synthesis of membrane and nuclear proteins in murine neutrophils.

Abstract

The effect of granulocyte macrophage-colony stimulating factor (GM-CSF), a well-characterized hemopoietic regulator, on protein synthesis in murine bone marrow neutrophils is described. Bone marrow neutrophils in excess of 95% purity were obtained by fluorescence-activated cell sorting. While GM-CSF did not appear to slow the rate of dying of peritoneal exudate neutorphils or thymus cells, the viability of bone marrow neutrophils after 17 hr was enhanced (40%) by GM-CSF. GM-CFS had no effect on total 35S-methionine incorporation by thymocytes or peritoneal exudate neutrophils over a 17-hr incubation period; however, bone marrow neutrophils showed increased incorporation (approximately 10%) at all times between 5-17 hr. As viability and 35S-methionine incorporation of bone marrow neutrophils at 5 hr were minimally affected by GM-CSF, this time point was chosen to study the effect of GM-CSF on the synthesis of particular proteins. Two-dimensional polyacrylamide gels of 35S-methionine-labelled lysates were prepared from whole cells, isolated nuclei, and membranes. Quantitative analysis of the fluorograms obtained from the two-dimensional electropherograms by a computer-linked optical data digitiser indicated that out of a total of 180 proteins, the amount of label contained in 11 proteins was significantly higher in the presence of GM-CSF, while three proteins, apparently of cytoplasmic origin, contained less label than control cells. Eight of these proteins were identified as nuclear, and one was membrane derived. Attempts have been made to identify some of the inducible proteins and to correlate results with other studies of normal hemopoietic and leukemic cells. The significance and multiple functions of GM-CSF in hemopoiesis are discussed.