Possible role of gangliosides in the interaction of colony-stimulating factor with granulocyte-macrophage progenitor cells.

Our previous studies have shown that preincubation of murine bone marrow (BM) cells with cholera toxin (CT) or with its B subunit inhibited their responsiveness to colony-stimulating factor (CSF). Because ganglioside GM1 is a component of the CT receptor, the present study was undertaken to determine whether gangliosides interact with CSF and therefore might play a role in the binding sites for CSF. Preincubation of CSF with increasing concentrations of bovine-brain mixed gangliosides resulted in decreased numbers of colonies of BM-derived granulocyte-macrophage progenitor cells (CFU-C) in soft agar. The inhibitory effect of the gangliosides could be reduced by increasing the concentrations of CSF. Evidence for direct binding of CSF to gangliosides was obtained by affinity chromatography of CSF on gangliosides-sepharose beads. CSF activity was retained on the beads and could be eluted with 6 M guanidine HCl. Four different individual gangliosides (GM1, GM2, GD1a, GT1b) were tested for their inhibitory effect on CSF-induced clonal growth of CFU-C. GM1 was the most effective with a 50% inhibition (I50) of clonal growth at a concentration of 15 microM. while the other three gangliosides had slight inhibitory activity (I50 at a concentration greater than 100 microM). In addition, preincubation of BM cells with rabbit anti-GM1 antibodies before addition of CSF reduced the clonal growth of CFU-C to 45%. These data indicate that GM1 interacts with CSF and suggest that gangliosides may play a role in the interaction of CSF with CFU-C and that the binding site for CSF on the surface of these cells might either consist of or contain this ganglioside.