Unidirectional cross-phosphorylation between the granulocyte colony-stimulating factor and interleukin 3 receptors

The mouse interleukin-3 (IL-3)-dependent hemopoietic precursor cell line 32DC13 responds to granulocyte colony-stimulating factor (G-CSF) for proliferation and differentiation. We established a subline (32D-FH) of the 32DC13 cells which has lost the ability to respond to G-CSF. When murine G-CSF receptor cDNA was introduced into the 32D-FH cell line, the transformants responded to G-CSF as well as to IL-3 for proliferation. Adding G-CSF to the transformants rapidly induced tyrosine phosphorylation not only of the G-CSF receptor but also of both subtypes of the IL-3 receptor beta-chain (AIC2A and AIC2B molecules). On the other hand, stimulation of the transformants with IL-3 induced tyrosine phosphorylation of the AIC2A and AIC2B but not of the G-CSF receptor. These results indicate that the tyrosine kinase activated through the G-CSF receptor interacts with the IL-3 receptor beta-chains but not vice versa. This unidirectional cross-phosphorylation between the G-CSF and IL-3 receptors may play a role in granulopoiesis induced by G-CSF.