Erythropoietin induces tyrosine phosphorylation of the beta chain of the GM-CSF receptor.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and erythropoietin (EPO) induce tyrosine phosphorylation of the GM-CSF receptor beta chain and the EPO receptor, respectively, although their receptors lack the tyrosine kinase activity. We have shown that EPO as well as GM-CSF induces tyrosine phosphorylation of the beta chain. Conversely, GM-CSF does not induce tyrosine phosphorylation of the EPO receptor. Tyrosine phosphorylation of the beta chain by stimulation with EPO is rapid and transient. EPO may trans-modulate a signaling pathway of GM-CSF by phosphorylating the beta chain of the GM-CSF receptor.