Distinct Regions of the Granulocyte Colony-Stimulating Factor Receptor Are Required for Tyrosine Phosphorylation of the Signaling Molecules JAK2, Stat3, and p42, p44MAPK

Abstract

The protein tyrosine kinases JAK1 and JAK2 are phosphorylated on tyrosine after the interaction of granulocyte colony-stimulating factor (G-CSF) with its transmembrane receptor. So too is Stat3, a member of the STAT family of transcriptional activators thought to be activated by the JAK kinases. Truncated G-CSF receptor (G-CSF-R) mutants were used to determine the different regions of the cytoplasmic domain necessary for tyrosine phosphorylation of the signaling molecules JAK2, Stat3, and p42, p44MAPK. We have shown that G-CSF-induced tyrosine phosphorylation and kinase activation of JAK2 requires the membrane proximal 57 amino acids of the cytoplasmic domain. In contrast, maximal Stat3 tyro..