The kinases JAK2 (Shimoda et al. 1997, Marino and Roguin 2008), TYK2 (Shimoda et al. 1997, Marino and Roguin 2008), HCK, and SYK (Kasper et al. 1999) bind phosphorylated tyrosine residues of the cytosolic domain of CSF3R and are activated by phosphorylation (also inferred from mouse homologs). The order of their binding and the kinases responsible for their phosphorylation are incompletely characterized.