Immediately after dimerization of CSF1R, tyrosine-561 is the first CSF1R tyrosine residue to be phosphorylated during a first wave of phosphorylation (inferred from the mouse homolog). The phosphorylation is catalyzed by CSF1R itself as one subunit of the CSF1R dimer phosphorylates the other subunit (inferred from the mouse homolog). Unphosphorylated tyrosine-561 inhibits the kinase activity of CSF1R. Phosphorylation causes a conformational change that relieves the inhibition and allows CSF1R to phosphorylate further targets (inferred from mouse homologs). Phosphorylated tyrosine-561 is also required for subsequent binding of Src family kinases to CSF1R and activation of the CBL ubiquitin ligase (inferred from mouse homologs). GRB2 subsequently binds phosphotyrosine-699 and CBL subsequently binds phosphotyrosine-969 so these tyrosine residues may also be phosphorylated at this time (inferred from mouse homologs). However, the CSF1R-mediated activation of CBL is not dependent on phosphorylation of tyrosine-969, suggesting that phosphotyrosine-969 binding of CBL may mediate other, ubiquitin ligase-independent effects of CBL (inferred from mouse homologs).