Feline McDonough Sarcoma-like tyrosine kinase (Flt3) is a member of the class III tyrosine kinase receptor family. Ligand binding induces conformational changes in the Flt3 receptor, which facilitates its dimerization and autophosphorylation. Once fully active, Flt3 receptors can associate with growth factor receptor-bound protein 2 (Grb2), which then recruits Grb2-associated-binding protein 2 (Gab2). Consequently, Gab2 is phosphorylated (Zhang et al. 2000, Masson et al. 2009, Chonabayashi et al. 2013). The precise phosphorylation mechanism of Gab2 is unclear.