Phosphorylated JAK2 phosphorylates VAV1 bound to GRB2 in a large complex assembled on the phosphorylated EPOR (Odai et al. 1997, Shigematsu et al. 1997). Phosphorylation of VAV1 activates its guanine nucleotide exchange activity (inferred from the mouse homolog).
protein tyrosine kinase activity of EPO:p-8Y-EPOR:p-12Y-JAK2:LYN:IRS2:p-CRKL:RAPGEF1:p-Y-SHC1:GRB2:VAV1 [plasma membrane]