SHP1 and SHP2 protein-tyrosine phosphatases associate with beta c after interleukin-3-induced receptor tyrosine phosphorylation - Identification of potential binding sites and substrates

The cytoplasmic tyrosine phosphatases, SHP1 and SHP2, are implicated in the control of cellular proliferation and survival. Here we demonstrate that both SHP1 and SHP2 associate with the beta c subunit of the human interleukin-3 (IL-3) receptor following IL-3 stimulation and that the src homology region 2 (SH2) domains of these phosphatases mediate this interaction. Sequential immunoprecipitation analyses suggest this interaction is direct. Competition studies, using phosphotyrosine-containing peptides based on sequences surrounding key tyrosine residues within beta c, suggest that phosphorylation of tyrosine 612 is the key event mediating the association of beta c with SHP1 and SHP2. However, inhibition of SHP2 binding to beta c, did not prevent tyrosine phosphorylation of SHP2. interestingly, this same phosphopeptide served as a substrate for the tyrosine phosphatase activity of both SHP1 and SHP2. Binding of these protein-tyrosine phosphatases to the IL-3 receptor may regulate IL-3 signal transduction pathways, both through their catalytic activity and through the recruitment of other molecules to the receptor complex.