Association of Lyn tyrosine kinase to the GM-CSF and IL-3 receptor common βc subunit and role of Src tyrosine kinases in DNA synthesis and anti-apoptosis

Background: After GM-CSF or IL-3 stimulation, the activation of JAK2 tyrosine kinase and members of the Src family of tyrosine kinases takes place, followed by phosphorylation of beta c tyrosine residues and the recruitment of SH2 containing molecules to the receptor complex. The exact role of Src kinases such as Lyn in this and other downstream signal transduction events remains unclear. Results: We investigated the association of Lyn kinase with beta c using synthetic peptides derived from the eight beta c tyrosine residues and the Box 1 motif. We found that Lyn kinase GST fusion proteins bind to peptides corresponding to the membrane proximal region of beta c and to peptides containing specific beta c derived phosphorylated tyrosine residues. We also determined that beta c tyrosine residues Y1,2 as well as Y7 and Y8 can act as substrates of Lyn. We further analysed the role of the Src kinases in DNA synthesis and anti-apoptosis downstream of GM-CSF by using the Src kinase inhibitor PP1 in murine BA/F3 cells stably expressing a series of mutant beta c receptors. Conclusions: Lyn binds to beta c derived peptides through multiple interactions, and may play an important role in beta c phosphorylation. Src family kinases also play an essential role in GM-CSF mediated DNA synthesis, as well as an important role in anti-apoptosis in response to GM-CSF.