IL-3 receptor dimerisation differentially regulates signalling by JAK-1, JAK-2 and Lyn tyrosine kinases

D Tvorogov1, T Hercus1, M Dottore1, H Ramshaw1, J Sandow2, A Webb2, M Parker3 and A Lopez1

  1. The Centre for Cancer Biology, Adelaide, South Australia, Australia
  2. The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
  3. Australian Cancer Research Foundation Rational Drug Discovery Centre, St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia

The IL-3 receptor signalling complex is a regulator of normal and malignant hemopoiesis and has also been implicated in several pathological activities outside of hemopoiesis. In hemopoietic cells IL-3 induces dimerisation of its receptor IL-3R and βc subunits and the formation of a high order complex, the structure of which we have recently solved. However, how the IL-3 receptor signals as it undergoes oligomerisation is poorly understood, as is the quality of the signalling and how it differs from the related GM-CSF receptor. Our laboratory is utilizing novel purification strategies using StrepTag and unique antibodies that have identified a distinct set of proteins and distinct interactions involved in IL-3 signalling. Proteomic analysis followed by validation experiments allowed us to: 1) revisit the role of JAK1 and JAK2 in IL-3-initiated signalling, which suggests distinct roles depending on hexameric or dodecameric receptor assembly; 2) identify a precise mechanism of SHP2 activation in response to IL-3 which involves not only JAK kinases but also IL-3Rα-associated Lyn kinase; 3) identify distinct docking sites in βc responsible for the interaction of SHP2 with the IL-3 receptor in vivo. This distinct JAK/SHP2/Lyn signalling pathway downstream of the IL-3 receptor complex may have important implications for certain types of leukaemia.