Analysis of Interleukin-2-dependent Signal Transduction through the Shc/Grb2 Adapter Pathway: INTERLEUKIN-2-DEPENDENT MITOGENESIS DOES NOT REQUIRE Shc PHOSPHORYLATION OR RECEPTOR ASSOCIATION
Journal of Biological Chemistry
The interleukin (IL)-2 receptor system has previously been shown to signal through the association and tyrosine phosphorylation of Shc. This study demonstrates that the IL-2 receptor ␤ (IL-2R␤) chain is the critical receptor component required to mediate this effect. The use of IL-2R␤ chain deletion mutants transfected into a Ba/F3 murine cell model describes a requirement for the IL-2R␤ "acid-rich" domain between amino acids 315 and 384 for Shc tyrosine phosphorylation and receptor
... eceptor association. COS cell co-transfection studies of IL-2R␤ chain constructs containing point mutations of tyrosine to phenylalanine along with the tyrosine kinase Jak-1 and a hemagglutinin-tagged Shc revealed that the motif surrounding phosphorylated tyrosine 338 within the acidrich domain of the IL-2R␤ is a binding site for Shc. Deletion of this domain has previously been shown to abrogate the ability of IL-2 to activate Ras but does not affect IL-2-dependent mitogenesis in the presence of serum. Proliferation assays of Ba/F3 cells containing IL-2R␤ chain deletion mutants in serum-free medium with or without insulin shows that deletion of the acid-rich domain does not affect IL-2-driven mitogenesis regardless of the culture conditions. This study thus defines the critical domain within the IL-2R␤ chain required to mediate Shc binding and Shc tyrosine phosphorylation and further shows that Shc binding and phosphorylation are not required for IL-2-dependent mitogenesis. Neither serum nor insulin is required to supplement the loss of induction of the Shc adapter or Ras pathways, which therefore suggests a novel mechanism for mitogenic signal transduction mediated by this hematopoietin receptor.